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auth2-chall.c
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auth2-chall.c
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/* $OpenBSD: auth2-chall.c,v 1.54 2020/10/18 11:32:01 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 <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include "xmalloc.h"
#include "ssh2.h"
#include "sshkey.h"
#include "hostfile.h"
#include "auth.h"
#include "sshbuf.h"
#include "packet.h"
#include "dispatch.h"
#include "ssherr.h"
#include "log.h"
#include "misc.h"
#include "servconf.h"
/* import */
extern ServerOptions options;
static int auth2_challenge_start(struct ssh *);
static int send_userauth_info_request(struct ssh *);
static int input_userauth_info_response(int, u_int32_t, struct ssh *);
#ifdef BSD_AUTH
extern KbdintDevice bsdauth_device;
#else
#ifdef USE_PAM
extern KbdintDevice sshpam_device;
#endif
#endif
KbdintDevice *devices[] = {
#ifdef BSD_AUTH
&bsdauth_device,
#else
#ifdef USE_PAM
&sshpam_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;
struct sshbuf *b;
int i, r;
#ifdef USE_PAM
if (!options.use_pam)
remove_kbdint_device("pam");
#endif
kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt));
if (strcmp(devs, "") == 0) {
if ((b = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
for (i = 0; devices[i]; i++) {
if ((r = sshbuf_putf(b, "%s%s",
sshbuf_len(b) ? "," : "", devices[i]->name)) != 0)
fatal_fr(r, "buffer error");
}
if ((kbdintctxt->devices = sshbuf_dup_string(b)) == NULL)
fatal_f("sshbuf_dup_string failed");
sshbuf_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);
freezero(kbdintctxt, sizeof(*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(struct ssh *ssh, char *devs)
{
Authctxt *authctxt = ssh->authctxt;
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(ssh);
}
/* unregister kbd-int callbacks and context */
void
auth2_challenge_stop(struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
/* unregister callback */
ssh_dispatch_set(ssh, 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(struct ssh *ssh)
{
Authctxt *authctxt = ssh->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(ssh);
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(ssh);
return 0;
}
if (send_userauth_info_request(ssh) == 0) {
auth2_challenge_stop(ssh);
return 0;
}
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE,
&input_userauth_info_response);
authctxt->postponed = 1;
return 0;
}
static int
send_userauth_info_request(struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
KbdintAuthctxt *kbdintctxt;
char *name, *instr, **prompts;
u_int r, i, *echo_on;
kbdintctxt = authctxt->kbdintctxt;
if (kbdintctxt->device->query(kbdintctxt->ctxt,
&name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
return 0;
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_INFO_REQUEST)) != 0 ||
(r = sshpkt_put_cstring(ssh, name)) != 0 ||
(r = sshpkt_put_cstring(ssh, instr)) != 0 ||
(r = sshpkt_put_cstring(ssh, "")) != 0 || /* language not used */
(r = sshpkt_put_u32(ssh, kbdintctxt->nreq)) != 0)
fatal_fr(r, "start packet");
for (i = 0; i < kbdintctxt->nreq; i++) {
if ((r = sshpkt_put_cstring(ssh, prompts[i])) != 0 ||
(r = sshpkt_put_u8(ssh, echo_on[i])) != 0)
fatal_fr(r, "assemble packet");
}
if ((r = sshpkt_send(ssh)) != 0 ||
(r = ssh_packet_write_wait(ssh)) != 0)
fatal_fr(r, "send packet");
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, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
KbdintAuthctxt *kbdintctxt;
int authenticated = 0, res;
int r;
u_int i, nresp;
const char *devicename = NULL;
char **response = NULL;
if (authctxt == NULL)
fatal_f("no authctxt");
kbdintctxt = authctxt->kbdintctxt;
if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
fatal_f("no kbdintctxt");
if (kbdintctxt->device == NULL)
fatal_f("no device");
authctxt->postponed = 0; /* reset */
if ((r = sshpkt_get_u32(ssh, &nresp)) != 0)
fatal_fr(r, "parse packet");
if (nresp != kbdintctxt->nreq)
fatal_f("wrong number of replies");
if (nresp > 100)
fatal_f("too many replies");
if (nresp > 0) {
response = xcalloc(nresp, sizeof(char *));
for (i = 0; i < nresp; i++) {
if ((r = sshpkt_get_cstring(ssh, &response[i], NULL)) != 0)
fatal_fr(r, "parse response");
}
}
if ((r = sshpkt_get_end(ssh)) != 0)
fatal_fr(r, "parse packet");
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(ssh) == 1)
authctxt->postponed = 1;
break;
default:
/* Failure! */
break;
}
devicename = kbdintctxt->device->name;
if (!authctxt->postponed) {
if (authenticated) {
auth2_challenge_stop(ssh);
} else {
/* start next device */
/* may set authctxt->postponed */
auth2_challenge_start(ssh);
}
}
userauth_finish(ssh, authenticated, "keyboard-interactive",
devicename);
return 0;
}
void
privsep_challenge_enable(void)
{
#if defined(BSD_AUTH) || defined(USE_PAM)
int n = 0;
#endif
#ifdef BSD_AUTH
extern KbdintDevice mm_bsdauth_device;
#endif
#ifdef USE_PAM
extern KbdintDevice mm_sshpam_device;
#endif
#ifdef BSD_AUTH
devices[n++] = &mm_bsdauth_device;
#else
#ifdef USE_PAM
devices[n++] = &mm_sshpam_device;
#endif
#endif
}