libpriv: Stop digging in private libcap internals #4769
Merged
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
cargo is complaining about this.
cgwalters
approved these changes
Jan 12, 2024
| { | ||
| /* Unfortunately, libcap doesn't expose any APIs to get the raw xattr value. |
cgwalters
reviewed
Jan 12, 2024
When handling file caps, we need to be able to get the actual xattr bytes. Currently, libcap doesn't provide a public API for this. Meanwhile, we've been hacking around this by redefining internal libcap structs and using internal fields. This is extremely brittle since any change to the struct will break us. And this is exactly what happened in the libcap currently in rawhide. A new field was added to the struct: https://git.kernel.org/pub/scm/libs/libcap/libcap.git//commit/?id=aca076443591ba18438b60e41294b59a324daf04 This patch works around the lack of a public API a different way: we allocate an `O_TMPFILE`, set caps on it, then read back the xattr. This is more heavyweight but few binaries actually have file caps anyway. It also requires `CAP_SETFCAP`, but that's already the case today since the assembly code also applies them to checked out files on-disk. No new tests for this; we have existing coverage for file caps. That coverage would've caught this if we ran CI against rawhide. Closes coreos#4765
|
Woohoo! Thanks! |
Merged
jmarrero
reviewed
Jan 30, 2024
| { | ||
| /* Unfortunately, libcap doesn't expose any APIs to get the raw xattr value. | ||
| * For now, we hackily dance around this by writting it out to a file and then | ||
| * re-reading from it. */ | ||
| cap_t caps = cap_from_text (fcap); |
There was a problem hiding this comment.
scanner says:
leaked_storage: Variable "caps" going out of scope leaks the storage it points to.
Should we be doing something like free(caps) before returning null?
There was a problem hiding this comment.
Ouch, sorry. Fix in #4811.
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.
When handling file caps, we need to be able to get the actual xattr
bytes. Currently, libcap doesn't provide a public API for this.
Meanwhile, we've been hacking around this by redefining internal libcap
structs and using internal fields. This is extremely brittle since any
change to the struct will break us.
And this is exactly what happened in the libcap currently in rawhide. A
new field was added to the struct:
https://git.kernel.org/pub/scm/libs/libcap/libcap.git//commit/?id=aca076443591ba18438b60e41294b59a324daf04
This patch works around the lack of a public API a different way: we
allocate an
O_TMPFILE, set caps on it, then read back the xattr. Thisis more heavyweight but few binaries actually have file caps anyway. It
also requires
CAP_SETFCAP, but that's already the case today since theassembly code also applies them to checked out files on-disk.
No new tests for this; we have existing coverage for file caps. That
coverage would've caught this if we ran CI against rawhide.
Closes #4765