Provide ssl3_packet_read() and ssl3_packet_extend() functions that improve

the awkward API provided by ssl3_read_n(). Call these when we need to
read or extend a packet.

ok beck@

3 files changed, 59 insertions, 35 deletions

diff --git a/lib/libssl/d1_pkt.c b/lib/libssl/d1_pkt.c
index f15b64364e8..19853d23756 100644
--- a/lib/libssl/d1_pkt.c
+++ b/lib/libssl/d1_pkt.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: d1_pkt.c,v 1.58 2017/01/23 14:35:42 jsing Exp $ */
+/* $OpenBSD: d1_pkt.c,v 1.59 2017/01/25 06:13:02 jsing Exp $ */
 /*
  * DTLS implementation written by Nagendra Modadugu
  * (nagendra@cs.stanford.edu) for the OpenSSL project 2005.
@@ -469,11 +469,11 @@ err:
 int
 dtls1_get_record(SSL *s)
 {
-	int i, n;
 	SSL3_RECORD *rr;
 	unsigned char *p = NULL;
 	DTLS1_BITMAP *bitmap;
 	unsigned int is_next_epoch;
+	int n;
 
 	rr = &(S3I(s)->rrec);
 
@@ -501,13 +501,12 @@ again:
 		uint16_t epoch, len, ssl_version;
 		uint8_t type;
 
-		n = ssl3_read_n(s, DTLS1_RT_HEADER_LENGTH, s->s3->rbuf.len, 0);
-		/* read timeout is handled by dtls1_read_bytes */
+		n = ssl3_packet_read(s, DTLS1_RT_HEADER_LENGTH);
 		if (n <= 0)
-			return(n); /* error or non-blocking */
+			return (n);
 
-		/* this packet contained a partial record, dump it */
-		if (s->internal->packet_length != DTLS1_RT_HEADER_LENGTH)
+		/* If this packet contained a partial record, dump it. */
+		if (n != DTLS1_RT_HEADER_LENGTH)
 			goto again;
 
 		s->internal->rstate = SSL_ST_READ_BODY;
@@ -553,20 +552,14 @@ again:
 
 	/* s->internal->rstate == SSL_ST_READ_BODY, get and decode the data */
 
-	if (rr->length > s->internal->packet_length - DTLS1_RT_HEADER_LENGTH) {
-		/* now s->internal->packet_length == DTLS1_RT_HEADER_LENGTH */
-		i = rr->length;
-		n = ssl3_read_n(s, i, i, 1);
-		if (n <= 0)
-			return(n); /* error or non-blocking io */
+	n = ssl3_packet_extend(s, DTLS1_RT_HEADER_LENGTH + rr->length);
+	if (n <= 0)
+		return (n);
 
-		/* this packet contained a partial record, dump it */
-		if (n != i)
-			goto again;
+	/* If this packet contained a partial record, dump it. */
+	if (n != DTLS1_RT_HEADER_LENGTH + rr->length)
+		goto again;
 
-		/* now n == rr->length,
-		 * and s->internal->packet_length == DTLS1_RT_HEADER_LENGTH + rr->length */
-	}
 	s->internal->rstate = SSL_ST_READ_HEADER; /* set state for later operations */
 
 	/* match epochs.  NULL means the packet is dropped on the floor */
diff --git a/lib/libssl/s3_pkt.c b/lib/libssl/s3_pkt.c
index a9737a7f400..152e384a4bd 100644
--- a/lib/libssl/s3_pkt.c
+++ b/lib/libssl/s3_pkt.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: s3_pkt.c,v 1.68 2017/01/23 14:35:42 jsing Exp $ */
+/* $OpenBSD: s3_pkt.c,v 1.69 2017/01/25 06:13:02 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -130,7 +130,7 @@ static int ssl3_get_record(SSL *s);
  * (If s->internal->read_ahead is set, 'max' bytes may be stored in rbuf
  * [plus s->internal->packet_length bytes if extend == 1].)
  */
-int
+static int
 ssl3_read_n(SSL *s, int n, int max, int extend)
 {
 	int i, len, left;
@@ -263,9 +263,42 @@ ssl3_read_n(SSL *s, int n, int max, int extend)
 	rb->left = left - n;
 	s->internal->packet_length += n;
 	s->internal->rwstate = SSL_NOTHING;
+
 	return (n);
 }
 
+int
+ssl3_packet_read(SSL *s, int plen)
+{
+	int n;
+
+	n = ssl3_read_n(s, plen, s->s3->rbuf.len, 0);
+	if (n <= 0)
+		return n;
+	if (s->internal->packet_length < plen)
+		return s->internal->packet_length;
+
+	return plen;
+}
+
+int
+ssl3_packet_extend(SSL *s, int plen)
+{
+	int rlen, n;
+
+	if (s->internal->packet_length >= plen)
+		return plen;
+	rlen = plen - s->internal->packet_length;
+
+	n = ssl3_read_n(s, rlen, rlen, 1);
+	if (n <= 0)
+		return n;
+	if (s->internal->packet_length < plen)
+		return s->internal->packet_length;
+
+	return plen;
+}
+
 /* Call this to get a new input record.
  * It will return <= 0 if more data is needed, normally due to an error
  * or non-blocking IO.
@@ -296,9 +329,10 @@ again:
 		uint16_t len, ssl_version;
 		uint8_t type;
 
-		n = ssl3_read_n(s, SSL3_RT_HEADER_LENGTH, s->s3->rbuf.len, 0);
+		n = ssl3_packet_read(s, SSL3_RT_HEADER_LENGTH);
 		if (n <= 0)
-			return(n); /* error or non-blocking */
+			return (n);
+
 		s->internal->rstate = SSL_ST_READ_BODY;
 
 		CBS_init(&header, s->internal->packet, n);
@@ -345,17 +379,13 @@ again:
 
 	/* s->internal->rstate == SSL_ST_READ_BODY, get and decode the data */
 
-	if (rr->length > s->internal->packet_length - SSL3_RT_HEADER_LENGTH) {
-		/* now s->internal->packet_length == SSL3_RT_HEADER_LENGTH */
-		i = rr->length;
-		n = ssl3_read_n(s, i, i, 1);
-		if (n <= 0)
-			return(n); /* error or non-blocking io */
-		/* now n == rr->length,
-		 * and s->internal->packet_length == SSL3_RT_HEADER_LENGTH + rr->length */
-	}
+	n = ssl3_packet_extend(s, SSL3_RT_HEADER_LENGTH + rr->length);
+	if (n <= 0)
+		return (n);
+	if (n != SSL3_RT_HEADER_LENGTH + rr->length)
+		return (n);
 
-	s->internal->rstate=SSL_ST_READ_HEADER; /* set state for later operations */
+	s->internal->rstate = SSL_ST_READ_HEADER; /* set state for later operations */
 
 	/* At this point, s->internal->packet_length == SSL3_RT_HEADER_LNGTH + rr->length,
 	 * and we have that many bytes in s->internal->packet
diff --git a/lib/libssl/ssl_locl.h b/lib/libssl/ssl_locl.h
index 0cda709da60..9cad2bc50d6 100644
--- a/lib/libssl/ssl_locl.h
+++ b/lib/libssl/ssl_locl.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_locl.h,v 1.164 2017/01/24 09:03:21 jsing Exp $ */
+/* $OpenBSD: ssl_locl.h,v 1.165 2017/01/25 06:13:02 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1198,7 +1198,8 @@ long ssl23_default_timeout(void);
 
 long tls1_default_timeout(void);
 int dtls1_do_write(SSL *s, int type);
-int ssl3_read_n(SSL *s, int n, int max, int extend);
+int ssl3_packet_read(SSL *s, int plen);
+int ssl3_packet_extend(SSL *s, int plen);
 int dtls1_read_bytes(SSL *s, int type, unsigned char *buf, int len, int peek);
 int ssl3_write_pending(SSL *s, int type, const unsigned char *buf,
     unsigned int len);