diff options
Diffstat (limited to 'SSHRSA.C')
| -rw-r--r-- | SSHRSA.C | 1109 |
1 files changed, 0 insertions, 1109 deletions
diff --git a/SSHRSA.C b/SSHRSA.C deleted file mode 100644 index e3dcbdda..00000000 --- a/SSHRSA.C +++ /dev/null @@ -1,1109 +0,0 @@ -/* - * RSA implementation for PuTTY. - */ - -#include <stdio.h> -#include <stdlib.h> -#include <string.h> -#include <assert.h> - -#include "ssh.h" -#include "mpint.h" -#include "misc.h" - -void BinarySource_get_rsa_ssh1_pub( - BinarySource *src, RSAKey *rsa, RsaSsh1Order order) -{ - unsigned bits; - mp_int *e, *m; - - bits = get_uint32(src); - if (order == RSA_SSH1_EXPONENT_FIRST) { - e = get_mp_ssh1(src); - m = get_mp_ssh1(src); - } else { - m = get_mp_ssh1(src); - e = get_mp_ssh1(src); - } - - if (rsa) { - rsa->bits = bits; - rsa->exponent = e; - rsa->modulus = m; - rsa->bytes = (mp_get_nbits(m) + 7) / 8; - } else { - mp_free(e); - mp_free(m); - } -} - -void BinarySource_get_rsa_ssh1_priv( - BinarySource *src, RSAKey *rsa) -{ - rsa->private_exponent = get_mp_ssh1(src); -} - -key_components *rsa_components(RSAKey *rsa) -{ - key_components *kc = key_components_new(); - key_components_add_text(kc, "key_type", "RSA"); - key_components_add_mp(kc, "public_modulus", rsa->modulus); - key_components_add_mp(kc, "public_exponent", rsa->exponent); - if (rsa->private_exponent) { - key_components_add_mp(kc, "private_exponent", rsa->private_exponent); - key_components_add_mp(kc, "private_p", rsa->p); - key_components_add_mp(kc, "private_q", rsa->q); - key_components_add_mp(kc, "private_inverse_q_mod_p", rsa->iqmp); - } - return kc; -} - -RSAKey *BinarySource_get_rsa_ssh1_priv_agent(BinarySource *src) -{ - RSAKey *rsa = snew(RSAKey); - memset(rsa, 0, sizeof(RSAKey)); - - get_rsa_ssh1_pub(src, rsa, RSA_SSH1_MODULUS_FIRST); - get_rsa_ssh1_priv(src, rsa); - - /* SSH-1 names p and q the other way round, i.e. we have the - * inverse of p mod q and not of q mod p. We swap the names, - * because our internal RSA wants iqmp. */ - rsa->iqmp = get_mp_ssh1(src); - rsa->q = get_mp_ssh1(src); - rsa->p = get_mp_ssh1(src); - - return rsa; -} - -bool rsa_ssh1_encrypt(unsigned char *data, int length, RSAKey *key) -{ - mp_int *b1, *b2; - int i; - unsigned char *p; - - if (key->bytes < length + 4) - return false; /* RSA key too short! */ - - memmove(data + key->bytes - length, data, length); - data[0] = 0; - data[1] = 2; - - size_t npad = key->bytes - length - 3; - /* - * Generate a sequence of nonzero padding bytes. We do this in a - * reasonably uniform way and without having to loop round - * retrying the random number generation, by first generating an - * integer in [0,2^n) for an appropriately large n; then we - * repeatedly multiply by 255 to give an integer in [0,255*2^n), - * extract the top 8 bits to give an integer in [0,255), and mask - * those bits off before multiplying up again for the next digit. - * This gives us a sequence of numbers in [0,255), and of course - * adding 1 to each of them gives numbers in [1,256) as we wanted. - * - * (You could imagine this being a sort of fixed-point operation: - * given a uniformly random binary _fraction_, multiplying it by k - * and subtracting off the integer part will yield you a sequence - * of integers each in [0,k). I'm just doing that scaled up by a - * power of 2 to avoid the fractions.) - */ - size_t random_bits = (npad + 16) * 8; - mp_int *randval = mp_new(random_bits + 8); - mp_int *tmp = mp_random_bits(random_bits); - mp_copy_into(randval, tmp); - mp_free(tmp); - for (i = 2; i < key->bytes - length - 1; i++) { - mp_mul_integer_into(randval, randval, 255); - uint8_t byte = mp_get_byte(randval, random_bits / 8); - assert(byte != 255); - data[i] = byte + 1; - mp_reduce_mod_2to(randval, random_bits); - } - mp_free(randval); - data[key->bytes - length - 1] = 0; - - b1 = mp_from_bytes_be(make_ptrlen(data, key->bytes)); - - b2 = mp_modpow(b1, key->exponent, key->modulus); - - p = data; - for (i = key->bytes; i--;) { - *p++ = mp_get_byte(b2, i); - } - - mp_free(b1); - mp_free(b2); - - return true; -} - -/* - * 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. - */ -static mp_int *crt_modpow(mp_int *base, mp_int *exp, mp_int *mod, - mp_int *p, mp_int *q, mp_int *iqmp) -{ - mp_int *pm1, *qm1, *pexp, *qexp, *presult, *qresult; - mp_int *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 = mp_copy(p); - mp_sub_integer_into(pm1, pm1, 1); - qm1 = mp_copy(q); - mp_sub_integer_into(qm1, qm1, 1); - pexp = mp_mod(exp, pm1); - qexp = mp_mod(exp, qm1); - - /* - * Do the two modpows. - */ - mp_int *base_mod_p = mp_mod(base, p); - presult = mp_modpow(base_mod_p, pexp, p); - mp_free(base_mod_p); - mp_int *base_mod_q = mp_mod(base, q); - qresult = mp_modpow(base_mod_q, qexp, q); - mp_free(base_mod_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 presult-qresult < 0, we add p to it to keep it positive.) - */ - unsigned presult_too_small = mp_cmp_hs(qresult, presult); - mp_cond_add_into(presult, presult, p, presult_too_small); - - diff = mp_sub(presult, qresult); - multiplier = mp_mul(iqmp, q); - ret0 = mp_mul(multiplier, diff); - mp_add_into(ret0, ret0, qresult); - - /* - * Finally, reduce the result mod n. - */ - ret = mp_mod(ret0, mod); - - /* - * Free all the intermediate results before returning. - */ - mp_free(pm1); - mp_free(qm1); - mp_free(pexp); - mp_free(qexp); - mp_free(presult); - mp_free(qresult); - mp_free(diff); - mp_free(multiplier); - mp_free(ret0); - - return ret; -} - -/* - * Wrapper on crt_modpow that looks up all the right values from an - * RSAKey. - */ -static mp_int *rsa_privkey_op(mp_int *input, RSAKey *key) -{ - return crt_modpow(input, key->private_exponent, - key->modulus, key->p, key->q, key->iqmp); -} - -mp_int *rsa_ssh1_decrypt(mp_int *input, RSAKey *key) -{ - return rsa_privkey_op(input, key); -} - -bool rsa_ssh1_decrypt_pkcs1(mp_int *input, RSAKey *key, - strbuf *outbuf) -{ - strbuf *data = strbuf_new_nm(); - bool success = false; - BinarySource src[1]; - - { - mp_int *b = rsa_ssh1_decrypt(input, key); - for (size_t i = (mp_get_nbits(key->modulus) + 7) / 8; i-- > 0 ;) { - put_byte(data, mp_get_byte(b, i)); - } - mp_free(b); - } - - BinarySource_BARE_INIT(src, data->u, data->len); - - /* Check PKCS#1 formatting prefix */ - if (get_byte(src) != 0) goto out; - if (get_byte(src) != 2) goto out; - while (1) { - unsigned char byte = get_byte(src); - if (get_err(src)) goto out; - if (byte == 0) - break; - } - - /* Everything else is the payload */ - success = true; - put_data(outbuf, get_ptr(src), get_avail(src)); - - out: - strbuf_free(data); - return success; -} - -static void append_hex_to_strbuf(strbuf *sb, mp_int *x) -{ - if (sb->len > 0) - put_byte(sb, ','); - put_data(sb, "0x", 2); - char *hex = mp_get_hex(x); - size_t hexlen = strlen(hex); - put_data(sb, hex, hexlen); - smemclr(hex, hexlen); - sfree(hex); -} - -char *rsastr_fmt(RSAKey *key) -{ - strbuf *sb = strbuf_new(); - - append_hex_to_strbuf(sb, key->exponent); - append_hex_to_strbuf(sb, key->modulus); - - return strbuf_to_str(sb); -} - -/* - * Generate a fingerprint string for the key. Compatible with the - * OpenSSH fingerprint code. - */ -char *rsa_ssh1_fingerprint(RSAKey *key) -{ - unsigned char digest[16]; - strbuf *out; - int i; - - /* - * The hash preimage for SSH-1 key fingerprinting consists of the - * modulus and exponent _without_ any preceding length field - - * just the minimum number of bytes to represent each integer, - * stored big-endian, concatenated with no marker at the division - * between them. - */ - - ssh_hash *hash = ssh_hash_new(&ssh_md5); - for (size_t i = (mp_get_nbits(key->modulus) + 7) / 8; i-- > 0 ;) - put_byte(hash, mp_get_byte(key->modulus, i)); - for (size_t i = (mp_get_nbits(key->exponent) + 7) / 8; i-- > 0 ;) - put_byte(hash, mp_get_byte(key->exponent, i)); - ssh_hash_final(hash, digest); - - out = strbuf_new(); - strbuf_catf(out, "%"SIZEu" ", mp_get_nbits(key->modulus)); - for (i = 0; i < 16; i++) - strbuf_catf(out, "%s%02x", i ? ":" : "", digest[i]); - if (key->comment) - strbuf_catf(out, " %s", key->comment); - return strbuf_to_str(out); -} - -/* - * Wrap the output of rsa_ssh1_fingerprint up into the same kind of - * structure that comes from ssh2_all_fingerprints. - */ -char **rsa_ssh1_fake_all_fingerprints(RSAKey *key) -{ - char **ret = snewn(SSH_N_FPTYPES, char *); - for (unsigned i = 0; i < SSH_N_FPTYPES; i++) - ret[i] = NULL; - ret[SSH_FPTYPE_MD5] = rsa_ssh1_fingerprint(key); - return ret; -} - -/* - * 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. - */ -bool rsa_verify(RSAKey *key) -{ - mp_int *n, *ed, *pm1, *qm1; - unsigned ok = 1; - - /* Preliminary checks: p,q can't be 0 or 1. (Of course no other - * very small value is any good either, but these are the values - * we _must_ check for to avoid assertion failures further down - * this function.) */ - if (!(mp_hs_integer(key->p, 2) & mp_hs_integer(key->q, 2))) - return false; - - /* n must equal pq. */ - n = mp_mul(key->p, key->q); - ok &= mp_cmp_eq(n, key->modulus); - mp_free(n); - - /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */ - pm1 = mp_copy(key->p); - mp_sub_integer_into(pm1, pm1, 1); - ed = mp_modmul(key->exponent, key->private_exponent, pm1); - mp_free(pm1); - ok &= mp_eq_integer(ed, 1); - mp_free(ed); - - qm1 = mp_copy(key->q); - mp_sub_integer_into(qm1, qm1, 1); - ed = mp_modmul(key->exponent, key->private_exponent, qm1); - mp_free(qm1); - ok &= mp_eq_integer(ed, 1); - mp_free(ed); - - /* - * 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. - */ - mp_int *p_new = mp_max(key->p, key->q); - mp_int *q_new = mp_min(key->p, key->q); - mp_free(key->p); - mp_free(key->q); - mp_free(key->iqmp); - key->p = p_new; - key->q = q_new; - key->iqmp = mp_invert(key->q, key->p); - - return ok; -} - -void rsa_ssh1_public_blob(BinarySink *bs, RSAKey *key, - RsaSsh1Order order) -{ - put_uint32(bs, mp_get_nbits(key->modulus)); - if (order == RSA_SSH1_EXPONENT_FIRST) { - put_mp_ssh1(bs, key->exponent); - put_mp_ssh1(bs, key->modulus); - } else { - put_mp_ssh1(bs, key->modulus); - put_mp_ssh1(bs, key->exponent); - } -} - -void rsa_ssh1_private_blob_agent(BinarySink *bs, RSAKey *key) -{ - rsa_ssh1_public_blob(bs, key, RSA_SSH1_MODULUS_FIRST); - put_mp_ssh1(bs, key->private_exponent); - put_mp_ssh1(bs, key->iqmp); - put_mp_ssh1(bs, key->q); - put_mp_ssh1(bs, key->p); -} - -/* Given an SSH-1 public key blob, determine its length. */ -int rsa_ssh1_public_blob_len(ptrlen data) -{ - BinarySource src[1]; - - BinarySource_BARE_INIT_PL(src, data); - - /* Expect a length word, then exponent and modulus. (It doesn't - * even matter which order.) */ - get_uint32(src); - mp_free(get_mp_ssh1(src)); - mp_free(get_mp_ssh1(src)); - - if (get_err(src)) - return -1; - - /* Return the number of bytes consumed. */ - return src->pos; -} - -void freersapriv(RSAKey *key) -{ - if (key->private_exponent) { - mp_free(key->private_exponent); - key->private_exponent = NULL; - } - if (key->p) { - mp_free(key->p); - key->p = NULL; - } - if (key->q) { - mp_free(key->q); - key->q = NULL; - } - if (key->iqmp) { - mp_free(key->iqmp); - key->iqmp = NULL; - } -} - -void freersakey(RSAKey *key) -{ - freersapriv(key); - if (key->modulus) { - mp_free(key->modulus); - key->modulus = NULL; - } - if (key->exponent) { - mp_free(key->exponent); - key->exponent = NULL; - } - if (key->comment) { - sfree(key->comment); - key->comment = NULL; - } -} - -/* ---------------------------------------------------------------------- - * Implementation of the ssh-rsa signing key type family. - */ - -struct ssh2_rsa_extra { - unsigned signflags; -}; - -static void rsa2_freekey(ssh_key *key); /* forward reference */ - -static ssh_key *rsa2_new_pub(const ssh_keyalg *self, ptrlen data) -{ - BinarySource src[1]; - RSAKey *rsa; - - BinarySource_BARE_INIT_PL(src, data); - if (!ptrlen_eq_string(get_string(src), "ssh-rsa")) - return NULL; - - rsa = snew(RSAKey); - rsa->sshk.vt = self; - rsa->exponent = get_mp_ssh2(src); - rsa->modulus = get_mp_ssh2(src); - rsa->private_exponent = NULL; - rsa->p = rsa->q = rsa->iqmp = NULL; - rsa->comment = NULL; - - if (get_err(src)) { - rsa2_freekey(&rsa->sshk); - return NULL; - } - - return &rsa->sshk; -} - -static void rsa2_freekey(ssh_key *key) -{ - RSAKey *rsa = container_of(key, RSAKey, sshk); - freersakey(rsa); - sfree(rsa); -} - -static char *rsa2_cache_str(ssh_key *key) -{ - RSAKey *rsa = container_of(key, RSAKey, sshk); - return rsastr_fmt(rsa); -} - -static key_components *rsa2_components(ssh_key *key) -{ - RSAKey *rsa = container_of(key, RSAKey, sshk); - return rsa_components(rsa); -} - -static void rsa2_public_blob(ssh_key *key, BinarySink *bs) -{ - RSAKey *rsa = container_of(key, RSAKey, sshk); - - put_stringz(bs, "ssh-rsa"); - put_mp_ssh2(bs, rsa->exponent); - put_mp_ssh2(bs, rsa->modulus); -} - -static void rsa2_private_blob(ssh_key *key, BinarySink *bs) -{ - RSAKey *rsa = container_of(key, RSAKey, sshk); - - put_mp_ssh2(bs, rsa->private_exponent); - put_mp_ssh2(bs, rsa->p); - put_mp_ssh2(bs, rsa->q); - put_mp_ssh2(bs, rsa->iqmp); -} - -static ssh_key *rsa2_new_priv(const ssh_keyalg *self, - ptrlen pub, ptrlen priv) -{ - BinarySource src[1]; - ssh_key *sshk; - RSAKey *rsa; - - sshk = rsa2_new_pub(self, pub); - if (!sshk) - return NULL; - - rsa = container_of(sshk, RSAKey, sshk); - BinarySource_BARE_INIT_PL(src, priv); - rsa->private_exponent = get_mp_ssh2(src); - rsa->p = get_mp_ssh2(src); - rsa->q = get_mp_ssh2(src); - rsa->iqmp = get_mp_ssh2(src); - - if (get_err(src) || !rsa_verify(rsa)) { - rsa2_freekey(&rsa->sshk); - return NULL; - } - - return &rsa->sshk; -} - -static ssh_key *rsa2_new_priv_openssh(const ssh_keyalg *self, - BinarySource *src) -{ - RSAKey *rsa; - - rsa = snew(RSAKey); - rsa->sshk.vt = &ssh_rsa; - rsa->comment = NULL; - - rsa->modulus = get_mp_ssh2(src); - rsa->exponent = get_mp_ssh2(src); - rsa->private_exponent = get_mp_ssh2(src); - rsa->iqmp = get_mp_ssh2(src); - rsa->p = get_mp_ssh2(src); - rsa->q = get_mp_ssh2(src); - - if (get_err(src) || !rsa_verify(rsa)) { - rsa2_freekey(&rsa->sshk); - return NULL; - } - - return &rsa->sshk; -} - -static void rsa2_openssh_blob(ssh_key *key, BinarySink *bs) -{ - RSAKey *rsa = container_of(key, RSAKey, sshk); - - put_mp_ssh2(bs, rsa->modulus); - put_mp_ssh2(bs, rsa->exponent); - put_mp_ssh2(bs, rsa->private_exponent); - put_mp_ssh2(bs, rsa->iqmp); - put_mp_ssh2(bs, rsa->p); - put_mp_ssh2(bs, rsa->q); -} - -static int rsa2_pubkey_bits(const ssh_keyalg *self, ptrlen pub) -{ - ssh_key *sshk; - RSAKey *rsa; - int ret; - - sshk = rsa2_new_pub(self, pub); - if (!sshk) - return -1; - - rsa = container_of(sshk, RSAKey, sshk); - ret = mp_get_nbits(rsa->modulus); - rsa2_freekey(&rsa->sshk); - - return ret; -} - -static inline const ssh_hashalg *rsa2_hash_alg_for_flags( - unsigned flags, const char **protocol_id_out) -{ - const ssh_hashalg *halg; - const char *protocol_id; - - if (flags & SSH_AGENT_RSA_SHA2_256) { - halg = &ssh_sha256; - protocol_id = "rsa-sha2-256"; - } else if (flags & SSH_AGENT_RSA_SHA2_512) { - halg = &ssh_sha512; - protocol_id = "rsa-sha2-512"; - } else { - halg = &ssh_sha1; - protocol_id = "ssh-rsa"; - } - - if (protocol_id_out) - *protocol_id_out = protocol_id; - - return halg; -} - -static inline ptrlen rsa_pkcs1_prefix_for_hash(const ssh_hashalg *halg) -{ - if (halg == &ssh_sha1) { - /* - * This is the magic ASN.1/DER prefix that goes in the decoded - * signature, between the string of FFs and the actual SHA-1 - * 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 sha1_asn1_prefix[] = { - 0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B, - 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14, - }; - return PTRLEN_FROM_CONST_BYTES(sha1_asn1_prefix); - } - - if (halg == &ssh_sha256) { - /* - * A similar piece of ASN.1 used for signatures using SHA-256, - * in the same format but differing only in various length - * fields and OID. - */ - static const unsigned char sha256_asn1_prefix[] = { - 0x00, 0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, - 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, - 0x05, 0x00, 0x04, 0x20, - }; - return PTRLEN_FROM_CONST_BYTES(sha256_asn1_prefix); - } - - if (halg == &ssh_sha512) { - /* - * And one more for SHA-512. - */ - static const unsigned char sha512_asn1_prefix[] = { - 0x00, 0x30, 0x51, 0x30, 0x0d, 0x06, 0x09, 0x60, - 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, - 0x05, 0x00, 0x04, 0x40, - }; - return PTRLEN_FROM_CONST_BYTES(sha512_asn1_prefix); - } - - unreachable("bad hash algorithm for RSA PKCS#1"); -} - -static inline size_t rsa_pkcs1_length_of_fixed_parts(const ssh_hashalg *halg) -{ - ptrlen asn1_prefix = rsa_pkcs1_prefix_for_hash(halg); - return halg->hlen + asn1_prefix.len + 2; -} - -static unsigned char *rsa_pkcs1_signature_string( - size_t nbytes, const ssh_hashalg *halg, ptrlen data) -{ - size_t fixed_parts = rsa_pkcs1_length_of_fixed_parts(halg); - assert(nbytes >= fixed_parts); - size_t padding = nbytes - fixed_parts; - - ptrlen asn1_prefix = rsa_pkcs1_prefix_for_hash(halg); - - unsigned char *bytes = snewn(nbytes, unsigned char); - - bytes[0] = 0; - bytes[1] = 1; - - memset(bytes + 2, 0xFF, padding); - - memcpy(bytes + 2 + padding, asn1_prefix.ptr, asn1_prefix.len); - - ssh_hash *h = ssh_hash_new(halg); - put_datapl(h, data); - ssh_hash_final(h, bytes + 2 + padding + asn1_prefix.len); - - return bytes; -} - -static bool rsa2_verify(ssh_key *key, ptrlen sig, ptrlen data) -{ - RSAKey *rsa = container_of(key, RSAKey, sshk); - BinarySource src[1]; - ptrlen type, in_pl; - mp_int *in, *out; - - const struct ssh2_rsa_extra *extra = - (const struct ssh2_rsa_extra *)key->vt->extra; - - const ssh_hashalg *halg = rsa2_hash_alg_for_flags(extra->signflags, NULL); - - /* Start by making sure the key is even long enough to encode a - * signature. If not, everything fails to verify. */ - size_t nbytes = (mp_get_nbits(rsa->modulus) + 7) / 8; - if (nbytes < rsa_pkcs1_length_of_fixed_parts(halg)) - return false; - - BinarySource_BARE_INIT_PL(src, sig); - type = get_string(src); - /* - * RFC 4253 section 6.6: the signature integer in an ssh-rsa - * signature is 'without lengths or padding'. That is, we _don't_ - * expect the usual leading zero byte if the topmost bit of the - * first byte is set. (However, because of the possibility of - * BUG_SSH2_RSA_PADDING at the other end, we tolerate it if it's - * there.) So we can't use get_mp_ssh2, which enforces that - * leading-byte scheme; instead we use get_string and - * mp_from_bytes_be, which will tolerate anything. - */ - in_pl = get_string(src); - if (get_err(src) || !ptrlen_eq_string(type, key->vt->ssh_id)) - return false; - - in = mp_from_bytes_be(in_pl); - out = mp_modpow(in, rsa->exponent, rsa->modulus); - mp_free(in); - - unsigned diff = 0; - - unsigned char *bytes = rsa_pkcs1_signature_string(nbytes, halg, data); - for (size_t i = 0; i < nbytes; i++) - diff |= bytes[nbytes-1 - i] ^ mp_get_byte(out, i); - smemclr(bytes, nbytes); - sfree(bytes); - mp_free(out); - - return diff == 0; -} - -static void rsa2_sign(ssh_key *key, ptrlen data, - unsigned flags, BinarySink *bs) -{ - RSAKey *rsa = container_of(key, RSAKey, sshk); - unsigned char *bytes; - size_t nbytes; - mp_int *in, *out; - const ssh_hashalg *halg; - const char *sign_alg_name; - - const struct ssh2_rsa_extra *extra = - (const struct ssh2_rsa_extra *)key->vt->extra; - flags |= extra->signflags; - - halg = rsa2_hash_alg_for_flags(flags, &sign_alg_name); - - nbytes = (mp_get_nbits(rsa->modulus) + 7) / 8; - - bytes = rsa_pkcs1_signature_string(nbytes, halg, data); - in = mp_from_bytes_be(make_ptrlen(bytes, nbytes)); - smemclr(bytes, nbytes); - sfree(bytes); - - out = rsa_privkey_op(in, rsa); - mp_free(in); - - put_stringz(bs, sign_alg_name); - nbytes = (mp_get_nbits(out) + 7) / 8; - put_uint32(bs, nbytes); - for (size_t i = 0; i < nbytes; i++) - put_byte(bs, mp_get_byte(out, nbytes - 1 - i)); - - mp_free(out); -} - -static char *rsa2_invalid(ssh_key *key, unsigned flags) -{ - RSAKey *rsa = container_of(key, RSAKey, sshk); - size_t bits = mp_get_nbits(rsa->modulus), nbytes = (bits + 7) / 8; - const char *sign_alg_name; - const ssh_hashalg *halg = rsa2_hash_alg_for_flags(flags, &sign_alg_name); - if (nbytes < rsa_pkcs1_length_of_fixed_parts(halg)) { - return dupprintf( - "%"SIZEu"-bit RSA key is too short to generate %s signatures", - bits, sign_alg_name); - } - - return NULL; -} - -static const struct ssh2_rsa_extra - rsa_extra = { 0 }, - rsa_sha256_extra = { SSH_AGENT_RSA_SHA2_256 }, - rsa_sha512_extra = { SSH_AGENT_RSA_SHA2_512 }; - -#define COMMON_KEYALG_FIELDS \ - .new_pub = rsa2_new_pub, \ - .new_priv = rsa2_new_priv, \ - .new_priv_openssh = rsa2_new_priv_openssh, \ - .freekey = rsa2_freekey, \ - .invalid = rsa2_invalid, \ - .sign = rsa2_sign, \ - .verify = rsa2_verify, \ - .public_blob = rsa2_public_blob, \ - .private_blob = rsa2_private_blob, \ - .openssh_blob = rsa2_openssh_blob, \ - .cache_str = rsa2_cache_str, \ - .components = rsa2_components, \ - .pubkey_bits = rsa2_pubkey_bits, \ - .cache_id = "rsa2" - -const ssh_keyalg ssh_rsa = { - COMMON_KEYALG_FIELDS, - .ssh_id = "ssh-rsa", - .supported_flags = SSH_AGENT_RSA_SHA2_256 | SSH_AGENT_RSA_SHA2_512, - .extra = &rsa_extra, -}; - -const ssh_keyalg ssh_rsa_sha256 = { - COMMON_KEYALG_FIELDS, - .ssh_id = "rsa-sha2-256", - .supported_flags = 0, - .extra = &rsa_sha256_extra, -}; - -const ssh_keyalg ssh_rsa_sha512 = { - COMMON_KEYALG_FIELDS, - .ssh_id = "rsa-sha2-512", - .supported_flags = 0, - .extra = &rsa_sha512_extra, -}; - -RSAKey *ssh_rsakex_newkey(ptrlen data) -{ - ssh_key *sshk = rsa2_new_pub(&ssh_rsa, data); - if (!sshk) - return NULL; - return container_of(sshk, RSAKey, sshk); -} - -void ssh_rsakex_freekey(RSAKey *key) -{ - rsa2_freekey(&key->sshk); -} - -int ssh_rsakex_klen(RSAKey *rsa) -{ - return mp_get_nbits(rsa->modulus); -} - -static void oaep_mask(const ssh_hashalg *h, void *seed, int seedlen, - void *vdata, int datalen) -{ - unsigned char *data = (unsigned char *)vdata; - unsigned count = 0; - - ssh_hash *s = ssh_hash_new(h); - - while (datalen > 0) { - int i, max = (datalen > h->hlen ? h->hlen : datalen); - unsigned char hash[MAX_HASH_LEN]; - - ssh_hash_reset(s); - assert(h->hlen <= MAX_HASH_LEN); - put_data(s, seed, seedlen); - put_uint32(s, count); - ssh_hash_digest(s, hash); - count++; - - for (i = 0; i < max; i++) - data[i] ^= hash[i]; - - data += max; - datalen -= max; - } - - ssh_hash_free(s); -} - -strbuf *ssh_rsakex_encrypt(RSAKey *rsa, const ssh_hashalg *h, ptrlen in) -{ - mp_int *b1, *b2; - 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 + mp_get_nbits(rsa->modulus)) / 8; - - /* The length of the input data must be at most k - 2hLen - 2. */ - assert(in.len > 0 && in.len <= k - 2*HLEN - 2); - - /* The length of the output data wants to be precisely k. */ - strbuf *toret = strbuf_new_nm(); - int outlen = k; - unsigned char *out = strbuf_append(toret, outlen); - - /* - * 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. */ - random_read(out + 1, HLEN); - /* At position 1+HLEN, the data block DB, consisting of: */ - /* The hash of the label (we only support an empty label here) */ - hash_simple(h, PTRLEN_LITERAL(""), 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 - in.len - 1] = 1; - memcpy(out + outlen - in.len, in.ptr, in.len); - - /* - * 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 = mp_from_bytes_be(make_ptrlen(out, outlen)); - b2 = mp_modpow(b1, rsa->exponent, rsa->modulus); - p = (char *)out; - for (i = outlen; i--;) { - *p++ = mp_get_byte(b2, i); - } - mp_free(b1); - mp_free(b2); - - /* - * And we're done. - */ - return toret; -} - -mp_int *ssh_rsakex_decrypt( - RSAKey *rsa, const ssh_hashalg *h, ptrlen ciphertext) -{ - mp_int *b1, *b2; - int outlen, i; - unsigned char *out; - unsigned char labelhash[64]; - BinarySource src[1]; - const int HLEN = h->hlen; - - /* - * Decryption side of the RSA key exchange operation. - */ - - /* The length of the encrypted data should be exactly the length - * in octets of the RSA modulus.. */ - outlen = (7 + mp_get_nbits(rsa->modulus)) / 8; - if (ciphertext.len != outlen) - return NULL; - - /* Do the RSA decryption, and extract the result into a byte array. */ - b1 = mp_from_bytes_be(ciphertext); - b2 = rsa_privkey_op(b1, rsa); - out = snewn(outlen, unsigned char); - for (i = 0; i < outlen; i++) - out[i] = mp_get_byte(b2, outlen-1-i); - mp_free(b1); - mp_free(b2); - - /* Do the OAEP masking operations, in the reverse order from encryption */ - oaep_mask(h, out+HLEN+1, outlen-HLEN-1, out+1, HLEN); - oaep_mask(h, out+1, HLEN, out+HLEN+1, outlen-HLEN-1); - - /* Check the leading byte is zero. */ - if (out[0] != 0) { - sfree(out); - return NULL; - } - /* Check the label hash at position 1+HLEN */ - assert(HLEN <= lenof(labelhash)); - hash_simple(h, PTRLEN_LITERAL(""), labelhash); - if (memcmp(out + HLEN + 1, labelhash, HLEN)) { - sfree(out); - return NULL; - } - /* Expect zero bytes followed by a 1 byte */ - for (i = 1 + 2 * HLEN; i < outlen; i++) { - if (out[i] == 1) { - i++; /* skip over the 1 byte */ - break; - } else if (out[i] != 0) { - sfree(out); - return NULL; - } - } - /* And what's left is the input message data, which should be - * encoded as an ordinary SSH-2 mpint. */ - BinarySource_BARE_INIT(src, out + i, outlen - i); - b1 = get_mp_ssh2(src); - sfree(out); - if (get_err(src) || get_avail(src) != 0) { - mp_free(b1); - return NULL; - } - - /* Success! */ - return b1; -} - -static const struct ssh_rsa_kex_extra ssh_rsa_kex_extra_sha1 = { 1024 }; -static const struct ssh_rsa_kex_extra ssh_rsa_kex_extra_sha256 = { 2048 }; - -static const ssh_kex ssh_rsa_kex_sha1 = { - "rsa1024-sha1", NULL, KEXTYPE_RSA, - &ssh_sha1, &ssh_rsa_kex_extra_sha1, -}; - -static const ssh_kex ssh_rsa_kex_sha256 = { - "rsa2048-sha256", NULL, KEXTYPE_RSA, - &ssh_sha256, &ssh_rsa_kex_extra_sha256, -}; - -static const ssh_kex *const rsa_kex_list[] = { - &ssh_rsa_kex_sha256, - &ssh_rsa_kex_sha1 -}; - -const ssh_kexes ssh_rsa_kex = { lenof(rsa_kex_list), rsa_kex_list }; |