X-Git-Url: https://git.distorted.org.uk/~mdw/sgt/putty/blobdiff_plain/3709bfe9981af43e3cd491c37d300b57e5b26d50..3980e64ffbb86a37d6810b004a04a21f338a408b:/sshdh.c diff --git a/sshdh.c b/sshdh.c index 35e66907..c733b61f 100644 --- a/sshdh.c +++ b/sshdh.c @@ -1,13 +1,13 @@ -#include "ssh.h" +/* + * Diffie-Hellman implementation for PuTTY. + */ -struct ssh_kex ssh_diffiehellman = { - "diffie-hellman-group1-sha1" -}; +#include "ssh.h" /* - * The prime p used in the key exchange. + * The primes used in the group1 and group14 key exchange. */ -static unsigned char P[] = { +static const unsigned char P1[] = { 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, @@ -20,81 +20,211 @@ static unsigned char P[] = { 0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE6, 0x53, 0x81, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }; +static const unsigned char P14[] = { + 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, 0xE4, 0x5B, 0x3D, + 0xC2, 0x00, 0x7C, 0xB8, 0xA1, 0x63, 0xBF, 0x05, 0x98, 0xDA, 0x48, 0x36, + 0x1C, 0x55, 0xD3, 0x9A, 0x69, 0x16, 0x3F, 0xA8, 0xFD, 0x24, 0xCF, 0x5F, + 0x83, 0x65, 0x5D, 0x23, 0xDC, 0xA3, 0xAD, 0x96, 0x1C, 0x62, 0xF3, 0x56, + 0x20, 0x85, 0x52, 0xBB, 0x9E, 0xD5, 0x29, 0x07, 0x70, 0x96, 0x96, 0x6D, + 0x67, 0x0C, 0x35, 0x4E, 0x4A, 0xBC, 0x98, 0x04, 0xF1, 0x74, 0x6C, 0x08, + 0xCA, 0x18, 0x21, 0x7C, 0x32, 0x90, 0x5E, 0x46, 0x2E, 0x36, 0xCE, 0x3B, + 0xE3, 0x9E, 0x77, 0x2C, 0x18, 0x0E, 0x86, 0x03, 0x9B, 0x27, 0x83, 0xA2, + 0xEC, 0x07, 0xA2, 0x8F, 0xB5, 0xC5, 0x5D, 0xF0, 0x6F, 0x4C, 0x52, 0xC9, + 0xDE, 0x2B, 0xCB, 0xF6, 0x95, 0x58, 0x17, 0x18, 0x39, 0x95, 0x49, 0x7C, + 0xEA, 0x95, 0x6A, 0xE5, 0x15, 0xD2, 0x26, 0x18, 0x98, 0xFA, 0x05, 0x10, + 0x15, 0x72, 0x8E, 0x5A, 0x8A, 0xAC, 0xAA, 0x68, 0xFF, 0xFF, 0xFF, 0xFF, + 0xFF, 0xFF, 0xFF, 0xFF +}; /* - * The generator g = 2. + * The generator g = 2 (used for both group1 and group14). */ -static unsigned char G[] = { 2 }; +static const unsigned char G[] = { 2 }; + +static const struct ssh_kex ssh_diffiehellman_group1_sha1 = { + "diffie-hellman-group1-sha1", "group1", + KEXTYPE_DH, P1, G, lenof(P1), lenof(G), &ssh_sha1 +}; + +static const struct ssh_kex *const group1_list[] = { + &ssh_diffiehellman_group1_sha1 +}; + +const struct ssh_kexes ssh_diffiehellman_group1 = { + sizeof(group1_list) / sizeof(*group1_list), + group1_list +}; + +static const struct ssh_kex ssh_diffiehellman_group14_sha1 = { + "diffie-hellman-group14-sha1", "group14", + KEXTYPE_DH, P14, G, lenof(P14), lenof(G), &ssh_sha1 +}; + +static const struct ssh_kex *const group14_list[] = { + &ssh_diffiehellman_group14_sha1 +}; + +const struct ssh_kexes ssh_diffiehellman_group14 = { + sizeof(group14_list) / sizeof(*group14_list), + group14_list +}; + +static const struct ssh_kex ssh_diffiehellman_gex_sha256 = { + "diffie-hellman-group-exchange-sha256", NULL, + KEXTYPE_DH, NULL, NULL, 0, 0, &ssh_sha256 +}; + +static const struct ssh_kex ssh_diffiehellman_gex_sha1 = { + "diffie-hellman-group-exchange-sha1", NULL, + KEXTYPE_DH, NULL, NULL, 0, 0, &ssh_sha1 +}; + +static const struct ssh_kex *const gex_list[] = { + &ssh_diffiehellman_gex_sha256, + &ssh_diffiehellman_gex_sha1 +}; + +const struct ssh_kexes ssh_diffiehellman_gex = { + sizeof(gex_list) / sizeof(*gex_list), + gex_list +}; /* * Variables. */ -static Bignum x, e, p, q, qmask, g; -static int need_to_free_pg; +struct dh_ctx { + Bignum x, e, p, q, qmask, g; +}; /* * Common DH initialisation. */ -static void dh_init(void) { - q = bignum_rshift(p, 1); - qmask = bignum_bitmask(q); +static void dh_init(struct dh_ctx *ctx) +{ + ctx->q = bignum_rshift(ctx->p, 1); + ctx->qmask = bignum_bitmask(ctx->q); + ctx->x = ctx->e = NULL; } /* - * Initialise DH for the standard group1. + * Initialise DH for a standard group. */ -void dh_setup_group1(void) { - p = bignum_from_bytes(P, sizeof(P)); - g = bignum_from_bytes(G, sizeof(G)); - dh_init(); +void *dh_setup_group(const struct ssh_kex *kex) +{ + struct dh_ctx *ctx = snew(struct dh_ctx); + ctx->p = bignum_from_bytes(kex->pdata, kex->plen); + ctx->g = bignum_from_bytes(kex->gdata, kex->glen); + dh_init(ctx); + return ctx; } /* - * Clean up. + * Initialise DH for a server-supplied group. */ -void dh_cleanup(void) { - freebn(p); - freebn(g); - freebn(q); - freebn(qmask); +void *dh_setup_gex(Bignum pval, Bignum gval) +{ + struct dh_ctx *ctx = snew(struct dh_ctx); + ctx->p = copybn(pval); + ctx->g = copybn(gval); + dh_init(ctx); + return ctx; +} + +/* + * Clean up and free a context. + */ +void dh_cleanup(void *handle) +{ + struct dh_ctx *ctx = (struct dh_ctx *)handle; + freebn(ctx->x); + freebn(ctx->e); + freebn(ctx->p); + freebn(ctx->g); + freebn(ctx->q); + freebn(ctx->qmask); + sfree(ctx); } /* * 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(void *handle, int nbits) +{ + struct dh_ctx *ctx = (struct dh_ctx *)handle; int i; int nbytes; unsigned char *buf; - nbytes = ssh1_bignum_length(qmask); - buf = smalloc(nbytes); + nbytes = ssh1_bignum_length(ctx->qmask); + buf = snewn(nbytes, unsigned char); do { /* * Create a potential x, by ANDing a string of random bytes * with qmask. */ - if (x) freebn(x); - ssh1_write_bignum(buf, qmask); - for (i = 2; i < nbytes; i++) - buf[i] &= random_byte(); - ssh1_read_bignum(buf, &x); - } while (bignum_cmp(x, One) <= 0 || bignum_cmp(x, q) >= 0); + if (ctx->x) + freebn(ctx->x); + if (nbits == 0 || nbits > bignum_bitcount(ctx->qmask)) { + ssh1_write_bignum(buf, ctx->qmask); + for (i = 2; i < nbytes; i++) + buf[i] &= random_byte(); + ssh1_read_bignum(buf, nbytes, &ctx->x); /* can't fail */ + } else { + int b, nb; + ctx->x = bn_power_2(nbits); + b = nb = 0; + for (i = 0; i < nbits; i++) { + if (nb == 0) { + nb = 8; + b = random_byte(); + } + bignum_set_bit(ctx->x, i, b & 1); + b >>= 1; + nb--; + } + } + } while (bignum_cmp(ctx->x, One) <= 0 || bignum_cmp(ctx->x, ctx->q) >= 0); + + sfree(buf); /* * Done. Now compute e = g^x mod p. */ - e = modpow(g, x, p); + ctx->e = modpow(ctx->g, ctx->x, ctx->p); - return e; + return ctx->e; } /* * 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(void *handle, Bignum f) +{ + struct dh_ctx *ctx = (struct dh_ctx *)handle; + Bignum ret; + ret = modpow(f, ctx->x, ctx->p); + return ret; }