Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752002AbdGaXyY (ORCPT ); Mon, 31 Jul 2017 19:54:24 -0400 Received: from mail-pf0-f174.google.com ([209.85.192.174]:34244 "EHLO mail-pf0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751729AbdGaXvv (ORCPT ); Mon, 31 Jul 2017 19:51:51 -0400 From: Kees Cook To: Andrew Morton Cc: Kees Cook , Andy Lutomirski , David Howells , "Eric W. Biederman" , John Johansen , "Serge E. Hallyn" , Paul Moore , Stephen Smalley , Casey Schaufler , Tetsuo Handa , James Morris , Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 08/15] commoncap: Move cap_elevated calculation into bprm_set_creds Date: Mon, 31 Jul 2017 16:51:26 -0700 Message-Id: <1501545093-56634-9-git-send-email-keescook@chromium.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1501545093-56634-1-git-send-email-keescook@chromium.org> References: <1501545093-56634-1-git-send-email-keescook@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4043 Lines: 136 Instead of a separate function, open-code the cap_elevated test, which lets us entirely remove bprm->cap_effective (to use the local "effective" variable instead), and more accurately examine euid/egid changes via the existing local "is_setid". The following LTP tests were run to validate the changes: # ./runltp -f syscalls -s cap # ./runltp -f securebits # ./runltp -f cap_bounds # ./runltp -f filecaps All kernel selftests for capabilities and exec continue to pass as well. Cc: Andy Lutomirski Signed-off-by: Kees Cook Reviewed-by: James Morris Acked-by: Serge Hallyn --- include/linux/binfmts.h | 3 --- security/commoncap.c | 52 ++++++++++--------------------------------------- 2 files changed, 10 insertions(+), 45 deletions(-) diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index ebc4030fc6bb..b2c1563091e5 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -31,9 +31,6 @@ struct linux_binprm { * binfmt_script/misc). */ called_set_creds:1, - cap_effective:1;/* true if has elevated effective capabilities, - * false if not; except for init which inherits - * its parent's caps anyway */ /* * True if most recent call to the commoncaps bprm_set_creds * hook (due to multiple prepare_binprm() calls from the diff --git a/security/commoncap.c b/security/commoncap.c index abb6050c8083..d8e26fb9781d 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -285,15 +285,6 @@ int cap_capset(struct cred *new, return 0; } -/* - * Clear proposed capability sets for execve(). - */ -static inline void bprm_clear_caps(struct linux_binprm *bprm) -{ - cap_clear(bprm->cred->cap_permitted); - bprm->cap_effective = false; -} - /** * cap_inode_need_killpriv - Determine if inode change affects privileges * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV @@ -443,7 +434,7 @@ static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_c int rc = 0; struct cpu_vfs_cap_data vcaps; - bprm_clear_caps(bprm); + cap_clear(bprm->cred->cap_permitted); if (!file_caps_enabled) return 0; @@ -476,13 +467,11 @@ static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_c out: if (rc) - bprm_clear_caps(bprm); + cap_clear(bprm->cred->cap_permitted); return rc; } -static int is_secureexec(struct linux_binprm *bprm); - /** * cap_bprm_set_creds - Set up the proposed credentials for execve(). * @bprm: The execution parameters, including the proposed creds @@ -587,8 +576,6 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) if (WARN_ON(!cap_ambient_invariant_ok(new))) return -EPERM; - bprm->cap_effective = effective; - /* * Audit candidate if current->cap_effective is set * @@ -617,35 +604,16 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) return -EPERM; /* Check for privilege-elevated exec. */ - bprm->cap_elevated = is_secureexec(bprm); - - return 0; -} - -/** - * is_secureexec - Determine whether a secure execution is required - * @bprm: The execution parameters - * - * Determine whether a secure execution is required, return 1 if it is, and 0 - * if it is not. - * - * The credentials have been committed by this point, and so are no longer - * available through @bprm->cred. - */ -static int is_secureexec(struct linux_binprm *bprm) -{ - const struct cred *cred = bprm->cred; - kuid_t root_uid = make_kuid(cred->user_ns, 0); - - if (!uid_eq(cred->uid, root_uid)) { - if (bprm->cap_effective) - return 1; - if (!cap_issubset(cred->cap_permitted, cred->cap_ambient)) - return 1; + bprm->cap_elevated = 0; + if (is_setid) { + bprm->cap_elevated = 1; + } else if (!uid_eq(new->uid, root_uid)) { + if (effective || + !cap_issubset(new->cap_permitted, new->cap_ambient)) + bprm->cap_elevated = 1; } - return (!uid_eq(cred->euid, cred->uid) || - !gid_eq(cred->egid, cred->gid)); + return 0; } /** -- 2.7.4