]> andersk Git - openssh.git/blobdiff - sshd.c
- stevesk@cvs.openbsd.org 2002/03/29 19:18:33
[openssh.git] / sshd.c
diff --git a/sshd.c b/sshd.c
index 71a5c2c2e98c6dcc530ec69e1ba014511e8d31de..541e9932ea8e3a46e90fcd4f55b1d880c7eb1448 100644 (file)
--- a/sshd.c
+++ b/sshd.c
  * called by a name other than "ssh" or "Secure Shell".
  *
  * SSH2 implementation:
+ * Privilege Separation:
  *
- * Copyright (c) 2000 Markus Friedl.  All rights reserved.
+ * Copyright (c) 2000, 2001, 2002 Markus Friedl.  All rights reserved.
+ * Copyright (c) 2002 Niels Provos.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: sshd.c,v 1.209 2001/11/10 13:19:45 markus Exp $");
+RCSID("$OpenBSD: sshd.c,v 1.238 2002/03/23 20:57:26 stevesk Exp $");
 
 #include <openssl/dh.h>
 #include <openssl/bn.h>
-#include <openssl/hmac.h>
+#include <openssl/md5.h>
+#include <openssl/rand.h>
 
 #include "ssh.h"
 #include "ssh1.h"
@@ -72,6 +75,11 @@ RCSID("$OpenBSD: sshd.c,v 1.209 2001/11/10 13:19:45 markus Exp $");
 #include "misc.h"
 #include "dispatch.h"
 #include "channels.h"
+#include "session.h"
+#include "monitor_mm.h"
+#include "monitor.h"
+#include "monitor_wrap.h"
+#include "monitor_fdpass.h"
 
 #ifdef LIBWRAP
 #include <tcpd.h>
@@ -169,11 +177,11 @@ struct {
  * Flag indicating whether the RSA server key needs to be regenerated.
  * Is set in the SIGALRM handler and cleared when the key is regenerated.
  */
-int key_do_regen = 0;
+static volatile sig_atomic_t key_do_regen = 0;
 
 /* This is set to true when a signal is received. */
-int received_sighup = 0;
-int received_sigterm = 0;
+static volatile sig_atomic_t received_sighup = 0;
+static volatile sig_atomic_t received_sigterm = 0;
 
 /* session identifier, used by RSA-auth */
 u_char session_id[16];
@@ -185,8 +193,17 @@ int session_id2_len = 0;
 /* record remote hostname or ip */
 u_int utmp_len = MAXHOSTNAMELEN;
 
+/* options.max_startup sized array of fd ints */
+int *startup_pipes = NULL;
+int startup_pipe;              /* in child */
+
+/* variables used for privilege separation */
+extern struct monitor *monitor;
+extern int use_privsep;
+
 /* Prototypes for various functions defined later in this file. */
 void destroy_sensitive_data(void);
+void demote_sensitive_data(void);
 
 static void do_ssh1_kex(void);
 static void do_ssh2_kex(void);
@@ -203,6 +220,16 @@ close_listen_socks(void)
        num_listen_socks = -1;
 }
 
+static void
+close_startup_pipes(void)
+{
+       int i;
+       if (startup_pipes)
+               for (i = 0; i < options.max_startups; i++)
+                       if (startup_pipes[i] != -1)
+                               close(startup_pipes[i]);
+}
+
 /*
  * Signal handler for SIGHUP.  Sshd execs itself when it receives SIGHUP;
  * the effect is to reread the configuration file (and to regenerate
@@ -211,8 +238,11 @@ close_listen_socks(void)
 static void
 sighup_handler(int sig)
 {
+       int save_errno = errno;
+
        received_sighup = 1;
        signal(SIGHUP, sighup_handler);
+       errno = save_errno;
 }
 
 /*
@@ -224,6 +254,7 @@ sighup_restart(void)
 {
        log("Received SIGHUP; restarting.");
        close_listen_socks();
+       close_startup_pipes();
        execv(saved_argv[0], saved_argv);
        log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
        exit(1);
@@ -381,7 +412,7 @@ sshd_exchange_identification(int sock_in, int sock_out)
                fatal_cleanup();
        }
        debug("Client protocol version %d.%d; client software version %.100s",
-             remote_major, remote_minor, remote_version);
+           remote_major, remote_minor, remote_version);
 
        compat_datafellows(remote_version);
 
@@ -392,7 +423,7 @@ sshd_exchange_identification(int sock_in, int sock_out)
        }
 
        mismatch = 0;
-       switch(remote_major) {
+       switch (remote_major) {
        case 1:
                if (remote_minor == 99) {
                        if (options.protocol & SSH_PROTO_2)
@@ -449,7 +480,7 @@ destroy_sensitive_data(void)
                key_free(sensitive_data.server_key);
                sensitive_data.server_key = NULL;
        }
-       for(i = 0; i < options.num_host_key_files; i++) {
+       for (i = 0; i < options.num_host_key_files; i++) {
                if (sensitive_data.host_keys[i]) {
                        key_free(sensitive_data.host_keys[i]);
                        sensitive_data.host_keys[i] = NULL;
@@ -459,36 +490,192 @@ destroy_sensitive_data(void)
        memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
 }
 
+/* Demote private to public keys for network child */
+void
+demote_sensitive_data(void)
+{
+       Key *tmp;
+       int i;
+
+       if (sensitive_data.server_key) {
+               tmp = key_demote(sensitive_data.server_key);
+               key_free(sensitive_data.server_key);
+               sensitive_data.server_key = tmp;
+       }
+
+       for (i = 0; i < options.num_host_key_files; i++) {
+               if (sensitive_data.host_keys[i]) {
+                       tmp = key_demote(sensitive_data.host_keys[i]);
+                       key_free(sensitive_data.host_keys[i]);
+                       sensitive_data.host_keys[i] = tmp;
+                       if (tmp->type == KEY_RSA1)
+                               sensitive_data.ssh1_host_key = tmp;
+               }
+       }
+
+       /* We do not clear ssh1_host key and cookie.  XXX - Okay Niels? */
+}
+
+static void
+privsep_preauth_child(void)
+{
+       u_int32_t rand[256];
+       int i;
+       struct passwd *pw;
+
+       /* Enable challenge-response authentication for privilege separation */
+       privsep_challenge_enable();
+
+       for (i = 0; i < 256; i++)
+               rand[i] = arc4random();
+       RAND_seed(rand, sizeof(rand));
+
+       /* Demote the private keys to public keys. */
+       demote_sensitive_data();
+
+       if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
+               fatal("%s: no user", SSH_PRIVSEP_USER);
+       memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
+       endpwent();
+
+       /* Change our root directory*/
+       if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
+               fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
+                   strerror(errno));
+       if (chdir("/") == -1)
+               fatal("chdir(\"/\"): %s", strerror(errno));
+
+       /* Drop our privileges */
+       debug3("privsep user:group %u:%u", (u_int)pw->pw_uid,
+           (u_int)pw->pw_gid);
+       do_setusercontext(pw);
+}
+
+static Authctxt*
+privsep_preauth(void)
+{
+       Authctxt *authctxt = NULL;
+       int status;
+       pid_t pid;
+
+       /* Set up unprivileged child process to deal with network data */
+       monitor = monitor_init();
+       /* Store a pointer to the kex for later rekeying */
+       monitor->m_pkex = &xxx_kex;
+
+       pid = fork();
+       if (pid == -1) {
+               fatal("fork of unprivileged child failed");
+       } else if (pid != 0) {
+               debug2("Network child is on pid %d", pid);
+
+               close(monitor->m_recvfd);
+               authctxt = monitor_child_preauth(monitor);
+               close(monitor->m_sendfd);
+
+               /* Sync memory */
+               monitor_sync(monitor);
+
+               /* Wait for the child's exit status */
+               waitpid(pid, &status, 0);
+
+               return (authctxt);
+       } else {
+               /* child */
+
+               close(monitor->m_sendfd);
+
+               /* Demote the child */
+               if (getuid() == 0 || geteuid() == 0)
+                       privsep_preauth_child();
+               setproctitle("%s", "[net]");
+       }
+       return (NULL);
+}
+
+static void
+privsep_postauth(Authctxt *authctxt)
+{
+       extern Authctxt *x_authctxt;
+
+       /* XXX - Remote port forwarding */
+       x_authctxt = authctxt;
+
+       if (authctxt->pw->pw_uid == 0 || options.use_login) {
+               /* File descriptor passing is broken or root login */
+               monitor_apply_keystate(monitor);
+               use_privsep = 0;
+               return;
+       }
+
+       /* Authentication complete */
+       alarm(0);
+       if (startup_pipe != -1) {
+               close(startup_pipe);
+               startup_pipe = -1;
+       }
+
+       /* New socket pair */
+       monitor_reinit(monitor);
+
+       monitor->m_pid = fork();
+       if (monitor->m_pid == -1)
+               fatal("fork of unprivileged child failed");
+       else if (monitor->m_pid != 0) {
+               debug2("User child is on pid %d", monitor->m_pid);
+               close(monitor->m_recvfd);
+               monitor_child_postauth(monitor);
+
+               /* NEVERREACHED */
+               exit(0);
+       }
+
+       close(monitor->m_sendfd);
+
+       /* Demote the private keys to public keys. */
+       demote_sensitive_data();
+
+       /* Drop privileges */
+       do_setusercontext(authctxt->pw);
+
+       /* It is safe now to apply the key state */
+       monitor_apply_keystate(monitor);
+}
+
 static char *
 list_hostkey_types(void)
 {
-       static char buf[1024];
+       Buffer b;
+       char *p;
        int i;
-       buf[0] = '\0';
-       for(i = 0; i < options.num_host_key_files; i++) {
+
+       buffer_init(&b);
+       for (i = 0; i < options.num_host_key_files; i++) {
                Key *key = sensitive_data.host_keys[i];
                if (key == NULL)
                        continue;
-               switch(key->type) {
+               switch (key->type) {
                case KEY_RSA:
                case KEY_DSA:
-                       strlcat(buf, key_ssh_name(key), sizeof buf);
-                       strlcat(buf, ",", sizeof buf);
+                       if (buffer_len(&b) > 0)
+                               buffer_append(&b, ",", 1);
+                       p = key_ssh_name(key);
+                       buffer_append(&b, p, strlen(p));
                        break;
                }
        }
-       i = strlen(buf);
-       if (i > 0 && buf[i-1] == ',')
-               buf[i-1] = '\0';
-       debug("list_hostkey_types: %s", buf);
-       return buf;
+       buffer_append(&b, "\0", 1);
+       p = xstrdup(buffer_ptr(&b));
+       buffer_free(&b);
+       debug("list_hostkey_types: %s", p);
+       return p;
 }
 
-static Key *
+Key *
 get_hostkey_by_type(int type)
 {
        int i;
-       for(i = 0; i < options.num_host_key_files; i++) {
+       for (i = 0; i < options.num_host_key_files; i++) {
                Key *key = sensitive_data.host_keys[i];
                if (key != NULL && key->type == type)
                        return key;
@@ -496,6 +683,25 @@ get_hostkey_by_type(int type)
        return NULL;
 }
 
+Key *
+get_hostkey_by_index(int ind)
+{
+       if (ind < 0 || ind >= options.num_host_key_files)
+               return (NULL);
+       return (sensitive_data.host_keys[ind]);
+}
+
+int
+get_hostkey_index(Key *key)
+{
+       int i;
+       for (i = 0; i < options.num_host_key_files; i++) {
+               if (key == sensitive_data.host_keys[i])
+                       return (i);
+       }
+       return (-1);
+}
+
 /*
  * returns 1 if connection should be dropped, 0 otherwise.
  * dropping starts at connection #max_startups_begin with a probability
@@ -525,8 +731,30 @@ drop_connection(int startups)
        return (r < p) ? 1 : 0;
 }
 
-int *startup_pipes = NULL;     /* options.max_startup sized array of fd ints */
-int startup_pipe;              /* in child */
+static void
+usage(void)
+{
+       fprintf(stderr, "sshd version %s\n", SSH_VERSION);
+       fprintf(stderr, "Usage: %s [options]\n", __progname);
+       fprintf(stderr, "Options:\n");
+       fprintf(stderr, "  -f file    Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
+       fprintf(stderr, "  -d         Debugging mode (multiple -d means more debugging)\n");
+       fprintf(stderr, "  -i         Started from inetd\n");
+       fprintf(stderr, "  -D         Do not fork into daemon mode\n");
+       fprintf(stderr, "  -t         Only test configuration file and keys\n");
+       fprintf(stderr, "  -q         Quiet (no logging)\n");
+       fprintf(stderr, "  -p port    Listen on the specified port (default: 22)\n");
+       fprintf(stderr, "  -k seconds Regenerate server key every this many seconds (default: 3600)\n");
+       fprintf(stderr, "  -g seconds Grace period for authentication (default: 600)\n");
+       fprintf(stderr, "  -b bits    Size of server RSA key (default: 768 bits)\n");
+       fprintf(stderr, "  -h file    File from which to read host key (default: %s)\n",
+           _PATH_HOST_KEY_FILE);
+       fprintf(stderr, "  -u len     Maximum hostname length for utmp recording\n");
+       fprintf(stderr, "  -4         Use IPv4 only\n");
+       fprintf(stderr, "  -6         Use IPv6 only\n");
+       fprintf(stderr, "  -o option  Process the option as if it was read from a configuration file.\n");
+       exit(1);
+}
 
 /*
  * Main program for the daemon.
@@ -550,6 +778,7 @@ main(int ac, char **av)
        int listen_sock, maxfd;
        int startup_p[2];
        int startups = 0;
+       Authctxt *authctxt;
        Key *key;
        int ret, key_used = 0;
 
@@ -564,7 +793,7 @@ main(int ac, char **av)
        initialize_server_options(&options);
 
        /* Parse command-line arguments. */
-       while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:dDeiqtQ46")) != -1) {
+       while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:o:dDeiqtQ46")) != -1) {
                switch (opt) {
                case '4':
                        IPv4or6 = AF_INET;
@@ -646,27 +875,15 @@ main(int ac, char **av)
                case 'u':
                        utmp_len = atoi(optarg);
                        break;
+               case 'o':
+                       if (process_server_config_line(&options, optarg,
+                           "command-line", 0) != 0)
+                               exit(1);
+                       break;
                case '?':
                default:
-                       fprintf(stderr, "sshd version %s\n", SSH_VERSION);
-                       fprintf(stderr, "Usage: %s [options]\n", __progname);
-                       fprintf(stderr, "Options:\n");
-                       fprintf(stderr, "  -f file    Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
-                       fprintf(stderr, "  -d         Debugging mode (multiple -d means more debugging)\n");
-                       fprintf(stderr, "  -i         Started from inetd\n");
-                       fprintf(stderr, "  -D         Do not fork into daemon mode\n");
-                       fprintf(stderr, "  -t         Only test configuration file and keys\n");
-                       fprintf(stderr, "  -q         Quiet (no logging)\n");
-                       fprintf(stderr, "  -p port    Listen on the specified port (default: 22)\n");
-                       fprintf(stderr, "  -k seconds Regenerate server key every this many seconds (default: 3600)\n");
-                       fprintf(stderr, "  -g seconds Grace period for authentication (default: 600)\n");
-                       fprintf(stderr, "  -b bits    Size of server RSA key (default: 768 bits)\n");
-                       fprintf(stderr, "  -h file    File from which to read host key (default: %s)\n",
-                           _PATH_HOST_KEY_FILE);
-                       fprintf(stderr, "  -u len     Maximum hostname length for utmp recording\n");
-                       fprintf(stderr, "  -4         Use IPv4 only\n");
-                       fprintf(stderr, "  -6         Use IPv6 only\n");
-                       exit(1);
+                       usage();
+                       break;
                }
        }
        SSLeay_add_all_algorithms();
@@ -677,8 +894,10 @@ main(int ac, char **av)
         * key (unless started from inetd)
         */
        log_init(__progname,
-           options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
-           options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
+           options.log_level == SYSLOG_LEVEL_NOT_SET ?
+           SYSLOG_LEVEL_INFO : options.log_level,
+           options.log_facility == SYSLOG_FACILITY_NOT_SET ?
+           SYSLOG_FACILITY_AUTH : options.log_facility,
            !inetd_flag);
 
 #ifdef _CRAY
@@ -706,14 +925,14 @@ main(int ac, char **av)
 
        /* load private host keys */
        sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
-       for(i = 0; i < options.num_host_key_files; i++)
+       for (i = 0; i < options.num_host_key_files; i++)
                sensitive_data.host_keys[i] = NULL;
        sensitive_data.server_key = NULL;
        sensitive_data.ssh1_host_key = NULL;
        sensitive_data.have_ssh1_key = 0;
        sensitive_data.have_ssh2_key = 0;
 
-       for(i = 0; i < options.num_host_key_files; i++) {
+       for (i = 0; i < options.num_host_key_files; i++) {
                key = key_load_private(options.host_key_files[i], "", NULL);
                sensitive_data.host_keys[i] = key;
                if (key == NULL) {
@@ -722,7 +941,7 @@ main(int ac, char **av)
                        sensitive_data.host_keys[i] = NULL;
                        continue;
                }
-               switch(key->type){
+               switch (key->type) {
                case KEY_RSA1:
                        sensitive_data.ssh1_host_key = key;
                        sensitive_data.have_ssh1_key = 1;
@@ -814,7 +1033,7 @@ main(int ac, char **av)
        /* Chdir to the root directory so that the current disk can be
           unmounted if desired. */
        chdir("/");
-       
+
        /* ignore SIGPIPE */
        signal(SIGPIPE, SIG_IGN);
 
@@ -866,11 +1085,11 @@ main(int ac, char **av)
                         * close.
                         */
                        setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
-                           (void *) &on, sizeof(on));
+                           &on, sizeof(on));
                        linger.l_onoff = 1;
                        linger.l_linger = 5;
                        setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
-                           (void *) &linger, sizeof(linger));
+                           &linger, sizeof(linger));
 
                        debug("Bind to port %s on %s.", strport, ntop);
 
@@ -963,7 +1182,7 @@ main(int ac, char **av)
                                error("select: %.100s", strerror(errno));
                        if (received_sigterm) {
                                log("Received signal %d; terminating.",
-                                   received_sigterm);
+                                   (int) received_sigterm);
                                close_listen_socks();
                                unlink(options.pid_file);
                                exit(255);
@@ -1002,6 +1221,7 @@ main(int ac, char **av)
                                }
                                if (fcntl(newsock, F_SETFL, 0) < 0) {
                                        error("newsock del O_NONBLOCK: %s", strerror(errno));
+                                       close(newsock);
                                        continue;
                                }
                                if (drop_connection(startups) == 1) {
@@ -1055,9 +1275,7 @@ main(int ac, char **av)
                                                 * the connection.
                                                 */
                                                startup_pipe = startup_p[1];
-                                               for (j = 0; j < options.max_startups; j++)
-                                                       if (startup_pipes[j] != -1)
-                                                               close(startup_pipes[j]);
+                                               close_startup_pipes();
                                                close_listen_socks();
                                                sock_in = newsock;
                                                sock_out = newsock;
@@ -1117,11 +1335,11 @@ main(int ac, char **av)
        /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
        linger.l_onoff = 1;
        linger.l_linger = 5;
-       setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
+       setsockopt(sock_in, SOL_SOCKET, SO_LINGER, &linger, sizeof(linger));
 
        /* Set keepalives if requested. */
        if (options.keepalives &&
-           setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
+           setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on,
            sizeof(on)) < 0)
                error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
 
@@ -1174,8 +1392,9 @@ main(int ac, char **av)
         * machine, he can connect from any port.  So do not use these
         * authentication methods from machines that you do not trust.
         */
-       if (remote_port >= IPPORT_RESERVED ||
-           remote_port < IPPORT_RESERVED / 2) {
+       if (options.rhosts_authentication &&
+           (remote_port >= IPPORT_RESERVED ||
+           remote_port < IPPORT_RESERVED / 2)) {
                debug("Rhosts Authentication disabled, "
                    "originating port %d not trusted.", remote_port);
                options.rhosts_authentication = 0;
@@ -1197,15 +1416,43 @@ main(int ac, char **av)
 
        packet_set_nonblocking();
 
+       if (use_privsep)
+               if ((authctxt = privsep_preauth()) != NULL)
+                       goto authenticated;
+
        /* perform the key exchange */
        /* authenticate user and start session */
        if (compat20) {
                do_ssh2_kex();
-               do_authentication2();
+               authctxt = do_authentication2();
        } else {
                do_ssh1_kex();
-               do_authentication();
+               authctxt = do_authentication();
        }
+       /*
+        * If we use privilege separation, the unprivileged child transfers
+        * the current keystate and exits
+        */
+       if (use_privsep) {
+               mm_send_keystate(monitor);
+               exit(0);
+       }
+
+ authenticated:
+       /*
+        * In privilege separation, we fork another child and prepare
+        * file descriptor passing.
+        */
+       if (use_privsep) {
+               privsep_postauth(authctxt);
+               /* the monitor process [priv] will not return */
+               if (!compat20)
+                       destroy_sensitive_data();
+       }
+
+       /* Perform session preparation. */
+       do_authenticated(authctxt);
+
        /* The connection has been terminated. */
        verbose("Closing connection to %.100s", remote_ip);
 
@@ -1214,9 +1461,57 @@ main(int ac, char **av)
 #endif /* USE_PAM */
 
        packet_close();
+
+       if (use_privsep)
+               mm_terminate();
+
        exit(0);
 }
 
+/*
+ * Decrypt session_key_int using our private server key and private host key
+ * (key with larger modulus first).
+ */
+int
+ssh1_session_key(BIGNUM *session_key_int)
+{
+       int rsafail = 0;
+
+       if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
+               /* Server key has bigger modulus. */
+               if (BN_num_bits(sensitive_data.server_key->rsa->n) <
+                   BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
+                       fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
+                           get_remote_ipaddr(),
+                           BN_num_bits(sensitive_data.server_key->rsa->n),
+                           BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
+                           SSH_KEY_BITS_RESERVED);
+               }
+               if (rsa_private_decrypt(session_key_int, session_key_int,
+                   sensitive_data.server_key->rsa) <= 0)
+                       rsafail++;
+               if (rsa_private_decrypt(session_key_int, session_key_int,
+                   sensitive_data.ssh1_host_key->rsa) <= 0)
+                       rsafail++;
+       } else {
+               /* Host key has bigger modulus (or they are equal). */
+               if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
+                   BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
+                       fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
+                           get_remote_ipaddr(),
+                           BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
+                           BN_num_bits(sensitive_data.server_key->rsa->n),
+                           SSH_KEY_BITS_RESERVED);
+               }
+               if (rsa_private_decrypt(session_key_int, session_key_int,
+                   sensitive_data.ssh1_host_key->rsa) < 0)
+                       rsafail++;
+               if (rsa_private_decrypt(session_key_int, session_key_int,
+                   sensitive_data.server_key->rsa) < 0)
+                       rsafail++;
+       }
+       return (rsafail);
+}
 /*
  * SSH1 key exchange
  */
@@ -1224,7 +1519,6 @@ static void
 do_ssh1_kex(void)
 {
        int i, len;
-       int plen, slen;
        int rsafail = 0;
        BIGNUM *session_key_int;
        u_char session_key[SSH_SESSION_KEY_LENGTH];
@@ -1308,7 +1602,7 @@ do_ssh1_kex(void)
            BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
 
        /* Read clients reply (cipher type and session key). */
-       packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
+       packet_read_expect(SSH_CMSG_SESSION_KEY);
 
        /* Get cipher type and check whether we accept this. */
        cipher_type = packet_get_char();
@@ -1325,51 +1619,17 @@ do_ssh1_kex(void)
        debug("Encryption type: %.200s", cipher_name(cipher_type));
 
        /* Get the encrypted integer. */
-       session_key_int = BN_new();
-       packet_get_bignum(session_key_int, &slen);
+       if ((session_key_int = BN_new()) == NULL)
+               fatal("do_ssh1_kex: BN_new failed");
+       packet_get_bignum(session_key_int);
 
        protocol_flags = packet_get_int();
        packet_set_protocol_flags(protocol_flags);
+       packet_check_eom();
 
-       packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
+       /* Decrypt session_key_int using host/server keys */
+       rsafail = PRIVSEP(ssh1_session_key(session_key_int));
 
-       /*
-        * Decrypt it using our private server key and private host key (key
-        * with larger modulus first).
-        */
-       if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
-               /* Server key has bigger modulus. */
-               if (BN_num_bits(sensitive_data.server_key->rsa->n) <
-                   BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
-                       fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
-                           get_remote_ipaddr(),
-                           BN_num_bits(sensitive_data.server_key->rsa->n),
-                           BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
-                           SSH_KEY_BITS_RESERVED);
-               }
-               if (rsa_private_decrypt(session_key_int, session_key_int,
-                   sensitive_data.server_key->rsa) <= 0)
-                       rsafail++;
-               if (rsa_private_decrypt(session_key_int, session_key_int,
-                   sensitive_data.ssh1_host_key->rsa) <= 0)
-                       rsafail++;
-       } else {
-               /* Host key has bigger modulus (or they are equal). */
-               if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
-                   BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
-                       fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
-                           get_remote_ipaddr(),
-                           BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
-                           BN_num_bits(sensitive_data.server_key->rsa->n),
-                           SSH_KEY_BITS_RESERVED);
-               }
-               if (rsa_private_decrypt(session_key_int, session_key_int,
-                   sensitive_data.ssh1_host_key->rsa) < 0)
-                       rsafail++;
-               if (rsa_private_decrypt(session_key_int, session_key_int,
-                   sensitive_data.server_key->rsa) < 0)
-                       rsafail++;
-       }
        /*
         * Extract session key from the decrypted integer.  The key is in the
         * least significant 256 bits of the integer; the first byte of the
@@ -1401,7 +1661,7 @@ do_ssh1_kex(void)
        }
        if (rsafail) {
                int bytes = BN_num_bytes(session_key_int);
-               char *buf = xmalloc(bytes);
+               u_char *buf = xmalloc(bytes);
                MD5_CTX md;
 
                log("do_connection: generating a fake encryption key");
@@ -1420,9 +1680,12 @@ do_ssh1_kex(void)
                for (i = 0; i < 16; i++)
                        session_id[i] = session_key[i] ^ session_key[i + 16];
        }
-       /* Destroy the private and public keys.  They will no longer be needed. */
+       /* Destroy the private and public keys. No longer. */
        destroy_sensitive_data();
 
+       if (use_privsep)
+               mm_ssh1_session_id(session_id);
+
        /* Destroy the decrypted integer.  It is no longer needed. */
        BN_clear_free(session_key_int);
 
@@ -1469,6 +1732,7 @@ do_ssh2_kex(void)
        kex->client_version_string=client_version_string;
        kex->server_version_string=server_version_string;
        kex->load_host_key=&get_hostkey_by_type;
+       kex->host_key_index=&get_hostkey_index;
 
        xxx_kex = kex;
 
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