its undocumented that only user.* extended attributes are restored upon extraction

[Brian Murray]

The tar info page and upstream documentation indicate that when --xattr is used "all names are stored in the archive (or extracted, if using '--extract')", however when using --xattr with extract the security.capability extended attributes are not restored. If one also uses "--xattrs-include=*" then the security.capability extended attributes will be restored.

[Test Case]
mkdir orig restore
touch orig/file_with_capability_and_user_xattr
setcap cap_net_raw=p orig/file_with_capability_and_user_xattr
(eoan-amd64)root@impulse:/tmp# getfattr -m . -d orig/file_with_capability_and_user_xattr
# file: orig/file_with_capability_and_user_xattr
security.capability=0sAAAAAgAgAAAAAAAAAAAAAAAAAAA=
user.testkey="testvalue"
(eoan-amd64)root@impulse:/tmp# tar c --xattrs --acls --directory orig/ . | tar x --xattrs --acls --directory restore/
(eoan-amd64)root@impulse:/tmp# getfattr -m . -d restore/file_with_capability_and_user_xattr
# file: restore/file_with_capability_and_user_xattr
user.testkey="testvalue"
(eoan-amd64)root@impulse:/tmp# tar c --xattrs --directory orig/ . | tar x --xattrs --xattrs-include=* --directory restore/
(eoan-amd64)root@impulse:/tmp# getfattr -m . -d restore/file_with_capability_and_user_xattr
# file: restore/file_with_capability_and_user_xattr
security.capability=0sAAAAAgAgAAAAAAAAAAAAAAAAAAA=
user.testkey="testvalue"

I think tar's extract behavior should be changed to match that of create so that all names are actually extracted.

[Brian Murray (brian-murray)]

After discussing this with upstream it became clear that the documentation is incorrect and it is deliberate that only the "user.*" extended attributes are applied by default during extraction.

"This decision was done because only user.* attributes are 100% safe to
extract. The security.* (especially capabilities) can have some binary
format specific to the box creating the archive but incompatible with host
extracting the archive."

https://lists.gnu.org/archive/html/bug-tar/2019-06/msg00001.html

The man for tar should be updated to reflect that to avoid any confusion.

[Brian Murray (brian-murray)]

Given that the only documentation which refers to the default behavior of extended attributes is only included upstream and is not shipped in the Debian or Ubuntu package I'm closing this bug as Invalid.