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#include "config.h"
#include "crypto/bn.h"
#include "tl-parser/portable_endian.h"
#include "tgl.h"
#include "tools.h"
#include "mtproto-utils.h"
static unsigned long long gcd (unsigned long long a, unsigned long long b) {
return b ? gcd (b, a % b) : a;
}
static int check_prime (struct tgl_state *TLS, TGLC_bn *p) {
int r = TGLC_bn_is_prime (p, /* "use default" */ 0, 0, TLS->TGLC_bn_ctx, 0);
ensure (r >= 0);
return r;
}
// Complete set of checks see at https://core.telegram.org/mtproto/security_guidelines
// Checks that (p,g) is acceptable pair for DH
int tglmp_check_DH_params (struct tgl_state *TLS, TGLC_bn *p, int g) {
if (g < 2 || g > 7) { return -1; }
if (TGLC_bn_num_bits (p) != 2048) { return -1; }
TGLC_bn *t = TGLC_bn_new ();
TGLC_bn *dh_g = TGLC_bn_new ();
ensure (TGLC_bn_set_word (dh_g, 4 * g));
ensure (TGLC_bn_mod (t, p, dh_g, TLS->TGLC_bn_ctx));
int x = TGLC_bn_get_word (t);
assert (x >= 0 && x < 4 * g);
TGLC_bn_free (dh_g);
int res = 0;
switch (g) {
case 2:
if (x != 7) { res = -1; }
break;
case 3:
if (x % 3 != 2) { res = -1; }
break;
case 4:
break;
case 5:
if (x % 5 != 1 && x % 5 != 4) { res = -1; }
break;
case 6:
if (x != 19 && x != 23) { res = -1; }
break;
case 7:
if (x % 7 != 3 && x % 7 != 5 && x % 7 != 6) { res = -1; }
break;
}
if (res < 0 || !check_prime (TLS, p)) {
TGLC_bn_free (t);
return -1;
}
TGLC_bn *b = TGLC_bn_new ();
ensure (TGLC_bn_set_word (b, 2));
ensure (TGLC_bn_div (t, 0, p, b, TLS->TGLC_bn_ctx));
if (!check_prime (TLS, t)) {
res = -1;
}
TGLC_bn_free (b);
TGLC_bn_free (t);
return res;
}
// checks that g_a is acceptable for DH
int tglmp_check_g_a (struct tgl_state *TLS, TGLC_bn *p, TGLC_bn *g_a) {
if (TGLC_bn_num_bytes (g_a) > 256) {
return -1;
}
if (TGLC_bn_num_bits (g_a) < 2048 - 64) {
return -1;
}
if (TGLC_bn_cmp (p, g_a) <= 0) {
return -1;
}
TGLC_bn *dif = TGLC_bn_new ();
TGLC_bn_sub (dif, p, g_a);
if (TGLC_bn_num_bits (dif) < 2048 - 64) {
TGLC_bn_free (dif);
return -1;
}
TGLC_bn_free (dif);
return 0;
}
static unsigned long long BN2ull (TGLC_bn *b) {
if (sizeof (unsigned long) == 8) {
return TGLC_bn_get_word (b);
} else if (sizeof (unsigned long long) == 8) {
assert (0); // As long as nobody ever uses this code, assume it is broken.
unsigned long long tmp;
/* Here be dragons, but it should be okay due to be64toh */
TGLC_bn_bn2bin (b, (unsigned char *) &tmp);
return be64toh (tmp);
} else {
assert (0);
}
}
static void ull2BN (TGLC_bn *b, unsigned long long val) {
if (sizeof (unsigned long) == 8 || val < (1ll << 32)) {
TGLC_bn_set_word (b, val);
} else if (sizeof (unsigned long long) == 8) {
assert (0); // As long as nobody ever uses this code, assume it is broken.
htobe64(val);
/* Here be dragons, but it should be okay due to htobe64 */
TGLC_bn_bin2bn ((unsigned char *) &val, 8, b);
} else {
assert (0);
}
}
int bn_factorize (TGLC_bn *pq, TGLC_bn *p, TGLC_bn *q) {
// Should work in any case
// Rewrite this code
unsigned long long what = BN2ull (pq);
int it = 0;
unsigned long long g = 0;
int i;
for (i = 0; i < 3 || it < 1000; i++) {
int q = ((rand() & 15) + 17) % what;
unsigned long long x = (long long)rand () % (what - 1) + 1, y = x;
int lim = 1 << (i + 18);
int j;
for (j = 1; j < lim; j++) {
++it;
unsigned long long a = x, b = x, c = q;
while (b) {
if (b & 1) {
c += a;
if (c >= what) {
c -= what;
}
}
a += a;
if (a >= what) {
a -= what;
}
b >>= 1;
}
x = c;
unsigned long long z = x < y ? what + x - y : x - y;
g = gcd (z, what);
if (g != 1) {
break;
}
if (!(j & (j - 1))) {
y = x;
}
}
if (g > 1 && g < what) break;
}
assert (g > 1 && g < what);
unsigned long long p1 = g;
unsigned long long p2 = what / g;
if (p1 > p2) {
unsigned long long t = p1; p1 = p2; p2 = t;
}
ull2BN (p, p1);
ull2BN (q, p2);
return 0;
}
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