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-rw-r--r--auth2-jpake.c557
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diff --git a/auth2-jpake.c b/auth2-jpake.c
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+/* $OpenBSD: auth2-jpake.c,v 1.1 2008/11/04 08:22:12 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
+ */
+
+#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 "buffer.h"
+#include "auth.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 "jpake.h"
+
+#ifdef JPAKE
+
+/*
+ * 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;
+ 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);
+ xfree(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");
+ }
+ xfree(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);
+ xfree(secret);
+}
+
+/*
+ * Being 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));
+ xfree(hash_scheme);
+ xfree(salt);
+ bzero(x3_proof, x3_proof_len);
+ bzero(x4_proof, x4_proof_len);
+ xfree(x3_proof);
+ xfree(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);
+ xfree(x1_proof);
+ xfree(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);
+ xfree(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);
+ xfree(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);
+}
+
+#endif /* JPAKE */
+
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-31 03:03:14 +0000