From: jsing <jsing@openbsd.org>
Date: Sat, 4 Sep 2021 14:24:28 +0000 (+0000)
Subject: Change dtls1_get_message_header() to take a CBS.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=ab5ddd1b3fb2d9af1be6366202432c66048d8b28;p=openbsd

Change dtls1_get_message_header() to take a CBS.

The callers know the actual length and can initialise a CBS correctly.

ok inoguchi@ tb@
---

diff --git a/lib/libssl/d1_both.c b/lib/libssl/d1_both.c
index 61dc47b4b74..4c014be6a9f 100644
--- a/lib/libssl/d1_both.c
+++ b/lib/libssl/d1_both.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: d1_both.c,v 1.77 2021/07/19 08:42:24 jsing Exp $ */
+/* $OpenBSD: d1_both.c,v 1.78 2021/09/04 14:24:28 jsing Exp $ */
 /*
  * DTLS implementation written by Nagendra Modadugu
  * (nagendra@cs.stanford.edu) for the OpenSSL project 2005.
@@ -744,8 +744,9 @@ dtls1_get_message_fragment(SSL *s, int st1, int stn, long max, int *ok)
 {
 	unsigned char wire[DTLS1_HM_HEADER_LENGTH];
 	unsigned long len, frag_off, frag_len;
-	int i, al;
 	struct hm_header_st msg_hdr;
+	int i, al;
+	CBS cbs;
 
  again:
 	/* see if we have the required fragment already */
@@ -758,16 +759,16 @@ dtls1_get_message_fragment(SSL *s, int st1, int stn, long max, int *ok)
 	/* read handshake message header */
 	i = s->method->ssl_read_bytes(s, SSL3_RT_HANDSHAKE, wire,
 	    DTLS1_HM_HEADER_LENGTH, 0);
-	if (i <= 0) 	/* nbio, or an error */
-	{
+	if (i <= 0) {
+	 	/* nbio, or an error */
 		s->internal->rwstate = SSL_READING;
 		*ok = 0;
 		return i;
 	}
-	/* Handshake fails if message header is incomplete */
-	if (i != DTLS1_HM_HEADER_LENGTH ||
-	    /* parse the message fragment header */
-	    dtls1_get_message_header(wire, &msg_hdr) == 0) {
+
+	CBS_init(&cbs, wire, i);
+	if (!dtls1_get_message_header(&cbs, &msg_hdr)) {
+		/* Handshake fails if message header is incomplete. */
 		al = SSL_AD_UNEXPECTED_MESSAGE;
 		SSLerror(s, SSL_R_UNEXPECTED_MESSAGE);
 		goto fatal_err;
@@ -1172,26 +1173,23 @@ dtls1_guess_mtu(unsigned int curr_mtu)
 }
 
 int
-dtls1_get_message_header(unsigned char *data, struct hm_header_st *msg_hdr)
+dtls1_get_message_header(CBS *header, struct hm_header_st *msg_hdr)
 {
-	CBS header;
 	uint32_t msg_len, frag_off, frag_len;
 	uint16_t seq;
 	uint8_t type;
 
-	CBS_init(&header, data, sizeof(*msg_hdr));
-
 	memset(msg_hdr, 0, sizeof(*msg_hdr));
 
-	if (!CBS_get_u8(&header, &type))
+	if (!CBS_get_u8(header, &type))
 		return 0;
-	if (!CBS_get_u24(&header, &msg_len))
+	if (!CBS_get_u24(header, &msg_len))
 		return 0;
-	if (!CBS_get_u16(&header, &seq))
+	if (!CBS_get_u16(header, &seq))
 		return 0;
-	if (!CBS_get_u24(&header, &frag_off))
+	if (!CBS_get_u24(header, &frag_off))
 		return 0;
-	if (!CBS_get_u24(&header, &frag_len))
+	if (!CBS_get_u24(header, &frag_len))
 		return 0;
 
 	msg_hdr->type = type;
diff --git a/lib/libssl/d1_pkt.c b/lib/libssl/d1_pkt.c
index 11e6d7f8f86..0b952cf5f32 100644
--- a/lib/libssl/d1_pkt.c
+++ b/lib/libssl/d1_pkt.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: d1_pkt.c,v 1.110 2021/09/04 14:15:52 jsing Exp $ */
+/* $OpenBSD: d1_pkt.c,v 1.111 2021/09/04 14:24:28 jsing Exp $ */
 /*
  * DTLS implementation written by Nagendra Modadugu
  * (nagendra@cs.stanford.edu) for the OpenSSL project 2005.
@@ -807,9 +807,11 @@ dtls1_read_bytes(SSL *s, int type, unsigned char *buf, int len, int peek)
 	    rr->length >= DTLS1_HM_HEADER_LENGTH && rr->off == 0 &&
 	    !s->internal->in_handshake) {
 		struct hm_header_st msg_hdr;
+		CBS cbs;
 
 		/* this may just be a stale retransmit */
-		if (!dtls1_get_message_header(rr->data, &msg_hdr))
+		CBS_init(&cbs, rr->data, rr->length);
+		if (!dtls1_get_message_header(&cbs, &msg_hdr))
 			return -1;
 		if (rr->epoch != tls12_record_layer_read_epoch(s->internal->rl)) {
 			rr->length = 0;
diff --git a/lib/libssl/dtls_locl.h b/lib/libssl/dtls_locl.h
index 502b42dcdd8..4cf8827ec31 100644
--- a/lib/libssl/dtls_locl.h
+++ b/lib/libssl/dtls_locl.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: dtls_locl.h,v 1.6 2021/08/31 13:34:55 jsing Exp $ */
+/* $OpenBSD: dtls_locl.h,v 1.7 2021/09/04 14:24:28 jsing Exp $ */
 /*
  * DTLS implementation written by Nagendra Modadugu
  * (nagendra@cs.stanford.edu) for the OpenSSL project 2005.
@@ -206,8 +206,7 @@ int dtls1_retransmit_message(SSL *s, unsigned short seq,
 int dtls1_get_queue_priority(unsigned short seq, int is_ccs);
 int dtls1_retransmit_buffered_messages(SSL *s);
 void dtls1_clear_record_buffer(SSL *s);
-int dtls1_get_message_header(unsigned char *data,
-    struct hm_header_st *msg_hdr);
+int dtls1_get_message_header(CBS *header, struct hm_header_st *msg_hdr);
 void dtls1_reset_read_seq_numbers(SSL *s);
 struct timeval* dtls1_get_timeout(SSL *s, struct timeval* timeleft);
 int dtls1_check_timeout_num(SSL *s);