diff options
Diffstat (limited to 'sshd.c')
| -rw-r--r-- | sshd.c | 2445 |
1 files changed, 2445 insertions, 0 deletions
@@ -0,0 +1,2445 @@ +/* + +sshd.c + +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. + +*/ + +#include "includes.h" +RCSID("$Id: sshd.c,v 1.1 1999/10/27 03:42:46 damien Exp $"); + +#include "xmalloc.h" +#include "rsa.h" +#include "ssh.h" +#include "pty.h" +#include "packet.h" +#include "buffer.h" +#include "cipher.h" +#include "mpaux.h" +#include "servconf.h" +#include "uidswap.h" +#include "compat.h" + +#ifdef LIBWRAP +#include <tcpd.h> +#include <syslog.h> +int allow_severity = LOG_INFO; +int deny_severity = LOG_WARNING; +#endif /* LIBWRAP */ + +#ifndef O_NOCTTY +#define O_NOCTTY 0 +#endif + +#ifdef KRB4 +char *ticket = NULL; +#endif /* KRB4 */ + +#ifdef HAVE_PAM +#include <security/pam_appl.h> +struct pam_handle_t *pamh=NULL; +char *pampasswd=NULL; +int retval; +int origretval; +#endif /* HAVE_PAM */ + +/* Local Xauthority file. */ +char *xauthfile = NULL; + +/* Server configuration options. */ +ServerOptions options; + +/* Name of the server configuration file. */ +char *config_file_name = 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 is being started from inetd. */ +int inetd_flag = 0; + +/* argv[0] without path. */ +char *av0; + +/* Saved arguments to main(). */ +char **saved_argv; + +/* This is set to the socket that the server is listening; this is used in + the SIGHUP signal handler. */ +int listen_sock; + +/* Flags set in auth-rsa from authorized_keys flags. These are set in + auth-rsa.c. */ +int no_port_forwarding_flag = 0; +int no_agent_forwarding_flag = 0; +int no_x11_forwarding_flag = 0; +int no_pty_flag = 0; +char *forced_command = NULL; /* RSA authentication "command=" option. */ +struct envstring *custom_environment = NULL; + /* RSA authentication "environment=" options. */ + +/* Session id for the current session. */ +unsigned char session_id[16]; + +/* 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 +{ + /* Private part of server key. */ + RSA *private_key; + + /* Private part of host key. */ + RSA *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; + +/* Prototypes for various functions defined later in this file. */ +void do_connection(int privileged_port); +void do_authentication(char *user, int privileged_port); +void do_authenticated(struct passwd *pw); +void do_exec_pty(const char *command, int ptyfd, int ttyfd, + const char *ttyname, struct passwd *pw, const char *term, + const char *display, const char *auth_proto, + const char *auth_data); +void do_exec_no_pty(const char *command, struct passwd *pw, + const char *display, const char *auth_proto, + const char *auth_data); +void do_child(const char *command, struct passwd *pw, const char *term, + const char *display, const char *auth_proto, + const char *auth_data, const char *ttyname); +#ifdef HAVE_PAM +static int pamconv(int num_msg, const struct pam_message **msg, + struct pam_response **resp, void *appdata_ptr); + +static struct pam_conv conv = { + pamconv, + NULL +}; + +static int pamconv(int num_msg, const struct pam_message **msg, + struct pam_response **resp, void *appdata_ptr) +{ + int count = 0; + int replies = 0; + struct pam_response *reply = NULL; + int size = sizeof(struct pam_response); + + for(count = 0; count < num_msg; count++) + { + switch (msg[count]->msg_style) + { + case PAM_PROMPT_ECHO_ON: + case PAM_PROMPT_ECHO_OFF: + if (reply == NULL) + reply = xmalloc(size); + else + reply = realloc(reply, size); + + if (reply == NULL) + return PAM_CONV_ERR; + + size += sizeof(struct pam_response); + + reply[replies].resp_retcode = PAM_SUCCESS; + + reply[replies++].resp = xstrdup(pampasswd); + /* PAM frees resp */ + break; + + case PAM_TEXT_INFO: + /* ignore it... */ + break; + + case PAM_ERROR_MSG: + default: + /* Must be an error of some sort... */ + if (reply != NULL) + free(reply); + + return PAM_CONV_ERR; + } + } + + if (reply != NULL) + *resp = reply; + + return PAM_SUCCESS; +} + +void pam_cleanup_proc(void *context) +{ + if (retval == PAM_SUCCESS) + retval = pam_close_session((pam_handle_t *)pamh, 0); + + if (pam_end((pam_handle_t *)pamh, retval) != PAM_SUCCESS) + log("Cannot release PAM authentication."); +} +#endif /* HAVE_PAM */ + +/* 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_sock); + 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_sock); + 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; + wait(&status); + 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."); +} + +/* 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. */ + +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; +} + +/* Main program for the daemon. */ + +int +main(int ac, char **av) +{ + extern char *optarg; + extern int optind; + int opt, aux, sock_in, sock_out, newsock, i, pid, on = 1; + int remote_major, remote_minor; + int silentrsa = 0; + struct sockaddr_in sin; + char buf[100]; /* Must not be larger than remote_version. */ + char remote_version[100]; /* Must be at least as big as buf. */ + char *comment; + FILE *f; + struct linger linger; + + /* 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:diqQ")) != EOF) + { + switch (opt) + { + case 'f': + config_file_name = optarg; + break; + case 'd': + debug_flag = 1; + break; + case 'i': + inetd_flag = 1; + break; + case 'Q': + silentrsa = 1; + break; + case 'q': + options.quiet_mode = 1; + break; + case 'b': + options.server_key_bits = atoi(optarg); + break; + case 'p': + options.port = 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 '?': + 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/sshd_config)\n", ETCDIR); + 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); + exit(1); + } + } + + /* check if RSA support exists */ + if (rsa_alive() == 0) { + if (silentrsa == 0) + printf("sshd: no RSA support in libssl and libcrypto -- exiting. See ssl(8)\n"); + log("no RSA support in libssl and libcrypto -- exiting. See ssl(8)"); + exit(1); + } + + /* 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 certain values for sanity. */ + if (options.server_key_bits < 512 || + options.server_key_bits > 32768) + { + fprintf(stderr, "Bad server key size.\n"); + exit(1); + } + if (options.port < 1 || options.port > 65535) + { + fprintf(stderr, "Bad port number.\n"); + exit(1); + } + + /* Check that there are no remaining arguments. */ + if (optind < ac) + { + fprintf(stderr, "Extra argument %s.\n", av[optind]); + exit(1); + } + + /* Initialize the log (it is reinitialized below in case we forked). */ + log_init(av0, debug_flag && !inetd_flag, + debug_flag || options.fascist_logging, + options.quiet_mode, options.log_facility); + + debug("sshd version %.100s", SSH_VERSION); + + sensitive_data.host_key = RSA_new(); + /* Load the host key. It must have empty passphrase. */ + if (!load_private_key(options.host_key_file, "", + sensitive_data.host_key, &comment)) + { + if (debug_flag) + fprintf(stderr, "Could not load host key: %s: %s\n", + options.host_key_file, strerror(errno)); + else + { + int err = errno; + log_init(av0, !inetd_flag, 1, 0, options.log_facility); + error("Could not load host key: %.200s: %.100s", + options.host_key_file, strerror(err)); + } + exit(1); + } + xfree(comment); + + /* 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, debug_flag && !inetd_flag, + debug_flag || options.fascist_logging, + options.quiet_mode, options.log_facility); + + /* 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); + } + + /* 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("/"); + + /* Close connection cleanly after attack. */ + cipher_attack_detected = packet_disconnect; + + /* 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); + + public_key = RSA_new(); + sensitive_data.private_key = RSA_new(); + /* Generate an rsa key. */ + 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 + { + /* Create socket for listening. */ + listen_sock = socket(AF_INET, SOCK_STREAM, 0); + if (listen_sock < 0) + fatal("socket: %.100s", strerror(errno)); + + /* 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)); + + /* Initialize the socket address. */ + memset(&sin, 0, sizeof(sin)); + sin.sin_family = AF_INET; + sin.sin_addr = options.listen_addr; + sin.sin_port = htons(options.port); + + /* Bind the socket to the desired port. */ + if (bind(listen_sock, (struct sockaddr *)&sin, sizeof(sin)) < 0) + { + error("bind: %.100s", strerror(errno)); + shutdown(listen_sock, SHUT_RDWR); + close(listen_sock); + fatal("Bind to port %d failed.", options.port); + } + + 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(SSH_DAEMON_PID_FILE, "w"); + if (f) + { + fprintf(f, "%u\n", (unsigned int)getpid()); + fclose(f); + } + } + + /* Start listening on the port. */ + log("Server listening on port %d.", options.port); + if (listen(listen_sock, 5) < 0) + fatal("listen: %.100s", strerror(errno)); + + public_key = RSA_new(); + sensitive_data.private_key = RSA_new(); + /* Generate an rsa key. */ + 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); + + /* Stay listening for connections until the system crashes or the + daemon is killed with a signal. */ + for (;;) + { + if (received_sighup) + sighup_restart(); + /* Wait in accept until there is a connection. */ + aux = sizeof(sin); + newsock = accept(listen_sock, (struct sockaddr *)&sin, &aux); + if (received_sighup) + sighup_restart(); + if (newsock < 0) + { + if (errno == EINTR) + continue; + error("accept: %.100s", 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_sock); + 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_sock); + sock_in = newsock; + sock_out = newsock; + log_init(av0, debug_flag && !inetd_flag, + options.fascist_logging || debug_flag, + options.quiet_mode, options.log_facility); + 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); + } + } + + /* 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); + + /* Check whether logins are denied from this host. */ +#ifdef LIBWRAP + { + 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); + } + log("Connection from %.500s port %d", + eval_client(&req), get_remote_port()); + } +#else + /* Log the connection. */ + log("Connection from %.100s port %d", + get_remote_ipaddr(), get_remote_port()); +#endif /* LIBWRAP */ + + /* 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); + + /* Send our protocol version identification. */ + snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", + PROTOCOL_MAJOR, PROTOCOL_MINOR, SSH_VERSION); + if (write(sock_out, buf, strlen(buf)) != strlen(buf)) + fatal("Could not write ident string."); + + /* Read other side\'s version identification. */ + for (i = 0; i < sizeof(buf) - 1; i++) + { + if (read(sock_in, &buf[i], 1) != 1) + fatal("Did not receive ident string."); + if (buf[i] == '\r') + { + buf[i] = '\n'; + buf[i + 1] = 0; + break; + } + if (buf[i] == '\n') + { + /* buf[i] == '\n' */ + buf[i + 1] = 0; + break; + } + } + buf[sizeof(buf) - 1] = 0; + + /* Check that the versions match. In future this might accept several + versions and set appropriate flags to handle them. */ + if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", &remote_major, &remote_minor, + remote_version) != 3) + { + const char *s = "Protocol mismatch.\n"; + (void) write(sock_out, s, strlen(s)); + close(sock_in); + close(sock_out); + fatal("Bad protocol version identification: %.100s", buf); + } + debug("Client protocol version %d.%d; client software version %.100s", + remote_major, remote_minor, remote_version); + if (remote_major != PROTOCOL_MAJOR) + { + const char *s = "Protocol major versions differ.\n"; + (void) write(sock_out, s, strlen(s)); + close(sock_in); + close(sock_out); + fatal("Protocol major versions differ: %d vs. %d", + PROTOCOL_MAJOR, remote_major); + } + + /* Check that the client has sufficiently high software version. */ + if (remote_major == 1 && remote_minor < 3) + packet_disconnect("Your ssh version is too old and is no longer supported. Please install a newer version."); + + if (remote_major == 1 && remote_minor == 3) { + enable_compat13(); + if (strcmp(remote_version, "OpenSSH-1.1") != 0) { + debug("Agent forwarding disabled, remote version is not compatible."); + no_agent_forwarding_flag = 1; + } + } + + packet_set_nonblocking(); + + /* Handle the connection. We pass as argument whether the connection + came from a privileged port. */ + do_connection(get_remote_port() < IPPORT_RESERVED); + +#ifdef KRB4 + /* Cleanup user's ticket cache file. */ + if (options.kerberos_ticket_cleanup) + (void) dest_tkt(); +#endif /* KRB4 */ + + /* Cleanup user's local Xauthority file. */ + if (xauthfile) unlink(xauthfile); + + /* The connection has been terminated. */ + log("Closing connection to %.100s", inet_ntoa(sin.sin_addr)); + +#ifdef HAVE_PAM + if (retval == PAM_SUCCESS) + retval = pam_close_session((pam_handle_t *)pamh, 0); + + if (pam_end((pam_handle_t *)pamh, retval) != PAM_SUCCESS) + log("Cannot release PAM authentication."); + + fatal_remove_cleanup(&pam_cleanup_proc, NULL); +#endif /* HAVE_PAM */ + + packet_close(); + + exit(0); +} + +/* Process an incoming connection. Protocol version identifiers have already + been exchanged. This sends server key and performs the key exchange. + Server and host keys will no longer be needed after this functions. */ + +void do_connection(int privileged_port) +{ + int i; + BIGNUM *session_key_int; + unsigned char session_key[SSH_SESSION_KEY_LENGTH]; + unsigned char check_bytes[8]; + char *user; + unsigned int cipher_type, auth_mask, protocol_flags; + int plen, slen; + 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(); + check_bytes[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(check_bytes[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_mask()); + + /* 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 + 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. */ + cipher_type = packet_get_char(); + + /* 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 (check_bytes[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); + + /* Get protocol flags. */ + 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. */ + assert(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). */ + assert(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 for this session. */ + compute_session_id(session_id, check_bytes, + BN_num_bits(sensitive_data.host_key->n), + sensitive_data.host_key->n, + BN_num_bits(sensitive_data.private_key->n), + sensitive_data.private_key->n); + + /* 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); + assert(BN_num_bytes(session_key_int) == sizeof(session_key)); + BN_bn2bin(session_key_int, session_key); + + /* 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]; + + /* 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, 0); + + /* 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(); + + /* Get the name of the user that we wish to log in as. */ + packet_read_expect(&plen, SSH_CMSG_USER); + + /* Get the user name. */ + { + int ulen; + user = packet_get_string(&ulen); + packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER); + } + + /* 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); + + setproctitle("%s", user); + /* Do the authentication. */ + do_authentication(user, privileged_port); +} + +/* Check if the user is allowed to log in via ssh. If user is listed in + DenyUsers or user's primary group is listed in DenyGroups, false will + be returned. If AllowUsers isn't empty and user isn't listed there, or + if AllowGroups isn't empty and user isn't listed there, false will be + returned. Otherwise true is returned. + XXX This function should also check if user has a valid shell */ + +static int +allowed_user(struct passwd *pw) +{ + struct group *grp; + int i; + + /* Shouldn't be called if pw is NULL, but better safe than sorry... */ + if (!pw) + return 0; + + /* XXX Should check for valid login shell */ + + /* Return false if user is listed in DenyUsers */ + if (options.num_deny_users > 0) + { + if (!pw->pw_name) + return 0; + for (i = 0; i < options.num_deny_users; i++) + if (match_pattern(pw->pw_name, options.deny_users[i])) + return 0; + } + + /* Return false if AllowUsers isn't empty and user isn't listed there */ + if (options.num_allow_users > 0) + { + if (!pw->pw_name) + return 0; + for (i = 0; i < options.num_allow_users; i++) + if (match_pattern(pw->pw_name, options.allow_users[i])) + break; + /* i < options.num_allow_users iff we break for loop */ + if (i >= options.num_allow_users) + return 0; + } + + /* Get the primary group name if we need it. Return false if it fails */ + if (options.num_deny_groups > 0 || options.num_allow_groups > 0 ) + { + grp = getgrgid(pw->pw_gid); + if (!grp) + return 0; + + /* Return false if user's group is listed in DenyGroups */ + if (options.num_deny_groups > 0) + { + if (!grp->gr_name) + return 0; + for (i = 0; i < options.num_deny_groups; i++) + if (match_pattern(grp->gr_name, options.deny_groups[i])) + return 0; + } + + /* Return false if AllowGroups isn't empty and user's group isn't + listed there */ + if (options.num_allow_groups > 0) + { + if (!grp->gr_name) + return 0; + for (i = 0; i < options.num_allow_groups; i++) + if (match_pattern(grp->gr_name, options.allow_groups[i])) + break; + /* i < options.num_allow_groups iff we break for loop */ + if (i >= options.num_allow_groups) + return 0; + } + } + + /* We found no reason not to let this user try to log on... */ + return 1; +} + +/* Performs authentication of an incoming connection. Session key has already + been exchanged and encryption is enabled. User is the user name to log + in as (received from the clinet). Privileged_port is true if the + connection comes from a privileged port (used for .rhosts authentication).*/ + +#define MAX_AUTH_FAILURES 5 + +void +do_authentication(char *user, int privileged_port) +{ + int type; + int authenticated = 0; + int authentication_failures = 0; + char *password; + struct passwd *pw, pwcopy; + char *client_user; + unsigned int client_host_key_bits; + BIGNUM *client_host_key_e, *client_host_key_n; +#ifdef HAVE_PAM + int pam_auth_ok; +#endif /* HAVE_PAM */ + +#ifdef AFS + /* If machine has AFS, set process authentication group. */ + if (k_hasafs()) { + k_setpag(); + k_unlog(); + } +#endif /* AFS */ + + /* Verify that the user is a valid user. */ + pw = getpwnam(user); +#ifdef HAVE_PAM + if ((pw != NULL) && allowed_user(pw)) + { + /* Initialise PAM */ + retval = pam_start("ssh", pw->pw_name, &conv, (pam_handle_t **)&pamh); + fatal_add_cleanup(&pam_cleanup_proc, NULL); + origretval = retval; + if (retval == PAM_SUCCESS) + pam_auth_ok = 1; + } + + if (pam_auth_ok == 0) +#else /* HAVE_PAM */ + if (!pw || !allowed_user(pw)) +#endif /* HAVE_PAM */ + { + /* The user does not exist or access is denied, + but fake indication that authentication is needed. */ + packet_start(SSH_SMSG_FAILURE); + packet_send(); + packet_write_wait(); + + /* Keep reading packets, and always respond with a failure. This is to + avoid disclosing whether such a user really exists. */ + for (;;) + { + /* Read a packet. This will not return if the client disconnects. */ + int plen; + int type = packet_read(&plen); +#ifdef SKEY + int passw_len; + char *password, *skeyinfo; + if (options.password_authentication && + options.skey_authentication == 1 && + type == SSH_CMSG_AUTH_PASSWORD && + (password = packet_get_string(&passw_len)) != NULL && + passw_len == 5 && + strncasecmp(password, "s/key", 5) == 0 && + (skeyinfo = skey_fake_keyinfo(user)) != NULL ){ + /* Send a fake s/key challenge. */ + packet_send_debug(skeyinfo); + } +#endif + /* Send failure. This should be indistinguishable from a failed + authentication. */ + packet_start(SSH_SMSG_FAILURE); + packet_send(); + packet_write_wait(); + if (++authentication_failures >= MAX_AUTH_FAILURES) { + packet_disconnect("Too many authentication failures for %.100s from %.200s", + user, get_canonical_hostname()); + } + } + /*NOTREACHED*/ + abort(); + } + + /* Take a copy of the returned structure. */ + memset(&pwcopy, 0, sizeof(pwcopy)); + pwcopy.pw_name = xstrdup(pw->pw_name); + pwcopy.pw_passwd = xstrdup(pw->pw_passwd); + pwcopy.pw_uid = pw->pw_uid; + pwcopy.pw_gid = pw->pw_gid; + pwcopy.pw_dir = xstrdup(pw->pw_dir); + pwcopy.pw_shell = xstrdup(pw->pw_shell); + pw = &pwcopy; + + /* If we are not running as root, the user must have the same uid as the + server. */ + if (getuid() != 0 && pw->pw_uid != getuid()) + packet_disconnect("Cannot change user when server not running as root."); + + debug("Attempting authentication for %.100s.", user); + + /* If the user has no password, accept authentication immediately. */ + if (options.password_authentication && +#ifdef KRB4 + (!options.kerberos_authentication || options.kerberos_or_local_passwd) && +#endif /* KRB4 */ + auth_password(pw, "")) + { + /* Authentication with empty password succeeded. */ + debug("Login for user %.100s accepted without authentication.", user); + /* authentication_type = SSH_AUTH_PASSWORD; */ + authenticated = 1; + /* Success packet will be sent after loop below. */ + } + else + { + /* Indicate that authentication is needed. */ + packet_start(SSH_SMSG_FAILURE); + packet_send(); + packet_write_wait(); + } + + /* Loop until the user has been authenticated or the connection is closed. */ + while (!authenticated) + { + int plen; + /* Get a packet from the client. */ + type = packet_read(&plen); + + /* Process the packet. */ + switch (type) + { + +#ifdef AFS + case SSH_CMSG_HAVE_KERBEROS_TGT: + if (!options.kerberos_tgt_passing) + { + /* packet_get_all(); */ + log("Kerberos tgt passing disabled."); + break; + } + else { + /* Accept Kerberos tgt. */ + int dlen; + char *tgt = packet_get_string(&dlen); + packet_integrity_check(plen, 4 + dlen, type); + if (!auth_kerberos_tgt(pw, tgt)) + debug("Kerberos tgt REFUSED for %s", user); + xfree(tgt); + } + continue; + + case SSH_CMSG_HAVE_AFS_TOKEN: + if (!options.afs_token_passing || !k_hasafs()) { + /* packet_get_all(); */ + log("AFS token passing disabled."); + break; + } + else { + /* Accept AFS token. */ + int dlen; + char *token_string = packet_get_string(&dlen); + packet_integrity_check(plen, 4 + dlen, type); + if (!auth_afs_token(user, pw->pw_uid, token_string)) + debug("AFS token REFUSED for %s", user); + xfree(token_string); + continue; + } +#endif /* AFS */ + +#ifdef KRB4 + case SSH_CMSG_AUTH_KERBEROS: + if (!options.kerberos_authentication) + { + /* packet_get_all(); */ + log("Kerberos authentication disabled."); + break; + } + else { + /* Try Kerberos v4 authentication. */ + KTEXT_ST auth; + char *tkt_user = NULL; + char *kdata = packet_get_string((unsigned int *)&auth.length); + packet_integrity_check(plen, 4 + auth.length, type); + + if (auth.length < MAX_KTXT_LEN) + memcpy(auth.dat, kdata, auth.length); + xfree(kdata); + + if (auth_krb4(user, &auth, &tkt_user)) { + /* Client has successfully authenticated to us. */ + log("Kerberos authentication accepted %s for account " + "%s from %s", tkt_user, user, get_canonical_hostname()); + /* authentication_type = SSH_AUTH_KERBEROS; */ + authenticated = 1; + xfree(tkt_user); + } + else { + log("Kerberos authentication failed for account " + "%s from %s", user, get_canonical_hostname()); + } + } + break; +#endif /* KRB4 */ + + case SSH_CMSG_AUTH_RHOSTS: + if (!options.rhosts_authentication) + { + log("Rhosts authentication disabled."); + break; + } + + /* Rhosts authentication (also uses /etc/hosts.equiv). */ + if (!privileged_port) + { + log("Rhosts authentication not available for connections from unprivileged port."); + break; + } + + /* Get client user name. Note that we just have to trust the client; + this is one reason why rhosts authentication is insecure. + (Another is IP-spoofing on a local network.) */ + { + int dlen; + client_user = packet_get_string(&dlen); + packet_integrity_check(plen, 4 + dlen, type); + } + + /* Try to authenticate using /etc/hosts.equiv and .rhosts. */ + if (auth_rhosts(pw, client_user, options.ignore_rhosts, + options.strict_modes)) + { + /* Authentication accepted. */ + log("Rhosts authentication accepted for %.100s, remote %.100s on %.700s.", + user, client_user, get_canonical_hostname()); + authenticated = 1; + xfree(client_user); + break; + } + log("Rhosts authentication failed for %.100s, remote %.100s.", + user, client_user); + xfree(client_user); + break; + + case SSH_CMSG_AUTH_RHOSTS_RSA: + if (!options.rhosts_rsa_authentication) + { + log("Rhosts with RSA authentication disabled."); + break; + } + + /* Rhosts authentication (also uses /etc/hosts.equiv) with RSA + host authentication. */ + if (!privileged_port) + { + log("Rhosts authentication not available for connections from unprivileged port."); + break; + } + + { + int ulen, elen, nlen; + /* Get client user name. Note that we just have to trust + the client; root on the client machine can claim to be + any user. */ + client_user = packet_get_string(&ulen); + + /* Get the client host key. */ + client_host_key_e = BN_new(); + client_host_key_n = BN_new(); + client_host_key_bits = packet_get_int(); + packet_get_bignum(client_host_key_e, &elen); + packet_get_bignum(client_host_key_n, &nlen); + + packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type); + } + + /* Try to authenticate using /etc/hosts.equiv and .rhosts. */ + if (auth_rhosts_rsa(pw, client_user, + client_host_key_bits, client_host_key_e, + client_host_key_n, options.ignore_rhosts, + options.strict_modes)) + { + /* Authentication accepted. */ + authenticated = 1; + xfree(client_user); + BN_clear_free(client_host_key_e); + BN_clear_free(client_host_key_n); + break; + } + log("Rhosts authentication failed for %.100s, remote %.100s.", + user, client_user); + xfree(client_user); + BN_clear_free(client_host_key_e); + BN_clear_free(client_host_key_n); + break; + + case SSH_CMSG_AUTH_RSA: + if (!options.rsa_authentication) + { + log("RSA authentication disabled."); + break; + } + + /* RSA authentication requested. */ + { + int nlen; + BIGNUM *n; + n = BN_new(); + packet_get_bignum(n, &nlen); + + packet_integrity_check(plen, nlen, type); + + if (auth_rsa(pw, n, options.strict_modes)) + { + /* Successful authentication. */ + BN_clear_free(n); + log("RSA authentication for %.100s accepted.", user); + authenticated = 1; + break; + } + BN_clear_free(n); + log("RSA authentication for %.100s failed.", user); + } + break; + + case SSH_CMSG_AUTH_PASSWORD: + if (!options.password_authentication) + { + log("Password authentication disabled."); + break; + } + + /* Password authentication requested. */ + /* Read user password. It is in plain text, but was transmitted + over the encrypted channel so it is not visible to an outside + observer. */ + { + int passw_len; + password = packet_get_string(&passw_len); + packet_integrity_check(plen, 4 + passw_len, type); + } + + /* Try authentication with the password. */ + if (auth_password(pw, password)) + { + /* Successful authentication. */ + /* Clear the password from memory. */ + memset(password, 0, strlen(password)); + xfree(password); + log("Password authentication for %.100s accepted.", user); + authenticated = 1; + break; + } + log("Password authentication for %.100s failed.", user); + memset(password, 0, strlen(password)); + xfree(password); + break; + + case SSH_CMSG_AUTH_TIS: + /* TIS Authentication is unsupported */ + log("TIS authentication disabled."); + break; + + default: + /* Any unknown messages will be ignored (and failure returned) + during authentication. */ + log("Unknown message during authentication: type %d", type); + break; /* Respond with a failure message. */ + } + /* If successfully authenticated, break out of loop. */ + if (authenticated) + break; + + /* Send a message indicating that the authentication attempt failed. */ + packet_start(SSH_SMSG_FAILURE); + packet_send(); + packet_write_wait(); + + if (++authentication_failures >= MAX_AUTH_FAILURES) { + packet_disconnect("Too many authentication failures for %.100s from %.200s", + pw->pw_name, get_canonical_hostname()); + } + } + + /* Check if the user is logging in as root and root logins are disallowed. */ + if (pw->pw_uid == 0 && !options.permit_root_login) + { + if (forced_command) + log("Root login accepted for forced command.", forced_command); + else + packet_disconnect("ROOT LOGIN REFUSED FROM %.200s", + get_canonical_hostname()); + } + + /* The user has been authenticated and accepted. */ + packet_start(SSH_SMSG_SUCCESS); + packet_send(); + packet_write_wait(); + + /* Perform session preparation. */ + do_authenticated(pw); +} + +/* Prepares for an interactive session. This is called after the user has + been successfully authenticated. During this message exchange, pseudo + terminals are allocated, X11, TCP/IP, and authentication agent forwardings + are requested, etc. */ + +void do_authenticated(struct passwd *pw) +{ + int type; + int compression_level = 0, enable_compression_after_reply = 0; + int have_pty = 0, ptyfd = -1, ttyfd = -1, xauthfd = -1; + int row, col, xpixel, ypixel, screen; + char ttyname[64]; + char *command, *term = NULL, *display = NULL, *proto = NULL, *data = NULL; + struct group *grp; + gid_t tty_gid; + mode_t tty_mode; + int n_bytes; + + /* Cancel the alarm we set to limit the time taken for authentication. */ + alarm(0); + + /* Inform the channel mechanism that we are the server side and that + the client may request to connect to any port at all. (The user could + do it anyway, and we wouldn\'t know what is permitted except by the + client telling us, so we can equally well trust the client not to request + anything bogus.) */ + channel_permit_all_opens(); + + /* We stay in this loop until the client requests to execute a shell or a + command. */ + while (1) + { + int plen, dlen; + + /* Get a packet from the client. */ + type = packet_read(&plen); + + /* Process the packet. */ + switch (type) + { + case SSH_CMSG_REQUEST_COMPRESSION: + packet_integrity_check(plen, 4, type); + compression_level = packet_get_int(); + if (compression_level < 1 || compression_level > 9) + { + packet_send_debug("Received illegal compression level %d.", + compression_level); + goto fail; + } + /* Enable compression after we have responded with SUCCESS. */ + enable_compression_after_reply = 1; + break; + + case SSH_CMSG_REQUEST_PTY: + if (no_pty_flag) + { + debug("Allocating a pty not permitted for this authentication."); + goto fail; + } + if (have_pty) + packet_disconnect("Protocol error: you already have a pty."); + + debug("Allocating pty."); + + /* Allocate a pty and open it. */ + if (!pty_allocate(&ptyfd, &ttyfd, ttyname)) + { + error("Failed to allocate pty."); + goto fail; + } + + /* Determine the group to make the owner of the tty. */ + grp = getgrnam("tty"); + if (grp) + { + tty_gid = grp->gr_gid; + tty_mode = S_IRUSR|S_IWUSR|S_IWGRP; + } + else + { + tty_gid = pw->pw_gid; + tty_mode = S_IRUSR|S_IWUSR|S_IWGRP|S_IWOTH; + } + + /* Change ownership of the tty. */ + if (chown(ttyname, pw->pw_uid, tty_gid) < 0) + fatal("chown(%.100s, %d, %d) failed: %.100s", + ttyname, pw->pw_uid, tty_gid, strerror(errno)); + if (chmod(ttyname, tty_mode) < 0) + fatal("chmod(%.100s, 0%o) failed: %.100s", + ttyname, tty_mode, strerror(errno)); + + /* Get TERM from the packet. Note that the value may be of arbitrary + length. */ + + term = packet_get_string(&dlen); + packet_integrity_check(dlen, strlen(term), type); + /* packet_integrity_check(plen, 4 + dlen + 4*4 + n_bytes, type); */ + /* Remaining bytes */ + n_bytes = plen - (4 + dlen + 4*4); + + if (strcmp(term, "") == 0) + term = NULL; + + /* Get window size from the packet. */ + row = packet_get_int(); + col = packet_get_int(); + xpixel = packet_get_int(); + ypixel = packet_get_int(); + pty_change_window_size(ptyfd, row, col, xpixel, ypixel); + + /* Get tty modes from the packet. */ + tty_parse_modes(ttyfd, &n_bytes); + packet_integrity_check(plen, 4 + dlen + 4*4 + n_bytes, type); + + /* Indicate that we now have a pty. */ + have_pty = 1; + break; + + case SSH_CMSG_X11_REQUEST_FORWARDING: + if (!options.x11_forwarding) + { + packet_send_debug("X11 forwarding disabled in server configuration file."); + goto fail; + } +#ifdef XAUTH_PATH + if (no_x11_forwarding_flag) + { + packet_send_debug("X11 forwarding not permitted for this authentication."); + goto fail; + } + debug("Received request for X11 forwarding with auth spoofing."); + if (display) + packet_disconnect("Protocol error: X11 display already set."); + { + int proto_len, data_len; + proto = packet_get_string(&proto_len); + data = packet_get_string(&data_len); + packet_integrity_check(plen, 4+proto_len + 4+data_len + 4, type); + } + if (packet_get_protocol_flags() & SSH_PROTOFLAG_SCREEN_NUMBER) + screen = packet_get_int(); + else + screen = 0; + display = x11_create_display_inet(screen); + if (!display) + goto fail; + + /* Setup to always have a local .Xauthority. */ + xauthfile = xmalloc(MAXPATHLEN); + snprintf(xauthfile, MAXPATHLEN, "/tmp/XauthXXXXXX"); + + if ((xauthfd = mkstemp(xauthfile)) != -1) { + fchown(xauthfd, pw->pw_uid, pw->pw_gid); + close(xauthfd); + } + else { + xfree(xauthfile); + xauthfile = NULL; + } + break; +#else /* XAUTH_PATH */ + /* No xauth program; we won't accept forwarding with spoofing. */ + packet_send_debug("No xauth program; cannot forward with spoofing."); + goto fail; +#endif /* XAUTH_PATH */ + + case SSH_CMSG_AGENT_REQUEST_FORWARDING: + if (no_agent_forwarding_flag) + { + debug("Authentication agent forwarding not permitted for this authentication."); + goto fail; + } + debug("Received authentication agent forwarding request."); + auth_input_request_forwarding(pw); + break; + + case SSH_CMSG_PORT_FORWARD_REQUEST: + if (no_port_forwarding_flag) + { + debug("Port forwarding not permitted for this authentication."); + goto fail; + } + debug("Received TCP/IP port forwarding request."); + channel_input_port_forward_request(pw->pw_uid == 0); + break; + + case SSH_CMSG_EXEC_SHELL: + /* Set interactive/non-interactive mode. */ + packet_set_interactive(have_pty || display != NULL, + options.keepalives); + + if (forced_command != NULL) + goto do_forced_command; + debug("Forking shell."); + packet_integrity_check(plen, 0, type); + if (have_pty) + do_exec_pty(NULL, ptyfd, ttyfd, ttyname, pw, term, display, proto, + data); + else + do_exec_no_pty(NULL, pw, display, proto, data); + return; + + case SSH_CMSG_EXEC_CMD: + /* Set interactive/non-interactive mode. */ + packet_set_interactive(have_pty || display != NULL, + options.keepalives); + + if (forced_command != NULL) + goto do_forced_command; + /* Get command from the packet. */ + { + int dlen; + command = packet_get_string(&dlen); + debug("Executing command '%.500s'", command); + packet_integrity_check(plen, 4 + dlen, type); + } + if (have_pty) + do_exec_pty(command, ptyfd, ttyfd, ttyname, pw, term, display, + proto, data); + else + do_exec_no_pty(command, pw, display, proto, data); + xfree(command); + return; + + case SSH_CMSG_MAX_PACKET_SIZE: + debug("The server does not support limiting packet size."); + goto fail; + + default: + /* Any unknown messages in this phase are ignored, and a failure + message is returned. */ + log("Unknown packet type received after authentication: %d", type); + goto fail; + } + + /* The request was successfully processed. */ + packet_start(SSH_SMSG_SUCCESS); + packet_send(); + packet_write_wait(); + + /* Enable compression now that we have replied if appropriate. */ + if (enable_compression_after_reply) + { + enable_compression_after_reply = 0; + packet_start_compression(compression_level); + } + + continue; + + fail: + /* The request failed. */ + packet_start(SSH_SMSG_FAILURE); + packet_send(); + packet_write_wait(); + continue; + + do_forced_command: + /* There is a forced command specified for this login. Execute it. */ + debug("Executing forced command: %.900s", forced_command); + if (have_pty) + do_exec_pty(forced_command, ptyfd, ttyfd, ttyname, pw, term, display, + proto, data); + else + do_exec_no_pty(forced_command, pw, display, proto, data); + return; + } +} + +/* This is called to fork and execute a command when we have no tty. This + will call do_child from the child, and server_loop from the parent after + setting up file descriptors and such. */ + +void do_exec_no_pty(const char *command, struct passwd *pw, + const char *display, const char *auth_proto, + const char *auth_data) +{ + int pid; + +#ifdef USE_PIPES + int pin[2], pout[2], perr[2]; + /* Allocate pipes for communicating with the program. */ + if (pipe(pin) < 0 || pipe(pout) < 0 || pipe(perr) < 0) + packet_disconnect("Could not create pipes: %.100s", + strerror(errno)); +#else /* USE_PIPES */ + int inout[2], err[2]; + /* Uses socket pairs to communicate with the program. */ + if (socketpair(AF_UNIX, SOCK_STREAM, 0, inout) < 0 || + socketpair(AF_UNIX, SOCK_STREAM, 0, err) < 0) + packet_disconnect("Could not create socket pairs: %.100s", + strerror(errno)); +#endif /* USE_PIPES */ + + setproctitle("%s@notty", pw->pw_name); + + /* Fork the child. */ + if ((pid = fork()) == 0) + { + /* Child. Reinitialize the log since the pid has changed. */ + log_init(av0, debug_flag && !inetd_flag, debug_flag, + options.quiet_mode, options.log_facility); + + /* Create a new session and process group since the 4.4BSD setlogin() + affects the entire process group. */ + if (setsid() < 0) + error("setsid failed: %.100s", strerror(errno)); + +#ifdef USE_PIPES + /* Redirect stdin. We close the parent side of the socket pair, + and make the child side the standard input. */ + close(pin[1]); + if (dup2(pin[0], 0) < 0) + perror("dup2 stdin"); + close(pin[0]); + + /* Redirect stdout. */ + close(pout[0]); + if (dup2(pout[1], 1) < 0) + perror("dup2 stdout"); + close(pout[1]); + + /* Redirect stderr. */ + close(perr[0]); + if (dup2(perr[1], 2) < 0) + perror("dup2 stderr"); + close(perr[1]); +#else /* USE_PIPES */ + /* Redirect stdin, stdout, and stderr. Stdin and stdout will use the + same socket, as some programs (particularly rdist) seem to depend + on it. */ + close(inout[1]); + close(err[1]); + if (dup2(inout[0], 0) < 0) /* stdin */ + perror("dup2 stdin"); + if (dup2(inout[0], 1) < 0) /* stdout. Note: same socket as stdin. */ + perror("dup2 stdout"); + if (dup2(err[0], 2) < 0) /* stderr */ + perror("dup2 stderr"); +#endif /* USE_PIPES */ + + /* Do processing for the child (exec command etc). */ + do_child(command, pw, NULL, display, auth_proto, auth_data, NULL); + /*NOTREACHED*/ + } + if (pid < 0) + packet_disconnect("fork failed: %.100s", strerror(errno)); +#ifdef USE_PIPES + /* We are the parent. Close the child sides of the pipes. */ + close(pin[0]); + close(pout[1]); + close(perr[1]); + + /* Enter the interactive session. */ + server_loop(pid, pin[1], pout[0], perr[0]); + /* server_loop has closed pin[1], pout[1], and perr[1]. */ +#else /* USE_PIPES */ + /* We are the parent. Close the child sides of the socket pairs. */ + close(inout[0]); + close(err[0]); + + /* Enter the interactive session. Note: server_loop must be able to handle + the case that fdin and fdout are the same. */ + server_loop(pid, inout[1], inout[1], err[1]); + /* server_loop has closed inout[1] and err[1]. */ +#endif /* USE_PIPES */ +} + +struct pty_cleanup_context +{ + const char *ttyname; + int pid; +}; + +/* Function to perform cleanup if we get aborted abnormally (e.g., due to a + dropped connection). */ + +void pty_cleanup_proc(void *context) +{ + struct pty_cleanup_context *cu = context; + + debug("pty_cleanup_proc called"); + +#if defined(KRB4) + /* Destroy user's ticket cache file. */ + (void) dest_tkt(); +#endif /* KRB4 */ + + /* Record that the user has logged out. */ + record_logout(cu->pid, cu->ttyname); + + /* Release the pseudo-tty. */ + pty_release(cu->ttyname); +} + +/* This is called to fork and execute a command when we have a tty. This + will call do_child from the child, and server_loop from the parent after + setting up file descriptors, controlling tty, updating wtmp, utmp, + lastlog, and other such operations. */ + +void do_exec_pty(const char *command, int ptyfd, int ttyfd, + const char *ttyname, struct passwd *pw, const char *term, + const char *display, const char *auth_proto, + const char *auth_data) +{ + int pid, fdout; + const char *hostname; + time_t last_login_time; + char buf[100], *time_string; + FILE *f; + char line[256]; + struct stat st; + int quiet_login; + struct sockaddr_in from; + int fromlen; + struct pty_cleanup_context cleanup_context; + + /* Get remote host name. */ + hostname = get_canonical_hostname(); + + /* Get the time when the user last logged in. Buf will be set to contain + the hostname the last login was from. */ + if(!options.use_login) { + last_login_time = get_last_login_time(pw->pw_uid, pw->pw_name, + buf, sizeof(buf)); + } + + setproctitle("%s@%s", pw->pw_name, strrchr(ttyname, '/') + 1); + + /* Fork the child. */ + if ((pid = fork()) == 0) + { + pid = getpid(); + + /* Child. Reinitialize the log because the pid has changed. */ + log_init(av0, debug_flag && !inetd_flag, debug_flag, options.quiet_mode, + options.log_facility); + + /* Close the master side of the pseudo tty. */ + close(ptyfd); + + /* Make the pseudo tty our controlling tty. */ + pty_make_controlling_tty(&ttyfd, ttyname); + + /* Redirect stdin from the pseudo tty. */ + if (dup2(ttyfd, fileno(stdin)) < 0) + error("dup2 stdin failed: %.100s", strerror(errno)); + + /* Redirect stdout to the pseudo tty. */ + if (dup2(ttyfd, fileno(stdout)) < 0) + error("dup2 stdin failed: %.100s", strerror(errno)); + + /* Redirect stderr to the pseudo tty. */ + if (dup2(ttyfd, fileno(stderr)) < 0) + error("dup2 stdin failed: %.100s", strerror(errno)); + + /* Close the extra descriptor for the pseudo tty. */ + close(ttyfd); + + /* Get IP address of client. This is needed because we want to record + where the user logged in from. If the connection is not a socket, + let the ip address be 0.0.0.0. */ + memset(&from, 0, sizeof(from)); + if (packet_get_connection_in() == packet_get_connection_out()) + { + fromlen = sizeof(from); + if (getpeername(packet_get_connection_in(), + (struct sockaddr *)&from, &fromlen) < 0) + fatal("getpeername: %.100s", strerror(errno)); + } + + /* Record that there was a login on that terminal. */ + record_login(pid, ttyname, pw->pw_name, pw->pw_uid, hostname, + &from); + + /* Check if .hushlogin exists. */ + snprintf(line, sizeof line, "%.200s/.hushlogin", pw->pw_dir); + quiet_login = stat(line, &st) >= 0; + + /* If the user has logged in before, display the time of last login. + However, don't display anything extra if a command has been + specified (so that ssh can be used to execute commands on a remote + machine without users knowing they are going to another machine). + Login(1) will do this for us as well, so check if login(1) is used */ + if (command == NULL && last_login_time != 0 && !quiet_login && + !options.use_login) + { + /* Convert the date to a string. */ + time_string = ctime(&last_login_time); + /* Remove the trailing newline. */ + if (strchr(time_string, '\n')) + *strchr(time_string, '\n') = 0; + /* Display the last login time. Host if displayed if known. */ + if (strcmp(buf, "") == 0) + printf("Last login: %s\r\n", time_string); + else + printf("Last login: %s from %s\r\n", time_string, buf); + } + + /* Print /etc/motd unless a command was specified or printing it was + disabled in server options or login(1) will be used. Note that + some machines appear to print it in /etc/profile or similar. */ + if (command == NULL && options.print_motd && !quiet_login && + !options.use_login) + { + /* Print /etc/motd if it exists. */ + f = fopen("/etc/motd", "r"); + if (f) + { + while (fgets(line, sizeof(line), f)) + fputs(line, stdout); + fclose(f); + } + } + + /* Do common processing for the child, such as execing the command. */ + do_child(command, pw, term, display, auth_proto, auth_data, ttyname); + /*NOTREACHED*/ + } + if (pid < 0) + packet_disconnect("fork failed: %.100s", strerror(errno)); + /* Parent. Close the slave side of the pseudo tty. */ + close(ttyfd); + + /* Create another descriptor of the pty master side for use as the standard + input. We could use the original descriptor, but this simplifies code + in server_loop. The descriptor is bidirectional. */ + fdout = dup(ptyfd); + if (fdout < 0) + packet_disconnect("dup failed: %.100s", strerror(errno)); + + /* Add a cleanup function to clear the utmp entry and record logout time + in case we call fatal() (e.g., the connection gets closed). */ + cleanup_context.pid = pid; + cleanup_context.ttyname = ttyname; + fatal_add_cleanup(pty_cleanup_proc, (void *)&cleanup_context); + + /* Enter interactive session. */ + server_loop(pid, ptyfd, fdout, -1); + /* server_loop has not closed ptyfd and fdout. */ + + /* Cancel the cleanup function. */ + fatal_remove_cleanup(pty_cleanup_proc, (void *)&cleanup_context); + + /* Record that the user has logged out. */ + record_logout(pid, ttyname); + + /* Release the pseudo-tty. */ + pty_release(ttyname); + + /* Close the server side of the socket pairs. We must do this after the + pty cleanup, so that another process doesn't get this pty while we're + still cleaning up. */ + close(ptyfd); + close(fdout); +} + +/* Sets the value of the given variable in the environment. If the variable + already exists, its value is overriden. */ + +void child_set_env(char ***envp, unsigned int *envsizep, const char *name, + const char *value) +{ + unsigned int i, namelen; + char **env; + + /* Find the slot where the value should be stored. If the variable already + exists, we reuse the slot; otherwise we append a new slot at the end + of the array, expanding if necessary. */ + env = *envp; + namelen = strlen(name); + for (i = 0; env[i]; i++) + if (strncmp(env[i], name, namelen) == 0 && env[i][namelen] == '=') + break; + if (env[i]) + { + /* Name already exists. Reuse the slot. */ + xfree(env[i]); + } + else + { + /* New variable. Expand the array if necessary. */ + if (i >= (*envsizep) - 1) + { + (*envsizep) += 50; + env = (*envp) = xrealloc(env, (*envsizep) * sizeof(char *)); + } + + /* Need to set the NULL pointer at end of array beyond the new + slot. */ + env[i + 1] = NULL; + } + + /* Allocate space and format the variable in the appropriate slot. */ + env[i] = xmalloc(strlen(name) + 1 + strlen(value) + 1); + snprintf(env[i], strlen(name) + 1 + strlen(value) + 1, "%s=%s", name, value); +} + +/* Reads environment variables from the given file and adds/overrides them + into the environment. If the file does not exist, this does nothing. + Otherwise, it must consist of empty lines, comments (line starts with '#') + and assignments of the form name=value. No other forms are allowed. */ + +void read_environment_file(char ***env, unsigned int *envsize, + const char *filename) +{ + FILE *f; + char buf[4096]; + char *cp, *value; + + /* Open the environment file. */ + f = fopen(filename, "r"); + if (!f) + return; /* Not found. */ + + /* Process each line. */ + while (fgets(buf, sizeof(buf), f)) + { + /* Skip leading whitespace. */ + for (cp = buf; *cp == ' ' || *cp == '\t'; cp++) + ; + + /* Ignore empty and comment lines. */ + if (!*cp || *cp == '#' || *cp == '\n') + continue; + + /* Remove newline. */ + if (strchr(cp, '\n')) + *strchr(cp, '\n') = '\0'; + + /* Find the equals sign. Its lack indicates badly formatted line. */ + value = strchr(cp, '='); + if (value == NULL) + { + fprintf(stderr, "Bad line in %.100s: %.200s\n", filename, buf); + continue; + } + + /* Replace the equals sign by nul, and advance value to the value + string. */ + *value = '\0'; + value++; + + /* Set the value in environment. */ + child_set_env(env, envsize, cp, value); + } + + fclose(f); +} + +/* Performs common processing for the child, such as setting up the + environment, closing extra file descriptors, setting the user and group + ids, and executing the command or shell. */ + +void do_child(const char *command, struct passwd *pw, const char *term, + const char *display, const char *auth_proto, + const char *auth_data, const char *ttyname) +{ + const char *shell, *cp = NULL; + char buf[256]; + FILE *f; + unsigned int envsize, i; + char **env; + extern char **environ; + struct stat st; + char *argv[10]; + + /* Check /etc/nologin. */ + f = fopen("/etc/nologin", "r"); + if (f) + { /* /etc/nologin exists. Print its contents and exit. */ + while (fgets(buf, sizeof(buf), f)) + fputs(buf, stderr); + fclose(f); + if (pw->pw_uid != 0) + exit(254); + } + + /* Set login name in the kernel. */ + if (setlogin(pw->pw_name) < 0) + error("setlogin failed: %s", strerror(errno)); + + /* Set uid, gid, and groups. */ + /* Login(1) does this as well, and it needs uid 0 for the "-h" switch, + so we let login(1) to this for us. */ + if(!options.use_login) { + if (getuid() == 0 || geteuid() == 0) + { + if (setgid(pw->pw_gid) < 0) + { + perror("setgid"); + exit(1); + } + /* Initialize the group list. */ + if (initgroups(pw->pw_name, pw->pw_gid) < 0) + { + perror("initgroups"); + exit(1); + } + endgrent(); + + /* Permanently switch to the desired uid. */ + permanently_set_uid(pw->pw_uid); + } + + if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) + fatal("Failed to set uids to %d.", (int)pw->pw_uid); + } + + /* Get the shell from the password data. An empty shell field is legal, + and means /bin/sh. */ + shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; + +#ifdef AFS + /* Try to get AFS tokens for the local cell. */ + if (k_hasafs()) { + char cell[64]; + + if (k_afs_cell_of_file(pw->pw_dir, cell, sizeof(cell)) == 0) + krb_afslog(cell, 0); + + krb_afslog(0, 0); + } +#endif /* AFS */ + + /* Initialize the environment. In the first part we allocate space for + all environment variables. */ + envsize = 100; + env = xmalloc(envsize * sizeof(char *)); + env[0] = NULL; + + if(!options.use_login) { + /* Set basic environment. */ + child_set_env(&env, &envsize, "USER", pw->pw_name); + child_set_env(&env, &envsize, "LOGNAME", pw->pw_name); + child_set_env(&env, &envsize, "HOME", pw->pw_dir); + child_set_env(&env, &envsize, "PATH", _PATH_STDPATH); + + snprintf(buf, sizeof buf, "%.200s/%.50s", + _PATH_MAILDIR, pw->pw_name); + child_set_env(&env, &envsize, "MAIL", buf); + + /* Normal systems set SHELL by default. */ + child_set_env(&env, &envsize, "SHELL", shell); + } + + /* Let it inherit timezone if we have one. */ + if (getenv("TZ")) + child_set_env(&env, &envsize, "TZ", getenv("TZ")); + + /* Set custom environment options from RSA authentication. */ + while (custom_environment) + { + struct envstring *ce = custom_environment; + char *s = ce->s; + int i; + for (i = 0; s[i] != '=' && s[i]; i++) + ; + if (s[i] == '=') + { + s[i] = 0; + child_set_env(&env, &envsize, s, s + i + 1); + } + custom_environment = ce->next; + xfree(ce->s); + xfree(ce); + } + + /* Set SSH_CLIENT. */ + snprintf(buf, sizeof buf, "%.50s %d %d", + get_remote_ipaddr(), get_remote_port(), options.port); + child_set_env(&env, &envsize, "SSH_CLIENT", buf); + + /* Set SSH_TTY if we have a pty. */ + if (ttyname) + child_set_env(&env, &envsize, "SSH_TTY", ttyname); + + /* Set TERM if we have a pty. */ + if (term) + child_set_env(&env, &envsize, "TERM", term); + + /* Set DISPLAY if we have one. */ + if (display) + child_set_env(&env, &envsize, "DISPLAY", display); + +#ifdef KRB4 + if (ticket) + child_set_env(&env, &envsize, "KRBTKFILE", ticket); +#endif /* KRB4 */ + + /* Set XAUTHORITY to always be a local file. */ + if (xauthfile) + child_set_env(&env, &envsize, "XAUTHORITY", xauthfile); + + /* Set variable for forwarded authentication connection, if we have one. */ + if (auth_get_socket_name() != NULL) + child_set_env(&env, &envsize, SSH_AUTHSOCKET_ENV_NAME, + auth_get_socket_name()); + + /* Read $HOME/.ssh/environment. */ + if(!options.use_login) { + snprintf(buf, sizeof buf, "%.200s/.ssh/environment", pw->pw_dir); + read_environment_file(&env, &envsize, buf); + } + + /* If debugging, dump the environment to stderr. */ + if (debug_flag) + { + fprintf(stderr, "Environment:\n"); + for (i = 0; env[i]; i++) + fprintf(stderr, " %.200s\n", env[i]); + } + + /* Close the connection descriptors; note that this is the child, and the + server will still have the socket open, and it is important that we + do not shutdown it. Note that the descriptors cannot be closed before + building the environment, as we call get_remote_ipaddr there. */ + if (packet_get_connection_in() == packet_get_connection_out()) + close(packet_get_connection_in()); + else + { + close(packet_get_connection_in()); + close(packet_get_connection_out()); + } + /* Close all descriptors related to channels. They will still remain + open in the parent. */ + channel_close_all(); + + /* Close any extra file descriptors. Note that there may still be + descriptors left by system functions. They will be closed later. */ + endpwent(); + endhostent(); + + /* Close any extra open file descriptors so that we don\'t have them + hanging around in clients. Note that we want to do this after + initgroups, because at least on Solaris 2.3 it leaves file descriptors + open. */ + for (i = 3; i < 64; i++) + close(i); + + /* Change current directory to the user\'s home directory. */ + if (chdir(pw->pw_dir) < 0) + fprintf(stderr, "Could not chdir to home directory %s: %s\n", + pw->pw_dir, strerror(errno)); + + /* Must take new environment into use so that .ssh/rc, /etc/sshrc and + xauth are run in the proper environment. */ + environ = env; + + /* Run $HOME/.ssh/rc, /etc/sshrc, or xauth (whichever is found first + in this order). */ + if(!options.use_login) { + if (stat(SSH_USER_RC, &st) >= 0) + { + if (debug_flag) + fprintf(stderr, "Running /bin/sh %s\n", SSH_USER_RC); + + f = popen("/bin/sh " SSH_USER_RC, "w"); + if (f) + { + if (auth_proto != NULL && auth_data != NULL) + fprintf(f, "%s %s\n", auth_proto, auth_data); + pclose(f); + } + else + fprintf(stderr, "Could not run %s\n", SSH_USER_RC); + } + else + if (stat(SSH_SYSTEM_RC, &st) >= 0) + { + if (debug_flag) + fprintf(stderr, "Running /bin/sh %s\n", SSH_SYSTEM_RC); + + f = popen("/bin/sh " SSH_SYSTEM_RC, "w"); + if (f) + { + if (auth_proto != NULL && auth_data != NULL) + fprintf(f, "%s %s\n", auth_proto, auth_data); + pclose(f); + } + else + fprintf(stderr, "Could not run %s\n", SSH_SYSTEM_RC); + } +#ifdef XAUTH_PATH + else + { + /* Add authority data to .Xauthority if appropriate. */ + if (auth_proto != NULL && auth_data != NULL) + { + if (debug_flag) + fprintf(stderr, "Running %.100s add %.100s %.100s %.100s\n", + XAUTH_PATH, display, auth_proto, auth_data); + + f = popen(XAUTH_PATH " -q -", "w"); + if (f) + { + fprintf(f, "add %s %s %s\n", display, auth_proto, auth_data); + fclose(f); + } + else + fprintf(stderr, "Could not run %s -q -\n", XAUTH_PATH); + } + } +#endif /* XAUTH_PATH */ + + /* Get the last component of the shell name. */ + cp = strrchr(shell, '/'); + if (cp) + cp++; + else + cp = shell; + } + + /* If we have no command, execute the shell. In this case, the shell name + to be passed in argv[0] is preceded by '-' to indicate that this is + a login shell. */ + if (!command) + { + if(!options.use_login) { + char buf[256]; + + /* Check for mail if we have a tty and it was enabled in server options. */ + if (ttyname && options.check_mail) { + char *mailbox; + struct stat mailstat; + mailbox = getenv("MAIL"); + if(mailbox != NULL) { + if(stat(mailbox, &mailstat) != 0 || mailstat.st_size == 0) { + printf("No mail.\n"); + } else if(mailstat.st_mtime < mailstat.st_atime) { + printf("You have mail.\n"); + } else { + printf("You have new mail.\n"); + } + } + } + /* Start the shell. Set initial character to '-'. */ + buf[0] = '-'; + strncpy(buf + 1, cp, sizeof(buf) - 1); + buf[sizeof(buf) - 1] = 0; + /* Execute the shell. */ + argv[0] = buf; + argv[1] = NULL; + execve(shell, argv, env); + /* Executing the shell failed. */ + perror(shell); + exit(1); + + } else { + /* Launch login(1). */ + + execl("/usr/bin/login", "login", "-h", get_remote_ipaddr(), "-p", "-f", "--", pw->pw_name, NULL); + + /* Login couldn't be executed, die. */ + + perror("login"); + exit(1); + } + } + + /* Execute the command using the user's shell. This uses the -c option + to execute the command. */ + argv[0] = (char *)cp; + argv[1] = "-c"; + argv[2] = (char *)command; + argv[3] = NULL; + execve(shell, argv, env); + perror(shell); + exit(1); +} |