1/*
2 *  RSA simple decryption program
3 *
4 *  Copyright The Mbed TLS Contributors
5 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
6 */
7
8#include "mbedtls/build_info.h"
9
10#include "mbedtls/platform.h"
11
12#if defined(MBEDTLS_BIGNUM_C) && defined(MBEDTLS_RSA_C) && \
13    defined(MBEDTLS_FS_IO) && defined(MBEDTLS_ENTROPY_C) && \
14    defined(MBEDTLS_CTR_DRBG_C)
15#include "mbedtls/rsa.h"
16#include "mbedtls/entropy.h"
17#include "mbedtls/ctr_drbg.h"
18
19#include <string.h>
20
21#endif
22
23#if !defined(MBEDTLS_BIGNUM_C) || !defined(MBEDTLS_RSA_C) ||  \
24    !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_ENTROPY_C) || \
25    !defined(MBEDTLS_CTR_DRBG_C)
26int main(void)
27{
28    mbedtls_printf("MBEDTLS_BIGNUM_C and/or MBEDTLS_RSA_C and/or "
29                   "MBEDTLS_FS_IO and/or MBEDTLS_ENTROPY_C and/or "
30                   "MBEDTLS_CTR_DRBG_C not defined.\n");
31    mbedtls_exit(0);
32}
33#else
34
35
36int main(int argc, char *argv[])
37{
38    FILE *f;
39    int ret = 1;
40    int exit_code = MBEDTLS_EXIT_FAILURE;
41    unsigned c;
42    size_t i;
43    mbedtls_rsa_context rsa;
44    mbedtls_mpi N, P, Q, D, E, DP, DQ, QP;
45    mbedtls_entropy_context entropy;
46    mbedtls_ctr_drbg_context ctr_drbg;
47    unsigned char result[1024];
48    unsigned char buf[512];
49    const char *pers = "rsa_decrypt";
50    ((void) argv);
51
52    memset(result, 0, sizeof(result));
53
54    if (argc != 1) {
55        mbedtls_printf("usage: rsa_decrypt\n");
56
57#if defined(_WIN32)
58        mbedtls_printf("\n");
59#endif
60
61        mbedtls_exit(exit_code);
62    }
63
64    mbedtls_printf("\n  . Seeding the random number generator...");
65    fflush(stdout);
66
67    mbedtls_rsa_init(&rsa);
68    mbedtls_ctr_drbg_init(&ctr_drbg);
69    mbedtls_entropy_init(&entropy);
70    mbedtls_mpi_init(&N); mbedtls_mpi_init(&P); mbedtls_mpi_init(&Q);
71    mbedtls_mpi_init(&D); mbedtls_mpi_init(&E); mbedtls_mpi_init(&DP);
72    mbedtls_mpi_init(&DQ); mbedtls_mpi_init(&QP);
73
74    ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func,
75                                &entropy, (const unsigned char *) pers,
76                                strlen(pers));
77    if (ret != 0) {
78        mbedtls_printf(" failed\n  ! mbedtls_ctr_drbg_seed returned %d\n",
79                       ret);
80        goto exit;
81    }
82
83    mbedtls_printf("\n  . Reading private key from rsa_priv.txt");
84    fflush(stdout);
85
86    if ((f = fopen("rsa_priv.txt", "rb")) == NULL) {
87        mbedtls_printf(" failed\n  ! Could not open rsa_priv.txt\n" \
88                       "  ! Please run rsa_genkey first\n\n");
89        goto exit;
90    }
91
92    if ((ret = mbedtls_mpi_read_file(&N, 16, f))  != 0 ||
93        (ret = mbedtls_mpi_read_file(&E, 16, f))  != 0 ||
94        (ret = mbedtls_mpi_read_file(&D, 16, f))  != 0 ||
95        (ret = mbedtls_mpi_read_file(&P, 16, f))  != 0 ||
96        (ret = mbedtls_mpi_read_file(&Q, 16, f))  != 0 ||
97        (ret = mbedtls_mpi_read_file(&DP, 16, f)) != 0 ||
98        (ret = mbedtls_mpi_read_file(&DQ, 16, f)) != 0 ||
99        (ret = mbedtls_mpi_read_file(&QP, 16, f)) != 0) {
100        mbedtls_printf(" failed\n  ! mbedtls_mpi_read_file returned %d\n\n",
101                       ret);
102        fclose(f);
103        goto exit;
104    }
105    fclose(f);
106
107    if ((ret = mbedtls_rsa_import(&rsa, &N, &P, &Q, &D, &E)) != 0) {
108        mbedtls_printf(" failed\n  ! mbedtls_rsa_import returned %d\n\n",
109                       ret);
110        goto exit;
111    }
112
113    if ((ret = mbedtls_rsa_complete(&rsa)) != 0) {
114        mbedtls_printf(" failed\n  ! mbedtls_rsa_complete returned %d\n\n",
115                       ret);
116        goto exit;
117    }
118
119    /*
120     * Extract the RSA encrypted value from the text file
121     */
122    if ((f = fopen("result-enc.txt", "rb")) == NULL) {
123        mbedtls_printf("\n  ! Could not open %s\n\n", "result-enc.txt");
124        goto exit;
125    }
126
127    i = 0;
128
129    while (fscanf(f, "%02X", (unsigned int *) &c) > 0 &&
130           i < (int) sizeof(buf)) {
131        buf[i++] = (unsigned char) c;
132    }
133
134    fclose(f);
135
136    if (i != mbedtls_rsa_get_len(&rsa)) {
137        mbedtls_printf("\n  ! Invalid RSA signature format\n\n");
138        goto exit;
139    }
140
141    /*
142     * Decrypt the encrypted RSA data and print the result.
143     */
144    mbedtls_printf("\n  . Decrypting the encrypted data");
145    fflush(stdout);
146
147    ret = mbedtls_rsa_pkcs1_decrypt(&rsa, mbedtls_ctr_drbg_random,
148                                    &ctr_drbg, &i,
149                                    buf, result, 1024);
150    if (ret != 0) {
151        mbedtls_printf(" failed\n  ! mbedtls_rsa_pkcs1_decrypt returned %d\n\n",
152                       ret);
153        goto exit;
154    }
155
156    mbedtls_printf("\n  . OK\n\n");
157
158    mbedtls_printf("The decrypted result is: '%s'\n\n", result);
159
160    exit_code = MBEDTLS_EXIT_SUCCESS;
161
162exit:
163    mbedtls_ctr_drbg_free(&ctr_drbg);
164    mbedtls_entropy_free(&entropy);
165    mbedtls_rsa_free(&rsa);
166    mbedtls_mpi_free(&N); mbedtls_mpi_free(&P); mbedtls_mpi_free(&Q);
167    mbedtls_mpi_free(&D); mbedtls_mpi_free(&E); mbedtls_mpi_free(&DP);
168    mbedtls_mpi_free(&DQ); mbedtls_mpi_free(&QP);
169
170    mbedtls_exit(exit_code);
171}
172#endif /* MBEDTLS_BIGNUM_C && MBEDTLS_RSA_C && MBEDTLS_FS_IO */
173