1*62c56f98SSadaf Ebrahimi /** \file asn1_helpers.c
2*62c56f98SSadaf Ebrahimi *
3*62c56f98SSadaf Ebrahimi * \brief Helper functions for tests that manipulate ASN.1 data.
4*62c56f98SSadaf Ebrahimi */
5*62c56f98SSadaf Ebrahimi
6*62c56f98SSadaf Ebrahimi /*
7*62c56f98SSadaf Ebrahimi * Copyright The Mbed TLS Contributors
8*62c56f98SSadaf Ebrahimi * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
9*62c56f98SSadaf Ebrahimi */
10*62c56f98SSadaf Ebrahimi
11*62c56f98SSadaf Ebrahimi #include <test/helpers.h>
12*62c56f98SSadaf Ebrahimi #include <test/macros.h>
13*62c56f98SSadaf Ebrahimi
14*62c56f98SSadaf Ebrahimi #if defined(MBEDTLS_ASN1_PARSE_C)
15*62c56f98SSadaf Ebrahimi
16*62c56f98SSadaf Ebrahimi #include <mbedtls/asn1.h>
17*62c56f98SSadaf Ebrahimi
mbedtls_test_asn1_skip_integer(unsigned char ** p,const unsigned char * end,size_t min_bits,size_t max_bits,int must_be_odd)18*62c56f98SSadaf Ebrahimi int mbedtls_test_asn1_skip_integer(unsigned char **p, const unsigned char *end,
19*62c56f98SSadaf Ebrahimi size_t min_bits, size_t max_bits,
20*62c56f98SSadaf Ebrahimi int must_be_odd)
21*62c56f98SSadaf Ebrahimi {
22*62c56f98SSadaf Ebrahimi size_t len;
23*62c56f98SSadaf Ebrahimi size_t actual_bits;
24*62c56f98SSadaf Ebrahimi unsigned char msb;
25*62c56f98SSadaf Ebrahimi TEST_EQUAL(mbedtls_asn1_get_tag(p, end, &len,
26*62c56f98SSadaf Ebrahimi MBEDTLS_ASN1_INTEGER),
27*62c56f98SSadaf Ebrahimi 0);
28*62c56f98SSadaf Ebrahimi
29*62c56f98SSadaf Ebrahimi /* Check if the retrieved length doesn't extend the actual buffer's size.
30*62c56f98SSadaf Ebrahimi * It is assumed here, that end >= p, which validates casting to size_t. */
31*62c56f98SSadaf Ebrahimi TEST_ASSERT(len <= (size_t) (end - *p));
32*62c56f98SSadaf Ebrahimi
33*62c56f98SSadaf Ebrahimi /* Tolerate a slight departure from DER encoding:
34*62c56f98SSadaf Ebrahimi * - 0 may be represented by an empty string or a 1-byte string.
35*62c56f98SSadaf Ebrahimi * - The sign bit may be used as a value bit. */
36*62c56f98SSadaf Ebrahimi if ((len == 1 && (*p)[0] == 0) ||
37*62c56f98SSadaf Ebrahimi (len > 1 && (*p)[0] == 0 && ((*p)[1] & 0x80) != 0)) {
38*62c56f98SSadaf Ebrahimi ++(*p);
39*62c56f98SSadaf Ebrahimi --len;
40*62c56f98SSadaf Ebrahimi }
41*62c56f98SSadaf Ebrahimi if (min_bits == 0 && len == 0) {
42*62c56f98SSadaf Ebrahimi return 1;
43*62c56f98SSadaf Ebrahimi }
44*62c56f98SSadaf Ebrahimi msb = (*p)[0];
45*62c56f98SSadaf Ebrahimi TEST_ASSERT(msb != 0);
46*62c56f98SSadaf Ebrahimi actual_bits = 8 * (len - 1);
47*62c56f98SSadaf Ebrahimi while (msb != 0) {
48*62c56f98SSadaf Ebrahimi msb >>= 1;
49*62c56f98SSadaf Ebrahimi ++actual_bits;
50*62c56f98SSadaf Ebrahimi }
51*62c56f98SSadaf Ebrahimi TEST_ASSERT(actual_bits >= min_bits);
52*62c56f98SSadaf Ebrahimi TEST_ASSERT(actual_bits <= max_bits);
53*62c56f98SSadaf Ebrahimi if (must_be_odd) {
54*62c56f98SSadaf Ebrahimi TEST_ASSERT(((*p)[len-1] & 1) != 0);
55*62c56f98SSadaf Ebrahimi }
56*62c56f98SSadaf Ebrahimi *p += len;
57*62c56f98SSadaf Ebrahimi return 1;
58*62c56f98SSadaf Ebrahimi exit:
59*62c56f98SSadaf Ebrahimi return 0;
60*62c56f98SSadaf Ebrahimi }
61*62c56f98SSadaf Ebrahimi
62*62c56f98SSadaf Ebrahimi #endif /* MBEDTLS_ASN1_PARSE_C */
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