Change dtls1_get_message_header() to take a CBS.

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

ok inoguchi@ tb@

3 files changed, 21 insertions, 22 deletions

diff --git a/src/lib/libssl/d1_both.c b/src/lib/libssl/d1_both.c
index 61dc47b4b7..4c014be6a9 100644
--- a/src/lib/libssl/d1_both.c
+++ b/src/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/src/lib/libssl/d1_pkt.c b/src/lib/libssl/d1_pkt.c
index 11e6d7f8f8..0b952cf5f3 100644
--- a/src/lib/libssl/d1_pkt.c
+++ b/src/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/src/lib/libssl/dtls_locl.h b/src/lib/libssl/dtls_locl.h
index 502b42dcdd..4cf8827ec3 100644
--- a/src/lib/libssl/dtls_locl.h
+++ b/src/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);