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Have keyboard-interactive code call the drivers even for responses for
invalid logins.  This allows the drivers themselves to decide how to handle
them and prevent leaking information where possible.  Existing behaviour for
bsdauth is maintained by checking authctxt->valid in the bsdauth driver.
Note that any third-party kbdint drivers will now need to be able to handle
responses for invalid logins.  ok markus@

/*
 * 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"
RCSID("$OpenBSD: auth2-chall.c,v 1.22 2005/01/19 13:11:47 dtucker Exp $");

#include "ssh2.h"
#include "auth.h"
#include "buffer.h"
#include "packet.h"
#include "xmalloc.h"
#include "dispatch.h"
#include "log.h"

static int auth2_challenge_start(Authctxt *);
static int send_userauth_info_request(Authctxt *);
static void input_userauth_info_response(int, u_int32_t, void *);

#ifdef BSD_AUTH
extern KbdintDevice bsdauth_device;
#else
#ifdef SKEY
extern KbdintDevice skey_device;
#endif
#endif

KbdintDevice *devices[] = {
#ifdef BSD_AUTH
	&bsdauth_device,
#else
#ifdef SKEY
	&skey_device,
#endif
#endif
	NULL
};

typedef struct KbdintAuthctxt KbdintAuthctxt;
struct KbdintAuthctxt
{
	char *devices;
	void *ctxt;
	KbdintDevice *device;
	u_int nreq;
};

static KbdintAuthctxt *
kbdint_alloc(const char *devs)
{
	KbdintAuthctxt *kbdintctxt;
	Buffer b;
	int i;

	kbdintctxt = xmalloc(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));
		}
		buffer_append(&b, "\0", 1);
		kbdintctxt->devices = xstrdup(buffer_ptr(&b));
		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);
	if (kbdintctxt->devices) {
		xfree(kbdintctxt->devices);
		kbdintctxt->devices = NULL;
	}
	xfree(kbdintctxt);
}
/* get next device */
static int
kbdint_next_device(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 (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0)
				kbdintctxt->device = devices[i];
		t = kbdintctxt->devices;
		kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
		xfree(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(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;
	int i;
	u_int *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++)
		xfree(prompts[i]);
	xfree(prompts);
	xfree(echo_on);
	xfree(name);
	xfree(instr);
	return 1;
}

static void
input_userauth_info_response(int type, u_int32_t seq, void *ctxt)
{
	Authctxt *authctxt = ctxt;
	KbdintAuthctxt *kbdintctxt;
	int i, authenticated = 0, res, len;
	u_int nresp;
	char **response = NULL, *method;

	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 = xmalloc(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++) {
		memset(response[i], 'r', strlen(response[i]));
		xfree(response[i]);
	}
	if (response)
		xfree(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;
	}

	len = strlen("keyboard-interactive") + 2 +
		strlen(kbdintctxt->device->name);
	method = xmalloc(len);
	snprintf(method, len, "keyboard-interactive/%s",
	    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, method);
	xfree(method);
}

void
privsep_challenge_enable(void)
{
#ifdef BSD_AUTH
	extern KbdintDevice mm_bsdauth_device;
#endif
#ifdef SKEY
	extern KbdintDevice mm_skey_device;
#endif
	/* As long as SSHv1 has devices[0] hard coded this is fine */
#ifdef BSD_AUTH
	devices[0] = &mm_bsdauth_device;
#else
#ifdef SKEY
	devices[0] = &mm_skey_device;
#endif
#endif
}