OpenSSL使用功能EVP_BytesToKey。您可以在找到呼叫apps/enc.c。enc如果未使用-md参数指定其他摘要,则该实用程序默认情况下会在密钥派生算法(KDF)中使用MD5摘要。现在默认情况下使用SHA-256。这是使用MD5的工作示例:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/evp.h>
int main(int argc, char *argv[])
{
const EVP_CIPHER *cipher;
const EVP_MD *dgst = NULL;
unsigned char key[EVP_MAX_KEY_LENGTH], iv[EVP_MAX_IV_LENGTH];
const char *password = "password";
const unsigned char *salt = NULL;
int i;
OpenSSL_add_all_algorithms();
cipher = EVP_get_cipherbyname("aes-256-cbc");
if(!cipher) { fprintf(stderr, "no such cipher\n"); return 1; }
dgst=EVP_get_digestbyname("md5");
if(!dgst) { fprintf(stderr, "no such digest\n"); return 1; }
if(!EVP_BytesToKey(cipher, dgst, salt,
(unsigned char *) password,
strlen(password), 1, key, iv))
{
fprintf(stderr, "EVP_BytesToKey Failed\n");
return 1;
}
printf("Key: "); for(i=0; i<cipher->key_len; ++i) { printf("%02x", key[i]); } printf("\n");
printf("IV: "); for(i=0; i<cipher->iv_len; ++i) { printf("%02x", iv[i]); } printf("\n");
return 0;
}
用法示例:
gcc b2k.c -o b2k -lcrypto -g
./b2k
Key: 5f4dcc3b5aa765d61d8327deb882cf992b95990a9151374abd8ff8c5a7a0fe08
IV: b7b4372cdfbcb3d16a2631b59b509e94
生成与此OpenSSL命令行相同的密钥:
openssl enc -aes-256-cbc -k password -nosalt -p < /dev/null
key=5F4DCC3B5AA765D61D8327DEB882CF992B95990A9151374ABD8FF8C5A7A0FE08
iv =B7B4372CDFBCB3D16A2631B59B509E94
OpenSSL 1.1.0c更改了某些内部组件中使用的摘要算法。以前使用MD5,并且1.1.0切换到SHA256。小心的变化不影响你在这两个EVP_BytesToKey和命令状openssl enc。