Copied tools directory from trunk. Here the original versions will be checked in, so that we can update them and merge the changes back in.

1 files changed, 643 insertions, 0 deletions

diff --git a/tools/plink/sshdss.c b/tools/plink/sshdss.c
new file mode 100644
index 000000000..dba1db1b4
--- /dev/null
+++ b/tools/plink/sshdss.c
@@ -0,0 +1,643 @@
+/*

+ * Digital Signature Standard implementation for PuTTY.

+ */

+

+#include <stdio.h>

+#include <stdlib.h>

+#include <assert.h>

+

+#include "ssh.h"

+#include "misc.h"

+

+static void sha_mpint(SHA_State * s, Bignum b)

+{

+    unsigned char lenbuf[4];

+    int len;

+    len = (bignum_bitcount(b) + 8) / 8;

+    PUT_32BIT(lenbuf, len);

+    SHA_Bytes(s, lenbuf, 4);

+    while (len-- > 0) {

+	lenbuf[0] = bignum_byte(b, len);

+	SHA_Bytes(s, lenbuf, 1);

+    }

+    memset(lenbuf, 0, sizeof(lenbuf));

+}

+

+static void sha512_mpint(SHA512_State * s, Bignum b)

+{

+    unsigned char lenbuf[4];

+    int len;

+    len = (bignum_bitcount(b) + 8) / 8;

+    PUT_32BIT(lenbuf, len);

+    SHA512_Bytes(s, lenbuf, 4);

+    while (len-- > 0) {

+	lenbuf[0] = bignum_byte(b, len);

+	SHA512_Bytes(s, lenbuf, 1);

+    }

+    memset(lenbuf, 0, sizeof(lenbuf));

+}

+

+static void getstring(char **data, int *datalen, char **p, int *length)

+{

+    *p = NULL;

+    if (*datalen < 4)

+	return;

+    *length = GET_32BIT(*data);

+    *datalen -= 4;

+    *data += 4;

+    if (*datalen < *length)

+	return;

+    *p = *data;

+    *data += *length;

+    *datalen -= *length;

+}

+static Bignum getmp(char **data, int *datalen)

+{

+    char *p;

+    int length;

+    Bignum b;

+

+    getstring(data, datalen, &p, &length);

+    if (!p)

+	return NULL;

+    if (p[0] & 0x80)

+	return NULL;		       /* negative mp */

+    b = bignum_from_bytes((unsigned char *)p, length);

+    return b;

+}

+

+static Bignum get160(char **data, int *datalen)

+{

+    Bignum b;

+

+    b = bignum_from_bytes((unsigned char *)*data, 20);

+    *data += 20;

+    *datalen -= 20;

+

+    return b;

+}

+

+static void *dss_newkey(char *data, int len)

+{

+    char *p;

+    int slen;

+    struct dss_key *dss;

+

+    dss = snew(struct dss_key);

+    if (!dss)

+	return NULL;

+    getstring(&data, &len, &p, &slen);

+

+#ifdef DEBUG_DSS

+    {

+	int i;

+	printf("key:");

+	for (i = 0; i < len; i++)

+	    printf("  %02x", (unsigned char) (data[i]));

+	printf("\n");

+    }

+#endif

+

+    if (!p || memcmp(p, "ssh-dss", 7)) {

+	sfree(dss);

+	return NULL;

+    }

+    dss->p = getmp(&data, &len);

+    dss->q = getmp(&data, &len);

+    dss->g = getmp(&data, &len);

+    dss->y = getmp(&data, &len);

+

+    return dss;

+}

+

+static void dss_freekey(void *key)

+{

+    struct dss_key *dss = (struct dss_key *) key;

+    freebn(dss->p);

+    freebn(dss->q);

+    freebn(dss->g);

+    freebn(dss->y);

+    sfree(dss);

+}

+

+static char *dss_fmtkey(void *key)

+{

+    struct dss_key *dss = (struct dss_key *) key;

+    char *p;

+    int len, i, pos, nibbles;

+    static const char hex[] = "0123456789abcdef";

+    if (!dss->p)

+	return NULL;

+    len = 8 + 4 + 1;		       /* 4 x "0x", punctuation, \0 */

+    len += 4 * (bignum_bitcount(dss->p) + 15) / 16;

+    len += 4 * (bignum_bitcount(dss->q) + 15) / 16;

+    len += 4 * (bignum_bitcount(dss->g) + 15) / 16;

+    len += 4 * (bignum_bitcount(dss->y) + 15) / 16;

+    p = snewn(len, char);

+    if (!p)

+	return NULL;

+

+    pos = 0;

+    pos += sprintf(p + pos, "0x");

+    nibbles = (3 + bignum_bitcount(dss->p)) / 4;

+    if (nibbles < 1)

+	nibbles = 1;

+    for (i = nibbles; i--;)

+	p[pos++] =

+	    hex[(bignum_byte(dss->p, i / 2) >> (4 * (i % 2))) & 0xF];

+    pos += sprintf(p + pos, ",0x");

+    nibbles = (3 + bignum_bitcount(dss->q)) / 4;

+    if (nibbles < 1)

+	nibbles = 1;

+    for (i = nibbles; i--;)

+	p[pos++] =

+	    hex[(bignum_byte(dss->q, i / 2) >> (4 * (i % 2))) & 0xF];

+    pos += sprintf(p + pos, ",0x");

+    nibbles = (3 + bignum_bitcount(dss->g)) / 4;

+    if (nibbles < 1)

+	nibbles = 1;

+    for (i = nibbles; i--;)

+	p[pos++] =

+	    hex[(bignum_byte(dss->g, i / 2) >> (4 * (i % 2))) & 0xF];

+    pos += sprintf(p + pos, ",0x");

+    nibbles = (3 + bignum_bitcount(dss->y)) / 4;

+    if (nibbles < 1)

+	nibbles = 1;

+    for (i = nibbles; i--;)

+	p[pos++] =

+	    hex[(bignum_byte(dss->y, i / 2) >> (4 * (i % 2))) & 0xF];

+    p[pos] = '\0';

+    return p;

+}

+

+static char *dss_fingerprint(void *key)

+{

+    struct dss_key *dss = (struct dss_key *) key;

+    struct MD5Context md5c;

+    unsigned char digest[16], lenbuf[4];

+    char buffer[16 * 3 + 40];

+    char *ret;

+    int numlen, i;

+

+    MD5Init(&md5c);

+    MD5Update(&md5c, (unsigned char *)"\0\0\0\7ssh-dss", 11);

+

+#define ADD_BIGNUM(bignum) \

+    numlen = (bignum_bitcount(bignum)+8)/8; \

+    PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \

+    for (i = numlen; i-- ;) { \

+        unsigned char c = bignum_byte(bignum, i); \

+        MD5Update(&md5c, &c, 1); \

+    }

+    ADD_BIGNUM(dss->p);

+    ADD_BIGNUM(dss->q);

+    ADD_BIGNUM(dss->g);

+    ADD_BIGNUM(dss->y);

+#undef ADD_BIGNUM

+

+    MD5Final(digest, &md5c);

+

+    sprintf(buffer, "ssh-dss %d ", bignum_bitcount(dss->p));

+    for (i = 0; i < 16; i++)

+	sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "",

+		digest[i]);

+    ret = snewn(strlen(buffer) + 1, char);

+    if (ret)

+	strcpy(ret, buffer);

+    return ret;

+}

+

+static int dss_verifysig(void *key, char *sig, int siglen,

+			 char *data, int datalen)

+{

+    struct dss_key *dss = (struct dss_key *) key;

+    char *p;

+    int slen;

+    char hash[20];

+    Bignum r, s, w, gu1p, yu2p, gu1yu2p, u1, u2, sha, v;

+    int ret;

+

+    if (!dss->p)

+	return 0;

+

+#ifdef DEBUG_DSS

+    {

+	int i;

+	printf("sig:");

+	for (i = 0; i < siglen; i++)

+	    printf("  %02x", (unsigned char) (sig[i]));

+	printf("\n");

+    }

+#endif

+    /*

+     * Commercial SSH (2.0.13) and OpenSSH disagree over the format

+     * of a DSA signature. OpenSSH is in line with RFC 4253:

+     * it uses a string "ssh-dss", followed by a 40-byte string

+     * containing two 160-bit integers end-to-end. Commercial SSH

+     * can't be bothered with the header bit, and considers a DSA

+     * signature blob to be _just_ the 40-byte string containing

+     * the two 160-bit integers. We tell them apart by measuring

+     * the length: length 40 means the commercial-SSH bug, anything

+     * else is assumed to be RFC-compliant.

+     */

+    if (siglen != 40) {		       /* bug not present; read admin fields */

+	getstring(&sig, &siglen, &p, &slen);

+	if (!p || slen != 7 || memcmp(p, "ssh-dss", 7)) {

+	    return 0;

+	}

+	sig += 4, siglen -= 4;	       /* skip yet another length field */

+    }

+    r = get160(&sig, &siglen);

+    s = get160(&sig, &siglen);

+    if (!r || !s)

+	return 0;

+

+    /*

+     * Step 1. w <- s^-1 mod q.

+     */

+    w = modinv(s, dss->q);

+

+    /*

+     * Step 2. u1 <- SHA(message) * w mod q.

+     */

+    SHA_Simple(data, datalen, (unsigned char *)hash);

+    p = hash;

+    slen = 20;

+    sha = get160(&p, &slen);

+    u1 = modmul(sha, w, dss->q);

+

+    /*

+     * Step 3. u2 <- r * w mod q.

+     */

+    u2 = modmul(r, w, dss->q);

+

+    /*

+     * Step 4. v <- (g^u1 * y^u2 mod p) mod q.

+     */

+    gu1p = modpow(dss->g, u1, dss->p);

+    yu2p = modpow(dss->y, u2, dss->p);

+    gu1yu2p = modmul(gu1p, yu2p, dss->p);

+    v = modmul(gu1yu2p, One, dss->q);

+

+    /*

+     * Step 5. v should now be equal to r.

+     */

+

+    ret = !bignum_cmp(v, r);

+

+    freebn(w);

+    freebn(sha);

+    freebn(gu1p);

+    freebn(yu2p);

+    freebn(gu1yu2p);

+    freebn(v);

+    freebn(r);

+    freebn(s);

+

+    return ret;

+}

+

+static unsigned char *dss_public_blob(void *key, int *len)

+{

+    struct dss_key *dss = (struct dss_key *) key;

+    int plen, qlen, glen, ylen, bloblen;

+    int i;

+    unsigned char *blob, *p;

+

+    plen = (bignum_bitcount(dss->p) + 8) / 8;

+    qlen = (bignum_bitcount(dss->q) + 8) / 8;

+    glen = (bignum_bitcount(dss->g) + 8) / 8;

+    ylen = (bignum_bitcount(dss->y) + 8) / 8;

+

+    /*

+     * string "ssh-dss", mpint p, mpint q, mpint g, mpint y. Total

+     * 27 + sum of lengths. (five length fields, 20+7=27).

+     */

+    bloblen = 27 + plen + qlen + glen + ylen;

+    blob = snewn(bloblen, unsigned char);

+    p = blob;

+    PUT_32BIT(p, 7);

+    p += 4;

+    memcpy(p, "ssh-dss", 7);

+    p += 7;

+    PUT_32BIT(p, plen);

+    p += 4;

+    for (i = plen; i--;)

+	*p++ = bignum_byte(dss->p, i);

+    PUT_32BIT(p, qlen);

+    p += 4;

+    for (i = qlen; i--;)

+	*p++ = bignum_byte(dss->q, i);

+    PUT_32BIT(p, glen);

+    p += 4;

+    for (i = glen; i--;)

+	*p++ = bignum_byte(dss->g, i);

+    PUT_32BIT(p, ylen);

+    p += 4;

+    for (i = ylen; i--;)

+	*p++ = bignum_byte(dss->y, i);

+    assert(p == blob + bloblen);

+    *len = bloblen;

+    return blob;

+}

+

+static unsigned char *dss_private_blob(void *key, int *len)

+{

+    struct dss_key *dss = (struct dss_key *) key;

+    int xlen, bloblen;

+    int i;

+    unsigned char *blob, *p;

+

+    xlen = (bignum_bitcount(dss->x) + 8) / 8;

+

+    /*

+     * mpint x, string[20] the SHA of p||q||g. Total 4 + xlen.

+     */

+    bloblen = 4 + xlen;

+    blob = snewn(bloblen, unsigned char);

+    p = blob;

+    PUT_32BIT(p, xlen);

+    p += 4;

+    for (i = xlen; i--;)

+	*p++ = bignum_byte(dss->x, i);

+    assert(p == blob + bloblen);

+    *len = bloblen;

+    return blob;

+}

+

+static void *dss_createkey(unsigned char *pub_blob, int pub_len,

+			   unsigned char *priv_blob, int priv_len)

+{

+    struct dss_key *dss;

+    char *pb = (char *) priv_blob;

+    char *hash;

+    int hashlen;

+    SHA_State s;

+    unsigned char digest[20];

+    Bignum ytest;

+

+    dss = dss_newkey((char *) pub_blob, pub_len);

+    dss->x = getmp(&pb, &priv_len);

+

+    /*

+     * Check the obsolete hash in the old DSS key format.

+     */

+    hashlen = -1;

+    getstring(&pb, &priv_len, &hash, &hashlen);

+    if (hashlen == 20) {

+	SHA_Init(&s);

+	sha_mpint(&s, dss->p);

+	sha_mpint(&s, dss->q);

+	sha_mpint(&s, dss->g);

+	SHA_Final(&s, digest);

+	if (0 != memcmp(hash, digest, 20)) {

+	    dss_freekey(dss);

+	    return NULL;

+	}

+    }

+

+    /*

+     * Now ensure g^x mod p really is y.

+     */

+    ytest = modpow(dss->g, dss->x, dss->p);

+    if (0 != bignum_cmp(ytest, dss->y)) {

+	dss_freekey(dss);

+	return NULL;

+    }

+    freebn(ytest);

+

+    return dss;

+}

+

+static void *dss_openssh_createkey(unsigned char **blob, int *len)

+{

+    char **b = (char **) blob;

+    struct dss_key *dss;

+

+    dss = snew(struct dss_key);

+    if (!dss)

+	return NULL;

+

+    dss->p = getmp(b, len);

+    dss->q = getmp(b, len);

+    dss->g = getmp(b, len);

+    dss->y = getmp(b, len);

+    dss->x = getmp(b, len);

+

+    if (!dss->p || !dss->q || !dss->g || !dss->y || !dss->x) {

+	sfree(dss->p);

+	sfree(dss->q);

+	sfree(dss->g);

+	sfree(dss->y);

+	sfree(dss->x);

+	sfree(dss);

+	return NULL;

+    }

+

+    return dss;

+}

+

+static int dss_openssh_fmtkey(void *key, unsigned char *blob, int len)

+{

+    struct dss_key *dss = (struct dss_key *) key;

+    int bloblen, i;

+

+    bloblen =

+	ssh2_bignum_length(dss->p) +

+	ssh2_bignum_length(dss->q) +

+	ssh2_bignum_length(dss->g) +

+	ssh2_bignum_length(dss->y) +

+	ssh2_bignum_length(dss->x);

+

+    if (bloblen > len)

+	return bloblen;

+

+    bloblen = 0;

+#define ENC(x) \

+    PUT_32BIT(blob+bloblen, ssh2_bignum_length((x))-4); bloblen += 4; \

+    for (i = ssh2_bignum_length((x))-4; i-- ;) blob[bloblen++]=bignum_byte((x),i);

+    ENC(dss->p);

+    ENC(dss->q);

+    ENC(dss->g);

+    ENC(dss->y);

+    ENC(dss->x);

+

+    return bloblen;

+}

+

+static int dss_pubkey_bits(void *blob, int len)

+{

+    struct dss_key *dss;

+    int ret;

+

+    dss = dss_newkey((char *) blob, len);

+    ret = bignum_bitcount(dss->p);

+    dss_freekey(dss);

+

+    return ret;

+}

+

+static unsigned char *dss_sign(void *key, char *data, int datalen, int *siglen)

+{

+    /*

+     * The basic DSS signing algorithm is:

+     * 

+     *  - invent a random k between 1 and q-1 (exclusive).

+     *  - Compute r = (g^k mod p) mod q.

+     *  - Compute s = k^-1 * (hash + x*r) mod q.

+     * 

+     * This has the dangerous properties that:

+     * 

+     *  - if an attacker in possession of the public key _and_ the

+     *    signature (for example, the host you just authenticated

+     *    to) can guess your k, he can reverse the computation of s

+     *    and work out x = r^-1 * (s*k - hash) mod q. That is, he

+     *    can deduce the private half of your key, and masquerade

+     *    as you for as long as the key is still valid.

+     * 

+     *  - since r is a function purely of k and the public key, if

+     *    the attacker only has a _range of possibilities_ for k

+     *    it's easy for him to work through them all and check each

+     *    one against r; he'll never be unsure of whether he's got

+     *    the right one.

+     * 

+     *  - if you ever sign two different hashes with the same k, it

+     *    will be immediately obvious because the two signatures

+     *    will have the same r, and moreover an attacker in

+     *    possession of both signatures (and the public key of

+     *    course) can compute k = (hash1-hash2) * (s1-s2)^-1 mod q,

+     *    and from there deduce x as before.

+     * 

+     *  - the Bleichenbacher attack on DSA makes use of methods of

+     *    generating k which are significantly non-uniformly

+     *    distributed; in particular, generating a 160-bit random

+     *    number and reducing it mod q is right out.

+     * 

+     * For this reason we must be pretty careful about how we

+     * generate our k. Since this code runs on Windows, with no

+     * particularly good system entropy sources, we can't trust our

+     * RNG itself to produce properly unpredictable data. Hence, we

+     * use a totally different scheme instead.

+     * 

+     * What we do is to take a SHA-512 (_big_) hash of the private

+     * key x, and then feed this into another SHA-512 hash that

+     * also includes the message hash being signed. That is:

+     * 

+     *   proto_k = SHA512 ( SHA512(x) || SHA160(message) )

+     * 

+     * This number is 512 bits long, so reducing it mod q won't be

+     * noticeably non-uniform. So

+     * 

+     *   k = proto_k mod q

+     * 

+     * This has the interesting property that it's _deterministic_:

+     * signing the same hash twice with the same key yields the

+     * same signature.

+     * 

+     * Despite this determinism, it's still not predictable to an

+     * attacker, because in order to repeat the SHA-512

+     * construction that created it, the attacker would have to

+     * know the private key value x - and by assumption he doesn't,

+     * because if he knew that he wouldn't be attacking k!

+     *

+     * (This trick doesn't, _per se_, protect against reuse of k.

+     * Reuse of k is left to chance; all it does is prevent

+     * _excessively high_ chances of reuse of k due to entropy

+     * problems.)

+     * 

+     * Thanks to Colin Plumb for the general idea of using x to

+     * ensure k is hard to guess, and to the Cambridge University

+     * Computer Security Group for helping to argue out all the

+     * fine details.

+     */

+    struct dss_key *dss = (struct dss_key *) key;

+    SHA512_State ss;

+    unsigned char digest[20], digest512[64];

+    Bignum proto_k, k, gkp, hash, kinv, hxr, r, s;

+    unsigned char *bytes;

+    int nbytes, i;

+

+    SHA_Simple(data, datalen, digest);

+

+    /*

+     * Hash some identifying text plus x.

+     */

+    SHA512_Init(&ss);

+    SHA512_Bytes(&ss, "DSA deterministic k generator", 30);

+    sha512_mpint(&ss, dss->x);

+    SHA512_Final(&ss, digest512);

+

+    /*

+     * Now hash that digest plus the message hash.

+     */

+    SHA512_Init(&ss);

+    SHA512_Bytes(&ss, digest512, sizeof(digest512));

+    SHA512_Bytes(&ss, digest, sizeof(digest));

+    SHA512_Final(&ss, digest512);

+

+    memset(&ss, 0, sizeof(ss));

+

+    /*

+     * Now convert the result into a bignum, and reduce it mod q.

+     */

+    proto_k = bignum_from_bytes(digest512, 64);

+    k = bigmod(proto_k, dss->q);

+    freebn(proto_k);

+

+    memset(digest512, 0, sizeof(digest512));

+

+    /*

+     * Now we have k, so just go ahead and compute the signature.

+     */

+    gkp = modpow(dss->g, k, dss->p);   /* g^k mod p */

+    r = bigmod(gkp, dss->q);	       /* r = (g^k mod p) mod q */

+    freebn(gkp);

+

+    hash = bignum_from_bytes(digest, 20);

+    kinv = modinv(k, dss->q);	       /* k^-1 mod q */

+    hxr = bigmuladd(dss->x, r, hash);  /* hash + x*r */

+    s = modmul(kinv, hxr, dss->q);     /* s = k^-1 * (hash + x*r) mod q */

+    freebn(hxr);

+    freebn(kinv);

+    freebn(hash);

+

+    /*

+     * Signature blob is

+     * 

+     *   string  "ssh-dss"

+     *   string  two 20-byte numbers r and s, end to end

+     * 

+     * i.e. 4+7 + 4+40 bytes.

+     */

+    nbytes = 4 + 7 + 4 + 40;

+    bytes = snewn(nbytes, unsigned char);

+    PUT_32BIT(bytes, 7);

+    memcpy(bytes + 4, "ssh-dss", 7);

+    PUT_32BIT(bytes + 4 + 7, 40);

+    for (i = 0; i < 20; i++) {

+	bytes[4 + 7 + 4 + i] = bignum_byte(r, 19 - i);

+	bytes[4 + 7 + 4 + 20 + i] = bignum_byte(s, 19 - i);

+    }

+    freebn(r);

+    freebn(s);

+

+    *siglen = nbytes;

+    return bytes;

+}

+

+const struct ssh_signkey ssh_dss = {

+    dss_newkey,

+    dss_freekey,

+    dss_fmtkey,

+    dss_public_blob,

+    dss_private_blob,

+    dss_createkey,

+    dss_openssh_createkey,

+    dss_openssh_fmtkey,

+    dss_pubkey_bits,

+    dss_fingerprint,

+    dss_verifysig,

+    dss_sign,

+    "ssh-dss",

+    "dss"

+};