diff options
Diffstat (limited to 'crypto/openssh/jpake.c')
| -rw-r--r-- | crypto/openssh/jpake.c | 449 |
1 files changed, 449 insertions, 0 deletions
diff --git a/crypto/openssh/jpake.c b/crypto/openssh/jpake.c new file mode 100644 index 0000000..1306610 --- /dev/null +++ b/crypto/openssh/jpake.c @@ -0,0 +1,449 @@ +/* $OpenBSD: jpake.c,v 1.2 2009/03/05 07:18:19 djm Exp $ */ +/* + * Copyright (c) 2008 Damien Miller. All rights reserved. + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +/* + * Shared components of zero-knowledge password auth using J-PAKE protocol + * as described in: + * + * F. Hao, P. Ryan, "Password Authenticated Key Exchange by Juggling", + * 16th Workshop on Security Protocols, Cambridge, April 2008 + * + * http://grouper.ieee.org/groups/1363/Research/contributions/hao-ryan-2008.pdf + */ + +#include "includes.h" + +#include <sys/types.h> + +#include <stdio.h> +#include <string.h> +#include <stdarg.h> + +#include <openssl/bn.h> +#include <openssl/evp.h> + +#include "xmalloc.h" +#include "ssh2.h" +#include "key.h" +#include "hostfile.h" +#include "auth.h" +#include "buffer.h" +#include "packet.h" +#include "dispatch.h" +#include "log.h" + +#include "jpake.h" +#include "schnorr.h" + +#ifdef JPAKE + +/* RFC3526 group 5, 1536 bits */ +#define JPAKE_GROUP_G "2" +#define JPAKE_GROUP_P \ + "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74" \ + "020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F1437" \ + "4FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" \ + "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3DC2007CB8A163BF05" \ + "98DA48361C55D39A69163FA8FD24CF5F83655D23DCA3AD961C62F356208552BB" \ + "9ED529077096966D670C354E4ABC9804F1746C08CA237327FFFFFFFFFFFFFFFF" + +struct modp_group * +jpake_default_group(void) +{ + return modp_group_from_g_and_safe_p(JPAKE_GROUP_G, JPAKE_GROUP_P); +} + +struct jpake_ctx * +jpake_new(void) +{ + struct jpake_ctx *ret; + + ret = xcalloc(1, sizeof(*ret)); + + ret->grp = jpake_default_group(); + + ret->s = ret->k = NULL; + ret->x1 = ret->x2 = ret->x3 = ret->x4 = NULL; + ret->g_x1 = ret->g_x2 = ret->g_x3 = ret->g_x4 = NULL; + ret->a = ret->b = NULL; + + ret->client_id = ret->server_id = NULL; + ret->h_k_cid_sessid = ret->h_k_sid_sessid = NULL; + + debug3("%s: alloc %p", __func__, ret); + + return ret; +} + +void +jpake_free(struct jpake_ctx *pctx) +{ + debug3("%s: free %p", __func__, pctx); + +#define JPAKE_BN_CLEAR_FREE(v) \ + do { \ + if ((v) != NULL) { \ + BN_clear_free(v); \ + (v) = NULL; \ + } \ + } while (0) +#define JPAKE_BUF_CLEAR_FREE(v, l) \ + do { \ + if ((v) != NULL) { \ + bzero((v), (l)); \ + xfree(v); \ + (v) = NULL; \ + (l) = 0; \ + } \ + } while (0) + + JPAKE_BN_CLEAR_FREE(pctx->s); + JPAKE_BN_CLEAR_FREE(pctx->k); + JPAKE_BN_CLEAR_FREE(pctx->x1); + JPAKE_BN_CLEAR_FREE(pctx->x2); + JPAKE_BN_CLEAR_FREE(pctx->x3); + JPAKE_BN_CLEAR_FREE(pctx->x4); + JPAKE_BN_CLEAR_FREE(pctx->g_x1); + JPAKE_BN_CLEAR_FREE(pctx->g_x2); + JPAKE_BN_CLEAR_FREE(pctx->g_x3); + JPAKE_BN_CLEAR_FREE(pctx->g_x4); + JPAKE_BN_CLEAR_FREE(pctx->a); + JPAKE_BN_CLEAR_FREE(pctx->b); + + JPAKE_BUF_CLEAR_FREE(pctx->client_id, pctx->client_id_len); + JPAKE_BUF_CLEAR_FREE(pctx->server_id, pctx->server_id_len); + JPAKE_BUF_CLEAR_FREE(pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len); + JPAKE_BUF_CLEAR_FREE(pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len); + +#undef JPAKE_BN_CLEAR_FREE +#undef JPAKE_BUF_CLEAR_FREE + + bzero(pctx, sizeof(pctx)); + xfree(pctx); +} + +/* dump entire jpake_ctx. NB. includes private values! */ +void +jpake_dump(struct jpake_ctx *pctx, const char *fmt, ...) +{ + char *out; + va_list args; + + out = NULL; + va_start(args, fmt); + vasprintf(&out, fmt, args); + va_end(args); + if (out == NULL) + fatal("%s: vasprintf failed", __func__); + + debug3("%s: %s (ctx at %p)", __func__, out, pctx); + if (pctx == NULL) { + free(out); + return; + } + +#define JPAKE_DUMP_BN(a) do { \ + if ((a) != NULL) \ + JPAKE_DEBUG_BN(((a), "%s = ", #a)); \ + } while (0) +#define JPAKE_DUMP_BUF(a, b) do { \ + if ((a) != NULL) \ + JPAKE_DEBUG_BUF((a, b, "%s", #a)); \ + } while (0) + + JPAKE_DUMP_BN(pctx->s); + JPAKE_DUMP_BN(pctx->k); + JPAKE_DUMP_BN(pctx->x1); + JPAKE_DUMP_BN(pctx->x2); + JPAKE_DUMP_BN(pctx->x3); + JPAKE_DUMP_BN(pctx->x4); + JPAKE_DUMP_BN(pctx->g_x1); + JPAKE_DUMP_BN(pctx->g_x2); + JPAKE_DUMP_BN(pctx->g_x3); + JPAKE_DUMP_BN(pctx->g_x4); + JPAKE_DUMP_BN(pctx->a); + JPAKE_DUMP_BN(pctx->b); + + JPAKE_DUMP_BUF(pctx->client_id, pctx->client_id_len); + JPAKE_DUMP_BUF(pctx->server_id, pctx->server_id_len); + JPAKE_DUMP_BUF(pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len); + JPAKE_DUMP_BUF(pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len); + + debug3("%s: %s done", __func__, out); + free(out); +} + +/* Shared parts of step 1 exchange calculation */ +void +jpake_step1(struct modp_group *grp, + u_char **id, u_int *id_len, + BIGNUM **priv1, BIGNUM **priv2, BIGNUM **g_priv1, BIGNUM **g_priv2, + u_char **priv1_proof, u_int *priv1_proof_len, + u_char **priv2_proof, u_int *priv2_proof_len) +{ + BN_CTX *bn_ctx; + + if ((bn_ctx = BN_CTX_new()) == NULL) + fatal("%s: BN_CTX_new", __func__); + + /* Random nonce to prevent replay */ + *id = xmalloc(KZP_ID_LEN); + *id_len = KZP_ID_LEN; + arc4random_buf(*id, *id_len); + + /* + * x1/x3 is a random element of Zq + * x2/x4 is a random element of Z*q + * We also exclude [1] from x1/x3 candidates and [0, 1] from + * x2/x4 candiates to avoid possible degeneracy (i.e. g^0, g^1). + */ + if ((*priv1 = bn_rand_range_gt_one(grp->q)) == NULL || + (*priv2 = bn_rand_range_gt_one(grp->q)) == NULL) + fatal("%s: bn_rand_range_gt_one", __func__); + + /* + * client: g_x1 = g^x1 mod p / server: g_x3 = g^x3 mod p + * client: g_x2 = g^x2 mod p / server: g_x4 = g^x4 mod p + */ + if ((*g_priv1 = BN_new()) == NULL || + (*g_priv2 = BN_new()) == NULL) + fatal("%s: BN_new", __func__); + if (BN_mod_exp(*g_priv1, grp->g, *priv1, grp->p, bn_ctx) == -1) + fatal("%s: BN_mod_exp", __func__); + if (BN_mod_exp(*g_priv2, grp->g, *priv2, grp->p, bn_ctx) == -1) + fatal("%s: BN_mod_exp", __func__); + + /* Generate proofs for holding x1/x3 and x2/x4 */ + if (schnorr_sign_buf(grp->p, grp->q, grp->g, + *priv1, *g_priv1, *id, *id_len, + priv1_proof, priv1_proof_len) != 0) + fatal("%s: schnorr_sign", __func__); + if (schnorr_sign_buf(grp->p, grp->q, grp->g, + *priv2, *g_priv2, *id, *id_len, + priv2_proof, priv2_proof_len) != 0) + fatal("%s: schnorr_sign", __func__); + + BN_CTX_free(bn_ctx); +} + +/* Shared parts of step 2 exchange calculation */ +void +jpake_step2(struct modp_group *grp, BIGNUM *s, + BIGNUM *mypub1, BIGNUM *theirpub1, BIGNUM *theirpub2, BIGNUM *mypriv2, + const u_char *theirid, u_int theirid_len, + const u_char *myid, u_int myid_len, + const u_char *theirpub1_proof, u_int theirpub1_proof_len, + const u_char *theirpub2_proof, u_int theirpub2_proof_len, + BIGNUM **newpub, + u_char **newpub_exponent_proof, u_int *newpub_exponent_proof_len) +{ + BN_CTX *bn_ctx; + BIGNUM *tmp, *exponent; + + /* Validate peer's step 1 values */ + if (BN_cmp(theirpub1, BN_value_one()) <= 0) + fatal("%s: theirpub1 <= 1", __func__); + if (BN_cmp(theirpub2, BN_value_one()) <= 0) + fatal("%s: theirpub2 <= 1", __func__); + + if (schnorr_verify_buf(grp->p, grp->q, grp->g, theirpub1, + theirid, theirid_len, theirpub1_proof, theirpub1_proof_len) != 1) + fatal("%s: schnorr_verify theirpub1 failed", __func__); + if (schnorr_verify_buf(grp->p, grp->q, grp->g, theirpub2, + theirid, theirid_len, theirpub2_proof, theirpub2_proof_len) != 1) + fatal("%s: schnorr_verify theirpub2 failed", __func__); + + if ((bn_ctx = BN_CTX_new()) == NULL) + fatal("%s: BN_CTX_new", __func__); + + if ((*newpub = BN_new()) == NULL || + (tmp = BN_new()) == NULL || + (exponent = BN_new()) == NULL) + fatal("%s: BN_new", __func__); + + /* + * client: exponent = x2 * s mod p + * server: exponent = x4 * s mod p + */ + if (BN_mod_mul(exponent, mypriv2, s, grp->q, bn_ctx) != 1) + fatal("%s: BN_mod_mul (exponent = mypriv2 * s mod p)", + __func__); + + /* + * client: tmp = g^(x1 + x3 + x4) mod p + * server: tmp = g^(x1 + x2 + x3) mod p + */ + if (BN_mod_mul(tmp, mypub1, theirpub1, grp->p, bn_ctx) != 1) + fatal("%s: BN_mod_mul (tmp = mypub1 * theirpub1 mod p)", + __func__); + if (BN_mod_mul(tmp, tmp, theirpub2, grp->p, bn_ctx) != 1) + fatal("%s: BN_mod_mul (tmp = tmp * theirpub2 mod p)", __func__); + + /* + * client: a = tmp^exponent = g^((x1+x3+x4) * x2 * s) mod p + * server: b = tmp^exponent = g^((x1+x2+x3) * x4 * s) mod p + */ + if (BN_mod_exp(*newpub, tmp, exponent, grp->p, bn_ctx) != 1) + fatal("%s: BN_mod_mul (newpub = tmp^exponent mod p)", __func__); + + JPAKE_DEBUG_BN((tmp, "%s: tmp = ", __func__)); + JPAKE_DEBUG_BN((exponent, "%s: exponent = ", __func__)); + + /* Note the generator here is 'tmp', not g */ + if (schnorr_sign_buf(grp->p, grp->q, tmp, exponent, *newpub, + myid, myid_len, + newpub_exponent_proof, newpub_exponent_proof_len) != 0) + fatal("%s: schnorr_sign newpub", __func__); + + BN_clear_free(tmp); /* XXX stash for later use? */ + BN_clear_free(exponent); /* XXX stash for later use? (yes, in conf) */ + + BN_CTX_free(bn_ctx); +} + +/* Confirmation hash calculation */ +void +jpake_confirm_hash(const BIGNUM *k, + const u_char *endpoint_id, u_int endpoint_id_len, + const u_char *sess_id, u_int sess_id_len, + u_char **confirm_hash, u_int *confirm_hash_len) +{ + Buffer b; + + /* + * Calculate confirmation proof: + * client: H(k || client_id || session_id) + * server: H(k || server_id || session_id) + */ + buffer_init(&b); + buffer_put_bignum2(&b, k); + buffer_put_string(&b, endpoint_id, endpoint_id_len); + buffer_put_string(&b, sess_id, sess_id_len); + if (hash_buffer(buffer_ptr(&b), buffer_len(&b), EVP_sha256(), + confirm_hash, confirm_hash_len) != 0) + fatal("%s: hash_buffer", __func__); + buffer_free(&b); +} + +/* Shared parts of key derivation and confirmation calculation */ +void +jpake_key_confirm(struct modp_group *grp, BIGNUM *s, BIGNUM *step2_val, + BIGNUM *mypriv2, BIGNUM *mypub1, BIGNUM *mypub2, + BIGNUM *theirpub1, BIGNUM *theirpub2, + const u_char *my_id, u_int my_id_len, + const u_char *their_id, u_int their_id_len, + const u_char *sess_id, u_int sess_id_len, + const u_char *theirpriv2_s_proof, u_int theirpriv2_s_proof_len, + BIGNUM **k, + u_char **confirm_hash, u_int *confirm_hash_len) +{ + BN_CTX *bn_ctx; + BIGNUM *tmp; + + if ((bn_ctx = BN_CTX_new()) == NULL) + fatal("%s: BN_CTX_new", __func__); + if ((tmp = BN_new()) == NULL || + (*k = BN_new()) == NULL) + fatal("%s: BN_new", __func__); + + /* Validate step 2 values */ + if (BN_cmp(step2_val, BN_value_one()) <= 0) + fatal("%s: step2_val <= 1", __func__); + + /* + * theirpriv2_s_proof is calculated with a different generator: + * tmp = g^(mypriv1+mypriv2+theirpub1) = g^mypub1*g^mypub2*g^theirpub1 + * Calculate it here so we can check the signature. + */ + if (BN_mod_mul(tmp, mypub1, mypub2, grp->p, bn_ctx) != 1) + fatal("%s: BN_mod_mul (tmp = mypub1 * mypub2 mod p)", __func__); + if (BN_mod_mul(tmp, tmp, theirpub1, grp->p, bn_ctx) != 1) + fatal("%s: BN_mod_mul (tmp = tmp * theirpub1 mod p)", __func__); + + JPAKE_DEBUG_BN((tmp, "%s: tmp = ", __func__)); + + if (schnorr_verify_buf(grp->p, grp->q, tmp, step2_val, + their_id, their_id_len, + theirpriv2_s_proof, theirpriv2_s_proof_len) != 1) + fatal("%s: schnorr_verify theirpriv2_s_proof failed", __func__); + + /* + * Derive shared key: + * client: k = (b / g^(x2*x4*s))^x2 = g^((x1+x3)*x2*x4*s) + * server: k = (a / g^(x2*x4*s))^x4 = g^((x1+x3)*x2*x4*s) + * + * Computed as: + * client: k = (g_x4^(q - (x2 * s)) * b)^x2 mod p + * server: k = (g_x2^(q - (x4 * s)) * b)^x4 mod p + */ + if (BN_mul(tmp, mypriv2, s, bn_ctx) != 1) + fatal("%s: BN_mul (tmp = mypriv2 * s)", __func__); + if (BN_mod_sub(tmp, grp->q, tmp, grp->q, bn_ctx) != 1) + fatal("%s: BN_mod_sub (tmp = q - tmp mod q)", __func__); + if (BN_mod_exp(tmp, theirpub2, tmp, grp->p, bn_ctx) != 1) + fatal("%s: BN_mod_exp (tmp = theirpub2^tmp) mod p", __func__); + if (BN_mod_mul(tmp, tmp, step2_val, grp->p, bn_ctx) != 1) + fatal("%s: BN_mod_mul (tmp = tmp * step2_val) mod p", __func__); + if (BN_mod_exp(*k, tmp, mypriv2, grp->p, bn_ctx) != 1) + fatal("%s: BN_mod_exp (k = tmp^mypriv2) mod p", __func__); + + BN_CTX_free(bn_ctx); + BN_clear_free(tmp); + + jpake_confirm_hash(*k, my_id, my_id_len, sess_id, sess_id_len, + confirm_hash, confirm_hash_len); +} + +/* + * Calculate and check confirmation hash from peer. Returns 1 on success + * 0 on failure/mismatch. + */ +int +jpake_check_confirm(const BIGNUM *k, + const u_char *peer_id, u_int peer_id_len, + const u_char *sess_id, u_int sess_id_len, + const u_char *peer_confirm_hash, u_int peer_confirm_hash_len) +{ + u_char *expected_confirm_hash; + u_int expected_confirm_hash_len; + int success = 0; + + /* Calculate and verify expected confirmation hash */ + jpake_confirm_hash(k, peer_id, peer_id_len, sess_id, sess_id_len, + &expected_confirm_hash, &expected_confirm_hash_len); + + JPAKE_DEBUG_BUF((expected_confirm_hash, expected_confirm_hash_len, + "%s: expected confirm hash", __func__)); + JPAKE_DEBUG_BUF((peer_confirm_hash, peer_confirm_hash_len, + "%s: received confirm hash", __func__)); + + if (peer_confirm_hash_len != expected_confirm_hash_len) + error("%s: confirmation length mismatch (my %u them %u)", + __func__, expected_confirm_hash_len, peer_confirm_hash_len); + else if (memcmp(peer_confirm_hash, expected_confirm_hash, + expected_confirm_hash_len) == 0) + success = 1; + bzero(expected_confirm_hash, expected_confirm_hash_len); + xfree(expected_confirm_hash); + debug3("%s: success = %d", __func__, success); + return success; +} + +/* XXX main() function with tests */ + +#endif /* JPAKE */ + |
