Permit unix_chkpwd & pam_unix.so to run without being setuid-root. #373
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Remove the hard-coding of the idea that the only way pam_unix.so can read the shadow file is if it can, in some way, run setuid-root. Linux capabilities only require cap_dac_override to read the /etc/shadow file. This change achieves two things: it opens a path for a linux-pam application to run without being setuid-root; further, it allows unix_chkpwd to run non-setuid-root if it is installed: sudo setcap cap_dac_override=ep unix_chkpwd If we wanted to link against libcap, we could install this binary with cap_dac_override=p, and use cap_set_proc() to raise the effective bit at runtime. However, some distributions already link unix_chkpwd against libcap-ng for some, likely spurious, reason so "ep" is fine for now. Signed-off-by: Andrew G. Morgan <[email protected]>
t8m
approved these changes
Jun 29, 2021
|
@ldv-alt This LGTM so I'll merge unless you have any comments, objections. |
ldv-alt
approved these changes
Jun 29, 2021
|
Merged to master. Thank you for the pull request! |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Remove the hard-coding of the idea that the only way pam_unix.so can
read the shadow file is if it can, in some way, run setuid-root.
Linux capabilities only require cap_dac_override to read the /etc/shadow
file.
This change achieves two things: it opens a path for a linux-pam
application to run without being setuid-root; further, it allows
unix_chkpwd to run non-setuid-root if it is installed:
sudo setcap cap_dac_override=ep unix_chkpwd
If we wanted to link against libcap, we could install this binary with
cap_dac_override=p, and use cap_set_proc() to raise the effective bit
at runtime. However, some distributions already link unix_chkpwd
against libcap-ng for some, likely spurious, reason so "ep" is fine
for now.
Signed-off-by: Andrew G. Morgan [email protected]