bugGNU tar - Bugs: bug #56421, security.capability extended...

 
 

bug #56421: security.capability extended attributes not restored upon extraction with --xattrs

Submitter:  None
Submitted:  Thu 30 May 2019 08:57:16 PM UTC
 
Category:  None Severity:  3 - Normal
Item Group:  None Status:  None
Privacy:  Public Assigned to:  None
Open/Closed:  Open
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Thu 06 Jun 2019 06:34:47 PM UTC, comment #3: 

Come to find that it is a deliberate decision to only extract the "user.*" extended attributes by default.

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

Brian Murray <bdmurray>
Mon 03 Jun 2019 10:19:08 PM UTC, comment #2: 

I've came across this bug a few years back (https://stackoverflow.com/questions/42414607/tar-not-preserving-extended-attributes-of-trusted-namespace/44753270#44753270) - It's important to note that when using (upon extraction) --xattrs --xattrs-include=* the security attributes does get extracted, only you need sudo privileges to set it

Jordan Cohen <ymec>
Sat 01 Jun 2019 12:08:39 AM UTC, comment #1: 

I'm the original reporter of this bug and I've tested this a bit more and discovered that actually only user.* extended attributes are extracted. Reading xattrs_kw_included() in xattrs.c this seems deliberate but I could find no indication why in the git history.

Brian Murray <bdmurray>
Thu 30 May 2019 08:57:16 PM UTC, original submission:  

The following page indicates that "By default, when `--xattr' is used, all names are stored in the archive (or extracted, if using `--extract')." However, this only seems to be true for create and not for extract as one must use "--xattrs-include=*" for the security capabilities to be restored.

https://www.gnu.org/software/tar/manual/tar.html#SEC70

Here's a 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"

This was tested using tar version 1.30+dfsg-6 on Ubuntu 19.10 but the source code for extract.c looks the same so I believe the same issue exists with the upstream version of tar.

Anonymous

 

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