Date: Wed, 18 Oct 2023 18:03:57 GMT From: Mitchell Horne <mhorne@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 26ff4836c888 - releng/14.0 - cr_canseeothergids(): Use real instead of effective group membership Message-ID: <202310181803.39II3vrm045009@gitrepo.freebsd.org>
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The branch releng/14.0 has been updated by mhorne: URL: https://cgit.FreeBSD.org/src/commit/?id=26ff4836c88812b9ee03c4cc127ba2b467173a0e commit 26ff4836c88812b9ee03c4cc127ba2b467173a0e Author: Olivier Certner <olce.freebsd@certner.fr> AuthorDate: 2023-08-17 23:54:45 +0000 Commit: Mitchell Horne <mhorne@FreeBSD.org> CommitDate: 2023-10-18 18:01:49 +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. Approved by: re (gjb) PR: 272093 Reviewed by: mhorne Sponsored by: Kumacom SAS Differential Revision: https://reviews.freebsd.org/D40642 Differential Revision: https://reviews.freebsd.org/D40644 (cherry picked from commit 91658080f1a598ddda03943a783c9a941199f7d2) (cherry picked from commit 0452dd841336cea7cd979b13ef12b6ea5e992eff) (cherry picked from commit 4e7cea61051abc476c64e4a996397235f5a881bc) --- share/man/man9/cr_bsd_visible.9 | 2 +- share/man/man9/cr_canseeothergids.9 | 8 ++++---- sys/kern/kern_prot.c | 23 ++++++++++------------- 3 files changed, 15 insertions(+), 18 deletions(-) diff --git a/share/man/man9/cr_bsd_visible.9 b/share/man/man9/cr_bsd_visible.9 index bd676e6f5705..f2d42f3835dc 100644 --- a/share/man/man9/cr_bsd_visible.9 +++ b/share/man/man9/cr_bsd_visible.9 @@ -97,7 +97,7 @@ and are not members of any common group .Po as determined by -.Xr groupmember 9 +.Xr realgroupmember 9 .Pc . .It Bq Er ESRCH Credentials diff --git a/share/man/man9/cr_canseeothergids.9 b/share/man/man9/cr_canseeothergids.9 index f0c1e5c4e726..109d41a8545d 100644 --- a/share/man/man9/cr_canseeothergids.9 +++ b/share/man/man9/cr_canseeothergids.9 @@ -48,9 +48,9 @@ This function checks if a subject associated to credentials is denied seeing a subject or object associated to credentials .Fa u2 by a policy that requires both credentials to have at least one group in common. -For this determination, the effective and supplementary group IDs are used, but -not the real group IDs, as per -.Xr groupmember 9 . +For this determination, the real and supplementary group IDs are used, but +not the effective group IDs, as per +.Xr realgroupmember 9 . .Pp This policy is active if and only if the .Xr sysctl 8 @@ -79,5 +79,5 @@ Otherwise, it returns .Er ESRCH . .Sh SEE ALSO .Xr cr_bsd_visible 9 , -.Xr groupmember 9 , +.Xr realgroupmember 9 , .Xr priv_check_cred 9 diff --git a/sys/kern/kern_prot.c b/sys/kern/kern_prot.c index 23bd2009582b..43fc3100bfa7 100644 --- a/sys/kern/kern_prot.c +++ b/sys/kern/kern_prot.c @@ -1404,21 +1404,18 @@ SYSCTL_INT(_security_bsd, OID_AUTO, see_other_gids, CTLFLAG_RW, 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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