[PATCH GHAK16 V5 01/10] capabilities: factor out cap_bprm_set_creds privileged root

Factor out the case of privileged root from the function cap_bprm_set_creds() to make the latter easier to read and analyse. Suggested-by: Serge Hallyn <serge(a)hallyn.com&gt; Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; Reviewed-by: Serge Hallyn <serge(a)hallyn.com&gt; Acked-by: James Morris <james.l.morris(a)oracle.com&gt; Acked-by: Kees Cook <keescook(a)chromium.org&gt; Okay-ished-by: Paul Moore <paul(a)paul-moore.com&gt; --- security/commoncap.c | 76 +++++++++++++++++++++++++++++++++------------------- 1 file changed, 48 insertions(+), 28 deletions(-) diff --git a/security/commoncap.c b/security/commoncap.c index c25e0d2..be9bca5 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -695,6 +695,52 @@ static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_c return rc; } +/* + * handle_privileged_root - Handle case of privileged root + * @bprm: The execution parameters, including the proposed creds + * @has_fcap: Are any file capabilities set? + * @effective: Do we have effective root privilege? + * @root_uid: This namespace' root UID WRT initial USER namespace + * + * Handle the case where root is privileged and hasn't been neutered by + * SECURE_NOROOT. If file capabilities are set, they won't be combined with + * set UID root and nothing is changed. If we are root, cap_permitted is + * updated. If we have become set UID root, the effective bit is set. + */ +static void handle_privileged_root(struct linux_binprm *bprm, bool has_cap, + bool *effective, kuid_t root_uid) +{ + const struct cred *old = current_cred(); + struct cred *new = bprm->cred; + + if (issecure(SECURE_NOROOT)) + return; + /* + * If the legacy file capability is set, then don't set privs + * for a setuid root binary run by a non-root user. Do set it + * for a root user just to cause least surprise to an admin. + */ + if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) { + warn_setuid_and_fcaps_mixed(bprm->filename); + return; + } + /* + * To support inheritance of root-permissions and suid-root + * executables under compatibility mode, we override the + * capability sets for the file. + */ + if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) { + /* pP' = (cap_bset & ~0) | (pI & ~0) */ + new->cap_permitted = cap_combine(old->cap_bset, + old->cap_inheritable); + } + /* + * If only the real uid is 0, we do not set the effective bit. + */ + if (uid_eq(new->euid, root_uid)) + *effective = true; +} + /** * cap_bprm_set_creds - Set up the proposed credentials for execve(). * @bprm: The execution parameters, including the proposed creds @@ -707,46 +753,20 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) { const struct cred *old = current_cred(); struct cred *new = bprm->cred; - bool effective, has_cap = false, is_setid; + bool effective = false, has_cap = false, is_setid; int ret; kuid_t root_uid; if (WARN_ON(!cap_ambient_invariant_ok(old))) return -EPERM; - effective = false; ret = get_file_caps(bprm, &effective, &has_cap); if (ret < 0) return ret; root_uid = make_kuid(new->user_ns, 0); - if (!issecure(SECURE_NOROOT)) { - /* - * If the legacy file capability is set, then don't set privs - * for a setuid root binary run by a non-root user. Do set it - * for a root user just to cause least surprise to an admin. - */ - if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) { - warn_setuid_and_fcaps_mixed(bprm->filename); - goto skip; - } - /* - * To support inheritance of root-permissions and suid-root - * executables under compatibility mode, we override the - * capability sets for the file. - * - * If only the real uid is 0, we do not set the effective bit. - */ - if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) { - /* pP' = (cap_bset & ~0) | (pI & ~0) */ - new->cap_permitted = cap_combine(old->cap_bset, - old->cap_inheritable); - } - if (uid_eq(new->euid, root_uid)) - effective = true; - } -skip: + handle_privileged_root(bprm, has_cap, &effective, root_uid); /* if we have fs caps, clear dangerous personality flags */ if (!cap_issubset(new->cap_permitted, old->cap_permitted)) -- 1.8.3.1