linux-kernel - Re: EUID != root + EGID = root, and CAP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Sun, 13 Dec 2009 05:19:56 +0000 (UTC)
From:	daw@...berkeley.edu (David Wagner)
To:	linux-kernel@...r.kernel.org
Subject: Re: EUID != root + EGID = root, and CAP_SETGID

Ivan Zahariev  wrote:
>Is this an intended behavior?

Yes.  Setuid/setgid are a mess.  For more details, you might
find the following research papers interesting:

http://www.cs.berkeley.edu/~daw/papers/setuid-usenix02.pdf 
http://www.cs.berkeley.edu/~daw/papers/setuid-login08b.pdf 

See, e.g., Section 5.2 of the former paper, which says:

  "an effective group ID of zero does not accord any
  special privileges to change groups. This is a potential
  source of confusion: it is tempting to assume incorrectly
  that since appropriate privileges are carried by the euid
  in the setuid-like calls, they will be carried by the
  egid in the setgid-like calls, but this is not how it
  actually works. This misconception caused a mistake in
  the manual page of setgid in Redhat Linux 7.2 (Section
  6.4.1)."
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/