我想做什么： 在C中编写一个程序，打开一个任意大小的文件并读取其内容。一旦读取内容，它将在AES 256 CBC中加密它们并将密文保存到一个名为密文的文件中。保存后，它将关闭这两个文件。然后将打开刚刚保存的文件中的密文并解密密文并将其保存到一个名为decrypted的文件中。
我的问题： 它似乎永远不会解密我的密文。我得到垃圾，我不知道我做错了什么。请帮忙。
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <openssl/evp.h>
#include <openssl/aes.h>
void encrypt(FILE *ifp, FILE *ofp)
{
//Get file size
fseek(ifp, 0L, SEEK_END);
int fsize = ftell(ifp);
//set back to normal
fseek(ifp, 0L, SEEK_SET);
int outLen1 = 0; int outLen2 = 0;
unsigned char *indata = malloc(fsize);
unsigned char *outdata = malloc(fsize*2);
unsigned char ckey[] = "thiskeyisverybad";
unsigned char ivec[] = "dontusethisinput";
//Read File
fread(indata,sizeof(char),fsize, ifp);//Read Entire File
//Set up encryption
EVP_CIPHER_CTX ctx;
EVP_EncryptInit(&ctx,EVP_aes_256_cbc(),ckey,ivec);
EVP_EncryptUpdate(&ctx,outdata,&outLen1,indata,fsize);
EVP_EncryptFinal(&ctx,outdata,&outLen2);
fwrite(outdata,sizeof(char),fsize,ofp);
}
void decrypt(FILE *ifp, FILE *ofp)
{
//Get file size
fseek(ifp, 0L, SEEK_END);
int fsize = ftell(ifp);
//set back to normal
fseek(ifp, 0L, SEEK_SET);
int outLen1 = 0; int outLen2 = 0;
unsigned char *indata = malloc(fsize);
unsigned char *outdata = malloc(fsize*2);
unsigned char ckey[] = "thiskeyisverybad";
unsigned char ivec[] = "dontusethisinput";
//Read File
fread(indata,sizeof(char),fsize, ifp);//Read Entire File
//setup decryption
EVP_CIPHER_CTX ctx;
EVP_DecryptInit(&ctx,EVP_aes_256_cbc(),ckey,ivec);
EVP_DecryptUpdate(&ctx,outdata,&outLen1,indata,fsize);
EVP_DecryptFinal(&ctx,outdata,&outLen2);
fwrite(outdata,sizeof(char),fsize,ofp);
}
int main(int argc, char *argv[])
{
FILE *fIN, *fOUT;
fIN = fopen("plain.txt", "rb");//File to be encrypted; plain text
fOUT = fopen("cyphertext.txt", "wb");//File to be written; cipher text
encrypt(fIN, fOUT);
fclose(fIN);
fclose(fOUT);
//Decrypt file now
fIN = fopen("cyphertext.txt", "rb");//File to be written; cipher text
fOUT = fopen("decrypted.txt", "wb");//File to be written; cipher text
decrypt(fIN,fOUT);
fclose(fIN);
fclose(fOUT);
return 0;
}
注意：可能会有一些拼写错误。 编辑：似乎我用键和IV弄错了，两者都是128位，我试图使用256位CBC。这是我的问题，一旦我将其改为
似乎工作EVP_aes_128_cbc()
答案 0 :(得分：11)
这是我的代码版本。当然我更喜欢它，但我提供它作为替代品。注意完全没有错误检查：真正的代码会有它。
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <openssl/evp.h>
#include <openssl/aes.h>
#ifndef TRUE
#define TRUE 1
#endif
#ifndef FALSE
#define FALSE 0
#endif
/**
* Encrypt or decrypt, depending on flag 'should_encrypt'
*/
void en_de_crypt(int should_encrypt, FILE *ifp, FILE *ofp, unsigned char *ckey, unsigned char *ivec) {
const unsigned BUFSIZE=4096;
unsigned char *read_buf = malloc(BUFSIZE);
unsigned char *cipher_buf;
unsigned blocksize;
int out_len;
EVP_CIPHER_CTX ctx;
EVP_CipherInit(&ctx, EVP_aes_256_cbc(), ckey, ivec, should_encrypt);
blocksize = EVP_CIPHER_CTX_block_size(&ctx);
cipher_buf = malloc(BUFSIZE + blocksize);
while (1) {
// Read in data in blocks until EOF. Update the ciphering with each read.
int numRead = fread(read_buf, sizeof(unsigned char), BUFSIZE, ifp);
EVP_CipherUpdate(&ctx, cipher_buf, &out_len, read_buf, numRead);
fwrite(cipher_buf, sizeof(unsigned char), out_len, ofp);
if (numRead < BUFSIZE) { // EOF
break;
}
}
// Now cipher the final block and write it out.
EVP_CipherFinal(&ctx, cipher_buf, &out_len);
fwrite(cipher_buf, sizeof(unsigned char), out_len, ofp);
// Free memory
free(cipher_buf);
free(read_buf);
}
int main(int argc, char *argv[]) {
unsigned char ckey[] = "thiskeyisverybad";
unsigned char ivec[] = "dontusethisinput";
FILE *fIN, *fOUT;
if (argc != 2) {
printf("Usage: <executable> /path/to/file/exe");
return -1;
}
// First encrypt the file
fIN = fopen("plain.txt", "rb"); //File to be encrypted; plain text
fOUT = fopen("cyphertext.txt", "wb"); //File to be written; cipher text
en_de_crypt(TRUE, fIN, fOUT, ckey, ivec);
fclose(fIN);
fclose(fOUT);
//Decrypt file now
fIN = fopen("cyphertext.txt", "rb"); //File to be read; cipher text
fOUT = fopen("decrypted.txt", "wb"); //File to be written; cipher text
en_de_crypt(FALSE, fIN, fOUT, ckey, ivec);
fclose(fIN);
fclose(fOUT);
return 0;
}
答案 1 :(得分：5)
此代码有效，如果有人对如何更清洁或更有效率提出一些建议，请发表评论。
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <openssl/evp.h>
#include <openssl/aes.h>
void encrypt(FILE *ifp, FILE *ofp)
{
//Get file size
fseek(ifp, 0L, SEEK_END);
int fsize = ftell(ifp);
//set back to normal
fseek(ifp, 0L, SEEK_SET);
int outLen1 = 0; int outLen2 = 0;
unsigned char *indata = malloc(fsize);
unsigned char *outdata = malloc(fsize*2);
unsigned char ckey[] = "thiskeyisverybad";
unsigned char ivec[] = "dontusethisinput";
//Read File
fread(indata,sizeof(char),fsize, ifp);//Read Entire File
//Set up encryption
EVP_CIPHER_CTX ctx;
EVP_EncryptInit(&ctx,EVP_aes_128_cbc(),ckey,ivec);
EVP_EncryptUpdate(&ctx,outdata,&outLen1,indata,fsize);
EVP_EncryptFinal(&ctx,outdata + outLen1,&outLen2);
fwrite(outdata,sizeof(char),outLen1 + outLen2,ofp);
}
void decrypt(FILE *ifp, FILE *ofp)
{
//Get file size
fseek(ifp, 0L, SEEK_END);
int fsize = ftell(ifp);
//set back to normal
fseek(ifp, 0L, SEEK_SET);
int outLen1 = 0; int outLen2 = 0;
unsigned char *indata = malloc(fsize);
unsigned char *outdata = malloc(fsize);
unsigned char ckey[] = "thiskeyisverybad";
unsigned char ivec[] = "dontusethisinput";
//Read File
fread(indata,sizeof(char),fsize, ifp);//Read Entire File
//setup decryption
EVP_CIPHER_CTX ctx;
EVP_DecryptInit(&ctx,EVP_aes_128_cbc(),ckey,ivec);
EVP_DecryptUpdate(&ctx,outdata,&outLen1,indata,fsize);
EVP_DecryptFinal(&ctx,outdata + outLen1,&outLen2);
fwrite(outdata,sizeof(char),outLen1 + outLen2,ofp);
}
int main(int argc, char *argv[])
{
if(argc != 2){
printf("Usage: <executable> /path/to/file/exe");
return -1;
}
FILE *fIN, *fOUT;
fIN = fopen("plain.txt", "rb");//File to be encrypted; plain text
fOUT = fopen("cyphertext.txt", "wb");//File to be written; cipher text
encrypt(fIN, fOUT);
fclose(fIN);
fclose(fOUT);
//Decrypt file now
fIN = fopen("cyphertext.txt", "rb");//File to be written; cipher text
fOUT = fopen("decrypted.txt", "wb");//File to be written; cipher text
decrypt(fIN,fOUT);
fclose(fIN);
fclose(fOUT);
return 0;
}
另外根据这篇文章，EVP api将处理任意大小的输入