1 /** \file asn1_helpers.c
2 *
3 * \brief Helper functions for tests that manipulate ASN.1 data.
4 */
5
6 /*
7 * Copyright The Mbed TLS Contributors
8 * SPDX-License-Identifier: Apache-2.0
9 *
10 * Licensed under the Apache License, Version 2.0 (the "License"); you may
11 * not use this file except in compliance with the License.
12 * You may obtain a copy of the License at
13 *
14 * http://www.apache.org/licenses/LICENSE-2.0
15 *
16 * Unless required by applicable law or agreed to in writing, software
17 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
18 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
19 * See the License for the specific language governing permissions and
20 * limitations under the License.
21 */
22
23 #include <test/helpers.h>
24 #include <test/macros.h>
25
26 #if defined(MBEDTLS_ASN1_PARSE_C)
27
28 #include <mbedtls/asn1.h>
29
mbedtls_test_asn1_skip_integer(unsigned char ** p,const unsigned char * end,size_t min_bits,size_t max_bits,int must_be_odd)30 int mbedtls_test_asn1_skip_integer(unsigned char **p, const unsigned char *end,
31 size_t min_bits, size_t max_bits,
32 int must_be_odd)
33 {
34 size_t len;
35 size_t actual_bits;
36 unsigned char msb;
37 TEST_EQUAL(mbedtls_asn1_get_tag(p, end, &len,
38 MBEDTLS_ASN1_INTEGER),
39 0);
40
41 /* Check if the retrieved length doesn't extend the actual buffer's size.
42 * It is assumed here, that end >= p, which validates casting to size_t. */
43 TEST_ASSERT(len <= (size_t) (end - *p));
44
45 /* Tolerate a slight departure from DER encoding:
46 * - 0 may be represented by an empty string or a 1-byte string.
47 * - The sign bit may be used as a value bit. */
48 if ((len == 1 && (*p)[0] == 0) ||
49 (len > 1 && (*p)[0] == 0 && ((*p)[1] & 0x80) != 0)) {
50 ++(*p);
51 --len;
52 }
53 if (min_bits == 0 && len == 0) {
54 return 1;
55 }
56 msb = (*p)[0];
57 TEST_ASSERT(msb != 0);
58 actual_bits = 8 * (len - 1);
59 while (msb != 0) {
60 msb >>= 1;
61 ++actual_bits;
62 }
63 TEST_ASSERT(actual_bits >= min_bits);
64 TEST_ASSERT(actual_bits <= max_bits);
65 if (must_be_odd) {
66 TEST_ASSERT(((*p)[len-1] & 1) != 0);
67 }
68 *p += len;
69 return 1;
70 exit:
71 return 0;
72 }
73
74 #endif /* MBEDTLS_ASN1_PARSE_C */
75
