| /* |
| * Author: Tatu Ylonen <ylo@cs.hut.fi> |
| * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| * All rights reserved |
| * This program is the ssh daemon. It listens for connections from clients, |
| * and performs authentication, executes use commands or shell, and forwards |
| * information to/from the application to the user client over an encrypted |
| * connection. This can also handle forwarding of X11, TCP/IP, and |
| * authentication agent connections. |
| * |
| * As far as I am concerned, the code I have written for this software |
| * can be used freely for any purpose. Any derived versions of this |
| * software must be clearly marked as such, and if the derived work is |
| * incompatible with the protocol description in the RFC file, it must be |
| * called by a name other than "ssh" or "Secure Shell". |
| * |
| * SSH2 implementation: |
| * Privilege Separation: |
| * |
| * 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 |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| #include "includes.h" |
| RCSID("$OpenBSD: sshd.c,v 1.249 2002/06/23 03:30:17 deraadt Exp $"); |
| |
| #include <openssl/dh.h> |
| #include <openssl/bn.h> |
| #include <openssl/md5.h> |
| #include <openssl/rand.h> |
| #ifdef HAVE_SECUREWARE |
| #include <sys/security.h> |
| #include <prot.h> |
| #endif |
| |
| #include "ssh.h" |
| #include "ssh1.h" |
| #include "ssh2.h" |
| #include "xmalloc.h" |
| #include "rsa.h" |
| #include "sshpty.h" |
| #include "packet.h" |
| #include "mpaux.h" |
| #include "log.h" |
| #include "servconf.h" |
| #include "uidswap.h" |
| #include "compat.h" |
| #include "buffer.h" |
| #include "cipher.h" |
| #include "kex.h" |
| #include "key.h" |
| #include "dh.h" |
| #include "myproposal.h" |
| #include "authfile.h" |
| #include "pathnames.h" |
| #include "atomicio.h" |
| #include "canohost.h" |
| #include "auth.h" |
| #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> |
| #include <syslog.h> |
| int allow_severity = LOG_INFO; |
| int deny_severity = LOG_WARNING; |
| #endif /* LIBWRAP */ |
| |
| #ifndef O_NOCTTY |
| #define O_NOCTTY 0 |
| #endif |
| |
| #ifdef HAVE___PROGNAME |
| extern char *__progname; |
| #else |
| char *__progname; |
| #endif |
| |
| /* Server configuration options. */ |
| ServerOptions options; |
| |
| /* Name of the server configuration file. */ |
| char *config_file_name = _PATH_SERVER_CONFIG_FILE; |
| |
| /* |
| * Flag indicating whether IPv4 or IPv6. This can be set on the command line. |
| * Default value is AF_UNSPEC means both IPv4 and IPv6. |
| */ |
| #ifdef IPV4_DEFAULT |
| int IPv4or6 = AF_INET; |
| #else |
| int IPv4or6 = AF_UNSPEC; |
| #endif |
| |
| /* |
| * Debug mode flag. This can be set on the command line. If debug |
| * mode is enabled, extra debugging output will be sent to the system |
| * log, the daemon will not go to background, and will exit after processing |
| * the first connection. |
| */ |
| int debug_flag = 0; |
| |
| /* Flag indicating that the daemon should only test the configuration and keys. */ |
| int test_flag = 0; |
| |
| /* Flag indicating that the daemon is being started from inetd. */ |
| int inetd_flag = 0; |
| |
| /* Flag indicating that sshd should not detach and become a daemon. */ |
| int no_daemon_flag = 0; |
| |
| /* debug goes to stderr unless inetd_flag is set */ |
| int log_stderr = 0; |
| |
| /* Saved arguments to main(). */ |
| char **saved_argv; |
| int saved_argc; |
| |
| /* |
| * The sockets that the server is listening; this is used in the SIGHUP |
| * signal handler. |
| */ |
| #define MAX_LISTEN_SOCKS 16 |
| int listen_socks[MAX_LISTEN_SOCKS]; |
| int num_listen_socks = 0; |
| |
| /* |
| * the client's version string, passed by sshd2 in compat mode. if != NULL, |
| * sshd will skip the version-number exchange |
| */ |
| char *client_version_string = NULL; |
| char *server_version_string = NULL; |
| |
| /* for rekeying XXX fixme */ |
| Kex *xxx_kex; |
| |
| /* |
| * Any really sensitive data in the application is contained in this |
| * structure. The idea is that this structure could be locked into memory so |
| * that the pages do not get written into swap. However, there are some |
| * problems. The private key contains BIGNUMs, and we do not (in principle) |
| * have access to the internals of them, and locking just the structure is |
| * not very useful. Currently, memory locking is not implemented. |
| */ |
| struct { |
| Key *server_key; /* ephemeral server key */ |
| Key *ssh1_host_key; /* ssh1 host key */ |
| Key **host_keys; /* all private host keys */ |
| int have_ssh1_key; |
| int have_ssh2_key; |
| u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH]; |
| } sensitive_data; |
| |
| /* |
| * Flag indicating whether the RSA server key needs to be regenerated. |
| * Is set in the SIGALRM handler and cleared when the key is regenerated. |
| */ |
| static volatile sig_atomic_t key_do_regen = 0; |
| |
| /* This is set to true when a signal is received. */ |
| 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]; |
| |
| /* same for ssh2 */ |
| u_char *session_id2 = NULL; |
| 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 *pmonitor; |
| 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); |
| |
| /* |
| * Close all listening sockets |
| */ |
| static void |
| close_listen_socks(void) |
| { |
| int i; |
| for (i = 0; i < num_listen_socks; i++) |
| close(listen_socks[i]); |
| 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 |
| * the server key). |
| */ |
| static void |
| sighup_handler(int sig) |
| { |
| int save_errno = errno; |
| |
| received_sighup = 1; |
| signal(SIGHUP, sighup_handler); |
| errno = save_errno; |
| } |
| |
| /* |
| * Called from the main program after receiving SIGHUP. |
| * Restarts the server. |
| */ |
| static void |
| 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); |
| } |
| |
| /* |
| * Generic signal handler for terminating signals in the master daemon. |
| */ |
| static void |
| sigterm_handler(int sig) |
| { |
| received_sigterm = sig; |
| } |
| |
| /* |
| * SIGCHLD handler. This is called whenever a child dies. This will then |
| * reap any zombies left by exited children. |
| */ |
| static void |
| main_sigchld_handler(int sig) |
| { |
| pid_t pid; |
| int save_errno = errno; |
| int status; |
| |
| while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || |
| (pid < 0 && errno == EINTR)) |
| ; |
| |
| signal(SIGCHLD, main_sigchld_handler); |
| errno = save_errno; |
| } |
| |
| /* |
| * Signal handler for the alarm after the login grace period has expired. |
| */ |
| static void |
| grace_alarm_handler(int sig) |
| { |
| /* XXX no idea how fix this signal handler */ |
| |
| /* Close the connection. */ |
| packet_close(); |
| |
| /* Log error and exit. */ |
| fatal("Timeout before authentication for %s.", get_remote_ipaddr()); |
| } |
| |
| /* |
| * Signal handler for the key regeneration alarm. Note that this |
| * alarm only occurs in the daemon waiting for connections, and it does not |
| * do anything with the private key or random state before forking. |
| * Thus there should be no concurrency control/asynchronous execution |
| * problems. |
| */ |
| static void |
| generate_ephemeral_server_key(void) |
| { |
| u_int32_t rand = 0; |
| int i; |
| |
| verbose("Generating %s%d bit RSA key.", |
| sensitive_data.server_key ? "new " : "", options.server_key_bits); |
| if (sensitive_data.server_key != NULL) |
| key_free(sensitive_data.server_key); |
| sensitive_data.server_key = key_generate(KEY_RSA1, |
| options.server_key_bits); |
| verbose("RSA key generation complete."); |
| |
| for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { |
| if (i % 4 == 0) |
| rand = arc4random(); |
| sensitive_data.ssh1_cookie[i] = rand & 0xff; |
| rand >>= 8; |
| } |
| arc4random_stir(); |
| } |
| |
| static void |
| key_regeneration_alarm(int sig) |
| { |
| int save_errno = errno; |
| signal(SIGALRM, SIG_DFL); |
| errno = save_errno; |
| key_do_regen = 1; |
| } |
| |
| static void |
| sshd_exchange_identification(int sock_in, int sock_out) |
| { |
| int i, mismatch; |
| int remote_major, remote_minor; |
| int major, minor; |
| char *s; |
| char buf[256]; /* Must not be larger than remote_version. */ |
| char remote_version[256]; /* Must be at least as big as buf. */ |
| |
| if ((options.protocol & SSH_PROTO_1) && |
| (options.protocol & SSH_PROTO_2)) { |
| major = PROTOCOL_MAJOR_1; |
| minor = 99; |
| } else if (options.protocol & SSH_PROTO_2) { |
| major = PROTOCOL_MAJOR_2; |
| minor = PROTOCOL_MINOR_2; |
| } else { |
| major = PROTOCOL_MAJOR_1; |
| minor = PROTOCOL_MINOR_1; |
| } |
| snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION); |
| server_version_string = xstrdup(buf); |
| |
| if (client_version_string == NULL) { |
| /* Send our protocol version identification. */ |
| if (atomicio(write, sock_out, server_version_string, |
| strlen(server_version_string)) |
| != strlen(server_version_string)) { |
| log("Could not write ident string to %s", get_remote_ipaddr()); |
| fatal_cleanup(); |
| } |
| |
| /* Read other sides version identification. */ |
| memset(buf, 0, sizeof(buf)); |
| for (i = 0; i < sizeof(buf) - 1; i++) { |
| if (atomicio(read, sock_in, &buf[i], 1) != 1) { |
| log("Did not receive identification string from %s", |
| get_remote_ipaddr()); |
| fatal_cleanup(); |
| } |
| if (buf[i] == '\r') { |
| buf[i] = 0; |
| /* Kludge for F-Secure Macintosh < 1.0.2 */ |
| if (i == 12 && |
| strncmp(buf, "SSH-1.5-W1.0", 12) == 0) |
| break; |
| continue; |
| } |
| if (buf[i] == '\n') { |
| buf[i] = 0; |
| break; |
| } |
| } |
| buf[sizeof(buf) - 1] = 0; |
| client_version_string = xstrdup(buf); |
| } |
| |
| /* |
| * Check that the versions match. In future this might accept |
| * several versions and set appropriate flags to handle them. |
| */ |
| if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", |
| &remote_major, &remote_minor, remote_version) != 3) { |
| s = "Protocol mismatch.\n"; |
| (void) atomicio(write, sock_out, s, strlen(s)); |
| close(sock_in); |
| close(sock_out); |
| log("Bad protocol version identification '%.100s' from %s", |
| client_version_string, get_remote_ipaddr()); |
| fatal_cleanup(); |
| } |
| debug("Client protocol version %d.%d; client software version %.100s", |
| remote_major, remote_minor, remote_version); |
| |
| compat_datafellows(remote_version); |
| |
| if (datafellows & SSH_BUG_SCANNER) { |
| log("scanned from %s with %s. Don't panic.", |
| get_remote_ipaddr(), client_version_string); |
| fatal_cleanup(); |
| } |
| |
| mismatch = 0; |
| switch (remote_major) { |
| case 1: |
| if (remote_minor == 99) { |
| if (options.protocol & SSH_PROTO_2) |
| enable_compat20(); |
| else |
| mismatch = 1; |
| break; |
| } |
| if (!(options.protocol & SSH_PROTO_1)) { |
| mismatch = 1; |
| break; |
| } |
| if (remote_minor < 3) { |
| packet_disconnect("Your ssh version is too old and " |
| "is no longer supported. Please install a newer version."); |
| } else if (remote_minor == 3) { |
| /* note that this disables agent-forwarding */ |
| enable_compat13(); |
| } |
| break; |
| case 2: |
| if (options.protocol & SSH_PROTO_2) { |
| enable_compat20(); |
| break; |
| } |
| /* FALLTHROUGH */ |
| default: |
| mismatch = 1; |
| break; |
| } |
| chop(server_version_string); |
| debug("Local version string %.200s", server_version_string); |
| |
| if (mismatch) { |
| s = "Protocol major versions differ.\n"; |
| (void) atomicio(write, sock_out, s, strlen(s)); |
| close(sock_in); |
| close(sock_out); |
| log("Protocol major versions differ for %s: %.200s vs. %.200s", |
| get_remote_ipaddr(), |
| server_version_string, client_version_string); |
| fatal_cleanup(); |
| } |
| } |
| |
| /* 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 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("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); |
| 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 */ |
| 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) { |
| 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; |
| 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; |
| |
| if (authctxt->pw->pw_uid == 0 || options.use_login) { |
| /* 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) { |
| 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); |
| } |
| |
| /* |
| * Main program for the daemon. |
| */ |
| int |
| main(int ac, char **av) |
| { |
| extern char *optarg; |
| extern int optind; |
| int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1; |
| pid_t pid; |
| socklen_t fromlen; |
| fd_set *fdset; |
| struct sockaddr_storage from; |
| const char *remote_ip; |
| int remote_port; |
| FILE *f; |
| struct linger linger; |
| struct addrinfo *ai; |
| char ntop[NI_MAXHOST], strport[NI_MAXSERV]; |
| int listen_sock, maxfd; |
| int startup_p[2]; |
| int startups = 0; |
| Authctxt *authctxt; |
| Key *key; |
| int ret, key_used = 0; |
| |
| #ifdef HAVE_SECUREWARE |
| (void)set_auth_parameters(ac, av); |
| #endif |
| __progname = get_progname(av[0]); |
| init_rng(); |
| |
| /* Save argv. */ |
| saved_argc = ac; |
| saved_argv = av; |
| |
| /* Initialize configuration options to their default values. */ |
| initialize_server_options(&options); |
| |
| /* Parse command-line arguments. */ |
| while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:o:dDeiqtQ46")) != -1) { |
| switch (opt) { |
| case '4': |
| IPv4or6 = AF_INET; |
| break; |
| case '6': |
| IPv4or6 = AF_INET6; |
| break; |
| case 'f': |
| config_file_name = optarg; |
| break; |
| case 'd': |
| if (0 == debug_flag) { |
| debug_flag = 1; |
| options.log_level = SYSLOG_LEVEL_DEBUG1; |
| } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) { |
| options.log_level++; |
| } else { |
| fprintf(stderr, "Too high debugging level.\n"); |
| exit(1); |
| } |
| break; |
| case 'D': |
| no_daemon_flag = 1; |
| break; |
| case 'e': |
| log_stderr = 1; |
| break; |
| case 'i': |
| inetd_flag = 1; |
| break; |
| case 'Q': |
| /* ignored */ |
| break; |
| case 'q': |
| options.log_level = SYSLOG_LEVEL_QUIET; |
| break; |
| case 'b': |
| options.server_key_bits = atoi(optarg); |
| break; |
| case 'p': |
| options.ports_from_cmdline = 1; |
| if (options.num_ports >= MAX_PORTS) { |
| fprintf(stderr, "too many ports.\n"); |
| exit(1); |
| } |
| options.ports[options.num_ports++] = a2port(optarg); |
| if (options.ports[options.num_ports-1] == 0) { |
| fprintf(stderr, "Bad port number.\n"); |
| exit(1); |
| } |
| break; |
| case 'g': |
| if ((options.login_grace_time = convtime(optarg)) == -1) { |
| fprintf(stderr, "Invalid login grace time.\n"); |
| exit(1); |
| } |
| break; |
| case 'k': |
| if ((options.key_regeneration_time = convtime(optarg)) == -1) { |
| fprintf(stderr, "Invalid key regeneration interval.\n"); |
| exit(1); |
| } |
| break; |
| case 'h': |
| if (options.num_host_key_files >= MAX_HOSTKEYS) { |
| fprintf(stderr, "too many host keys.\n"); |
| exit(1); |
| } |
| options.host_key_files[options.num_host_key_files++] = optarg; |
| break; |
| case 'V': |
| client_version_string = optarg; |
| /* only makes sense with inetd_flag, i.e. no listen() */ |
| inetd_flag = 1; |
| break; |
| case 't': |
| test_flag = 1; |
| break; |
| 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: |
| usage(); |
| break; |
| } |
| } |
| SSLeay_add_all_algorithms(); |
| channel_set_af(IPv4or6); |
| |
| /* |
| * Force logging to stderr until we have loaded the private host |
| * key (unless started from inetd) |
| */ |
| log_init(__progname, |
| 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 |
| /* Cray can define user privs drop all prives now! |
| * Not needed on PRIV_SU systems! |
| */ |
| drop_cray_privs(); |
| #endif |
| |
| seed_rng(); |
| |
| /* Read server configuration options from the configuration file. */ |
| read_server_config(&options, config_file_name); |
| |
| /* Fill in default values for those options not explicitly set. */ |
| fill_default_server_options(&options); |
| |
| /* Check that there are no remaining arguments. */ |
| if (optind < ac) { |
| fprintf(stderr, "Extra argument %s.\n", av[optind]); |
| exit(1); |
| } |
| |
| debug("sshd version %.100s", SSH_VERSION); |
| |
| /* 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++) |
| 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++) { |
| key = key_load_private(options.host_key_files[i], "", NULL); |
| sensitive_data.host_keys[i] = key; |
| if (key == NULL) { |
| error("Could not load host key: %s", |
| options.host_key_files[i]); |
| sensitive_data.host_keys[i] = NULL; |
| continue; |
| } |
| switch (key->type) { |
| case KEY_RSA1: |
| sensitive_data.ssh1_host_key = key; |
| sensitive_data.have_ssh1_key = 1; |
| break; |
| case KEY_RSA: |
| case KEY_DSA: |
| sensitive_data.have_ssh2_key = 1; |
| break; |
| } |
| debug("private host key: #%d type %d %s", i, key->type, |
| key_type(key)); |
| } |
| if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) { |
| log("Disabling protocol version 1. Could not load host key"); |
| options.protocol &= ~SSH_PROTO_1; |
| } |
| if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) { |
| log("Disabling protocol version 2. Could not load host key"); |
| options.protocol &= ~SSH_PROTO_2; |
| } |
| if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { |
| log("sshd: no hostkeys available -- exiting."); |
| exit(1); |
| } |
| |
| /* Check certain values for sanity. */ |
| if (options.protocol & SSH_PROTO_1) { |
| if (options.server_key_bits < 512 || |
| options.server_key_bits > 32768) { |
| fprintf(stderr, "Bad server key size.\n"); |
| exit(1); |
| } |
| /* |
| * Check that server and host key lengths differ sufficiently. This |
| * is necessary to make double encryption work with rsaref. Oh, I |
| * hate software patents. I dont know if this can go? Niels |
| */ |
| if (options.server_key_bits > |
| BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED && |
| options.server_key_bits < |
| BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { |
| options.server_key_bits = |
| BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED; |
| debug("Forcing server key to %d bits to make it differ from host key.", |
| options.server_key_bits); |
| } |
| } |
| |
| if (use_privsep) { |
| struct passwd *pw; |
| struct stat st; |
| |
| if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) |
| fatal("Privilege separation user %s does not exist", |
| SSH_PRIVSEP_USER); |
| if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || |
| (S_ISDIR(st.st_mode) == 0)) |
| fatal("Missing privilege separation directory: %s", |
| _PATH_PRIVSEP_CHROOT_DIR); |
| if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) |
| fatal("Bad owner or mode for %s", |
| _PATH_PRIVSEP_CHROOT_DIR); |
| } |
| |
| /* Configuration looks good, so exit if in test mode. */ |
| if (test_flag) |
| exit(0); |
| |
| /* |
| * Clear out any supplemental groups we may have inherited. This |
| * prevents inadvertent creation of files with bad modes (in the |
| * portable version at least, it's certainly possible for PAM |
| * to create a file, and we can't control the code in every |
| * module which might be used). |
| */ |
| if (setgroups(0, NULL) < 0) |
| debug("setgroups() failed: %.200s", strerror(errno)); |
| |
| /* Initialize the log (it is reinitialized below in case we forked). */ |
| if (debug_flag && !inetd_flag) |
| log_stderr = 1; |
| log_init(__progname, options.log_level, options.log_facility, log_stderr); |
| |
| /* |
| * If not in debugging mode, and not started from inetd, disconnect |
| * from the controlling terminal, and fork. The original process |
| * exits. |
| */ |
| if (!(debug_flag || inetd_flag || no_daemon_flag)) { |
| #ifdef TIOCNOTTY |
| int fd; |
| #endif /* TIOCNOTTY */ |
| if (daemon(0, 0) < 0) |
| fatal("daemon() failed: %.200s", strerror(errno)); |
| |
| /* Disconnect from the controlling tty. */ |
| #ifdef TIOCNOTTY |
| fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); |
| if (fd >= 0) { |
| (void) ioctl(fd, TIOCNOTTY, NULL); |
| close(fd); |
| } |
| #endif /* TIOCNOTTY */ |
| } |
| /* Reinitialize the log (because of the fork above). */ |
| log_init(__progname, options.log_level, options.log_facility, log_stderr); |
| |
| /* Initialize the random number generator. */ |
| arc4random_stir(); |
| |
| /* Chdir to the root directory so that the current disk can be |
| unmounted if desired. */ |
| chdir("/"); |
| |
| /* ignore SIGPIPE */ |
| signal(SIGPIPE, SIG_IGN); |
| |
| /* Start listening for a socket, unless started from inetd. */ |
| if (inetd_flag) { |
| int s1; |
| s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */ |
| dup(s1); |
| sock_in = dup(0); |
| sock_out = dup(1); |
| startup_pipe = -1; |
| /* |
| * We intentionally do not close the descriptors 0, 1, and 2 |
| * as our code for setting the descriptors won\'t work if |
| * ttyfd happens to be one of those. |
| */ |
| debug("inetd sockets after dupping: %d, %d", sock_in, sock_out); |
| if (options.protocol & SSH_PROTO_1) |
| generate_ephemeral_server_key(); |
| } else { |
| for (ai = options.listen_addrs; ai; ai = ai->ai_next) { |
| if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) |
| continue; |
| if (num_listen_socks >= MAX_LISTEN_SOCKS) |
| fatal("Too many listen sockets. " |
| "Enlarge MAX_LISTEN_SOCKS"); |
| if (getnameinfo(ai->ai_addr, ai->ai_addrlen, |
| ntop, sizeof(ntop), strport, sizeof(strport), |
| NI_NUMERICHOST|NI_NUMERICSERV) != 0) { |
| error("getnameinfo failed"); |
| continue; |
| } |
| /* Create socket for listening. */ |
| listen_sock = socket(ai->ai_family, SOCK_STREAM, 0); |
| if (listen_sock < 0) { |
| /* kernel may not support ipv6 */ |
| verbose("socket: %.100s", strerror(errno)); |
| continue; |
| } |
| if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) { |
| error("listen_sock O_NONBLOCK: %s", strerror(errno)); |
| close(listen_sock); |
| continue; |
| } |
| /* |
| * Set socket options. We try to make the port |
| * reusable and have it close as fast as possible |
| * without waiting in unnecessary wait states on |
| * close. |
| */ |
| setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, |
| &on, sizeof(on)); |
| linger.l_onoff = 1; |
| linger.l_linger = 5; |
| setsockopt(listen_sock, SOL_SOCKET, SO_LINGER, |
| &linger, sizeof(linger)); |
| |
| debug("Bind to port %s on %s.", strport, ntop); |
| |
| /* Bind the socket to the desired port. */ |
| if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { |
| if (!ai->ai_next) |
| error("Bind to port %s on %s failed: %.200s.", |
| strport, ntop, strerror(errno)); |
| close(listen_sock); |
| continue; |
| } |
| listen_socks[num_listen_socks] = listen_sock; |
| num_listen_socks++; |
| |
| /* Start listening on the port. */ |
| log("Server listening on %s port %s.", ntop, strport); |
| if (listen(listen_sock, 5) < 0) |
| fatal("listen: %.100s", strerror(errno)); |
| |
| } |
| freeaddrinfo(options.listen_addrs); |
| |
| if (!num_listen_socks) |
| fatal("Cannot bind any address."); |
| |
| if (options.protocol & SSH_PROTO_1) |
| generate_ephemeral_server_key(); |
| |
| /* |
| * Arrange to restart on SIGHUP. The handler needs |
| * listen_sock. |
| */ |
| signal(SIGHUP, sighup_handler); |
| |
| signal(SIGTERM, sigterm_handler); |
| signal(SIGQUIT, sigterm_handler); |
| |
| /* Arrange SIGCHLD to be caught. */ |
| signal(SIGCHLD, main_sigchld_handler); |
| |
| /* Write out the pid file after the sigterm handler is setup */ |
| if (!debug_flag) { |
| /* |
| * Record our pid in /var/run/sshd.pid to make it |
| * easier to kill the correct sshd. We don't want to |
| * do this before the bind above because the bind will |
| * fail if there already is a daemon, and this will |
| * overwrite any old pid in the file. |
| */ |
| f = fopen(options.pid_file, "wb"); |
| if (f) { |
| fprintf(f, "%ld\n", (long) getpid()); |
| fclose(f); |
| } |
| } |
| |
| /* setup fd set for listen */ |
| fdset = NULL; |
| maxfd = 0; |
| for (i = 0; i < num_listen_socks; i++) |
| if (listen_socks[i] > maxfd) |
| maxfd = listen_socks[i]; |
| /* pipes connected to unauthenticated childs */ |
| startup_pipes = xmalloc(options.max_startups * sizeof(int)); |
| for (i = 0; i < options.max_startups; i++) |
| startup_pipes[i] = -1; |
| |
| /* |
| * Stay listening for connections until the system crashes or |
| * the daemon is killed with a signal. |
| */ |
| for (;;) { |
| if (received_sighup) |
| sighup_restart(); |
| if (fdset != NULL) |
| xfree(fdset); |
| fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask); |
| fdset = (fd_set *)xmalloc(fdsetsz); |
| memset(fdset, 0, fdsetsz); |
| |
| for (i = 0; i < num_listen_socks; i++) |
| FD_SET(listen_socks[i], fdset); |
| for (i = 0; i < options.max_startups; i++) |
| if (startup_pipes[i] != -1) |
| FD_SET(startup_pipes[i], fdset); |
| |
| /* Wait in select until there is a connection. */ |
| ret = select(maxfd+1, fdset, NULL, NULL, NULL); |
| if (ret < 0 && errno != EINTR) |
| error("select: %.100s", strerror(errno)); |
| if (received_sigterm) { |
| log("Received signal %d; terminating.", |
| (int) received_sigterm); |
| close_listen_socks(); |
| unlink(options.pid_file); |
| exit(255); |
| } |
| if (key_used && key_do_regen) { |
| generate_ephemeral_server_key(); |
| key_used = 0; |
| key_do_regen = 0; |
| } |
| if (ret < 0) |
| continue; |
| |
| for (i = 0; i < options.max_startups; i++) |
| if (startup_pipes[i] != -1 && |
| FD_ISSET(startup_pipes[i], fdset)) { |
| /* |
| * the read end of the pipe is ready |
| * if the child has closed the pipe |
| * after successful authentication |
| * or if the child has died |
| */ |
| close(startup_pipes[i]); |
| startup_pipes[i] = -1; |
| startups--; |
| } |
| for (i = 0; i < num_listen_socks; i++) { |
| if (!FD_ISSET(listen_socks[i], fdset)) |
| continue; |
| fromlen = sizeof(from); |
| newsock = accept(listen_socks[i], (struct sockaddr *)&from, |
| &fromlen); |
| if (newsock < 0) { |
| if (errno != EINTR && errno != EWOULDBLOCK) |
| error("accept: %.100s", strerror(errno)); |
| continue; |
| } |
| if (fcntl(newsock, F_SETFL, 0) < 0) { |
| error("newsock del O_NONBLOCK: %s", strerror(errno)); |
| close(newsock); |
| continue; |
| } |
| if (drop_connection(startups) == 1) { |
| debug("drop connection #%d", startups); |
| close(newsock); |
| continue; |
| } |
| if (pipe(startup_p) == -1) { |
| close(newsock); |
| continue; |
| } |
| |
| for (j = 0; j < options.max_startups; j++) |
| if (startup_pipes[j] == -1) { |
| startup_pipes[j] = startup_p[0]; |
| if (maxfd < startup_p[0]) |
| maxfd = startup_p[0]; |
| startups++; |
| break; |
| } |
| |
| /* |
| * Got connection. Fork a child to handle it, unless |
| * we are in debugging mode. |
| */ |
| if (debug_flag) { |
| /* |
| * In debugging mode. Close the listening |
| * socket, and start processing the |
| * connection without forking. |
| */ |
| debug("Server will not fork when running in debugging mode."); |
| close_listen_socks(); |
| sock_in = newsock; |
| sock_out = newsock; |
| startup_pipe = -1; |
| pid = getpid(); |
| break; |
| } else { |
| /* |
| * Normal production daemon. Fork, and have |
| * the child process the connection. The |
| * parent continues listening. |
| */ |
| if ((pid = fork()) == 0) { |
| /* |
| * Child. Close the listening and max_startup |
| * sockets. Start using the accepted socket. |
| * Reinitialize logging (since our pid has |
| * changed). We break out of the loop to handle |
| * the connection. |
| */ |
| startup_pipe = startup_p[1]; |
| close_startup_pipes(); |
| close_listen_socks(); |
| sock_in = newsock; |
| sock_out = newsock; |
| log_init(__progname, options.log_level, options.log_facility, log_stderr); |
| break; |
| } |
| } |
| |
| /* Parent. Stay in the loop. */ |
| if (pid < 0) |
| error("fork: %.100s", strerror(errno)); |
| else |
| debug("Forked child %ld.", (long)pid); |
| |
| close(startup_p[1]); |
| |
| /* Mark that the key has been used (it was "given" to the child). */ |
| if ((options.protocol & SSH_PROTO_1) && |
| key_used == 0) { |
| /* Schedule server key regeneration alarm. */ |
| signal(SIGALRM, key_regeneration_alarm); |
| alarm(options.key_regeneration_time); |
| key_used = 1; |
| } |
| |
| arc4random_stir(); |
| |
| /* Close the new socket (the child is now taking care of it). */ |
| close(newsock); |
| } |
| /* child process check (or debug mode) */ |
| if (num_listen_socks < 0) |
| break; |
| } |
| } |
| |
| /* This is the child processing a new connection. */ |
| |
| /* |
| * Create a new session and process group since the 4.4BSD |
| * setlogin() affects the entire process group. We don't |
| * want the child to be able to affect the parent. |
| */ |
| #if 0 |
| /* XXX: this breaks Solaris */ |
| if (!debug_flag && !inetd_flag && setsid() < 0) |
| error("setsid: %.100s", strerror(errno)); |
| #endif |
| |
| /* |
| * Disable the key regeneration alarm. We will not regenerate the |
| * key since we are no longer in a position to give it to anyone. We |
| * will not restart on SIGHUP since it no longer makes sense. |
| */ |
| alarm(0); |
| signal(SIGALRM, SIG_DFL); |
| signal(SIGHUP, SIG_DFL); |
| signal(SIGTERM, SIG_DFL); |
| signal(SIGQUIT, SIG_DFL); |
| signal(SIGCHLD, SIG_DFL); |
| signal(SIGINT, SIG_DFL); |
| |
| /* |
| * Set socket options for the connection. We want the socket to |
| * close as fast as possible without waiting for anything. If the |
| * connection is not a socket, these will do nothing. |
| */ |
| /* 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, &linger, sizeof(linger)); |
| |
| /* Set keepalives if requested. */ |
| if (options.keepalives && |
| setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, |
| sizeof(on)) < 0) |
| error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); |
| |
| /* |
| * Register our connection. This turns encryption off because we do |
| * not have a key. |
| */ |
| packet_set_connection(sock_in, sock_out); |
| |
| remote_port = get_remote_port(); |
| remote_ip = get_remote_ipaddr(); |
| |
| #ifdef LIBWRAP |
| /* Check whether logins are denied from this host. */ |
| { |
| struct request_info req; |
| |
| request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0); |
| fromhost(&req); |
| |
| if (!hosts_access(&req)) { |
| debug("Connection refused by tcp wrapper"); |
| refuse(&req); |
| /* NOTREACHED */ |
| fatal("libwrap refuse returns"); |
| } |
| } |
| #endif /* LIBWRAP */ |
| |
| /* Log the connection. */ |
| verbose("Connection from %.500s port %d", remote_ip, remote_port); |
| |
| /* |
| * We don\'t want to listen forever unless the other side |
| * successfully authenticates itself. So we set up an alarm which is |
| * cleared after successful authentication. A limit of zero |
| * indicates no limit. Note that we don\'t set the alarm in debugging |
| * mode; it is just annoying to have the server exit just when you |
| * are about to discover the bug. |
| */ |
| signal(SIGALRM, grace_alarm_handler); |
| if (!debug_flag) |
| alarm(options.login_grace_time); |
| |
| sshd_exchange_identification(sock_in, sock_out); |
| /* |
| * Check that the connection comes from a privileged port. |
| * Rhosts-Authentication only makes sense from privileged |
| * programs. Of course, if the intruder has root access on his local |
| * machine, he can connect from any port. So do not use these |
| * authentication methods from machines that you do not trust. |
| */ |
| 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; |
| } |
| #if defined(KRB4) && !defined(KRB5) |
| if (!packet_connection_is_ipv4() && |
| options.kerberos_authentication) { |
| debug("Kerberos Authentication disabled, only available for IPv4."); |
| options.kerberos_authentication = 0; |
| } |
| #endif /* KRB4 && !KRB5 */ |
| #ifdef AFS |
| /* If machine has AFS, set process authentication group. */ |
| if (k_hasafs()) { |
| k_setpag(); |
| k_unlog(); |
| } |
| #endif /* AFS */ |
| |
| 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(); |
| authctxt = do_authentication2(); |
| } else { |
| do_ssh1_kex(); |
| authctxt = do_authentication(); |
| } |
| /* |
| * If we use privilege separation, the unprivileged child transfers |
| * the current keystate and exits |
| */ |
| if (use_privsep) { |
| mm_send_keystate(pmonitor); |
| 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); |
| |
| #ifdef USE_PAM |
| finish_pam(); |
| #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 |
| */ |
| static void |
| do_ssh1_kex(void) |
| { |
| int i, len; |
| int rsafail = 0; |
| BIGNUM *session_key_int; |
| u_char session_key[SSH_SESSION_KEY_LENGTH]; |
| u_char cookie[8]; |
| u_int cipher_type, auth_mask, protocol_flags; |
| u_int32_t rand = 0; |
| |
| /* |
| * Generate check bytes that the client must send back in the user |
| * packet in order for it to be accepted; this is used to defy ip |
| * spoofing attacks. Note that this only works against somebody |
| * doing IP spoofing from a remote machine; any machine on the local |
| * network can still see outgoing packets and catch the random |
| * cookie. This only affects rhosts authentication, and this is one |
| * of the reasons why it is inherently insecure. |
| */ |
| for (i = 0; i < 8; i++) { |
| if (i % 4 == 0) |
| rand = arc4random(); |
| cookie[i] = rand & 0xff; |
| rand >>= 8; |
| } |
| |
| /* |
| * Send our public key. We include in the packet 64 bits of random |
| * data that must be matched in the reply in order to prevent IP |
| * spoofing. |
| */ |
| packet_start(SSH_SMSG_PUBLIC_KEY); |
| for (i = 0; i < 8; i++) |
| packet_put_char(cookie[i]); |
| |
| /* Store our public server RSA key. */ |
| packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n)); |
| packet_put_bignum(sensitive_data.server_key->rsa->e); |
| packet_put_bignum(sensitive_data.server_key->rsa->n); |
| |
| /* Store our public host RSA key. */ |
| packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); |
| packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e); |
| packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n); |
| |
| /* Put protocol flags. */ |
| packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); |
| |
| /* Declare which ciphers we support. */ |
| packet_put_int(cipher_mask_ssh1(0)); |
| |
| /* Declare supported authentication types. */ |
| auth_mask = 0; |
| if (options.rhosts_authentication) |
| auth_mask |= 1 << SSH_AUTH_RHOSTS; |
| if (options.rhosts_rsa_authentication) |
| auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; |
| if (options.rsa_authentication) |
| auth_mask |= 1 << SSH_AUTH_RSA; |
| #if defined(KRB4) || defined(KRB5) |
| if (options.kerberos_authentication) |
| auth_mask |= 1 << SSH_AUTH_KERBEROS; |
| #endif |
| #if defined(AFS) || defined(KRB5) |
| if (options.kerberos_tgt_passing) |
| auth_mask |= 1 << SSH_PASS_KERBEROS_TGT; |
| #endif |
| #ifdef AFS |
| if (options.afs_token_passing) |
| auth_mask |= 1 << SSH_PASS_AFS_TOKEN; |
| #endif |
| if (options.challenge_response_authentication == 1) |
| auth_mask |= 1 << SSH_AUTH_TIS; |
| if (options.password_authentication) |
| auth_mask |= 1 << SSH_AUTH_PASSWORD; |
| packet_put_int(auth_mask); |
| |
| /* Send the packet and wait for it to be sent. */ |
| packet_send(); |
| packet_write_wait(); |
| |
| debug("Sent %d bit server key and %d bit host key.", |
| BN_num_bits(sensitive_data.server_key->rsa->n), |
| BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); |
| |
| /* Read clients reply (cipher type and session key). */ |
| packet_read_expect(SSH_CMSG_SESSION_KEY); |
| |
| /* Get cipher type and check whether we accept this. */ |
| cipher_type = packet_get_char(); |
| |
| if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) |
| packet_disconnect("Warning: client selects unsupported cipher."); |
| |
| /* Get check bytes from the packet. These must match those we |
| sent earlier with the public key packet. */ |
| for (i = 0; i < 8; i++) |
| if (cookie[i] != packet_get_char()) |
| packet_disconnect("IP Spoofing check bytes do not match."); |
| |
| debug("Encryption type: %.200s", cipher_name(cipher_type)); |
| |
| /* Get the encrypted integer. */ |
| 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(); |
| |
| /* Decrypt session_key_int using host/server keys */ |
| rsafail = PRIVSEP(ssh1_session_key(session_key_int)); |
| |
| /* |
| * Extract session key from the decrypted integer. The key is in the |
| * least significant 256 bits of the integer; the first byte of the |
| * key is in the highest bits. |
| */ |
| if (!rsafail) { |
| BN_mask_bits(session_key_int, sizeof(session_key) * 8); |
| len = BN_num_bytes(session_key_int); |
| if (len < 0 || len > sizeof(session_key)) { |
| error("do_connection: bad session key len from %s: " |
| "session_key_int %d > sizeof(session_key) %lu", |
| get_remote_ipaddr(), len, (u_long)sizeof(session_key)); |
| rsafail++; |
| } else { |
| memset(session_key, 0, sizeof(session_key)); |
| BN_bn2bin(session_key_int, |
| session_key + sizeof(session_key) - len); |
| |
| compute_session_id(session_id, cookie, |
| sensitive_data.ssh1_host_key->rsa->n, |
| sensitive_data.server_key->rsa->n); |
| /* |
| * Xor the first 16 bytes of the session key with the |
| * session id. |
| */ |
| for (i = 0; i < 16; i++) |
| session_key[i] ^= session_id[i]; |
| } |
| } |
| if (rsafail) { |
| int bytes = BN_num_bytes(session_key_int); |
| u_char *buf = xmalloc(bytes); |
| MD5_CTX md; |
| |
| log("do_connection: generating a fake encryption key"); |
| BN_bn2bin(session_key_int, buf); |
| MD5_Init(&md); |
| MD5_Update(&md, buf, bytes); |
| MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); |
| MD5_Final(session_key, &md); |
| MD5_Init(&md); |
| MD5_Update(&md, session_key, 16); |
| MD5_Update(&md, buf, bytes); |
| MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); |
| MD5_Final(session_key + 16, &md); |
| memset(buf, 0, bytes); |
| xfree(buf); |
| for (i = 0; i < 16; i++) |
| session_id[i] = session_key[i] ^ session_key[i + 16]; |
| } |
| /* 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); |
| |
| /* Set the session key. From this on all communications will be encrypted. */ |
| packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); |
| |
| /* Destroy our copy of the session key. It is no longer needed. */ |
| memset(session_key, 0, sizeof(session_key)); |
| |
| debug("Received session key; encryption turned on."); |
| |
| /* Send an acknowledgment packet. Note that this packet is sent encrypted. */ |
| packet_start(SSH_SMSG_SUCCESS); |
| packet_send(); |
| packet_write_wait(); |
| } |
| |
| /* |
| * SSH2 key exchange: diffie-hellman-group1-sha1 |
| */ |
| static void |
| do_ssh2_kex(void) |
| { |
| Kex *kex; |
| |
| if (options.ciphers != NULL) { |
| myproposal[PROPOSAL_ENC_ALGS_CTOS] = |
| myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; |
| } |
| myproposal[PROPOSAL_ENC_ALGS_CTOS] = |
| compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]); |
| myproposal[PROPOSAL_ENC_ALGS_STOC] = |
| compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]); |
| |
| if (options.macs != NULL) { |
| myproposal[PROPOSAL_MAC_ALGS_CTOS] = |
| myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; |
| } |
| if (!options.compression) { |
| myproposal[PROPOSAL_COMP_ALGS_CTOS] = |
| myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; |
| } |
| myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types(); |
| |
| /* start key exchange */ |
| kex = kex_setup(myproposal); |
| kex->server = 1; |
| 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; |
| |
| dispatch_run(DISPATCH_BLOCK, &kex->done, kex); |
| |
| session_id2 = kex->session_id; |
| session_id2_len = kex->session_id_len; |
| |
| #ifdef DEBUG_KEXDH |
| /* send 1st encrypted/maced/compressed message */ |
| packet_start(SSH2_MSG_IGNORE); |
| packet_put_cstring("markus"); |
| packet_send(); |
| packet_write_wait(); |
| #endif |
| debug("KEX done"); |
| } |