+}
+
+/* Destroy the host and server keys. They will no longer be needed. */
+void
+destroy_sensitive_data(void)
+{
+ int i;
+
+ if (sensitive_data.server_key) {
+ key_free(sensitive_data.server_key);
+ sensitive_data.server_key = NULL;
+ }
+ 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;
+ }
+ }
+ sensitive_data.ssh1_host_key = NULL;
+ 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 rnd[256];
+ gid_t gidset[1];
+ struct passwd *pw;
+ int i;
+
+ /* Enable challenge-response authentication for privilege separation */
+ privsep_challenge_enable();
+
+ for (i = 0; i < 256; i++)
+ rnd[i] = arc4random();
+ RAND_seed(rnd, sizeof(rnd));
+
+ /* Demote the private keys to public keys. */
+ demote_sensitive_data();
+
+ if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
+ fatal("Privilege separation user %s does not exist",
+ 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);
+#if 0
+ /* XXX not ready, to heavy after chroot */
+ do_setusercontext(pw);
+#else
+ gidset[0] = pw->pw_gid;
+ if (setgroups(1, gidset) < 0)
+ fatal("setgroups: %.100s", strerror(errno));
+ permanently_set_uid(pw);
+#endif
+}
+
+static Authctxt *
+privsep_preauth(void)
+{
+ Authctxt *authctxt = NULL;
+ int status;
+ pid_t pid;
+
+ /* Set up unprivileged child process to deal with network data */
+ pmonitor = monitor_init();
+ /* Store a pointer to the kex for later rekeying */
+ pmonitor->m_pkex = &xxx_kex;
+
+ pid = fork();
+ if (pid == -1) {
+ fatal("fork of unprivileged child failed");
+ } else if (pid != 0) {
+ fatal_remove_cleanup((void (*) (void *)) packet_close, NULL);
+
+ debug2("Network child is on pid %ld", (long)pid);
+
+ close(pmonitor->m_recvfd);
+ authctxt = monitor_child_preauth(pmonitor);
+ close(pmonitor->m_sendfd);
+
+ /* Sync memory */
+ monitor_sync(pmonitor);
+
+ /* Wait for the child's exit status */
+ while (waitpid(pid, &status, 0) < 0)
+ if (errno != EINTR)
+ break;
+
+ /* Reinstall, since the child has finished */
+ fatal_add_cleanup((void (*) (void *)) packet_close, NULL);
+
+ return (authctxt);
+ } else {
+ /* child */
+
+ close(pmonitor->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;
+
+#ifdef DISABLE_FD_PASSING
+ if (1) {
+#else
+ if (authctxt->pw->pw_uid == 0 || options.use_login) {
+#endif
+ /* File descriptor passing is broken or root login */
+ monitor_apply_keystate(pmonitor);
+ use_privsep = 0;
+ return;
+ }
+
+ /* Authentication complete */
+ alarm(0);
+ if (startup_pipe != -1) {
+ close(startup_pipe);
+ startup_pipe = -1;
+ }
+
+ /* New socket pair */
+ monitor_reinit(pmonitor);
+
+ pmonitor->m_pid = fork();
+ if (pmonitor->m_pid == -1)
+ fatal("fork of unprivileged child failed");
+ else if (pmonitor->m_pid != 0) {
+ fatal_remove_cleanup((void (*) (void *)) packet_close, NULL);
+
+ debug2("User child is on pid %ld", (long)pmonitor->m_pid);
+ close(pmonitor->m_recvfd);
+ monitor_child_postauth(pmonitor);
+
+ /* NEVERREACHED */
+ exit(0);
+ }
+
+ close(pmonitor->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(pmonitor);
+}
+
+static char *
+list_hostkey_types(void)
+{
+ Buffer b;
+ char *p;
+ int 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) {
+ case KEY_RSA:
+ case KEY_DSA:
+ if (buffer_len(&b) > 0)
+ buffer_append(&b, ",", 1);
+ p = key_ssh_name(key);
+ buffer_append(&b, p, strlen(p));
+ break;
+ }
+ }
+ buffer_append(&b, "\0", 1);
+ p = xstrdup(buffer_ptr(&b));
+ buffer_free(&b);
+ debug("list_hostkey_types: %s", p);
+ return p;
+}
+
+Key *
+get_hostkey_by_type(int type)
+{
+ int 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;
+ }
+ 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
+ * of (max_startups_rate/100). the probability increases linearly until
+ * all connections are dropped for startups > max_startups
+ */
+static int
+drop_connection(int startups)
+{
+ double p, r;
+
+ if (startups < options.max_startups_begin)
+ return 0;
+ if (startups >= options.max_startups)
+ return 1;
+ if (options.max_startups_rate == 100)
+ return 1;
+
+ p = 100 - options.max_startups_rate;
+ p *= startups - options.max_startups_begin;
+ p /= (double) (options.max_startups - options.max_startups_begin);
+ p += options.max_startups_rate;
+ p /= 100.0;
+ r = arc4random() / (double) UINT_MAX;
+
+ debug("drop_connection: p %g, r %g", p, r);
+ return (r < p) ? 1 : 0;
+}
+
+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);