Oh, I hadn’t noticed this before, but the *NIX read/write/execute bits are represented in that order in the permission bitmask, which is why
1. (Or, an easier mnemonic might be “they’re read in descending order”.)
When using symbolic permissions with
chmod, leaving off the
ugo bit will result in the permission being applied to all three categories. For more complex expressions, different permission changes can be separated with a comma (
,) - for example,
chmod ug+x,o-w file.txt.
Find SUID files:
find / -type f -perm -u=s -ls 2>/dev/null
Not sure if a binary is normally SUID? Compare the results of the above command with the same output on your local (Linux) box.
The presence of the SUID/SGID bit only allows a program to elevate its privileges to match its user/group - a call to
setregid() (or work-alikes) is still required to actually perform the (presumably legitimate) privilege escalation!
In the output of the
id command, the
egid are the effective user and group IDs.
When exploiting binaries that call other binaries, look for places where the absolute path has not been used and then see if you can manipulate the PATH so that a binary you control is called instead!