X-Git-Url: https://git.distorted.org.uk/~mdw/sgt/putty/blobdiff_plain/e557416818242c2e8b14ec03d321740fd83619e4..e99bb8bfc8d2c1a47b6ae90ef43683d191c30f66:/sshdh.c

diff --git a/sshdh.c b/sshdh.c
index d556a252..c733b61f 100644
--- a/sshdh.c
+++ b/sshdh.c
@@ -1,115 +1,230 @@
+/*
+ * Diffie-Hellman implementation for PuTTY.
+ */
+
 #include "ssh.h"
 
-struct ssh_kex ssh_diffiehellman = {
-    "diffie-hellman-group1-sha1"
+/*
+ * The primes used in the group1 and group14 key exchange.
+ */
+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,
+    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
+};
+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 prime p used in the key exchange. 
+ * The generator g = 2 (used for both group1 and group14).
  */
-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 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
 };
 
 /*
- * The order q of the group: (p-1)/2.
+ * Variables.
  */
-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,
+struct dh_ctx {
+    Bignum x, e, p, q, qmask, g;
 };
 
 /*
- * The bitmask covering q (for ease of generation of x).
+ * Common DH initialisation.
  */
-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 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;
+}
 
 /*
- * The generator g = 2.
+ * Initialise DH for a standard group.
  */
-static unsigned short G[] = { 1, 2 };
+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;
+}
 
 /*
- * Variables.
+ * Initialise DH for a server-supplied group.
  */
-static Bignum x, e;
+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;
 
-    x = newbn(Q[0]);
+    int nbytes;
+    unsigned char *buf;
 
-    tryagain:
-
-    /*
-     * Create a potential x, by ANDing a string of random bytes
-     * with Qmask.
-     */
-    for (i = 1; i <= x[0]; i++)
-        x[i] = ((random_byte() << 8) + random_byte()) & Qmask[i];
+    nbytes = ssh1_bignum_length(ctx->qmask);
+    buf = snewn(nbytes, unsigned char);
 
-    /*
-     * If x <= 1, go round again.
-     */
-    for (i = 2; i <= x[0]; i++)
-        if (x[i] != 0)
-            break;
-    if (i > x[0] && x[1] <= 1)
-        goto tryagain;
+    do {
+	/*
+	 * Create a potential x, by ANDing a string of random bytes
+	 * with qmask.
+	 */
+	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);
 
-    /*
-     * If x >= q, go round again.
-     */
-    for (i = x[0]; i > 0; i--) {
-        if (x[i] > Q[i])
-            goto tryagain;
-        if (x[i] < Q[i])
-            break;
-    }
+    sfree(buf);
 
     /*
      * Done. Now compute e = g^x mod p.
      */
-    e = newbn(P[0]);
-    modpow(G, x, P, e);
+    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) {
-    Bignum K = newbn(P[0]);
-    modpow(f, x, P, K);
-    return K;
+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;
 }