openssl - OpenSSL EVP_CIPHER 免费/发布

Question

我找不到像EVP_CIPHER_freein那样的任何方法openssl/evp.h。我不需要释放 EVP_CIPHERs 吗？

Answer 1

不，你没有。init 函数EVP_CipherInit_ex实际上是在 EVP_CIPHER_CTX object 中初始化变量ectx，您将其作为第一个参数传递。完成后记得打电话EVP_CIPHER_CTX_cleanup(&ectx)。

Answer 2

您可以在此页面底部清楚地看到它

EVP_CIPHER *cipher = NULL;
/* some stuff */
EVP_CIPHER_free(cipher);

完整代码：

int encrypt(const unsigned char *key, const unsigned char *iv,
         const unsigned char *msg, size_t msg_len, unsigned char *out)
{
/*
 * This assumes that key size is 32 bytes and the iv is 16 bytes.
 * For ciphertext stealing mode the length of the ciphertext "out" will be
 * the same size as the plaintext size "msg_len".
 * The "msg_len" can be any size >= 16.
 */
 int ret = 0, encrypt = 1, outlen, len;
 EVP_CIPHER_CTX *ctx = NULL;
 EVP_CIPHER *cipher = NULL;
 OSSL_PARAM params[2];

 ctx = EVP_CIPHER_CTX_new();
 cipher = EVP_CIPHER_fetch(NULL, "AES-256-CBC-CTS", NULL);
 if (ctx == NULL || cipher == NULL)
     goto err;

 /*
  * The default is "CS1" so this is not really needed,
  * but would be needed to set either "CS2" or "CS3".
  */
 params[0] = OSSL_PARAM_construct_utf8_string(OSSL_CIPHER_PARAM_CTS_MODE,
                                              "CS1", 0);
 params[1] = OSSL_PARAM_construct_end();

 if (!EVP_CipherInit_ex2(ctx, cipher, key, iv, encrypt, params))
     goto err;

 /* NOTE: CTS mode does not support multiple calls to EVP_CipherUpdate() */
 if (!EVP_CipherUpdate(ctx, encrypted, &outlen, msg, msglen))
     goto err;
  if (!EVP_CipherFinal_ex(ctx, encrypted + outlen, &len))
     goto err;
 ret = 1;
 err:
 EVP_CIPHER_free(cipher);
 EVP_CIPHER_CTX_free(ctx);
 return ret;
 }