tipc: only accept encrypted MSG_CRYPTO msgs

stable inclusion
form stable-v5.10.82
commit 9c3c2ef6ca2618c64f925b28a9d31a0d1212cd15
bugzilla: 185877 https://gitee.com/openeuler/kernel/issues/I4QU6V

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9c3c2ef6ca2618c64f925b28a9d31a0d1212cd15

--------------------------------

[ Upstream commit 271351d2 ]

The MSG_CRYPTO msgs are always encrypted and sent to other nodes
for keys' deployment. But when receiving in peers, if those nodes
do not validate it and make sure it's encrypted, one could craft
a malicious MSG_CRYPTO msg to deploy its key with no need to know
other nodes' keys.

This patch is to do that by checking TIPC_SKB_CB(skb)->decrypted
and discard it if this packet never got decrypted.

Note that this is also a supplementary fix to CVE-2021-43267 that
can be triggered by an unencrypted malicious MSG_CRYPTO msg.

Fixes: 1ef6f7c9 ("tipc: add automatic session key exchange")
Acked-by: NYing Xue <ying.xue@windriver.com>
Acked-by: NJon Maloy <jmaloy@redhat.com>
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

net/tipc/link.c

@@ -1258,8 +1258,11 @@ static bool tipc_data_input(struct tipc_link *l, struct sk_buff *skb,
 		return false;
 #ifdef CONFIG_TIPC_CRYPTO
 	case MSG_CRYPTO:
-		tipc_crypto_msg_rcv(l->net, skb);
-		return true;
+		if (TIPC_SKB_CB(skb)->decrypted) {
+			tipc_crypto_msg_rcv(l->net, skb);
+			return true;
+		}
+		fallthrough;
 #endif
 	default:
 		pr_warn("Dropping received illegal msg type\n");