这是以下问题的后续问题:
OpenSSL EVP_DecryptFinal_ex returns "wrong final block length" error when decrypting a file
我正在尝试解密文件。起初我把它读作ASCII文件而不是二进制文件。有了这个修复(我希望)并将其作为二进制读取我总是得到一个"bad decrypt"
错误:
15208:error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt:crypto\evp\evp_enc.c:570:
以下是我如何加密和解密的示例:
加密:
Cipher cipher;
ifstream f("d:/test.YML");
ofstream out("d:/temp.YML");
byte key[KEY_SIZE] = {1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2};
byte iv[BLOCK_SIZE] = {1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6};
secure_string line;
secure_string temp;
while (getline(f, line)) {
cipher.Encrypt(key, iv, line, temp);
out << temp << endl;
}
解密:
Cipher cipher;
ifstream f("d:/temp.YML", ifstream::binary);
ofstream out("d:/tempDecrypt.YML");
byte key[KEY_SIZE] = {1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2};
byte iv[BLOCK_SIZE] = {1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6};
secure_string temp;
vector<char> buffer(1024, 0);
while (!f.eof()) {
f.read(buffer.data(), buffer.size());
streamsize dataSize = f.gcount();
secure_string chunk = { buffer.begin(), buffer.begin() + dataSize };
cipher.Decrypt(key, iv, chunk, temp);
}
现在我不确定这个调查从哪里开始:
EVP_DecryptFinal_ex
)如果有人有任何指示,请告诉我。我之前从未使用加密技术,所以有些事情很难理解。
PS:我没有包括Encrypt
和Decrypt
方法,它们与Openssl Wiki website相同,请告诉我是否应该。
您的代码中存在许多问题......仅举几例:
ofstream out("d:/temp.YML");
应该以二进制模式打开。out << temp << endl;
将通过不必要地添加换行符来破坏二进制(加密)数据。update
/ final
模式。您无法独立加密/解密块。看看以下示例应用程序,它的工作原理如下:
#include <cstdint>
#include <fstream>
#include <openssl/conf.h>
#include <openssl/evp.h>
#include <openssl/err.h>
#include <openssl/rand.h>
#include <string.h>
#include <stdio.h>
static const size_t KEY_SIZE = 256 / 8, BLOCK_SIZE = 128 / 8;
class AESBase {
protected:
const uint8_t *key, *iv;
EVP_CIPHER_CTX *ctx;
AESBase(const uint8_t *key, const uint8_t *iv) : key(key), iv(iv) {
if (!(ctx = EVP_CIPHER_CTX_new()))
handleErrors();
}
~AESBase() {
EVP_CIPHER_CTX_free(ctx);
}
static void handleErrors(void) {
ERR_print_errors_fp(stderr);
abort();
}
};
class Encrypt : AESBase {
public:
Encrypt(const uint8_t *key, const uint8_t *iv) : AESBase(key, iv) {
if (1 != EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv))
handleErrors();
}
int update(const char *plaintext, int plaintext_len, char *ciphertext) {
int len;
if (1 != EVP_EncryptUpdate(ctx, (uint8_t*)ciphertext, &len, (const uint8_t*)plaintext, plaintext_len))
handleErrors();
return len;
}
int final(char *ciphertext) {
int len;
if (1 != EVP_EncryptFinal_ex(ctx, (uint8_t*)ciphertext, &len))
handleErrors();
return len;
}
};
class Decrypt : AESBase {
public:
Decrypt(const uint8_t *key, const uint8_t *iv) : AESBase(key, iv) {
if (1 != EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv))
handleErrors();
}
int update(const char *ciphertext, int ciphertext_len, char *plaintext) {
int len;
if (1 != EVP_DecryptUpdate(ctx, (uint8_t*)plaintext, &len, (const uint8_t*)ciphertext, ciphertext_len))
handleErrors();
return len;
}
int final(char *plaintext) {
int len;
if (1 != EVP_DecryptFinal_ex(ctx, (uint8_t*)plaintext, &len))
handleErrors();
return len;
}
};
void test_encrypt(const uint8_t *key, const char* in, const char* out) {
std::ifstream fin(in, std::ios_base::binary);
std::ofstream fout(out, std::ios_base::binary);
uint8_t iv[BLOCK_SIZE];
RAND_bytes(iv, sizeof(iv));
char buf[1024], temp[sizeof(buf) + BLOCK_SIZE];
Encrypt aes(key, iv);
fout.write((char*)iv, sizeof(iv));
while (fin) {
fin.read(buf, sizeof(buf));
int len = (int)fin.gcount();
if (len <= 0)
break;
len = aes.update(buf, len, temp);
fout.write(temp, len);
}
int len = aes.final(temp);
fout.write(temp, len);
}
void test_decrypt(const uint8_t *key, const char* in, const char* out) {
std::ifstream fin(in, std::ios_base::binary);
std::ofstream fout(out, std::ios_base::binary);
uint8_t iv[BLOCK_SIZE];
fin.read((char*)iv, sizeof(iv));
char buf[1024], temp[sizeof(buf) + BLOCK_SIZE];
Decrypt aes(key, iv);
while (fin) {
fin.read(buf, sizeof(buf));
int len = (int)fin.gcount();
if (len <= 0)
break;
len = aes.update(buf, len, temp);
fout.write(temp, len);
}
int len = aes.final(temp);
fout.write(temp, len);
}
int main()
{
ERR_load_crypto_strings();
OpenSSL_add_all_algorithms();
OPENSSL_config(NULL);
uint8_t key[KEY_SIZE] = { 1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2 };
test_encrypt(key, "main.cpp", "main.cpp.enc");
test_decrypt(key, "main.cpp.enc", "main.cpp.txt");
}