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@@ -536,7 +536,7 @@ int cap_convert_nscap(struct dentry *dentry, void **ivalue, size_t size)
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static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
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struct linux_binprm *bprm,
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bool *effective,
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- bool *has_cap)
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+ bool *has_fcap)
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{
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struct cred *new = bprm->cred;
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unsigned i;
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@@ -546,7 +546,7 @@ static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
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*effective = true;
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if (caps->magic_etc & VFS_CAP_REVISION_MASK)
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- *has_cap = true;
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+ *has_fcap = true;
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CAP_FOR_EACH_U32(i) {
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__u32 permitted = caps->permitted.cap[i];
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@@ -653,7 +653,7 @@ int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data
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* its xattrs and, if present, apply them to the proposed credentials being
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* constructed by execve().
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*/
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-static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)
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+static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_fcap)
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{
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int rc = 0;
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struct cpu_vfs_cap_data vcaps;
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@@ -684,7 +684,7 @@ static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_c
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goto out;
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}
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- rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
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+ rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
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if (rc == -EINVAL)
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printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
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__func__, rc, bprm->filename);
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@@ -696,6 +696,115 @@ out:
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return rc;
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}
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+static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
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+
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+static inline bool __is_real(kuid_t uid, struct cred *cred)
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+{ return uid_eq(cred->uid, uid); }
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+
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+static inline bool __is_eff(kuid_t uid, struct cred *cred)
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+{ return uid_eq(cred->euid, uid); }
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+
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+static inline bool __is_suid(kuid_t uid, struct cred *cred)
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+{ return !__is_real(uid, cred) && __is_eff(uid, cred); }
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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_fcap,
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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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+
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+ if (!root_privileged())
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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_fcap && __is_suid(root_uid, new)) {
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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 (__is_eff(root_uid, new) || __is_real(root_uid, new)) {
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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 (__is_eff(root_uid, new))
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+ *effective = true;
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+}
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+
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+#define __cap_gained(field, target, source) \
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+ !cap_issubset(target->cap_##field, source->cap_##field)
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+#define __cap_grew(target, source, cred) \
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+ !cap_issubset(cred->cap_##target, cred->cap_##source)
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+#define __cap_full(field, cred) \
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+ cap_issubset(CAP_FULL_SET, cred->cap_##field)
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+
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+static inline bool __is_setuid(struct cred *new, const struct cred *old)
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+{ return !uid_eq(new->euid, old->uid); }
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+
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+static inline bool __is_setgid(struct cred *new, const struct cred *old)
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+{ return !gid_eq(new->egid, old->gid); }
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+
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+/*
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+ * 1) Audit candidate if current->cap_effective is set
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+ *
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+ * We do not bother to audit if 3 things are true:
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+ * 1) cap_effective has all caps
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+ * 2) we became root *OR* are were already root
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+ * 3) root is supposed to have all caps (SECURE_NOROOT)
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+ * Since this is just a normal root execing a process.
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+ *
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+ * Number 1 above might fail if you don't have a full bset, but I think
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+ * that is interesting information to audit.
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+ *
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+ * A number of other conditions require logging:
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+ * 2) something prevented setuid root getting all caps
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+ * 3) non-setuid root gets fcaps
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+ * 4) non-setuid root gets ambient
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+ */
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+static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
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+ kuid_t root, bool has_fcap)
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+{
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+ bool ret = false;
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+
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+ if ((__cap_grew(effective, ambient, new) &&
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+ !(__cap_full(effective, new) &&
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+ (__is_eff(root, new) || __is_real(root, new)) &&
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+ root_privileged())) ||
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+ (root_privileged() &&
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+ __is_suid(root, new) &&
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+ !__cap_full(effective, new)) ||
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+ (!__is_setuid(new, old) &&
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+ ((has_fcap &&
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+ __cap_gained(permitted, new, old)) ||
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+ __cap_gained(ambient, new, old))))
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+
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+ ret = true;
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+
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+ return ret;
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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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* @bprm: The execution parameters, including the proposed creds
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@@ -708,61 +817,33 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
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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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- bool effective, has_cap = false, is_setid;
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+ bool effective = false, has_fcap = false, is_setid;
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int ret;
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kuid_t root_uid;
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if (WARN_ON(!cap_ambient_invariant_ok(old)))
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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_fcap);
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if (ret < 0)
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return ret;
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root_uid = make_kuid(new->user_ns, 0);
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- if (!issecure(SECURE_NOROOT)) {
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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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+ handle_privileged_root(bprm, has_fcap, &effective, root_uid);
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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_gained(permitted, new, old))
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bprm->per_clear |= PER_CLEAR_ON_SETID;
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-
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/* Don't let someone trace a set[ug]id/setpcap binary with the revised
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* credentials unless they have the appropriate permit.
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*
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* In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
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*/
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- is_setid = !uid_eq(new->euid, old->uid) || !gid_eq(new->egid, old->gid);
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+ is_setid = __is_setuid(new, old) || __is_setgid(new, old);
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- if ((is_setid ||
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- !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
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+ if ((is_setid || __cap_gained(permitted, new, old)) &&
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((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
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!ptracer_capable(current, new->user_ns))) {
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/* downgrade; they get no more than they had, and maybe less */
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@@ -779,7 +860,7 @@ skip:
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new->sgid = new->fsgid = new->egid;
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/* File caps or setid cancels ambient. */
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- if (has_cap || is_setid)
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+ if (has_fcap || is_setid)
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cap_clear(new->cap_ambient);
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/*
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@@ -800,26 +881,10 @@ skip:
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if (WARN_ON(!cap_ambient_invariant_ok(new)))
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return -EPERM;
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- /*
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- * Audit candidate if current->cap_effective is set
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- *
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- * We do not bother to audit if 3 things are true:
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- * 1) cap_effective has all caps
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- * 2) we are root
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- * 3) root is supposed to have all caps (SECURE_NOROOT)
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- * Since this is just a normal root execing a process.
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- *
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- * Number 1 above might fail if you don't have a full bset, but I think
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- * that is interesting information to audit.
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- */
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- if (!cap_issubset(new->cap_effective, new->cap_ambient)) {
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- if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
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- !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
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- issecure(SECURE_NOROOT)) {
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- ret = audit_log_bprm_fcaps(bprm, new, old);
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- if (ret < 0)
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- return ret;
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- }
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+ if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
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+ ret = audit_log_bprm_fcaps(bprm, new, old);
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+ if (ret < 0)
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+ return ret;
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}
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new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
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@@ -829,13 +894,11 @@ skip:
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/* Check for privilege-elevated exec. */
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bprm->cap_elevated = 0;
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- if (is_setid) {
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+ if (is_setid ||
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+ (!__is_real(root_uid, new) &&
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+ (effective ||
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+ __cap_grew(permitted, ambient, new))))
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bprm->cap_elevated = 1;
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- } else if (!uid_eq(new->uid, root_uid)) {
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- if (effective ||
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- !cap_issubset(new->cap_permitted, new->cap_ambient))
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- bprm->cap_elevated = 1;
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- }
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return 0;
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}
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