| /* 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/bytestring.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; |
| |
| /* 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_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; |
| } |
| |
| /* is_primitive_type returns true if |tag| likely a primitive type. Normally |
| * one can just test the "constructed" bit in the tag but, in BER, even |
| * primitive tags can have the constructed bit if they have indefinite |
| * length. */ |
| static char is_primitive_type(unsigned tag) { |
| return (tag & 0xc0) == 0 && |
| (tag & 0x1f) != (CBS_ASN1_SEQUENCE & 0x1f) && |
| (tag & 0x1f) != (CBS_ASN1_SET & 0x1f); |
| } |
| |
| /* is_eoc returns true if |header_len| and |contents|, as returned by |
| * |CBS_get_any_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 && |
| memcmp(CBS_data(contents), "\x00\x00", 2) == 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_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, primtive |
| * 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_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; |
| } |
| |
| 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; |
| } |
| |
| CBB_init(&cbb, CBS_len(in)); |
| if (!cbs_convert_ber(in, &cbb, 0, 0, 0)) { |
| CBB_cleanup(&cbb); |
| return 0; |
| } |
| |
| return CBB_finish(&cbb, out, out_len); |
| } |
