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     }
67     mbedtls_printf("\n");
68 }
69 
dump_pubkey(const char * title,mbedtls_ecdsa_context * key)70 static void dump_pubkey(const char *title, mbedtls_ecdsa_context *key)
71 {
72     unsigned char buf[300];
73     size_t len;
74 
75     if (mbedtls_ecp_point_write_binary(&key->MBEDTLS_PRIVATE(grp), &key->MBEDTLS_PRIVATE(Q),
76                                        MBEDTLS_ECP_PF_UNCOMPRESSED, &len, buf, sizeof(buf)) != 0) {
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         mbedtls_printf("usage: ecdsa\n");
112 
113 #if defined(_WIN32)
114         mbedtls_printf("\n");
115 #endif
116 
117         goto exit;
118     }
119 
120     /*
121      * Generate a key pair for signing
122      */
123     mbedtls_printf("\n  . Seeding the random number generator...");
124     fflush(stdout);
125 
126     mbedtls_entropy_init(&entropy);
127     if ((ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
128                                      (const unsigned char *) pers,
129                                      strlen(pers))) != 0) {
130         mbedtls_printf(" failed\n  ! mbedtls_ctr_drbg_seed returned %d\n", ret);
131         goto exit;
132     }
133 
134     mbedtls_printf(" ok\n  . Generating key pair...");
135     fflush(stdout);
136 
137     if ((ret = mbedtls_ecdsa_genkey(&ctx_sign, ECPARAMS,
138                                     mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
139         mbedtls_printf(" failed\n  ! mbedtls_ecdsa_genkey returned %d\n", ret);
140         goto exit;
141     }
142 
143     mbedtls_printf(" ok (key size: %d bits)\n", (int) ctx_sign.MBEDTLS_PRIVATE(grp).pbits);
144 
145     dump_pubkey("  + Public key: ", &ctx_sign);
146 
147     /*
148      * Compute message hash
149      */
150     mbedtls_printf("  . Computing message hash...");
151     fflush(stdout);
152 
153     if ((ret = mbedtls_sha256(message, sizeof(message), hash, 0)) != 0) {
154         mbedtls_printf(" failed\n  ! mbedtls_sha256 returned %d\n", ret);
155         goto exit;
156     }
157 
158     mbedtls_printf(" ok\n");
159 
160     dump_buf("  + Hash: ", hash, sizeof(hash));
161 
162     /*
163      * Sign message hash
164      */
165     mbedtls_printf("  . Signing message hash...");
166     fflush(stdout);
167 
168     if ((ret = mbedtls_ecdsa_write_signature(&ctx_sign, MBEDTLS_MD_SHA256,
169                                              hash, sizeof(hash),
170                                              sig, sizeof(sig), &sig_len,
171                                              mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
172         mbedtls_printf(" failed\n  ! mbedtls_ecdsa_write_signature returned %d\n", ret);
173         goto exit;
174     }
175     mbedtls_printf(" ok (signature length = %u)\n", (unsigned int) sig_len);
176 
177     dump_buf("  + Signature: ", sig, sig_len);
178 
179     /*
180      * Transfer public information to verifying context
181      *
182      * We could use the same context for verification and signatures, but we
183      * chose to use a new one in order to make it clear that the verifying
184      * context only needs the public key (Q), and not the private key (d).
185      */
186     mbedtls_printf("  . Preparing verification context...");
187     fflush(stdout);
188 
189     if ((ret =
190              mbedtls_ecp_group_copy(&ctx_verify.MBEDTLS_PRIVATE(grp),
191                                     &ctx_sign.MBEDTLS_PRIVATE(grp))) != 0) {
192         mbedtls_printf(" failed\n  ! mbedtls_ecp_group_copy returned %d\n", ret);
193         goto exit;
194     }
195 
196     if ((ret =
197              mbedtls_ecp_copy(&ctx_verify.MBEDTLS_PRIVATE(Q), &ctx_sign.MBEDTLS_PRIVATE(Q))) != 0) {
198         mbedtls_printf(" failed\n  ! mbedtls_ecp_copy returned %d\n", ret);
199         goto exit;
200     }
201 
202     /*
203      * Verify signature
204      */
205     mbedtls_printf(" ok\n  . Verifying signature...");
206     fflush(stdout);
207 
208     if ((ret = mbedtls_ecdsa_read_signature(&ctx_verify,
209                                             hash, sizeof(hash),
210                                             sig, sig_len)) != 0) {
211         mbedtls_printf(" failed\n  ! mbedtls_ecdsa_read_signature returned %d\n", ret);
212         goto exit;
213     }
214 
215     mbedtls_printf(" ok\n");
216 
217     exit_code = MBEDTLS_EXIT_SUCCESS;
218 
219 exit:
220 
221     mbedtls_ecdsa_free(&ctx_verify);
222     mbedtls_ecdsa_free(&ctx_sign);
223     mbedtls_ctr_drbg_free(&ctr_drbg);
224     mbedtls_entropy_free(&entropy);
225 
226     mbedtls_exit(exit_code);
227 }
228 #endif /* MBEDTLS_ECDSA_C && MBEDTLS_ENTROPY_C && MBEDTLS_CTR_DRBG_C &&
229           ECPARAMS */
230