- /* 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 <assert.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;
-
- /* is_string_type returns one if |tag| is a string type and zero otherwise. It
- * ignores the constructed bit. */
- static int is_string_type(unsigned tag) {
- if ((tag & 0xc0) != 0) {
- return 0;
- }
- switch (tag & 0x1f) {
- case CBS_ASN1_BITSTRING:
- case CBS_ASN1_OCTETSTRING:
- case CBS_ASN1_UTF8STRING:
- case CBS_ASN1_NUMERICSTRING:
- case CBS_ASN1_PRINTABLESTRING:
- case CBS_ASN1_T16STRING:
- case CBS_ASN1_VIDEOTEXSTRING:
- case CBS_ASN1_IA5STRING:
- case CBS_ASN1_GRAPHICSTRING:
- case CBS_ASN1_VISIBLESTRING:
- case CBS_ASN1_GENERALSTRING:
- case CBS_ASN1_UNIVERSALSTRING:
- case CBS_ASN1_BMPSTRING:
- return 1;
- default:
- return 0;
- }
- }
-
- /* cbs_find_ber walks an ASN.1 structure in |orig_in| and sets |*ber_found|
- * depending on whether an indefinite length element or constructed string was
- * found. The value of |orig_in| is not changed. It returns one on success (i.e.
- * |*ber_found| was set) and zero on error. */
- static int cbs_find_ber(const 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) {
- /* Found an indefinite-length element. */
- *ber_found = 1;
- return 1;
- }
- if (tag & CBS_ASN1_CONSTRUCTED) {
- if (is_string_type(tag)) {
- /* Constructed strings are only legal in BER and require conversion. */
- *ber_found = 1;
- return 1;
- }
- if (!CBS_skip(&contents, header_len) ||
- !cbs_find_ber(&contents, ber_found, depth + 1)) {
- return 0;
- }
- }
- }
-
- return 1;
- }
-
- /* 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
- * |string_tag| is non-zero, then all elements must match |string_tag| up to the
- * constructed bit and primitive element bodies are written to |out| without
- * element headers. This is used when concatenating the fragments of a
- * constructed string. 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, unsigned string_tag,
- char looking_for_eoc, unsigned depth) {
- assert(!(string_tag & CBS_ASN1_CONSTRUCTED));
-
- if (depth > kMaxDepth) {
- return 0;
- }
-
- while (CBS_len(in) > 0) {
- CBS contents;
- unsigned tag, child_string_tag = string_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;
- }
-
- if (is_eoc(header_len, &contents)) {
- return looking_for_eoc;
- }
-
- if (string_tag != 0) {
- /* This is part of a constructed string. All elements must match
- * |string_tag| up to the constructed bit and get appended to |out|
- * without a child element. */
- if ((tag & ~CBS_ASN1_CONSTRUCTED) != string_tag) {
- return 0;
- }
- out_contents = out;
- } else {
- unsigned out_tag = tag;
- if ((tag & CBS_ASN1_CONSTRUCTED) && is_string_type(tag)) {
- /* If a constructed string, clear the constructed bit and inform
- * children to concatenate bodies. */
- out_tag &= ~CBS_ASN1_CONSTRUCTED;
- child_string_tag = out_tag;
- }
- if (!CBB_add_asn1(out, &out_contents_storage, out_tag)) {
- return 0;
- }
- out_contents = &out_contents_storage;
- }
-
- if (CBS_len(&contents) == header_len && header_len > 0 &&
- CBS_data(&contents)[header_len - 1] == 0x80) {
- /* This is an indefinite length element. */
- if (!cbs_convert_ber(in, out_contents, child_string_tag,
- 1 /* looking for eoc */, depth + 1) ||
- !CBB_flush(out)) {
- return 0;
- }
- continue;
- }
-
- if (!CBS_skip(&contents, header_len)) {
- return 0;
- }
-
- if (tag & CBS_ASN1_CONSTRUCTED) {
- /* Recurse into children. */
- if (!cbs_convert_ber(&contents, out_contents, child_string_tag,
- 0 /* not looking for eoc */, depth + 1)) {
- return 0;
- }
- } else {
- /* Copy primitive contents as-is. */
- if (!CBB_add_bytes(out_contents, CBS_data(&contents),
- CBS_len(&contents))) {
- return 0;
- }
- }
-
- if (!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)) ||
- !cbs_convert_ber(in, &cbb, 0, 0, 0) ||
- !CBB_finish(&cbb, out, out_len)) {
- CBB_cleanup(&cbb);
- return 0;
- }
-
- return 1;
- }
-
- int CBS_get_asn1_implicit_string(CBS *in, CBS *out, uint8_t **out_storage,
- unsigned outer_tag, unsigned inner_tag) {
- assert(!(outer_tag & CBS_ASN1_CONSTRUCTED));
- assert(!(inner_tag & CBS_ASN1_CONSTRUCTED));
- assert(is_string_type(inner_tag));
-
- if (CBS_peek_asn1_tag(in, outer_tag)) {
- /* Normal implicitly-tagged string. */
- *out_storage = NULL;
- return CBS_get_asn1(in, out, outer_tag);
- }
-
- /* Otherwise, try to parse an implicitly-tagged constructed string.
- * |CBS_asn1_ber_to_der| is assumed to have run, so only allow one level deep
- * of nesting. */
- CBB result;
- CBS child;
- if (!CBB_init(&result, CBS_len(in)) ||
- !CBS_get_asn1(in, &child, outer_tag | CBS_ASN1_CONSTRUCTED)) {
- goto err;
- }
-
- while (CBS_len(&child) > 0) {
- CBS chunk;
- if (!CBS_get_asn1(&child, &chunk, inner_tag) ||
- !CBB_add_bytes(&result, CBS_data(&chunk), CBS_len(&chunk))) {
- goto err;
- }
- }
-
- uint8_t *data;
- size_t len;
- if (!CBB_finish(&result, &data, &len)) {
- goto err;
- }
-
- CBS_init(out, data, len);
- *out_storage = data;
- return 1;
-
- err:
- CBB_cleanup(&result);
- return 0;
- }
|