[PATCH 6.12 65/70] rxrpc: reject undecryptable rxkad response tickets

Greg Kroah-Hartman
2026-04-13T16:13:12Z

From: Yuqi Xu <xuyuqiabc@gmail.com>

commit fe4447cd95623b1cfacc15f280aab73a6d7340b2 upstream.

rxkad_decrypt_ticket() decrypts the RXKAD response ticket and then
parses the buffer as plaintext without checking whether
crypto_skcipher_decrypt() succeeded.

A malformed RESPONSE can therefore use a non-block-aligned ticket
length, make the decrypt operation fail, and still drive the ticket
parser with attacker-controlled bytes.

Check the decrypt result and abort the connection with RXKADBADTICKET
when ticket decryption fails.

Fixes: 17926a79320a ("[AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both")
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Co-developed-by: Yuan Tan <yuantan098@gmail.com>
Signed-off-by: Yuan Tan <yuantan098@gmail.com>
Suggested-by: Xin Liu <bird@lzu.edu.cn>
Tested-by: Ren Wei <enjou1224z@gmail.com>
Signed-off-by: Yuqi Xu <xuyuqiabc@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: stable@kernel.org
Link: https://patch.msgid.link/20260408121252.2249051-12-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/rxrpc/rxkad.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/net/rxrpc/rxkad.c
+++ b/net/rxrpc/rxkad.c
@@ -870,6 +870,7 @@ static int rxkad_decrypt_ticket(struct r
struct in_addr addr;
unsigned int life;
time64_t issue, now;
+ int ret;
bool little_endian;
u8 *p, *q, *name, *end;

@@ -889,8 +890,11 @@ static int rxkad_decrypt_ticket(struct r
sg_init_one(&sg[0], ticket, ticket_len);
skcipher_request_set_callback(req, 0, NULL, NULL);
skcipher_request_set_crypt(req, sg, sg, ticket_len, iv.x);
- crypto_skcipher_decrypt(req);
+ ret = crypto_skcipher_decrypt(req);
skcipher_request_free(req);
+ if (ret < 0)
+ return rxrpc_abort_conn(conn, skb, RXKADBADTICKET, -EPROTO,
+ rxkad_abort_resp_tkt_short);

p = ticket;
end = p + ticket_len;