zfs: merge openzfs/zfs@a382e2119

[FreeBSD/FreeBSD.git] / crypto / openssh / monitor.c

/* $OpenBSD: monitor.c,v 1.237 2023/08/16 16:14:11 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 "includes.h"

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>

#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#ifdef HAVE_PATHS_H
#include <paths.h>
#endif
#include <pwd.h>
#include <signal.h>
#ifdef HAVE_STDINT_H
# include <stdint.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <stdio.h>
#include <unistd.h>
#ifdef HAVE_POLL_H
#include <poll.h>
#else
# ifdef HAVE_SYS_POLL_H
#  include <sys/poll.h>
# endif
#endif

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

#include "openbsd-compat/sys-tree.h"
#include "openbsd-compat/sys-queue.h"
#include "openbsd-compat/openssl-compat.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 "auth-pam.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 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_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_sesskey(struct ssh *, int, struct sshbuf *);
int mm_answer_sessid(struct ssh *, int, struct sshbuf *);

#ifdef USE_PAM
int mm_answer_pam_start(struct ssh *, int, struct sshbuf *);
int mm_answer_pam_account(struct ssh *, int, struct sshbuf *);
int mm_answer_pam_init_ctx(struct ssh *, int, struct sshbuf *);
int mm_answer_pam_query(struct ssh *, int, struct sshbuf *);
int mm_answer_pam_respond(struct ssh *, int, struct sshbuf *);
int mm_answer_pam_free_ctx(struct ssh *, int, struct sshbuf *);
#endif

#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

#ifdef SSH_AUDIT_EVENTS
int mm_answer_audit_event(struct ssh *, int, struct sshbuf *);
int mm_answer_audit_command(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 u_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},
#ifdef USE_PAM
    {MONITOR_REQ_PAM_START, MON_ONCE, mm_answer_pam_start},
    {MONITOR_REQ_PAM_ACCOUNT, 0, mm_answer_pam_account},
    {MONITOR_REQ_PAM_INIT_CTX, MON_ONCE, mm_answer_pam_init_ctx},
    {MONITOR_REQ_PAM_QUERY, 0, mm_answer_pam_query},
    {MONITOR_REQ_PAM_RESPOND, MON_ONCE, mm_answer_pam_respond},
    {MONITOR_REQ_PAM_FREE_CTX, MON_ONCE|MON_AUTHDECIDE, mm_answer_pam_free_ctx},
#endif
#ifdef SSH_AUDIT_EVENTS
    {MONITOR_REQ_AUDIT_EVENT, MON_PERMIT, mm_answer_audit_event},
#endif
#ifdef BSD_AUTH
    {MONITOR_REQ_BSDAUTHQUERY, MON_ISAUTH, mm_answer_bsdauthquery},
    {MONITOR_REQ_BSDAUTHRESPOND, MON_AUTH, mm_answer_bsdauthrespond},
#endif
    {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},
#ifdef SSH_AUDIT_EVENTS
    {MONITOR_REQ_AUDIT_EVENT, MON_PERMIT, mm_answer_audit_event},
    {MONITOR_REQ_AUDIT_COMMAND, MON_PERMIT, mm_answer_audit_command},
#endif
    {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;

        authctxt->loginmsg = loginmsg;

        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_f("method %s: partial", auth_method);
                                authenticated = 0;
                                partial = 1;
                        }
                }

                if (authenticated) {
                        if (!(ent->flags & MON_AUTHDECIDE))
                                fatal_f("unexpected authentication from %d",
                                    ent->type);
                        if (authctxt->pw->pw_uid == 0 &&
                            !auth_root_allowed(ssh, auth_method))
                                authenticated = 0;
#ifdef USE_PAM
                        /* PAM needs to perform account checks after auth */
                        if (options.use_pam && authenticated) {
                                struct sshbuf *m;

                                if ((m = sshbuf_new()) == NULL)
                                        fatal("%s: sshbuf_new failed",
                                            __func__);
                                mm_request_receive_expect(pmonitor->m_sendfd,
                                    MONITOR_REQ_PAM_ACCOUNT, m);
                                authenticated = mm_answer_pam_account(
                                    ssh, pmonitor->m_sendfd, m);
                                sshbuf_free(m);
                        }
#endif
                }
                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->failures > options.max_authtries) {
                        /* Shouldn't happen */
                        fatal_f("privsep child made too many authentication "
                            "attempts");
                }
        }

        if (!authctxt->valid)
                fatal_f("authenticated invalid user");
        if (strcmp(auth_method, "unknown") == 0)
                fatal_f("authentication method name unknown");

        debug_f("user %s authenticated by privileged process", 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);
#ifdef SIGXFSZ
        ssh_signal(SIGXFSZ, SIG_IGN);
#endif

        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, forced;
        char *msg;
        u_char *p;
        int r;

        if ((logmsg = sshbuf_new()) == NULL)
                fatal_f("sshbuf_new");

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

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

        /* Log it */
        if (log_level_name(level) == NULL)
                fatal_f("invalid log level %u (corrupted message?)", level);
        sshlogdirect(level, forced, "%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_f("poll: %s", 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_f("sshbuf_new");

        mm_request_receive(pmonitor->m_sendfd, m);
        if ((r = sshbuf_get_u8(m, &type)) != 0)
                fatal_fr(r, "parse type");

        debug3_f("checking request %d", type);

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

        if (ent->f != NULL) {
                if (!(ent->flags & MON_PERMIT))
                        fatal_f("unpermitted request %d", 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_f("%d used once, disabling now", type);
                        ent->flags &= ~MON_PERMIT;
                }

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

                return ret;
        }

        fatal_f("unsupported request: %d", 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_fr(r, "parse");

        debug3_f("got parameters: %d %d %d", min, want, max);
        /* We need to check here, too, in case the child got corrupted */
        if (max < min || want < min || max < want)
                fatal_f("bad parameters: %d %d %d", min, want, max);

        sshbuf_reset(m);

        dh = choose_dh(min, want, max);
        if (dh == NULL) {
                if ((r = sshbuf_put_u8(m, 0)) != 0)
                        fatal_fr(r, "assemble empty");
                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_fr(r, "assemble");

                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_f("entering");

        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_fr(r, "parse");
        if (keyid > INT_MAX)
                fatal_f("invalid key ID");

        /*
         * 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_f("bad data length: %zu", datlen);
                if ((key = get_hostkey_public_by_index(keyid, ssh)) == NULL)
                        fatal_f("no hostkey for index %d", keyid);
                if ((sigbuf = sshbuf_new()) == NULL)
                        fatal_f("sshbuf_new");
                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_fr(r, "assemble private key proof");
                if (datlen != sshbuf_len(sigbuf) ||
                    memcmp(p, sshbuf_ptr(sigbuf), sshbuf_len(sigbuf)) != 0)
                        fatal_f("bad data length: %zu, hostkey proof len %zu",
                            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_fr(r, "sign");
        } 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_fr(r, "agent sign");
        } else
                fatal_f("no hostkey from index %d", keyid);

        debug3_f("%s %s signature len=%zu", alg,
            is_proof ? "hostkey proof" : "KEX", siglen);

        sshbuf_reset(m);
        if ((r = sshbuf_put_string(m, signature, siglen)) != 0)
                fatal_fr(r, "assemble");

        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);
}

#define PUTPW(b, id) \
        do { \
                if ((r = sshbuf_put_string(b, \
                    &pwent->id, sizeof(pwent->id))) != 0) \
                        fatal_fr(r, "assemble %s", #id); \
        } while (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)
{
        struct passwd *pwent;
        int r, allowed = 0;
        u_int i;

        debug3_f("entering");

        if (authctxt->attempt++ != 0)
                fatal_f("multiple attempts for getpwnam");

        if ((r = sshbuf_get_cstring(m, &authctxt->user, NULL)) != 0)
                fatal_fr(r, "parse");

        pwent = getpwnamallow(ssh, authctxt->user);

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

        sshbuf_reset(m);

        if (pwent == NULL) {
                if ((r = sshbuf_put_u8(m, 0)) != 0)
                        fatal_fr(r, "assemble fakepw");
                authctxt->pw = fakepw();
                goto out;
        }

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

        /* XXX send fake class/dir/shell, etc. */
        if ((r = sshbuf_put_u8(m, 1)) != 0)
                fatal_fr(r, "assemble ok");
        PUTPW(m, pw_uid);
        PUTPW(m, pw_gid);
#ifdef HAVE_STRUCT_PASSWD_PW_CHANGE
        PUTPW(m, pw_change);
#endif
#ifdef HAVE_STRUCT_PASSWD_PW_EXPIRE
        PUTPW(m, pw_expire);
#endif
        if ((r = sshbuf_put_cstring(m, pwent->pw_name)) != 0 ||
            (r = sshbuf_put_cstring(m, "*")) != 0 ||
#ifdef HAVE_STRUCT_PASSWD_PW_GECOS
            (r = sshbuf_put_cstring(m, pwent->pw_gecos)) != 0 ||
#endif
#ifdef HAVE_STRUCT_PASSWD_PW_CLASS
            (r = sshbuf_put_cstring(m, pwent->pw_class)) != 0 ||
#endif
            (r = sshbuf_put_cstring(m, pwent->pw_dir)) != 0 ||
            (r = sshbuf_put_cstring(m, pwent->pw_shell)) != 0)
                fatal_fr(r, "assemble pw");

 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_fr(r, "assemble options");

#define M_CP_STROPT(x) do { \
                if (options.x != NULL && \
                    (r = sshbuf_put_cstring(m, options.x)) != 0) \
                        fatal_fr(r, "assemble %s", #x); \
        } 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_fr(r, "assemble %s", #x); \
                } \
        } 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 its packet_disconnect(), but it must not allow any
                 * authentication to succeed.
                 */
                debug_f("no valid authentication method lists");
        }

        debug3_f("sending MONITOR_ANS_PWNAM: %d", 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);

#ifdef USE_PAM
        if (options.use_pam)
                monitor_permit(mon_dispatch, MONITOR_REQ_PAM_START, 1);
#endif

        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_fr(r, "assemble");
        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_fr(r, "parse");
        debug3_f("service=%s, style=%s", authctxt->service, authctxt->style);

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

        return (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_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_f("password authentication not enabled");
        if ((r = sshbuf_get_cstring(m, &passwd, &plen)) != 0)
                fatal_fr(r, "parse");
        /* 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_fr(r, "assemble");
#ifdef USE_PAM
        if ((r = sshbuf_put_u32(m, sshpam_get_maxtries_reached())) != 0)
                fatal_fr(r, "assemble PAM");
#endif

        debug3("%s: sending result %d", __func__, authenticated);
        debug3_f("sending result %d", 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);
}

#ifdef BSD_AUTH
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_f("kbd-int authentication not enabled");
        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_fr(r, "assemble");
        if (success) {
                if ((r = sshbuf_put_cstring(m, prompts[0])) != 0)
                        fatal_fr(r, "assemble prompt");
        }

        debug3_f("sending challenge success: %u", 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_f("kbd-int authentication not enabled");
        if (authctxt->as == NULL)
                fatal_f("no bsd auth session");

        if ((r = sshbuf_get_cstring(m, &response, NULL)) != 0)
                fatal_fr(r, "parse");
        authok = options.kbd_interactive_authentication &&
            auth_userresponse(authctxt->as, response, 0);
        authctxt->as = NULL;
        debug3_f("<%s> = <%d>", response, authok);
        free(response);

        sshbuf_reset(m);
        if ((r = sshbuf_put_u32(m, authok)) != 0)
                fatal_fr(r, "assemble");

        debug3_f("sending authenticated: %d", authok);
        mm_request_send(sock, MONITOR_ANS_BSDAUTHRESPOND, m);

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

        return (authok != 0);
}
#endif

#ifdef USE_PAM
int
mm_answer_pam_start(struct ssh *ssh, int sock, struct sshbuf *m)
{
        if (!options.use_pam)
                fatal("UsePAM not set, but ended up in %s anyway", __func__);

        start_pam(ssh);

        monitor_permit(mon_dispatch, MONITOR_REQ_PAM_ACCOUNT, 1);
        if (options.kbd_interactive_authentication)
                monitor_permit(mon_dispatch, MONITOR_REQ_PAM_INIT_CTX, 1);

        return (0);
}

int
mm_answer_pam_account(struct ssh *ssh, int sock, struct sshbuf *m)
{
        u_int ret;
        int r;

        if (!options.use_pam)
                fatal("%s: PAM not enabled", __func__);

        ret = do_pam_account();

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

        mm_request_send(sock, MONITOR_ANS_PAM_ACCOUNT, m);

        return (ret);
}

static void *sshpam_ctxt, *sshpam_authok;
extern KbdintDevice sshpam_device;

int
mm_answer_pam_init_ctx(struct ssh *ssh, int sock, struct sshbuf *m)
{
        u_int ok = 0;
        int r;

        debug3("%s", __func__);
        if (!options.kbd_interactive_authentication)
                fatal("%s: kbd-int authentication not enabled", __func__);
        if (sshpam_ctxt != NULL)
                fatal("%s: already called", __func__);
        sshpam_ctxt = (sshpam_device.init_ctx)(authctxt);
        sshpam_authok = NULL;
        sshbuf_reset(m);
        if (sshpam_ctxt != NULL) {
                monitor_permit(mon_dispatch, MONITOR_REQ_PAM_FREE_CTX, 1);
                monitor_permit(mon_dispatch, MONITOR_REQ_PAM_QUERY, 1);
                ok = 1;
        }
        if ((r = sshbuf_put_u32(m, ok)) != 0)
                fatal("%s: buffer error: %s", __func__, ssh_err(r));
        mm_request_send(sock, MONITOR_ANS_PAM_INIT_CTX, m);
        return (0);
}

int
mm_answer_pam_query(struct ssh *ssh, int sock, struct sshbuf *m)
{
        char *name = NULL, *info = NULL, **prompts = NULL;
        u_int i, num = 0, *echo_on = 0;
        int r, ret;

        debug3("%s", __func__);
        sshpam_authok = NULL;
        if (sshpam_ctxt == NULL)
                fatal("%s: no context", __func__);
        ret = (sshpam_device.query)(sshpam_ctxt, &name, &info,
            &num, &prompts, &echo_on);
        if (ret == 0 && num == 0)
                sshpam_authok = sshpam_ctxt;
        if (num > 1 || name == NULL || info == NULL)
                fatal("sshpam_device.query failed");
        monitor_permit(mon_dispatch, MONITOR_REQ_PAM_RESPOND, 1);
        sshbuf_reset(m);
        if ((r = sshbuf_put_u32(m, ret)) != 0 ||
            (r = sshbuf_put_cstring(m, name)) != 0 ||
            (r = sshbuf_put_cstring(m, info)) != 0 ||
            (r = sshbuf_put_u32(m, sshpam_get_maxtries_reached())) != 0 ||
            (r = sshbuf_put_u32(m, num)) != 0)
                fatal("%s: buffer error: %s", __func__, ssh_err(r));
        free(name);
        free(info);
        for (i = 0; i < num; ++i) {
                if ((r = sshbuf_put_cstring(m, prompts[i])) != 0 ||
                    (r = sshbuf_put_u32(m, echo_on[i])) != 0)
                        fatal("%s: buffer error: %s", __func__, ssh_err(r));
                free(prompts[i]);
        }
        free(prompts);
        free(echo_on);
        auth_method = "keyboard-interactive";
        auth_submethod = "pam";
        mm_request_send(sock, MONITOR_ANS_PAM_QUERY, m);
        return (0);
}

int
mm_answer_pam_respond(struct ssh *ssh, int sock, struct sshbuf *m)
{
        char **resp;
        u_int i, num;
        int r, ret;

        debug3("%s", __func__);
        if (sshpam_ctxt == NULL)
                fatal("%s: no context", __func__);
        sshpam_authok = NULL;
        if ((r = sshbuf_get_u32(m, &num)) != 0)
                fatal("%s: buffer error: %s", __func__, ssh_err(r));
        if (num > PAM_MAX_NUM_MSG) {
                fatal_f("Too many PAM messages, got %u, expected <= %u",
                    num, (unsigned)PAM_MAX_NUM_MSG);
        }
        if (num > 0) {
                resp = xcalloc(num, sizeof(char *));
                for (i = 0; i < num; ++i) {
                        if ((r = sshbuf_get_cstring(m, &(resp[i]), NULL)) != 0)
                                fatal("%s: buffer error: %s",
                                    __func__, ssh_err(r));
                }
                ret = (sshpam_device.respond)(sshpam_ctxt, num, resp);
                for (i = 0; i < num; ++i)
                        free(resp[i]);
                free(resp);
        } else {
                ret = (sshpam_device.respond)(sshpam_ctxt, num, NULL);
        }
        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_PAM_RESPOND, m);
        auth_method = "keyboard-interactive";
        auth_submethod = "pam";
        if (ret == 0)
                sshpam_authok = sshpam_ctxt;
        return (0);
}

int
mm_answer_pam_free_ctx(struct ssh *ssh, int sock, struct sshbuf *m)
{
        int r = sshpam_authok != NULL && sshpam_authok == sshpam_ctxt;

        debug3("%s", __func__);
        if (sshpam_ctxt == NULL)
                fatal("%s: no context", __func__);
        (sshpam_device.free_ctx)(sshpam_ctxt);
        sshpam_ctxt = sshpam_authok = NULL;
        sshbuf_reset(m);
        mm_request_send(sock, MONITOR_ANS_PAM_FREE_CTX, m);
        /* Allow another attempt */
        monitor_permit(mon_dispatch, MONITOR_REQ_PAM_INIT_CTX, 1);
        auth_method = "keyboard-interactive";
        auth_submethod = "pam";
        return r;
}
#endif

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

        debug3_f("entering");
        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_fr(r, "parse");

        if (key != NULL && authctxt->valid) {
                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_accepted_algos))
                                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_accepted_algos))
                                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_f("unknown key type %u", type);
                        break;
                }
        }

        debug3_f("%s authentication%s: %s key is %s", 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_fr(r, "sshkey_to_blob");
                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_fr(r, "assemble");
        if (opts != NULL && (r = sshauthopt_serialise(opts, m, 1)) != 0)
                fatal_fr(r, "sshauthopt_serialise");
        mm_request_send(sock, MONITOR_ANS_KEYALLOWED, m);

        if (!allowed)
                sshauthopt_free(opts);

        return (0);
}

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

        if ((b = sshbuf_from(data, datalen)) == NULL)
                fatal_f("sshbuf_from");

        if (ssh->compat & 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_fr(r, "consume");
        } else {
                if ((r = sshbuf_get_string_direct(b, &p, &len)) != 0)
                        fatal_fr(r, "parse sessionid");
                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_fr(r, "parse type");
        if (type != SSH2_MSG_USERAUTH_REQUEST)
                fail++;
        if ((r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
                fatal_fr(r, "parse userstyle");
        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_fr(r, "parse method");
        if (strcmp("publickey", cp) != 0) {
                if (strcmp("publickey-hostbound-v00@openssh.com", cp) == 0)
                        hostbound = 1;
                else
                        fail++;
        }
        free(cp);
        if ((r = sshbuf_get_u8(b, &type)) != 0)
                fatal_fr(r, "parse pktype");
        if (type == 0)
                fail++;
        if ((r = sshbuf_skip_string(b)) != 0 || /* pkalg */
            (r = sshbuf_skip_string(b)) != 0 || /* pkblob */
            (hostbound && (r = sshkey_froms(b, &hostkey)) != 0))
                fatal_fr(r, "parse pk");
        if (sshbuf_len(b) != 0)
                fail++;
        sshbuf_free(b);
        if (hostkey != NULL) {
                /*
                 * Ensure this is actually one of our hostkeys; unfortunately
                 * can't check ssh->kex->initial_hostkey directly at this point
                 * as packet state has not yet been exported to monitor.
                 */
                if (get_hostkey_index(hostkey, 1, ssh) == -1)
                        fatal_f("hostbound hostkey does not match");
                sshkey_free(hostkey);
        }
        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_f("sshbuf_new");
        if ((r = sshbuf_get_string_direct(b, &p, &len)) != 0)
                fatal_fr(r, "parse sessionid");

        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_fr(r, "parse type");
        if (type != SSH2_MSG_USERAUTH_REQUEST)
                fail++;
        if ((r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
                fatal_fr(r, "parse userstyle");
        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_fr(r, "parse method");
        if (strcmp(cp, "hostbased") != 0)
                fail++;
        free(cp);
        if ((r = sshbuf_skip_string(b)) != 0 || /* pkalg */
            (r = sshbuf_skip_string(b)) != 0)   /* pkblob */
                fatal_fr(r, "parse pk");

        /* verify client host, strip trailing dot if necessary */
        if ((r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
                fatal_fr(r, "parse host");
        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_fr(r, "parse ruser");
        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_fr(r, "parse");

        if (hostbased_cuser == NULL || hostbased_chost == NULL ||
          !monitor_allowed_key(blob, bloblen))
                fatal_f("bad key, not previously allowed");

        /* 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_fr(r, "parse key");

        switch (key_blobtype) {
        case MM_USERKEY:
                valid_data = monitor_valid_userblob(ssh, 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_f("bad %s signature data blob",
                    key_blobtype == MM_USERKEY ? "userkey" :
                    (key_blobtype == MM_HOSTKEY ? "hostkey" : "unknown"));

        if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
            SSH_FP_DEFAULT)) == NULL)
                fatal_f("sshkey_fingerprint failed");

        ret = sshkey_verify(key, signature, signaturelen, data, datalen,
            sigalg, ssh->compat, &sig_details);
        debug3_f("%s %s signature using %s %s%s%s", auth_method,
            sshkey_type(key), sigalg == NULL ? "default" : sigalg,
            (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_fr(r, "assemble");
        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_fr(r, "assemble sk");
        }
        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_f("session %d pid %ld", s->self, (long)s->pid);
        if (s->ttyfd != -1) {
                debug3_f("tty %s ptyfd %d", 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_f("entering");

        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_fr(r, "assemble");

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

        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_fr(r, "assemble loginmsg");
        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_f("send fds failed");

        /* make sure nothing uses fd 0 */
        if ((fd0 = open(_PATH_DEVNULL, O_RDONLY)) == -1)
                fatal_f("open(/dev/null): %s", strerror(errno));
        if (fd0 != 0)
                error_f("fd0 %d != 0", 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_f("tty %s ptyfd %d", s->tty, s->ttyfd);

        return (0);

 error:
        if (s != NULL)
                mm_session_close(s);
        if ((r = sshbuf_put_u32(m, 0)) != 0)
                fatal_fr(r, "assemble 0");
        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_f("entering");

        if ((r = sshbuf_get_cstring(m, &tty, NULL)) != 0)
                fatal_fr(r, "parse tty");
        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_f("tearing down sessions");

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

#ifdef USE_PAM
        if (options.use_pam)
                sshpam_cleanup();
#endif

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

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

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

#ifdef SSH_AUDIT_EVENTS
/* Report that an audit event occurred */
int
mm_answer_audit_event(struct ssh *ssh, int socket, struct sshbuf *m)
{
        u_int n;
        ssh_audit_event_t event;
        int r;

        debug3("%s entering", __func__);

        if ((r = sshbuf_get_u32(m, &n)) != 0)
                fatal("%s: buffer error: %s", __func__, ssh_err(r));
        event = (ssh_audit_event_t)n;
        switch (event) {
        case SSH_AUTH_FAIL_PUBKEY:
        case SSH_AUTH_FAIL_HOSTBASED:
        case SSH_AUTH_FAIL_GSSAPI:
        case SSH_LOGIN_EXCEED_MAXTRIES:
        case SSH_LOGIN_ROOT_DENIED:
        case SSH_CONNECTION_CLOSE:
        case SSH_INVALID_USER:
                audit_event(ssh, event);
                break;
        default:
                fatal("Audit event type %d not permitted", event);
        }

        return (0);
}

int
mm_answer_audit_command(struct ssh *ssh, int socket, struct sshbuf *m)
{
        char *cmd;
        int r;

        debug3("%s entering", __func__);
        if ((r = sshbuf_get_cstring(m, &cmd, NULL)) != 0)
                fatal("%s: buffer error: %s", __func__, ssh_err(r));
        /* sanity check command, if so how? */
        audit_run_command(cmd);
        free(cmd);
        return (0);
}
#endif /* SSH_AUDIT_EVENTS */

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_f("packet_set_state");
        if ((r = ssh_packet_set_state(ssh, child_state)) != 0)
                fatal_fr(r, "packet_set_state");
        sshbuf_free(child_state);
        child_state = NULL;
        if ((kex = ssh->kex) == NULL)
                fatal_f("internal error: ssh->kex == NULL");
        if (session_id2_len != sshbuf_len(ssh->kex->session_id)) {
                fatal_f("incorrect session id length %zu (expected %u)",
                    sshbuf_len(ssh->kex->session_id), session_id2_len);
        }
        if (memcmp(sshbuf_ptr(ssh->kex->session_id), session_id2,
            session_id2_len) != 0)
                fatal_f("session ID mismatch");
        /* 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;
# ifdef OPENSSL_HAS_ECC
        kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
# endif
#endif /* WITH_OPENSSL */
        kex->kex[KEX_C25519_SHA256] = kex_gen_server;
        kex->kex[KEX_KEM_SNTRUP761X25519_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_f("Waiting for new keys");

        if ((child_state = sshbuf_new()) == NULL)
                fatal_f("sshbuf_new failed");
        mm_request_receive_expect(pmonitor->m_sendfd, MONITOR_REQ_KEYEXPORT,
            child_state);
        debug3_f("GOT new keys");
}


/* 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_f("socketpair: %s", 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_f("pipe: %s", 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_f("GSSAPI authentication not enabled");

        if ((r = sshbuf_get_string(m, &p, &len)) != 0)
                fatal_fr(r, "parse");
        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_fr(r, "assemble");

        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_f("GSSAPI authentication not enabled");

        if ((r = ssh_gssapi_get_buffer_desc(m, &in)) != 0)
                fatal_fr(r, "ssh_gssapi_get_buffer_desc");
        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_fr(r, "assemble");
        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_f("GSSAPI authentication not enabled");

        if ((r = ssh_gssapi_get_buffer_desc(m, &gssbuf)) != 0 ||
            (r = ssh_gssapi_get_buffer_desc(m, &mic)) != 0)
                fatal_fr(r, "ssh_gssapi_get_buffer_desc");

        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_fr(r, "assemble");

        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_f("GSSAPI authentication not enabled");

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

        sshbuf_reset(m);
        if ((r = sshbuf_put_u32(m, authenticated)) != 0)
                fatal_fr(r, "assemble");

        debug3_f("sending result %d", 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 */