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>

2 files changed, 13 insertions, 6 deletions

diff --git a/Documentation/keys-request-key.txt b/Documentation/keys-request-key.txt
index 09b55e4..69686ad 100644
--- a/Documentation/keys-request-key.txt
+++ b/Documentation/keys-request-key.txt
@@ -127,14 +127,15 @@ This is because process A's keyrings can't simply be attached to
 of them, and (b) it requires the same UID/GID/Groups all the way through.
 
 
-======================
-NEGATIVE INSTANTIATION
-======================
+====================================
+NEGATIVE INSTANTIATION AND REJECTION
+====================================
 
 Rather than instantiating a key, it is possible for the possessor of an
 authorisation key to negatively instantiate a key that's under construction.
 This is a short duration placeholder that causes any attempt at re-requesting
-the key whilst it exists to fail with error ENOKEY.
+the key whilst it exists to fail with error ENOKEY if negated or the specified
+error if rejected.
 
 This is provided to prevent excessive repeated spawning of /sbin/request-key
 processes for a key that will never be obtainable.
diff --git a/Documentation/keys.txt b/Documentation/keys.txt
index cf68d1f..a6a97fd 100644
--- a/Documentation/keys.txt
+++ b/Documentation/keys.txt
@@ -657,6 +657,8 @@ The keyctl syscall functions are:
 
 	long keyctl(KEYCTL_NEGATE, key_serial_t key,
 		    unsigned timeout, key_serial_t keyring);
+	long keyctl(KEYCTL_REJECT, key_serial_t key,
+		    unsigned timeout, unsigned error, key_serial_t keyring);
 
      If the kernel calls back to userspace to complete the instantiation of a
      key, userspace should use this call mark the key as negative before the
@@ -669,6 +671,10 @@ The keyctl syscall functions are:
      that keyring, however all the constraints applying in KEYCTL_LINK apply in
      this case too.
 
+     If the key is rejected, future searches for it will return the specified
+     error code until the rejected key expires.  Negating the key is the same
+     as rejecting the key with ENOKEY as the error code.
+
 
  (*) Set the default request-key destination keyring.
 
@@ -1240,8 +1246,8 @@ example, the KDE desktop manager).
 The program (or whatever it calls) should finish construction of the key by
 calling KEYCTL_INSTANTIATE, which also permits it to cache the key in one of
 the keyrings (probably the session ring) before returning. Alternatively, the
-key can be marked as negative with KEYCTL_NEGATE; this also permits the key to
-be cached in one of the keyrings.
+key can be marked as negative with KEYCTL_NEGATE or KEYCTL_REJECT; this also
+permits the key to be cached in one of the keyrings.
 
 If it returns with the key remaining in the unconstructed state, the key will
 be marked as being negative, it will be added to the session keyring, and an