rxrpc: Handle temporary errors better in rxkad security

In the rxkad security module, when we encounter a temporary error (such as
ENOMEM) from which we could conceivably recover, don't abort the
connection, but rather permit retransmission of the relevant packets to
induce a retry.

Note that I'm leaving some places that could be merged together to insert
tracing in the next patch.

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

diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c
index 2d5838a3dc2415e96bddcfe8b91e6f5f8c34c36e..988903f1dc8082989151d9f293629fc8bf7a6174 100644 (file)
--- a/net/rxrpc/rxkad.c
+++ b/net/rxrpc/rxkad.c
@@ -759,16 +759,14 @@ static int rxkad_respond_to_challenge(struct rxrpc_connection *conn,
 
        _enter("{%d,%x}", conn->debug_id, key_serial(conn->params.key));
 
-       if (!conn->params.key) {
-               _leave(" = -EPROTO [no key]");
-               return -EPROTO;
-       }
+       abort_code = RX_PROTOCOL_ERROR;
+       if (!conn->params.key)
+               goto protocol_error;
 
+       abort_code = RXKADEXPIRED;
        ret = key_validate(conn->params.key);
-       if (ret < 0) {
-               *_abort_code = RXKADEXPIRED;
-               return ret;
-       }
+       if (ret < 0)
+               goto other_error;
 
        abort_code = RXKADPACKETSHORT;
        if (skb_copy_bits(skb, sizeof(struct rxrpc_wire_header),
@@ -787,8 +785,9 @@ static int rxkad_respond_to_challenge(struct rxrpc_connection *conn,
                goto protocol_error;
 
        abort_code = RXKADLEVELFAIL;
+       ret = -EACCES;
        if (conn->params.security_level < min_level)
-               goto protocol_error;
+               goto other_error;
 
        token = conn->params.key->payload.data[0];
 
@@ -815,9 +814,10 @@ static int rxkad_respond_to_challenge(struct rxrpc_connection *conn,
        return rxkad_send_response(conn, &sp->hdr, &resp, token->kad);
 
 protocol_error:
+       ret = -EPROTO;
+other_error:
        *_abort_code = abort_code;
-       _leave(" = -EPROTO [%d]", abort_code);
-       return -EPROTO;
+       return ret;
 }
 
 /*
@@ -848,10 +848,10 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
                switch (ret) {
                case -EKEYEXPIRED:
                        *_abort_code = RXKADEXPIRED;
-                       goto error;
+                       goto other_error;
                default:
                        *_abort_code = RXKADNOAUTH;
-                       goto error;
+                       goto other_error;
                }
        }
 
@@ -860,13 +860,11 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
 
        memcpy(&iv, &conn->server_key->payload.data[2], sizeof(iv));
 
+       ret = -ENOMEM;
        req = skcipher_request_alloc(conn->server_key->payload.data[0],
                                     GFP_NOFS);
-       if (!req) {
-               *_abort_code = RXKADNOAUTH;
-               ret = -ENOMEM;
-               goto error;
-       }
+       if (!req)
+               goto temporary_error;
 
        sg_init_one(&sg[0], ticket, ticket_len);
        skcipher_request_set_callback(req, 0, NULL, NULL);
@@ -943,13 +941,13 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
        if (issue > now) {
                *_abort_code = RXKADNOAUTH;
                ret = -EKEYREJECTED;
-               goto error;
+               goto other_error;
        }
 
        if (issue < now - life) {
                *_abort_code = RXKADEXPIRED;
                ret = -EKEYEXPIRED;
-               goto error;
+               goto other_error;
        }
 
        *_expiry = issue + life;
@@ -961,16 +959,15 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
        /* get the service instance name */
        name = Z(INST_SZ);
        _debug("KIV SINST: %s", name);
-
-       ret = 0;
-error:
-       _leave(" = %d", ret);
-       return ret;
+       return 0;
 
 bad_ticket:
        *_abort_code = RXKADBADTICKET;
-       ret = -EBADMSG;
-       goto error;
+       ret = -EPROTO;
+other_error:
+       return ret;
+temporary_error:
+       return ret;
 }
 
 /*
@@ -1054,9 +1051,10 @@ static int rxkad_verify_response(struct rxrpc_connection *conn,
                goto protocol_error;
 
        /* extract the kerberos ticket and decrypt and decode it */
+       ret = -ENOMEM;
        ticket = kmalloc(ticket_len, GFP_NOFS);
        if (!ticket)
-               return -ENOMEM;
+               goto temporary_error;
 
        abort_code = RXKADPACKETSHORT;
        if (skb_copy_bits(skb, sizeof(struct rxrpc_wire_header),
@@ -1064,12 +1062,9 @@ static int rxkad_verify_response(struct rxrpc_connection *conn,
                goto protocol_error_free;
 
        ret = rxkad_decrypt_ticket(conn, ticket, ticket_len, &session_key,
-                                  &expiry, &abort_code);
-       if (ret < 0) {
-               *_abort_code = abort_code;
-               kfree(ticket);
-               return ret;
-       }
+                                  &expiry, _abort_code);
+       if (ret < 0)
+               goto temporary_error_free;
 
        /* use the session key from inside the ticket to decrypt the
         * response */
@@ -1123,10 +1118,8 @@ static int rxkad_verify_response(struct rxrpc_connection *conn,
         * this the connection security can be handled in exactly the same way
         * as for a client connection */
        ret = rxrpc_get_server_data_key(conn, &session_key, expiry, kvno);
-       if (ret < 0) {
-               kfree(ticket);
-               return ret;
-       }
+       if (ret < 0)
+               goto temporary_error_free;
 
        kfree(ticket);
        _leave(" = 0");
@@ -1140,6 +1133,15 @@ protocol_error:
        *_abort_code = abort_code;
        _leave(" = -EPROTO [%d]", abort_code);
        return -EPROTO;
+
+temporary_error_free:
+       kfree(ticket);
+temporary_error:
+       /* Ignore the response packet if we got a temporary error such as
+        * ENOMEM.  We just want to send the challenge again.  Note that we
+        * also come out this way if the ticket decryption fails.
+        */
+       return ret;
 }
 
 /*