利用openssl中AES加密文件

代码如下，编译采用：gcc -o encrypt_function encrypt_function.c -lcrypto -lm -g。运行的是：./encrypt_function filename. 这篇文章之后,我还会对其他openssl的加密AES API进行测试，希望给大家提供帮助.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <openssl/aes.h>
//判断文件大小
long filesize(FILE *stream)
{
long curpos, length;
curpos = ftell(stream);
fseek(stream, 0L, SEEK_END);
length = ftell(stream);
fseek(stream, curpos, SEEK_SET);
return length;
}

int decrypt_function(unsigned char *encrypt_string, unsigned char* decrypt_string,int len,char* key_string){
AES_KEY aes;
unsigned char iv[AES_BLOCK_SIZE];        // init vector
int i;

for (i=0; i<AES_BLOCK_SIZE; ++i) {
iv[i] = 0;
}
if (AES_set_decrypt_key(key_string, 128, &aes) < 0) {
fprintf(stderr, "Unable to set decryption key in AES\n");
exit(-1);
}

// decrypt
AES_cbc_encrypt(encrypt_string, decrypt_string, len, &aes, iv,
AES_DECRYPT);
}

void decrypt(char *fileIn, char *fileOut, unsigned char *key) {
int i,count = 0;
char * inBuffer=malloc(AES_BLOCK_SIZE);
char * outBuffer=malloc(AES_BLOCK_SIZE);
memset(inBuffer,0,16);
memset(outBuffer,0,16);
FILE *inFile = fopen(fileIn, "rb");
FILE *outFile = fopen(fileOut, "wb");

int buffer_size = 50000;
while(buffer_size%16)
buffer_size++;

char * data;
char * decrypted_data;

int Lengthoffile= filesize(inFile);
int newsize = Lengthoffile;
while(newsize%16)
newsize++;
int readins = ceil((double)Lengthoffile/buffer_size);
if(readins ==1){
data = (char *)malloc(sizeof(char)*newsize);
decrypted_data = (char *)malloc(sizeof(char)*newsize);
memset(data,0,newsize);
memset(decrypted_data,0,newsize);
}else{
data = (char *)malloc(sizeof(char)*buffer_size);
decrypted_data = (char *)malloc(sizeof(char)*buffer_size);
memset(data,0,buffer_size);
memset(decrypted_data,0,buffer_size);
}

int n = 0;
int total = 0,extra = 0,lea = 0,total_write = 0;
while(n < readins){
if(total < Lengthoffile && total + buffer_size < Lengthoffile){
count= fread(data, 1, buffer_size, inFile);
total += count;
}else if(total < Lengthoffile && total + buffer_size > Lengthoffile){
extra = fread(data, sizeof(char), buffer_size, inFile);
if(extra%AES_BLOCK_SIZE==0){
lea = extra;
}else{
lea=(extra/16 + 1)*16;
for(i = extra;i< lea;i++){
data[i] = '0';
}
}
count = lea;
total += lea;

}else if(total == Lengthoffile){
lea=(Lengthoffile/AES_BLOCK_SIZE + 1)*AES_BLOCK_SIZE;
for(i = Lengthoffile;i< lea;i++){
data[i] = '0';
}
count = lea;
total += lea;
}
decrypt_function(data, decrypted_data, count,key);
fwrite(decrypted_data, 1, count, outFile);
n++;
}

fclose(inFile);
fclose(outFile);
}

int encrypt_function(char * input, unsigned char* encrypt_string,int len,char *key_string) {
AES_KEY aes;
unsigned char iv[AES_BLOCK_SIZE];        // init vector
unsigned int i;

// Set encryption key
for (i=0; i<AES_BLOCK_SIZE; ++i) {
iv[i] = 0;
}
if (AES_set_encrypt_key(key_string, 128, &aes) < 0) {
fprintf(stderr, "Unable to set encryption key in AES\n");
exit(-1);
}
char * input_string = (char *)malloc(sizeof(char)*len);
memset(input_string,0,len);
strncpy(input_string,input,len);
if (encrypt_string == NULL||input_string==NULL) {
fprintf(stderr, "Unable to allocate memory for encrypt_string\n");
exit(-1);
}

if(len%AES_BLOCK_SIZE){
printf("len is error.\n");
exit(0);
}
// encrypt (iv will change)
AES_cbc_encrypt(input_string, encrypt_string, len, &aes, iv, AES_ENCRYPT);

return 0;
}

void encrypt(char *fileIn, char *fileOut, unsigned char *key) {
int i,count = 0;
char * inBuffer=malloc(AES_BLOCK_SIZE);
char * outBuffer=malloc(AES_BLOCK_SIZE);
memset(inBuffer,0,16);
memset(outBuffer,0,16);
FILE *inFile = fopen(fileIn, "rb");
FILE *outFile = fopen(fileOut, "wb");

int buffer_size = 50000;
while(buffer_size%16)
buffer_size++;

char * data;
char * encrypted_data;

int Lengthoffile= filesize(inFile);
int newsize = Lengthoffile;
while(newsize%16)
newsize++;
int readins = ceil((double)Lengthoffile/buffer_size);
if(readins ==1){
data = (char *)malloc(sizeof(char)*newsize);
encrypted_data = (char *)malloc(sizeof(char)*newsize);
memset(data,0,newsize);
memset(encrypted_data,0,newsize);
}else{
data = (char *)malloc(sizeof(char)*buffer_size);
encrypted_data = (char *)malloc(sizeof(char)*buffer_size);
memset(data,0,buffer_size);
memset(encrypted_data,0,buffer_size);
}

int n = 0;
int total = 0,extra = 0,lea = 0,total_write = 0;
while(n < readins){
if(total < Lengthoffile && total + buffer_size < Lengthoffile){
count= fread(data, 1, buffer_size, inFile);
total +=count;
}else if(total < Lengthoffile && total + buffer_size > Lengthoffile){
extra = fread(data, sizeof(char), buffer_size, inFile);
if(extra%AES_BLOCK_SIZE==0){
lea = extra;
}else{
lea=(extra/AES_BLOCK_SIZE + 1)*AES_BLOCK_SIZE;
for(i = extra;i< lea;i++){
data[i] = '0';
}
}
count = lea;
total +=lea;
}else if(total == Lengthoffile){
lea=(Lengthoffile/AES_BLOCK_SIZE + 1)*AES_BLOCK_SIZE;
for(i = Lengthoffile;i< lea;i++){
data[i] = '0';
}
count= lea;
total += lea;
}
encrypt_function(data, encrypted_data, count,key);
total_write+=fwrite(encrypted_data, 1, count, outFile);
n++;
}
printf("count = %d\n",total_write);
fclose(inFile);
fclose(outFile);
}

void main(int argc,char ** argv){

char output_1[50]={0};
char output_2[50]={0};
char * key = "123456";
sprintf(output_1,"%s.encrypt",argv[1]);
sprintf(output_2,"%s.temp",argv[1]);
encrypt(argv[1],output_1,key);
//decrypt(output_1,output_2,key);
}