1 /* 2 * Copyright 2012-2024 The OpenSSL Project Authors. All Rights Reserved. 3 * 4 * Licensed under the Apache License 2.0 (the "License"). You may not use 5 * this file except in compliance with the License. You can obtain a copy 6 * in the file LICENSE in the source distribution or at 7 * https://www.openssl.org/source/license.html 8 */ 9 10 /* 11 * Simple AES GCM authenticated encryption with additional data (AEAD) 12 * demonstration program. 13 */ 14 15 #include <stdio.h> 16 #include <openssl/err.h> 17 #include <openssl/bio.h> 18 #include <openssl/evp.h> 19 #include <openssl/core_names.h> 20 21 /* AES-GCM test data obtained from NIST public test vectors */ 22 23 /* AES key */ 24 static const unsigned char gcm_key[] = { 25 0xee, 0xbc, 0x1f, 0x57, 0x48, 0x7f, 0x51, 0x92, 0x1c, 0x04, 0x65, 0x66, 26 0x5f, 0x8a, 0xe6, 0xd1, 0x65, 0x8b, 0xb2, 0x6d, 0xe6, 0xf8, 0xa0, 0x69, 27 0xa3, 0x52, 0x02, 0x93, 0xa5, 0x72, 0x07, 0x8f 28 }; 29 30 /* Unique initialisation vector */ 31 static const unsigned char gcm_iv[] = { 32 0x99, 0xaa, 0x3e, 0x68, 0xed, 0x81, 0x73, 0xa0, 0xee, 0xd0, 0x66, 0x84 33 }; 34 35 /* Example plaintext to encrypt */ 36 static const unsigned char gcm_pt[] = { 37 0xf5, 0x6e, 0x87, 0x05, 0x5b, 0xc3, 0x2d, 0x0e, 0xeb, 0x31, 0xb2, 0xea, 38 0xcc, 0x2b, 0xf2, 0xa5 39 }; 40 41 /* 42 * Example of Additional Authenticated Data (AAD), i.e. unencrypted data 43 * which can be authenticated using the generated Tag value. 44 */ 45 static const unsigned char gcm_aad[] = { 46 0x4d, 0x23, 0xc3, 0xce, 0xc3, 0x34, 0xb4, 0x9b, 0xdb, 0x37, 0x0c, 0x43, 47 0x7f, 0xec, 0x78, 0xde 48 }; 49 50 /* Expected ciphertext value */ 51 static const unsigned char gcm_ct[] = { 52 0xf7, 0x26, 0x44, 0x13, 0xa8, 0x4c, 0x0e, 0x7c, 0xd5, 0x36, 0x86, 0x7e, 53 0xb9, 0xf2, 0x17, 0x36 54 }; 55 56 /* Expected AEAD Tag value */ 57 static const unsigned char gcm_tag[] = { 58 0x67, 0xba, 0x05, 0x10, 0x26, 0x2a, 0xe4, 0x87, 0xd7, 0x37, 0xee, 0x62, 59 0x98, 0xf7, 0x7e, 0x0c 60 }; 61 62 /* 63 * A library context and property query can be used to select & filter 64 * algorithm implementations. If they are NULL then the default library 65 * context and properties are used. 66 */ 67 static OSSL_LIB_CTX *libctx = NULL; 68 static const char *propq = NULL; 69 70 static int aes_gcm_encrypt(void) 71 { 72 int ret = 0; 73 EVP_CIPHER_CTX *ctx; 74 EVP_CIPHER *cipher = NULL; 75 int outlen, tmplen; 76 size_t gcm_ivlen = sizeof(gcm_iv); 77 unsigned char outbuf[1024]; 78 unsigned char outtag[16]; 79 OSSL_PARAM params[2] = { 80 OSSL_PARAM_END, OSSL_PARAM_END 81 }; 82 83 printf("AES GCM Encrypt:\n"); 84 printf("Plaintext:\n"); 85 BIO_dump_fp(stdout, gcm_pt, sizeof(gcm_pt)); 86 87 /* Create a context for the encrypt operation */ 88 if ((ctx = EVP_CIPHER_CTX_new()) == NULL) 89 goto err; 90 91 /* Fetch the cipher implementation */ 92 if ((cipher = EVP_CIPHER_fetch(libctx, "AES-256-GCM", propq)) == NULL) 93 goto err; 94 95 /* Set IV length if default 96 bits is not appropriate */ 96 params[0] = OSSL_PARAM_construct_size_t(OSSL_CIPHER_PARAM_AEAD_IVLEN, 97 &gcm_ivlen); 98 99 /* 100 * Initialise an encrypt operation with the cipher/mode, key, IV and 101 * IV length parameter. 102 * For demonstration purposes the IV is being set here. In a compliant 103 * application the IV would be generated internally so the iv passed in 104 * would be NULL. 105 */ 106 if (!EVP_EncryptInit_ex2(ctx, cipher, gcm_key, gcm_iv, params)) 107 goto err; 108 109 /* Zero or more calls to specify any AAD */ 110 if (!EVP_EncryptUpdate(ctx, NULL, &outlen, gcm_aad, sizeof(gcm_aad))) 111 goto err; 112 113 /* Encrypt plaintext */ 114 if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, gcm_pt, sizeof(gcm_pt))) 115 goto err; 116 117 /* Output encrypted block */ 118 printf("Ciphertext:\n"); 119 BIO_dump_fp(stdout, outbuf, outlen); 120 121 /* Finalise: note get no output for GCM */ 122 if (!EVP_EncryptFinal_ex(ctx, outbuf, &tmplen)) 123 goto err; 124 125 /* Get tag */ 126 params[0] = OSSL_PARAM_construct_octet_string(OSSL_CIPHER_PARAM_AEAD_TAG, 127 outtag, 16); 128 129 if (!EVP_CIPHER_CTX_get_params(ctx, params)) 130 goto err; 131 132 /* Output tag */ 133 printf("Tag:\n"); 134 BIO_dump_fp(stdout, outtag, 16); 135 136 ret = 1; 137 err: 138 if (!ret) 139 ERR_print_errors_fp(stderr); 140 141 EVP_CIPHER_free(cipher); 142 EVP_CIPHER_CTX_free(ctx); 143 144 return ret; 145 } 146 147 static int aes_gcm_decrypt(void) 148 { 149 int ret = 0; 150 EVP_CIPHER_CTX *ctx; 151 EVP_CIPHER *cipher = NULL; 152 int outlen, rv; 153 size_t gcm_ivlen = sizeof(gcm_iv); 154 unsigned char outbuf[1024]; 155 OSSL_PARAM params[2] = { 156 OSSL_PARAM_END, OSSL_PARAM_END 157 }; 158 159 printf("AES GCM Decrypt:\n"); 160 printf("Ciphertext:\n"); 161 BIO_dump_fp(stdout, gcm_ct, sizeof(gcm_ct)); 162 163 if ((ctx = EVP_CIPHER_CTX_new()) == NULL) 164 goto err; 165 166 /* Fetch the cipher implementation */ 167 if ((cipher = EVP_CIPHER_fetch(libctx, "AES-256-GCM", propq)) == NULL) 168 goto err; 169 170 /* Set IV length if default 96 bits is not appropriate */ 171 params[0] = OSSL_PARAM_construct_size_t(OSSL_CIPHER_PARAM_AEAD_IVLEN, 172 &gcm_ivlen); 173 174 /* 175 * Initialise an encrypt operation with the cipher/mode, key, IV and 176 * IV length parameter. 177 */ 178 if (!EVP_DecryptInit_ex2(ctx, cipher, gcm_key, gcm_iv, params)) 179 goto err; 180 181 /* Zero or more calls to specify any AAD */ 182 if (!EVP_DecryptUpdate(ctx, NULL, &outlen, gcm_aad, sizeof(gcm_aad))) 183 goto err; 184 185 /* Decrypt plaintext */ 186 if (!EVP_DecryptUpdate(ctx, outbuf, &outlen, gcm_ct, sizeof(gcm_ct))) 187 goto err; 188 189 /* Output decrypted block */ 190 printf("Plaintext:\n"); 191 BIO_dump_fp(stdout, outbuf, outlen); 192 193 /* Set expected tag value. */ 194 params[0] = OSSL_PARAM_construct_octet_string(OSSL_CIPHER_PARAM_AEAD_TAG, 195 (void *)gcm_tag, sizeof(gcm_tag)); 196 197 if (!EVP_CIPHER_CTX_set_params(ctx, params)) 198 goto err; 199 200 /* Finalise: note get no output for GCM */ 201 rv = EVP_DecryptFinal_ex(ctx, outbuf, &outlen); 202 /* 203 * Print out return value. If this is not successful authentication 204 * failed and plaintext is not trustworthy. 205 */ 206 printf("Tag Verify %s\n", rv > 0 ? "Successful!" : "Failed!"); 207 208 ret = 1; 209 err: 210 if (!ret) 211 ERR_print_errors_fp(stderr); 212 213 EVP_CIPHER_free(cipher); 214 EVP_CIPHER_CTX_free(ctx); 215 216 return ret; 217 } 218 219 int main(int argc, char **argv) 220 { 221 if (!aes_gcm_encrypt()) 222 return EXIT_FAILURE; 223 224 if (!aes_gcm_decrypt()) 225 return EXIT_FAILURE; 226 227 return EXIT_SUCCESS; 228 } 229
Indexes created Sun Mar 01 05:31:48 UTC 2026