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auth2-chall.c
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/* $OpenBSD: auth2-chall.c,v 1.44 2016/05/02 08:49:03 djm Exp $ */
/*
* Copyright (c) 2001 Markus Friedl. All rights reserved.
* Copyright (c) 2001 Per Allansson. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
#include <sys/types.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.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 "misc.h"
#include "servconf.h"
/* import */
extern ServerOptions options;
static int auth2_challenge_start(Authctxt *);
static int send_userauth_info_request(Authctxt *);
static int input_userauth_info_response(int, u_int32_t, void *);
#ifdef BSD_AUTH
extern KbdintDevice bsdauth_device;
#else
#ifdef USE_PAM
extern KbdintDevice sshpam_device;
#endif
#ifdef SKEY
extern KbdintDevice skey_device;
#endif
#endif
KbdintDevice *devices[] = {
#ifdef BSD_AUTH
&bsdauth_device,
#else
#ifdef USE_PAM
&sshpam_device,
#endif
#ifdef SKEY
&skey_device,
#endif
#endif
NULL
};
typedef struct KbdintAuthctxt KbdintAuthctxt;
struct KbdintAuthctxt
{
char *devices;
void *ctxt;
KbdintDevice *device;
u_int nreq;
u_int devices_done;
};
#ifdef USE_PAM
void
remove_kbdint_device(const char *devname)
{
int i, j;
for (i = 0; devices[i] != NULL; i++)
if (strcmp(devices[i]->name, devname) == 0) {
for (j = i; devices[j] != NULL; j++)
devices[j] = devices[j+1];
i--;
}
}
#endif
static KbdintAuthctxt *
kbdint_alloc(const char *devs)
{
KbdintAuthctxt *kbdintctxt;
Buffer b;
int i;
#ifdef USE_PAM
if (!options.use_pam)
remove_kbdint_device("pam");
#endif
kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt));
if (strcmp(devs, "") == 0) {
buffer_init(&b);
for (i = 0; devices[i]; i++) {
if (buffer_len(&b) > 0)
buffer_append(&b, ",", 1);
buffer_append(&b, devices[i]->name,
strlen(devices[i]->name));
}
if ((kbdintctxt->devices = sshbuf_dup_string(&b)) == NULL)
fatal("%s: sshbuf_dup_string failed", __func__);
buffer_free(&b);
} else {
kbdintctxt->devices = xstrdup(devs);
}
debug("kbdint_alloc: devices '%s'", kbdintctxt->devices);
kbdintctxt->ctxt = NULL;
kbdintctxt->device = NULL;
kbdintctxt->nreq = 0;
return kbdintctxt;
}
static void
kbdint_reset_device(KbdintAuthctxt *kbdintctxt)
{
if (kbdintctxt->ctxt) {
kbdintctxt->device->free_ctx(kbdintctxt->ctxt);
kbdintctxt->ctxt = NULL;
}
kbdintctxt->device = NULL;
}
static void
kbdint_free(KbdintAuthctxt *kbdintctxt)
{
if (kbdintctxt->device)
kbdint_reset_device(kbdintctxt);
free(kbdintctxt->devices);
explicit_bzero(kbdintctxt, sizeof(*kbdintctxt));
free(kbdintctxt);
}
/* get next device */
static int
kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt)
{
size_t len;
char *t;
int i;
if (kbdintctxt->device)
kbdint_reset_device(kbdintctxt);
do {
len = kbdintctxt->devices ?
strcspn(kbdintctxt->devices, ",") : 0;
if (len == 0)
break;
for (i = 0; devices[i]; i++) {
if ((kbdintctxt->devices_done & (1 << i)) != 0 ||
!auth2_method_allowed(authctxt,
"keyboard-interactive", devices[i]->name))
continue;
if (strncmp(kbdintctxt->devices, devices[i]->name,
len) == 0) {
kbdintctxt->device = devices[i];
kbdintctxt->devices_done |= 1 << i;
}
}
t = kbdintctxt->devices;
kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
free(t);
debug2("kbdint_next_device: devices %s", kbdintctxt->devices ?
kbdintctxt->devices : "<empty>");
} while (kbdintctxt->devices && !kbdintctxt->device);
return kbdintctxt->device ? 1 : 0;
}
/*
* try challenge-response, set authctxt->postponed if we have to
* wait for the response.
*/
int
auth2_challenge(Authctxt *authctxt, char *devs)
{
debug("auth2_challenge: user=%s devs=%s",
authctxt->user ? authctxt->user : "<nouser>",
devs ? devs : "<no devs>");
if (authctxt->user == NULL || !devs)
return 0;
if (authctxt->kbdintctxt == NULL)
authctxt->kbdintctxt = kbdint_alloc(devs);
return auth2_challenge_start(authctxt);
}
/* unregister kbd-int callbacks and context */
void
auth2_challenge_stop(Authctxt *authctxt)
{
/* unregister callback */
dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
if (authctxt->kbdintctxt != NULL) {
kbdint_free(authctxt->kbdintctxt);
authctxt->kbdintctxt = NULL;
}
}
/* side effect: sets authctxt->postponed if a reply was sent*/
static int
auth2_challenge_start(Authctxt *authctxt)
{
KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
debug2("auth2_challenge_start: devices %s",
kbdintctxt->devices ? kbdintctxt->devices : "<empty>");
if (kbdint_next_device(authctxt, kbdintctxt) == 0) {
auth2_challenge_stop(authctxt);
return 0;
}
debug("auth2_challenge_start: trying authentication method '%s'",
kbdintctxt->device->name);
if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
auth2_challenge_stop(authctxt);
return 0;
}
if (send_userauth_info_request(authctxt) == 0) {
auth2_challenge_stop(authctxt);
return 0;
}
dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE,
&input_userauth_info_response);
authctxt->postponed = 1;
return 0;
}
static int
send_userauth_info_request(Authctxt *authctxt)
{
KbdintAuthctxt *kbdintctxt;
char *name, *instr, **prompts;
u_int i, *echo_on;
kbdintctxt = authctxt->kbdintctxt;
if (kbdintctxt->device->query(kbdintctxt->ctxt,
&name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
return 0;
packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
packet_put_cstring(name);
packet_put_cstring(instr);
packet_put_cstring(""); /* language not used */
packet_put_int(kbdintctxt->nreq);
for (i = 0; i < kbdintctxt->nreq; i++) {
packet_put_cstring(prompts[i]);
packet_put_char(echo_on[i]);
}
packet_send();
packet_write_wait();
for (i = 0; i < kbdintctxt->nreq; i++)
free(prompts[i]);
free(prompts);
free(echo_on);
free(name);
free(instr);
return 1;
}
static int
input_userauth_info_response(int type, u_int32_t seq, void *ctxt)
{
Authctxt *authctxt = ctxt;
KbdintAuthctxt *kbdintctxt;
int authenticated = 0, res;
u_int i, nresp;
const char *devicename = NULL;
char **response = NULL;
if (authctxt == NULL)
fatal("input_userauth_info_response: no authctxt");
kbdintctxt = authctxt->kbdintctxt;
if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
fatal("input_userauth_info_response: no kbdintctxt");
if (kbdintctxt->device == NULL)
fatal("input_userauth_info_response: no device");
authctxt->postponed = 0; /* reset */
nresp = packet_get_int();
if (nresp != kbdintctxt->nreq)
fatal("input_userauth_info_response: wrong number of replies");
if (nresp > 100)
fatal("input_userauth_info_response: too many replies");
if (nresp > 0) {
response = xcalloc(nresp, sizeof(char *));
for (i = 0; i < nresp; i++)
response[i] = packet_get_string(NULL);
}
packet_check_eom();
res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
for (i = 0; i < nresp; i++) {
explicit_bzero(response[i], strlen(response[i]));
free(response[i]);
}
free(response);
switch (res) {
case 0:
/* Success! */
authenticated = authctxt->valid ? 1 : 0;
break;
case 1:
/* Authentication needs further interaction */
if (send_userauth_info_request(authctxt) == 1)
authctxt->postponed = 1;
break;
default:
/* Failure! */
break;
}
devicename = kbdintctxt->device->name;
if (!authctxt->postponed) {
if (authenticated) {
auth2_challenge_stop(authctxt);
} else {
/* start next device */
/* may set authctxt->postponed */
auth2_challenge_start(authctxt);
}
}
userauth_finish(authctxt, authenticated, "keyboard-interactive",
devicename);
return 0;
}
void
privsep_challenge_enable(void)
{
#if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY)
int n = 0;
#endif
#ifdef BSD_AUTH
extern KbdintDevice mm_bsdauth_device;
#endif
#ifdef USE_PAM
extern KbdintDevice mm_sshpam_device;
#endif
#ifdef SKEY
extern KbdintDevice mm_skey_device;
#endif
#ifdef BSD_AUTH
devices[n++] = &mm_bsdauth_device;
#else
#ifdef USE_PAM
devices[n++] = &mm_sshpam_device;
#endif
#ifdef SKEY
devices[n++] = &mm_skey_device;
#endif
#endif
}