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#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);
}
int mt_19937_timestamp_orcale()
{
sleep(random_number_between(40,1000));
unsigned int seed = time(NULL);
printf("timestamp orcale seed: %u\n", seed);
mt_19937_seed(seed);
sleep(random_number_between(40,1000));
return mt_19937();
}
/***
* is there a more clever way to do this than brute force?
*
**/
void mt_19937_brute_force_timestamp()
{
unsigned int start = time(NULL);
int rnd = mt_19937_timestamp_orcale();
unsigned int stop = time(NULL);
unsigned int i;
// try every seed between start and stop
for(i=start;start<=stop;i++) {
mt_19937_seed(i);
if (rnd == mt_19937()) {
printf("found seed: %u\n", i);
break;
}
}
}
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