Convert the DTLS header creation code to CBB.

Also consolidate it into the one place, since there is no reason to write
the epoch and sequence out later.

ok inoguchi@ tb@

1 files changed, 27 insertions, 20 deletions

diff --git a/src/lib/libssl/d1_pkt.c b/src/lib/libssl/d1_pkt.c
index 5558c0e872..2cb2d089c8 100644
--- a/src/lib/libssl/d1_pkt.c
+++ b/src/lib/libssl/d1_pkt.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: d1_pkt.c,v 1.68 2020/02/21 16:13:16 jsing Exp $ */
+/* $OpenBSD: d1_pkt.c,v 1.69 2020/02/21 16:15:56 jsing Exp $ */
 /*
  * DTLS implementation written by Nagendra Modadugu
  * (nagendra@cs.stanford.edu) for the OpenSSL project 2005.
@@ -1178,12 +1178,15 @@ dtls1_write_bytes(SSL *s, int type, const void *buf, int len)
 int
 do_dtls1_write(SSL *s, int type, const unsigned char *buf, unsigned int len)
 {
-        unsigned char *p, *pseq;
+        unsigned char *p;
         int i, mac_size, clear = 0;
         SSL3_RECORD *wr;
         SSL3_BUFFER *wb;
         SSL_SESSION *sess;
         int bs;
+        CBB cbb;
+
+        memset(&cbb, 0, sizeof(cbb));
 
         /* first check if there is a SSL3_BUFFER still being written
          * out.  This will happen with non blocking IO */
@@ -1223,18 +1226,20 @@ do_dtls1_write(SSL *s, int type, const unsigned char *buf, unsigned int len)
 
         p = wb->buf;
 
-        /* write the header */
-
-        *(p++) = type&0xff;
-        wr->type = type;
-
-        *(p++) = (s->version >> 8);
-        *(p++) = s->version&0xff;
+        if (!CBB_init_fixed(&cbb, p, DTLS1_RT_HEADER_LENGTH))
+                goto err;
 
-        /* field where we are to write out packet epoch, seq num and len */
-        pseq = p;
+        /* Write the header. */
+        if (!CBB_add_u8(&cbb, type))
+                goto err;
+        if (!CBB_add_u16(&cbb, s->version))
+                goto err;
+        if (!CBB_add_u16(&cbb, D1I(s)->w_epoch))
+                goto err;
+        if (!CBB_add_bytes(&cbb, &(S3I(s)->write_sequence[2]), 6))
+                goto err;
 
-        p += 10;
+        p += DTLS1_RT_HEADER_LENGTH;
 
         /* lets setup the record stuff. */
 
@@ -1247,6 +1252,7 @@ do_dtls1_write(SSL *s, int type, const unsigned char *buf, unsigned int len)
         else
                 bs = 0;
 
+        wr->type = type;
         wr->data = p + bs;
         /* make room for IV in case of CBC */
         wr->length = (int)len;
@@ -1283,17 +1289,15 @@ do_dtls1_write(SSL *s, int type, const unsigned char *buf, unsigned int len)
         /* ssl3_enc can only have an error on read */
         s->method->internal->ssl3_enc->enc(s, 1);
 
-        s2n(D1I(s)->w_epoch, pseq);
-        memcpy(pseq, &(S3I(s)->write_sequence[2]), 6);
-        pseq += 6;
-
-        /* record length after mac and block padding */
-        s2n(wr->length, pseq);
+        if (!CBB_add_u16(&cbb, wr->length))
+                goto err;
+        if (!CBB_finish(&cbb, NULL, NULL))
+                goto err;
 
         /* we should now have
          * wr->data pointing to the encrypted data, which is
          * wr->length long */
-        wr->type=type; /* not needed but helps for debugging */
+        wr->type = type; /* not needed but helps for debugging */
         wr->length += DTLS1_RT_HEADER_LENGTH;
 
         tls1_record_sequence_increment(S3I(s)->write_sequence);
@@ -1310,7 +1314,10 @@ do_dtls1_write(SSL *s, int type, const unsigned char *buf, unsigned int len)
 
         /* we now just need to write the buffer */
         return ssl3_write_pending(s, type, buf, len);
-err:
+
+ err:
+        CBB_cleanup(&cbb);
+
         return -1;
 }