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support for requiring user verified FIDO keys in sshd

This adds a "verify-required" authorized_keys flag and a corresponding
sshd_config option that tells sshd to require that FIDO keys verify the
user identity before completing the signing/authentication attempt.
Whether or not user verification was performed is already baked into the
signature made on the FIDO token, so this is just plumbing that flag
through and adding ways to require it.

feedback and ok markus@

/* $OpenBSD: monitor.c,v 1.214 2020/08/27 01:07:09 djm Exp $ */
/*
 * Copyright 2002 Niels Provos <provos@citi.umich.edu>
 * Copyright 2002 Markus Friedl <markus@openbsd.org>
 * 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 <sys/types.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/tree.h>
#include <sys/queue.h>

#ifdef WITH_OPENSSL
#include <openssl/dh.h>
#endif

#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <paths.h>
#include <poll.h>
#include <pwd.h>
#include <signal.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "atomicio.h"
#include "xmalloc.h"
#include "ssh.h"
#include "sshkey.h"
#include "sshbuf.h"
#include "hostfile.h"
#include "auth.h"
#include "cipher.h"
#include "kex.h"
#include "dh.h"
#include "packet.h"
#include "auth-options.h"
#include "sshpty.h"
#include "channels.h"
#include "session.h"
#include "sshlogin.h"
#include "canohost.h"
#include "log.h"
#include "misc.h"
#include "servconf.h"
#include "monitor.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "monitor_fdpass.h"
#include "compat.h"
#include "ssh2.h"
#include "authfd.h"
#include "match.h"
#include "ssherr.h"
#include "sk-api.h"

#ifdef GSSAPI
static Gssctxt *gsscontext = NULL;
#endif

/* Imports */
extern ServerOptions options;
extern u_int utmp_len;
extern u_char session_id[];
extern struct sshbuf *loginmsg;
extern struct sshauthopt *auth_opts; /* XXX move to permanent ssh->authctxt? */

/* State exported from the child */
static struct sshbuf *child_state;

/* Functions on the monitor that answer unprivileged requests */

int mm_answer_moduli(struct ssh *, int, struct sshbuf *);
int mm_answer_sign(struct ssh *, int, struct sshbuf *);
int mm_answer_pwnamallow(struct ssh *, int, struct sshbuf *);
int mm_answer_auth2_read_banner(struct ssh *, int, struct sshbuf *);
int mm_answer_authserv(struct ssh *, int, struct sshbuf *);
int mm_answer_authpassword(struct ssh *, int, struct sshbuf *);
int mm_answer_bsdauthquery(struct ssh *, int, struct sshbuf *);
int mm_answer_bsdauthrespond(struct ssh *, int, struct sshbuf *);
int mm_answer_skeyquery(struct ssh *, int, struct sshbuf *);
int mm_answer_skeyrespond(struct ssh *, int, struct sshbuf *);
int mm_answer_keyallowed(struct ssh *, int, struct sshbuf *);
int mm_answer_keyverify(struct ssh *, int, struct sshbuf *);
int mm_answer_pty(struct ssh *, int, struct sshbuf *);
int mm_answer_pty_cleanup(struct ssh *, int, struct sshbuf *);
int mm_answer_term(struct ssh *, int, struct sshbuf *);
int mm_answer_rsa_keyallowed(struct ssh *, int, struct sshbuf *);
int mm_answer_rsa_challenge(struct ssh *, int, struct sshbuf *);
int mm_answer_rsa_response(struct ssh *, int, struct sshbuf *);
int mm_answer_sesskey(struct ssh *, int, struct sshbuf *);
int mm_answer_sessid(struct ssh *, int, struct sshbuf *);

#ifdef GSSAPI
int mm_answer_gss_setup_ctx(struct ssh *, int, struct sshbuf *);
int mm_answer_gss_accept_ctx(struct ssh *, int, struct sshbuf *);
int mm_answer_gss_userok(struct ssh *, int, struct sshbuf *);
int mm_answer_gss_checkmic(struct ssh *, int, struct sshbuf *);
#endif

static Authctxt *authctxt;

/* local state for key verify */
static u_char *key_blob = NULL;
static size_t key_bloblen = 0;
static int key_blobtype = MM_NOKEY;
static struct sshauthopt *key_opts = NULL;
static char *hostbased_cuser = NULL;
static char *hostbased_chost = NULL;
static char *auth_method = "unknown";
static char *auth_submethod = NULL;
static u_int session_id2_len = 0;
static u_char *session_id2 = NULL;
static pid_t monitor_child_pid;

struct mon_table {
	enum monitor_reqtype type;
	int flags;
	int (*f)(struct ssh *, int, struct sshbuf *);
};

#define MON_ISAUTH	0x0004	/* Required for Authentication */
#define MON_AUTHDECIDE	0x0008	/* Decides Authentication */
#define MON_ONCE	0x0010	/* Disable after calling */
#define MON_ALOG	0x0020	/* Log auth attempt without authenticating */

#define MON_AUTH	(MON_ISAUTH|MON_AUTHDECIDE)

#define MON_PERMIT	0x1000	/* Request is permitted */

static int monitor_read(struct ssh *, struct monitor *, struct mon_table *,
    struct mon_table **);
static int monitor_read_log(struct monitor *);

struct mon_table mon_dispatch_proto20[] = {
#ifdef WITH_OPENSSL
    {MONITOR_REQ_MODULI, MON_ONCE, mm_answer_moduli},
#endif
    {MONITOR_REQ_SIGN, MON_ONCE, mm_answer_sign},
    {MONITOR_REQ_PWNAM, MON_ONCE, mm_answer_pwnamallow},
    {MONITOR_REQ_AUTHSERV, MON_ONCE, mm_answer_authserv},
    {MONITOR_REQ_AUTH2_READ_BANNER, MON_ONCE, mm_answer_auth2_read_banner},
    {MONITOR_REQ_AUTHPASSWORD, MON_AUTH, mm_answer_authpassword},
    {MONITOR_REQ_BSDAUTHQUERY, MON_ISAUTH, mm_answer_bsdauthquery},
    {MONITOR_REQ_BSDAUTHRESPOND, MON_AUTH, mm_answer_bsdauthrespond},
    {MONITOR_REQ_KEYALLOWED, MON_ISAUTH, mm_answer_keyallowed},
    {MONITOR_REQ_KEYVERIFY, MON_AUTH, mm_answer_keyverify},
#ifdef GSSAPI
    {MONITOR_REQ_GSSSETUP, MON_ISAUTH, mm_answer_gss_setup_ctx},
    {MONITOR_REQ_GSSSTEP, 0, mm_answer_gss_accept_ctx},
    {MONITOR_REQ_GSSUSEROK, MON_ONCE|MON_AUTHDECIDE, mm_answer_gss_userok},
    {MONITOR_REQ_GSSCHECKMIC, MON_ONCE, mm_answer_gss_checkmic},
#endif
    {0, 0, NULL}
};

struct mon_table mon_dispatch_postauth20[] = {
#ifdef WITH_OPENSSL
    {MONITOR_REQ_MODULI, 0, mm_answer_moduli},
#endif
    {MONITOR_REQ_SIGN, 0, mm_answer_sign},
    {MONITOR_REQ_PTY, 0, mm_answer_pty},
    {MONITOR_REQ_PTYCLEANUP, 0, mm_answer_pty_cleanup},
    {MONITOR_REQ_TERM, 0, mm_answer_term},
    {0, 0, NULL}
};

struct mon_table *mon_dispatch;

/* Specifies if a certain message is allowed at the moment */
static void
monitor_permit(struct mon_table *ent, enum monitor_reqtype type, int permit)
{
	while (ent->f != NULL) {
		if (ent->type == type) {
			ent->flags &= ~MON_PERMIT;
			ent->flags |= permit ? MON_PERMIT : 0;
			return;
		}
		ent++;
	}
}

static void
monitor_permit_authentications(int permit)
{
	struct mon_table *ent = mon_dispatch;

	while (ent->f != NULL) {
		if (ent->flags & MON_AUTH) {
			ent->flags &= ~MON_PERMIT;
			ent->flags |= permit ? MON_PERMIT : 0;
		}
		ent++;
	}
}

void
monitor_child_preauth(struct ssh *ssh, struct monitor *pmonitor)
{
	struct mon_table *ent;
	int authenticated = 0, partial = 0;

	debug3("preauth child monitor started");

	if (pmonitor->m_recvfd >= 0)
		close(pmonitor->m_recvfd);
	if (pmonitor->m_log_sendfd >= 0)
		close(pmonitor->m_log_sendfd);
	pmonitor->m_log_sendfd = pmonitor->m_recvfd = -1;

	authctxt = (Authctxt *)ssh->authctxt;
	memset(authctxt, 0, sizeof(*authctxt));
	ssh->authctxt = authctxt;

	mon_dispatch = mon_dispatch_proto20;
	/* Permit requests for moduli and signatures */
	monitor_permit(mon_dispatch, MONITOR_REQ_MODULI, 1);
	monitor_permit(mon_dispatch, MONITOR_REQ_SIGN, 1);

	/* The first few requests do not require asynchronous access */
	while (!authenticated) {
		partial = 0;
		auth_method = "unknown";
		auth_submethod = NULL;
		auth2_authctxt_reset_info(authctxt);

		authenticated = (monitor_read(ssh, pmonitor,
		    mon_dispatch, &ent) == 1);

		/* Special handling for multiple required authentications */
		if (options.num_auth_methods != 0) {
			if (authenticated &&
			    !auth2_update_methods_lists(authctxt,
			    auth_method, auth_submethod)) {
				debug3("%s: method %s: partial", __func__,
				    auth_method);
				authenticated = 0;
				partial = 1;
			}
		}

		if (authenticated) {
			if (!(ent->flags & MON_AUTHDECIDE))
				fatal("%s: unexpected authentication from %d",
				    __func__, ent->type);
			if (authctxt->pw->pw_uid == 0 &&
			    !auth_root_allowed(ssh, auth_method))
				authenticated = 0;
		}
		if (ent->flags & (MON_AUTHDECIDE|MON_ALOG)) {
			auth_log(ssh, authenticated, partial,
			    auth_method, auth_submethod);
			if (!partial && !authenticated)
				authctxt->failures++;
			if (authenticated || partial) {
				auth2_update_session_info(authctxt,
				    auth_method, auth_submethod);
			}
		}
	}

	if (!authctxt->valid)
		fatal("%s: authenticated invalid user", __func__);
	if (strcmp(auth_method, "unknown") == 0)
		fatal("%s: authentication method name unknown", __func__);

	debug("%s: %s has been authenticated by privileged process",
	    __func__, authctxt->user);
	ssh->authctxt = NULL;
	ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);

	mm_get_keystate(ssh, pmonitor);

	/* Drain any buffered messages from the child */
	while (pmonitor->m_log_recvfd != -1 && monitor_read_log(pmonitor) == 0)
		;

	if (pmonitor->m_recvfd >= 0)
		close(pmonitor->m_recvfd);
	if (pmonitor->m_log_sendfd >= 0)
		close(pmonitor->m_log_sendfd);
	pmonitor->m_sendfd = pmonitor->m_log_recvfd = -1;
}

static void
monitor_set_child_handler(pid_t pid)
{
	monitor_child_pid = pid;
}

static void
monitor_child_handler(int sig)
{
	kill(monitor_child_pid, sig);
}

void
monitor_child_postauth(struct ssh *ssh, struct monitor *pmonitor)
{
	close(pmonitor->m_recvfd);
	pmonitor->m_recvfd = -1;

	monitor_set_child_handler(pmonitor->m_pid);
	ssh_signal(SIGHUP, &monitor_child_handler);
	ssh_signal(SIGTERM, &monitor_child_handler);
	ssh_signal(SIGINT, &monitor_child_handler);

	mon_dispatch = mon_dispatch_postauth20;

	/* Permit requests for moduli and signatures */
	monitor_permit(mon_dispatch, MONITOR_REQ_MODULI, 1);
	monitor_permit(mon_dispatch, MONITOR_REQ_SIGN, 1);
	monitor_permit(mon_dispatch, MONITOR_REQ_TERM, 1);

	if (auth_opts->permit_pty_flag) {
		monitor_permit(mon_dispatch, MONITOR_REQ_PTY, 1);
		monitor_permit(mon_dispatch, MONITOR_REQ_PTYCLEANUP, 1);
	}

	for (;;)
		monitor_read(ssh, pmonitor, mon_dispatch, NULL);
}

static int
monitor_read_log(struct monitor *pmonitor)
{
	struct sshbuf *logmsg;
	u_int len, level;
	char *msg;
	u_char *p;
	int r;

	if ((logmsg = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new", __func__);

	/* Read length */
	if ((r = sshbuf_reserve(logmsg, 4, &p)) != 0)
		fatal("%s: reserve: %s", __func__, ssh_err(r));
	if (atomicio(read, pmonitor->m_log_recvfd, p, 4) != 4) {
		if (errno == EPIPE) {
			sshbuf_free(logmsg);
			debug("%s: child log fd closed", __func__);
			close(pmonitor->m_log_recvfd);
			pmonitor->m_log_recvfd = -1;
			return -1;
		}
		fatal("%s: log fd read: %s", __func__, strerror(errno));
	}
	if ((r = sshbuf_get_u32(logmsg, &len)) != 0)
		fatal("%s: get len: %s", __func__, ssh_err(r));
	if (len <= 4 || len > 8192)
		fatal("%s: invalid log message length %u", __func__, len);

	/* Read severity, message */
	sshbuf_reset(logmsg);
	if ((r = sshbuf_reserve(logmsg, len, &p)) != 0)
		fatal("%s: reserve: %s", __func__, ssh_err(r));
	if (atomicio(read, pmonitor->m_log_recvfd, p, len) != len)
		fatal("%s: log fd read: %s", __func__, strerror(errno));
	if ((r = sshbuf_get_u32(logmsg, &level)) != 0 ||
	    (r = sshbuf_get_cstring(logmsg, &msg, NULL)) != 0)
		fatal("%s: decode: %s", __func__, ssh_err(r));

	/* Log it */
	if (log_level_name(level) == NULL)
		fatal("%s: invalid log level %u (corrupted message?)",
		    __func__, level);
	do_log2(level, "%s [preauth]", msg);

	sshbuf_free(logmsg);
	free(msg);

	return 0;
}

static int
monitor_read(struct ssh *ssh, struct monitor *pmonitor, struct mon_table *ent,
    struct mon_table **pent)
{
	struct sshbuf *m;
	int r, ret;
	u_char type;
	struct pollfd pfd[2];

	for (;;) {
		memset(&pfd, 0, sizeof(pfd));
		pfd[0].fd = pmonitor->m_sendfd;
		pfd[0].events = POLLIN;
		pfd[1].fd = pmonitor->m_log_recvfd;
		pfd[1].events = pfd[1].fd == -1 ? 0 : POLLIN;
		if (poll(pfd, pfd[1].fd == -1 ? 1 : 2, -1) == -1) {
			if (errno == EINTR || errno == EAGAIN)
				continue;
			fatal("%s: poll: %s", __func__, strerror(errno));
		}
		if (pfd[1].revents) {
			/*
			 * Drain all log messages before processing next
			 * monitor request.
			 */
			monitor_read_log(pmonitor);
			continue;
		}
		if (pfd[0].revents)
			break;  /* Continues below */
	}

	if ((m = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new", __func__);

	mm_request_receive(pmonitor->m_sendfd, m);
	if ((r = sshbuf_get_u8(m, &type)) != 0)
		fatal("%s: decode: %s", __func__, ssh_err(r));

	debug3("%s: checking request %d", __func__, type);

	while (ent->f != NULL) {
		if (ent->type == type)
			break;
		ent++;
	}

	if (ent->f != NULL) {
		if (!(ent->flags & MON_PERMIT))
			fatal("%s: unpermitted request %d", __func__,
			    type);
		ret = (*ent->f)(ssh, pmonitor->m_sendfd, m);
		sshbuf_free(m);

		/* The child may use this request only once, disable it */
		if (ent->flags & MON_ONCE) {
			debug2("%s: %d used once, disabling now", __func__,
			    type);
			ent->flags &= ~MON_PERMIT;
		}

		if (pent != NULL)
			*pent = ent;

		return ret;
	}

	fatal("%s: unsupported request: %d", __func__, type);

	/* NOTREACHED */
	return (-1);
}

/* allowed key state */
static int
monitor_allowed_key(const u_char *blob, u_int bloblen)
{
	/* make sure key is allowed */
	if (key_blob == NULL || key_bloblen != bloblen ||
	    timingsafe_bcmp(key_blob, blob, key_bloblen))
		return (0);
	return (1);
}

static void
monitor_reset_key_state(void)
{
	/* reset state */
	free(key_blob);
	free(hostbased_cuser);
	free(hostbased_chost);
	sshauthopt_free(key_opts);
	key_blob = NULL;
	key_bloblen = 0;
	key_blobtype = MM_NOKEY;
	key_opts = NULL;
	hostbased_cuser = NULL;
	hostbased_chost = NULL;
}

#ifdef WITH_OPENSSL
int
mm_answer_moduli(struct ssh *ssh, int sock, struct sshbuf *m)
{
	DH *dh;
	const BIGNUM *dh_p, *dh_g;
	int r;
	u_int min, want, max;

	if ((r = sshbuf_get_u32(m, &min)) != 0 ||
	    (r = sshbuf_get_u32(m, &want)) != 0 ||
	    (r = sshbuf_get_u32(m, &max)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	debug3("%s: got parameters: %d %d %d",
	    __func__, min, want, max);
	/* We need to check here, too, in case the child got corrupted */
	if (max < min || want < min || max < want)
		fatal("%s: bad parameters: %d %d %d",
		    __func__, min, want, max);

	sshbuf_reset(m);

	dh = choose_dh(min, want, max);
	if (dh == NULL) {
		if ((r = sshbuf_put_u8(m, 0)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
		return (0);
	} else {
		/* Send first bignum */
		DH_get0_pqg(dh, &dh_p, NULL, &dh_g);
		if ((r = sshbuf_put_u8(m, 1)) != 0 ||
		    (r = sshbuf_put_bignum2(m, dh_p)) != 0 ||
		    (r = sshbuf_put_bignum2(m, dh_g)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));

		DH_free(dh);
	}
	mm_request_send(sock, MONITOR_ANS_MODULI, m);
	return (0);
}
#endif

int
mm_answer_sign(struct ssh *ssh, int sock, struct sshbuf *m)
{
	extern int auth_sock;			/* XXX move to state struct? */
	struct sshkey *key;
	struct sshbuf *sigbuf = NULL;
	u_char *p = NULL, *signature = NULL;
	char *alg = NULL;
	size_t datlen, siglen, alglen;
	int r, is_proof = 0;
	u_int keyid, compat;
	const char proof_req[] = "hostkeys-prove-00@openssh.com";

	debug3("%s", __func__);

	if ((r = sshbuf_get_u32(m, &keyid)) != 0 ||
	    (r = sshbuf_get_string(m, &p, &datlen)) != 0 ||
	    (r = sshbuf_get_cstring(m, &alg, &alglen)) != 0 ||
	    (r = sshbuf_get_u32(m, &compat)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (keyid > INT_MAX)
		fatal("%s: invalid key ID", __func__);

	/*
	 * Supported KEX types use SHA1 (20 bytes), SHA256 (32 bytes),
	 * SHA384 (48 bytes) and SHA512 (64 bytes).
	 *
	 * Otherwise, verify the signature request is for a hostkey
	 * proof.
	 *
	 * XXX perform similar check for KEX signature requests too?
	 * it's not trivial, since what is signed is the hash, rather
	 * than the full kex structure...
	 */
	if (datlen != 20 && datlen != 32 && datlen != 48 && datlen != 64) {
		/*
		 * Construct expected hostkey proof and compare it to what
		 * the client sent us.
		 */
		if (session_id2_len == 0) /* hostkeys is never first */
			fatal("%s: bad data length: %zu", __func__, datlen);
		if ((key = get_hostkey_public_by_index(keyid, ssh)) == NULL)
			fatal("%s: no hostkey for index %d", __func__, keyid);
		if ((sigbuf = sshbuf_new()) == NULL)
			fatal("%s: sshbuf_new", __func__);
		if ((r = sshbuf_put_cstring(sigbuf, proof_req)) != 0 ||
		    (r = sshbuf_put_string(sigbuf, session_id2,
		    session_id2_len)) != 0 ||
		    (r = sshkey_puts(key, sigbuf)) != 0)
			fatal("%s: couldn't prepare private key "
			    "proof buffer: %s", __func__, ssh_err(r));
		if (datlen != sshbuf_len(sigbuf) ||
		    memcmp(p, sshbuf_ptr(sigbuf), sshbuf_len(sigbuf)) != 0)
			fatal("%s: bad data length: %zu, hostkey proof len %zu",
			    __func__, datlen, sshbuf_len(sigbuf));
		sshbuf_free(sigbuf);
		is_proof = 1;
	}

	/* save session id, it will be passed on the first call */
	if (session_id2_len == 0) {
		session_id2_len = datlen;
		session_id2 = xmalloc(session_id2_len);
		memcpy(session_id2, p, session_id2_len);
	}

	if ((key = get_hostkey_by_index(keyid)) != NULL) {
		if ((r = sshkey_sign(key, &signature, &siglen, p, datlen, alg,
		    options.sk_provider, NULL, compat)) != 0)
			fatal("%s: sshkey_sign failed: %s",
			    __func__, ssh_err(r));
	} else if ((key = get_hostkey_public_by_index(keyid, ssh)) != NULL &&
	    auth_sock > 0) {
		if ((r = ssh_agent_sign(auth_sock, key, &signature, &siglen,
		    p, datlen, alg, compat)) != 0) {
			fatal("%s: ssh_agent_sign failed: %s",
			    __func__, ssh_err(r));
		}
	} else
		fatal("%s: no hostkey from index %d", __func__, keyid);

	debug3("%s: %s signature %p(%zu)", __func__,
	    is_proof ? "hostkey proof" : "KEX", signature, siglen);

	sshbuf_reset(m);
	if ((r = sshbuf_put_string(m, signature, siglen)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	free(alg);
	free(p);
	free(signature);

	mm_request_send(sock, MONITOR_ANS_SIGN, m);

	/* Turn on permissions for getpwnam */
	monitor_permit(mon_dispatch, MONITOR_REQ_PWNAM, 1);

	return (0);
}

/* Retrieves the password entry and also checks if the user is permitted */

int
mm_answer_pwnamallow(struct ssh *ssh, int sock, struct sshbuf *m)
{
	char *username;
	struct passwd *pwent;
	int r, allowed = 0;
	u_int i;

	debug3("%s", __func__);

	if (authctxt->attempt++ != 0)
		fatal("%s: multiple attempts for getpwnam", __func__);

	if ((r = sshbuf_get_cstring(m, &username, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	pwent = getpwnamallow(ssh, username);

	authctxt->user = xstrdup(username);
	setproctitle("%s [priv]", pwent ? username : "unknown");
	free(username);

	sshbuf_reset(m);

	if (pwent == NULL) {
		if ((r = sshbuf_put_u8(m, 0)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
		authctxt->pw = fakepw();
		goto out;
	}

	allowed = 1;
	authctxt->pw = pwent;
	authctxt->valid = 1;

	/* XXX don't sent pwent to unpriv; send fake class/dir/shell too */
	if ((r = sshbuf_put_u8(m, 1)) != 0 ||
	    (r = sshbuf_put_string(m, pwent, sizeof(*pwent))) != 0 ||
	    (r = sshbuf_put_cstring(m, pwent->pw_name)) != 0 ||
	    (r = sshbuf_put_cstring(m, "*")) != 0 ||
	    (r = sshbuf_put_cstring(m, pwent->pw_gecos)) != 0 ||
	    (r = sshbuf_put_cstring(m, pwent->pw_class)) != 0 ||
	    (r = sshbuf_put_cstring(m, pwent->pw_dir)) != 0 ||
	    (r = sshbuf_put_cstring(m, pwent->pw_shell)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

 out:
	ssh_packet_set_log_preamble(ssh, "%suser %s",
	    authctxt->valid ? "authenticating" : "invalid ", authctxt->user);
	if ((r = sshbuf_put_string(m, &options, sizeof(options))) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

#define M_CP_STROPT(x) do { \
		if (options.x != NULL) { \
			if ((r = sshbuf_put_cstring(m, options.x)) != 0) \
				fatal("%s: buffer error: %s", \
				    __func__, ssh_err(r)); \
		} \
	} while (0)
#define M_CP_STRARRAYOPT(x, nx) do { \
		for (i = 0; i < options.nx; i++) { \
			if ((r = sshbuf_put_cstring(m, options.x[i])) != 0) \
				fatal("%s: buffer error: %s", \
				    __func__, ssh_err(r)); \
		} \
	} while (0)
	/* See comment in servconf.h */
	COPY_MATCH_STRING_OPTS();
#undef M_CP_STROPT
#undef M_CP_STRARRAYOPT

	/* Create valid auth method lists */
	if (auth2_setup_methods_lists(authctxt) != 0) {
		/*
		 * The monitor will continue long enough to let the child
		 * run to it's packet_disconnect(), but it must not allow any
		 * authentication to succeed.
		 */
		debug("%s: no valid authentication method lists", __func__);
	}

	debug3("%s: sending MONITOR_ANS_PWNAM: %d", __func__, allowed);
	mm_request_send(sock, MONITOR_ANS_PWNAM, m);

	/* Allow service/style information on the auth context */
	monitor_permit(mon_dispatch, MONITOR_REQ_AUTHSERV, 1);
	monitor_permit(mon_dispatch, MONITOR_REQ_AUTH2_READ_BANNER, 1);

	return (0);
}

int mm_answer_auth2_read_banner(struct ssh *ssh, int sock, struct sshbuf *m)
{
	char *banner;
	int r;

	sshbuf_reset(m);
	banner = auth2_read_banner();
	if ((r = sshbuf_put_cstring(m, banner != NULL ? banner : "")) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	mm_request_send(sock, MONITOR_ANS_AUTH2_READ_BANNER, m);
	free(banner);

	return (0);
}

int
mm_answer_authserv(struct ssh *ssh, int sock, struct sshbuf *m)
{
	int r;

	monitor_permit_authentications(1);

	if ((r = sshbuf_get_cstring(m, &authctxt->service, NULL)) != 0 ||
	    (r = sshbuf_get_cstring(m, &authctxt->style, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	debug3("%s: service=%s, style=%s",
	    __func__, authctxt->service, authctxt->style);

	if (strlen(authctxt->style) == 0) {
		free(authctxt->style);
		authctxt->style = NULL;
	}

	return (0);
}

int
mm_answer_authpassword(struct ssh *ssh, int sock, struct sshbuf *m)
{
	static int call_count;
	char *passwd;
	int r, authenticated;
	size_t plen;

	if (!options.password_authentication)
		fatal("%s: password authentication not enabled", __func__);
	if ((r = sshbuf_get_cstring(m, &passwd, &plen)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	/* Only authenticate if the context is valid */
	authenticated = options.password_authentication &&
	    auth_password(ssh, passwd);
	freezero(passwd, plen);

	sshbuf_reset(m);
	if ((r = sshbuf_put_u32(m, authenticated)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	debug3("%s: sending result %d", __func__, authenticated);
	mm_request_send(sock, MONITOR_ANS_AUTHPASSWORD, m);

	call_count++;
	if (plen == 0 && call_count == 1)
		auth_method = "none";
	else
		auth_method = "password";

	/* Causes monitor loop to terminate if authenticated */
	return (authenticated);
}

int
mm_answer_bsdauthquery(struct ssh *ssh, int sock, struct sshbuf *m)
{
	char *name, *infotxt;
	u_int numprompts, *echo_on, success;
	char **prompts;
	int r;

	if (!options.kbd_interactive_authentication)
		fatal("%s: kbd-int authentication not enabled", __func__);
	success = bsdauth_query(authctxt, &name, &infotxt, &numprompts,
	    &prompts, &echo_on) < 0 ? 0 : 1;

	sshbuf_reset(m);
	if ((r = sshbuf_put_u32(m, success)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (success) {
		if ((r = sshbuf_put_cstring(m, prompts[0])) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
	}

	debug3("%s: sending challenge success: %u", __func__, success);
	mm_request_send(sock, MONITOR_ANS_BSDAUTHQUERY, m);

	if (success) {
		free(name);
		free(infotxt);
		free(prompts);
		free(echo_on);
	}

	return (0);
}

int
mm_answer_bsdauthrespond(struct ssh *ssh, int sock, struct sshbuf *m)
{
	char *response;
	int r, authok;

	if (!options.kbd_interactive_authentication)
		fatal("%s: kbd-int authentication not enabled", __func__);
	if (authctxt->as == NULL)
		fatal("%s: no bsd auth session", __func__);

	if ((r = sshbuf_get_cstring(m, &response, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	authok = options.challenge_response_authentication &&
	    auth_userresponse(authctxt->as, response, 0);
	authctxt->as = NULL;
	debug3("%s: <%s> = <%d>", __func__, response, authok);
	free(response);

	sshbuf_reset(m);
	if ((r = sshbuf_put_u32(m, authok)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	debug3("%s: sending authenticated: %d", __func__, authok);
	mm_request_send(sock, MONITOR_ANS_BSDAUTHRESPOND, m);

	auth_method = "keyboard-interactive";
	auth_submethod = "bsdauth";

	return (authok != 0);
}

/*
 * Check that the key type appears in the supplied pattern list, ignoring
 * mismatches in the signature algorithm. (Signature algorithm checks are
 * performed in the unprivileged authentication code).
 * Returns 1 on success, 0 otherwise.
 */
static int
key_base_type_match(const char *method, const struct sshkey *key,
    const char *list)
{
	char *s, *l, *ol = xstrdup(list);
	int found = 0;

	l = ol;
	for ((s = strsep(&l, ",")); s && *s != '\0'; (s = strsep(&l, ","))) {
		if (sshkey_type_from_name(s) == key->type) {
			found = 1;
			break;
		}
	}
	if (!found) {
		error("%s key type %s is not in permitted list %s", method,
		    sshkey_ssh_name(key), list);
	}

	free(ol);
	return found;
}

int
mm_answer_keyallowed(struct ssh *ssh, int sock, struct sshbuf *m)
{
	struct sshkey *key = NULL;
	char *cuser, *chost;
	u_int pubkey_auth_attempt;
	enum mm_keytype type = 0;
	int r, allowed = 0;
	struct sshauthopt *opts = NULL;

	debug3("%s entering", __func__);
	if ((r = sshbuf_get_u32(m, &type)) != 0 ||
	    (r = sshbuf_get_cstring(m, &cuser, NULL)) != 0 ||
	    (r = sshbuf_get_cstring(m, &chost, NULL)) != 0 ||
	    (r = sshkey_froms(m, &key)) != 0 ||
	    (r = sshbuf_get_u32(m, &pubkey_auth_attempt)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	debug3("%s: key_from_blob: %p", __func__, key);

	if (key != NULL && authctxt->valid) {
		/* These should not make it past the privsep child */
		if (sshkey_type_plain(key->type) == KEY_RSA &&
		    (datafellows & SSH_BUG_RSASIGMD5) != 0)
			fatal("%s: passed a SSH_BUG_RSASIGMD5 key", __func__);

		switch (type) {
		case MM_USERKEY:
			auth_method = "publickey";
			if (!options.pubkey_authentication)
				break;
			if (auth2_key_already_used(authctxt, key))
				break;
			if (!key_base_type_match(auth_method, key,
			    options.pubkey_key_types))
				break;
			allowed = user_key_allowed(ssh, authctxt->pw, key,
			    pubkey_auth_attempt, &opts);
			break;
		case MM_HOSTKEY:
			auth_method = "hostbased";
			if (!options.hostbased_authentication)
				break;
			if (auth2_key_already_used(authctxt, key))
				break;
			if (!key_base_type_match(auth_method, key,
			    options.hostbased_key_types))
				break;
			allowed = hostbased_key_allowed(ssh, authctxt->pw,
			    cuser, chost, key);
			auth2_record_info(authctxt,
			    "client user \"%.100s\", client host \"%.100s\"",
			    cuser, chost);
			break;
		default:
			fatal("%s: unknown key type %d", __func__, type);
			break;
		}
	}

	debug3("%s: %s authentication%s: %s key is %s", __func__,
	    auth_method, pubkey_auth_attempt ? "" : " test",
	    (key == NULL || !authctxt->valid) ? "invalid" : sshkey_type(key),
	    allowed ? "allowed" : "not allowed");

	auth2_record_key(authctxt, 0, key);

	/* clear temporarily storage (used by verify) */
	monitor_reset_key_state();

	if (allowed) {
		/* Save temporarily for comparison in verify */
		if ((r = sshkey_to_blob(key, &key_blob, &key_bloblen)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
		key_blobtype = type;
		key_opts = opts;
		hostbased_cuser = cuser;
		hostbased_chost = chost;
	} else {
		/* Log failed attempt */
		auth_log(ssh, 0, 0, auth_method, NULL);
		free(cuser);
		free(chost);
	}
	sshkey_free(key);

	sshbuf_reset(m);
	if ((r = sshbuf_put_u32(m, allowed)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (opts != NULL && (r = sshauthopt_serialise(opts, m, 1)) != 0)
		fatal("%s: sshauthopt_serialise: %s", __func__, ssh_err(r));
	mm_request_send(sock, MONITOR_ANS_KEYALLOWED, m);

	if (!allowed)
		sshauthopt_free(opts);

	return (0);
}

static int
monitor_valid_userblob(const u_char *data, u_int datalen)
{
	struct sshbuf *b;
	const u_char *p;
	char *userstyle, *cp;
	size_t len;
	u_char type;
	int r, fail = 0;

	if ((b = sshbuf_from(data, datalen)) == NULL)
		fatal("%s: sshbuf_from", __func__);

	if (datafellows & SSH_OLD_SESSIONID) {
		p = sshbuf_ptr(b);
		len = sshbuf_len(b);
		if ((session_id2 == NULL) ||
		    (len < session_id2_len) ||
		    (timingsafe_bcmp(p, session_id2, session_id2_len) != 0))
			fail++;
		if ((r = sshbuf_consume(b, session_id2_len)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
	} else {
		if ((r = sshbuf_get_string_direct(b, &p, &len)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
		if ((session_id2 == NULL) ||
		    (len != session_id2_len) ||
		    (timingsafe_bcmp(p, session_id2, session_id2_len) != 0))
			fail++;
	}
	if ((r = sshbuf_get_u8(b, &type)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (type != SSH2_MSG_USERAUTH_REQUEST)
		fail++;
	if ((r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	xasprintf(&userstyle, "%s%s%s", authctxt->user,
	    authctxt->style ? ":" : "",
	    authctxt->style ? authctxt->style : "");
	if (strcmp(userstyle, cp) != 0) {
		logit("wrong user name passed to monitor: "
		    "expected %s != %.100s", userstyle, cp);
		fail++;
	}
	free(userstyle);
	free(cp);
	if ((r = sshbuf_skip_string(b)) != 0 ||	/* service */
	    (r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (strcmp("publickey", cp) != 0)
		fail++;
	free(cp);
	if ((r = sshbuf_get_u8(b, &type)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (type == 0)
		fail++;
	if ((r = sshbuf_skip_string(b)) != 0 ||	/* pkalg */
	    (r = sshbuf_skip_string(b)) != 0)	/* pkblob */
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (sshbuf_len(b) != 0)
		fail++;
	sshbuf_free(b);
	return (fail == 0);
}

static int
monitor_valid_hostbasedblob(const u_char *data, u_int datalen,
    const char *cuser, const char *chost)
{
	struct sshbuf *b;
	const u_char *p;
	char *cp, *userstyle;
	size_t len;
	int r, fail = 0;
	u_char type;

	if ((b = sshbuf_from(data, datalen)) == NULL)
		fatal("%s: sshbuf_new", __func__);
	if ((r = sshbuf_get_string_direct(b, &p, &len)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	if ((session_id2 == NULL) ||
	    (len != session_id2_len) ||
	    (timingsafe_bcmp(p, session_id2, session_id2_len) != 0))
		fail++;

	if ((r = sshbuf_get_u8(b, &type)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (type != SSH2_MSG_USERAUTH_REQUEST)
		fail++;
	if ((r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	xasprintf(&userstyle, "%s%s%s", authctxt->user,
	    authctxt->style ? ":" : "",
	    authctxt->style ? authctxt->style : "");
	if (strcmp(userstyle, cp) != 0) {
		logit("wrong user name passed to monitor: "
		    "expected %s != %.100s", userstyle, cp);
		fail++;
	}
	free(userstyle);
	free(cp);
	if ((r = sshbuf_skip_string(b)) != 0 ||	/* service */
	    (r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (strcmp(cp, "hostbased") != 0)
		fail++;
	free(cp);
	if ((r = sshbuf_skip_string(b)) != 0 ||	/* pkalg */
	    (r = sshbuf_skip_string(b)) != 0)	/* pkblob */
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	/* verify client host, strip trailing dot if necessary */
	if ((r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (((len = strlen(cp)) > 0) && cp[len - 1] == '.')
		cp[len - 1] = '\0';
	if (strcmp(cp, chost) != 0)
		fail++;
	free(cp);

	/* verify client user */
	if ((r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (strcmp(cp, cuser) != 0)
		fail++;
	free(cp);

	if (sshbuf_len(b) != 0)
		fail++;
	sshbuf_free(b);
	return (fail == 0);
}

int
mm_answer_keyverify(struct ssh *ssh, int sock, struct sshbuf *m)
{
	struct sshkey *key;
	const u_char *signature, *data, *blob;
	char *sigalg = NULL, *fp = NULL;
	size_t signaturelen, datalen, bloblen;
	int r, ret, req_presence = 0, req_verify = 0, valid_data = 0;
	int encoded_ret;
	struct sshkey_sig_details *sig_details = NULL;

	if ((r = sshbuf_get_string_direct(m, &blob, &bloblen)) != 0 ||
	    (r = sshbuf_get_string_direct(m, &signature, &signaturelen)) != 0 ||
	    (r = sshbuf_get_string_direct(m, &data, &datalen)) != 0 ||
	    (r = sshbuf_get_cstring(m, &sigalg, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	if (hostbased_cuser == NULL || hostbased_chost == NULL ||
	  !monitor_allowed_key(blob, bloblen))
		fatal("%s: bad key, not previously allowed", __func__);

	/* Empty signature algorithm means NULL. */
	if (*sigalg == '\0') {
		free(sigalg);
		sigalg = NULL;
	}

	/* XXX use sshkey_froms here; need to change key_blob, etc. */
	if ((r = sshkey_from_blob(blob, bloblen, &key)) != 0)
		fatal("%s: bad public key blob: %s", __func__, ssh_err(r));

	switch (key_blobtype) {
	case MM_USERKEY:
		valid_data = monitor_valid_userblob(data, datalen);
		auth_method = "publickey";
		break;
	case MM_HOSTKEY:
		valid_data = monitor_valid_hostbasedblob(data, datalen,
		    hostbased_cuser, hostbased_chost);
		auth_method = "hostbased";
		break;
	default:
		valid_data = 0;
		break;
	}
	if (!valid_data)
		fatal("%s: bad signature data blob", __func__);

	if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
	    SSH_FP_DEFAULT)) == NULL)
		fatal("%s: sshkey_fingerprint failed", __func__);

	ret = sshkey_verify(key, signature, signaturelen, data, datalen,
	    sigalg, ssh->compat, &sig_details);
	debug3("%s: %s %p signature %s%s%s", __func__, auth_method, key,
	    (ret == 0) ? "verified" : "unverified",
	    (ret != 0) ? ": " : "", (ret != 0) ? ssh_err(ret) : "");

	if (ret == 0 && key_blobtype == MM_USERKEY && sig_details != NULL) {
		req_presence = (options.pubkey_auth_options &
		    PUBKEYAUTH_TOUCH_REQUIRED) ||
		    !key_opts->no_require_user_presence;
		if (req_presence &&
		    (sig_details->sk_flags & SSH_SK_USER_PRESENCE_REQD) == 0) {
			error("public key %s %s signature for %s%s from %.128s "
			    "port %d rejected: user presence "
			    "(authenticator touch) requirement not met ",
			    sshkey_type(key), fp,
			    authctxt->valid ? "" : "invalid user ",
			    authctxt->user, ssh_remote_ipaddr(ssh),
			    ssh_remote_port(ssh));
			ret = SSH_ERR_SIGNATURE_INVALID;
		}
		req_verify = (options.pubkey_auth_options &
		    PUBKEYAUTH_VERIFY_REQUIRED) || key_opts->require_verify;
		if (req_verify &&
		    (sig_details->sk_flags & SSH_SK_USER_VERIFICATION_REQD) == 0) {
			error("public key %s %s signature for %s%s from %.128s "
			    "port %d rejected: user verification requirement "
			    "not met ", sshkey_type(key), fp,
			    authctxt->valid ? "" : "invalid user ",
			    authctxt->user, ssh_remote_ipaddr(ssh),
			    ssh_remote_port(ssh));
			ret = SSH_ERR_SIGNATURE_INVALID;
		}
	}
	auth2_record_key(authctxt, ret == 0, key);

	if (key_blobtype == MM_USERKEY)
		auth_activate_options(ssh, key_opts);
	monitor_reset_key_state();

	sshbuf_reset(m);

	/* encode ret != 0 as positive integer, since we're sending u32 */
	encoded_ret = (ret != 0);
	if ((r = sshbuf_put_u32(m, encoded_ret)) != 0 ||
	    (r = sshbuf_put_u8(m, sig_details != NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (sig_details != NULL) {
		if ((r = sshbuf_put_u32(m, sig_details->sk_counter)) != 0 ||
		    (r = sshbuf_put_u8(m, sig_details->sk_flags)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
	}
	sshkey_sig_details_free(sig_details);
	mm_request_send(sock, MONITOR_ANS_KEYVERIFY, m);

	free(sigalg);
	free(fp);
	sshkey_free(key);

	return ret == 0;
}

static void
mm_record_login(struct ssh *ssh, Session *s, struct passwd *pw)
{
	socklen_t fromlen;
	struct sockaddr_storage from;

	/*
	 * Get IP address of client. If the connection is not a socket, let
	 * the address be 0.0.0.0.
	 */
	memset(&from, 0, sizeof(from));
	fromlen = sizeof(from);
	if (ssh_packet_connection_is_on_socket(ssh)) {
		if (getpeername(ssh_packet_get_connection_in(ssh),
		    (struct sockaddr *)&from, &fromlen) == -1) {
			debug("getpeername: %.100s", strerror(errno));
			cleanup_exit(255);
		}
	}
	/* Record that there was a login on that tty from the remote host. */
	record_login(s->pid, s->tty, pw->pw_name, pw->pw_uid,
	    session_get_remote_name_or_ip(ssh, utmp_len, options.use_dns),
	    (struct sockaddr *)&from, fromlen);
}

static void
mm_session_close(Session *s)
{
	debug3("%s: session %d pid %ld", __func__, s->self, (long)s->pid);
	if (s->ttyfd != -1) {
		debug3("%s: tty %s ptyfd %d", __func__, s->tty, s->ptyfd);
		session_pty_cleanup2(s);
	}
	session_unused(s->self);
}

int
mm_answer_pty(struct ssh *ssh, int sock, struct sshbuf *m)
{
	extern struct monitor *pmonitor;
	Session *s;
	int r, res, fd0;

	debug3("%s entering", __func__);

	sshbuf_reset(m);
	s = session_new();
	if (s == NULL)
		goto error;
	s->authctxt = authctxt;
	s->pw = authctxt->pw;
	s->pid = pmonitor->m_pid;
	res = pty_allocate(&s->ptyfd, &s->ttyfd, s->tty, sizeof(s->tty));
	if (res == 0)
		goto error;
	pty_setowner(authctxt->pw, s->tty);

	if ((r = sshbuf_put_u32(m, 1)) != 0 ||
	    (r = sshbuf_put_cstring(m, s->tty)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	/* We need to trick ttyslot */
	if (dup2(s->ttyfd, 0) == -1)
		fatal("%s: dup2", __func__);

	mm_record_login(ssh, s, authctxt->pw);

	/* Now we can close the file descriptor again */
	close(0);

	/* send messages generated by record_login */
	if ((r = sshbuf_put_stringb(m, loginmsg)) != 0)
		fatal("%s: put login message: %s", __func__, ssh_err(r));
	sshbuf_reset(loginmsg);

	mm_request_send(sock, MONITOR_ANS_PTY, m);

	if (mm_send_fd(sock, s->ptyfd) == -1 ||
	    mm_send_fd(sock, s->ttyfd) == -1)
		fatal("%s: send fds failed", __func__);

	/* make sure nothing uses fd 0 */
	if ((fd0 = open(_PATH_DEVNULL, O_RDONLY)) == -1)
		fatal("%s: open(/dev/null): %s", __func__, strerror(errno));
	if (fd0 != 0)
		error("%s: fd0 %d != 0", __func__, fd0);

	/* slave side of pty is not needed */
	close(s->ttyfd);
	s->ttyfd = s->ptyfd;
	/* no need to dup() because nobody closes ptyfd */
	s->ptymaster = s->ptyfd;

	debug3("%s: tty %s ptyfd %d", __func__, s->tty, s->ttyfd);

	return (0);

 error:
	if (s != NULL)
		mm_session_close(s);
	if ((r = sshbuf_put_u32(m, 0)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	mm_request_send(sock, MONITOR_ANS_PTY, m);
	return (0);
}

int
mm_answer_pty_cleanup(struct ssh *ssh, int sock, struct sshbuf *m)
{
	Session *s;
	char *tty;
	int r;

	debug3("%s entering", __func__);

	if ((r = sshbuf_get_cstring(m, &tty, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if ((s = session_by_tty(tty)) != NULL)
		mm_session_close(s);
	sshbuf_reset(m);
	free(tty);
	return (0);
}

int
mm_answer_term(struct ssh *ssh, int sock, struct sshbuf *req)
{
	extern struct monitor *pmonitor;
	int res, status;

	debug3("%s: tearing down sessions", __func__);

	/* The child is terminating */
	session_destroy_all(ssh, &mm_session_close);

	while (waitpid(pmonitor->m_pid, &status, 0) == -1)
		if (errno != EINTR)
			exit(1);

	res = WIFEXITED(status) ? WEXITSTATUS(status) : 1;

	/* Terminate process */
	exit(res);
}

void
monitor_clear_keystate(struct ssh *ssh, struct monitor *pmonitor)
{
	ssh_clear_newkeys(ssh, MODE_IN);
	ssh_clear_newkeys(ssh, MODE_OUT);
	sshbuf_free(child_state);
	child_state = NULL;
}

void
monitor_apply_keystate(struct ssh *ssh, struct monitor *pmonitor)
{
	struct kex *kex;
	int r;

	debug3("%s: packet_set_state", __func__);
	if ((r = ssh_packet_set_state(ssh, child_state)) != 0)
                fatal("%s: packet_set_state: %s", __func__, ssh_err(r));
	sshbuf_free(child_state);
	child_state = NULL;

	if ((kex = ssh->kex) != NULL) {
		/* XXX set callbacks */
#ifdef WITH_OPENSSL
		kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
		kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
		kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
		kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
		kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
		kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
		kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
		kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
#endif
		kex->kex[KEX_C25519_SHA256] = kex_gen_server;
		kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_server;
		kex->load_host_public_key=&get_hostkey_public_by_type;
		kex->load_host_private_key=&get_hostkey_private_by_type;
		kex->host_key_index=&get_hostkey_index;
		kex->sign = sshd_hostkey_sign;
	}
}

/* This function requires careful sanity checking */

void
mm_get_keystate(struct ssh *ssh, struct monitor *pmonitor)
{
	debug3("%s: Waiting for new keys", __func__);

	if ((child_state = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	mm_request_receive_expect(pmonitor->m_sendfd, MONITOR_REQ_KEYEXPORT,
	    child_state);
	debug3("%s: GOT new keys", __func__);
}


/* XXX */

#define FD_CLOSEONEXEC(x) do { \
	if (fcntl(x, F_SETFD, FD_CLOEXEC) == -1) \
		fatal("fcntl(%d, F_SETFD)", x); \
} while (0)

static void
monitor_openfds(struct monitor *mon, int do_logfds)
{
	int pair[2];
#ifdef SO_ZEROIZE
	int on = 1;
#endif

	if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1)
		fatal("%s: socketpair: %s", __func__, strerror(errno));
#ifdef SO_ZEROIZE
	if (setsockopt(pair[0], SOL_SOCKET, SO_ZEROIZE, &on, sizeof(on)) == -1)
		error("setsockopt SO_ZEROIZE(0): %.100s", strerror(errno));
	if (setsockopt(pair[1], SOL_SOCKET, SO_ZEROIZE, &on, sizeof(on)) == -1)
		error("setsockopt SO_ZEROIZE(1): %.100s", strerror(errno));
#endif
	FD_CLOSEONEXEC(pair[0]);
	FD_CLOSEONEXEC(pair[1]);
	mon->m_recvfd = pair[0];
	mon->m_sendfd = pair[1];

	if (do_logfds) {
		if (pipe(pair) == -1)
			fatal("%s: pipe: %s", __func__, strerror(errno));
		FD_CLOSEONEXEC(pair[0]);
		FD_CLOSEONEXEC(pair[1]);
		mon->m_log_recvfd = pair[0];
		mon->m_log_sendfd = pair[1];
	} else
		mon->m_log_recvfd = mon->m_log_sendfd = -1;
}

#define MM_MEMSIZE	65536

struct monitor *
monitor_init(void)
{
	struct monitor *mon;

	mon = xcalloc(1, sizeof(*mon));
	monitor_openfds(mon, 1);

	return mon;
}

void
monitor_reinit(struct monitor *mon)
{
	monitor_openfds(mon, 0);
}

#ifdef GSSAPI
int
mm_answer_gss_setup_ctx(struct ssh *ssh, int sock, struct sshbuf *m)
{
	gss_OID_desc goid;
	OM_uint32 major;
	size_t len;
	u_char *p;
	int r;

	if (!options.gss_authentication)
		fatal("%s: GSSAPI authentication not enabled", __func__);

	if ((r = sshbuf_get_string(m, &p, &len)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	goid.elements = p;
	goid.length = len;

	major = ssh_gssapi_server_ctx(&gsscontext, &goid);

	free(goid.elements);

	sshbuf_reset(m);
	if ((r = sshbuf_put_u32(m, major)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	mm_request_send(sock, MONITOR_ANS_GSSSETUP, m);

	/* Now we have a context, enable the step */
	monitor_permit(mon_dispatch, MONITOR_REQ_GSSSTEP, 1);

	return (0);
}

int
mm_answer_gss_accept_ctx(struct ssh *ssh, int sock, struct sshbuf *m)
{
	gss_buffer_desc in;
	gss_buffer_desc out = GSS_C_EMPTY_BUFFER;
	OM_uint32 major, minor;
	OM_uint32 flags = 0; /* GSI needs this */
	int r;

	if (!options.gss_authentication)
		fatal("%s: GSSAPI authentication not enabled", __func__);

	if ((r = ssh_gssapi_get_buffer_desc(m, &in)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	major = ssh_gssapi_accept_ctx(gsscontext, &in, &out, &flags);
	free(in.value);

	sshbuf_reset(m);
	if ((r = sshbuf_put_u32(m, major)) != 0 ||
	    (r = sshbuf_put_string(m, out.value, out.length)) != 0 ||
	    (r = sshbuf_put_u32(m, flags)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	mm_request_send(sock, MONITOR_ANS_GSSSTEP, m);

	gss_release_buffer(&minor, &out);

	if (major == GSS_S_COMPLETE) {
		monitor_permit(mon_dispatch, MONITOR_REQ_GSSSTEP, 0);
		monitor_permit(mon_dispatch, MONITOR_REQ_GSSUSEROK, 1);
		monitor_permit(mon_dispatch, MONITOR_REQ_GSSCHECKMIC, 1);
	}
	return (0);
}

int
mm_answer_gss_checkmic(struct ssh *ssh, int sock, struct sshbuf *m)
{
	gss_buffer_desc gssbuf, mic;
	OM_uint32 ret;
	int r;

	if (!options.gss_authentication)
		fatal("%s: GSSAPI authentication not enabled", __func__);

	if ((r = ssh_gssapi_get_buffer_desc(m, &gssbuf)) != 0 ||
	    (r = ssh_gssapi_get_buffer_desc(m, &mic)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	ret = ssh_gssapi_checkmic(gsscontext, &gssbuf, &mic);

	free(gssbuf.value);
	free(mic.value);

	sshbuf_reset(m);
	if ((r = sshbuf_put_u32(m, ret)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	mm_request_send(sock, MONITOR_ANS_GSSCHECKMIC, m);

	if (!GSS_ERROR(ret))
		monitor_permit(mon_dispatch, MONITOR_REQ_GSSUSEROK, 1);

	return (0);
}

int
mm_answer_gss_userok(struct ssh *ssh, int sock, struct sshbuf *m)
{
	int r, authenticated;
	const char *displayname;

	if (!options.gss_authentication)
		fatal("%s: GSSAPI authentication not enabled", __func__);

	authenticated = authctxt->valid && ssh_gssapi_userok(authctxt->user);

	sshbuf_reset(m);
	if ((r = sshbuf_put_u32(m, authenticated)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	debug3("%s: sending result %d", __func__, authenticated);
	mm_request_send(sock, MONITOR_ANS_GSSUSEROK, m);

	auth_method = "gssapi-with-mic";

	if ((displayname = ssh_gssapi_displayname()) != NULL)
		auth2_record_info(authctxt, "%s", displayname);

	/* Monitor loop will terminate if authenticated */
	return (authenticated);
}
#endif /* GSSAPI */