Search Results: "will"

10 September 2017

intrigeri: Can you reproduce this Tails ISO image?

Thanks to a Mozilla Open Source Software award, we have been working on making the Tails ISO images build reproducibly. We have made huge progress: since a few months, ISO images built by Tails core developers and our CI system have always been identical. But we're not done yet and we need your help! Our first call for testing build reproducibility in August uncovered a number of remaining issues. We think that we have fixed them all since, and we now want to find out what other problems may prevent you from building our ISO image reproducibly. Please try to build an ISO image today, and tell us whether it matches ours! Build an ISO These instructions have been tested on Debian Stretch and testing/sid. If you're using another distribution, you may need to adjust them. If you get stuck at some point in the process, see our more detailed build documentation and don't hesitate to contact us: Setup the build environment You need a system that supports KVM, 1 GiB of free memory, and about 20 GiB of disk space.
  1. Install the build dependencies: 
    sudo apt install \
    git \
    rake \
    libvirt-daemon-system \
    dnsmasq-base \
    ebtables \
    qemu-system-x86 \
    qemu-utils \
    vagrant \
    vagrant-libvirt \
    vmdebootstrap && \
sudo systemctl restart libvirtd
  2. Ensure your user is in the relevant groups: 
    for group in kvm libvirt libvirt-qemu ; do
   sudo adduser "$(whoami)" "$group"
done
  3. Logout and log back in to apply the new group memberships.
Build Tails 3.2~alpha2 This should produce a Tails ISO image: 
git clone https://git-tails.immerda.ch/tails && \
cd tails && \
git checkout 3.2-alpha2 && \
git submodule update --init && \
rake build
Send us feedback! No matter how your build attempt turned out we are interested in your feedback. Gather system information To gather the information we need about your system, run the following commands in the terminal where you've run rake build: 
sudo apt install apt-show-versions && \
(
  for f in /etc/issue /proc/cpuinfo
  do
    echo "--- File: $ f  ---"
    cat "$ f "
    echo
  done
  for c in free locale env 'uname -a' '/usr/sbin/libvirtd --version' \
            'qemu-system-x86_64 --version' 'vagrant --version'
  do
    echo "--- Command: $ c  ---"
    eval "$ c "
    echo
  done
  echo '--- APT package versions ---'
  apt-show-versions qemu:amd64 linux-image-amd64:amd64 vagrant \
                    libvirt0:amd64
)   bzip2 > system-info.txt.bz2
Then check that the generated file doesn't contain any sensitive information you do not want to leak: 
bzless system-info.txt.bz2
Next, please follow the instructions below that match your situation! If the build failed Sorry about that. Please help us fix it by opening a ticket: If the build succeeded Compute the SHA-512 checksum of the resulting ISO image: 
sha512sum tails-amd64-3.2~alpha2.iso
Compare your checksum with ours: 
9b4e9e7ee7b2ab6a3fb959d4e4a2db346ae322f9db5409be4d5460156fa1101c23d834a1886c0ce6bef2ed6fe378a7e76f03394c7f651cc4c9a44ba608dda0bc
If the checksums match: success, congrats for reproducing Tails 3.2~alpha2! Please send an email to tails-dev@boum.org (public) or tails@boum.org (private) with the subject "Reproduction of Tails 3.2~alpha2 successful" and system-info.txt.bz2 attached. Thanks in advance! Then you can stop reading here. Else, if the checksums differ: too bad, but really it's good news as the whole point of the exercise is precisely to identify such problems :) Now you are in a great position to help improve the reproducibility of Tails ISO images by following these instructions:
  1. Install diffoscope version 83 or higher and all the packages it recommends. For example, if you're using Debian Stretch: 
    sudo apt remove diffoscope && \
echo 'deb http://ftp.debian.org/debian stretch-backports main' \
    sudo tee /etc/apt/sources.list.d/stretch-backports.list && \
sudo apt update && \
sudo apt -o APT::Install-Recommends="true" \
         install diffoscope/stretch-backports
  2. Download the official Tails 3.2~alpha2 ISO image.
  3. Compare the official Tails 3.2~alpha2 ISO image with yours: 
    diffoscope \
       --text diffoscope.txt \
       --html diffoscope.html \
       --max-report-size 262144000 \
       --max-diff-block-lines 10000 \
       --max-diff-input-lines 10000000 \
       path/to/official/tails-amd64-3.2~alpha2.iso \
       path/to/your/own/tails-amd64-3.2~alpha2.iso
bzip2 diffoscope. txt,html
  4. Send an email to tails-dev@boum.org (public) or tails@boum.org (private) with the subject "Reproduction of Tails 3.2~alpha2 failed", attaching:
    • system-info.txt.bz2;
    • the smallest file among diffoscope.txt.bz2 and diffoscope.html.bz2, except if they are larger than 100 KiB, in which case better upload the file somewhere (e.g. share.riseup.net and share the link in your email.
Thanks a lot! Credits Thanks to Ulrike & anonym who authored a draft on which this blog post is based.

Sylvain Beucler: dot-zed archive file format

TL,DR: I reverse-engineered the .zed encrypted archive format.
Following a clean-room design, I'm providing a description that can be implemented by a third-party.
Interested? :) (reference version at: https://www.beuc.net/zed/) .zed archive file format Introduction Archives with the .zed extension are conceptually similar to an encrypted .zip file. In addition to a specific format, .zed files support multiple users: files are encrypted using the archive master key, which itself is encrypted for each user and/or authentication method (password, RSA key through certificate or PKCS#11 token). Metadata such as filenames is partially encrypted. .zed archives are used as stand-alone or attached to e-mails with the help of a MS Outlook plugin. A variant, which is not covered here, can encrypt/decrypt MS Windows folders on the fly like ecryptfs. In the spirit of academic and independent research this document provides a description of the file format and encryption algorithms for this encrypted file archive. See the conventions section for conventions and acronyms used in this document. Structure overview The .zed file format is composed of several layers. Or as a diagram: 
+----------------------------------------------------------------------------------------------------+
  .zed archive (MS-CBF)                                                                               
                                                                                                      
   stream #1                         stream #2                       stream #3...                     
  +------------------------------+  +---------------------------+  +---------------------------+      
    metadata (MS-OLEPS)               encryption (AES)               encryption (AES)                 
                                      512-bytes chunks               512-bytes chunks                 
    +--------------------------+                                                                      
      obfuscation (static key)        +-----------------------+      +-----------------------+        
      +----------------------+       -  compression (zlib)     -    -  compression (zlib)     -       
       _ctlfile (TLV)                                                                            ...  
      +----------------------+          +---------------+              +---------------+               
    +--------------------------+          file contents                  file contents                
                                                                                                      
    +--------------------------+     -  +---------------+      -    -  +---------------+      -       
      _catalog (TLV)                                                                                  
    +--------------------------+      +-----------------------+      +-----------------------+        
  +------------------------------+  +---------------------------+  +---------------------------+      
+----------------------------------------------------------------------------------------------------+
Encryption schemes Several AES key sizes are supported, such as 128 and 256 bits. The Cipher Block Chaining (CBC) block cipher mode of operation is used to decrypt multiple AES 16-byte blocks, which means an initialisation vector (IV) is stored in clear along with the ciphertext. All filenames and file contents are encrypted using the same encryption mode, key and IV (e.g. if you remove and re-add a file in the archive, the resulting stream will be identical). No cleartext padding is used during encryption; instead, several end-of-stream handlers are available, so the ciphertext has exactly the size of the cleartext (e.g. the size of the compressed file). The following variants were identified in the 'encryption_mode' field. STREAM This is the end-of-stream handler for: This end-of-stream handler is apparently specific to the .zed format, and applied when the cleartext's does not end on a 16-byte boundary ; in this case special processing is performed on the last partial 16-byte block. The encryption and decryption phases are identical: let's assume the last partial block of cleartext (for encryption) or ciphertext (for decryption) was appended after all the complete 16-byte blocks of ciphertext: In either case, if the full ciphertext is less then one AES block (< 16 bytes), then the IV is used instead of the second-to-last block. CTS CTS or CipherText Stealing is the end-of-stream handler for: It matches the CBC-CS3 variant as described in Recommendation for Block Cipher Modes of Operation: Three Variants of Ciphertext Stealing for CBC Mode. Empty cleartext Since empty filenames or metadata are invalid, and since all files are compressed (resulting in a minimum 8-byte zlib cleartext), no empty cleartext was encrypted in the archive. metadata stream It is named 05356861616161716149656b7a6565636e576a33317a7868304e63 (hexadecimal), i.e. the character with code 5 followed by '5haaaaqaIekzeecnWj31zxh0Nc' (ASCII). The format used is OLE Property Set (MS-OLEPS). It introduces 2 property names "_ctlfile" (index 3) and "_catalog" (index 4), and 2 instances of said properties each containing an application-specific VT_BLOB (type 0x0041). _ctlfile: obfuscated global properties and access list This subpart is stored under index 3 ("_ctlfile") of the MS-OLEPS metadata. It consists of: The ciphertext is encrypted with AES-CBC "STREAM" mode using 128-bit static key 37F13CF81C780AF26B6A52654F794AEF (hexadecimal) and the prepended IV so as to obfuscate the access list. The ciphertext is continuous and not split in chunks (unlike files), even when it is larger than 512 bytes. The decrypted text contain properties in a TLV format as described in _ctlfile TLV: Archives may include "mandatory" users that cannot be removed. They are typically used to add an enterprise wide recovery RSA key to all archives. Extreme care must be taken to protect these key, as it can decrypt all past archives generated from within that company. _catalog: file list This subpart is stored under index 4 ("_catalog") of the MS-OLEPS metadata. It contains a series of 'fileprops' TLV structures, one for each file or directory. The file hierarchy can be reconstructed by checking the 'parent_id' field of each file entry. If 'parent_id' is 0 then the file is located at the top-level of the hierarchy, otherwise it's located under the directory with the matching 'file_id'. TLV format This format is a series of fields : Value semantics depend on its Type. It may contain an uint32be integer, a UTF-16LE string, a character sequence, or an inner TLV structure. Unless otherwise noted, TLV structures appear once. Some fields are optional and may not be present at all (e.g. 'archive_createdwith'). Some fields are unique within a structure (e.g. 'files_iv'), other may be repeated within a structure to form a list (e.g. 'fileprops' and 'passworduser'). The following top-level types that have been identified, and detailed in the next sections: Some additional unidentified types may be present. _ctlfile TLV _catalog TLV Decrypting the archive AES key rsauser The user accessing the archive will be authenticated by comparing his/her X509 certificate with the one stored in the 'certificate' field using DER format. The 'files_key_ciphertext' field is then decrypted using the PKCS#1 v1.5 encryption mechanism, with the private key that matches the user certificate. passworduser An intermediary user key, a user IV and an integrity checksum will be derived from the user password, using the deprecated PKCS#12 method as described at rfc7292 appendix B. Note: this is not PKCS#5 (nor PBKDF1/PBKDF2), this is an incompatible method from PKCS#12 that notably does not use HMAC. The 'pkcs12_hashfunc' field defines the underlying hash function. The following values have been identified: PBA - Password-based authentication The user accessing the archive will be authenticated by deriving an 8-byte sequence from his/her password. The parameters for the derivation function are: The derivation is checked against 'pba_checksum'. PBE - Password-based encryption Once the user is identified, 2 new values are derived from the password with different parameters to produce the IV and the key decryption key, with the same hash function: The parameters specific to user key are: The user key needs to be truncated to a length of 'encryption_strength', as specified in bytes in the archive properties. The parameters specific to user IV are: Once the key decryption key and the IV are derived, 'files_key_ciphertext' is decrypted using AES CBC, with PKCS#7 padding. Identifying file streams The name of the MS-CFB stream is derived by shuffling the bytes from the 'file_id' field and then encoding the result as hexadecimal. The reordering is: 
Initial  offset: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Shuffled offset: 3 2 1 0 5 4 7 6 8 9 10 11 12 13 14 15
The 16th byte is usually a NUL byte, hence the stream identifier is a 30-character-long string. Decrypting files The compressed stream is split in chunks of 512 bytes, each of them encrypted separately using AES CBS and the global archive encryption scheme. Decryption uses the global AES key (retrieved using the user credentials), and the global IV (retrieved from the deobfuscated archive metadata). The IV for each chunk is computed by: Each chunk is an independent stream and the decryption process involves end-of-stream handling even if this is not the end of the actual file. This is particularly important for the CTS handler. Note: this is not to be confused with CTR block cipher mode of operation with operates differently and requires a nonce. Decompressing files Compressed streams are zlib stream with default compression options and can be decompressed following the zlib format. Test cases Excluded for brevity, cf. https://www.beuc.net/zed/#test-cases. Conventions and references Feedback Feel free to send comments at beuc@beuc.net. If you have .zed files that you think are not covered by this document, please send them as well (replace sensitive files with other ones). The author's GPG key can be found at 8FF1CB6E8D89059F. Copyright (C) 2017 Sylvain Beucler Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved. This file is offered as-is, without any warranty.

Sylvain Beucler: dot-zed archive file format

TL,DR: I reverse-engineered the .zed encrypted archive format.
Following a clean-room design, I'm providing a description that can be implemented by a third-party.
Interested? :) (reference version at: https://www.beuc.net/zed/) .zed archive file format Introduction Archives with the .zed extension are conceptually similar to an encrypted .zip file. In addition to a specific format, .zed files support multiple users: files are encrypted using the archive master key, which itself is encrypted for each user and/or authentication method (password, RSA key through certificate or PKCS#11 token). Metadata such as filenames is partially encrypted. .zed archives are used as stand-alone or attached to e-mails with the help of a MS Outlook plugin. A variant, which is not covered here, can encrypt/decrypt MS Windows folders on the fly like ecryptfs. In the spirit of academic and independent research this document provides a description of the file format and encryption algorithms for this encrypted file archive. See the conventions section for conventions and acronyms used in this document. Structure overview The .zed file format is composed of several layers. Or as a diagram: 
+----------------------------------------------------------------------------------------------------+
  .zed archive (MS-CBF)                                                                               
                                                                                                      
   stream #1                         stream #2                       stream #3...                     
  +------------------------------+  +---------------------------+  +---------------------------+      
    metadata (MS-OLEPS)               encryption (AES)               encryption (AES)                 
                                      512-bytes chunks               512-bytes chunks                 
    +--------------------------+                                                                      
      obfuscation (static key)        +-----------------------+      +-----------------------+        
      +----------------------+       -  compression (zlib)     -    -  compression (zlib)     -       
       _ctlfile (TLV)                                                                            ...  
      +----------------------+          +---------------+              +---------------+               
    +--------------------------+          file contents                  file contents                
                                                                                                      
    +--------------------------+     -  +---------------+      -    -  +---------------+      -       
      _catalog (TLV)                                                                                  
    +--------------------------+      +-----------------------+      +-----------------------+        
  +------------------------------+  +---------------------------+  +---------------------------+      
+----------------------------------------------------------------------------------------------------+
Encryption schemes Several AES key sizes are supported, such as 128 and 256 bits. The Cipher Block Chaining (CBC) block cipher mode of operation is used to decrypt multiple AES 16-byte blocks, which means an initialisation vector (IV) is stored in clear along with the ciphertext. All filenames and file contents are encrypted using the same encryption mode, key and IV (e.g. if you remove and re-add a file in the archive, the resulting stream will be identical). No cleartext padding is used during encryption; instead, several end-of-stream handlers are available, so the ciphertext has exactly the size of the cleartext (e.g. the size of the compressed file). The following variants were identified in the 'encryption_mode' field. STREAM This is the end-of-stream handler for: This end-of-stream handler is apparently specific to the .zed format, and applied when the cleartext's does not end on a 16-byte boundary ; in this case special processing is performed on the last partial 16-byte block. The encryption and decryption phases are identical: let's assume the last partial block of cleartext (for encryption) or ciphertext (for decryption) was appended after all the complete 16-byte blocks of ciphertext: In either case, if the full ciphertext is less then one AES block (< 16 bytes), then the IV is used instead of the second-to-last block. CTS CTS or CipherText Stealing is the end-of-stream handler for: It matches the CBC-CS3 variant as described in Recommendation for Block Cipher Modes of Operation: Three Variants of Ciphertext Stealing for CBC Mode. Empty cleartext Since empty filenames or metadata are invalid, and since all files are compressed (resulting in a minimum 8-byte zlib cleartext), no empty cleartext was encrypted in the archive. metadata stream It is named 05356861616161716149656b7a6565636e576a33317a7868304e63 (hexadecimal), i.e. the character with code 5 followed by '5haaaaqaIekzeecnWj31zxh0Nc' (ASCII). The format used is OLE Property Set (MS-OLEPS). It introduces 2 property names "_ctlfile" (index 3) and "_catalog" (index 4), and 2 instances of said properties each containing an application-specific VT_BLOB (type 0x0041). _ctlfile: obfuscated global properties and access list This subpart is stored under index 3 ("_ctlfile") of the MS-OLEPS metadata. It consists of: The ciphertext is encrypted with AES-CBC "STREAM" mode using 128-bit static key 37F13CF81C780AF26B6A52654F794AEF (hexadecimal) and the prepended IV so as to obfuscate the access list. The ciphertext is continuous and not split in chunks (unlike files), even when it is larger than 512 bytes. The decrypted text contain properties in a TLV format as described in _ctlfile TLV: Archives may include "mandatory" users that cannot be removed. They are typically used to add an enterprise wide recovery RSA key to all archives. Extreme care must be taken to protect these key, as it can decrypt all past archives generated from within that company. _catalog: file list This subpart is stored under index 4 ("_catalog") of the MS-OLEPS metadata. It contains a series of 'fileprops' TLV structures, one for each file or directory. The file hierarchy can be reconstructed by checking the 'parent_id' field of each file entry. If 'parent_id' is 0 then the file is located at the top-level of the hierarchy, otherwise it's located under the directory with the matching 'file_id'. TLV format This format is a series of fields : Value semantics depend on its Type. It may contain an uint32be integer, a UTF-16LE string, a character sequence, or an inner TLV structure. Unless otherwise noted, TLV structures appear once. Some fields are optional and may not be present at all (e.g. 'archive_createdwith'). Some fields are unique within a structure (e.g. 'files_iv'), other may be repeated within a structure to form a list (e.g. 'fileprops' and 'passworduser'). The following top-level types that have been identified, and detailed in the next sections: Some additional unidentified types may be present. _ctlfile TLV _catalog TLV Decrypting the archive AES key rsauser The user accessing the archive will be authenticated by comparing his/her X509 certificate with the one stored in the 'certificate' field using DER format. The 'files_key_ciphertext' field is then decrypted using the PKCS#1 v1.5 encryption mechanism, with the private key that matches the user certificate. passworduser An intermediary user key, a user IV and an integrity checksum will be derived from the user password, using the deprecated PKCS#12 method as described at rfc7292 appendix B. Note: this is not PKCS#5 (nor PBKDF1/PBKDF2), this is an incompatible method from PKCS#12 that notably does not use HMAC. The 'pkcs12_hashfunc' field defines the underlying hash function. The following values have been identified: PBA - Password-based authentication The user accessing the archive will be authenticated by deriving an 8-byte sequence from his/her password. The parameters for the derivation function are: The derivation is checked against 'pba_checksum'. PBE - Password-based encryption Once the user is identified, 2 new values are derived from the password with different parameters to produce the IV and the key decryption key, with the same hash function: The parameters specific to user key are: The user key needs to be truncated to a length of 'encryption_strength', as specified in bytes in the archive properties. The parameters specific to user IV are: Once the key decryption key and the IV are derived, 'files_key_ciphertext' is decrypted using AES CBC, with PKCS#7 padding. Identifying file streams The name of the MS-CFB stream is derived by shuffling the bytes from the 'file_id' field and then encoding the result as hexadecimal. The reordering is: 
Initial  offset: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Shuffled offset: 3 2 1 0 5 4 7 6 8 9 10 11 12 13 14 15
The 16th byte is usually a NUL byte, hence the stream identifier is a 30-character-long string. Decrypting files The compressed stream is split in chunks of 512 bytes, each of them encrypted separately using AES CBS and the global archive encryption scheme. Decryption uses the global AES key (retrieved using the user credentials), and the global IV (retrieved from the deobfuscated archive metadata). The IV for each chunk is computed by: Each chunk is an independent stream and the decryption process involves end-of-stream handling even if this is not the end of the actual file. This is particularly important for the CTS handler. Note: this is not to be confused with CTR block cipher mode of operation with operates differently and requires a nonce. Decompressing files Compressed streams are zlib stream with default compression options and can be decompressed following the zlib format. Test cases Excluded for brevity, cf. https://www.beuc.net/zed/#test-cases. Conventions and references Feedback Feel free to send comments at beuc@beuc.net. If you have .zed files that you think are not covered by this document, please send them as well (replace sensitive files with other ones). The author's GPG key can be found at 8FF1CB6E8D89059F. Copyright (C) 2017 Sylvain Beucler Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved. This file is offered as-is, without any warranty.

Joachim Breitner: Less parentheses

Yesterday, at the Haskell Implementers Workshop 2017 in Oxford, I gave a lightning talk titled syntactic musings , where I presented three possibly useful syntactic features that one might want to add to a language like Haskell. The talked caused quite some heated discussions, and since the Internet likes heated discussion, I will happily share these ideas with you

Context aka. Sections This is probably the most relevant of the three proposals. Consider a bunch of related functions, say analyseExpr and analyseAlt, like these: 
analyseExpr :: Expr -> Expr
analyseExpr (Var v) = change v
analyseExpr (App e1 e2) =
  App (analyseExpr e1) (analyseExpr e2)
analyseExpr (Lam v e) = Lam v (analyseExpr flag e)
analyseExpr (Case scrut alts) =
  Case (analyseExpr scrut) (analyseAlt <$> alts)
analyseAlt :: Alt -> Alt
analyseAlt (dc, pats, e) = (dc, pats, analyseExpr e)
You have written them, but now you notice that you need to make them configurable, e.g. to do different things in the Var case. You thus add a parameter to all these functions, and hence an argument to every call: 
type Flag = Bool
analyseExpr :: Flag -> Expr -> Expr
analyseExpr flag (Var v) = if flag then change1 v else change2 v
analyseExpr flag (App e1 e2) =
  App (analyseExpr flag e1) (analyseExpr flag e2)
analyseExpr flag (Lam v e) = Lam v (analyseExpr (not flag) e)
analyseExpr flag (Case scrut alts) =
  Case (analyseExpr flag scrut) (analyseAlt flag <$> alts)
analyseAlt :: Flag -> Alt -> Alt
analyseAlt flag (dc, pats, e) = (dc, pats, analyseExpr flag e)
I find this code problematic. The intention was: flag is a parameter that an external caller can use to change the behaviour of this code, but when reading and reasoning about this code, flag should be considered constant. But this intention is neither easily visible nor enforced. And in fact, in the above code, flag does change , as analyseExpr passes something else in the Lam case. The idiom is indistinguishable from the environment idiom, where a locally changing environment (such as variables in scope ) is passed around. So we are facing exactly the same problem as when reasoning about a loop in an imperative program with mutable variables. And we (pure functional programmers) should know better: We cherish immutability! We want to bind our variables once and have them scope over everything we need to scope over! The solution I d like to see in Haskell is common in other languages (Gallina, Idris, Agda, Isar), and this is what it would look like here: 
type Flag = Bool
section (flag :: Flag) where
  analyseExpr :: Expr -> Expr
  analyseExpr (Var v) = if flag then change1 v else change2v 
  analyseExpr (App e1 e2) =
    App (analyseExpr e1) (analyseExpr e2)
  analyseExpr (Lam v e) = Lam v (analyseExpr e)
  analyseExpr (Case scrut alts) =
    Case (analyseExpr scrut) (analyseAlt <$> alts)
  analyseAlt :: Alt -> Alt
  analyseAlt (dc, pats, e) = (dc, pats, analyseExpr e)
Now the intention is clear: Within a clearly marked block, flag is fixed and when reasoning about this code I do not have to worry that it might change. Either all variables will be passed to change1, or all to change2. An important distinction! Therefore, inside the section, the type of analyseExpr does not mention Flag, whereas outside its type is Flag -> Expr -> Expr. This is a bit unusual, but not completely: You see precisely the same effect in a class declaration, where the type signature of the methods do not mention the class constraint, but outside the declaration they do. Note that idioms like implicit parameters or the Reader monad do not give the guarantee that the parameter is (locally) constant. More details can be found in the GHC proposal that I prepared, and I invite you to raise concern or voice support there. Curiously, this problem must have bothered me for longer than I remember: I discovered that seven years ago, I wrote a Template Haskell based implementation of this idea in the seal-module package!

Less parentheses 1: Bulleted argument lists The next two proposals are all about removing parentheses. I believe that Haskell s tendency to express complex code with no or few parentheses is one of its big strengths, as it makes it easier to visualy parse programs. A common idiom is to use the $ operator to separate a function from a complex argument without parentheses, but it does not help when there are multiple complex arguments. For that case I propose to steal an idea from the surprisingly successful markup language markdown, and use bulleted lists to indicate multiple arguments: 
foo :: Baz
foo = bracket
          some complicated code
          that is evaluated first
          other complicated code for later
          even more complicated code
I find this very easy to visually parse and navigate. It is actually possible to do this now, if one defines ( ) = id with infixl 0 . A dedicated syntax extension (-XArgumentBullets) is preferable:
  • It only really adds readability if the bullets are nicely vertically aligned, which the compiler should enforce.
  • I would like to use $ inside these complex arguments, and multiple operators of precedence 0 do not mix. (infixl -1 would help).
  • It should be possible to nest these, and distinguish different nesting levers based on their indentation.

Less parentheses 1: Whitespace precedence The final proposal is the most daring. I am convinced that it improves readability and should be considered when creating a new language. As for Haskell, I am at the moment not proposing this as a language extension (but could be convinced to do so if there is enough positive feedback). Consider this definition of append: 
(++) :: [a] -> [a] -> [a]
[]     ++ ys = ys
(x:xs) ++ ys = x : (xs++ys)
Imagine you were explaining the last line to someone orally. How would you speak it? One common way to do so is to not read the parentheses out aloud, but rather speak parenthesised expression more quickly and add pauses otherwise. We can do the same in syntax! 
(++) :: [a] -> [a] -> [a]
[]   ++ ys = ys
x:xs ++ ys = x : xs++ys
The rule is simple: A sequence of tokens without any space is implicitly parenthesised. The reaction I got in Oxford was horror and disgust. And that is understandable we are very used to ignore spacing when parsing expressions (unless it is indentation, of course. Then we are no longer horrified, as our non-Haskell colleagues are when they see our code). But I am convinced that once you let the rule sink in, you will have no problem parsing such code with ease, and soon even with greater ease than the parenthesised version. It is a very natural thing to look at the general structure, identify compact chunks of characters , mentally group them, and then go and separately parse the internals of the chunks and how the chunks relate to each other. More natural than first scanning everything for ( and ), matching them up, building a mental tree, and then digging deeper. Incidentally, there was a non-programmer present during my presentation, and while she did not openly contradict the dismissive groan of the audience, I later learned that she found this variant quite obvious to understand and more easily to read than the parenthesised code. Some FAQs about this:
  • What about an operator with space on one side but not on the other? I d simply forbid that, and hence enforce readable code.
  • Do operator sections still require parenthesis? Yes, I d say so.
  • Does this overrule operator precedence? Yes! a * b+c == a * (b+c).
  • What is a token? Good question, and I am not not decided. In particular: Is a parenthesised expression a single token? If so, then (Succ a)+b * c parses as ((Succ a)+b) * c, otherwise it should probably simply be illegal.
  • Can we extend this so that one space binds tighter than two spaces, and so on? Yes we can, but really, we should not.
  • This is incompatible with Agda s syntax! Indeed it is, and I really like Agda s mixfix syntax. Can t have everything.
  • Has this been done before? I have not seen it in any language, but Lewis Wall has blogged this idea before.
Well, let me know what you think!

9 September 2017

Fran ois Marier: TLS Authentication on Freenode and OFTC

In order to easily authenticate with IRC networks such as OFTC and Freenode, it is possible to use client TLS certificates (also known as SSL certificates). In fact, it turns out that it's very easy to setup both on irssi and on znc.

Generate your TLS certificate On a machine with good entropy, run the following command to create a keypair that will last for 10 years: 
openssl req -nodes -newkey rsa:2048 -keyout user.pem -x509 -days 3650 -out user.pem -subj "/CN=<your nick>"
Then extract your key fingerprint using this command: 
openssl x509 -sha1 -noout -fingerprint -in user.pem   sed -e 's/^.*=//;s/://g'

Share your fingerprints with NickServ On each IRC network, do this: 
/msg NickServ IDENTIFY Password1!
/msg NickServ CERT ADD <your fingerprint>
in order to add your fingerprint to the access control list.

Configure ZNC To configure znc, start by putting the key in the right place: 
cp user.pem ~/.znc/users/<your nick>/networks/oftc/moddata/cert/
and then enable the built-in cert plugin for each network in ~/.znc/configs/znc.conf: 
<Network oftc>
    ...
            LoadModule = cert
    ...
</Network>
    <Network freenode>
    ...
            LoadModule = cert
    ...
</Network>

Configure irssi For irssi, do the same thing but put the cert in ~/.irssi/user.pem and then change the OFTC entry in ~/.irssi/config to look like this: 
 
  address = "irc.oftc.net";
  chatnet = "OFTC";
  port = "6697";
  use_tls = "yes";
  tls_cert = "~/.irssi/user.pem";
  tls_verify = "yes";
  autoconnect = "yes";
and the Freenode one to look like this: 
 
  address = "chat.freenode.net";
  chatnet = "Freenode";
  port = "7000";
  use_tls = "yes";
  tls_cert = "~/.irssi/user.pem";
  tls_verify = "yes";
  autoconnect = "yes";
That's it. That's all you need to replace password authentication with a much stronger alternative.

8 September 2017

Sven Hoexter: munin with TLS

Primarily a note for my future self so I don't have to find out what I did in the past once more. If you're running some smaller systems scattered around the internet, without connecting them with a VPN, you might want your munin master and nodes to communicate with TLS and validate certificates. If you remember what to do it's a rather simple and straight forward process. To manage the PKI I'll utilize the well known easyrsa script collection. For this special purpose CA I'll go with a flat layout. So it's one root certificate issuing all server and client certificates directly. Some very basic docs can be also found in the munin wiki. master setup For your '/etc/munin/munin.conf': 
tls paranoid
tls_verify_certificate yes
tls_private_key /etc/munin/master.key
tls_certificate /etc/munin/master.crt
tls_ca_certificate /etc/munin/ca.crt
tls_verify_depth 1
A node entry with TLS will look like this: 
[node1.stormbind.net]
    address [2001:db8::]
    use_node_name yes
Important points here: For easy-rsa the following command invocations are relevant: 
./easyrsa init-pki
./easyrsa build-ca
./easrsa gen-req master
./easyrsa sign-req client master
./easyrsa set-rsa-pass master nopass
node setup For your '/etc/munin/munin-node.conf': 
tls paranoid
tls_verify_certificate yes
tls_private_key /etc/munin/node1.key
tls_certificate /etc/munin/node1.crt
tls_ca_certificate /etc/munin/ca.crt
tls_verify_depth 1
For easy-rsa the following command invocations are relevant: 
./easyrsa gen-req node1
./easyrsa sign-req server node1
./easyrsa set-rsa-pass node1 nopass
Important points here:

7 September 2017

Lior Kaplan: FOSScamp Syros 2017 day 3

The 3rd day should have started with a Debian sprint and then a LibreOffice one, taking advantage I m still attending, as that s my last day. But plans don t always work out and we started 2 hours later. When everybody arrive we got everyone together for a short daily meeting (scrum style). The people were divided to 3 teams for translating: Debian Installer, LibreOffice and Gnome. For each team we did a short list of what left and with what to start. And in the end how does what so there will be no toe stepping. I was really proud with this and felt it was time well spent. The current translation percentage for Albanian in LibreOffice is 60%. So my recommendation to the team is translate master only and do not touch the help translation. My plans ahead would be to improve the translation as much as possible for LibreOffice 6.0 and near the branching point (Set to November 20th by the release schedule) decide if it s doable for the 6.0 life time or to set the goal at 6.1. In the 2nd case, we might try to backport translation back to 6.0. For the translation itself, I ve mentioned to the team about KeyID language pack and referred them to the nightly builds. These tools should help with keeping the translation quality high. For the Debian team, after deciding who works on what, I ve asked Silva to do review for the others, as doing it myself started to take more and more of my time. It s also good that the reviewer know the target language and not like me, can catch more the syntax only mistakes. Another point, as she s available more easily to the team while I m leaving soon, so I hope this role of reviewer will stay as part of the team. With the time left I mostly worked on my own tasks, which were packaging the Albanian dictionary, resulting in https://packages.debian.org/sid/myspell-sq and making sure the dictionary is also part of LibreOffice resulting in https://gerrit.libreoffice.org/#/c/41906/ . When it is accepted, I want to upload it to the LibreOffice repository so all users can download and use the dictionary. During the voyage home (ferry, bus, plain and train), I mailed Sergio Durigan Junior, my NM applicant, with a set of questions. My first action as an AM (: Overall FOSScamp results for Albanian translation were very close to the goal I set (100%): That s the result of work by Silva Arapi, Eva Vranici, Redon Skikuli, Anisa Kuci and Nafie Shehu.
Filed under: Debian GNU/Linux, i18n & l10n, LibreOffice

Thomas Lange: My recent FAI activities

During DebConf 17 in Montr al I had a FAI demo session (video), where I showed how to create a customized installation CD and how to create a diskimage using the same configuration. This diskimage is ready for use with a VM software or can be booted inside a cloud environment. During the last weeks I was working on FAI 5.4 which will be released in a few weeks. I you want to test it use 
deb https://fai-project.org/download beta-testing koeln
in your sources.list file. The most important new feature will be the cross architecture support. I managed to create an ARM64 diskimage on a x86 host and boot this inside Qemu. Currently I learn how to flash images onto my new Hikey960 board for booting my own Debian images on real hardware. The embedded world is still new for me and very different in respect to the boot process. At DebConf, I also worked on debootstrap. I produced a set of patches which can speedup debootstrap by a factor of 2. See #871835 for details. FAI debootstrap ARM

Reproducible builds folks: Reproducible Builds: Weekly report #123

Here's what happened in the Reproducible Builds effort between Sunday August 27 and Saturday September 2 2017: Talks and presentations Holger Levsen talked about our progress and our still-far goals at BornHack 2017 (Video). Toolchain development and fixes The Debian FTP archive will now reject changelogs where different entries have the same timestamps. UDD now uses reproducible-tracker.json (~25MB) which ignores our tests for Debian unstable, instead of our full set of results in reproducible.json. Our tests for Debian unstable uses a stricter definition of "reproducible" than what was recently added to Debian policy, and these stricter tests are currently more unreliable. Packages reviewed and fixed, and bugs filed Patches sent upstream: Debian bugs filed: Debian packages NMU-uploaded: Reviews of unreproducible packages 25 package reviews have been added, 50 have been updated and 86 have been removed in this week, adding to our knowledge about identified issues. Weekly QA work During our reproducibility testing, FTBFS bugs have been detected and reported by: diffoscope development Version 86 was uploaded to unstable by Mattia Rizzolo. It included previous weeks' contributions from: reprotest development Development continued in git with contributions from: Misc. This week's edition was written by Ximin Luo, Chris Lamb, Bernhard M. Wiedemann and Holger Levsen & reviewed by a bunch of Reproducible Builds folks on IRC & the mailing lists.

John Goerzen: Switching to xmonad + Gnome and ditching a Mac

I have been using XFCE with xmonad for years now. I m not sure exactly how many, but at least 6 years, if not closer to 10. Today I threw in the towel and switched to Gnome. More recently, at a new job, I was given a Macbook Pro. I wasn t entirely sure what to think of this, but I thought I d give it a try. I found MacOS to be extremely frustrating and confining. It had no real support for a tiling window manager, and although projects like amethyst tried to approximate what xmonad can do on Linux, they were just too limited by the platform and were clunky. Moreover, the entire UI was surprisingly sluggish; maybe that was an induced effect from animations, but I don t think that explains it. A Debisn stretch install, even on inferior hardware, was snappy in a way that MacOS never was. So I have requested to swap for a laptop that will run Debian. The strange use of Command instead of Control for things, combined with the overall lack of configurability of keybindings, meant that I was going to always be fighting muscle memory moving from one platform to another. Not only that, but being back in the world of a Free Software OS means a lot. Now then, back to xmonad and XFCE situation. XFCE once worked very well with xmonad. Over the years, this got more challenging. Around the jessie (XFCE 4.10) time, I had to be very careful about when I would let it save my session, because it would easily break. With stretch, I had to write custom scripts because the panel wouldn t show up properly, and even some application icons would be invisible, if things were started in a certain order. This took much trial and error and was still cumbersome. Gnome 3, with its tightly-coupled Gnome Shell, has never been compatible with other window managers at least not directly. A person could have always used MATE with xmonad but a lot of people that run XFCE tend to have some Gnome 3 apps (for instance, evince) anyhow. Cinnamon also wouldn t work with xmonad, because it is simply another tightly-coupled shell instead of Gnome Shell. And then today I discovered gnome-flashback. gnome-flashback is a Gnome 3 environment that uses the traditional X approach with a separate window manager (metacity of yore by default). Sweet. It turns out that Debian s xmonad has built-in support for it. If you know the secret: apt-get install gnome-session-flashback (OK, it s not so secret; it s even in xmonad s README.Debian these days) Install that, plus gnome and gdm3 and things are nice. Configure xmonad with GNOME support and poof goodness right out of the box, selectable from the gdm sessions list. I still have some gripes about Gnome s configurability (or lack thereof). But I ve got to say: This environment is the first one I ve ever used that got external display switching very nearly right without any configuration, and I include MacOS in that. Plug in an external display, and poof it s configured and set up. You can hit a toggle key (Windows+P by default) to change the configurations, or use the Display section in gnome-control-center. Unplug it, and it instantly reconfigures itself to put everything back on the laptop screen. Yessss! I used to have scripts to do this in the wheezy/jessie days. XFCE in stretch had numerous annoying failures in this area which rendered the internal display completely dark until the next reboot very frustrating. With Gnome, it just works. And, even if you have suspend on lid closed turned on, if the system is powered up and hooked up to an external display, it will keep running even if the lid is closed, figuring you must be using it on the external screen. Another thing the Mac wouldn t do well. All in all, some pretty good stuff here. I continue to be impressed by stretch. It is darn impressive to put this OS on generic hardware and have it outshine the closed-ecosystem Mac!

5 September 2017

Kees Cook: security things in Linux v4.13

Previously: v4.12. Here s a short summary of some of interesting security things in Sunday s v4.13 release of the Linux kernel: security documentation ReSTification
The kernel has been switching to formatting documentation with ReST, and I noticed that none of the Documentation/security/ tree had been converted yet. I took the opportunity to take a few passes at formatting the existing documentation and, at Jon Corbet s recommendation, split it up between end-user documentation (which is mainly how to use LSMs) and developer documentation (which is mainly how to use various internal APIs). A bunch of these docs need some updating, so maybe with the improved visibility, they ll get some extra attention. CONFIG_REFCOUNT_FULL
Since Peter Zijlstra implemented the refcount_t API in v4.11, Elena Reshetova (with Hans Liljestrand and David Windsor) has been systematically replacing atomic_t reference counters with refcount_t. As of v4.13, there are now close to 125 conversions with many more to come. However, there were concerns over the performance characteristics of the refcount_t implementation from the maintainers of the net, mm, and block subsystems. In order to assuage these concerns and help the conversion progress continue, I added an unchecked refcount_t implementation (identical to the earlier atomic_t implementation) as the default, with the fully checked implementation now available under CONFIG_REFCOUNT_FULL. The plan is that for v4.14 and beyond, the kernel can grow per-architecture implementations of refcount_t that have performance characteristics on par with atomic_t (as done in grsecurity s PAX_REFCOUNT). CONFIG_FORTIFY_SOURCE
Daniel Micay created a version of glibc s FORTIFY_SOURCE compile-time and run-time protection for finding overflows in the common string (e.g. strcpy, strcmp) and memory (e.g. memcpy, memcmp) functions. The idea is that since the compiler already knows the size of many of the buffer arguments used by these functions, it can already build in checks for buffer overflows. When all the sizes are known at compile time, this can actually allow the compiler to fail the build instead of continuing with a proven overflow. When only some of the sizes are known (e.g. destination size is known at compile-time, but source size is only known at run-time) run-time checks are added to catch any cases where an overflow might happen. Adding this found several places where minor leaks were happening, and Daniel and I chased down fixes for them. One interesting note about this protection is that is only examines the size of the whole object for its size (via __builtin_object_size(..., 0)). If you have a string within a structure, CONFIG_FORTIFY_SOURCE as currently implemented will make sure only that you can t copy beyond the structure (but therefore, you can still overflow the string within the structure). The next step in enhancing this protection is to switch from 0 (above) to 1, which will use the closest surrounding subobject (e.g. the string). However, there are a lot of cases where the kernel intentionally copies across multiple structure fields, which means more fixes before this higher level can be enabled. NULL-prefixed stack canary
Rik van Riel and Daniel Micay changed how the stack canary is defined on 64-bit systems to always make sure that the leading byte is zero. This provides a deterministic defense against overflowing string functions (e.g. strcpy), since they will either stop an overflowing read at the NULL byte, or be unable to write a NULL byte, thereby always triggering the canary check. This does reduce the entropy from 64 bits to 56 bits for overflow cases where NULL bytes can be written (e.g. memcpy), but the trade-off is worth it. (Besdies, x86_64 s canary was 32-bits until recently.) IPC refactoring
Partially in support of allowing IPC structure layouts to be randomized by the randstruct plugin, Manfred Spraul and I reorganized the internal layout of how IPC is tracked in the kernel. The resulting allocations are smaller and much easier to deal with, even if I initially missed a few needed container_of() uses. randstruct gcc plugin
I ported grsecurity s clever randstruct gcc plugin to upstream. This plugin allows structure layouts to be randomized on a per-build basis, providing a probabilistic defense against attacks that need to know the location of sensitive structure fields in kernel memory (which is most attacks). By moving things around in this fashion, attackers need to perform much more work to determine the resulting layout before they can mount a reliable attack. Unfortunately, due to the timing of the development cycle, only the manual mode of randstruct landed in upstream (i.e. marking structures with __randomize_layout). v4.14 will also have the automatic mode enabled, which randomizes all structures that contain only function pointers. A large number of fixes to support randstruct have been landing from v4.10 through v4.13, most of which were already identified and fixed by grsecurity, but many were novel, either in newly added drivers, as whitelisted cross-structure casts, refactorings (like IPC noted above), or in a corner case on ARM found during upstream testing. lower ELF_ET_DYN_BASE
One of the issues identified from the Stack Clash set of vulnerabilities was that it was possible to collide stack memory with the highest portion of a PIE program s text memory since the default ELF_ET_DYN_BASE (the lowest possible random position of a PIE executable in memory) was already so high in the memory layout (specifically, 2/3rds of the way through the address space). Fixing this required teaching the ELF loader how to load interpreters as shared objects in the mmap region instead of as a PIE executable (to avoid potentially colliding with the binary it was loading). As a result, the PIE default could be moved down to ET_EXEC (0x400000) on 32-bit, entirely avoiding the subset of Stack Clash attacks. 64-bit could be moved to just above the 32-bit address space (0x100000000), leaving the entire 32-bit region open for VMs to do 32-bit addressing, but late in the cycle it was discovered that Address Sanitizer couldn t handle it moving. With most of the Stack Clash risk only applicable to 32-bit, fixing 64-bit has been deferred until there is a way to teach Address Sanitizer how to load itself as a shared object instead of as a PIE binary. early device randomness
I noticed that early device randomness wasn t actually getting added to the kernel entropy pools, so I fixed that to improve the effectiveness of the latent_entropy gcc plugin. That s it for now; please let me know if I missed anything. As a side note, I was rather alarmed to discover that due to all my trivial ReSTification formatting, and tiny FORTIFY_SOURCE and randstruct fixes, I made it into the most active 4.13 developers list (by patch count) at LWN with 76 patches: a whopping 0.6% of the cycle s patches. ;) Anyway, the v4.14 merge window is open!

2017, Kees Cook. This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 License.
Creative Commons License

Chris Lamb: Ask the dumb questions

In the same way it vital to ask the "smart questions", it is equally important to ask the dumb ones. Whilst your milieu might be say comparing and contrasting the finer details of commission structures between bond brokers, if you aren't quite sure of the topic learn to be bold and confident enough to boldly ask: I'm sorry, but what actually is a bond? Don't consider this to be an all-or-nothing affair. After all, you might have at least some idea about what a bond is. Rather, adjust your tolerance to also ask for clarification when you are merely slightly unsure or merely slightly uncertain about a concept, term or reference.
So why do this? Most obviously, you are learning something and expanding your knowledge about the world, but a clarification can avoid problems later if you were mistaken in your assumptions. Not only that, asking "can you explain that?" or admitting "I don't follow " is not only being honest with yourself, the vulnerability you show when admitting one's ignorance opens yourself to others leading to closer friendships and working relationships. We clearly have a tendency to want to come across as knowledgable or perhaps more honestly we don't want to appear dumb or uninformed as it will bruise our ego. But the precise opposite is true: nodding and muddling your way through conversations you only partly understand is unlikely to cultivate true feelings of self-respect and a healthy self-esteem. Since adopting this approach I have found I've rarely derailed the conversation. In fact, speaking up not only encourages and flatters others that you care about their subject, it has invariably lead to related matters which are not only more inclusive but actually novel and interesting to all present.
So push through the voice in your head and be that elephant in the room. After all, you might not the only person thinking it. If it helps, try reframing it to yourself as helping others You'll be finding it effortless soon enough. Indeed, asking the dumb question is actually a positive feedback loop where each question you pose helps you make others in the future. Excellence is not an act, but a habit.

4 September 2017

Dominique Dumont: cme: some read-write backend features are being deprecated

Hello Config::Model and cme read and write configuration data with a set of backend classes, like Config::Model::Backend::IniFile. These classes are managed by Config::Model::BackendMgr. Well, that s the simplified view. Actually, the backend manager can handle several different backends to read and write data: read backends are tried until one of them succeeds to read configuration data. And write backend cen be different from the read backend, thus offering the possibility to migrare from one format to another. This feature came at the beginning of the project, back in 2005. This felt like a good idea to let user migrate from one data format to another. More than 10 years later, this feature has never been used and is handled by a bunch of messy code that hampers further evolution of the backend classes. So, without further ado, I m going to deprecate the following features in order to simplify the backend manager: Unless someone objects, actual removal of these feature will be done in the next few months, after a quite short deprecation period. All the best
Tagged: cme, config-model, Config::Model, configuration

Alessio Treglia: MeteoSurf: a free App for the Mediterranean Sea

meteosurf

MeteoSurf is a free multi-source weather forecasting App designed to provide wind and wave conditions of the Mediterranean Sea. It is an application for smartphones and tablets, built as a Progressive Web App able to supply detailed and updated maps and data showing heights of sea waves (and other information) in the Central Mediterranean. It is mainly targeted for surfers and wind-surfers but anyone who needs to know the sea conditions will take advantage from this app.

Data can be displayed as animated graphical maps, or as detailed table data. The maps refer to the whole Mediterranean Sea, while the table data is able to provide specific information for any of the major surf spots in the Med.

As of current version, MeteoSurf shows data collecting them from 3 different forecasting systems Read More [by Fabio Marzocca]

Lior Kaplan: FOSScamp Syros 2017 day 2

The morning stated by taking the bus to Kini beach. After some to enjoy the water (which were still cold in the morning), we sat for talking about the local Debian community and how can we help it grow. The main topic was localization (l10n), but we soon started to check other options. I reminded them that l10n isn t only translation and we also talked about dictionaries for spell checking, fonts and local software which might be relevant (e.g. hdate for the Jewish/Hebrew calendar or Jcal for the Jalali calendar). For example it seems that regular Latin fonts are missing two Albanian characters. We also talked about how to use Open Labs to better work together with two hats member of the local FOSS community and also as members of various open source projects (not forgetting open content / data ones projects as well). So people can cooperate both on the local level, the international level or to mix (using the other s project international resources). In short: connections, connections, connections. Another aspect I tried to push the guys toward is cooperating with local companies about open source, whether it s the local market, the municipal and general government. Such cooperation can take many forms, sponsoring events / giving resources (computers, physical space or employee s time) and of course creating more jobs for open source people, which in turn will support more people doing open source for longer period. One of the guys thought benefit the local community will benefit from a mirror server, but that also requires to see the network topology of Albania to make sure it makes sense to invest in one (resources and effort). We continued to how it would be best to contribute to open source, mostly that Debian, although great isn t always the best target, and they should always try to work with the relevant upstream. It s better to translate gnome upstream then sending the Debian maintainer the translation to be included in the package. That shortcut can work if there s something urgent like a really problematic typo or something what unless done before the release would require a long long wait (e.g. the next Debian release). I gave an example that for important RTL bugs in LibreOffice I ve asked Rene Engelhard to include the patch instead of waiting for the next release and its inclusion in Debian. When I started the conversation I mentioned that we have 33% females out of the 12 participants. And that s considered good comparing to other computer/technical events, especially open source. To my surprise the guys told me that in the Open Labs hackerspace the situation is the opposite, they have more female members than male (14 female to 12 male). Also in their last OSCAL event they had 220 women and 100 men. I think there s grounds to learn what happens there, as the gals do something damn right over there. Maybe Outreachy rules for Albania should be different (: Later that day I did another session with Redon Skikuli to be more practical, so I started to search on an Albanian dictionary for spell checking, found an old one and asked Redon to check the current status with the guy. And also check info about such technical stuff with Social Sciences and Albanological Section of the Academy of Sciences of Albania, who is officially the regulator for Albanian. In parallel I started to check how to include the dictionary in LibreOffice, and asked Rene Engelhard to enable Albanian language pack in Debian (as upstream already provide one). Checking the dictionaries I ve took the opportunity to update the Hebrew. It took me a little longer as I needed to get rust off my LibreOffice repositories (dictionaries is a different repository) and also the gerrit setup. But in the end: https://gerrit.libreoffice.org/#/c/41864/ With the talks toady and the starting to combine both Debian and LibreOffice work today (although much of it was talking) I felt like I m the right person on the right place. I m happy to be here and contribute to two projects in parallel (:
Filed under: Debian GNU/Linux, i18n & l10n, LibreOffice

Daniel Pocock: Spyware Dolls and Intel's vPro

Back in February, it was reported that a "smart" doll with wireless capabilities could be used to remotely spy on children and was banned for breaching German laws on surveillance devices disguised as another object. Would you trust this doll? For a number of years now there has been growing concern that the management technologies in recent Intel CPUs (ME, AMT and vPro) also conceal capabilities for spying, either due to design flaws (no software is perfect) or backdoors deliberately installed for US spy agencies, as revealed by Edward Snowden. In a 2014 interview, Intel's CEO offered to answer any question, except this one. The LibreBoot project provides a more comprehensive and technical analysis of the issue, summarized in the statement "the libreboot project recommends avoiding all modern Intel hardware. If you have an Intel based system affected by the problems described below, then you should get rid of it as soon as possible" - eerily similar to the official advice German authorities are giving to victims of Cayla the doll. All those amateur psychiatrists suggesting LibreBoot developers suffer from symptoms of schizophrenia have had to shut their mouths since May when Intel confirmed a design flaw (or NSA backdoor) in every modern CPU had become known to hackers. Bill Gates famously started out with the mission to put a computer on every desk and in every home. With more than 80% of new laptops based on an Intel CPU with these hidden capabilities, can you imagine the NSA would not have wanted to come along for the ride? Four questions everybody should be asking
  • If existing laws can already be applied to Cayla the doll, why haven't they been used to alert owners of devices containing Intel's vPro?
  • Are exploits of these backdoors (either Cayla or vPro) only feasible on a targeted basis, or do the intelligence agencies harvest data from these backdoors on a wholesale level, keeping a mirror image of every laptop owner's hard disk in one of their data centers, just as they already do with phone and Internet records?
  • How long will it be before every fast food or coffee chain with a "free" wifi service starts dipping in to the data exposed by these vulnerabilities as part of their customer profiling initiatives?
  • Since Intel's admissions in May, has anybody seen any evidence that anything is changing though, either in what vendors are offering or in terms of how companies and governments outside the US buy technology?
Share your thoughts This issue was recently raised on the LibrePlanet mailing list. Please feel free to join the list and click here to reply on the thread.

3 September 2017

Lior Kaplan: FOSScamp Syros 2017 day 1

During Debconf17 I was asked by Daniel Pocock if I can attend FOSScamp Syros to help with Debian s l10n in the Balkans. I said I would be happy to, although my visit would be short (2.5 days) due to previous plans. The main idea of camp is to have FOSS people meet for about 1 week near a beach. So it s sun, water and free software. This year it takes place in Syros, Greece. After take the morning ferry, I met with the guys at noon. I didn t know how would it be, as it s my first time with this group/meeting, but they were very nice and welcoming. 10 minutes after my arrival I found myself setting with two of the female attendees starting to work on Albanian (sq) translation of Debian Installer. It took my a few minutes to find my where to check out the current level1 files, as I thought they aren t in SVN anymore, but ended up learning the PO files is the only part of the installer still on SVN. As the girls were quick with the assinged levle1 sublevels, I started to look for the level2 and level3 files, and it was annoying to have the POT files very accessible, but no links to the relevant git repositories. I do want to have all the relevant links in one central place, so people who want to help with translation could do that. While some of the team member just used a text editor to edit the files, I suggested to them using either poedit or granslator, both I used a few years ago. Yaron Shahrabani also recommended virtaal to me, but after trying it for a while I didn t like it (expect it s great feature showing the diff with fuzzy messages). For the few people who also have Windows on their machine, both poedit and Virtaal have windows binaries for download. So you don t have to have Linux in order to help with translations. In parallel, I used the free time to work on the Hebrew translation for level1, as it s been a while since either me or Omer Zak worked on it. Quite soon the guys started to send me the files for review, and I did find some errors using diff. Especially when not everyone use a PO editor. I also missed a few strings during the review, which got fixed later on by Christian Perrier. Team work indeed (: I found it interesting to see the reactions and problems for the team to work with the PO files, and most projects now use some system (e.g. Pootle) for online web translation. Which saves some of the head ace, but also prevents from making some review and quality check before submitting the files. It s a good idea to explore this option for Debian as well. A tip for those who do want to work with PO files, either use git s diff features or use colordiff to check your changes (notice less will require -R parameter to keep the color). Although I met the guys only at noon, the day was very fruitful for Debian Installer l10n: Some files are still work in progress and will be completed tomorrow. My goal is to have Albanian at 100% during the camp and ready for the next d-i alpha. I must admit that I remember d-i to have many more strings as part of the 3 levels, especially levels 2+3 which were huge (e.g. the iso codes). Except all the work and FOSS related conversations, I found a great group who welcomed me quickly, made me feel comfortable and taught me a thing or two about Greece and the Syros specifically. TIP: try the dark chocolate with red hot chili pepper in the icecream shop.
Filed under: Debian GNU/Linux, i18n & l10n

Thorsten Alteholz: My Debian Activities in August 2017

FTP assistant This month I accepted 217 packages and rejected 16 uploads. Though this might seem to be a low number this month, I am very pleased about the total number of packages that have been accepted: 558. Debian LTS This was my thirty-eight month that I did some work for the Debian LTS initiative, started by Raphael Hertzog at Freexian. This month my all in all workload has been 20.25h. During that time I did LTS uploads of: I also did the upload and sent the DLA for [DLA 1061-1] newsbeuter security update Last but not least I also spent some time for frontdesk duties. Other stuff As announced last month I finished uploading all dependencies of glewlwyd and now we have an oauth2 server available in Debian. This month I am trying to really use it and will tell you about my experiences. As the severity of the gcc-7 bugs have been raised, I took care of: #853501, #853304, #853305, #853306, #853307, #853308 and #871088 I also uploaded a new version of duktape and now try to also provide a library that can be used in other packages. Last but not least my DOPOM of this month has been oysttyer. Actually it is a new package, but as ttytter has been abandonded upstream, this is the replacement. It is a fork so you should only get a new authorization key and simply use it as ttytter before.

2 September 2017

Antoine Beaupr : My free software activities, August 2017

Debian Long Term Support (LTS) This is my monthly Debian LTS report. This month I worked on a few major packages that took a long time instead of multiple smaller issues. Affected packages were Mercurial, libdbd-mysql-perl and Ruby.

Mercurial updates Mercurial was vulnerable to two CVEs: CVE-2017-1000116 (command injection on clients through malicious ssh URLs) and CVE-2017-1000115 (path traversal via symlink). The former is an issue that actually affects many other similar software like Git (CVE-2017-1000117), Subversion (CVE-2017-9800) and even CVS (CVE-2017-12836). The latter symlink issue is a distinct issue that came up during an internal audit. The fix, shipped as DLA-1072-1, involved a rather difficult backport, especially because the Mercurial test suite takes a long time to complete. This reminded me of the virtues of DEB_BUILD_OPTIONS=parallel=4, which sped up the builds considerably. I also discovered that the Wheezy build chain doesn't support sbuild's --source-only-changes flag which I had hardcoded in my sbuild.conf file. This seems to be simply because sbuild passes --build=source to dpkg-buildpackage, an option that is supported only in jessie or later.

libdbd-mysql-perl I have worked on fixing two issues with the libdbd-mysql-perl package, CVE-2017-10788 and CVE-2017-10789, which resulted in the DLA-1079-1 upload. Behind this mysteriously named package sits a critical piece of infrastructure, namely the mysql commandline client which is probably used and abused by hundreds if not thousands of home-made scripts, but also all of Perl's MySQL support, which is probably used by even a larger base of software. Through the Debian bug reports (Debian bug #866818 and Debian bug #866821), I have learned that the patches existed in the upstream tracker but were either ignored or even reverted in the latest 4.043 upstream release. It turns out that there are talks of forking that library because of maintainership issue. It blows my mind that such an important part of MySQL is basically unmaintained. I ended up backporting the upstream patches, which was also somewhat difficult because of the long-standing issues with SSL support in MySQL. The backport there was particularly hard to test, as you need to run that test suite by hand, twice: once with a server configured with a (valid!) SSL certificate and one without (!). I'm wondering how much time it is really worth spending on trying to fix SSL in MySQL, however. It has been badly broken forever, and while the patch is an improvement, I would actually still never trust SSL transports in MySQL over an untrusted network. The few people that I know use such transports wrap their connections around a simpler stunnel instead. The other issue was easier to fix so I submitted a pull request upstream to make sure that work isn't lost, although it is not clear what the future of that patch (or project!) will be at this point.

Rubygems I also worked on the rubygems issues, which, thanks to the "vendoring" practice of the Ruby community, also affects the ruby1.9 package. 4 distinct CVEs were triaged here (CVE-2017-0899, CVE-2017-0900, CVE-2017-0901 and CVE-2017-0902) and I determined the latter issue didn't affect wheezy as rubygems doesn't do its own DNS resolution there (later versions lookup SRV records). This is another package where the test suite takes a long time to run. Worse, the packages in Wheezy actually fails to build from source: the test suites just fail in various steps, particularly because of dh key too small errors for Rubygems, but also other errors for Ruby. I also had trouble backporting one test which I had to simply skip for Rubygems. I uploaded and announced test packages and hopefully I'll be able to complete this work soon, although I would certainly appreciate any help on this...

Triage I took a look at the sox, libvorbis and exiv2 issues. None had fixes available. sox and exiv2 were basically a list of fuzzing issues, which are often minor or at least of unknown severity. Those would have required a significant amount of work and I figured I would prioritize other work first. I also triaged CVE-2017-7506, which doesn't seem to affect the spice package in wheezy, after doing a fairly thorough audit of the code. The vulnerability is specifically bound to the reds_on_main_agent_monitors_config function, which is simply not present in our older version. A hostile message would fall through the code and not provoke memory allocation or out of bounds access, so I simply marked the wheezy version as not-affected, something which usually happens during the original triage but can also happen during the actual patching work, as in this case.

Other free software work This describes the volunteer work I do on various free software projects. This month, again, my internal reports show that I spent about the same time on volunteer and paid time, but this is probably a wrong estimate because I spent a lot of time at Debconf which I didn't clock in...

Debconf So I participated in the 17th Debian Conference in Montreal. It was great to see (and make!) so many friends from all over the world in person again, and I was happy to work on specific issues together with other Debian developers. I am especially thankful to David Bremner for fixing the syncing of the flagged tag when added to new messages (patch series). This allows me to easily sync the one tag (inbox) that is not statically assigned during notmuch new, by using flagged as a synchronization tool. This allows me to use notmuch more easily across multiple machines without having to sync all tags with dump/restore or using muchsync which wasn't working for me (although a new release came out which may fix my issues). The magic incantation looks something like this: 
notmuch tag -inbox tag:inbox and not tag:flagged
notmuch tag +inbox not tag:inbox and tag:flagged
However, most of my time in the first week (Debcamp) was spent trying to complete the networking setup: configure switches, setup wiring and so on. I also configured an apt-cacher-ng proxy to serve packages to attendees during the conference. I configured it with Avahi to configure clients automatically, which led me to discover (and fix) issue Debian bug #870321) although there are more issues with the autodiscovery mechanism... I spent extra time to document the (somewhat simple) configuration of such a server in the Debian wiki because it was not the first time I had research that procedure... I somehow thought this was a great time to upgrade my laptop to stretch. Normally, I keep that device running stable because I don't use it often and I don't want to have major traumatizing upgrades every time I leave with it on a trip. But this time was special: there were literally hundreds of Debian developers to help me out if there was trouble. And there was, of course, trouble as it turns out! I had problems with the fonts on my display, because, well, I had suspended (twice) my laptop during the install. The fix was simply to flush the fontconfig cache, and I tried to document this in the fonts wiki page and my upgrades page. I also gave a short training called Debian packaging 101 which was pretty successful. Like the short presentation I made at the last Montreal BSP, the workshop was based on my quick debian development guide. I'm thinking of expanding this to a larger audience with a "102" course that would discuss more complex packaging problems. But my secret plan (well, secret until now I guess) is to make packaging procedures more uniform in Debian by training new Debian packagers using that same training for the next 2 decades. But I will probably start by just trying to do this again at the next Debconf, if I can attend.

Debian uploads I also sponsored two packages during Debconf: one was a "scratch an itch" upload (elpa-ivy) which I requested (Debian bug #863216) as part of a larger effort to ship the Emacs elisp packages as Debian packages. The other was an upload of diceware to build the documentation in a separate package and fix other issues I have found in the package during a review. I also uploaded a bunch of other fixes to the Debian archive:

Signing keys rotation I also started the process of moving my main OpenPGP certification key by adding a signing subkey. The subkey is stored in a cryptographic token so I can sign things on more than one machine without storing that critical key on all those devices physically. Unfortunately, this meant that I need to do some shenanigans when I want to sign content in my Debian work, because the new subkey takes time to propagate to the Debian archive. For example, I have to specify the primary key with a "bang" when signing packages (debsign -k '792152527B75921E!' ...) or use inline signatures in email sent for security announcement (since that trick doesn't work in Mutt or Notmuch). I tried to figure out how to better coordinate this next time by reading up documentation on keyring.debian.org, but there is no fixed date for key changes on the rsync interface. There are "monthly changes" so one's best bet is to look for the last change in their git repository.

GitLab.com and LFS migration I finally turned off my src.anarc.at git repository service by moving the remaining repos to GitLab. Unfortunately, GitLab removed support for git-annex recently, so I had to migrate my repositories to Git-LFS, which was an interesting experience. LFS is pretty easy to use, definitely simpler than git-annex. It also seems to be a good match for the use-case at hand, which is to store large files (videos, namely) as part of slides for presentations. It turns out that their migration guide could have been made much simpler. I tried to submit those changes to the documentation but couldn't fork the GitLab EE project to make a patch, so I just documented the issue in the original MR for now. While I was there I filed a feature request to add a new reference shortcut (GL-NNN) after noticing a similar token used on GitHub. This would be a useful addition because I often have numbering conflicts between Debian BTS bug numbers and GitLab issues in packages I maintain there. In particular, I have problems using GitLab issue numbers in Monkeysign, because commit logs end up in Debian changelogs and will be detected by the Debian infrastructure even though those are GitLab bug numbers. Using such a shortcut would avoid detection and such a conflict.

Numpy-stats I wrote a small tool to extract numeric statistics from a given file. I often do ad-hoc benchmarks where I store a bunch of numbers in a file and then try to make averages and so on. As an exercise in learning NumPy, I figured I would write such a simple tool, called numpy-stats, which probably sounds naive to seasoned Python scientists. My incentive was that I was trying to figure out what was the distribution of password length in a given password generator scheme. So I wrote this simple script: 
for i in seq 10000 ; do
    shuf -n4 /usr/share/dict/words   tr -d '\n'
done > length
And then feed that data in the tool: 
$ numpy-stats lengths 
 
  "max": 60, 
  "mean": 33.883293722913464, 
  "median": 34.0, 
  "min": 14, 
  "size": 143060, 
  "std": 5.101490225062775
I am surprised that there isn't such a tool already: hopefully I am wrong and will just be pointed towards the better alternative in the comments here!

Safe Eyes I added screensaver support to the new SafeEyes project, which I am considering as a replacement to the workrave project I have been using for years. I really like how the interruptions basically block the whole screen: way more effective than only blocking the keyboard, because all potential distractions go away. One feature that is missing is keystrokes and mouse movement counting and of course an official Debian package, although the latter would be easy to fix because upstream already has an unofficial build. I am thinking of writing my own little tool to count keystrokes, since the overlap between SafeEyes and such a counter isn't absolutely necessary. This is something that workrave does, but there are "idle time" extensions in Xorg that do not need to count keystrokes. There are already certain tools to count input events, but none seem to do what I want (most of them are basically keyloggers). It would be an interesting test to see if it's possible to write something that would work both for Xorg and Wayland at the same time. Unfortunately, preliminary research show that:
  1. in Xorg, the only way to implement this is to sniff all events, ie. to implement a keylogger
  2. in Wayland, this is completely unsupported. it seems some compositors could implement such a counter, but then it means that this is compositor specific, or, in other words, unportable
So there is little hope here, which brings to my mind "painmeter" as an appropriate name for this future programming nightmare.

Ansible I sent my first contribution to the ansible project with a small documentation fix. I had an eye opener recently when I discovered a GitLab ansible prototype that would manipulate GitLab settings. When I first discovered Ansible, I was frustrated by the YAML/Jinja DSL: it felt silly to write all this code in YAML when you are a Python developer. It was great to see reasonably well-written Python code that would do things and delegate the metadata storage (and only that!) to YAML, as opposed to using YAML as a DSL. So I figured I would look at the Ansible documentation on how this works, but unfortunately, the Ansible documentation is severly lacking in this area. There are broken links (I only fixed one page) and missing pieces. For example, the developing plugins page doesn't explain how to program a plugin at all. I was told on IRC that: "documentation around developing plugins is sparse in general. the code is the best documentation that exists (right now)". I didn't get a reply when asking which code in particular could provide good examples either. In comparison, Puppet has excellent documentation on how to create custom types, functions and facts. That is definitely a turn-off for a new contributor, but at least my pull request was merged in and I can only hope that seasoned Ansible contributors expand on this critical piece of documentation eventually.

Misc As you can see, I'm all over the place, as usual. GitHub tells me I "Opened 13 other pull requests in 11 repositories" (emphasis mine), which I guess means on top of the "9 commits in 5 repositories" mentioned earlier. My profile probably tells a more detailed story that what would be useful to mention here. I should also mention how difficult it is to write those reports: I basically do a combination of looking into my GitHub and GitLab profiles, the last 30 days of emails (!) and filesystem changes (!!). En vrac, a list of changes which may be of interest:
  • font-large (and its alias, font-small): shortcut to send the right escape sequence to rxvt so it changes its font
  • fix-acer: short script to hardcode the modeline (you remember those?!) for my screen which has a broken EDID pin (so autodetection fails, yay Xorg log files...)
  • ikiwiki-pandoc-quickie: fake ikiwiki renderer that (ab)uses pandoc to generate a HTML file with the right stylesheet to preview Markdown as it may look in this blog (the basic template is missing still)
  • git-annex-transfer: a command I've often been missing in git-annex, which is a way to transfer files between remotes without having to copy them locally (upstream feature request)
  • I linked the graphics of the Debian archive software architecture in the Debian wiki in the hope more people notice it.
  • I did some tweaks on my Taffybar to introduce a battery meter and hoping to have temperature sensors, which mostly failed. there's a pending pull request that may bring some sense into this, hopefully.
  • I made two small patches in Monkeysign to fix gpg.conf handling and multiple email output, a dumb bug I cannot believe anyone noticed or reported just yet. Thanks Valerie for the bug report! The upload of this in Debian is pending a review from the release team.

Wouter Verhelst: Playing with Moose and FFmpeg

As I've blogged before, I've been on and off working on SReview, a video review system. Development over the past year has been mostly driven by the need to have something up and running for first FOSDEM 2017, and then DebConf17, and so I've cut corners left and right which made the system, while functional, not quite entirely perfect everywhere. For instance, the backend scripts were done in ad-hoc perl, each reinventing their own wheel. Doing so made it easier for me to experiment with things and figure out where I want them to go, without immediately creating a lot of baggage that is not necessarily something I want to be stuck to. This flexibility has already paid off, in that I've redone the state machine between FOSDEM and DebConf17 and all it needed was to update a few SQL statements here and there. Well, and add a few of them, too. It was always the intent to replace most of the ad-hoc perl with something better, however, once the time was ripe. One place where historical baggage is not so much of a problem, and where in fact abstracting away the complexity would now be an asset, is in the area of FFmpeg command lines. Currently, these are built by simple string expansion. For example, we do something like this (shortened for brevity): 
system("ffmpeg -y -i $outputdir/$slug.ts -pass 1 -passlogfile ...");
inside an environment where the $outputdir and $slug variables are set in a perl environment. That works, but it has some downsides; e.g., adding or removing options based on which codecs we're using is not so easy. It would be much more flexible if the command lines were generated dynamically based on requested output bandwidth and codecs, rather than that they be hardcoded in the file. Case in point: currently there are multiple versions of some of the backend scripts, that only differ in details mostly the chosen codec on the ffmpeg command line. Obviously this is suboptimal. Instead, we want a way where video file formats can be autodetected, so that I can just say "create a file that uses encoder etc settings of this other file here". In addition, we also want a way where we can say "create a file that uses encoder etc settings of this other file here, except for these one or two options that I want to fine-tune manually". When I first thought about doing that about a year ago, that seemed complicated and not worth it or at least not to that extent. Enter Moose. The Moose OO system for Perl 5 is an interesting way to do object orientation in Perl. I knew Perl supports OO, and I had heard about Moose, but never had looked into it, mostly because the standard perl OO features were "good enough". Until now. Moose has a concept of adding 'attributes' to objects. Attributes can be set at object construction time, or can be accessed later on by way of getter/setter functions, or even simply functions named after the attribute itself (the default). For more complicated attributes, where the value may not be known until some time after the object has been created, Moose borrows the concept of "lazy" variables from Perl 6: 
package Object;
use Moose;
has 'time' => (
    is => 'rw',
    builder => 'read_time',
    lazy => 1,
);
sub read_time  
    return localtime();
The above object has an attribute 'time', which will not have a value initially. However, upon first read, the 'localtime()' function will be called, the result is cached, and then (and on all further calls of the same function), the cached result will be returned. In addition, since the attribute is read/write, the time can also be written to. In that case, any cached value that may exist will be overwritten, and if no cached value exists yet, the read_time function will never be called. (it is also possible to clear values if needs be, so that the function would be called again). We use this with the following pattern: 
package SReview::Video;
use Moose;
has 'url' => (
    is => 'rw',
)
has 'video_codec' => (
    is => 'rw',
    builder => '_probe_videocodec',
    lazy => 1,
);
has 'videodata' => (
    is => 'bare',
    reader => '_get_videodata',
    builder => '_probe_videodata',
    lazy => 1,
);
has 'probedata' => (
    is => 'bare',
    reader => '_get_probedata',
    builder => '_probe',
    lazy => 1,
);
sub _probe_videocodec  
    my $self = shift;
    return $self->_get_videodata-> codec_name ;
 
sub _probe_videodata  
    my $self = shift;
    if(!exists($self->_get_probedata-> streams ))  
        return  ;
     
    foreach my $stream(@ $self->_get_probedata-> streams )  
        if($stream-> codec_type  eq "video")  
            return $stream;
         
     
    return  ;
 
sub _probe  
    my $self = shift;
    open JSON, "ffprobe -print_format json -show_format -show_streams " . $self->url . " "
    my $json = "";
    while(<JSON>)  
        $json .= $_;
     
    close JSON;
    return decode_json($json);
The videodata and probedata attributes are internal-use only attributes, and are therefore of the 'bare' type that is, they cannot be read nor written to. However, we do add 'reader' functions that can be used from inside the object, so that the object itself can access them. These reader functions are generated, so they're not part of the object source. The probedata attribute's builder simply calls ffprobe with the right command-line arguments to retrieve data in JSON format, and then decodes that JSON file. Since the passed JSON file contains an array with (at least) two streams one for video and one for audio and since the ordering of those streams depends on the file and is therefore not guaranteed, we have to loop over them. Since doing so in each and every attribute of the file we might be interested in would be tedious, we add a videodata attribute that just returns the data for the first found video stream (the actual source also contains a similar one for audio streams). So, if you create an SReview::Video object and you pass it a filename in the url attribute, and then immediately run print $object->video_codec, then the object will However, if the caller first calls $object->video_codec('h264'), then the ffprobe and most of the caching will be skipped, and instead the h265 data will be returned as video codec name. Okay, so with a reasonably small amount of code, we now have a bunch of attributes that have defaults based on actual files but can be overwritten when necessary. Useful, right? Well, you might also want to care about the fact that sometimes you want to generate a video file that uses the same codec settings of this other file here. That's easy. First, we add another attribute: 
has 'reference' => (
    is => 'ro',
    isa => 'SReview::Video',
    predicate => 'has_reference'
);
which we then use in the _probe method like so: 
sub _probe  
    my $self = shift;
    if($self->has_reference)  
        return $self->reference->_get_probedata;
     
    # original code remains here
With that, we can create an object like so: 
my $video = SReview::Video->new(url => 'file.ts');
my $generated = SReview::Video->new(url => 'file2.ts', reference => $video);
now if we ask the $generated object what the value of its video_codec setting is without telling it ourselves first, it will use the $video object for its probed data, and use that. That only misses generating the ffmpeg command line, but that's all fairly straightforward and therefore left as an exercise to the reader. Or you can cheat, and look it up.

Next.

Previous.