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-rw-r--r--auth2-jpake.c563
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diff --git a/auth2-jpake.c b/auth2-jpake.c
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-/* $OpenBSD: auth2-jpake.c,v 1.6 2013/05/17 00:13:13 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.
- */
-
-/*
- * Server side 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
- */
-
-#ifdef JPAKE
-
-#include <sys/types.h>
-#include <sys/param.h>
-
-#include <pwd.h>
-#include <stdio.h>
-#include <string.h>
-#include <login_cap.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 "servconf.h"
-#include "auth-options.h"
-#include "canohost.h"
-#ifdef GSSAPI
-#include "ssh-gss.h"
-#endif
-#include "monitor_wrap.h"
-
-#include "schnorr.h"
-#include "jpake.h"
-
-/*
- * XXX options->permit_empty_passwd (at the moment, they will be refused
- * anyway because they will mismatch on fake salt.
- */
-
-/* Dispatch handlers */
-static void input_userauth_jpake_client_step1(int, u_int32_t, void *);
-static void input_userauth_jpake_client_step2(int, u_int32_t, void *);
-static void input_userauth_jpake_client_confirm(int, u_int32_t, void *);
-
-static int auth2_jpake_start(Authctxt *);
-
-/* import */
-extern ServerOptions options;
-extern u_char *session_id2;
-extern u_int session_id2_len;
-
-/*
- * Attempt J-PAKE authentication.
- */
-static int
-userauth_jpake(Authctxt *authctxt)
-{
- int authenticated = 0;
-
- packet_check_eom();
-
- debug("jpake-01@openssh.com requested");
-
- if (authctxt->user != NULL) {
- if (authctxt->jpake_ctx == NULL)
- authctxt->jpake_ctx = jpake_new();
- if (options.zero_knowledge_password_authentication)
- authenticated = auth2_jpake_start(authctxt);
- }
-
- return authenticated;
-}
-
-Authmethod method_jpake = {
- "jpake-01@openssh.com",
- userauth_jpake,
- &options.zero_knowledge_password_authentication
-};
-
-/* Clear context and callbacks */
-void
-auth2_jpake_stop(Authctxt *authctxt)
-{
- /* unregister callbacks */
- dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP1, NULL);
- dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP2, NULL);
- dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_CONFIRM, NULL);
- if (authctxt->jpake_ctx != NULL) {
- jpake_free(authctxt->jpake_ctx);
- authctxt->jpake_ctx = NULL;
- }
-}
-
-/* Returns 1 if 'c' is a valid crypt(3) salt character, 0 otherwise */
-static int
-valid_crypt_salt(int c)
-{
- if (c >= 'A' && c <= 'Z')
- return 1;
- if (c >= 'a' && c <= 'z')
- return 1;
- if (c >= '.' && c <= '9')
- return 1;
- return 0;
-}
-
-/*
- * Derive fake salt as H(username || first_private_host_key)
- * This provides relatively stable fake salts for non-existent
- * users and avoids the jpake method becoming an account validity
- * oracle.
- */
-static void
-derive_rawsalt(const char *username, u_char *rawsalt, u_int len)
-{
- u_char *digest;
- u_int digest_len;
- Buffer b;
- Key *k;
-
- buffer_init(&b);
- buffer_put_cstring(&b, username);
- if ((k = get_hostkey_by_index(0)) == NULL ||
- (k->flags & KEY_FLAG_EXT))
- fatal("%s: no hostkeys", __func__);
- switch (k->type) {
- case KEY_RSA1:
- case KEY_RSA:
- if (k->rsa->p == NULL || k->rsa->q == NULL)
- fatal("%s: RSA key missing p and/or q", __func__);
- buffer_put_bignum2(&b, k->rsa->p);
- buffer_put_bignum2(&b, k->rsa->q);
- break;
- case KEY_DSA:
- if (k->dsa->priv_key == NULL)
- fatal("%s: DSA key missing priv_key", __func__);
- buffer_put_bignum2(&b, k->dsa->priv_key);
- break;
- case KEY_ECDSA:
- if (EC_KEY_get0_private_key(k->ecdsa) == NULL)
- fatal("%s: ECDSA key missing priv_key", __func__);
- buffer_put_bignum2(&b, EC_KEY_get0_private_key(k->ecdsa));
- break;
- default:
- fatal("%s: unknown key type %d", __func__, k->type);
- }
- if (hash_buffer(buffer_ptr(&b), buffer_len(&b), EVP_sha256(),
- &digest, &digest_len) != 0)
- fatal("%s: hash_buffer", __func__);
- buffer_free(&b);
- if (len > digest_len)
- fatal("%s: not enough bytes for rawsalt (want %u have %u)",
- __func__, len, digest_len);
- memcpy(rawsalt, digest, len);
- bzero(digest, digest_len);
- free(digest);
-}
-
-/* ASCII an integer [0, 64) for inclusion in a password/salt */
-static char
-pw_encode64(u_int i64)
-{
- const u_char e64[] =
- "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
- return e64[i64 % 64];
-}
-
-/* Generate ASCII salt bytes for user */
-static char *
-makesalt(u_int want, const char *user)
-{
- u_char rawsalt[32];
- static char ret[33];
- u_int i;
-
- if (want > sizeof(ret) - 1)
- fatal("%s: want %u", __func__, want);
-
- derive_rawsalt(user, rawsalt, sizeof(rawsalt));
- bzero(ret, sizeof(ret));
- for (i = 0; i < want; i++)
- ret[i] = pw_encode64(rawsalt[i]);
- bzero(rawsalt, sizeof(rawsalt));
-
- return ret;
-}
-
-/*
- * Select the system's default password hashing scheme and generate
- * a stable fake salt under it for use by a non-existent account.
- * Prevents jpake method being used to infer the validity of accounts.
- */
-static void
-fake_salt_and_scheme(Authctxt *authctxt, char **salt, char **scheme)
-{
- char *rounds_s, *style;
- long long rounds;
- login_cap_t *lc;
-
-
- if ((lc = login_getclass(authctxt->pw->pw_class)) == NULL &&
- (lc = login_getclass(NULL)) == NULL)
- fatal("%s: login_getclass failed", __func__);
- style = login_getcapstr(lc, "localcipher", NULL, NULL);
- if (style == NULL)
- style = xstrdup("blowfish,6");
- login_close(lc);
-
- if ((rounds_s = strchr(style, ',')) != NULL)
- *rounds_s++ = '\0';
- rounds = strtonum(rounds_s, 1, 1<<31, NULL);
-
- if (strcmp(style, "md5") == 0) {
- xasprintf(salt, "$1$%s$", makesalt(8, authctxt->user));
- *scheme = xstrdup("md5");
- } else if (strcmp(style, "old") == 0) {
- *salt = xstrdup(makesalt(2, authctxt->user));
- *scheme = xstrdup("crypt");
- } else if (strcmp(style, "newsalt") == 0) {
- rounds = MAX(rounds, 7250);
- rounds = MIN(rounds, (1<<24) - 1);
- xasprintf(salt, "_%c%c%c%c%s",
- pw_encode64(rounds), pw_encode64(rounds >> 6),
- pw_encode64(rounds >> 12), pw_encode64(rounds >> 18),
- makesalt(4, authctxt->user));
- *scheme = xstrdup("crypt-extended");
- } else {
- /* Default to blowfish */
- rounds = MAX(rounds, 3);
- rounds = MIN(rounds, 31);
- xasprintf(salt, "$2a$%02lld$%s", rounds,
- makesalt(22, authctxt->user));
- *scheme = xstrdup("bcrypt");
- }
- free(style);
- debug3("%s: fake %s salt for user %s: %s",
- __func__, *scheme, authctxt->user, *salt);
-}
-
-/*
- * Fetch password hashing scheme, password salt and derive shared secret
- * for user. If user does not exist, a fake but stable and user-unique
- * salt will be returned.
- */
-void
-auth2_jpake_get_pwdata(Authctxt *authctxt, BIGNUM **s,
- char **hash_scheme, char **salt)
-{
- char *cp;
- u_char *secret;
- u_int secret_len, salt_len;
-
-#ifdef JPAKE_DEBUG
- debug3("%s: valid %d pw %.5s...", __func__,
- authctxt->valid, authctxt->pw->pw_passwd);
-#endif
-
- *salt = NULL;
- *hash_scheme = NULL;
- if (authctxt->valid) {
- if (strncmp(authctxt->pw->pw_passwd, "$2$", 3) == 0 &&
- strlen(authctxt->pw->pw_passwd) > 28) {
- /*
- * old-variant bcrypt:
- * "$2$", 2 digit rounds, "$", 22 bytes salt
- */
- salt_len = 3 + 2 + 1 + 22 + 1;
- *salt = xmalloc(salt_len);
- strlcpy(*salt, authctxt->pw->pw_passwd, salt_len);
- *hash_scheme = xstrdup("bcrypt");
- } else if (strncmp(authctxt->pw->pw_passwd, "$2a$", 4) == 0 &&
- strlen(authctxt->pw->pw_passwd) > 29) {
- /*
- * current-variant bcrypt:
- * "$2a$", 2 digit rounds, "$", 22 bytes salt
- */
- salt_len = 4 + 2 + 1 + 22 + 1;
- *salt = xmalloc(salt_len);
- strlcpy(*salt, authctxt->pw->pw_passwd, salt_len);
- *hash_scheme = xstrdup("bcrypt");
- } else if (strncmp(authctxt->pw->pw_passwd, "$1$", 3) == 0 &&
- strlen(authctxt->pw->pw_passwd) > 5) {
- /*
- * md5crypt:
- * "$1$", salt until "$"
- */
- cp = strchr(authctxt->pw->pw_passwd + 3, '$');
- if (cp != NULL) {
- salt_len = (cp - authctxt->pw->pw_passwd) + 1;
- *salt = xmalloc(salt_len);
- strlcpy(*salt, authctxt->pw->pw_passwd,
- salt_len);
- *hash_scheme = xstrdup("md5crypt");
- }
- } else if (strncmp(authctxt->pw->pw_passwd, "_", 1) == 0 &&
- strlen(authctxt->pw->pw_passwd) > 9) {
- /*
- * BSDI extended crypt:
- * "_", 4 digits count, 4 chars salt
- */
- salt_len = 1 + 4 + 4 + 1;
- *salt = xmalloc(salt_len);
- strlcpy(*salt, authctxt->pw->pw_passwd, salt_len);
- *hash_scheme = xstrdup("crypt-extended");
- } else if (strlen(authctxt->pw->pw_passwd) == 13 &&
- valid_crypt_salt(authctxt->pw->pw_passwd[0]) &&
- valid_crypt_salt(authctxt->pw->pw_passwd[1])) {
- /*
- * traditional crypt:
- * 2 chars salt
- */
- salt_len = 2 + 1;
- *salt = xmalloc(salt_len);
- strlcpy(*salt, authctxt->pw->pw_passwd, salt_len);
- *hash_scheme = xstrdup("crypt");
- }
- if (*salt == NULL) {
- debug("%s: unrecognised crypt scheme for user %s",
- __func__, authctxt->pw->pw_name);
- }
- }
- if (*salt == NULL)
- fake_salt_and_scheme(authctxt, salt, hash_scheme);
-
- if (hash_buffer(authctxt->pw->pw_passwd,
- strlen(authctxt->pw->pw_passwd), EVP_sha256(),
- &secret, &secret_len) != 0)
- fatal("%s: hash_buffer", __func__);
- if ((*s = BN_bin2bn(secret, secret_len, NULL)) == NULL)
- fatal("%s: BN_bin2bn (secret)", __func__);
-#ifdef JPAKE_DEBUG
- debug3("%s: salt = %s (len %u)", __func__,
- *salt, (u_int)strlen(*salt));
- debug3("%s: scheme = %s", __func__, *hash_scheme);
- JPAKE_DEBUG_BN((*s, "%s: s = ", __func__));
-#endif
- bzero(secret, secret_len);
- free(secret);
-}
-
-/*
- * Begin authentication attempt.
- * Note, sets authctxt->postponed while in subprotocol
- */
-static int
-auth2_jpake_start(Authctxt *authctxt)
-{
- struct jpake_ctx *pctx = authctxt->jpake_ctx;
- u_char *x3_proof, *x4_proof;
- u_int x3_proof_len, x4_proof_len;
- char *salt, *hash_scheme;
-
- debug("%s: start", __func__);
-
- PRIVSEP(jpake_step1(pctx->grp,
- &pctx->server_id, &pctx->server_id_len,
- &pctx->x3, &pctx->x4, &pctx->g_x3, &pctx->g_x4,
- &x3_proof, &x3_proof_len,
- &x4_proof, &x4_proof_len));
-
- PRIVSEP(auth2_jpake_get_pwdata(authctxt, &pctx->s,
- &hash_scheme, &salt));
-
- if (!use_privsep)
- JPAKE_DEBUG_CTX((pctx, "step 1 sending in %s", __func__));
-
- packet_start(SSH2_MSG_USERAUTH_JPAKE_SERVER_STEP1);
- packet_put_cstring(hash_scheme);
- packet_put_cstring(salt);
- packet_put_string(pctx->server_id, pctx->server_id_len);
- packet_put_bignum2(pctx->g_x3);
- packet_put_bignum2(pctx->g_x4);
- packet_put_string(x3_proof, x3_proof_len);
- packet_put_string(x4_proof, x4_proof_len);
- packet_send();
- packet_write_wait();
-
- bzero(hash_scheme, strlen(hash_scheme));
- bzero(salt, strlen(salt));
- free(hash_scheme);
- free(salt);
- bzero(x3_proof, x3_proof_len);
- bzero(x4_proof, x4_proof_len);
- free(x3_proof);
- free(x4_proof);
-
- /* Expect step 1 packet from peer */
- dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP1,
- input_userauth_jpake_client_step1);
-
- authctxt->postponed = 1;
- return 0;
-}
-
-/* ARGSUSED */
-static void
-input_userauth_jpake_client_step1(int type, u_int32_t seq, void *ctxt)
-{
- Authctxt *authctxt = ctxt;
- struct jpake_ctx *pctx = authctxt->jpake_ctx;
- u_char *x1_proof, *x2_proof, *x4_s_proof;
- u_int x1_proof_len, x2_proof_len, x4_s_proof_len;
-
- /* Disable this message */
- dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP1, NULL);
-
- /* Fetch step 1 values */
- if ((pctx->g_x1 = BN_new()) == NULL ||
- (pctx->g_x2 = BN_new()) == NULL)
- fatal("%s: BN_new", __func__);
- pctx->client_id = packet_get_string(&pctx->client_id_len);
- packet_get_bignum2(pctx->g_x1);
- packet_get_bignum2(pctx->g_x2);
- x1_proof = packet_get_string(&x1_proof_len);
- x2_proof = packet_get_string(&x2_proof_len);
- packet_check_eom();
-
- if (!use_privsep)
- JPAKE_DEBUG_CTX((pctx, "step 1 received in %s", __func__));
-
- PRIVSEP(jpake_step2(pctx->grp, pctx->s, pctx->g_x3,
- pctx->g_x1, pctx->g_x2, pctx->x4,
- pctx->client_id, pctx->client_id_len,
- pctx->server_id, pctx->server_id_len,
- x1_proof, x1_proof_len,
- x2_proof, x2_proof_len,
- &pctx->b,
- &x4_s_proof, &x4_s_proof_len));
-
- bzero(x1_proof, x1_proof_len);
- bzero(x2_proof, x2_proof_len);
- free(x1_proof);
- free(x2_proof);
-
- if (!use_privsep)
- JPAKE_DEBUG_CTX((pctx, "step 2 sending in %s", __func__));
-
- /* Send values for step 2 */
- packet_start(SSH2_MSG_USERAUTH_JPAKE_SERVER_STEP2);
- packet_put_bignum2(pctx->b);
- packet_put_string(x4_s_proof, x4_s_proof_len);
- packet_send();
- packet_write_wait();
-
- bzero(x4_s_proof, x4_s_proof_len);
- free(x4_s_proof);
-
- /* Expect step 2 packet from peer */
- dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP2,
- input_userauth_jpake_client_step2);
-}
-
-/* ARGSUSED */
-static void
-input_userauth_jpake_client_step2(int type, u_int32_t seq, void *ctxt)
-{
- Authctxt *authctxt = ctxt;
- struct jpake_ctx *pctx = authctxt->jpake_ctx;
- u_char *x2_s_proof;
- u_int x2_s_proof_len;
-
- /* Disable this message */
- dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP2, NULL);
-
- if ((pctx->a = BN_new()) == NULL)
- fatal("%s: BN_new", __func__);
-
- /* Fetch step 2 values */
- packet_get_bignum2(pctx->a);
- x2_s_proof = packet_get_string(&x2_s_proof_len);
- packet_check_eom();
-
- if (!use_privsep)
- JPAKE_DEBUG_CTX((pctx, "step 2 received in %s", __func__));
-
- /* Derive shared key and calculate confirmation hash */
- PRIVSEP(jpake_key_confirm(pctx->grp, pctx->s, pctx->a,
- pctx->x4, pctx->g_x3, pctx->g_x4, pctx->g_x1, pctx->g_x2,
- pctx->server_id, pctx->server_id_len,
- pctx->client_id, pctx->client_id_len,
- session_id2, session_id2_len,
- x2_s_proof, x2_s_proof_len,
- &pctx->k,
- &pctx->h_k_sid_sessid, &pctx->h_k_sid_sessid_len));
-
- bzero(x2_s_proof, x2_s_proof_len);
- free(x2_s_proof);
-
- if (!use_privsep)
- JPAKE_DEBUG_CTX((pctx, "confirm sending in %s", __func__));
-
- /* Send key confirmation proof */
- packet_start(SSH2_MSG_USERAUTH_JPAKE_SERVER_CONFIRM);
- packet_put_string(pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len);
- packet_send();
- packet_write_wait();
-
- /* Expect confirmation from peer */
- dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_CONFIRM,
- input_userauth_jpake_client_confirm);
-}
-
-/* ARGSUSED */
-static void
-input_userauth_jpake_client_confirm(int type, u_int32_t seq, void *ctxt)
-{
- Authctxt *authctxt = ctxt;
- struct jpake_ctx *pctx = authctxt->jpake_ctx;
- int authenticated = 0;
-
- /* Disable this message */
- dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_CONFIRM, NULL);
-
- pctx->h_k_cid_sessid = packet_get_string(&pctx->h_k_cid_sessid_len);
- packet_check_eom();
-
- if (!use_privsep)
- JPAKE_DEBUG_CTX((pctx, "confirm received in %s", __func__));
-
- /* Verify expected confirmation hash */
- if (PRIVSEP(jpake_check_confirm(pctx->k,
- pctx->client_id, pctx->client_id_len,
- session_id2, session_id2_len,
- pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len)) == 1)
- authenticated = authctxt->valid ? 1 : 0;
- else
- debug("%s: confirmation mismatch", __func__);
-
- /* done */
- authctxt->postponed = 0;
- jpake_free(authctxt->jpake_ctx);
- authctxt->jpake_ctx = NULL;
- userauth_finish(authctxt, authenticated, method_jpake.name, NULL);
-}
-
-#endif /* JPAKE */
-