rsa_decrypt.c (5066B)
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) 26 int 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 36 int 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; 161 162 exit: 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 */