Date: Thu, 28 Sep 2023 15:10:51 GMT From: Mitchell Horne <mhorne@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 91658080f1a5 - main - cr_canseeothergids(): Use real instead of effective group membership Message-ID: <202309281510.38SFAp4u047838@gitrepo.freebsd.org>
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The branch main has been updated by mhorne: URL: https://cgit.FreeBSD.org/src/commit/?id=91658080f1a598ddda03943a783c9a941199f7d2 commit 91658080f1a598ddda03943a783c9a941199f7d2 Author: Olivier Certner <olce.freebsd@certner.fr> AuthorDate: 2023-08-17 23:54:45 +0000 Commit: Mitchell Horne <mhorne@FreeBSD.org> CommitDate: 2023-09-28 15:05:46 +0000 cr_canseeothergids(): Use real instead of effective group membership Using the effective group and not the real one when testing membership has the consequence that unprivileged processes cannot see setuid commands they launch until these have relinquished their privileges. This is also in contradiction with how the similar cr_canseeotheruids() works, i.e., by taking into account real user IDs. Fix this by substituting groupmember() with realgroupmember(). While here, simplify the code. PR: 272093 Reviewed by: mhorne MFC after: 2 weeks Sponsored by: Kumacom SAS Differential Revision: https://reviews.freebsd.org/D40642 --- sys/kern/kern_prot.c | 23 ++++++++++------------- 1 file changed, 10 insertions(+), 13 deletions(-) diff --git a/sys/kern/kern_prot.c b/sys/kern/kern_prot.c index b62a5e9ee20b..0f15771fb00d 100644 --- a/sys/kern/kern_prot.c +++ b/sys/kern/kern_prot.c @@ -1408,21 +1408,18 @@ SYSCTL_INT(_security_bsd, OID_AUTO, see_other_gids, CTLFLAG_RW, static int cr_canseeothergids(struct ucred *u1, struct ucred *u2) { - int i, match; - if (!see_other_gids) { - match = 0; - for (i = 0; i < u1->cr_ngroups; i++) { - if (groupmember(u1->cr_groups[i], u2)) - match = 1; - if (match) - break; - } - if (!match) { - if (priv_check_cred(u1, PRIV_SEEOTHERGIDS) != 0) - return (ESRCH); - } + if (realgroupmember(u1->cr_rgid, u2)) + return (0); + + for (int i = 1; i < u1->cr_ngroups; i++) + if (realgroupmember(u1->cr_groups[i], u2)) + return (0); + + if (priv_check_cred(u1, PRIV_SEEOTHERGIDS) != 0) + return (ESRCH); } + return (0); }
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