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authorcvs2svn <admin@example.com>2015-08-02 21:54:22 +0000
committercvs2svn <admin@example.com>2015-08-02 21:54:22 +0000
commited3760bf4be4a96a89233fb8f8b84a0d44725862 (patch)
tree5609c82060f75c53af0a7641d9b33a88574876cd /src/lib/libssl/bs_ber.c
parentf8b563fb5ba1524c821d37308f4e6abfc866bc3f (diff)
downloadopenbsd-OPENBSD_5_8_BASE.tar.gz
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This commit was manufactured by cvs2git to create tag 'OPENBSD_5_8_BASE'.OPENBSD_5_8_BASE
Diffstat (limited to 'src/lib/libssl/bs_ber.c')
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diff --git a/src/lib/libssl/bs_ber.c b/src/lib/libssl/bs_ber.c
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1/* $OpenBSD: bs_ber.c,v 1.8 2015/06/21 16:10:45 doug Exp $ */
2/*
3 * Copyright (c) 2014, Google Inc.
4 *
5 * Permission to use, copy, modify, and/or distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
12 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
14 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
15 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
16
17#include <string.h>
18
19#include <openssl/opensslconf.h>
20
21#include "bytestring.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.
27 */
28static const unsigned int kMaxDepth = 2048;
29
30/* Non-strict version that allows a relaxed DER with indefinite form. */
31static int
32cbs_nonstrict_get_any_asn1_element(CBS *cbs, CBS *out, unsigned int *out_tag,
33 size_t *out_header_len)
34{
35 return cbs_get_any_asn1_element_internal(cbs, out,
36 out_tag, out_header_len, 0);
37}
38
39/*
40 * cbs_find_indefinite walks an ASN.1 structure in |orig_in| and sets
41 * |*indefinite_found| depending on whether an indefinite length element was
42 * found. The value of |orig_in| is not modified.
43 *
44 * Returns one on success (i.e. |*indefinite_found| was set) and zero on error.
45 */
46static int
47cbs_find_indefinite(const CBS *orig_in, char *indefinite_found,
48 unsigned int depth)
49{
50 CBS in;
51
52 if (depth > kMaxDepth)
53 return 0;
54
55 CBS_init(&in, CBS_data(orig_in), CBS_len(orig_in));
56
57 while (CBS_len(&in) > 0) {
58 CBS contents;
59 unsigned int tag;
60 size_t header_len;
61
62 if (!cbs_nonstrict_get_any_asn1_element(&in, &contents, &tag,
63 &header_len))
64 return 0;
65
66 /* Indefinite form not allowed by DER. */
67 if (CBS_len(&contents) == header_len && header_len > 0 &&
68 CBS_data(&contents)[header_len - 1] == 0x80) {
69 *indefinite_found = 1;
70 return 1;
71 }
72 if (tag & CBS_ASN1_CONSTRUCTED) {
73 if (!CBS_skip(&contents, header_len) ||
74 !cbs_find_indefinite(&contents, indefinite_found,
75 depth + 1))
76 return 0;
77 }
78 }
79
80 *indefinite_found = 0;
81 return 1;
82}
83
84/*
85 * is_primitive_type returns true if |tag| likely a primitive type. Normally
86 * one can just test the "constructed" bit in the tag but, in BER, even
87 * primitive tags can have the constructed bit if they have indefinite
88 * length.
89 */
90static char
91is_primitive_type(unsigned int tag)
92{
93 return (tag & 0xc0) == 0 &&
94 (tag & 0x1f) != (CBS_ASN1_SEQUENCE & 0x1f) &&
95 (tag & 0x1f) != (CBS_ASN1_SET & 0x1f);
96}
97
98/*
99 * is_eoc returns true if |header_len| and |contents|, as returned by
100 * |cbs_nonstrict_get_any_asn1_element|, indicate an "end of contents" (EOC)
101 * value.
102 */
103static char
104is_eoc(size_t header_len, CBS *contents)
105{
106 return header_len == 2 && CBS_mem_equal(contents, "\x00\x00", 2);
107}
108
109/*
110 * cbs_convert_indefinite reads data with DER encoding (but relaxed to allow
111 * indefinite form) from |in| and writes definite form DER data to |out|. If
112 * |squash_header| is set then the top-level of elements from |in| will not
113 * have their headers written. This is used when concatenating the fragments of
114 * an indefinite length, primitive value. If |looking_for_eoc| is set then any
115 * EOC elements found will cause the function to return after consuming it.
116 * It returns one on success and zero on error.
117 */
118static int
119cbs_convert_indefinite(CBS *in, CBB *out, char squash_header,
120 char looking_for_eoc, unsigned int depth)
121{
122 if (depth > kMaxDepth)
123 return 0;
124
125 while (CBS_len(in) > 0) {
126 CBS contents;
127 unsigned int tag;
128 size_t header_len;
129 CBB *out_contents, out_contents_storage;
130
131 if (!cbs_nonstrict_get_any_asn1_element(in, &contents, &tag,
132 &header_len))
133 return 0;
134
135 out_contents = out;
136
137 if (CBS_len(&contents) == header_len) {
138 if (is_eoc(header_len, &contents))
139 return looking_for_eoc;
140
141 if (header_len > 0 &&
142 CBS_data(&contents)[header_len - 1] == 0x80) {
143 /*
144 * This is an indefinite length element. If
145 * it's a SEQUENCE or SET then we just need to
146 * write the out the contents as normal, but
147 * with a concrete length prefix.
148 *
149 * If it's a something else then the contents
150 * will be a series of DER elements of the same
151 * type which need to be concatenated.
152 */
153 const char context_specific = (tag & 0xc0)
154 == 0x80;
155 char squash_child_headers =
156 is_primitive_type(tag);
157
158 /*
159 * This is a hack, but it sufficies to handle
160 * NSS's output. If we find an indefinite
161 * length, context-specific tag with a definite,
162 * primtive tag inside it, then we assume that
163 * the context-specific tag is implicit and the
164 * tags within are fragments of a primitive type
165 * that need to be concatenated.
166 */
167 if (context_specific &&
168 (tag & CBS_ASN1_CONSTRUCTED)) {
169 CBS in_copy, inner_contents;
170 unsigned int inner_tag;
171 size_t inner_header_len;
172
173 CBS_init(&in_copy, CBS_data(in),
174 CBS_len(in));
175 if (!cbs_nonstrict_get_any_asn1_element(
176 &in_copy, &inner_contents,
177 &inner_tag, &inner_header_len))
178 return 0;
179
180 if (CBS_len(&inner_contents) >
181 inner_header_len &&
182 is_primitive_type(inner_tag))
183 squash_child_headers = 1;
184 }
185
186 if (!squash_header) {
187 unsigned int out_tag = tag;
188
189 if (squash_child_headers)
190 out_tag &=
191 ~CBS_ASN1_CONSTRUCTED;
192
193 if (!CBB_add_asn1(out,
194 &out_contents_storage, out_tag))
195 return 0;
196
197 out_contents = &out_contents_storage;
198 }
199
200 if (!cbs_convert_indefinite(in, out_contents,
201 squash_child_headers,
202 1 /* looking for eoc */, depth + 1))
203 return 0;
204
205 if (out_contents != out && !CBB_flush(out))
206 return 0;
207
208 continue;
209 }
210 }
211
212 if (!squash_header) {
213 if (!CBB_add_asn1(out, &out_contents_storage, tag))
214 return 0;
215
216 out_contents = &out_contents_storage;
217 }
218
219 if (!CBS_skip(&contents, header_len))
220 return 0;
221
222 if (tag & CBS_ASN1_CONSTRUCTED) {
223 if (!cbs_convert_indefinite(&contents, out_contents,
224 0 /* don't squash header */,
225 0 /* not looking for eoc */, depth + 1))
226 return 0;
227 } else {
228 if (!CBB_add_bytes(out_contents, CBS_data(&contents),
229 CBS_len(&contents)))
230 return 0;
231 }
232
233 if (out_contents != out && !CBB_flush(out))
234 return 0;
235 }
236
237 return looking_for_eoc == 0;
238}
239
240int
241CBS_asn1_indefinite_to_definite(CBS *in, uint8_t **out, size_t *out_len)
242{
243 CBB cbb;
244
245 /*
246 * First, do a quick walk to find any indefinite-length elements. Most
247 * of the time we hope that there aren't any and thus we can quickly
248 * return.
249 */
250 char conversion_needed;
251 if (!cbs_find_indefinite(in, &conversion_needed, 0))
252 return 0;
253
254 if (!conversion_needed) {
255 *out = NULL;
256 *out_len = 0;
257 return 1;
258 }
259
260 if (!CBB_init(&cbb, CBS_len(in)))
261 return 0;
262 if (!cbs_convert_indefinite(in, &cbb, 0, 0, 0)) {
263 CBB_cleanup(&cbb);
264 return 0;
265 }
266
267 return CBB_finish(&cbb, out, out_len);
268}
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