#include "lib4.h"
#include "lib3.h"
#include "lib2.h"
#include "lib.h"
/**
  * encrypt always with the same key, same nonce?
  *
  **/
int aes_ctr_edit(char *ciphertext, int ciphertext_length, int offset, char *newtext)
{
	// do not allow greater ciphertexts
	if((strlen(newtext)+offset) > ciphertext_length)
		return 1;
		
	// insert newtext at offset and reencrpyt
	char *plaintext = malloc(ciphertext_length);
	aes_ctr(ciphertext, ciphertext_length, plaintext, key, nonce);
	memcpy(&plaintext[offset], newtext, strlen(newtext));

	aes_ctr(plaintext, ciphertext_length, ciphertext, key, nonce);
	return 0;
}


void sha1_hmac(unsigned int *mac, unsigned char *message, unsigned int msg_len,
		unsigned char *key, unsigned int key_len)
{
	char *res = malloc(msg_len + key_len);

	memcpy(res, key, key_len);
	memcpy(&res[key_len], message, msg_len);

	SHA1Context sh;

	SHA1Reset(&sh);

	SHA1Input(&sh, res, (msg_len + key_len));
	SHA1Result(&sh);

	memcpy(mac, &(sh.Message_Digest), 20);
}

int sha1_hmac_verify(unsigned int *mac, unsigned char *msg, unsigned int msg_len,
		unsigned char *key, unsigned int key_len)
{
	unsigned int com_mac[5];

	sha1_hmac(com_mac, msg, msg_len, key, key_len);

	return !memcmp(com_mac, mac, 20);

}

int sha1_padding(unsigned long msg_len, char **result)
{
	int i;
	unsigned int padding_len = 64 - (msg_len % 64);
	// enough sapce for the length of the message?
	padding_len = padding_len < 9 ? padding_len+64 : padding_len;

	(*result) = malloc(padding_len);

	memset((*result), 0x00, padding_len);
	// append 1
	memset(&(*result)[0], 0x80, 1);
	//(*result)[0] = 0x80;

	// write the 8 byte msg_len at the end bytewise
	for(i=0;i<8;i++) {
		(*result)[padding_len-i-1] = (msg_len*8 >> (i*8)) & 0xFF;
	}

	return padding_len;
}

void sha1_hmac_forge(unsigned int *mac, unsigned char *text, unsigned int text_len,
		unsigned int *sha1_registers)
{
	SHA1Context sh;
	SHA1Reset(&sh);

	sha1_set_magic_nr(&sh, sha1_registers);

	SHA1Input(&sh, text, text_len);
	SHA1Result(&sh);

	memcpy(mac, &(sh.Message_Digest), 20);
}