CppCMS/aes_encryptor.cpp

#include <assert.h>
#include <stdio.h>

#include <string>
#include <vector>
#include <algorithm>
#include "cppcms_error.h"
#include "aes_encryptor.h"

#include "base64.h"

using namespace std;

namespace cppcms {

namespace aes {

namespace {
class load {
	public:
	load() {
		gcry_check_version(NULL);
	}
};

} // anon namespace

cipher::cipher(string k) :
	encryptor(k)
{
	bool in=false,out=false;
	in=gcry_cipher_open(&hd_in,GCRY_CIPHER_AES,GCRY_CIPHER_MODE_CBC,0) == 0;
	out=gcry_cipher_open(&hd_out,GCRY_CIPHER_AES,GCRY_CIPHER_MODE_CBC,0) == 0;
	if(!in || !out){
		goto error_exit;
	}

	if( gcry_cipher_setkey(hd_in,&key.front(),16) != 0) {
		goto error_exit;
	}
	if( gcry_cipher_setkey(hd_out,&key.front(),16) != 0)
		goto error_exit;
	char iv[16];
	gcry_create_nonce(iv,sizeof(iv));
	gcry_cipher_setiv(hd_out,iv,sizeof(iv));
	return;
error_exit:
	if(in) gcry_cipher_close(hd_in);
	if(out) gcry_cipher_close(hd_out);
	throw cppcms_error("AES cipher initialization failed");
}

cipher::~cipher()
{
	gcry_cipher_close(hd_in);
	gcry_cipher_close(hd_out);
}

string cipher::encrypt(string const &plain,time_t timeout)
{
	size_t block_size=(plain.size() + 15) / 16 * 16;

	vector<unsigned char> data(sizeof(aes_hdr)+sizeof(info)+block_size,0);
	copy(plain.begin(),plain.end(),data.begin() + sizeof(aes_hdr)+sizeof(info));
	aes_hdr &aes_header=*(aes_hdr*)(&data.front());
	info &header=*(info *)(&data.front()+sizeof(aes_hdr));
	header.timeout=timeout;
	header.size=plain.size();
	memset(&aes_header,0,16);

	gcry_md_hash_buffer(GCRY_MD_MD5,&aes_header.md5,&header,block_size+sizeof(info));
	gcry_cipher_encrypt(hd_out,&data.front(),data.size(),NULL,0);

	return base64_enc(data);
}

bool cipher::decrypt(string const &cipher,string &plain,time_t *timeout)
{
	vector<unsigned char> data;
	base64_dec(cipher,data);
	size_t norm_size=b64url::decoded_size(cipher.size());
	if(norm_size<sizeof(info)+sizeof(aes_hdr) || norm_size % 16 !=0)
		return false;

	gcry_cipher_decrypt(hd_in,&data.front(),data.size(),NULL,0);
	gcry_cipher_reset(hd_in);
	vector<char> md5(16,0);
	gcry_md_hash_buffer(GCRY_MD_MD5,&md5.front(),&data.front()+sizeof(aes_hdr),data.size()-sizeof(aes_hdr));
	aes_hdr &aes_header = *(aes_hdr*)&data.front();
	if(!std::equal(md5.begin(),md5.end(),aes_header.md5)) {
		return false;
	}
	info &header=*(info *)(&data.front()+sizeof(aes_hdr));
	if(time(NULL)>header.timeout)
		return false;
	if(timeout) *timeout=header.timeout;

	vector<unsigned char>::iterator data_start=data.begin()+sizeof(aes_hdr)+sizeof(info),
			data_end=data_start+header.size;

	plain.assign(data_start,data_end);
	return true;
}


} // namespace aes

} // namespace cppcms