[PATCH 5.10 076/154] tipc: only accept encrypted MSG_CRYPTO msgs

[Greg Kroah-Hartman]

From: Xin Long <lucien.xin@xxxxxxxxx>

[ Upstream commit 271351d255b09e39c7f6437738cba595f9b235be ]

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: 1ef6f7c9390f ("tipc: add automatic session key exchange")
Acked-by: Ying Xue <ying.xue@xxxxxxxxxxxxx>
Acked-by: Jon Maloy <jmaloy@xxxxxxxxxx>
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/tipc/link.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/tipc/link.c b/net/tipc/link.c
index c92e6984933cb..29591955d08a5 100644
--- a/net/tipc/link.c
+++ b/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");
-- 
2.33.0