#include "lib3.h"
#include "lib2.h"
#include "lib.h"


#define NR_STIRNGS_CHALLENGE17 10

char *challenge17_encrypt(int *length)
{
	int i, t;
	char **string;
	char **decoded;
	string = malloc(sizeof(char *)*NR_STIRNGS_CHALLENGE17);
	decoded = malloc(sizeof(char *)*NR_STIRNGS_CHALLENGE17);
	char filename[] = "task17_0";	

	for(i=0;i<10;i++) {
		filename[strlen(filename)-1] = (char) (i+'0');
		t = read_base64_file(filename, &string[i]);
		decoded[i] = malloc(t);
		length[i] = decode_base64(string[i], decoded[i]);
		printf("read: %s\n", string[i]);
	}
	// choose one randomly
	int random = rand() % NR_STIRNGS_CHALLENGE17;
	int padding;
	printf("plaintext: %s\n", string[random]);
	*length = strlen(string[random]);
	char *padded_string = __pkcs7_padding(string[random], *length, 16, &padding);
	char *encrypted = malloc(strlen(padded_string));
	*length += padding;
	aes_cbc(padded_string, strlen(padded_string), encrypted, key, iv, 1);
	return encrypted;	
}

int cbc_padding_oracle(char *encrypted, int length)
{
	char *decrypted = malloc(length);
	char *unpadded= malloc(length);
	
	aes_cbc(encrypted, length, decrypted, key, iv, 0);

	int valid = valid_pkcs7_padding(decrypted, length, unpadded, 16);
	free(decrypted);
	free(unpadded);
	return valid;

}

/**
  * format is: 64 nonce concat with 64 bit counter
  * calle has to make sure that nonce is at least 8 bytes
  * its all little endian
  */
int aes_ctr(char *in, int length_in, char *out, char *string_key, char *nonce)
{
	long counter;
	unsigned char tmp[16];
	char keystream[16];
	long nr_blocks = length_in / BLOCKSIZE;
	int length_last_block = length_in % BLOCKSIZE;
	memcpy(tmp, nonce, 16);

	for(counter=0;counter<nr_blocks-1;counter++) {
		// right now it only works for 256 block :P 
		tmp[8] = counter % 256;
		// encrypt nonce and counter and produce keystream
		aes_ecb(tmp, 16, keystream, string_key, 16, 1);
		// xor against keystream to encrpy/decrypt
		xor_string(&in[counter*BLOCKSIZE], keystream, &out[counter*BLOCKSIZE], 16, 16); 
	}

	// do last block
	tmp[8] = counter % 256;
	aes_ecb(tmp, 16, keystream, string_key, 16, 1);
	xor_string(&in[counter*BLOCKSIZE], keystream, &out[counter*BLOCKSIZE],
			16, length_last_block);

}

void mt_19937_seed(unsigned int seed)
{
	int i;

	__global_mt_19937.index = MT_19937_N;
	__global_mt_19937.mt[0] = seed;
	memset(&__global_mt_19937.mt[1], 0, 623);
	for(i=1;i<=MT_19937_N;i++) {
		__global_mt_19937.mt[i] = (1812433253 * (__global_mt_19937.mt[i-1]
			^ (__global_mt_19937.mt[i-1] >> 30))) + i;
		// only the last 32 bit
		__global_mt_19937.mt[i] &= 0xFFFFFFFF;
	}
}

void mt_19937_generate()
{
	unsigned int i, x;

	for(i=0;i<=MT_19937_N;i++) {
		x = (((__global_mt_19937.mt[i] & MT_19937_UPPER_MASK) + 
			(__global_mt_19937.mt[(i+1) % 624] & MT_19937_LOWER_MASK)
		   	)& 0xFFFFFFFF);
		
		__global_mt_19937.mt[i] = __global_mt_19937.mt[(i+397) % MT_19937_N] ^ x >> 1;	

		if (x % 2)
			__global_mt_19937.mt[i] ^= 0x9908b0df;
	}
	__global_mt_19937.index = 0;
}


int mt_19937()
{
	unsigned int y = 0x0;

	if(__global_mt_19937.index >= MT_19937_N)
		mt_19937_generate();

	y = __global_mt_19937.mt[__global_mt_19937.index];

	y = y ^ (y >> 11);
	y = y ^ ((y << 7) & 0x9D2C5680);
	y = y ^ ((y << 15) & 0xEFC60000);
	y = y ^ (y >> 18);

	__global_mt_19937.index++;

	return (y & 0xFFFFFFFF);
}