From nobody Tue Aug 25 15:59:49 2026 X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4hTstG3kJwz6pbP0 for ; Tue, 25 Aug 2026 15:59:50 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "YR2" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4hTstG0jfkz41yZ for ; Tue, 25 Aug 2026 15:59:50 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1787673590; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=JHMYa6BeNiTipBjdBK+jMpjZZf/Xc2949pckvEQT5qo=; b=gDdQzXw7qri8y3o0Kdt8AQNHnBtAZ/YpfUuz+pw1KpZ0k6apc3vHbxsa0DkldRqG6KBGVS dA89dkHtPUDB5KDFocHQtNVi1L/HUd19SxCeGzJdmzFQe4UOZ3A9PDxAz84UYg1Jn3XLfK 3R7La3USrL5HBshzFIw+L4ql+HInnFp4/BGL8E3rPe7ZwmtkaUl4e8rWoWFszNfX1C2FJn yWfPBnH0mqt/oyMzTJ0/+XDMHTUByVjzTBQVg/89IkW62npAIvNTYYYQ8pfDcXsRNSVxYy zL7euC5PmU7FyxoGo/QiPdvwE2cpODOGG8cz8mdOKhIdFHhqgTBA6Wsm7E32JQ== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1787673590; a=rsa-sha256; cv=none; b=oDJnSqVsoi2zQA5huk5dXNiWRM1DOqrK84aewIwhKMF9FzBoI0pcoJlR0uNmTaQ/2LSk32 Lk8HC4f2KjQ3ccZqnkfieTQPCfk7D1Wxufe96bpk1wHHzhlzdISjgaRfPRfF9OfWph+Kqz RI4KQ4H/plPFkcRAGRsOOTnLk7xvx3H8NZJuldzE7EgZb/GyKP9UftmYVpW1eubZpsLrOg fpRYE8tRe+Dyog1GRfvR2WLo2x1dNEBxcNPBGePZS3zDsiBL5zQCodxlo08DgFKlSg5d1N iatO5ErpfBgDQAppjlaz9ZTuVcygCvSNlzgaefF4UU5dsqb9G5nHhCDVjn+2wQ== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1787673590; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=JHMYa6BeNiTipBjdBK+jMpjZZf/Xc2949pckvEQT5qo=; b=SFo4orQONfK+GgxAd1ZEtnrVMesbdcq7PrGBBdr8yv74jKCHa19OXUJFhmd73FIgn7/Kou pFydYB42wTy9vxcHbROFDreF6HBdiPaJkxKPajnMuslHC3yLRBjPOjYOnov3qmBvDcIpiw 0EJbgfPCdwLznBYjrVH1evsmYoNpTwnB0XPtBj6F2cFVf+AYhQRR2Y+pLy1Omz4Ad4z8ZU cH+kRbHxF3hUMP15NuY4rmHRj4RQ3J6W6YAz0Ou+ssSoYGebwaztZ9/xReVDcd4KqQD6ji k80u64H71nWDHZS4m5KGihpS0eG9tnIEeUivX7y/dIoOwuJVM3Gm1h8hHyk+qQ== Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) by mxrelay.nyi.freebsd.org (Postfix) with ESMTP id 4hTstF6l9Nzxt7 for ; Tue, 25 Aug 2026 15:59:49 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from git (uid 1279) (envelope-from git@FreeBSD.org) id 31637 by gitrepo.freebsd.org (DragonFly Mail Agent v0.13+ on gitrepo.freebsd.org); Tue, 25 Aug 2026 15:59:49 +0000 To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org From: Mark Johnston Subject: git: ae27dff4710b - stable/15 - cred: Fix group_is_primary() List-Id: Commit messages for all branches of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all List-Help: List-Post: List-Subscribe: List-Unsubscribe: X-BeenThere: dev-commits-src-all@freebsd.org Sender: owner-dev-commits-src-all@FreeBSD.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: markj X-Git-Repository: src X-Git-Refname: refs/heads/stable/15 X-Git-Reftype: branch X-Git-Commit: ae27dff4710b87f25a909e008cdbe822b5b61667 Auto-Submitted: auto-generated Date: Tue, 25 Aug 2026 15:59:49 +0000 Message-Id: <6a8dbbf5.31637.10cb2e80@gitrepo.freebsd.org> The branch stable/15 has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=ae27dff4710b87f25a909e008cdbe822b5b61667 commit ae27dff4710b87f25a909e008cdbe822b5b61667 Author: Mark Johnston AuthorDate: 2026-08-24 18:13:29 +0000 Commit: Mark Johnston CommitDate: 2026-08-25 15:47:12 +0000 cred: Fix group_is_primary() This helper wasn't updated in commit be1f7435ef21, so in reality it was testing whether "gid" is the first supplemental group. If a user doesn't belong to a supplementary group, then it's testing an uninitialized slot; since ucreds are allocated with M_ZERO, this typically means that we're testing gid == 0. group_is_primary() has exactly one use, in mac_do. There, it's used to determine whether to keep the caller's current primary groups. This means that a rule such as gid=0>uid=0 will permit any credential with no supplementary groups. I believe this is mostly exploitable by daemons which have explicitly dropped privileges and called setgroups(0, NULL); logged in users will have a non-empty supplementary group list by virtue of having gone through initgroups(3). Fix group_is_primary(), and add a regression test. Approved by: so Security: FreeBSD-SA-26:59.mac_do Security: CVE-2026-58092 Reported by: Hazley Samsudin of GovTech CSG Fixes: be1f7435ef21 ("kern: start tracking cr_gid outside of cr_groups[]") Reviewed by: olce, kevans Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D59051 --- sys/sys/ucred.h | 2 +- tests/sys/mac/do/Makefile | 2 ++ tests/sys/mac/do/regression.c | 83 +++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 86 insertions(+), 1 deletion(-) diff --git a/sys/sys/ucred.h b/sys/sys/ucred.h index 4bf48a5e4b87..19b45a5541a7 100644 --- a/sys/sys/ucred.h +++ b/sys/sys/ucred.h @@ -267,7 +267,7 @@ bool cr_xids_subset(struct ucred *active_cred, struct ucred *obj_cred); static inline bool group_is_primary(const gid_t gid, const struct ucred *const cred) { - return (gid == cred->cr_groups[0] || gid == cred->cr_rgid || + return (gid == cred->cr_gid || gid == cred->cr_rgid || gid == cred->cr_svgid); } bool group_is_supplementary(const gid_t gid, const struct ucred *const cred); diff --git a/tests/sys/mac/do/Makefile b/tests/sys/mac/do/Makefile index 0c40f65b65f6..0b88700c624c 100644 --- a/tests/sys/mac/do/Makefile +++ b/tests/sys/mac/do/Makefile @@ -2,6 +2,8 @@ PACKAGE= tests TESTSDIR= ${TESTSBASE}/sys/mac/do +ATF_TESTS_C= regression + ATF_TESTS_SH+= valid_configs invalid_configs consistency ${PACKAGE}FILES+= common.sh diff --git a/tests/sys/mac/do/regression.c b/tests/sys/mac/do/regression.c new file mode 100644 index 000000000000..bbf284803e4a --- /dev/null +++ b/tests/sys/mac/do/regression.c @@ -0,0 +1,83 @@ +/* + * Copyright (c) 2026 The FreeBSD Foundation + * + * This software was developed by Mark Johnston under sponsorship from + * the FreeBSD Foundation. + * + * SPDX-License-Identifier: BSD-2-Clause + */ + +#include +#include + +#include +#include +#include +#include +#include +#include +#include + +#include + +/* + * Regression test for a bug which erroneously allowed the setcred() call below. + */ +ATF_TC(empty_supplementary_group_list); +ATF_TC_HEAD(empty_supplementary_group_list, tc) +{ + atf_tc_set_md_var(tc, "require.user", "root"); +} +ATF_TC_BODY(empty_supplementary_group_list, tc) +{ + struct setcred cred = SETCRED_INITIALIZER; + struct passwd *passwd; + const char *user; + char path[PATH_MAX], *progname, *rule; + int flags; + + if (!atf_tc_has_config_var(tc, "unprivileged_user")) + atf_tc_skip("unprivileged_user not set"); + + user = atf_tc_get_config_var(tc, "unprivileged_user"); + passwd = getpwnam(user); + ATF_REQUIRE(passwd != NULL); + ATF_REQUIRE_MSG(passwd->pw_uid != 0, + "unprivileged user must not be root"); + ATF_REQUIRE_MSG(passwd->pw_gid != 0, + "unprivileged user group must not be wheel"); + + (void)asprintf(&rule, "uid=%d>uid=%d;gid=0>uid=0", + passwd->pw_uid, passwd->pw_uid + 1); + ATF_REQUIRE(sysctlbyname("security.mac.do.rules", + NULL, NULL, rule, strlen(rule)) == 0); + + progname = basename(strdup(getprogname())); + (void)snprintf(path, sizeof(path), "%s/%s", + atf_tc_get_config_var(tc, "srcdir"), progname); + ATF_REQUIRE(sysctlbyname("security.mac.do.exec_paths", + NULL, NULL, path, strlen(path)) == 0); + + ATF_REQUIRE(setgroups(0, NULL) == 0); + ATF_REQUIRE(setgid(passwd->pw_gid) == 0); + ATF_REQUIRE(setuid(passwd->pw_uid) == 0); + + /* + * Request the UID transition permitted by the first rule while also + * setting all primary GIDs to 0. MAC/do must reject this because GID 0 + * is not a primary GID of the current credential. + */ + cred.sc_uid = cred.sc_ruid = cred.sc_svuid = passwd->pw_uid + 1; + cred.sc_gid = cred.sc_rgid = cred.sc_svgid = 0; + flags = SETCREDF_UID | SETCREDF_RUID | SETCREDF_SVUID | + SETCREDF_GID | SETCREDF_RGID | SETCREDF_SVGID; + ATF_REQUIRE_ERRNO(EPERM, + setcred(flags, &cred, sizeof(cred)) == -1); +} + +ATF_TP_ADD_TCS(tp) +{ + ATF_TP_ADD_TC(tp, empty_supplementary_group_list); + + return (atf_no_error()); +}