KEYS: Add a new keyctl op to reject a key with a specified error code

Add a new keyctl op to reject a key with a specified error code.  This works
much the same as negating a key, and so keyctl_negate_key() is made a special
case of keyctl_reject_key().  The difference is that keyctl_negate_key()
selects ENOKEY as the error to be reported.

Typically the key would be rejected with EKEYEXPIRED, EKEYREVOKED or
EKEYREJECTED, but this is not mandatory.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

6 files changed, 56 insertions, 13 deletions

diff --git a/security/keys/compat.c b/security/keys/compat.c
index 07a5f35e3970..17c99d0149ec 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -85,6 +85,9 @@ asmlinkage long compat_sys_keyctl(u32 option,
         case KEYCTL_SESSION_TO_PARENT:
                 return keyctl_session_to_parent();
 
+        case KEYCTL_REJECT:
+                return keyctl_reject_key(arg2, arg3, arg4, arg5);
+
         default:
                 return -EOPNOTSUPP;
         }
diff --git a/security/keys/internal.h b/security/keys/internal.h
index a52aa7c88b41..286c0959ee51 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -214,6 +214,7 @@ extern long keyctl_assume_authority(key_serial_t);
 extern long keyctl_get_security(key_serial_t keyid, char __user *buffer,
                                 size_t buflen);
 extern long keyctl_session_to_parent(void);
+extern long keyctl_reject_key(key_serial_t, unsigned, unsigned, key_serial_t);
 
 /*
  * Debugging key validation
diff --git a/security/keys/key.c b/security/keys/key.c
index 8e315ef2e88e..f7f9d93f08d9 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -511,26 +511,29 @@ int key_instantiate_and_link(struct key *key,
 EXPORT_SYMBOL(key_instantiate_and_link);
 
 /**
- * key_negate_and_link - Negatively instantiate a key and link it into the keyring.
+ * key_reject_and_link - Negatively instantiate a key and link it into the keyring.
  * @key: The key to instantiate.
  * @timeout: The timeout on the negative key.
+ * @error: The error to return when the key is hit.
  * @keyring: Keyring to create a link in on success (or NULL).
  * @authkey: The authorisation token permitting instantiation.
  *
  * Negatively instantiate a key that's in the uninstantiated state and, if
- * successful, set its timeout and link it in to the destination keyring if one
- * is supplied.  The key and any links to the key will be automatically garbage
- * collected after the timeout expires.
+ * successful, set its timeout and stored error and link it in to the
+ * destination keyring if one is supplied.  The key and any links to the key
+ * will be automatically garbage collected after the timeout expires.
  *
  * Negative keys are used to rate limit repeated request_key() calls by causing
- * them to return -ENOKEY until the negative key expires.
+ * them to return the stored error code (typically ENOKEY) until the negative
+ * key expires.
  *
  * If successful, 0 is returned, the authorisation token is revoked and anyone
  * waiting for the key is woken up.  If the key was already instantiated,
  * -EBUSY will be returned.
  */
-int key_negate_and_link(struct key *key,
+int key_reject_and_link(struct key *key,
                         unsigned timeout,
+                        unsigned error,
                         struct key *keyring,
                         struct key *authkey)
 {
@@ -556,6 +559,7 @@ int key_negate_and_link(struct key *key,
                 atomic_inc(&key->user->nikeys);
                 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
                 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
+                key->type_data.reject_error = -error;
                 now = current_kernel_time();
                 key->expiry = now.tv_sec + timeout;
                 key_schedule_gc(key->expiry + key_gc_delay);
@@ -585,8 +589,7 @@ int key_negate_and_link(struct key *key,
 
         return ret == 0 ? link_ret : ret;
 }
-
-EXPORT_SYMBOL(key_negate_and_link);
+EXPORT_SYMBOL(key_reject_and_link);
 
 /*
  * Garbage collect keys in process context so that we don't have to disable
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 31a0fd8189f1..0d7b1946ff94 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1013,12 +1013,42 @@ error:
  */
 long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
 {
+        return keyctl_reject_key(id, timeout, ENOKEY, ringid);
+}
+
+/*
+ * Negatively instantiate the key with the given timeout (in seconds) and error
+ * code and link the key into the destination keyring if one is given.
+ *
+ * The caller must have the appropriate instantiation permit set for this to
+ * work (see keyctl_assume_authority).  No other permissions are required.
+ *
+ * The key and any links to the key will be automatically garbage collected
+ * after the timeout expires.
+ *
+ * Negative keys are used to rate limit repeated request_key() calls by causing
+ * them to return the specified error code until the negative key expires.
+ *
+ * If successful, 0 will be returned.
+ */
+long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
+                       key_serial_t ringid)
+{
         const struct cred *cred = current_cred();
         struct request_key_auth *rka;
         struct key *instkey, *dest_keyring;
         long ret;
 
-        kenter("%d,%u,%d", id, timeout, ringid);
+        kenter("%d,%u,%u,%d", id, timeout, error, ringid);
+
+        /* must be a valid error code and mustn't be a kernel special */
+        if (error <= 0 ||
+            error >= MAX_ERRNO ||
+            error == ERESTARTSYS ||
+            error == ERESTARTNOINTR ||
+            error == ERESTARTNOHAND ||
+            error == ERESTART_RESTARTBLOCK)
+                return -EINVAL;
 
         /* the appropriate instantiation authorisation key must have been
          * assumed before calling this */
@@ -1038,7 +1068,7 @@ long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
                 goto error;
 
         /* instantiate the key and link it into a keyring */
-        ret = key_negate_and_link(rka->target_key, timeout,
+        ret = key_reject_and_link(rka->target_key, timeout, error,
                                   dest_keyring, instkey);
 
         key_put(dest_keyring);
@@ -1492,6 +1522,12 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
         case KEYCTL_SESSION_TO_PARENT:
                 return keyctl_session_to_parent();
 
+        case KEYCTL_REJECT:
+                return keyctl_reject_key((key_serial_t) arg2,
+                                         (unsigned) arg3,
+                                         (unsigned) arg4,
+                                         (key_serial_t) arg5);
+
         default:
                 return -EOPNOTSUPP;
         }
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 5620f084dede..cdd2f3f88c88 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -352,7 +352,7 @@ key_ref_t keyring_search_aux(key_ref_t keyring_ref,
                         goto error_2;
                 if (key->expiry && now.tv_sec >= key->expiry)
                         goto error_2;
-                key_ref = ERR_PTR(-ENOKEY);
+                key_ref = ERR_PTR(key->type_data.reject_error);
                 if (kflags & (1 << KEY_FLAG_NEGATIVE))
                         goto error_2;
                 goto found;
@@ -401,7 +401,7 @@ descend:
 
                 /* we set a different error code if we pass a negative key */
                 if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
-                        err = -ENOKEY;
+                        err = key->type_data.reject_error;
                         continue;
                 }
 
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index a3dc0d460def..df3c0417ee40 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -585,7 +585,7 @@ int wait_for_key_construction(struct key *key, bool intr)
         if (ret < 0)
                 return ret;
         if (test_bit(KEY_FLAG_NEGATIVE, &key->flags))
-                return -ENOKEY;
+                return key->type_data.reject_error;
         return key_validate(key);
 }
 EXPORT_SYMBOL(wait_for_key_construction);