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 OR GPL-2.0-or-later
9 */
10
11 #include <test/helpers.h>
12 #include <test/macros.h>
13
14 #if defined(MBEDTLS_ASN1_PARSE_C)
15
16 #include <mbedtls/asn1.h>
17
18 #include <test/asn1_helpers.h>
19
mbedtls_test_asn1_skip_integer(unsigned char ** p,const unsigned char * end,size_t min_bits,size_t max_bits,int must_be_odd)20 int mbedtls_test_asn1_skip_integer(unsigned char **p, const unsigned char *end,
21 size_t min_bits, size_t max_bits,
22 int must_be_odd)
23 {
24 size_t len;
25 size_t actual_bits;
26 unsigned char msb;
27 TEST_EQUAL(mbedtls_asn1_get_tag(p, end, &len,
28 MBEDTLS_ASN1_INTEGER),
29 0);
30
31 /* Check if the retrieved length doesn't extend the actual buffer's size.
32 * It is assumed here, that end >= p, which validates casting to size_t. */
33 TEST_ASSERT(len <= (size_t) (end - *p));
34
35 /* Tolerate a slight departure from DER encoding:
36 * - 0 may be represented by an empty string or a 1-byte string.
37 * - The sign bit may be used as a value bit. */
38 if ((len == 1 && (*p)[0] == 0) ||
39 (len > 1 && (*p)[0] == 0 && ((*p)[1] & 0x80) != 0)) {
40 ++(*p);
41 --len;
42 }
43 if (min_bits == 0 && len == 0) {
44 return 1;
45 }
46 msb = (*p)[0];
47 TEST_ASSERT(msb != 0);
48 actual_bits = 8 * (len - 1);
49 while (msb != 0) {
50 msb >>= 1;
51 ++actual_bits;
52 }
53 TEST_ASSERT(actual_bits >= min_bits);
54 TEST_ASSERT(actual_bits <= max_bits);
55 if (must_be_odd) {
56 TEST_ASSERT(((*p)[len-1] & 1) != 0);
57 }
58 *p += len;
59 return 1;
60 exit:
61 return 0;
62 }
63
64 #endif /* MBEDTLS_ASN1_PARSE_C */
65
