Add CBS_dup() to initialize a new CBS with the same values.

This is useful for when you need to check the data ahead and then continue
on from the same spot.

input + ok jsing@ miod@

2 files changed, 14 insertions, 2 deletions

diff --git a/lib/libssl/bs_cbs.c b/lib/libssl/bs_cbs.c
index 45c253cc4b4..81731772496 100644
--- a/lib/libssl/bs_cbs.c
+++ b/lib/libssl/bs_cbs.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: bs_cbs.c,v 1.13 2015/06/17 07:25:56 doug Exp $	*/
+/*	$OpenBSD: bs_cbs.c,v 1.14 2015/06/19 00:23:36 doug Exp $	*/
 /*
  * Copyright (c) 2014, Google Inc.
  *
@@ -32,6 +32,12 @@ CBS_init(CBS *cbs, const uint8_t *data, size_t len)
 	cbs->len = len;
 }
 
+void
+CBS_dup(const CBS *cbs, CBS *out)
+{
+	CBS_init(out, CBS_data(cbs), CBS_len(cbs));
+}
+
 static int
 cbs_get(CBS *cbs, const uint8_t **p, size_t n)
 {
diff --git a/lib/libssl/bytestring.h b/lib/libssl/bytestring.h
index 4c9d4d88847..8ea84005b49 100644
--- a/lib/libssl/bytestring.h
+++ b/lib/libssl/bytestring.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: bytestring.h,v 1.13 2015/06/18 23:25:07 doug Exp $	*/
+/*	$OpenBSD: bytestring.h,v 1.14 2015/06/19 00:23:36 doug Exp $	*/
 /*
  * Copyright (c) 2014, Google Inc.
  *
@@ -466,6 +466,12 @@ int CBB_add_asn1_uint64(CBB *cbb, uint64_t value);
 
 #ifdef LIBRESSL_INTERNAL
 /*
+ * CBS_dup sets |out| to point to cbs's |data| and |len|.  It results in two
+ * CBS that point to the same buffer.
+ */
+void CBS_dup(const CBS *cbs, CBS *out);
+
+/*
  * cbs_get_any_asn1_element sets |*out| to contain the next ASN.1 element from
  * |*cbs| (including header bytes) and advances |*cbs|. It sets |*out_tag| to
  * the tag number and |*out_header_len| to the length of the ASN.1 header. If