1 /*
2 * Example ECDSA program
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19
20 #include "mbedtls/build_info.h"
21
22 #include "mbedtls/platform.h"
23
24 #if defined(MBEDTLS_ECDSA_C) && \
25 defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_CTR_DRBG_C)
26 #include "mbedtls/entropy.h"
27 #include "mbedtls/ctr_drbg.h"
28 #include "mbedtls/ecdsa.h"
29 #include "mbedtls/sha256.h"
30
31 #include <string.h>
32 #endif
33
34 /*
35 * Uncomment to show key and signature details
36 */
37 #define VERBOSE
38
39 /*
40 * Uncomment to force use of a specific curve
41 */
42 #define ECPARAMS MBEDTLS_ECP_DP_SECP192R1
43
44 #if !defined(ECPARAMS)
45 #define ECPARAMS mbedtls_ecp_curve_list()->grp_id
46 #endif
47
48 #if !defined(MBEDTLS_ECDSA_C) || !defined(MBEDTLS_SHA256_C) || \
49 !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_CTR_DRBG_C)
main(void)50 int main( void )
51 {
52 mbedtls_printf("MBEDTLS_ECDSA_C and/or MBEDTLS_SHA256_C and/or "
53 "MBEDTLS_ENTROPY_C and/or MBEDTLS_CTR_DRBG_C not defined\n");
54 mbedtls_exit( 0 );
55 }
56 #else
57 #if defined(VERBOSE)
dump_buf(const char * title,unsigned char * buf,size_t len)58 static void dump_buf( const char *title, unsigned char *buf, size_t len )
59 {
60 size_t i;
61
62 mbedtls_printf( "%s", title );
63 for( i = 0; i < len; i++ )
64 mbedtls_printf("%c%c", "0123456789ABCDEF" [buf[i] / 16],
65 "0123456789ABCDEF" [buf[i] % 16] );
66 mbedtls_printf( "\n" );
67 }
68
dump_pubkey(const char * title,mbedtls_ecdsa_context * key)69 static void dump_pubkey( const char *title, mbedtls_ecdsa_context *key )
70 {
71 unsigned char buf[300];
72 size_t len;
73
74 if( mbedtls_ecp_point_write_binary( &key->MBEDTLS_PRIVATE(grp), &key->MBEDTLS_PRIVATE(Q),
75 MBEDTLS_ECP_PF_UNCOMPRESSED, &len, buf, sizeof buf ) != 0 )
76 {
77 mbedtls_printf("internal error\n");
78 return;
79 }
80
81 dump_buf( title, buf, len );
82 }
83 #else
84 #define dump_buf( a, b, c )
85 #define dump_pubkey( a, b )
86 #endif
87
88
main(int argc,char * argv[])89 int main( int argc, char *argv[] )
90 {
91 int ret = 1;
92 int exit_code = MBEDTLS_EXIT_FAILURE;
93 mbedtls_ecdsa_context ctx_sign, ctx_verify;
94 mbedtls_entropy_context entropy;
95 mbedtls_ctr_drbg_context ctr_drbg;
96 unsigned char message[100];
97 unsigned char hash[32];
98 unsigned char sig[MBEDTLS_ECDSA_MAX_LEN];
99 size_t sig_len;
100 const char *pers = "ecdsa";
101 ((void) argv);
102
103 mbedtls_ecdsa_init( &ctx_sign );
104 mbedtls_ecdsa_init( &ctx_verify );
105 mbedtls_ctr_drbg_init( &ctr_drbg );
106
107 memset( sig, 0, sizeof( sig ) );
108 memset( message, 0x25, sizeof( message ) );
109
110 if( argc != 1 )
111 {
112 mbedtls_printf( "usage: ecdsa\n" );
113
114 #if defined(_WIN32)
115 mbedtls_printf( "\n" );
116 #endif
117
118 goto exit;
119 }
120
121 /*
122 * Generate a key pair for signing
123 */
124 mbedtls_printf( "\n . Seeding the random number generator..." );
125 fflush( stdout );
126
127 mbedtls_entropy_init( &entropy );
128 if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
129 (const unsigned char *) pers,
130 strlen( pers ) ) ) != 0 )
131 {
132 mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
133 goto exit;
134 }
135
136 mbedtls_printf( " ok\n . Generating key pair..." );
137 fflush( stdout );
138
139 if( ( ret = mbedtls_ecdsa_genkey( &ctx_sign, ECPARAMS,
140 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
141 {
142 mbedtls_printf( " failed\n ! mbedtls_ecdsa_genkey returned %d\n", ret );
143 goto exit;
144 }
145
146 mbedtls_printf( " ok (key size: %d bits)\n", (int) ctx_sign.MBEDTLS_PRIVATE(grp).pbits );
147
148 dump_pubkey( " + Public key: ", &ctx_sign );
149
150 /*
151 * Compute message hash
152 */
153 mbedtls_printf( " . Computing message hash..." );
154 fflush( stdout );
155
156 if( ( ret = mbedtls_sha256( message, sizeof( message ), hash, 0 ) ) != 0 )
157 {
158 mbedtls_printf( " failed\n ! mbedtls_sha256 returned %d\n", ret );
159 goto exit;
160 }
161
162 mbedtls_printf( " ok\n" );
163
164 dump_buf( " + Hash: ", hash, sizeof( hash ) );
165
166 /*
167 * Sign message hash
168 */
169 mbedtls_printf( " . Signing message hash..." );
170 fflush( stdout );
171
172 if( ( ret = mbedtls_ecdsa_write_signature( &ctx_sign, MBEDTLS_MD_SHA256,
173 hash, sizeof( hash ),
174 sig, sizeof( sig ), &sig_len,
175 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
176 {
177 mbedtls_printf( " failed\n ! mbedtls_ecdsa_write_signature returned %d\n", ret );
178 goto exit;
179 }
180 mbedtls_printf( " ok (signature length = %u)\n", (unsigned int) sig_len );
181
182 dump_buf( " + Signature: ", sig, sig_len );
183
184 /*
185 * Transfer public information to verifying context
186 *
187 * We could use the same context for verification and signatures, but we
188 * chose to use a new one in order to make it clear that the verifying
189 * context only needs the public key (Q), and not the private key (d).
190 */
191 mbedtls_printf( " . Preparing verification context..." );
192 fflush( stdout );
193
194 if( ( ret = mbedtls_ecp_group_copy( &ctx_verify.MBEDTLS_PRIVATE(grp), &ctx_sign.MBEDTLS_PRIVATE(grp) ) ) != 0 )
195 {
196 mbedtls_printf( " failed\n ! mbedtls_ecp_group_copy returned %d\n", ret );
197 goto exit;
198 }
199
200 if( ( ret = mbedtls_ecp_copy( &ctx_verify.MBEDTLS_PRIVATE(Q), &ctx_sign.MBEDTLS_PRIVATE(Q) ) ) != 0 )
201 {
202 mbedtls_printf( " failed\n ! mbedtls_ecp_copy returned %d\n", ret );
203 goto exit;
204 }
205
206 /*
207 * Verify signature
208 */
209 mbedtls_printf( " ok\n . Verifying signature..." );
210 fflush( stdout );
211
212 if( ( ret = mbedtls_ecdsa_read_signature( &ctx_verify,
213 hash, sizeof( hash ),
214 sig, sig_len ) ) != 0 )
215 {
216 mbedtls_printf( " failed\n ! mbedtls_ecdsa_read_signature returned %d\n", ret );
217 goto exit;
218 }
219
220 mbedtls_printf( " ok\n" );
221
222 exit_code = MBEDTLS_EXIT_SUCCESS;
223
224 exit:
225
226 mbedtls_ecdsa_free( &ctx_verify );
227 mbedtls_ecdsa_free( &ctx_sign );
228 mbedtls_ctr_drbg_free( &ctr_drbg );
229 mbedtls_entropy_free( &entropy );
230
231 mbedtls_exit( exit_code );
232 }
233 #endif /* MBEDTLS_ECDSA_C && MBEDTLS_ENTROPY_C && MBEDTLS_CTR_DRBG_C &&
234 ECPARAMS */
235