/*
- * RSA implementation just sufficient for ssh client-side
- * initialisation step
- *
- * Rewritten for more speed by Joris van Rantwijk, Jun 1999.
+ * RSA implementation for PuTTY.
*/
#include <stdio.h>
#include "ssh.h"
#include "misc.h"
-#define GET_32BIT(cp) \
- (((unsigned long)(unsigned char)(cp)[0] << 24) | \
- ((unsigned long)(unsigned char)(cp)[1] << 16) | \
- ((unsigned long)(unsigned char)(cp)[2] << 8) | \
- ((unsigned long)(unsigned char)(cp)[3]))
-
-#define PUT_32BIT(cp, value) { \
- (cp)[0] = (unsigned char)((value) >> 24); \
- (cp)[1] = (unsigned char)((value) >> 16); \
- (cp)[2] = (unsigned char)((value) >> 8); \
- (cp)[3] = (unsigned char)(value); }
-
-int makekey(unsigned char *data, struct RSAKey *result,
+int makekey(unsigned char *data, int len, struct RSAKey *result,
unsigned char **keystr, int order)
{
unsigned char *p = data;
- int i;
+ int i, n;
+
+ if (len < 4)
+ return -1;
if (result) {
result->bits = 0;
} else
p += 4;
+ len -= 4;
+
/*
* order=0 means exponent then modulus (the keys sent by the
* server). order=1 means modulus then exponent (the keys
* stored in a keyfile).
*/
- if (order == 0)
- p += ssh1_read_bignum(p, result ? &result->exponent : NULL);
+ if (order == 0) {
+ n = ssh1_read_bignum(p, len, result ? &result->exponent : NULL);
+ if (n < 0) return -1;
+ p += n;
+ len -= n;
+ }
+
+ n = ssh1_read_bignum(p, len, result ? &result->modulus : NULL);
+ if (n < 0 || (result && bignum_bitcount(result->modulus) == 0)) return -1;
if (result)
- result->bytes = (((p[0] << 8) + p[1]) + 7) / 8;
+ result->bytes = n - 2;
if (keystr)
*keystr = p + 2;
- p += ssh1_read_bignum(p, result ? &result->modulus : NULL);
- if (order == 1)
- p += ssh1_read_bignum(p, result ? &result->exponent : NULL);
-
+ p += n;
+ len -= n;
+
+ if (order == 1) {
+ n = ssh1_read_bignum(p, len, result ? &result->exponent : NULL);
+ if (n < 0) return -1;
+ p += n;
+ len -= n;
+ }
return p - data;
}
-int makeprivate(unsigned char *data, struct RSAKey *result)
+int makeprivate(unsigned char *data, int len, struct RSAKey *result)
{
- return ssh1_read_bignum(data, &result->private_exponent);
+ return ssh1_read_bignum(data, len, &result->private_exponent);
}
-void rsaencrypt(unsigned char *data, int length, struct RSAKey *key)
+int rsaencrypt(unsigned char *data, int length, struct RSAKey *key)
{
Bignum b1, b2;
int i;
unsigned char *p;
+ if (key->bytes < length + 4)
+ return 0; /* RSA key too short! */
+
memmove(data + key->bytes - length, data, length);
data[0] = 0;
data[1] = 2;
freebn(b1);
freebn(b2);
+
+ return 1;
}
-Bignum rsadecrypt(Bignum input, struct RSAKey *key)
+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));
+}
+
+/*
+ * Compute (base ^ exp) % mod, provided mod == p * q, with p,q
+ * distinct primes, and iqmp is the multiplicative inverse of q mod p.
+ * Uses Chinese Remainder Theorem to speed computation up over the
+ * obvious implementation of a single big modpow.
+ */
+Bignum crt_modpow(Bignum base, Bignum exp, Bignum mod,
+ Bignum p, Bignum q, Bignum iqmp)
+{
+ Bignum pm1, qm1, pexp, qexp, presult, qresult, diff, multiplier, ret0, ret;
+
+ /*
+ * Reduce the exponent mod phi(p) and phi(q), to save time when
+ * exponentiating mod p and mod q respectively. Of course, since p
+ * and q are prime, phi(p) == p-1 and similarly for q.
+ */
+ pm1 = copybn(p);
+ decbn(pm1);
+ qm1 = copybn(q);
+ decbn(qm1);
+ pexp = bigmod(exp, pm1);
+ qexp = bigmod(exp, qm1);
+
+ /*
+ * Do the two modpows.
+ */
+ presult = modpow(base, pexp, p);
+ qresult = modpow(base, qexp, q);
+
+ /*
+ * Recombine the results. We want a value which is congruent to
+ * qresult mod q, and to presult mod p.
+ *
+ * We know that iqmp * q is congruent to 1 * mod p (by definition
+ * of iqmp) and to 0 mod q (obviously). So we start with qresult
+ * (which is congruent to qresult mod both primes), and add on
+ * (presult-qresult) * (iqmp * q) which adjusts it to be congruent
+ * to presult mod p without affecting its value mod q.
+ */
+ if (bignum_cmp(presult, qresult) < 0) {
+ /*
+ * Can't subtract presult from qresult without first adding on
+ * p.
+ */
+ Bignum tmp = presult;
+ presult = bigadd(presult, p);
+ freebn(tmp);
+ }
+ diff = bigsub(presult, qresult);
+ multiplier = bigmul(iqmp, q);
+ ret0 = bigmuladd(multiplier, diff, qresult);
+
+ /*
+ * Finally, reduce the result mod n.
+ */
+ ret = bigmod(ret0, mod);
+
+ /*
+ * Free all the intermediate results before returning.
+ */
+ freebn(pm1);
+ freebn(qm1);
+ freebn(pexp);
+ freebn(qexp);
+ freebn(presult);
+ freebn(qresult);
+ freebn(diff);
+ freebn(multiplier);
+ freebn(ret0);
+
+ return ret;
+}
+
+/*
+ * This function is a wrapper on modpow(). It has the same effect as
+ * modpow(), but employs RSA blinding to protect against timing
+ * attacks and also uses the Chinese Remainder Theorem (implemented
+ * above, in crt_modpow()) to speed up the main operation.
+ */
+static Bignum rsa_privkey_op(Bignum input, struct RSAKey *key)
{
+ Bignum random, random_encrypted, random_inverse;
+ Bignum input_blinded, ret_blinded;
Bignum ret;
- ret = modpow(input, key->private_exponent, key->modulus);
+
+ SHA512_State ss;
+ unsigned char digest512[64];
+ int digestused = lenof(digest512);
+ int hashseq = 0;
+
+ /*
+ * Start by inventing a random number chosen uniformly from the
+ * range 2..modulus-1. (We do this by preparing a random number
+ * of the right length and retrying if it's greater than the
+ * modulus, to prevent any potential Bleichenbacher-like
+ * attacks making use of the uneven distribution within the
+ * range that would arise from just reducing our number mod n.
+ * There are timing implications to the potential retries, of
+ * course, but all they tell you is the modulus, which you
+ * already knew.)
+ *
+ * To preserve determinism and avoid Pageant needing to share
+ * the random number pool, we actually generate this `random'
+ * number by hashing stuff with the private key.
+ */
+ while (1) {
+ int bits, byte, bitsleft, v;
+ random = copybn(key->modulus);
+ /*
+ * Find the topmost set bit. (This function will return its
+ * index plus one.) Then we'll set all bits from that one
+ * downwards randomly.
+ */
+ bits = bignum_bitcount(random);
+ byte = 0;
+ bitsleft = 0;
+ while (bits--) {
+ if (bitsleft <= 0) {
+ bitsleft = 8;
+ /*
+ * Conceptually the following few lines are equivalent to
+ * byte = random_byte();
+ */
+ if (digestused >= lenof(digest512)) {
+ unsigned char seqbuf[4];
+ PUT_32BIT(seqbuf, hashseq);
+ SHA512_Init(&ss);
+ SHA512_Bytes(&ss, "RSA deterministic blinding", 26);
+ SHA512_Bytes(&ss, seqbuf, sizeof(seqbuf));
+ sha512_mpint(&ss, key->private_exponent);
+ SHA512_Final(&ss, digest512);
+ hashseq++;
+
+ /*
+ * Now hash that digest plus the signature
+ * input.
+ */
+ SHA512_Init(&ss);
+ SHA512_Bytes(&ss, digest512, sizeof(digest512));
+ sha512_mpint(&ss, input);
+ SHA512_Final(&ss, digest512);
+
+ digestused = 0;
+ }
+ byte = digest512[digestused++];
+ }
+ v = byte & 1;
+ byte >>= 1;
+ bitsleft--;
+ bignum_set_bit(random, bits, v);
+ }
+
+ /*
+ * Now check that this number is strictly greater than
+ * zero, and strictly less than modulus.
+ */
+ if (bignum_cmp(random, Zero) <= 0 ||
+ bignum_cmp(random, key->modulus) >= 0) {
+ freebn(random);
+ continue;
+ } else {
+ break;
+ }
+ }
+
+ /*
+ * RSA blinding relies on the fact that (xy)^d mod n is equal
+ * to (x^d mod n) * (y^d mod n) mod n. We invent a random pair
+ * y and y^d; then we multiply x by y, raise to the power d mod
+ * n as usual, and divide by y^d to recover x^d. Thus an
+ * attacker can't correlate the timing of the modpow with the
+ * input, because they don't know anything about the number
+ * that was input to the actual modpow.
+ *
+ * The clever bit is that we don't have to do a huge modpow to
+ * get y and y^d; we will use the number we just invented as
+ * _y^d_, and use the _public_ exponent to compute (y^d)^e = y
+ * from it, which is much faster to do.
+ */
+ random_encrypted = crt_modpow(random, key->exponent,
+ key->modulus, key->p, key->q, key->iqmp);
+ random_inverse = modinv(random, key->modulus);
+ input_blinded = modmul(input, random_encrypted, key->modulus);
+ ret_blinded = crt_modpow(input_blinded, key->private_exponent,
+ key->modulus, key->p, key->q, key->iqmp);
+ ret = modmul(ret_blinded, random_inverse, key->modulus);
+
+ freebn(ret_blinded);
+ freebn(input_blinded);
+ freebn(random_inverse);
+ freebn(random_encrypted);
+ freebn(random);
+
return ret;
}
+Bignum rsadecrypt(Bignum input, struct RSAKey *key)
+{
+ return rsa_privkey_op(input, key);
+}
+
int rsastr_len(struct RSAKey *key)
{
Bignum md, ex;
/*
* Ensure p > q.
+ *
+ * I have seen key blobs in the wild which were generated with
+ * p < q, so instead of rejecting the key in this case we
+ * should instead flip them round into the canonical order of
+ * p > q. This also involves regenerating iqmp.
*/
- if (bignum_cmp(key->p, key->q) <= 0)
- return 0;
+ if (bignum_cmp(key->p, key->q) <= 0) {
+ Bignum tmp = key->p;
+ key->p = key->q;
+ key->q = tmp;
+
+ freebn(key->iqmp);
+ key->iqmp = modinv(key->q, key->p);
+ }
/*
* Ensure iqmp * q is congruent to 1, modulo p.
length = (ssh1_bignum_length(key->modulus) +
ssh1_bignum_length(key->exponent) + 4);
- ret = smalloc(length);
+ ret = snewn(length, unsigned char);
PUT_32BIT(ret, bignum_bitcount(key->modulus));
pos = 4;
}
/* Given a public blob, determine its length. */
-int rsa_public_blob_len(void *data)
+int rsa_public_blob_len(void *data, int maxlen)
{
unsigned char *p = (unsigned char *)data;
- int ret;
+ int n;
+ if (maxlen < 4)
+ return -1;
p += 4; /* length word */
- p += ssh1_read_bignum(p, NULL); /* exponent */
- p += ssh1_read_bignum(p, NULL); /* modulus */
+ maxlen -= 4;
+
+ n = ssh1_read_bignum(p, maxlen, NULL); /* exponent */
+ if (n < 0)
+ return -1;
+ p += n;
+
+ n = ssh1_read_bignum(p, maxlen, NULL); /* modulus */
+ if (n < 0)
+ return -1;
+ p += n;
return p - (unsigned char *)data;
}
freebn(key->exponent);
if (key->private_exponent)
freebn(key->private_exponent);
+ if (key->p)
+ freebn(key->p);
+ if (key->q)
+ freebn(key->q);
+ if (key->iqmp)
+ freebn(key->iqmp);
if (key->comment)
sfree(key->comment);
}
getstring(data, datalen, &p, &length);
if (!p)
return NULL;
- b = bignum_from_bytes(p, length);
+ b = bignum_from_bytes((unsigned char *)p, length);
return b;
}
int slen;
struct RSAKey *rsa;
- rsa = smalloc(sizeof(struct RSAKey));
+ rsa = snew(struct RSAKey);
if (!rsa)
return NULL;
getstring(&data, &len, &p, &slen);
rsa->exponent = getmp(&data, &len);
rsa->modulus = getmp(&data, &len);
rsa->private_exponent = NULL;
+ rsa->p = rsa->q = rsa->iqmp = NULL;
rsa->comment = NULL;
return rsa;
int len;
len = rsastr_len(rsa);
- p = smalloc(len);
+ p = snewn(len, char);
rsastr_fmt(p, rsa);
return p;
}
* (three length fields, 12+7=19).
*/
bloblen = 19 + elen + mlen;
- blob = smalloc(bloblen);
+ blob = snewn(bloblen, unsigned char);
p = blob;
PUT_32BIT(p, 7);
p += 4;
* sum of lengths.
*/
bloblen = 16 + dlen + plen + qlen + ulen;
- blob = smalloc(bloblen);
+ blob = snewn(bloblen, unsigned char);
p = blob;
PUT_32BIT(p, dlen);
p += 4;
char **b = (char **) blob;
struct RSAKey *rsa;
- rsa = smalloc(sizeof(struct RSAKey));
+ rsa = snew(struct RSAKey);
if (!rsa)
return NULL;
rsa->comment = NULL;
return bloblen;
}
+static int rsa2_pubkey_bits(void *blob, int len)
+{
+ struct RSAKey *rsa;
+ int ret;
+
+ rsa = rsa2_newkey((char *) blob, len);
+ ret = bignum_bitcount(rsa->modulus);
+ rsa2_freekey(rsa);
+
+ return ret;
+}
+
static char *rsa2_fingerprint(void *key)
{
struct RSAKey *rsa = (struct RSAKey *) key;
int numlen, i;
MD5Init(&md5c);
- MD5Update(&md5c, "\0\0\0\7ssh-rsa", 11);
+ MD5Update(&md5c, (unsigned char *)"\0\0\0\7ssh-rsa", 11);
#define ADD_BIGNUM(bignum) \
numlen = (bignum_bitcount(bignum)+8)/8; \
for (i = 0; i < 16; i++)
sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "",
digest[i]);
- ret = smalloc(strlen(buffer) + 1);
+ ret = snewn(strlen(buffer) + 1, char);
if (ret)
strcpy(ret, buffer);
return ret;
* iso(1) identified-organization(3) oiw(14) secsig(3)
* algorithms(2) 26 }
*/
-static unsigned char asn1_weird_stuff[] = {
+static const unsigned char asn1_weird_stuff[] = {
0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B,
0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14,
};
ret = 1;
- bytes = bignum_bitcount(rsa->modulus) / 8;
+ bytes = (bignum_bitcount(rsa->modulus)+7) / 8;
/* Top (partial) byte should be zero. */
if (bignum_byte(out, bytes - 1) != 0)
ret = 0;
if (bignum_byte(out, i) != hash[j])
ret = 0;
}
+ freebn(out);
return ret;
}
-unsigned char *rsa2_sign(void *key, char *data, int datalen, int *siglen)
+static unsigned char *rsa2_sign(void *key, char *data, int datalen,
+ int *siglen)
{
struct RSAKey *rsa = (struct RSAKey *) key;
unsigned char *bytes;
SHA_Simple(data, datalen, hash);
nbytes = (bignum_bitcount(rsa->modulus) - 1) / 8;
- bytes = smalloc(nbytes);
+ assert(1 <= nbytes - 20 - ASN1_LEN);
+ bytes = snewn(nbytes, unsigned char);
bytes[0] = 1;
for (i = 1; i < nbytes - 20 - ASN1_LEN; i++)
in = bignum_from_bytes(bytes, nbytes);
sfree(bytes);
- out = modpow(in, rsa->private_exponent, rsa->modulus);
+ out = rsa_privkey_op(in, rsa);
freebn(in);
nbytes = (bignum_bitcount(out) + 7) / 8;
- bytes = smalloc(4 + 7 + 4 + nbytes);
+ bytes = snewn(4 + 7 + 4 + nbytes, unsigned char);
PUT_32BIT(bytes, 7);
memcpy(bytes + 4, "ssh-rsa", 7);
PUT_32BIT(bytes + 4 + 7, nbytes);
rsa2_createkey,
rsa2_openssh_createkey,
rsa2_openssh_fmtkey,
+ rsa2_pubkey_bits,
rsa2_fingerprint,
rsa2_verifysig,
rsa2_sign,
"ssh-rsa",
"rsa2"
};
+
+void *ssh_rsakex_newkey(char *data, int len)
+{
+ return rsa2_newkey(data, len);
+}
+
+void ssh_rsakex_freekey(void *key)
+{
+ rsa2_freekey(key);
+}
+
+int ssh_rsakex_klen(void *key)
+{
+ struct RSAKey *rsa = (struct RSAKey *) key;
+
+ return bignum_bitcount(rsa->modulus);
+}
+
+static void oaep_mask(const struct ssh_hash *h, void *seed, int seedlen,
+ void *vdata, int datalen)
+{
+ unsigned char *data = (unsigned char *)vdata;
+ unsigned count = 0;
+
+ while (datalen > 0) {
+ int i, max = (datalen > h->hlen ? h->hlen : datalen);
+ void *s;
+ unsigned char counter[4], hash[SSH2_KEX_MAX_HASH_LEN];
+
+ assert(h->hlen <= SSH2_KEX_MAX_HASH_LEN);
+ PUT_32BIT(counter, count);
+ s = h->init();
+ h->bytes(s, seed, seedlen);
+ h->bytes(s, counter, 4);
+ h->final(s, hash);
+ count++;
+
+ for (i = 0; i < max; i++)
+ data[i] ^= hash[i];
+
+ data += max;
+ datalen -= max;
+ }
+}
+
+void ssh_rsakex_encrypt(const struct ssh_hash *h, unsigned char *in, int inlen,
+ unsigned char *out, int outlen,
+ void *key)
+{
+ Bignum b1, b2;
+ struct RSAKey *rsa = (struct RSAKey *) key;
+ int k, i;
+ char *p;
+ const int HLEN = h->hlen;
+
+ /*
+ * Here we encrypt using RSAES-OAEP. Essentially this means:
+ *
+ * - we have a SHA-based `mask generation function' which
+ * creates a pseudo-random stream of mask data
+ * deterministically from an input chunk of data.
+ *
+ * - we have a random chunk of data called a seed.
+ *
+ * - we use the seed to generate a mask which we XOR with our
+ * plaintext.
+ *
+ * - then we use _the masked plaintext_ to generate a mask
+ * which we XOR with the seed.
+ *
+ * - then we concatenate the masked seed and the masked
+ * plaintext, and RSA-encrypt that lot.
+ *
+ * The result is that the data input to the encryption function
+ * is random-looking and (hopefully) contains no exploitable
+ * structure such as PKCS1-v1_5 does.
+ *
+ * For a precise specification, see RFC 3447, section 7.1.1.
+ * Some of the variable names below are derived from that, so
+ * it'd probably help to read it anyway.
+ */
+
+ /* k denotes the length in octets of the RSA modulus. */
+ k = (7 + bignum_bitcount(rsa->modulus)) / 8;
+
+ /* The length of the input data must be at most k - 2hLen - 2. */
+ assert(inlen > 0 && inlen <= k - 2*HLEN - 2);
+
+ /* The length of the output data wants to be precisely k. */
+ assert(outlen == k);
+
+ /*
+ * Now perform EME-OAEP encoding. First set up all the unmasked
+ * output data.
+ */
+ /* Leading byte zero. */
+ out[0] = 0;
+ /* At position 1, the seed: HLEN bytes of random data. */
+ for (i = 0; i < HLEN; i++)
+ out[i + 1] = random_byte();
+ /* At position 1+HLEN, the data block DB, consisting of: */
+ /* The hash of the label (we only support an empty label here) */
+ h->final(h->init(), out + HLEN + 1);
+ /* A bunch of zero octets */
+ memset(out + 2*HLEN + 1, 0, outlen - (2*HLEN + 1));
+ /* A single 1 octet, followed by the input message data. */
+ out[outlen - inlen - 1] = 1;
+ memcpy(out + outlen - inlen, in, inlen);
+
+ /*
+ * Now use the seed data to mask the block DB.
+ */
+ oaep_mask(h, out+1, HLEN, out+HLEN+1, outlen-HLEN-1);
+
+ /*
+ * And now use the masked DB to mask the seed itself.
+ */
+ oaep_mask(h, out+HLEN+1, outlen-HLEN-1, out+1, HLEN);
+
+ /*
+ * Now `out' contains precisely the data we want to
+ * RSA-encrypt.
+ */
+ b1 = bignum_from_bytes(out, outlen);
+ b2 = modpow(b1, rsa->exponent, rsa->modulus);
+ p = (char *)out;
+ for (i = outlen; i--;) {
+ *p++ = bignum_byte(b2, i);
+ }
+ freebn(b1);
+ freebn(b2);
+
+ /*
+ * And we're done.
+ */
+}
+
+static const struct ssh_kex ssh_rsa_kex_sha1 = {
+ "rsa1024-sha1", NULL, KEXTYPE_RSA, NULL, NULL, 0, 0, &ssh_sha1
+};
+
+static const struct ssh_kex ssh_rsa_kex_sha256 = {
+ "rsa2048-sha256", NULL, KEXTYPE_RSA, NULL, NULL, 0, 0, &ssh_sha256
+};
+
+static const struct ssh_kex *const rsa_kex_list[] = {
+ &ssh_rsa_kex_sha256,
+ &ssh_rsa_kex_sha1
+};
+
+const struct ssh_kexes ssh_rsa_kex = {
+ sizeof(rsa_kex_list) / sizeof(*rsa_kex_list),
+ rsa_kex_list
+};