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;
}
/* 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;
}
/* 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;
}
