256 lines
7.1 KiB
C
256 lines
7.1 KiB
C
// Copyright (c) 2014, Google Inc.
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// SPDX-License-Identifier: ISC
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#include <openssl/bytestring.h>
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#include <assert.h>
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#include <string.h>
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#include "internal.h"
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// kMaxDepth limits the recursion depth to avoid overflowing the stack.
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static const uint32_t kMaxDepth = 128;
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// is_string_type returns one if |tag| is a string type and zero otherwise. It
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// ignores the constructed bit.
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static int is_string_type(CBS_ASN1_TAG tag) {
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// While BER supports constructed BIT STRINGS, OpenSSL misparses them. To
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// avoid acting on an ambiguous input, we do not support constructed BIT
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// STRINGS. See https://github.com/openssl/openssl/issues/12810.
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switch (tag & ~CBS_ASN1_CONSTRUCTED) {
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case CBS_ASN1_OCTETSTRING:
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case CBS_ASN1_UTF8STRING:
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case CBS_ASN1_NUMERICSTRING:
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case CBS_ASN1_PRINTABLESTRING:
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case CBS_ASN1_T61STRING:
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case CBS_ASN1_VIDEOTEXSTRING:
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case CBS_ASN1_IA5STRING:
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case CBS_ASN1_GRAPHICSTRING:
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case CBS_ASN1_VISIBLESTRING:
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case CBS_ASN1_GENERALSTRING:
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case CBS_ASN1_UNIVERSALSTRING:
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case CBS_ASN1_BMPSTRING:
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return 1;
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default:
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return 0;
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}
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}
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// cbs_find_ber walks an ASN.1 structure in |orig_in| and sets |*ber_found|
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// depending on whether an indefinite length element or constructed string was
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// found. The value of |orig_in| is not changed. It returns one on success (i.e.
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// |*ber_found| was set) and zero on error.
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static int cbs_find_ber(const CBS *orig_in, int *ber_found, uint32_t depth) {
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if (depth > kMaxDepth) {
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return 0;
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}
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CBS in = *orig_in;
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*ber_found = 0;
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while (CBS_len(&in) > 0) {
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CBS contents;
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CBS_ASN1_TAG tag;
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size_t header_len;
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int indefinite;
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if (!CBS_get_any_ber_asn1_element(&in, &contents, &tag, &header_len,
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ber_found, &indefinite)) {
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return 0;
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}
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if (*ber_found) {
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return 1;
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}
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if (tag & CBS_ASN1_CONSTRUCTED) {
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if (is_string_type(tag)) {
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// Constructed strings are only legal in BER and require conversion.
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*ber_found = 1;
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return 1;
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}
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if (!CBS_skip(&contents, header_len) ||
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!cbs_find_ber(&contents, ber_found, depth + 1)) {
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return 0;
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}
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if (*ber_found) {
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// We already found BER. No need to continue parsing.
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return 1;
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}
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}
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}
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return 1;
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}
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// cbs_get_eoc returns one if |cbs| begins with an "end of contents" (EOC) value
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// and zero otherwise. If an EOC was found, it advances |cbs| past it.
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static int cbs_get_eoc(CBS *cbs) {
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if (CBS_len(cbs) >= 2 &&
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CBS_data(cbs)[0] == 0 && CBS_data(cbs)[1] == 0) {
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return CBS_skip(cbs, 2);
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}
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return 0;
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}
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// cbs_convert_ber reads BER data from |in| and writes DER data to |out|. If
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// |string_tag| is non-zero, then all elements must match |string_tag| up to the
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// constructed bit and primitive element bodies are written to |out| without
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// element headers. This is used when concatenating the fragments of a
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// constructed string. If |looking_for_eoc| is set then any EOC elements found
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// will cause the function to return after consuming it. It returns one on
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// success and zero on error.
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static int cbs_convert_ber(CBS *in, CBB *out, CBS_ASN1_TAG string_tag,
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int looking_for_eoc, uint32_t depth) {
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assert(!(string_tag & CBS_ASN1_CONSTRUCTED));
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if (depth > kMaxDepth) {
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return 0;
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}
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while (CBS_len(in) > 0) {
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if (looking_for_eoc && cbs_get_eoc(in)) {
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return 1;
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}
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CBS contents;
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CBS_ASN1_TAG tag, child_string_tag = string_tag;
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size_t header_len;
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int indefinite;
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CBB *out_contents, out_contents_storage;
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if (!CBS_get_any_ber_asn1_element(in, &contents, &tag, &header_len,
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/*out_ber_found=*/NULL, &indefinite)) {
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return 0;
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}
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if (string_tag != 0) {
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// This is part of a constructed string. All elements must match
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// |string_tag| up to the constructed bit and get appended to |out|
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// without a child element.
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if ((tag & ~CBS_ASN1_CONSTRUCTED) != string_tag) {
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return 0;
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}
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out_contents = out;
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} else {
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CBS_ASN1_TAG out_tag = tag;
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if ((tag & CBS_ASN1_CONSTRUCTED) && is_string_type(tag)) {
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// If a constructed string, clear the constructed bit and inform
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// children to concatenate bodies.
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out_tag &= ~CBS_ASN1_CONSTRUCTED;
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child_string_tag = out_tag;
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}
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if (!CBB_add_asn1(out, &out_contents_storage, out_tag)) {
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return 0;
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}
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out_contents = &out_contents_storage;
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}
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if (indefinite) {
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if (!cbs_convert_ber(in, out_contents, child_string_tag,
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/*looking_for_eoc=*/1, depth + 1) ||
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!CBB_flush(out)) {
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return 0;
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}
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continue;
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}
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if (!CBS_skip(&contents, header_len)) {
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return 0;
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}
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if (tag & CBS_ASN1_CONSTRUCTED) {
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// Recurse into children.
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if (!cbs_convert_ber(&contents, out_contents, child_string_tag,
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/*looking_for_eoc=*/0, depth + 1)) {
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return 0;
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}
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} else {
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// Copy primitive contents as-is.
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if (!CBB_add_bytes(out_contents, CBS_data(&contents),
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CBS_len(&contents))) {
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return 0;
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}
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}
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if (!CBB_flush(out)) {
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return 0;
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}
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}
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return looking_for_eoc == 0;
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}
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int CBS_asn1_ber_to_der(CBS *in, CBS *out, uint8_t **out_storage) {
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CBB cbb;
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// First, do a quick walk to find any indefinite-length elements. Most of the
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// time we hope that there aren't any and thus we can quickly return.
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int conversion_needed;
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if (!cbs_find_ber(in, &conversion_needed, 0)) {
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return 0;
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}
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if (!conversion_needed) {
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if (!CBS_get_any_asn1_element(in, out, NULL, NULL)) {
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return 0;
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}
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*out_storage = NULL;
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return 1;
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}
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size_t len;
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if (!CBB_init(&cbb, CBS_len(in)) ||
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!cbs_convert_ber(in, &cbb, 0, 0, 0) ||
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!CBB_finish(&cbb, out_storage, &len)) {
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CBB_cleanup(&cbb);
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return 0;
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}
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CBS_init(out, *out_storage, len);
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return 1;
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}
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int CBS_get_asn1_implicit_string(CBS *in, CBS *out, uint8_t **out_storage,
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CBS_ASN1_TAG outer_tag,
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CBS_ASN1_TAG inner_tag) {
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assert(!(outer_tag & CBS_ASN1_CONSTRUCTED));
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assert(!(inner_tag & CBS_ASN1_CONSTRUCTED));
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assert(is_string_type(inner_tag));
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if (CBS_peek_asn1_tag(in, outer_tag)) {
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// Normal implicitly-tagged string.
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*out_storage = NULL;
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return CBS_get_asn1(in, out, outer_tag);
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}
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// Otherwise, try to parse an implicitly-tagged constructed string.
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// |CBS_asn1_ber_to_der| is assumed to have run, so only allow one level deep
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// of nesting.
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CBB result;
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CBS child;
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if (!CBB_init(&result, CBS_len(in)) ||
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!CBS_get_asn1(in, &child, outer_tag | CBS_ASN1_CONSTRUCTED)) {
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goto err;
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}
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while (CBS_len(&child) > 0) {
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CBS chunk;
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if (!CBS_get_asn1(&child, &chunk, inner_tag) ||
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!CBB_add_bytes(&result, CBS_data(&chunk), CBS_len(&chunk))) {
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goto err;
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}
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}
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uint8_t *data;
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size_t len;
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if (!CBB_finish(&result, &data, &len)) {
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goto err;
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}
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CBS_init(out, data, len);
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*out_storage = data;
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return 1;
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err:
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CBB_cleanup(&result);
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return 0;
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}
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