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 {
51 ++( *p );
52 --len;
53 }
54 if( min_bits == 0 && len == 0 )
55 return( 1 );
56 msb = ( *p )[0];
57 TEST_ASSERT( msb != 0 );
58 actual_bits = 8 * ( len - 1 );
59 while( msb != 0 )
60 {
61 msb >>= 1;
62 ++actual_bits;
63 }
64 TEST_ASSERT( actual_bits >= min_bits );
65 TEST_ASSERT( actual_bits <= max_bits );
66 if( must_be_odd )
67 TEST_ASSERT( ( ( *p )[len-1] & 1 ) != 0 );
68 *p += len;
69 return( 1 );
70 exit:
71 return( 0 );
72 }
73
74 #endif /* MBEDTLS_ASN1_PARSE_C */
75