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-rw-r--r--tools/plink/sshrsa.c2191
1 files changed, 1105 insertions, 1086 deletions
diff --git a/tools/plink/sshrsa.c b/tools/plink/sshrsa.c
index ea6440bc5..25f9cf7e6 100644
--- a/tools/plink/sshrsa.c
+++ b/tools/plink/sshrsa.c
@@ -1,1086 +1,1105 @@
-/*
- * RSA implementation for PuTTY.
- */
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <assert.h>
-
-#include "ssh.h"
-#include "misc.h"
-
-int makekey(unsigned char *data, int len, struct RSAKey *result,
- unsigned char **keystr, int order)
-{
- unsigned char *p = data;
- int i, n;
-
- if (len < 4)
- return -1;
-
- if (result) {
- result->bits = 0;
- for (i = 0; i < 4; i++)
- result->bits = (result->bits << 8) + *p++;
- } 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) {
- 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 = n - 2;
- if (keystr)
- *keystr = p + 2;
- 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, int len, struct RSAKey *result)
-{
- return ssh1_read_bignum(data, len, &result->private_exponent);
-}
-
-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;
-
- for (i = 2; i < key->bytes - length - 1; i++) {
- do {
- data[i] = random_byte();
- } while (data[i] == 0);
- }
- data[key->bytes - length - 1] = 0;
-
- b1 = bignum_from_bytes(data, key->bytes);
-
- b2 = modpow(b1, key->exponent, key->modulus);
-
- p = data;
- for (i = key->bytes; i--;) {
- *p++ = bignum_byte(b2, i);
- }
-
- freebn(b1);
- freebn(b2);
-
- return 1;
-}
-
-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;
-
- 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;
- int mdlen, exlen;
-
- md = key->modulus;
- ex = key->exponent;
- mdlen = (bignum_bitcount(md) + 15) / 16;
- exlen = (bignum_bitcount(ex) + 15) / 16;
- return 4 * (mdlen + exlen) + 20;
-}
-
-void rsastr_fmt(char *str, struct RSAKey *key)
-{
- Bignum md, ex;
- int len = 0, i, nibbles;
- static const char hex[] = "0123456789abcdef";
-
- md = key->modulus;
- ex = key->exponent;
-
- len += sprintf(str + len, "0x");
-
- nibbles = (3 + bignum_bitcount(ex)) / 4;
- if (nibbles < 1)
- nibbles = 1;
- for (i = nibbles; i--;)
- str[len++] = hex[(bignum_byte(ex, i / 2) >> (4 * (i % 2))) & 0xF];
-
- len += sprintf(str + len, ",0x");
-
- nibbles = (3 + bignum_bitcount(md)) / 4;
- if (nibbles < 1)
- nibbles = 1;
- for (i = nibbles; i--;)
- str[len++] = hex[(bignum_byte(md, i / 2) >> (4 * (i % 2))) & 0xF];
-
- str[len] = '\0';
-}
-
-/*
- * Generate a fingerprint string for the key. Compatible with the
- * OpenSSH fingerprint code.
- */
-void rsa_fingerprint(char *str, int len, struct RSAKey *key)
-{
- struct MD5Context md5c;
- unsigned char digest[16];
- char buffer[16 * 3 + 40];
- int numlen, slen, i;
-
- MD5Init(&md5c);
- numlen = ssh1_bignum_length(key->modulus) - 2;
- for (i = numlen; i--;) {
- unsigned char c = bignum_byte(key->modulus, i);
- MD5Update(&md5c, &c, 1);
- }
- numlen = ssh1_bignum_length(key->exponent) - 2;
- for (i = numlen; i--;) {
- unsigned char c = bignum_byte(key->exponent, i);
- MD5Update(&md5c, &c, 1);
- }
- MD5Final(digest, &md5c);
-
- sprintf(buffer, "%d ", bignum_bitcount(key->modulus));
- for (i = 0; i < 16; i++)
- sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "",
- digest[i]);
- strncpy(str, buffer, len);
- str[len - 1] = '\0';
- slen = strlen(str);
- if (key->comment && slen < len - 1) {
- str[slen] = ' ';
- strncpy(str + slen + 1, key->comment, len - slen - 1);
- str[len - 1] = '\0';
- }
-}
-
-/*
- * Verify that the public data in an RSA key matches the private
- * data. We also check the private data itself: we ensure that p >
- * q and that iqmp really is the inverse of q mod p.
- */
-int rsa_verify(struct RSAKey *key)
-{
- Bignum n, ed, pm1, qm1;
- int cmp;
-
- /* n must equal pq. */
- n = bigmul(key->p, key->q);
- cmp = bignum_cmp(n, key->modulus);
- freebn(n);
- if (cmp != 0)
- return 0;
-
- /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */
- pm1 = copybn(key->p);
- decbn(pm1);
- ed = modmul(key->exponent, key->private_exponent, pm1);
- cmp = bignum_cmp(ed, One);
- sfree(ed);
- if (cmp != 0)
- return 0;
-
- qm1 = copybn(key->q);
- decbn(qm1);
- ed = modmul(key->exponent, key->private_exponent, qm1);
- cmp = bignum_cmp(ed, One);
- sfree(ed);
- if (cmp != 0)
- return 0;
-
- /*
- * 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) {
- 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.
- */
- n = modmul(key->iqmp, key->q, key->p);
- cmp = bignum_cmp(n, One);
- sfree(n);
- if (cmp != 0)
- return 0;
-
- return 1;
-}
-
-/* Public key blob as used by Pageant: exponent before modulus. */
-unsigned char *rsa_public_blob(struct RSAKey *key, int *len)
-{
- int length, pos;
- unsigned char *ret;
-
- length = (ssh1_bignum_length(key->modulus) +
- ssh1_bignum_length(key->exponent) + 4);
- ret = snewn(length, unsigned char);
-
- PUT_32BIT(ret, bignum_bitcount(key->modulus));
- pos = 4;
- pos += ssh1_write_bignum(ret + pos, key->exponent);
- pos += ssh1_write_bignum(ret + pos, key->modulus);
-
- *len = length;
- return ret;
-}
-
-/* Given a public blob, determine its length. */
-int rsa_public_blob_len(void *data, int maxlen)
-{
- unsigned char *p = (unsigned char *)data;
- int n;
-
- if (maxlen < 4)
- return -1;
- p += 4; /* length word */
- 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;
-}
-
-void freersakey(struct RSAKey *key)
-{
- if (key->modulus)
- freebn(key->modulus);
- if (key->exponent)
- 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);
-}
-
-/* ----------------------------------------------------------------------
- * Implementation of the ssh-rsa signing key type.
- */
-
-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;
- b = bignum_from_bytes((unsigned char *)p, length);
- return b;
-}
-
-static void *rsa2_newkey(char *data, int len)
-{
- char *p;
- int slen;
- struct RSAKey *rsa;
-
- rsa = snew(struct RSAKey);
- if (!rsa)
- return NULL;
- getstring(&data, &len, &p, &slen);
-
- if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
- sfree(rsa);
- return NULL;
- }
- 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;
-}
-
-static void rsa2_freekey(void *key)
-{
- struct RSAKey *rsa = (struct RSAKey *) key;
- freersakey(rsa);
- sfree(rsa);
-}
-
-static char *rsa2_fmtkey(void *key)
-{
- struct RSAKey *rsa = (struct RSAKey *) key;
- char *p;
- int len;
-
- len = rsastr_len(rsa);
- p = snewn(len, char);
- rsastr_fmt(p, rsa);
- return p;
-}
-
-static unsigned char *rsa2_public_blob(void *key, int *len)
-{
- struct RSAKey *rsa = (struct RSAKey *) key;
- int elen, mlen, bloblen;
- int i;
- unsigned char *blob, *p;
-
- elen = (bignum_bitcount(rsa->exponent) + 8) / 8;
- mlen = (bignum_bitcount(rsa->modulus) + 8) / 8;
-
- /*
- * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen.
- * (three length fields, 12+7=19).
- */
- bloblen = 19 + elen + mlen;
- blob = snewn(bloblen, unsigned char);
- p = blob;
- PUT_32BIT(p, 7);
- p += 4;
- memcpy(p, "ssh-rsa", 7);
- p += 7;
- PUT_32BIT(p, elen);
- p += 4;
- for (i = elen; i--;)
- *p++ = bignum_byte(rsa->exponent, i);
- PUT_32BIT(p, mlen);
- p += 4;
- for (i = mlen; i--;)
- *p++ = bignum_byte(rsa->modulus, i);
- assert(p == blob + bloblen);
- *len = bloblen;
- return blob;
-}
-
-static unsigned char *rsa2_private_blob(void *key, int *len)
-{
- struct RSAKey *rsa = (struct RSAKey *) key;
- int dlen, plen, qlen, ulen, bloblen;
- int i;
- unsigned char *blob, *p;
-
- dlen = (bignum_bitcount(rsa->private_exponent) + 8) / 8;
- plen = (bignum_bitcount(rsa->p) + 8) / 8;
- qlen = (bignum_bitcount(rsa->q) + 8) / 8;
- ulen = (bignum_bitcount(rsa->iqmp) + 8) / 8;
-
- /*
- * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 +
- * sum of lengths.
- */
- bloblen = 16 + dlen + plen + qlen + ulen;
- blob = snewn(bloblen, unsigned char);
- p = blob;
- PUT_32BIT(p, dlen);
- p += 4;
- for (i = dlen; i--;)
- *p++ = bignum_byte(rsa->private_exponent, i);
- PUT_32BIT(p, plen);
- p += 4;
- for (i = plen; i--;)
- *p++ = bignum_byte(rsa->p, i);
- PUT_32BIT(p, qlen);
- p += 4;
- for (i = qlen; i--;)
- *p++ = bignum_byte(rsa->q, i);
- PUT_32BIT(p, ulen);
- p += 4;
- for (i = ulen; i--;)
- *p++ = bignum_byte(rsa->iqmp, i);
- assert(p == blob + bloblen);
- *len = bloblen;
- return blob;
-}
-
-static void *rsa2_createkey(unsigned char *pub_blob, int pub_len,
- unsigned char *priv_blob, int priv_len)
-{
- struct RSAKey *rsa;
- char *pb = (char *) priv_blob;
-
- rsa = rsa2_newkey((char *) pub_blob, pub_len);
- rsa->private_exponent = getmp(&pb, &priv_len);
- rsa->p = getmp(&pb, &priv_len);
- rsa->q = getmp(&pb, &priv_len);
- rsa->iqmp = getmp(&pb, &priv_len);
-
- if (!rsa_verify(rsa)) {
- rsa2_freekey(rsa);
- return NULL;
- }
-
- return rsa;
-}
-
-static void *rsa2_openssh_createkey(unsigned char **blob, int *len)
-{
- char **b = (char **) blob;
- struct RSAKey *rsa;
-
- rsa = snew(struct RSAKey);
- if (!rsa)
- return NULL;
- rsa->comment = NULL;
-
- rsa->modulus = getmp(b, len);
- rsa->exponent = getmp(b, len);
- rsa->private_exponent = getmp(b, len);
- rsa->iqmp = getmp(b, len);
- rsa->p = getmp(b, len);
- rsa->q = getmp(b, len);
-
- if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent ||
- !rsa->iqmp || !rsa->p || !rsa->q) {
- sfree(rsa->modulus);
- sfree(rsa->exponent);
- sfree(rsa->private_exponent);
- sfree(rsa->iqmp);
- sfree(rsa->p);
- sfree(rsa->q);
- sfree(rsa);
- return NULL;
- }
-
- return rsa;
-}
-
-static int rsa2_openssh_fmtkey(void *key, unsigned char *blob, int len)
-{
- struct RSAKey *rsa = (struct RSAKey *) key;
- int bloblen, i;
-
- bloblen =
- ssh2_bignum_length(rsa->modulus) +
- ssh2_bignum_length(rsa->exponent) +
- ssh2_bignum_length(rsa->private_exponent) +
- ssh2_bignum_length(rsa->iqmp) +
- ssh2_bignum_length(rsa->p) + ssh2_bignum_length(rsa->q);
-
- 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(rsa->modulus);
- ENC(rsa->exponent);
- ENC(rsa->private_exponent);
- ENC(rsa->iqmp);
- ENC(rsa->p);
- ENC(rsa->q);
-
- 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;
- 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-rsa", 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(rsa->exponent);
- ADD_BIGNUM(rsa->modulus);
-#undef ADD_BIGNUM
-
- MD5Final(digest, &md5c);
-
- sprintf(buffer, "ssh-rsa %d ", bignum_bitcount(rsa->modulus));
- 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;
-}
-
-/*
- * This is the magic ASN.1/DER prefix that goes in the decoded
- * signature, between the string of FFs and the actual SHA hash
- * value. The meaning of it is:
- *
- * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself
- *
- * 30 21 -- a constructed SEQUENCE of length 0x21
- * 30 09 -- a constructed sub-SEQUENCE of length 9
- * 06 05 -- an object identifier, length 5
- * 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 }
- * (the 1,3 comes from 0x2B = 43 = 40*1+3)
- * 05 00 -- NULL
- * 04 14 -- a primitive OCTET STRING of length 0x14
- * [0x14 bytes of hash data follows]
- *
- * The object id in the middle there is listed as `id-sha1' in
- * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the
- * ASN module for PKCS #1) and its expanded form is as follows:
- *
- * id-sha1 OBJECT IDENTIFIER ::= {
- * iso(1) identified-organization(3) oiw(14) secsig(3)
- * algorithms(2) 26 }
- */
-static const unsigned char asn1_weird_stuff[] = {
- 0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B,
- 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14,
-};
-
-#define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) )
-
-static int rsa2_verifysig(void *key, char *sig, int siglen,
- char *data, int datalen)
-{
- struct RSAKey *rsa = (struct RSAKey *) key;
- Bignum in, out;
- char *p;
- int slen;
- int bytes, i, j, ret;
- unsigned char hash[20];
-
- getstring(&sig, &siglen, &p, &slen);
- if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
- return 0;
- }
- in = getmp(&sig, &siglen);
- out = modpow(in, rsa->exponent, rsa->modulus);
- freebn(in);
-
- ret = 1;
-
- bytes = (bignum_bitcount(rsa->modulus)+7) / 8;
- /* Top (partial) byte should be zero. */
- if (bignum_byte(out, bytes - 1) != 0)
- ret = 0;
- /* First whole byte should be 1. */
- if (bignum_byte(out, bytes - 2) != 1)
- ret = 0;
- /* Most of the rest should be FF. */
- for (i = bytes - 3; i >= 20 + ASN1_LEN; i--) {
- if (bignum_byte(out, i) != 0xFF)
- ret = 0;
- }
- /* Then we expect to see the asn1_weird_stuff. */
- for (i = 20 + ASN1_LEN - 1, j = 0; i >= 20; i--, j++) {
- if (bignum_byte(out, i) != asn1_weird_stuff[j])
- ret = 0;
- }
- /* Finally, we expect to see the SHA-1 hash of the signed data. */
- SHA_Simple(data, datalen, hash);
- for (i = 19, j = 0; i >= 0; i--, j++) {
- if (bignum_byte(out, i) != hash[j])
- ret = 0;
- }
- freebn(out);
-
- return ret;
-}
-
-static unsigned char *rsa2_sign(void *key, char *data, int datalen,
- int *siglen)
-{
- struct RSAKey *rsa = (struct RSAKey *) key;
- unsigned char *bytes;
- int nbytes;
- unsigned char hash[20];
- Bignum in, out;
- int i, j;
-
- SHA_Simple(data, datalen, hash);
-
- nbytes = (bignum_bitcount(rsa->modulus) - 1) / 8;
- assert(1 <= nbytes - 20 - ASN1_LEN);
- bytes = snewn(nbytes, unsigned char);
-
- bytes[0] = 1;
- for (i = 1; i < nbytes - 20 - ASN1_LEN; i++)
- bytes[i] = 0xFF;
- for (i = nbytes - 20 - ASN1_LEN, j = 0; i < nbytes - 20; i++, j++)
- bytes[i] = asn1_weird_stuff[j];
- for (i = nbytes - 20, j = 0; i < nbytes; i++, j++)
- bytes[i] = hash[j];
-
- in = bignum_from_bytes(bytes, nbytes);
- sfree(bytes);
-
- out = rsa_privkey_op(in, rsa);
- freebn(in);
-
- nbytes = (bignum_bitcount(out) + 7) / 8;
- bytes = snewn(4 + 7 + 4 + nbytes, unsigned char);
- PUT_32BIT(bytes, 7);
- memcpy(bytes + 4, "ssh-rsa", 7);
- PUT_32BIT(bytes + 4 + 7, nbytes);
- for (i = 0; i < nbytes; i++)
- bytes[4 + 7 + 4 + i] = bignum_byte(out, nbytes - 1 - i);
- freebn(out);
-
- *siglen = 4 + 7 + 4 + nbytes;
- return bytes;
-}
-
-const struct ssh_signkey ssh_rsa = {
- rsa2_newkey,
- rsa2_freekey,
- rsa2_fmtkey,
- rsa2_public_blob,
- rsa2_private_blob,
- 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
-};
+/*
+ * RSA implementation for PuTTY.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#include "ssh.h"
+#include "misc.h"
+
+int makekey(unsigned char *data, int len, struct RSAKey *result,
+ unsigned char **keystr, int order)
+{
+ unsigned char *p = data;
+ int i, n;
+
+ if (len < 4)
+ return -1;
+
+ if (result) {
+ result->bits = 0;
+ for (i = 0; i < 4; i++)
+ result->bits = (result->bits << 8) + *p++;
+ } 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) {
+ 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 = n - 2;
+ if (keystr)
+ *keystr = p + 2;
+ 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, int len, struct RSAKey *result)
+{
+ return ssh1_read_bignum(data, len, &result->private_exponent);
+}
+
+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;
+
+ for (i = 2; i < key->bytes - length - 1; i++) {
+ do {
+ data[i] = random_byte();
+ } while (data[i] == 0);
+ }
+ data[key->bytes - length - 1] = 0;
+
+ b1 = bignum_from_bytes(data, key->bytes);
+
+ b2 = modpow(b1, key->exponent, key->modulus);
+
+ p = data;
+ for (i = key->bytes; i--;) {
+ *p++ = bignum_byte(b2, i);
+ }
+
+ freebn(b1);
+ freebn(b2);
+
+ return 1;
+}
+
+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);
+ }
+ smemclr(lenbuf, 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;
+
+ 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);
+ }
+ bn_restore_invariant(random);
+
+ /*
+ * 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;
+ }
+
+ /*
+ * Also, make sure it has an inverse mod modulus.
+ */
+ random_inverse = modinv(random, key->modulus);
+ if (!random_inverse) {
+ freebn(random);
+ continue;
+ }
+
+ 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);
+ 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;
+ int mdlen, exlen;
+
+ md = key->modulus;
+ ex = key->exponent;
+ mdlen = (bignum_bitcount(md) + 15) / 16;
+ exlen = (bignum_bitcount(ex) + 15) / 16;
+ return 4 * (mdlen + exlen) + 20;
+}
+
+void rsastr_fmt(char *str, struct RSAKey *key)
+{
+ Bignum md, ex;
+ int len = 0, i, nibbles;
+ static const char hex[] = "0123456789abcdef";
+
+ md = key->modulus;
+ ex = key->exponent;
+
+ len += sprintf(str + len, "0x");
+
+ nibbles = (3 + bignum_bitcount(ex)) / 4;
+ if (nibbles < 1)
+ nibbles = 1;
+ for (i = nibbles; i--;)
+ str[len++] = hex[(bignum_byte(ex, i / 2) >> (4 * (i % 2))) & 0xF];
+
+ len += sprintf(str + len, ",0x");
+
+ nibbles = (3 + bignum_bitcount(md)) / 4;
+ if (nibbles < 1)
+ nibbles = 1;
+ for (i = nibbles; i--;)
+ str[len++] = hex[(bignum_byte(md, i / 2) >> (4 * (i % 2))) & 0xF];
+
+ str[len] = '\0';
+}
+
+/*
+ * Generate a fingerprint string for the key. Compatible with the
+ * OpenSSH fingerprint code.
+ */
+void rsa_fingerprint(char *str, int len, struct RSAKey *key)
+{
+ struct MD5Context md5c;
+ unsigned char digest[16];
+ char buffer[16 * 3 + 40];
+ int numlen, slen, i;
+
+ MD5Init(&md5c);
+ numlen = ssh1_bignum_length(key->modulus) - 2;
+ for (i = numlen; i--;) {
+ unsigned char c = bignum_byte(key->modulus, i);
+ MD5Update(&md5c, &c, 1);
+ }
+ numlen = ssh1_bignum_length(key->exponent) - 2;
+ for (i = numlen; i--;) {
+ unsigned char c = bignum_byte(key->exponent, i);
+ MD5Update(&md5c, &c, 1);
+ }
+ MD5Final(digest, &md5c);
+
+ sprintf(buffer, "%d ", bignum_bitcount(key->modulus));
+ for (i = 0; i < 16; i++)
+ sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "",
+ digest[i]);
+ strncpy(str, buffer, len);
+ str[len - 1] = '\0';
+ slen = strlen(str);
+ if (key->comment && slen < len - 1) {
+ str[slen] = ' ';
+ strncpy(str + slen + 1, key->comment, len - slen - 1);
+ str[len - 1] = '\0';
+ }
+}
+
+/*
+ * Verify that the public data in an RSA key matches the private
+ * data. We also check the private data itself: we ensure that p >
+ * q and that iqmp really is the inverse of q mod p.
+ */
+int rsa_verify(struct RSAKey *key)
+{
+ Bignum n, ed, pm1, qm1;
+ int cmp;
+
+ /* n must equal pq. */
+ n = bigmul(key->p, key->q);
+ cmp = bignum_cmp(n, key->modulus);
+ freebn(n);
+ if (cmp != 0)
+ return 0;
+
+ /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */
+ pm1 = copybn(key->p);
+ decbn(pm1);
+ ed = modmul(key->exponent, key->private_exponent, pm1);
+ freebn(pm1);
+ cmp = bignum_cmp(ed, One);
+ freebn(ed);
+ if (cmp != 0)
+ return 0;
+
+ qm1 = copybn(key->q);
+ decbn(qm1);
+ ed = modmul(key->exponent, key->private_exponent, qm1);
+ freebn(qm1);
+ cmp = bignum_cmp(ed, One);
+ freebn(ed);
+ if (cmp != 0)
+ return 0;
+
+ /*
+ * 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) {
+ Bignum tmp = key->p;
+ key->p = key->q;
+ key->q = tmp;
+
+ freebn(key->iqmp);
+ key->iqmp = modinv(key->q, key->p);
+ if (!key->iqmp)
+ return 0;
+ }
+
+ /*
+ * Ensure iqmp * q is congruent to 1, modulo p.
+ */
+ n = modmul(key->iqmp, key->q, key->p);
+ cmp = bignum_cmp(n, One);
+ freebn(n);
+ if (cmp != 0)
+ return 0;
+
+ return 1;
+}
+
+/* Public key blob as used by Pageant: exponent before modulus. */
+unsigned char *rsa_public_blob(struct RSAKey *key, int *len)
+{
+ int length, pos;
+ unsigned char *ret;
+
+ length = (ssh1_bignum_length(key->modulus) +
+ ssh1_bignum_length(key->exponent) + 4);
+ ret = snewn(length, unsigned char);
+
+ PUT_32BIT(ret, bignum_bitcount(key->modulus));
+ pos = 4;
+ pos += ssh1_write_bignum(ret + pos, key->exponent);
+ pos += ssh1_write_bignum(ret + pos, key->modulus);
+
+ *len = length;
+ return ret;
+}
+
+/* Given a public blob, determine its length. */
+int rsa_public_blob_len(void *data, int maxlen)
+{
+ unsigned char *p = (unsigned char *)data;
+ int n;
+
+ if (maxlen < 4)
+ return -1;
+ p += 4; /* length word */
+ 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;
+}
+
+void freersakey(struct RSAKey *key)
+{
+ if (key->modulus)
+ freebn(key->modulus);
+ if (key->exponent)
+ 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);
+}
+
+/* ----------------------------------------------------------------------
+ * Implementation of the ssh-rsa signing key type.
+ */
+
+static void getstring(char **data, int *datalen, char **p, int *length)
+{
+ *p = NULL;
+ if (*datalen < 4)
+ return;
+ *length = toint(GET_32BIT(*data));
+ if (*length < 0)
+ return;
+ *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;
+ b = bignum_from_bytes((unsigned char *)p, length);
+ return b;
+}
+
+static void rsa2_freekey(void *key); /* forward reference */
+
+static void *rsa2_newkey(char *data, int len)
+{
+ char *p;
+ int slen;
+ struct RSAKey *rsa;
+
+ rsa = snew(struct RSAKey);
+ getstring(&data, &len, &p, &slen);
+
+ if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
+ sfree(rsa);
+ return NULL;
+ }
+ rsa->exponent = getmp(&data, &len);
+ rsa->modulus = getmp(&data, &len);
+ rsa->private_exponent = NULL;
+ rsa->p = rsa->q = rsa->iqmp = NULL;
+ rsa->comment = NULL;
+
+ if (!rsa->exponent || !rsa->modulus) {
+ rsa2_freekey(rsa);
+ return NULL;
+ }
+
+ return rsa;
+}
+
+static void rsa2_freekey(void *key)
+{
+ struct RSAKey *rsa = (struct RSAKey *) key;
+ freersakey(rsa);
+ sfree(rsa);
+}
+
+static char *rsa2_fmtkey(void *key)
+{
+ struct RSAKey *rsa = (struct RSAKey *) key;
+ char *p;
+ int len;
+
+ len = rsastr_len(rsa);
+ p = snewn(len, char);
+ rsastr_fmt(p, rsa);
+ return p;
+}
+
+static unsigned char *rsa2_public_blob(void *key, int *len)
+{
+ struct RSAKey *rsa = (struct RSAKey *) key;
+ int elen, mlen, bloblen;
+ int i;
+ unsigned char *blob, *p;
+
+ elen = (bignum_bitcount(rsa->exponent) + 8) / 8;
+ mlen = (bignum_bitcount(rsa->modulus) + 8) / 8;
+
+ /*
+ * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen.
+ * (three length fields, 12+7=19).
+ */
+ bloblen = 19 + elen + mlen;
+ blob = snewn(bloblen, unsigned char);
+ p = blob;
+ PUT_32BIT(p, 7);
+ p += 4;
+ memcpy(p, "ssh-rsa", 7);
+ p += 7;
+ PUT_32BIT(p, elen);
+ p += 4;
+ for (i = elen; i--;)
+ *p++ = bignum_byte(rsa->exponent, i);
+ PUT_32BIT(p, mlen);
+ p += 4;
+ for (i = mlen; i--;)
+ *p++ = bignum_byte(rsa->modulus, i);
+ assert(p == blob + bloblen);
+ *len = bloblen;
+ return blob;
+}
+
+static unsigned char *rsa2_private_blob(void *key, int *len)
+{
+ struct RSAKey *rsa = (struct RSAKey *) key;
+ int dlen, plen, qlen, ulen, bloblen;
+ int i;
+ unsigned char *blob, *p;
+
+ dlen = (bignum_bitcount(rsa->private_exponent) + 8) / 8;
+ plen = (bignum_bitcount(rsa->p) + 8) / 8;
+ qlen = (bignum_bitcount(rsa->q) + 8) / 8;
+ ulen = (bignum_bitcount(rsa->iqmp) + 8) / 8;
+
+ /*
+ * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 +
+ * sum of lengths.
+ */
+ bloblen = 16 + dlen + plen + qlen + ulen;
+ blob = snewn(bloblen, unsigned char);
+ p = blob;
+ PUT_32BIT(p, dlen);
+ p += 4;
+ for (i = dlen; i--;)
+ *p++ = bignum_byte(rsa->private_exponent, i);
+ PUT_32BIT(p, plen);
+ p += 4;
+ for (i = plen; i--;)
+ *p++ = bignum_byte(rsa->p, i);
+ PUT_32BIT(p, qlen);
+ p += 4;
+ for (i = qlen; i--;)
+ *p++ = bignum_byte(rsa->q, i);
+ PUT_32BIT(p, ulen);
+ p += 4;
+ for (i = ulen; i--;)
+ *p++ = bignum_byte(rsa->iqmp, i);
+ assert(p == blob + bloblen);
+ *len = bloblen;
+ return blob;
+}
+
+static void *rsa2_createkey(unsigned char *pub_blob, int pub_len,
+ unsigned char *priv_blob, int priv_len)
+{
+ struct RSAKey *rsa;
+ char *pb = (char *) priv_blob;
+
+ rsa = rsa2_newkey((char *) pub_blob, pub_len);
+ rsa->private_exponent = getmp(&pb, &priv_len);
+ rsa->p = getmp(&pb, &priv_len);
+ rsa->q = getmp(&pb, &priv_len);
+ rsa->iqmp = getmp(&pb, &priv_len);
+
+ if (!rsa_verify(rsa)) {
+ rsa2_freekey(rsa);
+ return NULL;
+ }
+
+ return rsa;
+}
+
+static void *rsa2_openssh_createkey(unsigned char **blob, int *len)
+{
+ char **b = (char **) blob;
+ struct RSAKey *rsa;
+
+ rsa = snew(struct RSAKey);
+ rsa->comment = NULL;
+
+ rsa->modulus = getmp(b, len);
+ rsa->exponent = getmp(b, len);
+ rsa->private_exponent = getmp(b, len);
+ rsa->iqmp = getmp(b, len);
+ rsa->p = getmp(b, len);
+ rsa->q = getmp(b, len);
+
+ if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent ||
+ !rsa->iqmp || !rsa->p || !rsa->q) {
+ rsa2_freekey(rsa);
+ return NULL;
+ }
+
+ if (!rsa_verify(rsa)) {
+ rsa2_freekey(rsa);
+ return NULL;
+ }
+
+ return rsa;
+}
+
+static int rsa2_openssh_fmtkey(void *key, unsigned char *blob, int len)
+{
+ struct RSAKey *rsa = (struct RSAKey *) key;
+ int bloblen, i;
+
+ bloblen =
+ ssh2_bignum_length(rsa->modulus) +
+ ssh2_bignum_length(rsa->exponent) +
+ ssh2_bignum_length(rsa->private_exponent) +
+ ssh2_bignum_length(rsa->iqmp) +
+ ssh2_bignum_length(rsa->p) + ssh2_bignum_length(rsa->q);
+
+ 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(rsa->modulus);
+ ENC(rsa->exponent);
+ ENC(rsa->private_exponent);
+ ENC(rsa->iqmp);
+ ENC(rsa->p);
+ ENC(rsa->q);
+
+ 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;
+ 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-rsa", 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(rsa->exponent);
+ ADD_BIGNUM(rsa->modulus);
+#undef ADD_BIGNUM
+
+ MD5Final(digest, &md5c);
+
+ sprintf(buffer, "ssh-rsa %d ", bignum_bitcount(rsa->modulus));
+ 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;
+}
+
+/*
+ * This is the magic ASN.1/DER prefix that goes in the decoded
+ * signature, between the string of FFs and the actual SHA hash
+ * value. The meaning of it is:
+ *
+ * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself
+ *
+ * 30 21 -- a constructed SEQUENCE of length 0x21
+ * 30 09 -- a constructed sub-SEQUENCE of length 9
+ * 06 05 -- an object identifier, length 5
+ * 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 }
+ * (the 1,3 comes from 0x2B = 43 = 40*1+3)
+ * 05 00 -- NULL
+ * 04 14 -- a primitive OCTET STRING of length 0x14
+ * [0x14 bytes of hash data follows]
+ *
+ * The object id in the middle there is listed as `id-sha1' in
+ * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the
+ * ASN module for PKCS #1) and its expanded form is as follows:
+ *
+ * id-sha1 OBJECT IDENTIFIER ::= {
+ * iso(1) identified-organization(3) oiw(14) secsig(3)
+ * algorithms(2) 26 }
+ */
+static const unsigned char asn1_weird_stuff[] = {
+ 0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B,
+ 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14,
+};
+
+#define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) )
+
+static int rsa2_verifysig(void *key, char *sig, int siglen,
+ char *data, int datalen)
+{
+ struct RSAKey *rsa = (struct RSAKey *) key;
+ Bignum in, out;
+ char *p;
+ int slen;
+ int bytes, i, j, ret;
+ unsigned char hash[20];
+
+ getstring(&sig, &siglen, &p, &slen);
+ if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
+ return 0;
+ }
+ in = getmp(&sig, &siglen);
+ if (!in)
+ return 0;
+ out = modpow(in, rsa->exponent, rsa->modulus);
+ freebn(in);
+
+ ret = 1;
+
+ bytes = (bignum_bitcount(rsa->modulus)+7) / 8;
+ /* Top (partial) byte should be zero. */
+ if (bignum_byte(out, bytes - 1) != 0)
+ ret = 0;
+ /* First whole byte should be 1. */
+ if (bignum_byte(out, bytes - 2) != 1)
+ ret = 0;
+ /* Most of the rest should be FF. */
+ for (i = bytes - 3; i >= 20 + ASN1_LEN; i--) {
+ if (bignum_byte(out, i) != 0xFF)
+ ret = 0;
+ }
+ /* Then we expect to see the asn1_weird_stuff. */
+ for (i = 20 + ASN1_LEN - 1, j = 0; i >= 20; i--, j++) {
+ if (bignum_byte(out, i) != asn1_weird_stuff[j])
+ ret = 0;
+ }
+ /* Finally, we expect to see the SHA-1 hash of the signed data. */
+ SHA_Simple(data, datalen, hash);
+ for (i = 19, j = 0; i >= 0; i--, j++) {
+ if (bignum_byte(out, i) != hash[j])
+ ret = 0;
+ }
+ freebn(out);
+
+ return ret;
+}
+
+static unsigned char *rsa2_sign(void *key, char *data, int datalen,
+ int *siglen)
+{
+ struct RSAKey *rsa = (struct RSAKey *) key;
+ unsigned char *bytes;
+ int nbytes;
+ unsigned char hash[20];
+ Bignum in, out;
+ int i, j;
+
+ SHA_Simple(data, datalen, hash);
+
+ nbytes = (bignum_bitcount(rsa->modulus) - 1) / 8;
+ assert(1 <= nbytes - 20 - ASN1_LEN);
+ bytes = snewn(nbytes, unsigned char);
+
+ bytes[0] = 1;
+ for (i = 1; i < nbytes - 20 - ASN1_LEN; i++)
+ bytes[i] = 0xFF;
+ for (i = nbytes - 20 - ASN1_LEN, j = 0; i < nbytes - 20; i++, j++)
+ bytes[i] = asn1_weird_stuff[j];
+ for (i = nbytes - 20, j = 0; i < nbytes; i++, j++)
+ bytes[i] = hash[j];
+
+ in = bignum_from_bytes(bytes, nbytes);
+ sfree(bytes);
+
+ out = rsa_privkey_op(in, rsa);
+ freebn(in);
+
+ nbytes = (bignum_bitcount(out) + 7) / 8;
+ bytes = snewn(4 + 7 + 4 + nbytes, unsigned char);
+ PUT_32BIT(bytes, 7);
+ memcpy(bytes + 4, "ssh-rsa", 7);
+ PUT_32BIT(bytes + 4 + 7, nbytes);
+ for (i = 0; i < nbytes; i++)
+ bytes[4 + 7 + 4 + i] = bignum_byte(out, nbytes - 1 - i);
+ freebn(out);
+
+ *siglen = 4 + 7 + 4 + nbytes;
+ return bytes;
+}
+
+const struct ssh_signkey ssh_rsa = {
+ rsa2_newkey,
+ rsa2_freekey,
+ rsa2_fmtkey,
+ rsa2_public_blob,
+ rsa2_private_blob,
+ 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
+};
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-23 06:58:17 +0000