Provide the bytestring APIs for libcrypto internal use.

Bring a copy of the bytestring APIs (CBB/CBS) from libssl, for use in
libcrypto - these are not exposed publicly.

Discussed with beck@ and tb@

5 files changed, 1771 insertions, 3 deletions

diff --git a/lib/libcrypto/Makefile b/lib/libcrypto/Makefile
index 3f4014409d1..fba3871e73d 100644
--- a/lib/libcrypto/Makefile
+++ b/lib/libcrypto/Makefile
@@ -1,4 +1,4 @@
-# $OpenBSD: Makefile,v 1.49 2021/11/01 20:53:08 tb Exp $
+# $OpenBSD: Makefile,v 1.50 2021/11/20 18:10:52 jsing Exp $
 
 LIB=	crypto
 LIBREBUILD=y
@@ -28,8 +28,8 @@ CFLAGS+= -DDSO_DLFCN -DHAVE_DLFCN_H -DHAVE_FUNOPEN
 CFLAGS+= -DOPENSSL_NO_HW_PADLOCK # XXX enable this?
 
 CFLAGS+= -I${LCRYPTO_SRC}
-CFLAGS+= -I${LCRYPTO_SRC}/asn1 -I${LCRYPTO_SRC}/bn -I${LCRYPTO_SRC}/evp
-CFLAGS+= -I${LCRYPTO_SRC}/modes -I${LCRYPTO_SRC}/x509
+CFLAGS+= -I${LCRYPTO_SRC}/asn1 -I${LCRYPTO_SRC}/bn -I${LCRYPTO_SRC}/bytestring
+CFLAGS+= -I${LCRYPTO_SRC}/evp -I${LCRYPTO_SRC}/modes -I${LCRYPTO_SRC}/x509
 
 # XXX FIXME ecdsa and ec should be merged
 CFLAGS+= -I${LCRYPTO_SRC}/ecdsa
@@ -85,6 +85,9 @@ SRCS+= bn_depr.c bn_const.c bn_x931p.c
 # buffer/
 SRCS+= buffer.c buf_err.c buf_str.c
 
+# bytestring/
+SRCS+= bs_ber.c bs_cbb.c bs_cbs.c
+
 # camellia/
 SRCS+= cmll_cfb.c cmll_ctr.c cmll_ecb.c cmll_ofb.c
 
@@ -290,6 +293,7 @@ SRCS+= pcy_cache.c pcy_node.c pcy_data.c pcy_map.c pcy_tree.c pcy_lib.c
 	${LCRYPTO_SRC}/bn \
 	${LCRYPTO_SRC}/bn/asm \
 	${LCRYPTO_SRC}/buffer \
+	${LCRYPTO_SRC}/bytestring \
 	${LCRYPTO_SRC}/camellia \
 	${LCRYPTO_SRC}/cast \
 	${LCRYPTO_SRC}/chacha \
diff --git a/lib/libcrypto/bytestring/bs_ber.c b/lib/libcrypto/bytestring/bs_ber.c
new file mode 100644
index 00000000000..e77c98b2238
--- /dev/null
+++ b/lib/libcrypto/bytestring/bs_ber.c
@@ -0,0 +1,269 @@
+/*	$OpenBSD: bs_ber.c,v 1.1 2021/11/20 18:10:52 jsing Exp $	*/
+/*
+ * Copyright (c) 2014, Google Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <string.h>
+
+#include "bytestring.h"
+
+/*
+ * kMaxDepth is a just a sanity limit. The code should be such that the length
+ * of the input being processes always decreases. None the less, a very large
+ * input could otherwise cause the stack to overflow.
+ */
+static const unsigned int kMaxDepth = 2048;
+
+/* Non-strict version that allows a relaxed DER with indefinite form. */
+static int
+cbs_nonstrict_get_any_asn1_element(CBS *cbs, CBS *out, unsigned int *out_tag,
+    size_t *out_header_len)
+{
+	return cbs_get_any_asn1_element_internal(cbs, out,
+	    out_tag, out_header_len, 0);
+}
+
+/*
+ * cbs_find_indefinite walks an ASN.1 structure in |orig_in| and sets
+ * |*indefinite_found| depending on whether an indefinite length element was
+ * found. The value of |orig_in| is not modified.
+ *
+ * Returns one on success (i.e. |*indefinite_found| was set) and zero on error.
+ */
+static int
+cbs_find_indefinite(const CBS *orig_in, char *indefinite_found,
+    unsigned int depth)
+{
+	CBS in;
+
+	if (depth > kMaxDepth)
+		return 0;
+
+	CBS_init(&in, CBS_data(orig_in), CBS_len(orig_in));
+
+	while (CBS_len(&in) > 0) {
+		CBS contents;
+		unsigned int tag;
+		size_t header_len;
+
+		if (!cbs_nonstrict_get_any_asn1_element(&in, &contents, &tag,
+		    &header_len))
+			return 0;
+
+		/* Indefinite form not allowed by DER. */
+		if (CBS_len(&contents) == header_len && header_len > 0 &&
+		    CBS_data(&contents)[header_len - 1] == 0x80) {
+			*indefinite_found = 1;
+			return 1;
+		}
+		if (tag & CBS_ASN1_CONSTRUCTED) {
+			if (!CBS_skip(&contents, header_len) ||
+			    !cbs_find_indefinite(&contents, indefinite_found,
+			    depth + 1))
+				return 0;
+		}
+	}
+
+	*indefinite_found = 0;
+	return 1;
+}
+
+/*
+ * is_primitive_type returns true if |tag| likely a primitive type. Normally
+ * one can just test the "constructed" bit in the tag but, in BER, even
+ * primitive tags can have the constructed bit if they have indefinite
+ * length.
+ */
+static char
+is_primitive_type(unsigned int tag)
+{
+	return (tag & 0xc0) == 0 &&
+	    (tag & 0x1f) != (CBS_ASN1_SEQUENCE & 0x1f) &&
+	    (tag & 0x1f) != (CBS_ASN1_SET & 0x1f);
+}
+
+/*
+ * is_eoc returns true if |header_len| and |contents|, as returned by
+ * |cbs_nonstrict_get_any_asn1_element|, indicate an "end of contents" (EOC)
+ * value.
+ */
+static char
+is_eoc(size_t header_len, CBS *contents)
+{
+	const unsigned char eoc[] = {0x0, 0x0};
+
+	return header_len == 2 && CBS_mem_equal(contents, eoc, 2);
+}
+
+/*
+ * cbs_convert_indefinite reads data with DER encoding (but relaxed to allow
+ * indefinite form) from |in| and writes definite form DER data to |out|. If
+ * |squash_header| is set then the top-level of elements from |in| will not
+ * have their headers written. This is used when concatenating the fragments of
+ * an indefinite length, primitive value. If |looking_for_eoc| is set then any
+ * EOC elements found will cause the function to return after consuming it.
+ * It returns one on success and zero on error.
+ */
+static int
+cbs_convert_indefinite(CBS *in, CBB *out, char squash_header,
+    char looking_for_eoc, unsigned int depth)
+{
+	if (depth > kMaxDepth)
+		return 0;
+
+	while (CBS_len(in) > 0) {
+		CBS contents;
+		unsigned int tag;
+		size_t header_len;
+		CBB *out_contents, out_contents_storage;
+
+		if (!cbs_nonstrict_get_any_asn1_element(in, &contents, &tag,
+		    &header_len))
+			return 0;
+
+		out_contents = out;
+
+		if (CBS_len(&contents) == header_len) {
+			if (is_eoc(header_len, &contents))
+				return looking_for_eoc;
+
+			if (header_len > 0 &&
+			    CBS_data(&contents)[header_len - 1] == 0x80) {
+				/*
+				 * This is an indefinite length element. If
+				 * it's a SEQUENCE or SET then we just need to
+				 * write the out the contents as normal, but
+				 * with a concrete length prefix.
+				 *
+				 * If it's a something else then the contents
+				 * will be a series of DER elements of the same
+				 * type which need to be concatenated.
+				 */
+				const char context_specific = (tag & 0xc0)
+				    == 0x80;
+				char squash_child_headers =
+				    is_primitive_type(tag);
+
+				/*
+				 * This is a hack, but it sufficies to handle
+				 * NSS's output. If we find an indefinite
+				 * length, context-specific tag with a definite,
+				 * primtive tag inside it, then we assume that
+				 * the context-specific tag is implicit and the
+				 * tags within are fragments of a primitive type
+				 * that need to be concatenated.
+				 */
+				if (context_specific &&
+				    (tag & CBS_ASN1_CONSTRUCTED)) {
+					CBS in_copy, inner_contents;
+					unsigned int inner_tag;
+					size_t inner_header_len;
+
+					CBS_init(&in_copy, CBS_data(in),
+					    CBS_len(in));
+					if (!cbs_nonstrict_get_any_asn1_element(
+					    &in_copy, &inner_contents,
+					    &inner_tag, &inner_header_len))
+						return 0;
+
+					if (CBS_len(&inner_contents) >
+					    inner_header_len &&
+					    is_primitive_type(inner_tag))
+						squash_child_headers = 1;
+				}
+
+				if (!squash_header) {
+					unsigned int out_tag = tag;
+
+					if (squash_child_headers)
+						out_tag &=
+						    ~CBS_ASN1_CONSTRUCTED;
+
+					if (!CBB_add_asn1(out,
+					    &out_contents_storage, out_tag))
+						return 0;
+
+					out_contents = &out_contents_storage;
+				}
+
+				if (!cbs_convert_indefinite(in, out_contents,
+				    squash_child_headers,
+				    1 /* looking for eoc */, depth + 1))
+					return 0;
+
+				if (out_contents != out && !CBB_flush(out))
+					return 0;
+
+				continue;
+			}
+		}
+
+		if (!squash_header) {
+			if (!CBB_add_asn1(out, &out_contents_storage, tag))
+				return 0;
+
+			out_contents = &out_contents_storage;
+		}
+
+		if (!CBS_skip(&contents, header_len))
+			return 0;
+
+		if (tag & CBS_ASN1_CONSTRUCTED) {
+			if (!cbs_convert_indefinite(&contents, out_contents,
+			    0 /* don't squash header */,
+			    0 /* not looking for eoc */, depth + 1))
+				return 0;
+		} else {
+			if (!CBB_add_bytes(out_contents, CBS_data(&contents),
+			    CBS_len(&contents)))
+				return 0;
+		}
+
+		if (out_contents != out && !CBB_flush(out))
+			return 0;
+	}
+
+	return looking_for_eoc == 0;
+}
+
+int
+CBS_asn1_indefinite_to_definite(CBS *in, uint8_t **out, size_t *out_len)
+{
+	CBB cbb;
+
+	/*
+	 * First, do a quick walk to find any indefinite-length elements. Most
+	 * of the time we hope that there aren't any and thus we can quickly
+	 * return.
+	 */
+	char conversion_needed;
+	if (!cbs_find_indefinite(in, &conversion_needed, 0))
+		return 0;
+
+	if (!conversion_needed) {
+		*out = NULL;
+		*out_len = 0;
+		return 1;
+	}
+
+	if (!CBB_init(&cbb, CBS_len(in)))
+		return 0;
+	if (!cbs_convert_indefinite(in, &cbb, 0, 0, 0)) {
+		CBB_cleanup(&cbb);
+		return 0;
+	}
+
+	return CBB_finish(&cbb, out, out_len);
+}
diff --git a/lib/libcrypto/bytestring/bs_cbb.c b/lib/libcrypto/bytestring/bs_cbb.c
new file mode 100644
index 00000000000..2aaee30a068
--- /dev/null
+++ b/lib/libcrypto/bytestring/bs_cbb.c
@@ -0,0 +1,467 @@
+/*	$OpenBSD: bs_cbb.c,v 1.1 2021/11/20 18:10:52 jsing Exp $	*/
+/*
+ * Copyright (c) 2014, Google Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "bytestring.h"
+
+#define CBB_INITIAL_SIZE 64
+
+static int
+cbb_init(CBB *cbb, uint8_t *buf, size_t cap)
+{
+	struct cbb_buffer_st *base;
+
+	if ((base = calloc(1, sizeof(struct cbb_buffer_st))) == NULL)
+		return 0;
+
+	base->buf = buf;
+	base->len = 0;
+	base->cap = cap;
+	base->can_resize = 1;
+
+	cbb->base = base;
+	cbb->is_top_level = 1;
+
+	return 1;
+}
+
+int
+CBB_init(CBB *cbb, size_t initial_capacity)
+{
+	uint8_t *buf = NULL;
+
+	memset(cbb, 0, sizeof(*cbb));
+
+	if (initial_capacity == 0)
+		initial_capacity = CBB_INITIAL_SIZE;
+
+	if ((buf = calloc(1, initial_capacity)) == NULL)
+		return 0;
+
+	if (!cbb_init(cbb, buf, initial_capacity)) {
+		free(buf);
+		return 0;
+	}
+
+	return 1;
+}
+
+int
+CBB_init_fixed(CBB *cbb, uint8_t *buf, size_t len)
+{
+	memset(cbb, 0, sizeof(*cbb));
+
+	if (!cbb_init(cbb, buf, len))
+		return 0;
+
+	cbb->base->can_resize = 0;
+
+	return 1;
+}
+
+void
+CBB_cleanup(CBB *cbb)
+{
+	if (cbb->base) {
+		if (cbb->base->can_resize)
+			freezero(cbb->base->buf, cbb->base->cap);
+		free(cbb->base);
+	}
+	cbb->base = NULL;
+	cbb->child = NULL;
+}
+
+static int
+cbb_buffer_add(struct cbb_buffer_st *base, uint8_t **out, size_t len)
+{
+	size_t newlen;
+
+	if (base == NULL)
+		return 0;
+
+	newlen = base->len + len;
+	if (newlen < base->len)
+		/* Overflow */
+		return 0;
+
+	if (newlen > base->cap) {
+		size_t newcap = base->cap * 2;
+		uint8_t *newbuf;
+
+		if (!base->can_resize)
+			return 0;
+
+		if (newcap < base->cap || newcap < newlen)
+			newcap = newlen;
+
+		newbuf = recallocarray(base->buf, base->cap, newcap, 1);
+		if (newbuf == NULL)
+			return 0;
+
+		base->buf = newbuf;
+		base->cap = newcap;
+	}
+
+	if (out)
+		*out = base->buf + base->len;
+
+	base->len = newlen;
+	return 1;
+}
+
+static int
+cbb_add_u(CBB *cbb, uint32_t v, size_t len_len)
+{
+	uint8_t *buf;
+	size_t i;
+
+	if (len_len == 0)
+		return 1;
+
+	if (len_len > 4)
+		return 0;
+
+	if (!CBB_flush(cbb) || !cbb_buffer_add(cbb->base, &buf, len_len))
+		return 0;
+
+	for (i = len_len - 1; i < len_len; i--) {
+		buf[i] = v;
+		v >>= 8;
+	}
+	return 1;
+}
+
+int
+CBB_finish(CBB *cbb, uint8_t **out_data, size_t *out_len)
+{
+	if (!cbb->is_top_level)
+		return 0;
+
+	if (!CBB_flush(cbb))
+		return 0;
+
+	if (cbb->base->can_resize && (out_data == NULL || out_len == NULL))
+		/*
+		 * |out_data| and |out_len| can only be NULL if the CBB is
+		 * fixed.
+		 */
+		return 0;
+
+	if (out_data != NULL)
+		*out_data = cbb->base->buf;
+
+	if (out_len != NULL)
+		*out_len = cbb->base->len;
+
+	cbb->base->buf = NULL;
+	CBB_cleanup(cbb);
+	return 1;
+}
+
+/*
+ * CBB_flush recurses and then writes out any pending length prefix. The current
+ * length of the underlying base is taken to be the length of the
+ * length-prefixed data.
+ */
+int
+CBB_flush(CBB *cbb)
+{
+	size_t child_start, i, len;
+
+	if (cbb->base == NULL)
+		return 0;
+
+	if (cbb->child == NULL || cbb->pending_len_len == 0)
+		return 1;
+
+	child_start = cbb->offset + cbb->pending_len_len;
+
+	if (!CBB_flush(cbb->child) || child_start < cbb->offset ||
+	    cbb->base->len < child_start)
+		return 0;
+
+	len = cbb->base->len - child_start;
+
+	if (cbb->pending_is_asn1) {
+		/*
+		 * For ASN.1, we assumed that we were using short form which
+		 * only requires a single byte for the length octet.
+		 *
+		 * If it turns out that we need long form, we have to move
+		 * the contents along in order to make space for more length
+		 * octets.
+		 */
+		size_t len_len = 1;  /* total number of length octets */
+		uint8_t initial_length_byte;
+
+		/* We already wrote 1 byte for the length. */
+		if (cbb->pending_len_len != 1)
+			return 0;
+
+		/* Check for long form */
+		if (len > 0xfffffffe)
+			return 0;	/* 0xffffffff is reserved */
+		else if (len > 0xffffff)
+			len_len = 5;
+		else if (len > 0xffff)
+			len_len = 4;
+		else if (len > 0xff)
+			len_len = 3;
+		else if (len > 0x7f)
+			len_len = 2;
+
+		if (len_len == 1) {
+			/* For short form, the initial byte is the length. */
+			initial_length_byte = len;
+			len = 0;
+
+		} else {
+			/*
+			 * For long form, the initial byte is the number of
+			 * subsequent length octets (plus bit 8 set).
+			 */
+			initial_length_byte = 0x80 | (len_len - 1);
+
+			/*
+			 * We need to move the contents along in order to make
+			 * space for the long form length octets.
+			 */
+			size_t extra_bytes = len_len - 1;
+			if (!cbb_buffer_add(cbb->base, NULL, extra_bytes))
+				return 0;
+
+			memmove(cbb->base->buf + child_start + extra_bytes,
+			    cbb->base->buf + child_start, len);
+		}
+		cbb->base->buf[cbb->offset++] = initial_length_byte;
+		cbb->pending_len_len = len_len - 1;
+	}
+
+	for (i = cbb->pending_len_len - 1; i < cbb->pending_len_len; i--) {
+		cbb->base->buf[cbb->offset + i] = len;
+		len >>= 8;
+	}
+	if (len != 0)
+		return 0;
+
+	cbb->child->base = NULL;
+	cbb->child = NULL;
+	cbb->pending_len_len = 0;
+	cbb->pending_is_asn1 = 0;
+	cbb->offset = 0;
+
+	return 1;
+}
+
+void
+CBB_discard_child(CBB *cbb)
+{
+	if (cbb->child == NULL)
+		return;
+
+	cbb->base->len = cbb->offset;
+
+	cbb->child->base = NULL;
+	cbb->child = NULL;
+	cbb->pending_len_len = 0;
+	cbb->pending_is_asn1 = 0;
+	cbb->offset = 0;
+}
+
+static int
+cbb_add_length_prefixed(CBB *cbb, CBB *out_contents, size_t len_len)
+{
+	uint8_t *prefix_bytes;
+
+	if (!CBB_flush(cbb))
+		return 0;
+
+	cbb->offset = cbb->base->len;
+	if (!cbb_buffer_add(cbb->base, &prefix_bytes, len_len))
+		return 0;
+
+	memset(prefix_bytes, 0, len_len);
+	memset(out_contents, 0, sizeof(CBB));
+	out_contents->base = cbb->base;
+	cbb->child = out_contents;
+	cbb->pending_len_len = len_len;
+	cbb->pending_is_asn1 = 0;
+
+	return 1;
+}
+
+int
+CBB_add_u8_length_prefixed(CBB *cbb, CBB *out_contents)
+{
+	return cbb_add_length_prefixed(cbb, out_contents, 1);
+}
+
+int
+CBB_add_u16_length_prefixed(CBB *cbb, CBB *out_contents)
+{
+	return cbb_add_length_prefixed(cbb, out_contents, 2);
+}
+
+int
+CBB_add_u24_length_prefixed(CBB *cbb, CBB *out_contents)
+{
+	return cbb_add_length_prefixed(cbb, out_contents, 3);
+}
+
+int
+CBB_add_asn1(CBB *cbb, CBB *out_contents, unsigned int tag)
+{
+	if (tag > UINT8_MAX)
+		return 0;
+
+	/* Long form identifier octets are not supported. */
+	if ((tag & 0x1f) == 0x1f)
+		return 0;
+
+	/* Short-form identifier octet only needs a single byte */
+	if (!CBB_flush(cbb) || !CBB_add_u8(cbb, tag))
+		return 0;
+
+	/*
+	 * Add 1 byte to cover the short-form length octet case.  If it turns
+	 * out we need long-form, it will be extended later.
+	 */
+	cbb->offset = cbb->base->len;
+	if (!CBB_add_u8(cbb, 0))
+		return 0;
+
+	memset(out_contents, 0, sizeof(CBB));
+	out_contents->base = cbb->base;
+	cbb->child = out_contents;
+	cbb->pending_len_len = 1;
+	cbb->pending_is_asn1 = 1;
+
+	return 1;
+}
+
+int
+CBB_add_bytes(CBB *cbb, const uint8_t *data, size_t len)
+{
+	uint8_t *dest;
+
+	if (!CBB_flush(cbb) || !cbb_buffer_add(cbb->base, &dest, len))
+		return 0;
+
+	memcpy(dest, data, len);
+	return 1;
+}
+
+int
+CBB_add_space(CBB *cbb, uint8_t **out_data, size_t len)
+{
+	if (!CBB_flush(cbb) || !cbb_buffer_add(cbb->base, out_data, len))
+		return 0;
+
+	memset(*out_data, 0, len);
+	return 1;
+}
+
+int
+CBB_add_u8(CBB *cbb, size_t value)
+{
+	if (value > UINT8_MAX)
+		return 0;
+
+	return cbb_add_u(cbb, (uint32_t)value, 1);
+}
+
+int
+CBB_add_u16(CBB *cbb, size_t value)
+{
+	if (value > UINT16_MAX)
+		return 0;
+
+	return cbb_add_u(cbb, (uint32_t)value, 2);
+}
+
+int
+CBB_add_u24(CBB *cbb, size_t value)
+{
+	if (value > 0xffffffUL)
+		return 0;
+
+	return cbb_add_u(cbb, (uint32_t)value, 3);
+}
+
+int
+CBB_add_u32(CBB *cbb, size_t value)
+{
+	if (value > 0xffffffffUL)
+		return 0;
+
+	return cbb_add_u(cbb, (uint32_t)value, 4);
+}
+
+int
+CBB_add_asn1_uint64(CBB *cbb, uint64_t value)
+{
+	CBB child;
+	size_t i;
+	int started = 0;
+
+	if (!CBB_add_asn1(cbb, &child, CBS_ASN1_INTEGER))
+		return 0;
+
+	for (i = 0; i < 8; i++) {
+		uint8_t byte = (value >> 8 * (7 - i)) & 0xff;
+
+		/*
+		 * ASN.1 restriction: first 9 bits cannot be all zeroes or
+		 * all ones.  Since this function only encodes unsigned
+		 * integers, the only concerns are not encoding leading
+		 * zeros and adding a padding byte if necessary.
+		 *
+		 * In practice, this means:
+		 * 1) Skip leading octets of all zero bits in the value
+		 * 2) After skipping the leading zero octets, if the next 9
+		 *    bits are all ones, add an all zero prefix octet (and
+		 *    set the high bit of the prefix octet if negative).
+		 *
+		 * Additionally, for an unsigned value, add an all zero
+		 * prefix if the high bit of the first octet would be one.
+		 */
+		if (!started) {
+			if (byte == 0)
+				/* Don't encode leading zeros. */
+				continue;
+
+			/*
+			 * If the high bit is set, add a padding byte to make it
+			 * unsigned.
+			 */
+			if ((byte & 0x80) && !CBB_add_u8(&child, 0))
+				return 0;
+
+			started = 1;
+		}
+		if (!CBB_add_u8(&child, byte))
+			return 0;
+	}
+
+	/* 0 is encoded as a single 0, not the empty string. */
+	if (!started && !CBB_add_u8(&child, 0))
+		return 0;
+
+	return CBB_flush(cbb);
+}
diff --git a/lib/libcrypto/bytestring/bs_cbs.c b/lib/libcrypto/bytestring/bs_cbs.c
new file mode 100644
index 00000000000..06283abd946
--- /dev/null
+++ b/lib/libcrypto/bytestring/bs_cbs.c
@@ -0,0 +1,510 @@
+/*	$OpenBSD: bs_cbs.c,v 1.1 2021/11/20 18:10:52 jsing Exp $	*/
+/*
+ * Copyright (c) 2014, Google Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "bytestring.h"
+
+void
+CBS_init(CBS *cbs, const uint8_t *data, size_t len)
+{
+	cbs->data = data;
+	cbs->initial_len = len;
+	cbs->len = len;
+}
+
+void
+CBS_dup(const CBS *cbs, CBS *out)
+{
+	CBS_init(out, CBS_data(cbs), CBS_len(cbs));
+	out->initial_len = cbs->initial_len;
+}
+
+static int
+cbs_get(CBS *cbs, const uint8_t **p, size_t n)
+{
+	if (cbs->len < n)
+		return 0;
+
+	*p = cbs->data;
+	cbs->data += n;
+	cbs->len -= n;
+	return 1;
+}
+
+size_t
+CBS_offset(const CBS *cbs)
+{
+	return cbs->initial_len - cbs->len;
+}
+
+int
+CBS_skip(CBS *cbs, size_t len)
+{
+	const uint8_t *dummy;
+	return cbs_get(cbs, &dummy, len);
+}
+
+const uint8_t *
+CBS_data(const CBS *cbs)
+{
+	return cbs->data;
+}
+
+size_t
+CBS_len(const CBS *cbs)
+{
+	return cbs->len;
+}
+
+int
+CBS_stow(const CBS *cbs, uint8_t **out_ptr, size_t *out_len)
+{
+	free(*out_ptr);
+	*out_ptr = NULL;
+	*out_len = 0;
+
+	if (cbs->len == 0)
+		return 1;
+
+	if ((*out_ptr = malloc(cbs->len)) == NULL)
+		return 0;
+
+	memcpy(*out_ptr, cbs->data, cbs->len);
+
+	*out_len = cbs->len;
+	return 1;
+}
+
+int
+CBS_strdup(const CBS *cbs, char **out_ptr)
+{
+	free(*out_ptr);
+	*out_ptr = NULL;
+
+	if (CBS_contains_zero_byte(cbs))
+		return 0;
+
+	*out_ptr = strndup((const char *)cbs->data, cbs->len);
+	return (*out_ptr != NULL);
+}
+
+int
+CBS_write_bytes(const CBS *cbs, uint8_t *dst, size_t dst_len, size_t *copied)
+{
+	if (dst_len < cbs->len)
+		return 0;
+
+	memmove(dst, cbs->data, cbs->len);
+
+	if (copied != NULL)
+		*copied = cbs->len;
+
+	return 1;
+}
+
+int
+CBS_contains_zero_byte(const CBS *cbs)
+{
+	return memchr(cbs->data, 0, cbs->len) != NULL;
+}
+
+int
+CBS_mem_equal(const CBS *cbs, const uint8_t *data, size_t len)
+{
+	if (len != cbs->len)
+		return 0;
+
+	return timingsafe_memcmp(cbs->data, data, len) == 0;
+}
+
+static int
+cbs_get_u(CBS *cbs, uint32_t *out, size_t len)
+{
+	uint32_t result = 0;
+	size_t i;
+	const uint8_t *data;
+
+	if (len < 1 || len > 4)
+		return 0;
+
+	if (!cbs_get(cbs, &data, len))
+		return 0;
+
+	for (i = 0; i < len; i++) {
+		result <<= 8;
+		result |= data[i];
+	}
+	*out = result;
+	return 1;
+}
+
+int
+CBS_get_u8(CBS *cbs, uint8_t *out)
+{
+	const uint8_t *v;
+
+	if (!cbs_get(cbs, &v, 1))
+		return 0;
+
+	*out = *v;
+	return 1;
+}
+
+int
+CBS_get_u16(CBS *cbs, uint16_t *out)
+{
+	uint32_t v;
+
+	if (!cbs_get_u(cbs, &v, 2))
+		return 0;
+
+	*out = v;
+	return 1;
+}
+
+int
+CBS_get_u24(CBS *cbs, uint32_t *out)
+{
+	return cbs_get_u(cbs, out, 3);
+}
+
+int
+CBS_get_u32(CBS *cbs, uint32_t *out)
+{
+	return cbs_get_u(cbs, out, 4);
+}
+
+int
+CBS_get_bytes(CBS *cbs, CBS *out, size_t len)
+{
+	const uint8_t *v;
+
+	if (!cbs_get(cbs, &v, len))
+		return 0;
+
+	CBS_init(out, v, len);
+	return 1;
+}
+
+static int
+cbs_get_length_prefixed(CBS *cbs, CBS *out, size_t len_len)
+{
+	uint32_t len;
+
+	if (!cbs_get_u(cbs, &len, len_len))
+		return 0;
+
+	return CBS_get_bytes(cbs, out, len);
+}
+
+int
+CBS_get_u8_length_prefixed(CBS *cbs, CBS *out)
+{
+	return cbs_get_length_prefixed(cbs, out, 1);
+}
+
+int
+CBS_get_u16_length_prefixed(CBS *cbs, CBS *out)
+{
+	return cbs_get_length_prefixed(cbs, out, 2);
+}
+
+int
+CBS_get_u24_length_prefixed(CBS *cbs, CBS *out)
+{
+	return cbs_get_length_prefixed(cbs, out, 3);
+}
+
+int
+CBS_get_any_asn1_element(CBS *cbs, CBS *out, unsigned int *out_tag,
+    size_t *out_header_len)
+{
+	return cbs_get_any_asn1_element_internal(cbs, out, out_tag,
+	    out_header_len, 1);
+}
+
+/*
+ * Review X.690 for details on ASN.1 DER encoding.
+ *
+ * If non-strict mode is enabled, then DER rules are relaxed
+ * for indefinite constructs (violates DER but a little closer to BER).
+ * Non-strict mode should only be used by bs_ber.c
+ *
+ * Sections 8, 10 and 11 for DER encoding
+ */
+int
+cbs_get_any_asn1_element_internal(CBS *cbs, CBS *out, unsigned int *out_tag,
+    size_t *out_header_len, int strict)
+{
+	uint8_t tag, length_byte;
+	CBS header = *cbs;
+	CBS throwaway;
+	size_t len;
+
+	if (out == NULL)
+		out = &throwaway;
+
+	/*
+	 * Get identifier octet and length octet.  Only 1 octet for each
+	 * is a CBS limitation.
+	 */
+	if (!CBS_get_u8(&header, &tag) || !CBS_get_u8(&header, &length_byte))
+		return 0;
+
+	/* CBS limitation: long form tags are not supported. */
+	if ((tag & 0x1f) == 0x1f)
+		return 0;
+
+	if (out_tag != NULL)
+		*out_tag = tag;
+
+	if ((length_byte & 0x80) == 0) {
+		/* Short form length. */
+		len = ((size_t) length_byte) + 2;
+		if (out_header_len != NULL)
+			*out_header_len = 2;
+
+	} else {
+		/* Long form length. */
+		const size_t num_bytes = length_byte & 0x7f;
+		uint32_t len32;
+
+		/* ASN.1 reserved value for future extensions */
+		if (num_bytes == 0x7f)
+			return 0;
+
+		/* Handle indefinite form length */
+		if (num_bytes == 0) {
+			/* DER encoding doesn't allow for indefinite form. */
+			if (strict)
+				return 0;
+
+			/* Primitive cannot use indefinite in BER or DER. */
+			if ((tag & CBS_ASN1_CONSTRUCTED) == 0)
+				return 0;
+
+			/* Constructed, indefinite length allowed in BER. */
+			if (out_header_len != NULL)
+				*out_header_len = 2;
+			return CBS_get_bytes(cbs, out, 2);
+		}
+
+		/* CBS limitation. */
+		if (num_bytes > 4)
+			return 0;
+
+		if (!cbs_get_u(&header, &len32, num_bytes))
+			return 0;
+
+		/* DER has a minimum length octet requirement. */
+		if (len32 < 128)
+			/* Should have used short form instead */
+			return 0;
+
+		if ((len32 >> ((num_bytes - 1) * 8)) == 0)
+			/* Length should have been at least one byte shorter. */
+			return 0;
+
+		len = len32;
+		if (len + 2 + num_bytes < len)
+			/* Overflow. */
+			return 0;
+
+		len += 2 + num_bytes;
+		if (out_header_len != NULL)
+			*out_header_len = 2 + num_bytes;
+	}
+
+	return CBS_get_bytes(cbs, out, len);
+}
+
+static int
+cbs_get_asn1(CBS *cbs, CBS *out, unsigned int tag_value, int skip_header)
+{
+	size_t header_len;
+	unsigned int tag;
+	CBS throwaway;
+
+	if (out == NULL)
+		out = &throwaway;
+
+	if (!CBS_get_any_asn1_element(cbs, out, &tag, &header_len) ||
+	    tag != tag_value)
+		return 0;
+
+	if (skip_header && !CBS_skip(out, header_len))
+		return 0;
+
+	return 1;
+}
+
+int
+CBS_get_asn1(CBS *cbs, CBS *out, unsigned int tag_value)
+{
+	return cbs_get_asn1(cbs, out, tag_value, 1 /* skip header */);
+}
+
+int
+CBS_get_asn1_element(CBS *cbs, CBS *out, unsigned int tag_value)
+{
+	return cbs_get_asn1(cbs, out, tag_value, 0 /* include header */);
+}
+
+int
+CBS_peek_asn1_tag(const CBS *cbs, unsigned int tag_value)
+{
+	if (CBS_len(cbs) < 1)
+		return 0;
+
+	/*
+	 * Tag number 31 indicates the start of a long form number.
+	 * This is valid in ASN.1, but CBS only supports short form.
+	 */
+	if ((tag_value & 0x1f) == 0x1f)
+		return 0;
+
+	return CBS_data(cbs)[0] == tag_value;
+}
+
+/* Encoding details are in ASN.1: X.690 section 8.3 */
+int
+CBS_get_asn1_uint64(CBS *cbs, uint64_t *out)
+{
+	CBS bytes;
+	const uint8_t *data;
+	size_t i, len;
+
+	if (!CBS_get_asn1(cbs, &bytes, CBS_ASN1_INTEGER))
+		return 0;
+
+	*out = 0;
+	data = CBS_data(&bytes);
+	len = CBS_len(&bytes);
+
+	if (len == 0)
+		/* An INTEGER is encoded with at least one content octet. */
+		return 0;
+
+	if ((data[0] & 0x80) != 0)
+		/* Negative number. */
+		return 0;
+
+	if (data[0] == 0 && len > 1 && (data[1] & 0x80) == 0)
+		/* Violates smallest encoding rule: excessive leading zeros. */
+		return 0;
+
+	for (i = 0; i < len; i++) {
+		if ((*out >> 56) != 0)
+			/* Too large to represent as a uint64_t. */
+			return 0;
+
+		*out <<= 8;
+		*out |= data[i];
+	}
+
+	return 1;
+}
+
+int
+CBS_get_optional_asn1(CBS *cbs, CBS *out, int *out_present, unsigned int tag)
+{
+	if (CBS_peek_asn1_tag(cbs, tag)) {
+		if (!CBS_get_asn1(cbs, out, tag))
+			return 0;
+
+		*out_present = 1;
+	} else {
+		*out_present = 0;
+	}
+	return 1;
+}
+
+int
+CBS_get_optional_asn1_octet_string(CBS *cbs, CBS *out, int *out_present,
+    unsigned int tag)
+{
+	CBS child;
+	int present;
+
+	if (!CBS_get_optional_asn1(cbs, &child, &present, tag))
+		return 0;
+
+	if (present) {
+		if (!CBS_get_asn1(&child, out, CBS_ASN1_OCTETSTRING) ||
+		    CBS_len(&child) != 0)
+			return 0;
+	} else {
+		CBS_init(out, NULL, 0);
+	}
+	if (out_present)
+		*out_present = present;
+
+	return 1;
+}
+
+int
+CBS_get_optional_asn1_uint64(CBS *cbs, uint64_t *out, unsigned int tag,
+    uint64_t default_value)
+{
+	CBS child;
+	int present;
+
+	if (!CBS_get_optional_asn1(cbs, &child, &present, tag))
+		return 0;
+
+	if (present) {
+		if (!CBS_get_asn1_uint64(&child, out) ||
+		    CBS_len(&child) != 0)
+			return 0;
+	} else {
+		*out = default_value;
+	}
+	return 1;
+}
+
+int
+CBS_get_optional_asn1_bool(CBS *cbs, int *out, unsigned int tag,
+    int default_value)
+{
+	CBS child, child2;
+	int present;
+
+	if (!CBS_get_optional_asn1(cbs, &child, &present, tag))
+		return 0;
+
+	if (present) {
+		uint8_t boolean;
+
+		if (!CBS_get_asn1(&child, &child2, CBS_ASN1_BOOLEAN) ||
+		    CBS_len(&child2) != 1 || CBS_len(&child) != 0)
+			return 0;
+
+		boolean = CBS_data(&child2)[0];
+		if (boolean == 0)
+			*out = 0;
+		else if (boolean == 0xff)
+			*out = 1;
+		else
+			return 0;
+
+	} else {
+		*out = default_value;
+	}
+	return 1;
+}
diff --git a/lib/libcrypto/bytestring/bytestring.h b/lib/libcrypto/bytestring/bytestring.h
new file mode 100644
index 00000000000..7728ef8de26
--- /dev/null
+++ b/lib/libcrypto/bytestring/bytestring.h
@@ -0,0 +1,518 @@
+/*	$OpenBSD: bytestring.h,v 1.1 2021/11/20 18:10:52 jsing Exp $	*/
+/*
+ * Copyright (c) 2014, Google Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef OPENSSL_HEADER_BYTESTRING_H
+#define OPENSSL_HEADER_BYTESTRING_H
+
+#include <sys/types.h>
+#include <stdint.h>
+
+__BEGIN_HIDDEN_DECLS
+
+/*
+ * Bytestrings are used for parsing and building TLS and ASN.1 messages.
+ *
+ * A "CBS" (CRYPTO ByteString) represents a string of bytes in memory and
+ * provides utility functions for safely parsing length-prefixed structures
+ * like TLS and ASN.1 from it.
+ *
+ * A "CBB" (CRYPTO ByteBuilder) is a memory buffer that grows as needed and
+ * provides utility functions for building length-prefixed messages.
+ */
+
+/* CRYPTO ByteString */
+typedef struct cbs_st {
+	const uint8_t *data;
+	size_t initial_len;
+	size_t len;
+} CBS;
+
+/*
+ * CBS_init sets |cbs| to point to |data|. It does not take ownership of
+ * |data|.
+ */
+void CBS_init(CBS *cbs, const uint8_t *data, size_t len);
+
+/*
+ * CBS_skip advances |cbs| by |len| bytes. It returns one on success and zero
+ * otherwise.
+ */
+int CBS_skip(CBS *cbs, size_t len);
+
+/*
+ * CBS_data returns a pointer to the contents of |cbs|.
+ */
+const uint8_t *CBS_data(const CBS *cbs);
+
+/*
+ * CBS_len returns the number of bytes remaining in |cbs|.
+ */
+size_t CBS_len(const CBS *cbs);
+
+/*
+ * CBS_offset returns the current offset into the original data of |cbs|.
+ */
+size_t CBS_offset(const CBS *cbs);
+
+/*
+ * CBS_stow copies the current contents of |cbs| into |*out_ptr| and
+ * |*out_len|. If |*out_ptr| is not NULL, the contents are freed with
+ * free. It returns one on success and zero on allocation failure. On
+ * success, |*out_ptr| should be freed with free. If |cbs| is empty,
+ * |*out_ptr| will be NULL.
+ */
+int CBS_stow(const CBS *cbs, uint8_t **out_ptr, size_t *out_len);
+
+/*
+ * CBS_strdup copies the current contents of |cbs| into |*out_ptr| as a
+ * NUL-terminated C string. If |*out_ptr| is not NULL, the contents are freed
+ * with free. It returns one on success and zero on allocation
+ * failure. On success, |*out_ptr| should be freed with free.
+ *
+ * NOTE: If |cbs| contains NUL bytes, the string will be truncated. Call
+ * |CBS_contains_zero_byte(cbs)| to check for NUL bytes.
+ */
+int CBS_strdup(const CBS *cbs, char **out_ptr);
+
+/*
+ * CBS_write_bytes writes all of the remaining data from |cbs| into |dst|
+ * if it is at most |dst_len| bytes.  If |copied| is not NULL, it will be set
+ * to the amount copied. It returns one on success and zero otherwise.
+ */
+int CBS_write_bytes(const CBS *cbs, uint8_t *dst, size_t dst_len,
+    size_t *copied);
+
+/*
+ * CBS_contains_zero_byte returns one if the current contents of |cbs| contains
+ * a NUL byte and zero otherwise.
+ */
+int CBS_contains_zero_byte(const CBS *cbs);
+
+/*
+ * CBS_mem_equal compares the current contents of |cbs| with the |len| bytes
+ * starting at |data|. If they're equal, it returns one, otherwise zero. If the
+ * lengths match, it uses a constant-time comparison.
+ */
+int CBS_mem_equal(const CBS *cbs, const uint8_t *data, size_t len);
+
+/*
+ * CBS_get_u8 sets |*out| to the next uint8_t from |cbs| and advances |cbs|. It
+ * returns one on success and zero on error.
+ */
+int CBS_get_u8(CBS *cbs, uint8_t *out);
+
+/*
+ * CBS_get_u16 sets |*out| to the next, big-endian uint16_t from |cbs| and
+ * advances |cbs|. It returns one on success and zero on error.
+ */
+int CBS_get_u16(CBS *cbs, uint16_t *out);
+
+/*
+ * CBS_get_u24 sets |*out| to the next, big-endian 24-bit value from |cbs| and
+ * advances |cbs|. It returns one on success and zero on error.
+ */
+int CBS_get_u24(CBS *cbs, uint32_t *out);
+
+/*
+ * CBS_get_u32 sets |*out| to the next, big-endian uint32_t value from |cbs|
+ * and advances |cbs|. It returns one on success and zero on error.
+ */
+int CBS_get_u32(CBS *cbs, uint32_t *out);
+
+/*
+ * CBS_get_bytes sets |*out| to the next |len| bytes from |cbs| and advances
+ * |cbs|. It returns one on success and zero on error.
+ */
+int CBS_get_bytes(CBS *cbs, CBS *out, size_t len);
+
+/*
+ * CBS_get_u8_length_prefixed sets |*out| to the contents of an 8-bit,
+ * length-prefixed value from |cbs| and advances |cbs| over it. It returns one
+ * on success and zero on error.
+ */
+int CBS_get_u8_length_prefixed(CBS *cbs, CBS *out);
+
+/*
+ * CBS_get_u16_length_prefixed sets |*out| to the contents of a 16-bit,
+ * big-endian, length-prefixed value from |cbs| and advances |cbs| over it. It
+ * returns one on success and zero on error.
+ */
+int CBS_get_u16_length_prefixed(CBS *cbs, CBS *out);
+
+/*
+ * CBS_get_u24_length_prefixed sets |*out| to the contents of a 24-bit,
+ * big-endian, length-prefixed value from |cbs| and advances |cbs| over it. It
+ * returns one on success and zero on error.
+ */
+int CBS_get_u24_length_prefixed(CBS *cbs, CBS *out);
+
+
+/* Parsing ASN.1 */
+
+/*
+ * While an identifier can be multiple octets, this library only handles the
+ * single octet variety currently.  This limits support up to tag number 30
+ * since tag number 31 is a reserved value to indicate multiple octets.
+ */
+
+/* Bits 8 and 7: class tag type: See X.690 section 8.1.2.2. */
+#define CBS_ASN1_UNIVERSAL		0x00
+#define CBS_ASN1_APPLICATION		0x40
+#define CBS_ASN1_CONTEXT_SPECIFIC	0x80
+#define CBS_ASN1_PRIVATE		0xc0
+
+/* Bit 6: Primitive or constructed: See X.690 section 8.1.2.3. */
+#define CBS_ASN1_PRIMITIVE	0x00
+#define CBS_ASN1_CONSTRUCTED	0x20
+
+/*
+ * Bits 5 to 1 are the tag number.  See X.680 section 8.6 for tag numbers of
+ * the universal class.
+ */
+
+/*
+ * Common universal identifier octets.
+ * See X.690 section 8.1 and X.680 section 8.6 for universal tag numbers.
+ *
+ * Note: These definitions are the cause of some of the strange behavior in
+ * CBS's bs_ber.c.
+ *
+ * In BER, it is the sender's option to use primitive or constructed for
+ * bitstring (X.690 section 8.6.1) and octetstring (X.690 section 8.7.1).
+ *
+ * In DER, bitstring and octetstring are required to be primitive
+ * (X.690 section 10.2).
+ */
+#define CBS_ASN1_BOOLEAN     (CBS_ASN1_UNIVERSAL | CBS_ASN1_PRIMITIVE | 0x1)
+#define CBS_ASN1_INTEGER     (CBS_ASN1_UNIVERSAL | CBS_ASN1_PRIMITIVE | 0x2)
+#define CBS_ASN1_BITSTRING   (CBS_ASN1_UNIVERSAL | CBS_ASN1_PRIMITIVE | 0x3)
+#define CBS_ASN1_OCTETSTRING (CBS_ASN1_UNIVERSAL | CBS_ASN1_PRIMITIVE | 0x4)
+#define CBS_ASN1_OBJECT      (CBS_ASN1_UNIVERSAL | CBS_ASN1_PRIMITIVE | 0x6)
+#define CBS_ASN1_ENUMERATED  (CBS_ASN1_UNIVERSAL | CBS_ASN1_PRIMITIVE | 0xa)
+#define CBS_ASN1_SEQUENCE    (CBS_ASN1_UNIVERSAL | CBS_ASN1_CONSTRUCTED | 0x10)
+#define CBS_ASN1_SET         (CBS_ASN1_UNIVERSAL | CBS_ASN1_CONSTRUCTED | 0x11)
+
+/*
+ * CBS_get_asn1 sets |*out| to the contents of DER-encoded, ASN.1 element (not
+ * including tag and length bytes) and advances |cbs| over it. The ASN.1
+ * element must match |tag_value|. It returns one on success and zero
+ * on error.
+ *
+ * Tag numbers greater than 30 are not supported (i.e. short form only).
+ */
+int CBS_get_asn1(CBS *cbs, CBS *out, unsigned int tag_value);
+
+/*
+ * CBS_get_asn1_element acts like |CBS_get_asn1| but |out| will include the
+ * ASN.1 header bytes too.
+ */
+int CBS_get_asn1_element(CBS *cbs, CBS *out, unsigned int tag_value);
+
+/*
+ * CBS_peek_asn1_tag looks ahead at the next ASN.1 tag and returns one
+ * if the next ASN.1 element on |cbs| would have tag |tag_value|. If
+ * |cbs| is empty or the tag does not match, it returns zero. Note: if
+ * it returns one, CBS_get_asn1 may still fail if the rest of the
+ * element is malformed.
+ */
+int CBS_peek_asn1_tag(const CBS *cbs, unsigned int tag_value);
+
+/*
+ * 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.
+ * Each of |out|, |out_tag|, and |out_header_len| may be NULL to ignore
+ * the value.
+ *
+ * Tag numbers greater than 30 are not supported (i.e. short form only).
+ */
+int CBS_get_any_asn1_element(CBS *cbs, CBS *out, unsigned int *out_tag,
+    size_t *out_header_len);
+
+/*
+ * CBS_get_asn1_uint64 gets an ASN.1 INTEGER from |cbs| using |CBS_get_asn1|
+ * and sets |*out| to its value. It returns one on success and zero on error,
+ * where error includes the integer being negative, or too large to represent
+ * in 64 bits.
+ */
+int CBS_get_asn1_uint64(CBS *cbs, uint64_t *out);
+
+/*
+ * CBS_get_optional_asn1 gets an optional explicitly-tagged element
+ * from |cbs| tagged with |tag| and sets |*out| to its contents. If
+ * present, it sets |*out_present| to one, otherwise zero. It returns
+ * one on success, whether or not the element was present, and zero on
+ * decode failure.
+ */
+int CBS_get_optional_asn1(CBS *cbs, CBS *out, int *out_present,
+    unsigned int tag);
+
+/*
+ * CBS_get_optional_asn1_octet_string gets an optional
+ * explicitly-tagged OCTET STRING from |cbs|. If present, it sets
+ * |*out| to the string and |*out_present| to one. Otherwise, it sets
+ * |*out| to empty and |*out_present| to zero. |out_present| may be
+ * NULL. It returns one on success, whether or not the element was
+ * present, and zero on decode failure.
+ */
+int CBS_get_optional_asn1_octet_string(CBS *cbs, CBS *out, int *out_present,
+    unsigned int tag);
+
+/*
+ * CBS_get_optional_asn1_uint64 gets an optional explicitly-tagged
+ * INTEGER from |cbs|. If present, it sets |*out| to the
+ * value. Otherwise, it sets |*out| to |default_value|. It returns one
+ * on success, whether or not the element was present, and zero on
+ * decode failure.
+ */
+int CBS_get_optional_asn1_uint64(CBS *cbs, uint64_t *out, unsigned int tag,
+    uint64_t default_value);
+
+/*
+ * CBS_get_optional_asn1_bool gets an optional, explicitly-tagged BOOLEAN from
+ * |cbs|. If present, it sets |*out| to either zero or one, based on the
+ * boolean. Otherwise, it sets |*out| to |default_value|. It returns one on
+ * success, whether or not the element was present, and zero on decode
+ * failure.
+ */
+int CBS_get_optional_asn1_bool(CBS *cbs, int *out, unsigned int tag,
+    int default_value);
+
+
+/*
+ * CRYPTO ByteBuilder.
+ *
+ * |CBB| objects allow one to build length-prefixed serialisations. A |CBB|
+ * object is associated with a buffer and new buffers are created with
+ * |CBB_init|. Several |CBB| objects can point at the same buffer when a
+ * length-prefix is pending, however only a single |CBB| can be 'current' at
+ * any one time. For example, if one calls |CBB_add_u8_length_prefixed| then
+ * the new |CBB| points at the same buffer as the original. But if the original
+ * |CBB| is used then the length prefix is written out and the new |CBB| must
+ * not be used again.
+ *
+ * If one needs to force a length prefix to be written out because a |CBB| is
+ * going out of scope, use |CBB_flush|.
+ */
+
+struct cbb_buffer_st {
+	uint8_t *buf;
+
+	/* The number of valid bytes. */
+	size_t len;
+
+	/* The size of buf. */
+	size_t cap;
+
+	/*
+	 * One iff |buf| is owned by this object. If not then |buf| cannot be
+	 * resized.
+	 */
+	char can_resize;
+};
+
+typedef struct cbb_st {
+	struct cbb_buffer_st *base;
+
+	/*
+	 * offset is the offset from the start of |base->buf| to the position of any
+	 * pending length-prefix.
+	 */
+	size_t offset;
+
+	/* child points to a child CBB if a length-prefix is pending. */
+	struct cbb_st *child;
+
+	/*
+	 * pending_len_len contains the number of bytes in a pending length-prefix,
+	 * or zero if no length-prefix is pending.
+	 */
+	uint8_t pending_len_len;
+
+	char pending_is_asn1;
+
+	/*
+	 * is_top_level is true iff this is a top-level |CBB| (as opposed to a child
+	 * |CBB|). Top-level objects are valid arguments for |CBB_finish|.
+	 */
+	char is_top_level;
+} CBB;
+
+/*
+ * CBB_init initialises |cbb| with |initial_capacity|. Since a |CBB| grows as
+ * needed, the |initial_capacity| is just a hint. It returns one on success or
+ * zero on error.
+ */
+int CBB_init(CBB *cbb, size_t initial_capacity);
+
+/*
+ * CBB_init_fixed initialises |cbb| to write to |len| bytes at |buf|. Since
+ * |buf| cannot grow, trying to write more than |len| bytes will cause CBB
+ * functions to fail. It returns one on success or zero on error.
+ */
+int CBB_init_fixed(CBB *cbb, uint8_t *buf, size_t len);
+
+/*
+ * CBB_cleanup frees all resources owned by |cbb| and other |CBB| objects
+ * writing to the same buffer. This should be used in an error case where a
+ * serialisation is abandoned.
+ */
+void CBB_cleanup(CBB *cbb);
+
+/*
+ * CBB_finish completes any pending length prefix and sets |*out_data| to a
+ * malloced buffer and |*out_len| to the length of that buffer. The caller
+ * takes ownership of the buffer and, unless the buffer was fixed with
+ * |CBB_init_fixed|, must call |free| when done.
+ *
+ * It can only be called on a "top level" |CBB|, i.e. one initialised with
+ * |CBB_init| or |CBB_init_fixed|. It returns one on success and zero on
+ * error.
+ */
+int CBB_finish(CBB *cbb, uint8_t **out_data, size_t *out_len);
+
+/*
+ * CBB_flush causes any pending length prefixes to be written out and any child
+ * |CBB| objects of |cbb| to be invalidated. It returns one on success or zero
+ * on error.
+ */
+int CBB_flush(CBB *cbb);
+
+/*
+ * CBB_discard_child discards the current unflushed child of |cbb|. Neither the
+ * child's contents nor the length prefix will be included in the output.
+ */
+void CBB_discard_child(CBB *cbb);
+
+/*
+ * CBB_add_u8_length_prefixed sets |*out_contents| to a new child of |cbb|. The
+ * data written to |*out_contents| will be prefixed in |cbb| with an 8-bit
+ * length. It returns one on success or zero on error.
+ */
+int CBB_add_u8_length_prefixed(CBB *cbb, CBB *out_contents);
+
+/*
+ * CBB_add_u16_length_prefixed sets |*out_contents| to a new child of |cbb|.
+ * The data written to |*out_contents| will be prefixed in |cbb| with a 16-bit,
+ * big-endian length. It returns one on success or zero on error.
+ */
+int CBB_add_u16_length_prefixed(CBB *cbb, CBB *out_contents);
+
+/*
+ * CBB_add_u24_length_prefixed sets |*out_contents| to a new child of |cbb|.
+ * The data written to |*out_contents| will be prefixed in |cbb| with a 24-bit,
+ * big-endian length. It returns one on success or zero on error.
+ */
+int CBB_add_u24_length_prefixed(CBB *cbb, CBB *out_contents);
+
+/*
+ * CBB_add_asn sets |*out_contents| to a |CBB| into which the contents of an
+ * ASN.1 object can be written. The |tag| argument will be used as the tag for
+ * the object. Passing in |tag| number 31 will return in an error since only
+ * single octet identifiers are supported. It returns one on success or zero
+ * on error.
+ */
+int CBB_add_asn1(CBB *cbb, CBB *out_contents, unsigned int tag);
+
+/*
+ * CBB_add_bytes appends |len| bytes from |data| to |cbb|. It returns one on
+ * success and zero otherwise.
+ */
+int CBB_add_bytes(CBB *cbb, const uint8_t *data, size_t len);
+
+/*
+ * CBB_add_space appends |len| bytes to |cbb| and sets |*out_data| to point to
+ * the beginning of that space. The caller must then write |len| bytes of
+ * actual contents to |*out_data|. It returns one on success and zero
+ * otherwise.
+ */
+int CBB_add_space(CBB *cbb, uint8_t **out_data, size_t len);
+
+/*
+ * CBB_add_u8 appends an 8-bit number from |value| to |cbb|. It returns one on
+ * success and zero otherwise.
+ */
+int CBB_add_u8(CBB *cbb, size_t value);
+
+/*
+ * CBB_add_u8 appends a 16-bit, big-endian number from |value| to |cbb|. It
+ * returns one on success and zero otherwise.
+ */
+int CBB_add_u16(CBB *cbb, size_t value);
+
+/*
+ * CBB_add_u24 appends a 24-bit, big-endian number from |value| to |cbb|. It
+ * returns one on success and zero otherwise.
+ */
+int CBB_add_u24(CBB *cbb, size_t value);
+
+/*
+ * CBB_add_u32 appends a 32-bit, big-endian number from |value| to |cbb|. It
+ * returns one on success and zero otherwise.
+ */
+int CBB_add_u32(CBB *cbb, size_t value);
+
+/*
+ * CBB_add_asn1_uint64 writes an ASN.1 INTEGER into |cbb| using |CBB_add_asn1|
+ * and writes |value| in its contents. It returns one on success and zero on
+ * error.
+ */
+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
+ * strict mode is disabled and the element has indefinite length then |*out|
+ * will only contain the header. Each of |out|, |out_tag|, and
+ * |out_header_len| may be NULL to ignore the value.
+ *
+ * Tag numbers greater than 30 are not supported (i.e. short form only).
+ */
+int cbs_get_any_asn1_element_internal(CBS *cbs, CBS *out, unsigned int *out_tag,
+    size_t *out_header_len, int strict);
+
+/*
+ * CBS_asn1_indefinite_to_definite reads an ASN.1 structure from |in|. If it
+ * finds indefinite-length elements that otherwise appear to be valid DER, it
+ * attempts to convert the DER-like data to DER and sets |*out| and
+ * |*out_length| to describe a malloced buffer containing the DER data.
+ * Additionally, |*in| will be advanced over the ASN.1 data.
+ *
+ * If it doesn't find any indefinite-length elements then it sets |*out| to
+ * NULL and |*in| is unmodified.
+ *
+ * This is NOT a conversion from BER to DER.  There are many restrictions when
+ * dealing with DER data.  This is only concerned with one: indefinite vs.
+ * definite form. However, this suffices to handle the PKCS#7 and PKCS#12 output
+ * from NSS.
+ *
+ * It returns one on success and zero otherwise.
+ */
+int CBS_asn1_indefinite_to_definite(CBS *in, uint8_t **out, size_t *out_len);
+#endif /* LIBRESSL_INTERNAL */
+
+__END_HIDDEN_DECLS 
+
+#endif  /* OPENSSL_HEADER_BYTESTRING_H */