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- /* 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 <openssl/bytestring.h>
-
- #include <string.h>
-
- #include "internal.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 kMaxDepth = 2048;
-
- /* cbs_find_ber walks an ASN.1 structure in |orig_in| and sets |*ber_found|
- * depending on whether an indefinite length element was found. The value of
- * |in| is not changed. It returns one on success (i.e. |*ber_found| was set)
- * and zero on error. */
- static int cbs_find_ber(CBS *orig_in, char *ber_found, unsigned depth) {
- CBS in;
-
- if (depth > kMaxDepth) {
- return 0;
- }
-
- CBS_init(&in, CBS_data(orig_in), CBS_len(orig_in));
- *ber_found = 0;
-
- while (CBS_len(&in) > 0) {
- CBS contents;
- unsigned tag;
- size_t header_len;
-
- if (!CBS_get_any_ber_asn1_element(&in, &contents, &tag, &header_len)) {
- return 0;
- }
- if (CBS_len(&contents) == header_len &&
- header_len > 0 &&
- CBS_data(&contents)[header_len-1] == 0x80) {
- *ber_found = 1;
- return 1;
- }
- if (tag & CBS_ASN1_CONSTRUCTED) {
- if (!CBS_skip(&contents, header_len) ||
- !cbs_find_ber(&contents, ber_found, depth + 1)) {
- return 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 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_get_any_ber_asn1_element|, indicate an "end of contents" (EOC) value. */
- static char is_eoc(size_t header_len, CBS *contents) {
- return header_len == 2 && CBS_len(contents) == 2 &&
- memcmp(CBS_data(contents), "\x00\x00", 2) == 0;
- }
-
- /* cbs_convert_ber reads BER data from |in| and writes 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_ber(CBS *in, CBB *out, char squash_header,
- char looking_for_eoc, unsigned depth) {
- if (depth > kMaxDepth) {
- return 0;
- }
-
- while (CBS_len(in) > 0) {
- CBS contents;
- unsigned tag;
- size_t header_len;
- CBB *out_contents, out_contents_storage;
-
- if (!CBS_get_any_ber_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 BER
- * 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 inner_tag;
- size_t inner_header_len;
-
- CBS_init(&in_copy, CBS_data(in), CBS_len(in));
- if (!CBS_get_any_ber_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 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_ber(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_ber(&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_ber_to_der(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_ber(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_ber(in, &cbb, 0, 0, 0)) {
- CBB_cleanup(&cbb);
- return 0;
- }
-
- return CBB_finish(&cbb, out, out_len);
- }
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