/* 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_grpc/bytestring.h> #include <assert.h> #include <string.h> #include "internal.h" #include "../internal.h" // kMaxDepth is a just a sanity limit. The code should be such that the length // of the input being processes always decreases. None the less, a very large // input could otherwise cause the stack to overflow. static const unsigned kMaxDepth = 2048; // is_string_type returns one if |tag| is a string type and zero otherwise. It // ignores the constructed bit. static int is_string_type(unsigned tag) { // While BER supports constructed BIT STRINGS, OpenSSL misparses them. To // avoid acting on an ambiguous input, we do not support constructed BIT // STRINGS. See https://github.com/openssl/openssl/issues/12810. switch (tag & ~CBS_ASN1_CONSTRUCTED) { case CBS_ASN1_OCTETSTRING: case CBS_ASN1_UTF8STRING: case CBS_ASN1_NUMERICSTRING: case CBS_ASN1_PRINTABLESTRING: case CBS_ASN1_T61STRING: case CBS_ASN1_VIDEOTEXSTRING: case CBS_ASN1_IA5STRING: case CBS_ASN1_GRAPHICSTRING: case CBS_ASN1_VISIBLESTRING: case CBS_ASN1_GENERALSTRING: case CBS_ASN1_UNIVERSALSTRING: case CBS_ASN1_BMPSTRING: return 1; default: return 0; } } // 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, int *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, ber_found)) { return 0; } if (*ber_found) { 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; } // is_eoc returns true if |header_len| and |contents|, as returned by // |CBS_get_any_ber_asn1_element|, indicate an "end of contents" (EOC) value. static char is_eoc(size_t header_len, CBS *contents) { return header_len == 2 && CBS_len(contents) == 2 && OPENSSL_memcmp(CBS_data(contents), "\x00\x00", 2) == 0; } // 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; int ber_found; CBB *out_contents, out_contents_storage; if (!CBS_get_any_ber_asn1_element(in, &contents, &tag, &header_len, &ber_found)) { 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; } int CBS_asn1_ber_to_der(CBS *in, CBS *out, uint8_t **out_storage) { 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. int conversion_needed; if (!cbs_find_ber(in, &conversion_needed, 0)) { return 0; } if (!conversion_needed) { if (!CBS_get_any_asn1_element(in, out, NULL, NULL)) { return 0; } *out_storage = NULL; return 1; } size_t len; if (!CBB_init(&cbb, CBS_len(in)) || !cbs_convert_ber(in, &cbb, 0, 0, 0) || !CBB_finish(&cbb, out_storage, &len)) { CBB_cleanup(&cbb); return 0; } CBS_init(out, *out_storage, len); return 1; } int CBS_get_asn1_implicit_string(CBS *in, CBS *out, uint8_t **out_storage, unsigned outer_tag, unsigned inner_tag) { assert(!(outer_tag & CBS_ASN1_CONSTRUCTED)); assert(!(inner_tag & CBS_ASN1_CONSTRUCTED)); assert(is_string_type(inner_tag)); if (CBS_peek_asn1_tag(in, outer_tag)) { // Normal implicitly-tagged string. *out_storage = NULL; return CBS_get_asn1(in, out, outer_tag); } // Otherwise, try to parse an implicitly-tagged constructed string. // |CBS_asn1_ber_to_der| is assumed to have run, so only allow one level deep // of nesting. CBB result; CBS child; if (!CBB_init(&result, CBS_len(in)) || !CBS_get_asn1(in, &child, outer_tag | CBS_ASN1_CONSTRUCTED)) { goto err; } while (CBS_len(&child) > 0) { CBS chunk; if (!CBS_get_asn1(&child, &chunk, inner_tag) || !CBB_add_bytes(&result, CBS_data(&chunk), CBS_len(&chunk))) { goto err; } } uint8_t *data; size_t len; if (!CBB_finish(&result, &data, &len)) { goto err; } CBS_init(out, data, len); *out_storage = data; return 1; err: CBB_cleanup(&result); return 0; }