Capabilities question

Capabilities question

[Torsten Foertsch]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi,

what is the right way to get the current capability setting inherited through 
execve()?

My goal is a wrapper program that sets the needed capabilities and then 
execve()s the real program. These capabilities should also be inherited if 
the real program spawns childs via fork/exec.

Is that possible?

I read the appropriate parts of fs/exec.c where 
/*
 * This function is used to produce the new IDs and capabilities
 * from the old ones and the file's capabilities.
 *
 * The formula used for evolving capabilities is:
 *
 *       pI' = pI
 * (***) pP' = (fP & X) | (fI & pI)
 *       pE' = pP' & fE          [NB. fE is 0 or ~0]
 *
 * I=Inheritable, P=Permitted, E=Effective // p=process, f=file
 * ' indicates post-exec(), and X is the global 'cap_bset'.
 *
 */
is implemented. The problem is that fP and fE are either 0 or ~0 depending on 
the current uid or the uid of the file to be executed (if S_ISUID). Thus pP' 
is only masked by cap_bset which is a global constant (0xfffffeff).

Torsten
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.7 (GNU/Linux)

iD8DBQE+XlsbwicyCTir8T4RAjaaAJ9dU8E0YWy1fBnf6OdIX0wr7aQQ2gCgwObJ
aSAxVyLvV0n4MN4E84VVERg=
=YE3a
-----END PGP SIGNATURE-----