Warning when swupd client extracts symbolic links about mixer-tools

[cmarcelo]

The symbolic links in question do have non ASCII characters.

Extracting os-core pack for version 50
Warning: Linkname can't be converted from UTF-8 to current locale.
  Issue with header for entry: staged/dbd127931f8a330113afd10bfe3979d7b395a0d88c407473cb3db5ee1aa36b2e
  with link: TÜBİTAK_UEKAE_Kök_Sertifika_Hizmet_Sağlayıcısı_-_Sürüm_3.crt
Warning: Linkname can't be converted from UTF-8 to current locale.
  Issue with header for entry: staged/1b2f6102fac7898b72bbaaeb0fa580a2d693598b1adc9ebbcc9f14c5063aa762
  with link: AC_Raíz_Certicámara_S.A..crt
Warning: Linkname can't be converted from UTF-8 to current locale.
  Issue with header for entry: staged/ca61e50a8e4b1bcb36aafabb66e11fecadaafd8a2b93b69ff61b5a567b6d1b15
  with link: TÜRKTRUST_Elektronik_Sertifika_Hizmet_Sağlayıcısı_H5.crt
Warning: Linkname can't be converted from UTF-8 to current locale.
  Issue with header for entry: staged/5ea38d0b2dfd812a72ca4b9c2a893c8723963c12397096f86455d85042101272
  with link: NetLock_Arany_=Class_Gold=_Főtanúsítvány.crt
Warning: Linkname can't be converted from UTF-8 to current locale.
  Issue with header for entry: staged/21d89e644fd57b4194364d356799ae200da61b936a184ab74667ee50866e84bc
  with link: TÜRKTRUST_Elektronik_Sertifika_Hizmet_Sağlayıcısı_H6.crt
Warning: Linkname can't be converted from UTF-8 to current locale.
  Issue with header for entry: staged/538da6ab585223433a079f1c43799d1d6e8ec9c6cdf073125435ae330c52ff1e
  with link: Certinomis_-_Autorité_Racine.crt

Next step is to see how encoding from GNU tar (used in swupd-server) is different than Go tar package so that libarchive doesn't complain about it.

[cmarcelo]

• Go tar encodes the symbolic link using a PAX record "linkpath". UTF-8. Gets warning from swupd client.
• GNU tar encodes it using a GNU format header. UTF-8. No warning from swupd client.

Also tested in Go 1.10 (still unreleased), which contains a way to force the use of GNU extension for an entry.

• Go 1.10 by default for that file still produces PAX + linkpath.
• Go 1.10 tar forcing GNU format header. UTF-8. No warning from swupd client.

After inspecting the output tar files from various combinations and formats, I think that the files we are generating are sound. The warning message from libarchive seems misleading, as libarchive can handle correctly the GNU one. My current guess:

One mitigation for us, once Go 1.10 is release is to force GNU format for any symbolic link that has non ASCII characters.

I haven't looked deeply at libarchive, so next step is to check if we could explicitly state the UTF-8 in our usage of libarchive.

Given that the files themselves are being correctly written by swupd client besides the warning AND in a couple of weeks we'll have a mitigation, I'll likely put this on a lower priority.

[cmarcelo]

I couldn't revisit this. I still think it is something on swupd client side. Go 1.10 will be released soon so we can apply the workaround for the minimum effort.

The workaround: set the format to GNU in the header of any symbolic link we archive.

[cmarcelo]

For debugging libarchive, a starting point:

<thiago> if anyone wnats to debug this, put a breakpoint in archive_entry.c line 1301 with condition r != 0
<thiago> the debug fuse doesn't work for me (container)

[matthewrsj]

swupd now uses a more recent version of libarchive. This needs to be tested to see if it is still an issue.

[reaganlo]

This has been fixed.