Use SSL3_HM_HEADER_LENGTH instead of the magic number 4.

ok beck@

Author: 4a6f656c

lib/libssl/ssl_both.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_both.c,v 1.34 2021/08/30 19:25:43 jsing Exp $ */
+/* $OpenBSD: ssl_both.c,v 1.35 2021/09/03 13:19:12 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -418,22 +418,22 @@ ssl3_get_message(SSL *s, int st1, int stn, int mt, long max, int *ok)
 goto fatal_err;
 }
 *ok = 1;
-s->internal->init_msg = s->internal->init_buf->data + 4;
+s->internal->init_msg = s->internal->init_buf->data +
+ SSL3_HM_HEADER_LENGTH;
 s->internal->init_num = (int)S3I(s)->hs.tls12.message_size;
 return s->internal->init_num;
 }
 
 p = (unsigned char *)s->internal->init_buf->data;
 
-/* s->internal->init_num < 4 */
 if (S3I(s)->hs.state == st1) {
 int skip_message;
 
 do {
-while (s->internal->init_num < 4) {
+while (s->internal->init_num < SSL3_HM_HEADER_LENGTH) {
 i = s->method->ssl_read_bytes(s,
  SSL3_RT_HANDSHAKE, &p[s->internal->init_num],
- 4 - s->internal->init_num, 0);
+ SSL3_HM_HEADER_LENGTH - s->internal->init_num, 0);
 if (i <= 0) {
 s->internal->rwstate = SSL_READING;
 *ok = 0;
@@ -455,20 +455,19 @@ ssl3_get_message(SSL *s, int st1, int stn, int mt, long max, int *ok)
 skip_message = 1;
 
 ssl_msg_callback(s, 0,
- SSL3_RT_HANDSHAKE, p, 4);
+ SSL3_RT_HANDSHAKE, p,
+ SSL3_HM_HEADER_LENGTH);
 }
 }
 } while (skip_message);
 
-/* s->internal->init_num == 4 */
-
 if ((mt >= 0) && (*p != mt)) {
 al = SSL_AD_UNEXPECTED_MESSAGE;
 SSLerror(s, SSL_R_UNEXPECTED_MESSAGE);
 goto fatal_err;
 }
 
-CBS_init(&cbs, p, 4);
+CBS_init(&cbs, p, SSL3_HM_HEADER_LENGTH);
 if (!CBS_get_u8(&cbs, &u8) ||
  !CBS_get_u24(&cbs, &l)) {
 SSLerror(s, ERR_R_BUF_LIB);
@@ -481,14 +480,16 @@ ssl3_get_message(SSL *s, int st1, int stn, int mt, long max, int *ok)
 SSLerror(s, SSL_R_EXCESSIVE_MESSAGE_SIZE);
 goto fatal_err;
 }
-if (l && !BUF_MEM_grow_clean(s->internal->init_buf, l + 4)) {
+if (l && !BUF_MEM_grow_clean(s->internal->init_buf,
+ l + SSL3_HM_HEADER_LENGTH)) {
 SSLerror(s, ERR_R_BUF_LIB);
 goto err;
 }
 S3I(s)->hs.tls12.message_size = l;
 S3I(s)->hs.state = stn;
 
-s->internal->init_msg = s->internal->init_buf->data + 4;
+s->internal->init_msg = s->internal->init_buf->data +
+ SSL3_HM_HEADER_LENGTH;
 s->internal->init_num = 0;
 }
 
@@ -510,11 +511,11 @@ ssl3_get_message(SSL *s, int st1, int stn, int mt, long max, int *ok)
 /* Feed this message into MAC computation. */
 if (s->internal->mac_packet) {
 tls1_transcript_record(s, (unsigned char *)s->internal->init_buf->data,
- s->internal->init_num + 4);
+ s->internal->init_num + SSL3_HM_HEADER_LENGTH);
 
 ssl_msg_callback(s, 0, SSL3_RT_HANDSHAKE,
  s->internal->init_buf->data,
- (size_t)s->internal->init_num + 4);
+ (size_t)s->internal->init_num + SSL3_HM_HEADER_LENGTH);
 }
 
 *ok = 1;