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sonic-openssh/auth2-jpake.c

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/* $OpenBSD: auth2-jpake.c,v 1.3 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.
*/
/*
* 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;
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);
}
/*
* 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));
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 */
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