Deleted directory path not recorded when running rmdir with slash at directory path end

[Steve Grubb]

On Thursday, March 4, 2021 10:09:35 PM EST Alan Evangelista wrote:
> If I run the rmdir command with a directory path with a slash at its end,
> Audit doesn't record the deleted directory path.
> 
> Audit rule:
> -a always,exit -F dir=/sasdata -F arch=b64 -S creat -S open -S openat -S
> unlink -S unlinkat -S symlink -S symlinkat -S link -S linkat -S rename -S
> renameat -S chmod -S fchmod -S fchmodat -S chown -S fchown -S fchownat -S
> mkdir -S mkdirat -S rmdir -S setxattr -S lsetxattr -S fsetxattr -S
> removexattr -S lremovexattr -S fremovexattr -k filesystem_op
> 
> Test command:
> rmdir /sasdata/testdir
> 
> Audit output:
> 
> type=SYSCALL msg=audit(1614912311.117:4136): arch=c000003e syscall=84
> success=yes exit=0 a0=7ffcf6e5c757 a1=2 a2=7f200050f280 a3=7ffcf6e5b660
> items=3 ppid=17590 pid=22579 auid=201327714 uid=0 gid=0 euid=0 suid=0
> fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts1 ses=269 comm=\"rmdir\"
> exe=\"/usr/bin/rmdir\" key=\"filesystem_op\"","type=CWD
> msg=audit(1614912311.117:4136):  cwd=\"/home/aevangelista\""
> 
> type=PATH msg=audit(1614912311.117:4136): item=0 name=\"/sasdata/\"
> inode=100916940 dev=08:04 mode=040775 ouid=0 ogid=201327708 rdev=00:00
> objtype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0
> cap_fver=0
> 
> type=PATH msg=audit(1614912311.117:4136): item=1 name=(null)
> inode=100916940 dev=08:04 mode=040775 ouid=0 ogid=201327708 rdev=00:00
> objtype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0
> cap_fver=0
> 
> type=PATH msg=audit(1614912311.117:4136): item=2 name=(null) inode=1181650
> dev=08:04 mode=040755 ouid=0 ogid=0 rdev=00:00 objtype=DELETE
> cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0

I'm guessing that this ^^^ record is the directory that was removed. But as 
this is syscall exit, it has been removed and has no name.

> type=PROCTITLE msg=audit(1614912311.117:4136):
> proctitle=726D646972002F736173646174612F746573746469722F
> 
> Shouldn't the directory path be recorded somewhere, regardless if there is
> a slash at the end of the directory path?

I want to think this was a problem on older kernels. The solution was to also 
place a watch on the directory itself  ( -F path=/sasdata ). It has nothing 
to do with the trailing slash.

-Steve

> I found this issue while using Auditbeat, a collector of Linux Audit events
> used for integration with Elasticsearch. Related discussion:
> https://discuss.elastic.co/t/rmdir-syscall-event-and-file-path/266015/3
> 
> Thanks in advance.