CVE-2021-43267: Improper Validation of Specified Quantity in Input (CWE-1284)
value: An issue was discovered in net/tipc/crypto.c in the Linux kernel before 5.14.16. The Transparent Inter-Process Communication (TIPC) functionality allows remote attackers to exploit insufficient validation of user-supplied sizes for the MSG_CRYPTO message type.
CWE description: The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.
CVSS v3 base score: 9.8
Published: 2021-11-02T23:15Z
Repository: https://github.com/torvalds/linux
Language: C
Files changed: net/tipc/crypto.c
Commit date: 2021-10-26 13:43:07 +0100
Commit message: tipc: fix size validations for the MSG_CRYPTO type

The function tipc_crypto_key_rcv is used to parse MSG_CRYPTO messages
to receive keys from other nodes in the cluster in order to decrypt any
further messages from them.
This patch verifies that any supplied sizes in the message body are
valid for the received message.

Fixes: 1ef6f7c9390f ("tipc: add automatic session key exchange")
Signed-off-by: Max VA <maxv@sentinelone.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Diff: diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
index c9391d38de85..dc60c32bb70d 100644
--- a/net/tipc/crypto.c
+++ b/net/tipc/crypto.c
@@ -2283,47 +2283,57 @@ static bool tipc_crypto_key_rcv(struct tipc_crypto *rx, struct tipc_msg *hdr)
 	struct tipc_crypto *tx = tipc_net(rx->net)->crypto_tx;
 	struct tipc_aead_key *skey = NULL;
 	u16 key_gen = msg_key_gen(hdr);
 	u16 size = msg_data_sz(hdr);
 	u8 *data = msg_data(hdr);
+	unsigned int keylen;
+
+	/* Verify whether the size can exist in the packet */
+	if (unlikely(size < sizeof(struct tipc_aead_key) + TIPC_AEAD_KEYLEN_MIN)) {
+		pr_debug("%s: message data size is too small\n", rx->name);
+		goto exit;
+	}
+
+	keylen = ntohl(*((__be32 *)(data + TIPC_AEAD_ALG_NAME)));
+
+	/* Verify the supplied size values */
+	if (unlikely(size != keylen + sizeof(struct tipc_aead_key) ||
+		     keylen > TIPC_AEAD_KEY_SIZE_MAX)) {
+		pr_debug("%s: invalid MSG_CRYPTO key size\n", rx->name);
+		goto exit;
+	}
 
 	spin_lock(&rx->lock);
 	if (unlikely(rx->skey || (key_gen == rx->key_gen && rx->key.keys))) {
 		pr_err("%s: key existed <%p>, gen %d vs %d\n", rx->name,
 		       rx->skey, key_gen, rx->key_gen);
-		goto exit;
+		goto exit_unlock;
 	}
 
 	/* Allocate memory for the key */
 	skey = kmalloc(size, GFP_ATOMIC);
 	if (unlikely(!skey)) {
 		pr_err("%s: unable to allocate memory for skey\n", rx->name);
-		goto exit;
+		goto exit_unlock;
 	}
 
 	/* Copy key from msg data */
-	skey->keylen = ntohl(*((__be32 *)(data + TIPC_AEAD_ALG_NAME)));
+	skey->keylen = keylen;
 	memcpy(skey->alg_name, data, TIPC_AEAD_ALG_NAME);
 	memcpy(skey->key, data + TIPC_AEAD_ALG_NAME + sizeof(__be32),
 	       skey->keylen);
 
-	/* Sanity check */
-	if (unlikely(size != tipc_aead_key_size(skey))) {
-		kfree(skey);
-		skey = NULL;
-		goto exit;
-	}
-
 	rx->key_gen = key_gen;
 	rx->skey_mode = msg_key_mode(hdr);
 	rx->skey = skey;
 	rx->nokey = 0;
 	mb(); /* for nokey flag */
 
-exit:
+exit_unlock:
 	spin_unlock(&rx->lock);
 
+exit:
 	/* Schedule the key attaching on this crypto */
 	if (likely(skey && queue_delayed_work(tx->wq, &rx->work, 0)))
 		return true;
 
 	return false;

Vulnerable code: 		goto exit;
		goto exit;
	skey->keylen = ntohl(*((__be32 *)(data + TIPC_AEAD_ALG_NAME)));
	/* Sanity check */
	if (unlikely(size != tipc_aead_key_size(skey))) {
		kfree(skey);
		skey = NULL;
		goto exit;
	}

exit:
Fixed code: 	unsigned int keylen;

	/* Verify whether the size can exist in the packet */
	if (unlikely(size < sizeof(struct tipc_aead_key) + TIPC_AEAD_KEYLEN_MIN)) {
		pr_debug("%s: message data size is too small\n", rx->name);
		goto exit;
	}

	keylen = ntohl(*((__be32 *)(data + TIPC_AEAD_ALG_NAME)));

	/* Verify the supplied size values */
	if (unlikely(size != keylen + sizeof(struct tipc_aead_key) ||
		     keylen > TIPC_AEAD_KEY_SIZE_MAX)) {
		pr_debug("%s: invalid MSG_CRYPTO key size\n", rx->name);
		goto exit;
	}
		goto exit_unlock;
		goto exit_unlock;
	skey->keylen = keylen;
exit_unlock:
exit: