blob: 639fdbbd28e9c0ddcebb4b0a8452ea6387e7ef4d [file] [log] [blame]
/* 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>
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;
}
void *CBS_memdup(const CBS *cbs) {
return BUF_memdup(cbs->data, cbs->len);
}
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 */);
}