X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/a71540b90834ae07f4d9fcc09a43c7a09279c66f..32874aeac8dacbca26663777b39a79efc5d8dc4b:/sshdh.c diff --git a/sshdh.c b/sshdh.c index dabed52a..edd05b68 100644 --- a/sshdh.c +++ b/sshdh.c @@ -1,86 +1,138 @@ #include "ssh.h" -struct ssh_kex ssh_diffiehellman = { +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 short P[] = { - 64, - 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0x5381, 0xECE6, 0x6651, 0x4928, - 0x1FE6, 0x7C4B, 0x2411, 0xAE9F, 0x9FA5, 0x5A89, 0x6BFB, 0xEE38, - 0xB7ED, 0xF406, 0x5CB6, 0x0BFF, 0xED6B, 0xA637, 0x42E9, 0xF44C, - 0x7EC6, 0x625E, 0xB576, 0xE485, 0xC245, 0x6D51, 0x356D, 0x4FE1, - 0x1437, 0xF25F, 0x0A6D, 0x302B, 0x431B, 0xCD3A, 0x19B3, 0xEF95, - 0x04DD, 0x8E34, 0x0879, 0x514A, 0x9B22, 0x3B13, 0xBEA6, 0x020B, - 0xCC74, 0x8A67, 0x4E08, 0x2902, 0x1CD1, 0x80DC, 0x628B, 0xC4C6, - 0xC234, 0x2168, 0xDAA2, 0xC90F, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, +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 order q of the group: (p-1)/2. + * The generator g = 2. */ -static unsigned short Q[] = { - 64, - 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0x29C0, 0xF673, 0x3328, 0x2494, - 0x8FF3, 0xBE25, 0x9208, 0xD74F, 0xCFD2, 0xAD44, 0x35FD, 0xF71C, - 0x5BF6, 0x7A03, 0xAE5B, 0x85FF, 0xF6B5, 0xD31B, 0x2174, 0x7A26, - 0x3F63, 0x312F, 0xDABB, 0xF242, 0xE122, 0xB6A8, 0x9AB6, 0xA7F0, - 0x8A1B, 0xF92F, 0x8536, 0x9815, 0x218D, 0xE69D, 0x8CD9, 0xF7CA, - 0x026E, 0xC71A, 0x043C, 0x28A5, 0xCD91, 0x1D89, 0xDF53, 0x0105, - 0xE63A, 0x4533, 0x2704, 0x9481, 0x0E68, 0xC06E, 0x3145, 0x6263, - 0x611A, 0x10B4, 0xED51, 0xE487, 0xFFFF, 0xFFFF, 0xFFFF, 0x7FFF, -}; +static unsigned char G[] = { 2 }; /* - * The bitmask covering q (for ease of generation of x). + * Variables. */ -static unsigned short Qmask[] = { - 64, - 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, - 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, - 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, - 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, - 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, - 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, - 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, - 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0x7FFF, -}; +static Bignum x, e, p, q, qmask, g; +static int need_to_free_pg; /* - * The generator g = 2. + * Common DH initialisation. */ -static unsigned short G[] = { 1, 2 }; +static void dh_init(void) +{ + q = bignum_rshift(p, 1); + qmask = bignum_bitmask(q); +} /* - * Variables. + * Initialise DH for the standard group1. */ -static Bignum x, e; +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(void) { +Bignum dh_create_e(int nbits) +{ int i; - x = newbn(Q[0]); + 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. + * with qmask. */ - for (i = 1; i <= x[0]; i++) - x[i] = ((random_byte() << 8) + random_byte()) & Qmask[i]; - } while (bignum_cmp(x, One) <= 0 || bignum_cmp(x, Q) >= 0); + if (x) + freebn(x); + if (nbits == 0 || nbits > 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); + e = modpow(g, x, p); return e; } @@ -88,6 +140,9 @@ Bignum dh_create_e(void) { /* * DH stage 2: given a number f, compute K = f^x mod p. */ -Bignum dh_find_K(Bignum f) { - return modpow(f, x, P); +Bignum dh_find_K(Bignum f) +{ + Bignum ret; + ret = modpow(f, x, p); + return ret; }