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