зеркало из https://github.com/github/putty.git
142 строки
3.3 KiB
C
142 строки
3.3 KiB
C
#include "ssh.h"
|
|
|
|
const struct ssh_kex ssh_diffiehellman = {
|
|
"diffie-hellman-group1-sha1"
|
|
};
|
|
|
|
const struct ssh_kex ssh_diffiehellman_gex = {
|
|
"diffie-hellman-group-exchange-sha1"
|
|
};
|
|
|
|
/*
|
|
* The prime p used in the key exchange.
|
|
*/
|
|
static unsigned char P[] = {
|
|
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2,
|
|
0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1,
|
|
0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6,
|
|
0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD,
|
|
0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D,
|
|
0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45,
|
|
0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9,
|
|
0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED,
|
|
0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11,
|
|
0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE6, 0x53, 0x81,
|
|
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
|
|
};
|
|
|
|
/*
|
|
* The generator g = 2.
|
|
*/
|
|
static unsigned char G[] = { 2 };
|
|
|
|
/*
|
|
* Variables.
|
|
*/
|
|
static Bignum x, e, p, q, qmask, g;
|
|
static int need_to_free_pg;
|
|
|
|
/*
|
|
* Common DH initialisation.
|
|
*/
|
|
static void dh_init(void) {
|
|
q = bignum_rshift(p, 1);
|
|
qmask = bignum_bitmask(q);
|
|
}
|
|
|
|
/*
|
|
* Initialise DH for the standard group1.
|
|
*/
|
|
void dh_setup_group1(void) {
|
|
p = bignum_from_bytes(P, sizeof(P));
|
|
g = bignum_from_bytes(G, sizeof(G));
|
|
dh_init();
|
|
}
|
|
|
|
/*
|
|
* Initialise DH for an alternative group.
|
|
*/
|
|
void dh_setup_group(Bignum pval, Bignum gval) {
|
|
p = copybn(pval);
|
|
g = copybn(gval);
|
|
dh_init();
|
|
}
|
|
|
|
/*
|
|
* Clean up.
|
|
*/
|
|
void dh_cleanup(void) {
|
|
freebn(p);
|
|
freebn(g);
|
|
freebn(q);
|
|
freebn(qmask);
|
|
}
|
|
|
|
/*
|
|
* DH stage 1: invent a number x between 1 and q, and compute e =
|
|
* g^x mod p. Return e.
|
|
*
|
|
* If `nbits' is greater than zero, it is used as an upper limit
|
|
* for the number of bits in x. This is safe provided that (a) you
|
|
* use twice as many bits in x as the number of bits you expect to
|
|
* use in your session key, and (b) the DH group is a safe prime
|
|
* (which SSH demands that it must be).
|
|
*
|
|
* P. C. van Oorschot, M. J. Wiener
|
|
* "On Diffie-Hellman Key Agreement with Short Exponents".
|
|
* Advances in Cryptology: Proceedings of Eurocrypt '96
|
|
* Springer-Verlag, May 1996.
|
|
*/
|
|
Bignum dh_create_e(int nbits) {
|
|
int i;
|
|
|
|
int nbytes;
|
|
unsigned char *buf;
|
|
|
|
nbytes = ssh1_bignum_length(qmask);
|
|
buf = smalloc(nbytes);
|
|
|
|
do {
|
|
/*
|
|
* Create a potential x, by ANDing a string of random bytes
|
|
* with qmask.
|
|
*/
|
|
if (x) freebn(x);
|
|
if (nbits == 0 || nbits > ssh1_bignum_bitcount(qmask)) {
|
|
ssh1_write_bignum(buf, qmask);
|
|
for (i = 2; i < nbytes; i++)
|
|
buf[i] &= random_byte();
|
|
ssh1_read_bignum(buf, &x);
|
|
} else {
|
|
int b, nb;
|
|
x = bn_power_2(nbits);
|
|
nb = 0;
|
|
for (i = 0; i < nbits; i++) {
|
|
if (nb == 0) {
|
|
nb = 8;
|
|
b = random_byte();
|
|
}
|
|
bignum_set_bit(x, i, b & 1);
|
|
b >>= 1;
|
|
nb--;
|
|
}
|
|
}
|
|
} while (bignum_cmp(x, One) <= 0 || bignum_cmp(x, q) >= 0);
|
|
|
|
/*
|
|
* Done. Now compute e = g^x mod p.
|
|
*/
|
|
e = modpow(g, x, p);
|
|
|
|
return e;
|
|
}
|
|
|
|
/*
|
|
* DH stage 2: given a number f, compute K = f^x mod p.
|
|
*/
|
|
Bignum dh_find_K(Bignum f) {
|
|
Bignum ret;
|
|
ret = modpow(f, x, p);
|
|
return ret;
|
|
}
|