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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/buf.h>
- #include <openssl/mem.h>
- #include <openssl/bytestring.h>
-
- #include <assert.h>
- #include <string.h>
-
-
- void CBS_init(CBS *cbs, const uint8_t *data, size_t len) {
- cbs->data = data;
- cbs->len = 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;
- }
-
- 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) {
- if (*out_ptr != NULL) {
- OPENSSL_free(*out_ptr);
- *out_ptr = NULL;
- }
- *out_len = 0;
-
- if (cbs->len == 0) {
- return 1;
- }
- *out_ptr = BUF_memdup(cbs->data, cbs->len);
- if (*out_ptr == NULL) {
- return 0;
- }
- *out_len = cbs->len;
- return 1;
- }
-
- int CBS_strdup(const CBS *cbs, char **out_ptr) {
- if (*out_ptr != NULL) {
- OPENSSL_free(*out_ptr);
- }
- *out_ptr = BUF_strndup((const char*)cbs->data, cbs->len);
- return (*out_ptr != NULL);
- }
-
- 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 CRYPTO_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 (!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);
- }
-
- static int cbs_get_asn1_element(CBS *cbs, CBS *out, unsigned *out_tag,
- size_t *out_header_len, unsigned depth,
- int *was_indefinite_len);
-
- /* cbs_get_asn1_indefinite_len sets |*out| to be a CBS that covers an
- * indefinite length element in |cbs| and advances |*in|. On entry, |cbs| will
- * not have had the tag and length byte removed. On exit, |*out| does not cover
- * the EOC element, but |*in| is skipped over it.
- *
- * The |depth| argument counts the number of times the code has recursed trying
- * to find an indefinite length. */
- static int cbs_get_asn1_indefinite_len(CBS *in, CBS *out, unsigned depth) {
- static const size_t kEOCLength = 2;
- size_t header_len;
- unsigned tag;
- int was_indefinite_len;
- CBS orig = *in, child;
-
- if (!CBS_skip(in, 2 /* tag plus 0x80 byte for indefinite len */)) {
- return 0;
- }
-
- for (;;) {
- if (!cbs_get_asn1_element(in, &child, &tag, &header_len, depth + 1,
- &was_indefinite_len)) {
- return 0;
- }
-
- if (!was_indefinite_len && CBS_len(&child) == kEOCLength &&
- header_len == kEOCLength && tag == 0) {
- break;
- }
- }
-
- return CBS_get_bytes(&orig, out, CBS_len(&orig) - CBS_len(in) - kEOCLength);
- }
-
- /* MAX_DEPTH the maximum number of levels of indefinite lengths that we'll
- * support. */
- #define MAX_DEPTH 64
-
- static int cbs_get_asn1_element(CBS *cbs, CBS *out, unsigned *out_tag,
- size_t *out_header_len, unsigned depth,
- int *was_indefinite_len) {
- uint8_t tag, length_byte;
- CBS header = *cbs;
- if (!CBS_get_u8(&header, &tag) ||
- !CBS_get_u8(&header, &length_byte)) {
- return 0;
- }
-
- if ((tag & 0x1f) == 0x1f) {
- /* Long form tags are not supported. */
- return 0;
- }
-
- *out_tag = tag;
- if (was_indefinite_len) {
- *was_indefinite_len = 0;
- }
-
- size_t len;
- if ((length_byte & 0x80) == 0) {
- /* Short form length. */
- len = ((size_t) length_byte) + 2;
- *out_header_len = 2;
- } else {
- /* Long form length. */
- const size_t num_bytes = length_byte & 0x7f;
- uint32_t len32;
-
- if (depth < MAX_DEPTH && num_bytes == 0) {
- /* indefinite length */
- *out_header_len = 2;
- if (was_indefinite_len) {
- *was_indefinite_len = 1;
- }
- return cbs_get_asn1_indefinite_len(cbs, out, depth);
- }
-
- if (num_bytes == 0 || num_bytes > 4) {
- return 0;
- }
- if (!cbs_get_u(&header, &len32, num_bytes)) {
- return 0;
- }
- if (len32 < 128) {
- /* Length should have used short-form encoding. */
- 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;
- *out_header_len = 2 + num_bytes;
- }
-
- return CBS_get_bytes(cbs, out, len);
- }
-
- static int cbs_get_asn1(CBS *cbs, CBS *out, unsigned tag_value, int ber,
- int skip_header) {
- size_t header_len;
- unsigned tag;
- CBS throwaway;
-
- if (out == NULL) {
- out = &throwaway;
- }
-
- if (!cbs_get_asn1_element(cbs, out, &tag, &header_len, ber ? 0 : MAX_DEPTH,
- NULL) ||
- tag != tag_value) {
- return 0;
- }
-
- if (skip_header && !CBS_skip(out, header_len)) {
- assert(0);
- return 0;
- }
-
- return 1;
- }
-
- int CBS_get_asn1(CBS *cbs, CBS *out, unsigned tag_value) {
- return cbs_get_asn1(cbs, out, tag_value, 0 /* DER */,
- 1 /* skip header */);
- }
-
- int CBS_get_asn1_ber(CBS *cbs, CBS *out, unsigned tag_value) {
- return cbs_get_asn1(cbs, out, tag_value, 1 /* BER */,
- 1 /* skip header */);
- }
-
- int CBS_get_asn1_element(CBS *cbs, CBS *out, unsigned tag_value) {
- return cbs_get_asn1(cbs, out, tag_value, 0 /* DER */,
- 0 /* include header */);
- }
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