/* 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;
}
/* 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;
}
/* 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, primitive
* 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;
}
