1d9e397b599b13d642138480a28c14db7a136bf0Adam Langley/* Copyright (c) 2014, Google Inc. 2d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * 3d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * Permission to use, copy, modify, and/or distribute this software for any 4d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * purpose with or without fee is hereby granted, provided that the above 5d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * copyright notice and this permission notice appear in all copies. 6d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * 7d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 8d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 9d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 10d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 11d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION 12d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN 13d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ 14d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 15d9e397b599b13d642138480a28c14db7a136bf0Adam Langley#include <openssl/bytestring.h> 16d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 17d9e397b599b13d642138480a28c14db7a136bf0Adam Langley#include <string.h> 18d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 19d9e397b599b13d642138480a28c14db7a136bf0Adam Langley#include "internal.h" 20d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 21d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 22d9e397b599b13d642138480a28c14db7a136bf0Adam Langley/* kMaxDepth is a just a sanity limit. The code should be such that the length 23d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * of the input being processes always decreases. None the less, a very large 24d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * input could otherwise cause the stack to overflow. */ 25d9e397b599b13d642138480a28c14db7a136bf0Adam Langleystatic const unsigned kMaxDepth = 2048; 26d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 27d9e397b599b13d642138480a28c14db7a136bf0Adam Langley/* cbs_find_ber walks an ASN.1 structure in |orig_in| and sets |*ber_found| 28d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * depending on whether an indefinite length element was found. The value of 29d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * |in| is not changed. It returns one on success (i.e. |*ber_found| was set) 30d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * and zero on error. */ 31d9e397b599b13d642138480a28c14db7a136bf0Adam Langleystatic int cbs_find_ber(CBS *orig_in, char *ber_found, unsigned depth) { 32d9e397b599b13d642138480a28c14db7a136bf0Adam Langley CBS in; 33d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 34d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (depth > kMaxDepth) { 35d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 36d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 37d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 38d9e397b599b13d642138480a28c14db7a136bf0Adam Langley CBS_init(&in, CBS_data(orig_in), CBS_len(orig_in)); 39d9e397b599b13d642138480a28c14db7a136bf0Adam Langley *ber_found = 0; 40d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 41d9e397b599b13d642138480a28c14db7a136bf0Adam Langley while (CBS_len(&in) > 0) { 42d9e397b599b13d642138480a28c14db7a136bf0Adam Langley CBS contents; 43d9e397b599b13d642138480a28c14db7a136bf0Adam Langley unsigned tag; 44d9e397b599b13d642138480a28c14db7a136bf0Adam Langley size_t header_len; 45d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 4653b272a2813a0b11f107d77100ff8805ada8fbd2Adam Langley if (!CBS_get_any_ber_asn1_element(&in, &contents, &tag, &header_len)) { 47d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 48d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 49d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (CBS_len(&contents) == header_len && 50d9e397b599b13d642138480a28c14db7a136bf0Adam Langley header_len > 0 && 51d9e397b599b13d642138480a28c14db7a136bf0Adam Langley CBS_data(&contents)[header_len-1] == 0x80) { 52d9e397b599b13d642138480a28c14db7a136bf0Adam Langley *ber_found = 1; 53d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 1; 54d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 55d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (tag & CBS_ASN1_CONSTRUCTED) { 56d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (!CBS_skip(&contents, header_len) || 57d9e397b599b13d642138480a28c14db7a136bf0Adam Langley !cbs_find_ber(&contents, ber_found, depth + 1)) { 58d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 59d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 60d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 61d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 62d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 63d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 1; 64d9e397b599b13d642138480a28c14db7a136bf0Adam Langley} 65d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 66d9e397b599b13d642138480a28c14db7a136bf0Adam Langley/* is_primitive_type returns true if |tag| likely a primitive type. Normally 67d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * one can just test the "constructed" bit in the tag but, in BER, even 68d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * primitive tags can have the constructed bit if they have indefinite 69d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * length. */ 70d9e397b599b13d642138480a28c14db7a136bf0Adam Langleystatic char is_primitive_type(unsigned tag) { 71d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return (tag & 0xc0) == 0 && 72d9e397b599b13d642138480a28c14db7a136bf0Adam Langley (tag & 0x1f) != (CBS_ASN1_SEQUENCE & 0x1f) && 73d9e397b599b13d642138480a28c14db7a136bf0Adam Langley (tag & 0x1f) != (CBS_ASN1_SET & 0x1f); 74d9e397b599b13d642138480a28c14db7a136bf0Adam Langley} 75d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 76d9e397b599b13d642138480a28c14db7a136bf0Adam Langley/* is_eoc returns true if |header_len| and |contents|, as returned by 7753b272a2813a0b11f107d77100ff8805ada8fbd2Adam Langley * |CBS_get_any_ber_asn1_element|, indicate an "end of contents" (EOC) value. */ 78d9e397b599b13d642138480a28c14db7a136bf0Adam Langleystatic char is_eoc(size_t header_len, CBS *contents) { 79d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return header_len == 2 && CBS_len(contents) == 2 && 80d9e397b599b13d642138480a28c14db7a136bf0Adam Langley memcmp(CBS_data(contents), "\x00\x00", 2) == 0; 81d9e397b599b13d642138480a28c14db7a136bf0Adam Langley} 82d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 83d9e397b599b13d642138480a28c14db7a136bf0Adam Langley/* cbs_convert_ber reads BER data from |in| and writes DER data to |out|. If 84d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * |squash_header| is set then the top-level of elements from |in| will not 85d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * have their headers written. This is used when concatenating the fragments of 86d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * an indefinite length, primitive value. If |looking_for_eoc| is set then any 87d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * EOC elements found will cause the function to return after consuming it. 88d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * It returns one on success and zero on error. */ 89d9e397b599b13d642138480a28c14db7a136bf0Adam Langleystatic int cbs_convert_ber(CBS *in, CBB *out, char squash_header, 90d9e397b599b13d642138480a28c14db7a136bf0Adam Langley char looking_for_eoc, unsigned depth) { 91d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (depth > kMaxDepth) { 92d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 93d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 94d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 95d9e397b599b13d642138480a28c14db7a136bf0Adam Langley while (CBS_len(in) > 0) { 96d9e397b599b13d642138480a28c14db7a136bf0Adam Langley CBS contents; 97d9e397b599b13d642138480a28c14db7a136bf0Adam Langley unsigned tag; 98d9e397b599b13d642138480a28c14db7a136bf0Adam Langley size_t header_len; 99d9e397b599b13d642138480a28c14db7a136bf0Adam Langley CBB *out_contents, out_contents_storage; 100d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 10153b272a2813a0b11f107d77100ff8805ada8fbd2Adam Langley if (!CBS_get_any_ber_asn1_element(in, &contents, &tag, &header_len)) { 102d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 103d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 104d9e397b599b13d642138480a28c14db7a136bf0Adam Langley out_contents = out; 105d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 106d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (CBS_len(&contents) == header_len) { 107d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (is_eoc(header_len, &contents)) { 108d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return looking_for_eoc; 109d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 110d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 111d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (header_len > 0 && CBS_data(&contents)[header_len - 1] == 0x80) { 112d9e397b599b13d642138480a28c14db7a136bf0Adam Langley /* This is an indefinite length element. If it's a SEQUENCE or SET then 113d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * we just need to write the out the contents as normal, but with a 114d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * concrete length prefix. 115d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * 116d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * If it's a something else then the contents will be a series of BER 117d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * elements of the same type which need to be concatenated. */ 118d9e397b599b13d642138480a28c14db7a136bf0Adam Langley const char context_specific = (tag & 0xc0) == 0x80; 119d9e397b599b13d642138480a28c14db7a136bf0Adam Langley char squash_child_headers = is_primitive_type(tag); 120d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 121d9e397b599b13d642138480a28c14db7a136bf0Adam Langley /* This is a hack, but it sufficies to handle NSS's output. If we find 122d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * an indefinite length, context-specific tag with a definite, primtive 123d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * tag inside it, then we assume that the context-specific tag is 124d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * implicit and the tags within are fragments of a primitive type that 125d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * need to be concatenated. */ 126d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (context_specific && (tag & CBS_ASN1_CONSTRUCTED)) { 127d9e397b599b13d642138480a28c14db7a136bf0Adam Langley CBS in_copy, inner_contents; 128d9e397b599b13d642138480a28c14db7a136bf0Adam Langley unsigned inner_tag; 129d9e397b599b13d642138480a28c14db7a136bf0Adam Langley size_t inner_header_len; 130d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 131d9e397b599b13d642138480a28c14db7a136bf0Adam Langley CBS_init(&in_copy, CBS_data(in), CBS_len(in)); 13253b272a2813a0b11f107d77100ff8805ada8fbd2Adam Langley if (!CBS_get_any_ber_asn1_element(&in_copy, &inner_contents, 13353b272a2813a0b11f107d77100ff8805ada8fbd2Adam Langley &inner_tag, &inner_header_len)) { 134d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 135d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 136d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (CBS_len(&inner_contents) > inner_header_len && 137d9e397b599b13d642138480a28c14db7a136bf0Adam Langley is_primitive_type(inner_tag)) { 138d9e397b599b13d642138480a28c14db7a136bf0Adam Langley squash_child_headers = 1; 139d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 140d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 141d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 142d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (!squash_header) { 143d9e397b599b13d642138480a28c14db7a136bf0Adam Langley unsigned out_tag = tag; 144d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (squash_child_headers) { 145d9e397b599b13d642138480a28c14db7a136bf0Adam Langley out_tag &= ~CBS_ASN1_CONSTRUCTED; 146d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 147d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (!CBB_add_asn1(out, &out_contents_storage, out_tag)) { 148d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 149d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 150d9e397b599b13d642138480a28c14db7a136bf0Adam Langley out_contents = &out_contents_storage; 151d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 152d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 153d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (!cbs_convert_ber(in, out_contents, 154d9e397b599b13d642138480a28c14db7a136bf0Adam Langley squash_child_headers, 155d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 1 /* looking for eoc */, depth + 1)) { 156d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 157d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 158d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (out_contents != out && !CBB_flush(out)) { 159d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 160d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 161d9e397b599b13d642138480a28c14db7a136bf0Adam Langley continue; 162d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 163d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 164d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 165d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (!squash_header) { 166d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (!CBB_add_asn1(out, &out_contents_storage, tag)) { 167d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 168d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 169d9e397b599b13d642138480a28c14db7a136bf0Adam Langley out_contents = &out_contents_storage; 170d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 171d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 172d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (!CBS_skip(&contents, header_len)) { 173d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 174d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 175d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 176d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (tag & CBS_ASN1_CONSTRUCTED) { 177d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (!cbs_convert_ber(&contents, out_contents, 0 /* don't squash header */, 178d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 0 /* not looking for eoc */, depth + 1)) { 179d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 180d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 181d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } else { 182d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (!CBB_add_bytes(out_contents, CBS_data(&contents), 183d9e397b599b13d642138480a28c14db7a136bf0Adam Langley CBS_len(&contents))) { 184d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 185d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 186d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 187d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 188d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (out_contents != out && !CBB_flush(out)) { 189d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 190d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 191d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 192d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 193d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return looking_for_eoc == 0; 194d9e397b599b13d642138480a28c14db7a136bf0Adam Langley} 195d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 196d9e397b599b13d642138480a28c14db7a136bf0Adam Langleyint CBS_asn1_ber_to_der(CBS *in, uint8_t **out, size_t *out_len) { 197d9e397b599b13d642138480a28c14db7a136bf0Adam Langley CBB cbb; 198d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 199d9e397b599b13d642138480a28c14db7a136bf0Adam Langley /* First, do a quick walk to find any indefinite-length elements. Most of the 200d9e397b599b13d642138480a28c14db7a136bf0Adam Langley * time we hope that there aren't any and thus we can quickly return. */ 201d9e397b599b13d642138480a28c14db7a136bf0Adam Langley char conversion_needed; 202d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (!cbs_find_ber(in, &conversion_needed, 0)) { 203d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 204d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 205d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 206d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (!conversion_needed) { 207d9e397b599b13d642138480a28c14db7a136bf0Adam Langley *out = NULL; 208d9e397b599b13d642138480a28c14db7a136bf0Adam Langley *out_len = 0; 209d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 1; 210d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 211d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 21253b272a2813a0b11f107d77100ff8805ada8fbd2Adam Langley if (!CBB_init(&cbb, CBS_len(in))) { 21353b272a2813a0b11f107d77100ff8805ada8fbd2Adam Langley return 0; 21453b272a2813a0b11f107d77100ff8805ada8fbd2Adam Langley } 215d9e397b599b13d642138480a28c14db7a136bf0Adam Langley if (!cbs_convert_ber(in, &cbb, 0, 0, 0)) { 216d9e397b599b13d642138480a28c14db7a136bf0Adam Langley CBB_cleanup(&cbb); 217d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return 0; 218d9e397b599b13d642138480a28c14db7a136bf0Adam Langley } 219d9e397b599b13d642138480a28c14db7a136bf0Adam Langley 220d9e397b599b13d642138480a28c14db7a136bf0Adam Langley return CBB_finish(&cbb, out, out_len); 221d9e397b599b13d642138480a28c14db7a136bf0Adam Langley} 222