我编写了一个小型测试程序，它采用一串纯文本，使用 AES 对其进行加密，并将其编码为 base 64。这部分看起来不错，但是当我尝试解码和解密数据时，我得到了错误的信息。
我的代码如下。我对C很陌生，所以我认为我在某处错误地使用了指针或引用而犯了一个新手错误。我试图在EVP_DecryptFinal_ex函数中找出问题所在，但似乎找不到错误。笔记！请忽略 and 的使用iv，key这只是测试代码。
代码：
#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <openssl/evp.h>
#include <openssl/bio.h>
#include <openssl/pem.h>
// BASE 64 ENCODING
char* base64Encode(const unsigned char *message, const size_t length) {
BIO *bio;
BIO *b64;
FILE* stream;
int encodedSize = 4*ceil((double)length/3);
char *buffer = (char*)malloc(encodedSize+1);
stream = fmemopen(buffer, encodedSize+1, "w");
b64 = BIO_new(BIO_f_base64());
bio = BIO_new_fp(stream, BIO_NOCLOSE);
bio = BIO_push(b64, bio);
BIO_set_flags(bio, BIO_FLAGS_BASE64_NO_NL);
BIO_write(bio, message, length);
(void)BIO_flush(bio);
BIO_free_all(bio);
fclose(stream);
return buffer;
}
// BASE 64 DECODING
int calcDecodeLength(const char *b64input) {
int len = strlen(b64input);
int padding = 0;
// Check for trailing '=''s as padding
if (b64input[len-1] == '=' && b64input[len-2] == '=') {
padding = 2;
} else if (b64input[len-1] == '=') {
padding = 1;
}
return (int)len*0.75 - padding;
}
int base64Decode(const char *b64message, unsigned char **buffer) {
BIO *bio;
BIO *b64;
int decodeLen = calcDecodeLength(b64message);
*buffer = (unsigned char*)malloc(decodeLen+1);
FILE* stream = fmemopen((char*)b64message, strlen(b64message), "r");
b64 = BIO_new(BIO_f_base64());
bio = BIO_new_fp(stream, BIO_NOCLOSE);
bio = BIO_push(b64, bio);
BIO_set_flags(bio, BIO_FLAGS_BASE64_NO_NL);
size_t length = BIO_read(bio, *buffer, strlen(b64message));
(*buffer)[length] = '\0';
BIO_free_all(bio);
fclose(stream);
return decodeLen;
}
// AES ENCRYPTION
int encryptAes(const char *plainText, char *cipherText, const char *key) {
unsigned char iv[] = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f };
int plainTextLength = 0;
int cipherTextLength = 0;
int blockLength = 0;
static const int MAX_PADDING_LENGTH = 16;
EVP_CIPHER_CTX encryptCtx;
EVP_CIPHER_CTX_init(&encryptCtx);
plainTextLength = strlen(plainText);
cipherText = (unsigned char *) malloc(plainTextLength + MAX_PADDING_LENGTH);
// Initialise the encryption with AES256 (CBC mode) using the key and IV
EVP_EncryptInit_ex(&encryptCtx, EVP_aes_256_cbc(), NULL, key, iv);
// Encrypt the plainText into the cipherText, update cipherTextLength with the length of the generated cipherText
if (!EVP_EncryptUpdate(&encryptCtx, cipherText, &blockLength, (unsigned char *) plainText, plainTextLength) ) {
printf("Error in EVP_EncryptUpdate \n");
return 1;
}
cipherTextLength += blockLength;
// Encrypt the "final" data remaining in a partial block
if (!EVP_EncryptFinal_ex(&encryptCtx, cipherText + cipherTextLength, &blockLength)) {
printf("Error in EVP_EncryptFinal_ex \n");
return 1;
}
cipherTextLength += blockLength;
EVP_CIPHER_CTX_cleanup(&encryptCtx);
return cipherTextLength;
}
// AES DECRYPTION
int decryptAes(const char *cipherText, char *decipheredPlainText, int cipherTextLength, const char *key) {
unsigned char iv[] = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f };
int plainTextLength = 0;
int blockLength = 0;
decipheredPlainText = (unsigned char *) malloc(cipherTextLength + 1);
EVP_CIPHER_CTX decryptCtx;
EVP_CIPHER_CTX_init(&decryptCtx);
// Initialise the decryption with AES256 (CBC mode) using the key and IV
EVP_DecryptInit_ex(&decryptCtx, EVP_aes_256_cbc(), NULL, key, iv);
// Decrypt the cipherText into the plainText, update plainTextLength
if (!EVP_DecryptUpdate(&decryptCtx, decipheredPlainText, &blockLength, cipherText, cipherTextLength)) {
printf("Error in EVP_DecryptUpdate\n");
return 1;
}
plainTextLength += blockLength;
// Decrypt the "final" data remaining in a partial block
if (!EVP_DecryptFinal_ex(&decryptCtx, decipheredPlainText + plainTextLength, &blockLength)) {
printf("Error in EVP_DecryptFinal_ex\n");
return 1;
}
plainTextLength += blockLength;
EVP_CIPHER_CTX_cleanup(&decryptCtx);
return plainTextLength;
}
int main(int argc, char **argv) {
unsigned char key[] = { 0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c };
const char *plainText = "cipher cipher cipher cipher CIPHER TEXT! 187? 1$5 78@2 14 .TӒ��틪�ձ1z.$�?�U���<y";
printf("Original Plain Text\t[%s]\n", plainText);
//////////////
// ENCRYPTION
//////////////
// Encrypt the plain text using AES
unsigned char cipherText[180];
int cipherTextLength = encryptAes(plainText, cipherText, key);
printf("Cipher Length\t\t[%d]\n", cipherTextLength);
// Base64 encode the buffer
char* encodedCipherText = base64Encode(cipherText, cipherTextLength);
printf("Base64 is\t\t[%s]\n", encodedCipherText);
//////////////
// DECRYPTION
//////////////
// Decode the Base64 string
unsigned char* decodedCipherText;
int decodedCipherTextLength = base64Decode(encodedCipherText, &decodedCipherText);
printf("Decoded Cipher Length\t[%d]\n", decodedCipherTextLength);
// Decrypt the cipher text
unsigned char decryptedPlainText[180];
int decryptedPlainTextLength = decryptAes(decodedCipherText, decryptedPlainText, decodedCipherTextLength, key);
printf("Decrypted Plain Text\t[%s]\n", decryptedPlainText);
// Compare before and after
if (strcmp(plainText, (char *) decryptedPlainText) == 0) {
printf("Decrypted data matches input data.\n");
} else {
printf("Decrypted data does not match input data.\n");
}
return 0;
}
命令：
gcc AesTest2.c -lcrypto -std=c99 -lm
输出：
Original Plain Text [cipher cipher cipher cipher CIPHER TEXT! 187? 1$5 78@2 14 .TӒ��틪�ձ1z.$�?�U���<y]
Cipher Length [112]
Base64 is [AQAAAAAAAACIEYLbPgAAAOh04wX/fwAAdgAAAAAAAAAJAAAAAAAAAP504wX/fwAAAAAAAAAAAADgFILbPgAAABB14wX/fwAAlwWp2z4AAAAodeMF/38AAAAAAAABAAAA2LGg2z4AAABxB0AAAAAAAA==]
Decoded Cipher Length [112]
Error in EVP_DecryptFinal_ex
Decrypted Plain Text [�t��]
Decrypted data does not match input data.
经验丰富的 C 开发人员的任何帮助将不胜感激。非常感谢。