diff options
Diffstat (limited to 'crypto/openssh/sshd.c')
| -rw-r--r-- | crypto/openssh/sshd.c | 2156 |
1 files changed, 2156 insertions, 0 deletions
diff --git a/crypto/openssh/sshd.c b/crypto/openssh/sshd.c new file mode 100644 index 0000000..4aa1c98 --- /dev/null +++ b/crypto/openssh/sshd.c @@ -0,0 +1,2156 @@ +/* $OpenBSD: sshd.c,v 1.348 2006/11/06 21:25:28 markus Exp $ */ +/* + * 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" + +#include <sys/types.h> +#include <sys/ioctl.h> +#include <sys/socket.h> +#ifdef HAVE_SYS_STAT_H +# include <sys/stat.h> +#endif +#ifdef HAVE_SYS_TIME_H +# include <sys/time.h> +#endif +#include "openbsd-compat/sys-tree.h" +#include <sys/wait.h> + +#include <errno.h> +#include <fcntl.h> +#include <netdb.h> +#ifdef HAVE_PATHS_H +#include <paths.h> +#endif +#include <grp.h> +#include <pwd.h> +#include <signal.h> +#include <stdarg.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +#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 "xmalloc.h" +#include "ssh.h" +#include "ssh1.h" +#include "ssh2.h" +#include "rsa.h" +#include "sshpty.h" +#include "packet.h" +#include "log.h" +#include "buffer.h" +#include "servconf.h" +#include "uidswap.h" +#include "compat.h" +#include "cipher.h" +#include "key.h" +#include "kex.h" +#include "dh.h" +#include "myproposal.h" +#include "authfile.h" +#include "pathnames.h" +#include "atomicio.h" +#include "canohost.h" +#include "hostfile.h" +#include "auth.h" +#include "misc.h" +#include "msg.h" +#include "dispatch.h" +#include "channels.h" +#include "session.h" +#include "monitor_mm.h" +#include "monitor.h" +#ifdef GSSAPI +#include "ssh-gss.h" +#endif +#include "monitor_wrap.h" +#include "monitor_fdpass.h" +#include "version.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 + +/* Re-exec fds */ +#define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1) +#define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2) +#define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3) +#define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4) + +extern char *__progname; + +/* Server configuration options. */ +ServerOptions options; + +/* Name of the server configuration file. */ +char *config_file_name = _PATH_SERVER_CONFIG_FILE; + +/* + * 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; + +/* re-exec */ +int rexeced_flag = 0; +int rexec_flag = 1; +int rexec_argc = 0; +char **rexec_argv; + +/* + * 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; +u_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 */ +int use_privsep = -1; +struct monitor *pmonitor = NULL; + +/* global authentication context */ +Authctxt *the_authctxt = NULL; + +/* sshd_config buffer */ +Buffer cfg; + +/* message to be displayed after login */ +Buffer loginmsg; + +/* Unprivileged user */ +struct passwd *privsep_pw = NULL; + +/* 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). + */ + +/*ARGSUSED*/ +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) +{ + logit("Received SIGHUP; restarting."); + close_listen_socks(); + close_startup_pipes(); + execv(saved_argv[0], saved_argv); + logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], + strerror(errno)); + exit(1); +} + +/* + * Generic signal handler for terminating signals in the master daemon. + */ +/*ARGSUSED*/ +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. + */ +/*ARGSUSED*/ +static void +main_sigchld_handler(int sig) +{ + int save_errno = errno; + pid_t pid; + 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. + */ +/*ARGSUSED*/ +static void +grace_alarm_handler(int sig) +{ + if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0) + kill(pmonitor->m_pid, SIGALRM); + + /* Log error and exit. */ + sigdie("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 rnd = 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) + rnd = arc4random(); + sensitive_data.ssh1_cookie[i] = rnd & 0xff; + rnd >>= 8; + } + arc4random_stir(); +} + +/*ARGSUSED*/ +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) +{ + u_int i; + int 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); + + /* Send our protocol version identification. */ + if (atomicio(vwrite, sock_out, server_version_string, + strlen(server_version_string)) + != strlen(server_version_string)) { + logit("Could not write ident string to %s", get_remote_ipaddr()); + cleanup_exit(255); + } + + /* 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) { + logit("Did not receive identification string from %s", + get_remote_ipaddr()); + cleanup_exit(255); + } + 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(vwrite, sock_out, s, strlen(s)); + close(sock_in); + close(sock_out); + logit("Bad protocol version identification '%.100s' from %s", + client_version_string, get_remote_ipaddr()); + cleanup_exit(255); + } + debug("Client protocol version %d.%d; client software version %.100s", + remote_major, remote_minor, remote_version); + + compat_datafellows(remote_version); + + if (datafellows & SSH_BUG_PROBE) { + logit("probed from %s with %s. Don't panic.", + get_remote_ipaddr(), client_version_string); + cleanup_exit(255); + } + + if (datafellows & SSH_BUG_SCANNER) { + logit("scanned from %s with %s. Don't panic.", + get_remote_ipaddr(), client_version_string); + cleanup_exit(255); + } + + 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(vwrite, sock_out, s, strlen(s)); + close(sock_in); + close(sock_out); + logit("Protocol major versions differ for %s: %.200s vs. %.200s", + get_remote_ipaddr(), + server_version_string, client_version_string); + cleanup_exit(255); + } +} + +/* 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]; + 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(); + + /* 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)privsep_pw->pw_uid, + (u_int)privsep_pw->pw_gid); +#if 0 + /* XXX not ready, too heavy after chroot */ + do_setusercontext(privsep_pw); +#else + gidset[0] = privsep_pw->pw_gid; + if (setgroups(1, gidset) < 0) + fatal("setgroups: %.100s", strerror(errno)); + permanently_set_uid(privsep_pw); +#endif +} + +static int +privsep_preauth(Authctxt *authctxt) +{ + 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); + pmonitor->m_pid = pid; + monitor_child_preauth(authctxt, 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 (1); + } else { + /* child */ + + close(pmonitor->m_sendfd); + + /* Demote the child */ + if (getuid() == 0 || geteuid() == 0) + privsep_preauth_child(); + setproctitle("%s", "[net]"); + } + return (0); +} + +static void +privsep_postauth(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 */ + use_privsep = 0; + goto skip; + } + + /* 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); + buffer_clear(&loginmsg); + 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); + + skip: + /* It is safe now to apply the key state */ + monitor_apply_keystate(pmonitor); + + /* + * Tell the packet layer that authentication was successful, since + * this information is not part of the key state. + */ + packet_set_authenticated(); +} + +static char * +list_hostkey_types(void) +{ + Buffer b; + const char *p; + char *ret; + 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); + ret = xstrdup(buffer_ptr(&b)); + buffer_free(&b); + debug("list_hostkey_types: %s", ret); + return ret; +} + +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) +{ + int 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 /= options.max_startups - options.max_startups_begin; + p += options.max_startups_rate; + r = arc4random() % 100; + + debug("drop_connection: p %d, r %d", p, r); + return (r < p) ? 1 : 0; +} + +static void +usage(void) +{ + fprintf(stderr, "%s, %s\n", + SSH_RELEASE, SSLeay_version(SSLEAY_VERSION)); + fprintf(stderr, +"usage: sshd [-46Ddeiqt] [-b bits] [-f config_file] [-g login_grace_time]\n" +" [-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len]\n" + ); + exit(1); +} + +static void +send_rexec_state(int fd, Buffer *conf) +{ + Buffer m; + + debug3("%s: entering fd = %d config len %d", __func__, fd, + buffer_len(conf)); + + /* + * Protocol from reexec master to child: + * string configuration + * u_int ephemeral_key_follows + * bignum e (only if ephemeral_key_follows == 1) + * bignum n " + * bignum d " + * bignum iqmp " + * bignum p " + * bignum q " + * string rngseed (only if OpenSSL is not self-seeded) + */ + buffer_init(&m); + buffer_put_cstring(&m, buffer_ptr(conf)); + + if (sensitive_data.server_key != NULL && + sensitive_data.server_key->type == KEY_RSA1) { + buffer_put_int(&m, 1); + buffer_put_bignum(&m, sensitive_data.server_key->rsa->e); + buffer_put_bignum(&m, sensitive_data.server_key->rsa->n); + buffer_put_bignum(&m, sensitive_data.server_key->rsa->d); + buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp); + buffer_put_bignum(&m, sensitive_data.server_key->rsa->p); + buffer_put_bignum(&m, sensitive_data.server_key->rsa->q); + } else + buffer_put_int(&m, 0); + +#ifndef OPENSSL_PRNG_ONLY + rexec_send_rng_seed(&m); +#endif + + if (ssh_msg_send(fd, 0, &m) == -1) + fatal("%s: ssh_msg_send failed", __func__); + + buffer_free(&m); + + debug3("%s: done", __func__); +} + +static void +recv_rexec_state(int fd, Buffer *conf) +{ + Buffer m; + char *cp; + u_int len; + + debug3("%s: entering fd = %d", __func__, fd); + + buffer_init(&m); + + if (ssh_msg_recv(fd, &m) == -1) + fatal("%s: ssh_msg_recv failed", __func__); + if (buffer_get_char(&m) != 0) + fatal("%s: rexec version mismatch", __func__); + + cp = buffer_get_string(&m, &len); + if (conf != NULL) + buffer_append(conf, cp, len + 1); + xfree(cp); + + if (buffer_get_int(&m)) { + if (sensitive_data.server_key != NULL) + key_free(sensitive_data.server_key); + sensitive_data.server_key = key_new_private(KEY_RSA1); + buffer_get_bignum(&m, sensitive_data.server_key->rsa->e); + buffer_get_bignum(&m, sensitive_data.server_key->rsa->n); + buffer_get_bignum(&m, sensitive_data.server_key->rsa->d); + buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp); + buffer_get_bignum(&m, sensitive_data.server_key->rsa->p); + buffer_get_bignum(&m, sensitive_data.server_key->rsa->q); + rsa_generate_additional_parameters( + sensitive_data.server_key->rsa); + } + +#ifndef OPENSSL_PRNG_ONLY + rexec_recv_rng_seed(&m); +#endif + + buffer_free(&m); + + debug3("%s: done", __func__); +} + +/* Accept a connection from inetd */ +static void +server_accept_inetd(int *sock_in, int *sock_out) +{ + int fd; + + startup_pipe = -1; + if (rexeced_flag) { + close(REEXEC_CONFIG_PASS_FD); + *sock_in = *sock_out = dup(STDIN_FILENO); + if (!debug_flag) { + startup_pipe = dup(REEXEC_STARTUP_PIPE_FD); + close(REEXEC_STARTUP_PIPE_FD); + } + } else { + *sock_in = dup(STDIN_FILENO); + *sock_out = dup(STDOUT_FILENO); + } + /* + * 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. + */ + if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { + dup2(fd, STDIN_FILENO); + dup2(fd, STDOUT_FILENO); + if (fd > STDOUT_FILENO) + close(fd); + } + debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out); +} + +/* + * Listen for TCP connections + */ +static void +server_listen(void) +{ + int ret, listen_sock, on = 1; + struct addrinfo *ai; + char ntop[NI_MAXHOST], strport[NI_MAXSERV]; + + 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 ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen, + ntop, sizeof(ntop), strport, sizeof(strport), + NI_NUMERICHOST|NI_NUMERICSERV)) != 0) { + error("getnameinfo failed: %.100s", + (ret != EAI_SYSTEM) ? gai_strerror(ret) : + strerror(errno)); + continue; + } + /* Create socket for listening. */ + listen_sock = socket(ai->ai_family, ai->ai_socktype, + ai->ai_protocol); + if (listen_sock < 0) { + /* kernel may not support ipv6 */ + verbose("socket: %.100s", strerror(errno)); + continue; + } + if (set_nonblock(listen_sock) == -1) { + close(listen_sock); + continue; + } + /* + * Set socket options. + * Allow local port reuse in TIME_WAIT. + */ + if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, + &on, sizeof(on)) == -1) + error("setsockopt SO_REUSEADDR: %s", strerror(errno)); + + 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) { + 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. */ + if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0) + fatal("listen on [%s]:%s: %.100s", + ntop, strport, strerror(errno)); + logit("Server listening on %s port %s.", ntop, strport); + } + freeaddrinfo(options.listen_addrs); + + if (!num_listen_socks) + fatal("Cannot bind any address."); +} + +/* + * The main TCP accept loop. Note that, for the non-debug case, returns + * from this function are in a forked subprocess. + */ +static void +server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s) +{ + fd_set *fdset; + int i, j, ret, maxfd; + int key_used = 0, startups = 0; + int startup_p[2] = { -1 , -1 }; + struct sockaddr_storage from; + socklen_t fromlen; + pid_t pid; + + /* setup fd set for accept */ + 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 = xcalloc(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); + fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS), + sizeof(fd_mask)); + + 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) { + logit("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 (unset_nonblock(*newsock) == -1) { + close(*newsock); + continue; + } + if (drop_connection(startups) == 1) { + debug("drop connection #%d", startups); + close(*newsock); + continue; + } + if (pipe(startup_p) == -1) { + close(*newsock); + continue; + } + + if (rexec_flag && socketpair(AF_UNIX, + SOCK_STREAM, 0, config_s) == -1) { + error("reexec socketpair: %s", + strerror(errno)); + close(*newsock); + close(startup_p[0]); + close(startup_p[1]); + 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; + close(startup_p[0]); + close(startup_p[1]); + startup_pipe = -1; + pid = getpid(); + if (rexec_flag) { + send_rexec_state(config_s[0], + &cfg); + close(config_s[0]); + } + break; + } + + /* + * Normal production daemon. Fork, and have + * the child process the connection. The + * parent continues listening. + */ + platform_pre_fork(); + 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. + */ + platform_post_fork_child(); + 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); + if (rexec_flag) + close(config_s[0]); + break; + } + + /* Parent. Stay in the loop. */ + platform_post_fork_parent(pid); + if (pid < 0) + error("fork: %.100s", strerror(errno)); + else + debug("Forked child %ld.", (long)pid); + + close(startup_p[1]); + + if (rexec_flag) { + send_rexec_state(config_s[0], &cfg); + close(config_s[0]); + close(config_s[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; + } + + close(*newsock); + + /* + * Ensure that our random state differs + * from that of the child + */ + arc4random_stir(); + } + + /* child process check (or debug mode) */ + if (num_listen_socks < 0) + break; + } +} + + +/* + * Main program for the daemon. + */ +int +main(int ac, char **av) +{ + extern char *optarg; + extern int optind; + int opt, i, on = 1; + int sock_in = -1, sock_out = -1, newsock = -1; + const char *remote_ip; + int remote_port; + char *line; + int config_s[2] = { -1 , -1 }; + Key *key; + Authctxt *authctxt; + +#ifdef HAVE_SECUREWARE + (void)set_auth_parameters(ac, av); +#endif + __progname = ssh_get_progname(av[0]); + init_rng(); + + /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ + saved_argc = ac; + rexec_argc = ac; + saved_argv = xcalloc(ac + 1, sizeof(*saved_argv)); + for (i = 0; i < ac; i++) + saved_argv[i] = xstrdup(av[i]); + saved_argv[i] = NULL; + +#ifndef HAVE_SETPROCTITLE + /* Prepare for later setproctitle emulation */ + compat_init_setproctitle(ac, av); + av = saved_argv; +#endif + + if (geteuid() == 0 && setgroups(0, NULL) == -1) + debug("setgroups(): %.200s", strerror(errno)); + + /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ + sanitise_stdfd(); + + /* 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:u:o:dDeiqrtQR46")) != -1) { + switch (opt) { + case '4': + options.address_family = AF_INET; + break; + case '6': + options.address_family = AF_INET6; + break; + case 'f': + config_file_name = optarg; + break; + case 'd': + if (debug_flag == 0) { + debug_flag = 1; + options.log_level = SYSLOG_LEVEL_DEBUG1; + } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) + options.log_level++; + break; + case 'D': + no_daemon_flag = 1; + break; + case 'e': + log_stderr = 1; + break; + case 'i': + inetd_flag = 1; + break; + case 'r': + rexec_flag = 0; + break; + case 'R': + rexeced_flag = 1; + inetd_flag = 1; + break; + case 'Q': + /* ignored */ + break; + case 'q': + options.log_level = SYSLOG_LEVEL_QUIET; + break; + case 'b': + options.server_key_bits = (int)strtonum(optarg, 256, + 32768, NULL); + 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 't': + test_flag = 1; + break; + case 'u': + utmp_len = (u_int)strtonum(optarg, 0, MAXHOSTNAMELEN+1, NULL); + if (utmp_len > MAXHOSTNAMELEN) { + fprintf(stderr, "Invalid utmp length.\n"); + exit(1); + } + break; + case 'o': + line = xstrdup(optarg); + if (process_server_config_line(&options, line, + "command-line", 0, NULL, NULL, NULL, NULL) != 0) + exit(1); + xfree(line); + break; + case '?': + default: + usage(); + break; + } + } + if (rexeced_flag || inetd_flag) + rexec_flag = 0; + if (rexec_flag && (av[0] == NULL || *av[0] != '/')) + fatal("sshd re-exec requires execution with an absolute path"); + if (rexeced_flag) + closefrom(REEXEC_MIN_FREE_FD); + else + closefrom(REEXEC_DEVCRYPTO_RESERVED_FD); + + SSLeay_add_all_algorithms(); + + /* + * 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, + log_stderr || !inetd_flag); + + /* + * Unset KRB5CCNAME, otherwise the user's session may inherit it from + * root's environment + */ + if (getenv("KRB5CCNAME") != NULL) + unsetenv("KRB5CCNAME"); + +#ifdef _UNICOS + /* Cray can define user privs drop all privs now! + * Not needed on PRIV_SU systems! + */ + drop_cray_privs(); +#endif + + sensitive_data.server_key = NULL; + sensitive_data.ssh1_host_key = NULL; + sensitive_data.have_ssh1_key = 0; + sensitive_data.have_ssh2_key = 0; + + /* Fetch our configuration */ + buffer_init(&cfg); + if (rexeced_flag) + recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg); + else + load_server_config(config_file_name, &cfg); + + parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name, + &cfg, NULL, NULL, NULL); + + seed_rng(); + + /* Fill in default values for those options not explicitly set. */ + fill_default_server_options(&options); + + /* set default channel AF */ + channel_set_af(options.address_family); + + /* 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_RELEASE); + + /* Store privilege separation user for later use if required. */ + if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) { + if (use_privsep || options.kerberos_authentication) + fatal("Privilege separation user %s does not exist", + SSH_PRIVSEP_USER); + } else { + memset(privsep_pw->pw_passwd, 0, strlen(privsep_pw->pw_passwd)); + privsep_pw = pwcopy(privsep_pw); + xfree(privsep_pw->pw_passwd); + privsep_pw->pw_passwd = xstrdup("*"); + } + endpwent(); + + /* load private host keys */ + sensitive_data.host_keys = xcalloc(options.num_host_key_files, + sizeof(Key *)); + for (i = 0; i < options.num_host_key_files; i++) + sensitive_data.host_keys[i] = NULL; + + 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) { + logit("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) { + logit("Disabling protocol version 2. Could not load host key"); + options.protocol &= ~SSH_PROTO_2; + } + if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { + logit("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 stat st; + + if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || + (S_ISDIR(st.st_mode) == 0)) + fatal("Missing privilege separation directory: %s", + _PATH_PRIVSEP_CHROOT_DIR); + +#ifdef HAVE_CYGWIN + if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && + (st.st_uid != getuid () || + (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)) +#else + if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) +#endif + fatal("%s must be owned by root and not group or " + "world-writable.", _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)); + + if (rexec_flag) { + rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *)); + for (i = 0; i < rexec_argc; i++) { + debug("rexec_argv[%d]='%s'", i, saved_argv[i]); + rexec_argv[i] = saved_argv[i]; + } + rexec_argv[rexec_argc] = "-R"; + rexec_argv[rexec_argc + 1] = NULL; + } + + /* Initialize the log (it is reinitialized below in case we forked). */ + if (debug_flag && (!inetd_flag || rexeced_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); + + /* Get a connection, either from inetd or a listening TCP socket */ + if (inetd_flag) { + server_accept_inetd(&sock_in, &sock_out); + + if ((options.protocol & SSH_PROTO_1) && + sensitive_data.server_key == NULL) + generate_ephemeral_server_key(); + } else { + server_listen(); + + if (options.protocol & SSH_PROTO_1) + generate_ephemeral_server_key(); + + signal(SIGHUP, sighup_handler); + signal(SIGCHLD, main_sigchld_handler); + signal(SIGTERM, sigterm_handler); + signal(SIGQUIT, sigterm_handler); + + /* + * Write out the pid file after the sigterm handler + * is setup and the listen sockets are bound + */ + if (!debug_flag) { + FILE *f = fopen(options.pid_file, "w"); + + if (f == NULL) { + error("Couldn't create pid file \"%s\": %s", + options.pid_file, strerror(errno)); + } else { + fprintf(f, "%ld\n", (long) getpid()); + fclose(f); + } + } + + /* Accept a connection and return in a forked child */ + server_accept_loop(&sock_in, &sock_out, + &newsock, config_s); + } + + /* This is the child processing a new connection. */ + setproctitle("%s", "[accepted]"); + + /* + * 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 !defined(SSHD_ACQUIRES_CTTY) + /* + * If setsid is called, on some platforms sshd will later acquire a + * controlling terminal which will result in "could not set + * controlling tty" errors. + */ + if (!debug_flag && !inetd_flag && setsid() < 0) + error("setsid: %.100s", strerror(errno)); +#endif + + if (rexec_flag) { + int fd; + + debug("rexec start in %d out %d newsock %d pipe %d sock %d", + sock_in, sock_out, newsock, startup_pipe, config_s[0]); + dup2(newsock, STDIN_FILENO); + dup2(STDIN_FILENO, STDOUT_FILENO); + if (startup_pipe == -1) + close(REEXEC_STARTUP_PIPE_FD); + else + dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD); + + dup2(config_s[1], REEXEC_CONFIG_PASS_FD); + close(config_s[1]); + if (startup_pipe != -1) + close(startup_pipe); + + execv(rexec_argv[0], rexec_argv); + + /* Reexec has failed, fall back and continue */ + error("rexec of %s failed: %s", rexec_argv[0], strerror(errno)); + recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL); + log_init(__progname, options.log_level, + options.log_facility, log_stderr); + + /* Clean up fds */ + startup_pipe = REEXEC_STARTUP_PIPE_FD; + close(config_s[1]); + close(REEXEC_CONFIG_PASS_FD); + newsock = sock_out = sock_in = dup(STDIN_FILENO); + if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { + dup2(fd, STDIN_FILENO); + dup2(fd, STDOUT_FILENO); + if (fd > STDERR_FILENO) + close(fd); + } + debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d", + sock_in, sock_out, newsock, startup_pipe, config_s[0]); + } + + /* + * 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); + + /* + * Register our connection. This turns encryption off because we do + * not have a key. + */ + packet_set_connection(sock_in, sock_out); + packet_set_server(); + + /* Set SO_KEEPALIVE if requested. */ + if (options.tcp_keep_alive && packet_connection_is_on_socket() && + setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0) + error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); + + if ((remote_port = get_remote_port()) < 0) { + debug("get_remote_port failed"); + cleanup_exit(255); + } + + /* + * We use get_canonical_hostname with usedns = 0 instead of + * get_remote_ipaddr here so IP options will be checked. + */ + (void) get_canonical_hostname(0); + /* + * The rest of the code depends on the fact that + * get_remote_ipaddr() caches the remote ip, even if + * the socket goes away. + */ + remote_ip = get_remote_ipaddr(); + +#ifdef SSH_AUDIT_EVENTS + audit_connection_from(remote_ip, remote_port); +#endif +#ifdef LIBWRAP + /* Check whether logins are denied from this host. */ + if (packet_connection_is_on_socket()) { + 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); + + packet_set_nonblocking(); + + /* allocate authentication context */ + authctxt = xcalloc(1, sizeof(*authctxt)); + + authctxt->loginmsg = &loginmsg; + + /* XXX global for cleanup, access from other modules */ + the_authctxt = authctxt; + + /* prepare buffer to collect messages to display to user after login */ + buffer_init(&loginmsg); + + if (use_privsep) + if (privsep_preauth(authctxt) == 1) + goto authenticated; + + /* perform the key exchange */ + /* authenticate user and start session */ + if (compat20) { + do_ssh2_kex(); + do_authentication2(authctxt); + } else { + do_ssh1_kex(); + do_authentication(authctxt); + } + /* + * If we use privilege separation, the unprivileged child transfers + * the current keystate and exits + */ + if (use_privsep) { + mm_send_keystate(pmonitor); + exit(0); + } + + authenticated: + /* + * Cancel the alarm we set to limit the time taken for + * authentication. + */ + alarm(0); + signal(SIGALRM, SIG_DFL); + authctxt->authenticated = 1; + if (startup_pipe != -1) { + close(startup_pipe); + startup_pipe = -1; + } + +#ifdef SSH_AUDIT_EVENTS + audit_event(SSH_AUTH_SUCCESS); +#endif + + /* + * 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(); + } + + /* Start session. */ + do_authenticated(authctxt); + + /* The connection has been terminated. */ + verbose("Closing connection to %.100s", remote_ip); + +#ifdef USE_PAM + if (options.use_pam) + finish_pam(); +#endif /* USE_PAM */ + +#ifdef SSH_AUDIT_EVENTS + PRIVSEP(audit_event(SSH_CONNECTION_CLOSE)); +#endif + + 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 rnd = 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) + rnd = arc4random(); + cookie[i] = rnd & 0xff; + rnd >>= 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_rsa_authentication) + auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; + if (options.rsa_authentication) + auth_mask |= 1 << SSH_AUTH_RSA; + 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) { + (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8); + len = BN_num_bytes(session_key_int); + if (len < 0 || (u_int)len > sizeof(session_key)) { + error("do_ssh1_kex: 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); + + derive_ssh1_session_id( + sensitive_data.ssh1_host_key->rsa->n, + sensitive_data.server_key->rsa->n, + cookie, session_id); + /* + * 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; + + logit("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 == COMP_NONE) { + myproposal[PROPOSAL_COMP_ALGS_CTOS] = + myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; + } else if (options.compression == COMP_DELAYED) { + myproposal[PROPOSAL_COMP_ALGS_CTOS] = + myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com"; + } + + myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types(); + + /* start key exchange */ + kex = kex_setup(myproposal); + kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; + kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server; + kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; + kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; + 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"); +} + +/* server specific fatal cleanup */ +void +cleanup_exit(int i) +{ + if (the_authctxt) + do_cleanup(the_authctxt); +#ifdef SSH_AUDIT_EVENTS + /* done after do_cleanup so it can cancel the PAM auth 'thread' */ + if (!use_privsep || mm_is_monitor()) + audit_event(SSH_CONNECTION_ABANDON); +#endif + _exit(i); +} |
