diff options
Diffstat (limited to 'crypto/openssh/sshd.c')
| -rw-r--r-- | crypto/openssh/sshd.c | 1345 |
1 files changed, 0 insertions, 1345 deletions
diff --git a/crypto/openssh/sshd.c b/crypto/openssh/sshd.c deleted file mode 100644 index 0d62320a11837..0000000000000 --- a/crypto/openssh/sshd.c +++ /dev/null @@ -1,1345 +0,0 @@ -/* - * Author: Tatu Ylonen <ylo@cs.hut.fi> - * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland - * All rights reserved - * Created: Fri Mar 17 17:09:28 1995 ylo - * 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. - * - * SSH2 implementation, - * Copyright (c) 2000 Markus Friedl. All rights reserved. - */ - -#include "includes.h" -RCSID("$OpenBSD: sshd.c,v 1.115 2000/05/03 10:21:49 markus Exp $"); - -#include "xmalloc.h" -#include "rsa.h" -#include "ssh.h" -#include "pty.h" -#include "packet.h" -#include "cipher.h" -#include "mpaux.h" -#include "servconf.h" -#include "uidswap.h" -#include "compat.h" -#include "buffer.h" - -#include "ssh2.h" -#include <openssl/dh.h> -#include <openssl/bn.h> -#include <openssl/hmac.h> -#include "kex.h" -#include <openssl/dsa.h> -#include <openssl/rsa.h> -#include "key.h" -#include "dsa.h" - -#include "auth.h" -#include "myproposal.h" -#include "authfile.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 - -/* Server configuration options. */ -ServerOptions options; - -/* Name of the server configuration file. */ -char *config_file_name = 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. - */ -int IPv4or6 = AF_UNSPEC; - -/* - * 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 is being started from inetd. */ -int inetd_flag = 0; - -/* debug goes to stderr unless inetd_flag is set */ -int log_stderr = 0; - -/* argv[0] without path. */ -char *av0; - -/* Saved arguments to main(). */ -char **saved_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; - -/* - * 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 { - RSA *private_key; /* Private part of empheral server key. */ - RSA *host_key; /* Private part of host key. */ - Key *dsa_host_key; /* Private DSA host key. */ -} sensitive_data; - -/* - * Flag indicating whether the current session key has been used. This flag - * is set whenever the key is used, and cleared when the key is regenerated. - */ -int key_used = 0; - -/* This is set to true when SIGHUP is received. */ -int received_sighup = 0; - -/* Public side of the server key. This value is regenerated regularly with - the private key. */ -RSA *public_key; - -/* session identifier, used by RSA-auth */ -unsigned char session_id[16]; - -/* same for ssh2 */ -unsigned char *session_id2 = NULL; -int session_id2_len = 0; - -/* Prototypes for various functions defined later in this file. */ -void do_ssh1_kex(); -void do_ssh2_kex(); - -/* - * Close all listening sockets - */ -void -close_listen_socks(void) -{ - int i; - for (i = 0; i < num_listen_socks; i++) - close(listen_socks[i]); - num_listen_socks = -1; -} - -/* - * 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). - */ -void -sighup_handler(int sig) -{ - received_sighup = 1; - signal(SIGHUP, sighup_handler); -} - -/* - * Called from the main program after receiving SIGHUP. - * Restarts the server. - */ -void -sighup_restart() -{ - log("Received SIGHUP; restarting."); - close_listen_socks(); - execv(saved_argv[0], saved_argv); - log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno)); - exit(1); -} - -/* - * Generic signal handler for terminating signals in the master daemon. - * These close the listen socket; not closing it seems to cause "Address - * already in use" problems on some machines, which is inconvenient. - */ -void -sigterm_handler(int sig) -{ - log("Received signal %d; terminating.", sig); - close_listen_socks(); - unlink(options.pid_file); - exit(255); -} - -/* - * SIGCHLD handler. This is called whenever a child dies. This will then - * reap any zombies left by exited c. - */ -void -main_sigchld_handler(int sig) -{ - int save_errno = errno; - int status; - - while (waitpid(-1, &status, WNOHANG) > 0) - ; - - signal(SIGCHLD, main_sigchld_handler); - errno = save_errno; -} - -/* - * Signal handler for the alarm after the login grace period has expired. - */ -void -grace_alarm_handler(int sig) -{ - /* 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. - */ -/* XXX do we really want this work to be done in a signal handler ? -m */ -void -key_regeneration_alarm(int sig) -{ - int save_errno = errno; - - /* Check if we should generate a new key. */ - if (key_used) { - /* This should really be done in the background. */ - log("Generating new %d bit RSA key.", options.server_key_bits); - - if (sensitive_data.private_key != NULL) - RSA_free(sensitive_data.private_key); - sensitive_data.private_key = RSA_new(); - - if (public_key != NULL) - RSA_free(public_key); - public_key = RSA_new(); - - rsa_generate_key(sensitive_data.private_key, public_key, - options.server_key_bits); - arc4random_stir(); - key_used = 0; - log("RSA key generation complete."); - } - /* Reschedule the alarm. */ - signal(SIGALRM, key_regeneration_alarm); - alarm(options.key_regeneration_time); - errno = save_errno; -} - -char * -chop(char *s) -{ - char *t = s; - while (*t) { - if(*t == '\n' || *t == '\r') { - *t = '\0'; - return s; - } - t++; - } - return s; - -} - -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 side\'s version identification. */ - for (i = 0; i < sizeof(buf) - 1; i++) { - if (read(sock_in, &buf[i], 1) != 1) { - log("Did not receive ident string from %s.", get_remote_ipaddr()); - fatal_cleanup(); - } - if (buf[i] == '\r') { - buf[i] = '\n'; - buf[i + 1] = 0; - continue; - } - if (buf[i] == '\n') { - /* buf[i] == '\n' */ - buf[i + 1] = 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); - - 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); - chop(client_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(); - } - if (compat20) - packet_set_ssh2_format(); -} - - -void -destroy_sensitive_data(void) -{ - /* Destroy the private and public keys. They will no longer be needed. */ - RSA_free(public_key); - RSA_free(sensitive_data.private_key); - RSA_free(sensitive_data.host_key); - if (sensitive_data.dsa_host_key != NULL) - key_free(sensitive_data.dsa_host_key); -} - -/* - * 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, i, fdsetsz, on = 1; - pid_t pid; - socklen_t fromlen; - int silent = 0; - 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; - - /* Save argv[0]. */ - saved_argv = av; - if (strchr(av[0], '/')) - av0 = strrchr(av[0], '/') + 1; - else - av0 = av[0]; - - /* 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:diqQ46")) != EOF) { - switch (opt) { - case '4': - IPv4or6 = AF_INET; - break; - case '6': - IPv4or6 = AF_INET6; - break; - case 'f': - config_file_name = optarg; - break; - case 'd': - debug_flag = 1; - options.log_level = SYSLOG_LEVEL_DEBUG; - break; - case 'i': - inetd_flag = 1; - break; - case 'Q': - silent = 1; - 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) - fatal("too many ports.\n"); - options.ports[options.num_ports++] = atoi(optarg); - break; - case 'g': - options.login_grace_time = atoi(optarg); - break; - case 'k': - options.key_regeneration_time = atoi(optarg); - break; - case 'h': - options.host_key_file = optarg; - break; - case 'V': - client_version_string = optarg; - /* only makes sense with inetd_flag, i.e. no listen() */ - inetd_flag = 1; - break; - case '?': - default: - fprintf(stderr, "sshd version %s\n", SSH_VERSION); - fprintf(stderr, "Usage: %s [options]\n", av0); - fprintf(stderr, "Options:\n"); - fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE); - fprintf(stderr, " -d Debugging mode\n"); - fprintf(stderr, " -i Started from inetd\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: 300)\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", - HOST_KEY_FILE); - fprintf(stderr, " -4 Use IPv4 only\n"); - fprintf(stderr, " -6 Use IPv6 only\n"); - exit(1); - } - } - - /* - * Force logging to stderr until we have loaded the private host - * key (unless started from inetd) - */ - log_init(av0, - options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level, - options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility, - !silent && !inetd_flag); - - /* 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); - - sensitive_data.dsa_host_key = NULL; - sensitive_data.host_key = NULL; - - /* check if RSA support exists */ - if ((options.protocol & SSH_PROTO_1) && - rsa_alive() == 0) { - log("no RSA support in libssl and libcrypto. See ssl(8)"); - log("Disabling protocol version 1"); - options.protocol &= ~SSH_PROTO_1; - } - /* Load the RSA/DSA host key. It must have empty passphrase. */ - if (options.protocol & SSH_PROTO_1) { - Key k; - sensitive_data.host_key = RSA_new(); - k.type = KEY_RSA; - k.rsa = sensitive_data.host_key; - errno = 0; - if (!load_private_key(options.host_key_file, "", &k, NULL)) { - error("Could not load host key: %.200s: %.100s", - options.host_key_file, strerror(errno)); - log("Disabling protocol version 1"); - options.protocol &= ~SSH_PROTO_1; - } - k.rsa = NULL; - } - if (options.protocol & SSH_PROTO_2) { - sensitive_data.dsa_host_key = key_new(KEY_DSA); - if (!load_private_key(options.host_dsa_key_file, "", sensitive_data.dsa_host_key, NULL)) { - - error("Could not load DSA host key: %.200s", options.host_dsa_key_file); - log("Disabling protocol version 2"); - options.protocol &= ~SSH_PROTO_2; - } - } - if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) { - if (silent == 0) - fprintf(stderr, "sshd: no hostkeys available -- exiting.\n"); - log("sshd: no hostkeys available -- exiting.\n"); - 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.host_key->n) - SSH_KEY_BITS_RESERVED && - options.server_key_bits < - BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) { - options.server_key_bits = - BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED; - debug("Forcing server key to %d bits to make it differ from host key.", - options.server_key_bits); - } - } - - /* Initialize the log (it is reinitialized below in case we forked). */ - if (debug_flag && !inetd_flag) - log_stderr = 1; - log_init(av0, 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) { -#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("/dev/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(av0, options.log_level, options.log_facility, log_stderr); - - /* Do not display messages to stdout in RSA code. */ - rsa_set_verbose(0); - - /* Initialize the random number generator. */ - arc4random_stir(); - - /* Chdir to the root directory so that the current disk can be - unmounted if desired. */ - chdir("/"); - - /* Start listening for a socket, unless started from inetd. */ - if (inetd_flag) { - int s1, s2; - s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */ - s2 = dup(s1); - sock_in = dup(0); - sock_out = dup(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) { - public_key = RSA_new(); - sensitive_data.private_key = RSA_new(); - log("Generating %d bit RSA key.", options.server_key_bits); - rsa_generate_key(sensitive_data.private_key, public_key, - options.server_key_bits); - arc4random_stir(); - log("RSA key generation complete."); - } - } 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, - (void *) &on, sizeof(on)); - linger.l_onoff = 1; - linger.l_linger = 5; - setsockopt(listen_sock, SOL_SOCKET, SO_LINGER, - (void *) &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) { - 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 (!debug_flag) { - /* - * Record our pid in /etc/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, "w"); - if (f) { - fprintf(f, "%u\n", (unsigned int) getpid()); - fclose(f); - } - } - if (options.protocol & SSH_PROTO_1) { - public_key = RSA_new(); - sensitive_data.private_key = RSA_new(); - - log("Generating %d bit RSA key.", options.server_key_bits); - rsa_generate_key(sensitive_data.private_key, public_key, - options.server_key_bits); - arc4random_stir(); - log("RSA key generation complete."); - - /* Schedule server key regeneration alarm. */ - signal(SIGALRM, key_regeneration_alarm); - alarm(options.key_regeneration_time); - } - - /* 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); - - /* setup fd set for listen */ - maxfd = 0; - for (i = 0; i < num_listen_socks; i++) - if (listen_socks[i] > maxfd) - maxfd = listen_socks[i]; - fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask); - fdset = (fd_set *)xmalloc(fdsetsz); - - /* - * Stay listening for connections until the system crashes or - * the daemon is killed with a signal. - */ - for (;;) { - if (received_sighup) - sighup_restart(); - /* Wait in select until there is a connection. */ - memset(fdset, 0, fdsetsz); - for (i = 0; i < num_listen_socks; i++) - FD_SET(listen_socks[i], fdset); - if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) { - if (errno != EINTR) - error("select: %.100s", strerror(errno)); - continue; - } - 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)); - continue; - } - /* - * 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; - 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 socket, and start using the - * accepted socket. Reinitialize logging (since our pid has - * changed). We break out of the loop to handle the connection. - */ - close_listen_socks(); - sock_in = newsock; - sock_out = newsock; - log_init(av0, 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 %d.", pid); - - /* Mark that the key has been used (it was "given" to the child). */ - key_used = 1; - - arc4random_stir(); - - /* Close the new socket (the child is now taking care of it). */ - close(newsock); - } /* for (i = 0; i < num_listen_socks; i++) */ - /* child process check (or debug mode) */ - if (num_listen_socks < 0) - break; - } - } - - /* This is the child processing a new connection. */ - - /* - * 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); - - /* - * 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, (void *) &linger, sizeof(linger)); - - /* - * 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(); - - /* Check whether logins are denied from this host. */ -#ifdef LIBWRAP - /* XXX LIBWRAP noes not know about IPv6 */ - { - struct request_info req; - - request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL); - fromhost(&req); - - if (!hosts_access(&req)) { - close(sock_in); - close(sock_out); - refuse(&req); - } -/*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */ - } -#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- - * and Rhosts-RSA-Authentication only make sense from priviledged - * 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 (remote_port >= IPPORT_RESERVED || - remote_port < IPPORT_RESERVED / 2) { - options.rhosts_authentication = 0; - options.rhosts_rsa_authentication = 0; - } -#ifdef KRB4 - if (!packet_connection_is_ipv4() && - options.kerberos_authentication) { - debug("Kerberos Authentication disabled, only available for IPv4."); - options.kerberos_authentication = 0; - } -#endif /* KRB4 */ - - packet_set_nonblocking(); - - /* perform the key exchange */ - /* authenticate user and start session */ - if (compat20) { - do_ssh2_kex(); - do_authentication2(); - } else { - do_ssh1_kex(); - do_authentication(); - } - -#ifdef KRB4 - /* Cleanup user's ticket cache file. */ - if (options.kerberos_ticket_cleanup) - (void) dest_tkt(); -#endif /* KRB4 */ - - /* The connection has been terminated. */ - verbose("Closing connection to %.100s", remote_ip); - packet_close(); - exit(0); -} - -/* - * SSH1 key exchange - */ -void -do_ssh1_kex() -{ - int i, len; - int plen, slen; - BIGNUM *session_key_int; - unsigned char session_key[SSH_SESSION_KEY_LENGTH]; - unsigned char cookie[8]; - unsigned 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(public_key->n)); - packet_put_bignum(public_key->e); - packet_put_bignum(public_key->n); - - /* Store our public host RSA key. */ - packet_put_int(BN_num_bits(sensitive_data.host_key->n)); - packet_put_bignum(sensitive_data.host_key->e); - packet_put_bignum(sensitive_data.host_key->n); - - /* Put protocol flags. */ - packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); - - /* Declare which ciphers we support. */ - packet_put_int(cipher_mask1()); - - /* 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; -#ifdef KRB4 - if (options.kerberos_authentication) - auth_mask |= 1 << SSH_AUTH_KERBEROS; -#endif -#ifdef AFS - if (options.kerberos_tgt_passing) - auth_mask |= 1 << SSH_PASS_KERBEROS_TGT; - if (options.afs_token_passing) - auth_mask |= 1 << SSH_PASS_AFS_TOKEN; -#endif -#ifdef SKEY - if (options.skey_authentication == 1) - auth_mask |= 1 << SSH_AUTH_TIS; -#endif - 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 public key and %d bit host key.", - BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n)); - - /* Read clients reply (cipher type and session key). */ - packet_read_expect(&plen, SSH_CMSG_SESSION_KEY); - - /* Get cipher type and check whether we accept this. */ - cipher_type = packet_get_char(); - - if (!(cipher_mask() & (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. */ - session_key_int = BN_new(); - packet_get_bignum(session_key_int, &slen); - - protocol_flags = packet_get_int(); - packet_set_protocol_flags(protocol_flags); - - packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY); - - /* - * Decrypt it using our private server key and private host key (key - * with larger modulus first). - */ - if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) { - /* Private key has bigger modulus. */ - if (BN_num_bits(sensitive_data.private_key->n) < - BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) { - fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", - get_remote_ipaddr(), - BN_num_bits(sensitive_data.private_key->n), - BN_num_bits(sensitive_data.host_key->n), - SSH_KEY_BITS_RESERVED); - } - rsa_private_decrypt(session_key_int, session_key_int, - sensitive_data.private_key); - rsa_private_decrypt(session_key_int, session_key_int, - sensitive_data.host_key); - } else { - /* Host key has bigger modulus (or they are equal). */ - if (BN_num_bits(sensitive_data.host_key->n) < - BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) { - fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d", - get_remote_ipaddr(), - BN_num_bits(sensitive_data.host_key->n), - BN_num_bits(sensitive_data.private_key->n), - SSH_KEY_BITS_RESERVED); - } - rsa_private_decrypt(session_key_int, session_key_int, - sensitive_data.host_key); - rsa_private_decrypt(session_key_int, session_key_int, - sensitive_data.private_key); - } - - compute_session_id(session_id, cookie, - sensitive_data.host_key->n, - sensitive_data.private_key->n); - - /* Destroy the private and public keys. They will no longer be needed. */ - destroy_sensitive_data(); - - /* - * 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. - */ - BN_mask_bits(session_key_int, sizeof(session_key) * 8); - len = BN_num_bytes(session_key_int); - if (len < 0 || len > sizeof(session_key)) - fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d", - get_remote_ipaddr(), - len, sizeof(session_key)); - memset(session_key, 0, sizeof(session_key)); - BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len); - - /* Destroy the decrypted integer. It is no longer needed. */ - BN_clear_free(session_key_int); - - /* 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]; - - /* 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 acknowledgement 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 - */ -void -do_ssh2_kex() -{ - Buffer *server_kexinit; - Buffer *client_kexinit; - int payload_len, dlen; - int slen; - unsigned int klen, kout; - char *ptr; - unsigned char *signature = NULL; - unsigned char *server_host_key_blob = NULL; - unsigned int sbloblen; - DH *dh; - BIGNUM *dh_client_pub = 0; - BIGNUM *shared_secret = 0; - int i; - unsigned char *kbuf; - unsigned char *hash; - Kex *kex; - char *cprop[PROPOSAL_MAX]; - char *sprop[PROPOSAL_MAX]; - -/* KEXINIT */ - - if (options.ciphers != NULL) { - myproposal[PROPOSAL_ENC_ALGS_CTOS] = - myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; - } - - debug("Sending KEX init."); - - for (i = 0; i < PROPOSAL_MAX; i++) - sprop[i] = xstrdup(myproposal[i]); - server_kexinit = kex_init(sprop); - packet_start(SSH2_MSG_KEXINIT); - packet_put_raw(buffer_ptr(server_kexinit), buffer_len(server_kexinit)); - packet_send(); - packet_write_wait(); - - debug("done"); - - packet_read_expect(&payload_len, SSH2_MSG_KEXINIT); - - /* - * save raw KEXINIT payload in buffer. this is used during - * computation of the session_id and the session keys. - */ - client_kexinit = xmalloc(sizeof(*client_kexinit)); - buffer_init(client_kexinit); - ptr = packet_get_raw(&payload_len); - buffer_append(client_kexinit, ptr, payload_len); - - /* skip cookie */ - for (i = 0; i < 16; i++) - (void) packet_get_char(); - /* save kex init proposal strings */ - for (i = 0; i < PROPOSAL_MAX; i++) { - cprop[i] = packet_get_string(NULL); - debug("got kexinit string: %s", cprop[i]); - } - - i = (int) packet_get_char(); - debug("first kex follow == %d", i); - i = packet_get_int(); - debug("reserved == %d", i); - - debug("done read kexinit"); - kex = kex_choose_conf(cprop, sprop, 1); - -/* KEXDH */ - - debug("Wait SSH2_MSG_KEXDH_INIT."); - packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT); - - /* key, cert */ - dh_client_pub = BN_new(); - if (dh_client_pub == NULL) - fatal("dh_client_pub == NULL"); - packet_get_bignum2(dh_client_pub, &dlen); - -#ifdef DEBUG_KEXDH - fprintf(stderr, "\ndh_client_pub= "); - bignum_print(dh_client_pub); - fprintf(stderr, "\n"); - debug("bits %d", BN_num_bits(dh_client_pub)); -#endif - - /* generate DH key */ - dh = dh_new_group1(); /* XXX depends on 'kex' */ - -#ifdef DEBUG_KEXDH - fprintf(stderr, "\np= "); - bignum_print(dh->p); - fprintf(stderr, "\ng= "); - bignum_print(dh->g); - fprintf(stderr, "\npub= "); - bignum_print(dh->pub_key); - fprintf(stderr, "\n"); -#endif - if (!dh_pub_is_valid(dh, dh_client_pub)) - packet_disconnect("bad client public DH value"); - - klen = DH_size(dh); - kbuf = xmalloc(klen); - kout = DH_compute_key(kbuf, dh_client_pub, dh); - -#ifdef DEBUG_KEXDH - debug("shared secret: len %d/%d", klen, kout); - fprintf(stderr, "shared secret == "); - for (i = 0; i< kout; i++) - fprintf(stderr, "%02x", (kbuf[i])&0xff); - fprintf(stderr, "\n"); -#endif - shared_secret = BN_new(); - - BN_bin2bn(kbuf, kout, shared_secret); - memset(kbuf, 0, klen); - xfree(kbuf); - - /* XXX precompute? */ - dsa_make_key_blob(sensitive_data.dsa_host_key, &server_host_key_blob, &sbloblen); - - /* calc H */ /* XXX depends on 'kex' */ - hash = kex_hash( - client_version_string, - server_version_string, - buffer_ptr(client_kexinit), buffer_len(client_kexinit), - buffer_ptr(server_kexinit), buffer_len(server_kexinit), - (char *)server_host_key_blob, sbloblen, - dh_client_pub, - dh->pub_key, - shared_secret - ); - buffer_free(client_kexinit); - buffer_free(server_kexinit); - xfree(client_kexinit); - xfree(server_kexinit); -#ifdef DEBUG_KEXDH - fprintf(stderr, "hash == "); - for (i = 0; i< 20; i++) - fprintf(stderr, "%02x", (hash[i])&0xff); - fprintf(stderr, "\n"); -#endif - /* save session id := H */ - /* XXX hashlen depends on KEX */ - session_id2_len = 20; - session_id2 = xmalloc(session_id2_len); - memcpy(session_id2, hash, session_id2_len); - - /* sign H */ - /* XXX hashlen depends on KEX */ - dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20); - - destroy_sensitive_data(); - - /* send server hostkey, DH pubkey 'f' and singed H */ - packet_start(SSH2_MSG_KEXDH_REPLY); - packet_put_string((char *)server_host_key_blob, sbloblen); - packet_put_bignum2(dh->pub_key); /* f */ - packet_put_string((char *)signature, slen); - packet_send(); - xfree(signature); - xfree(server_host_key_blob); - packet_write_wait(); - - kex_derive_keys(kex, hash, shared_secret); - packet_set_kex(kex); - - /* have keys, free DH */ - DH_free(dh); - - debug("send SSH2_MSG_NEWKEYS."); - packet_start(SSH2_MSG_NEWKEYS); - packet_send(); - packet_write_wait(); - debug("done: send SSH2_MSG_NEWKEYS."); - - debug("Wait SSH2_MSG_NEWKEYS."); - packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS); - debug("GOT SSH2_MSG_NEWKEYS."); - -#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("done: KEX2."); -} |