ktls_ocf: Reject encrypted TLS records using AEAD that are too small.

If a TLS record is too small to contain the required explicit IV,
record_type (TLS 1.3), and MAC, reject attempts to decrypt it with
EMSGSIZE without submitting it to OCF.  OCF drivers may not properly
detect that regions in the crypto request are outside the bounds of
the mbuf chain.  The caller isn't supposed to submit such requests.

Reviewed by:	markj
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D37372

1 files changed, 28 insertions, 9 deletions

diff --git a/sys/opencrypto/ktls_ocf.c b/sys/opencrypto/ktls_ocf.c
index 938133fa451a..25d50adba5ca 100644
--- a/sys/opencrypto/ktls_ocf.c
+++ b/sys/opencrypto/ktls_ocf.c
@@ -638,10 +638,16 @@ ktls_ocf_tls12_aead_decrypt(struct ktls_session *tls,
 	struct cryptop crp;
 	struct ktls_ocf_session *os;
 	int error;
-	uint16_t tls_comp_len;
+	uint16_t tls_comp_len, tls_len;
 
 	os = tls->ocf_session;
 
+	/* Ensure record contains at least an explicit IV and tag. */
+	tls_len = ntohs(hdr->tls_length);
+	if (tls_len + sizeof(*hdr) < tls->params.tls_hlen +
+	    tls->params.tls_tlen)
+		return (EMSGSIZE);
+
 	crypto_initreq(&crp, os->sid);
 
 	/* Setup the IV. */
@@ -661,10 +667,10 @@ ktls_ocf_tls12_aead_decrypt(struct ktls_session *tls,
 
 	/* Setup the AAD. */
 	if (tls->params.cipher_algorithm == CRYPTO_AES_NIST_GCM_16)
-		tls_comp_len = ntohs(hdr->tls_length) -
+		tls_comp_len = tls_len -
 		    (AES_GMAC_HASH_LEN + sizeof(uint64_t));
 	else
-		tls_comp_len = ntohs(hdr->tls_length) - POLY1305_HASH_LEN;
+		tls_comp_len = tls_len - POLY1305_HASH_LEN;
 	ad.seq = htobe64(seqno);
 	ad.type = hdr->tls_type;
 	ad.tls_vmajor = hdr->tls_vmajor;
@@ -730,9 +736,15 @@ ktls_ocf_tls12_aead_recrypt(struct ktls_session *tls,
 	char *buf;
 	u_int payload_len;
 	int error;
+	uint16_t tls_len;
 
 	os = tls->ocf_session;
 
+	/* Ensure record contains at least an explicit IV and tag. */
+	tls_len = ntohs(hdr->tls_length);
+	if (tls_len < sizeof(uint64_t) + AES_GMAC_HASH_LEN)
+		return (EMSGSIZE);
+
 	crypto_initreq(&crp, os->recrypt_sid);
 
 	KASSERT(tls->params.cipher_algorithm == CRYPTO_AES_NIST_GCM_16,
@@ -743,8 +755,7 @@ ktls_ocf_tls12_aead_recrypt(struct ktls_session *tls,
 	memcpy(crp.crp_iv + TLS_AEAD_GCM_LEN, hdr + 1, sizeof(uint64_t));
 	be32enc(crp.crp_iv + AES_GCM_IV_LEN, 2);
 
-	payload_len = ntohs(hdr->tls_length) -
-	    (AES_GMAC_HASH_LEN + sizeof(uint64_t));
+	payload_len = tls_len - (AES_GMAC_HASH_LEN + sizeof(uint64_t));
 	crp.crp_op = CRYPTO_OP_ENCRYPT;
 	crp.crp_flags = CRYPTO_F_CBIMM | CRYPTO_F_IV_SEPARATE;
 	crypto_use_mbuf(&crp, m);
@@ -858,14 +869,16 @@ ktls_ocf_tls13_aead_decrypt(struct ktls_session *tls,
 	struct ktls_ocf_session *os;
 	int error;
 	u_int tag_len;
+	uint16_t tls_len;
 
 	os = tls->ocf_session;
 
 	tag_len = tls->params.tls_tlen - 1;
 
 	/* Payload must contain at least one byte for the record type. */
-	if (ntohs(hdr->tls_length) < tag_len + 1)
-		return (EBADMSG);
+	tls_len = ntohs(hdr->tls_length);
+	if (tls_len < tag_len + 1)
+		return (EMSGSIZE);
 
 	crypto_initreq(&crp, os->sid);
 
@@ -882,7 +895,7 @@ ktls_ocf_tls13_aead_decrypt(struct ktls_session *tls,
 	crp.crp_aad_length = sizeof(ad);
 
 	crp.crp_payload_start = tls->params.tls_hlen;
-	crp.crp_payload_length = ntohs(hdr->tls_length) - tag_len;
+	crp.crp_payload_length = tls_len - tag_len;
 	crp.crp_digest_start = crp.crp_payload_start + crp.crp_payload_length;
 
 	crp.crp_op = CRYPTO_OP_DECRYPT | CRYPTO_OP_VERIFY_DIGEST;
@@ -910,9 +923,15 @@ ktls_ocf_tls13_aead_recrypt(struct ktls_session *tls,
 	char *buf;
 	u_int payload_len;
 	int error;
+	uint16_t tls_len;
 
 	os = tls->ocf_session;
 
+	/* Payload must contain at least one byte for the record type. */
+	tls_len = ntohs(hdr->tls_length);
+	if (tls_len < AES_GMAC_HASH_LEN + 1)
+		return (EMSGSIZE);
+
 	crypto_initreq(&crp, os->recrypt_sid);
 
 	KASSERT(tls->params.cipher_algorithm == CRYPTO_AES_NIST_GCM_16,
@@ -923,7 +942,7 @@ ktls_ocf_tls13_aead_recrypt(struct ktls_session *tls,
 	*(uint64_t *)(crp.crp_iv + 4) ^= htobe64(seqno);
 	be32enc(crp.crp_iv + 12, 2);
 
-	payload_len = ntohs(hdr->tls_length) - AES_GMAC_HASH_LEN;
+	payload_len = tls_len - AES_GMAC_HASH_LEN;
 	crp.crp_op = CRYPTO_OP_ENCRYPT;
 	crp.crp_flags = CRYPTO_F_CBIMM | CRYPTO_F_IV_SEPARATE;
 	crypto_use_mbuf(&crp, m);