1/* Copyright (c) 2014, Google Inc.
2 *
3 * Permission to use, copy, modify, and/or distribute this software for any
4 * purpose with or without fee is hereby granted, provided that the above
5 * copyright notice and this permission notice appear in all copies.
6 *
7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
14
15#include <openssl/bytestring.h>
16
17#include <assert.h>
18#include <string.h>
19
20#include "internal.h"
21#include "../internal.h"
22
23
24// kMaxDepth is a just a sanity limit. The code should be such that the length
25// of the input being processes always decreases. None the less, a very large
26// input could otherwise cause the stack to overflow.
27static const unsigned kMaxDepth = 2048;
28
29// is_string_type returns one if |tag| is a string type and zero otherwise. It
30// ignores the constructed bit.
31static int is_string_type(unsigned tag) {
32 switch (tag & ~CBS_ASN1_CONSTRUCTED) {
33 case CBS_ASN1_BITSTRING:
34 case CBS_ASN1_OCTETSTRING:
35 case CBS_ASN1_UTF8STRING:
36 case CBS_ASN1_NUMERICSTRING:
37 case CBS_ASN1_PRINTABLESTRING:
38 case CBS_ASN1_T61STRING:
39 case CBS_ASN1_VIDEOTEXSTRING:
40 case CBS_ASN1_IA5STRING:
41 case CBS_ASN1_GRAPHICSTRING:
42 case CBS_ASN1_VISIBLESTRING:
43 case CBS_ASN1_GENERALSTRING:
44 case CBS_ASN1_UNIVERSALSTRING:
45 case CBS_ASN1_BMPSTRING:
46 return 1;
47 default:
48 return 0;
49 }
50}
51
52// cbs_find_ber walks an ASN.1 structure in |orig_in| and sets |*ber_found|
53// depending on whether an indefinite length element or constructed string was
54// found. The value of |orig_in| is not changed. It returns one on success (i.e.
55// |*ber_found| was set) and zero on error.
56static int cbs_find_ber(const CBS *orig_in, char *ber_found, unsigned depth) {
57 CBS in;
58
59 if (depth > kMaxDepth) {
60 return 0;
61 }
62
63 CBS_init(&in, CBS_data(orig_in), CBS_len(orig_in));
64 *ber_found = 0;
65
66 while (CBS_len(&in) > 0) {
67 CBS contents;
68 unsigned tag;
69 size_t header_len;
70
71 if (!CBS_get_any_ber_asn1_element(&in, &contents, &tag, &header_len)) {
72 return 0;
73 }
74 if (CBS_len(&contents) == header_len &&
75 header_len > 0 &&
76 CBS_data(&contents)[header_len-1] == 0x80) {
77 // Found an indefinite-length element.
78 *ber_found = 1;
79 return 1;
80 }
81 if (tag & CBS_ASN1_CONSTRUCTED) {
82 if (is_string_type(tag)) {
83 // Constructed strings are only legal in BER and require conversion.
84 *ber_found = 1;
85 return 1;
86 }
87 if (!CBS_skip(&contents, header_len) ||
88 !cbs_find_ber(&contents, ber_found, depth + 1)) {
89 return 0;
90 }
91 }
92 }
93
94 return 1;
95}
96
97// is_eoc returns true if |header_len| and |contents|, as returned by
98// |CBS_get_any_ber_asn1_element|, indicate an "end of contents" (EOC) value.
99static char is_eoc(size_t header_len, CBS *contents) {
100 return header_len == 2 && CBS_len(contents) == 2 &&
101 OPENSSL_memcmp(CBS_data(contents), "\x00\x00", 2) == 0;
102}
103
104// cbs_convert_ber reads BER data from |in| and writes DER data to |out|. If
105// |string_tag| is non-zero, then all elements must match |string_tag| up to the
106// constructed bit and primitive element bodies are written to |out| without
107// element headers. This is used when concatenating the fragments of a
108// constructed string. If |looking_for_eoc| is set then any EOC elements found
109// will cause the function to return after consuming it. It returns one on
110// success and zero on error.
111static int cbs_convert_ber(CBS *in, CBB *out, unsigned string_tag,
112 char looking_for_eoc, unsigned depth) {
113 assert(!(string_tag & CBS_ASN1_CONSTRUCTED));
114
115 if (depth > kMaxDepth) {
116 return 0;
117 }
118
119 while (CBS_len(in) > 0) {
120 CBS contents;
121 unsigned tag, child_string_tag = string_tag;
122 size_t header_len;
123 CBB *out_contents, out_contents_storage;
124
125 if (!CBS_get_any_ber_asn1_element(in, &contents, &tag, &header_len)) {
126 return 0;
127 }
128
129 if (is_eoc(header_len, &contents)) {
130 return looking_for_eoc;
131 }
132
133 if (string_tag != 0) {
134 // This is part of a constructed string. All elements must match
135 // |string_tag| up to the constructed bit and get appended to |out|
136 // without a child element.
137 if ((tag & ~CBS_ASN1_CONSTRUCTED) != string_tag) {
138 return 0;
139 }
140 out_contents = out;
141 } else {
142 unsigned out_tag = tag;
143 if ((tag & CBS_ASN1_CONSTRUCTED) && is_string_type(tag)) {
144 // If a constructed string, clear the constructed bit and inform
145 // children to concatenate bodies.
146 out_tag &= ~CBS_ASN1_CONSTRUCTED;
147 child_string_tag = out_tag;
148 }
149 if (!CBB_add_asn1(out, &out_contents_storage, out_tag)) {
150 return 0;
151 }
152 out_contents = &out_contents_storage;
153 }
154
155 if (CBS_len(&contents) == header_len && header_len > 0 &&
156 CBS_data(&contents)[header_len - 1] == 0x80) {
157 // This is an indefinite length element.
158 if (!cbs_convert_ber(in, out_contents, child_string_tag,
159 1 /* looking for eoc */, depth + 1) ||
160 !CBB_flush(out)) {
161 return 0;
162 }
163 continue;
164 }
165
166 if (!CBS_skip(&contents, header_len)) {
167 return 0;
168 }
169
170 if (tag & CBS_ASN1_CONSTRUCTED) {
171 // Recurse into children.
172 if (!cbs_convert_ber(&contents, out_contents, child_string_tag,
173 0 /* not looking for eoc */, depth + 1)) {
174 return 0;
175 }
176 } else {
177 // Copy primitive contents as-is.
178 if (!CBB_add_bytes(out_contents, CBS_data(&contents),
179 CBS_len(&contents))) {
180 return 0;
181 }
182 }
183
184 if (!CBB_flush(out)) {
185 return 0;
186 }
187 }
188
189 return looking_for_eoc == 0;
190}
191
192int CBS_asn1_ber_to_der(CBS *in, CBS *out, uint8_t **out_storage) {
193 CBB cbb;
194
195 // First, do a quick walk to find any indefinite-length elements. Most of the
196 // time we hope that there aren't any and thus we can quickly return.
197 char conversion_needed;
198 if (!cbs_find_ber(in, &conversion_needed, 0)) {
199 return 0;
200 }
201
202 if (!conversion_needed) {
203 if (!CBS_get_any_asn1_element(in, out, NULL, NULL)) {
204 return 0;
205 }
206 *out_storage = NULL;
207 return 1;
208 }
209
210 size_t len;
211 if (!CBB_init(&cbb, CBS_len(in)) ||
212 !cbs_convert_ber(in, &cbb, 0, 0, 0) ||
213 !CBB_finish(&cbb, out_storage, &len)) {
214 CBB_cleanup(&cbb);
215 return 0;
216 }
217
218 CBS_init(out, *out_storage, len);
219 return 1;
220}
221
222int CBS_get_asn1_implicit_string(CBS *in, CBS *out, uint8_t **out_storage,
223 unsigned outer_tag, unsigned inner_tag) {
224 assert(!(outer_tag & CBS_ASN1_CONSTRUCTED));
225 assert(!(inner_tag & CBS_ASN1_CONSTRUCTED));
226 assert(is_string_type(inner_tag));
227
228 if (CBS_peek_asn1_tag(in, outer_tag)) {
229 // Normal implicitly-tagged string.
230 *out_storage = NULL;
231 return CBS_get_asn1(in, out, outer_tag);
232 }
233
234 // Otherwise, try to parse an implicitly-tagged constructed string.
235 // |CBS_asn1_ber_to_der| is assumed to have run, so only allow one level deep
236 // of nesting.
237 CBB result;
238 CBS child;
239 if (!CBB_init(&result, CBS_len(in)) ||
240 !CBS_get_asn1(in, &child, outer_tag | CBS_ASN1_CONSTRUCTED)) {
241 goto err;
242 }
243
244 while (CBS_len(&child) > 0) {
245 CBS chunk;
246 if (!CBS_get_asn1(&child, &chunk, inner_tag) ||
247 !CBB_add_bytes(&result, CBS_data(&chunk), CBS_len(&chunk))) {
248 goto err;
249 }
250 }
251
252 uint8_t *data;
253 size_t len;
254 if (!CBB_finish(&result, &data, &len)) {
255 goto err;
256 }
257
258 CBS_init(out, data, len);
259 *out_storage = data;
260 return 1;
261
262err:
263 CBB_cleanup(&result);
264 return 0;
265}
266