rxrpc: Don't leak the service-side session key to userspace

Don't let someone reading a service-side rxrpc-type key get access to the
session key that was exchanged with the client.  The server application
will, at some point, need to be able to read the information in the ticket,
but this probably shouldn't include the key material.

Signed-off-by: David Howells <dhowells@redhat.com>

diff --git a/include/keys/rxrpc-type.h b/include/keys/rxrpc-type.h
index 8e4ced9..333c0f4 100644 (file)
--- a/include/keys/rxrpc-type.h
+++ b/include/keys/rxrpc-type.h
@@ -36,6 +36,7 @@ struct rxkad_key {
  */
 struct rxrpc_key_token {
        u16     security_index;         /* RxRPC header security index */
+       bool    no_leak_key;            /* Don't copy the key to userspace */
        struct rxrpc_key_token *next;   /* the next token in the list */
        union {
                struct rxkad_key *kad;

diff --git a/net/rxrpc/key.c b/net/rxrpc/key.c
index 3bd7b9d..ed29ec0 100644 (file)
--- a/net/rxrpc/key.c
+++ b/net/rxrpc/key.c
@@ -579,7 +579,8 @@ static long rxrpc_read(const struct key *key,
                case RXRPC_SECURITY_RXKAD:
                        toksize += 8 * 4;       /* viceid, kvno, key*2, begin,
                                                 * end, primary, tktlen */
-                       toksize += RND(token->kad->ticket_len);
+                       if (!token->no_leak_key)
+                               toksize += RND(token->kad->ticket_len);
                        break;
 
                default: /* we have a ticket we can't encode */
@@ -654,7 +655,10 @@ static long rxrpc_read(const struct key *key,
                        ENCODE(token->kad->start);
                        ENCODE(token->kad->expiry);
                        ENCODE(token->kad->primary_flag);
-                       ENCODE_DATA(token->kad->ticket_len, token->kad->ticket);
+                       if (token->no_leak_key)
+                               ENCODE(0);
+                       else
+                               ENCODE_DATA(token->kad->ticket_len, token->kad->ticket);
                        break;
 
                default: