Edit
IABSD.fr/src/usr.bin/ssh/session.c
djm
- usr.bin/ssh/session.c
-
/* $OpenBSD: session.c,v 1.329 2021/08/11 05:20:17 djm Exp $ */ /* * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland * All rights reserved * * As far as I am concerned, the code I have written for this software * can be used freely for any purpose. Any derived versions of this * software must be clearly marked as such, and if the derived work is * incompatible with the protocol description in the RFC file, it must be * called by a name other than "ssh" or "Secure Shell". * * SSH2 support by Markus Friedl. * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include <sys/types.h> #include <sys/wait.h> #include <sys/un.h> #include <sys/stat.h> #include <sys/socket.h> #include <sys/queue.h> #include <ctype.h> #include <errno.h> #include <fcntl.h> #include <grp.h> #include <login_cap.h> #include <netdb.h> #include <paths.h> #include <pwd.h> #include <signal.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <stdarg.h> #include <unistd.h> #include <limits.h> #include "xmalloc.h" #include "ssh.h" #include "ssh2.h" #include "sshpty.h" #include "packet.h" #include "sshbuf.h" #include "ssherr.h" #include "match.h" #include "uidswap.h" #include "compat.h" #include "channels.h" #include "sshkey.h" #include "cipher.h" #include "kex.h" #include "hostfile.h" #include "auth.h" #include "auth-options.h" #include "authfd.h" #include "pathnames.h" #include "log.h" #include "misc.h" #include "servconf.h" #include "sshlogin.h" #include "serverloop.h" #include "canohost.h" #include "session.h" #ifdef GSSAPI #include "ssh-gss.h" #endif #include "monitor_wrap.h" #include "sftp.h" #include "atomicio.h" #ifdef KRB5 #include <kafs.h> #endif #define IS_INTERNAL_SFTP(c) \ (!strncmp(c, INTERNAL_SFTP_NAME, sizeof(INTERNAL_SFTP_NAME) - 1) && \ (c[sizeof(INTERNAL_SFTP_NAME) - 1] == '\0' || \ c[sizeof(INTERNAL_SFTP_NAME) - 1] == ' ' || \ c[sizeof(INTERNAL_SFTP_NAME) - 1] == '\t')) /* func */ Session *session_new(void); void session_set_fds(struct ssh *, Session *, int, int, int, int, int); void session_pty_cleanup(Session *); void session_proctitle(Session *); int session_setup_x11fwd(struct ssh *, Session *); int do_exec_pty(struct ssh *, Session *, const char *); int do_exec_no_pty(struct ssh *, Session *, const char *); int do_exec(struct ssh *, Session *, const char *); void do_login(struct ssh *, Session *, const char *); void do_child(struct ssh *, Session *, const char *); void do_motd(void); int check_quietlogin(Session *, const char *); static void do_authenticated2(struct ssh *, Authctxt *); static int session_pty_req(struct ssh *, Session *); /* import */ extern ServerOptions options; extern char *__progname; extern int debug_flag; extern u_int utmp_len; extern int startup_pipe; extern void destroy_sensitive_data(void); extern struct sshbuf *loginmsg; extern struct sshauthopt *auth_opts; extern char *tun_fwd_ifnames; /* serverloop.c */ /* original command from peer. */ const char *original_command = NULL; /* data */ static int sessions_first_unused = -1; static int sessions_nalloc = 0; static Session *sessions = NULL; #define SUBSYSTEM_NONE 0 #define SUBSYSTEM_EXT 1 #define SUBSYSTEM_INT_SFTP 2 #define SUBSYSTEM_INT_SFTP_ERROR 3 login_cap_t *lc; static int is_child = 0; static int in_chroot = 0; /* File containing userauth info, if ExposeAuthInfo set */ static char *auth_info_file = NULL; /* Name and directory of socket for authentication agent forwarding. */ static char *auth_sock_name = NULL; static char *auth_sock_dir = NULL; /* removes the agent forwarding socket */ static void auth_sock_cleanup_proc(struct passwd *pw) { if (auth_sock_name != NULL) { temporarily_use_uid(pw); unlink(auth_sock_name); rmdir(auth_sock_dir); auth_sock_name = NULL; restore_uid(); } } static int auth_input_request_forwarding(struct ssh *ssh, struct passwd * pw) { Channel *nc; int sock = -1; if (auth_sock_name != NULL) { error("authentication forwarding requested twice."); return 0; } /* Temporarily drop privileged uid for mkdir/bind. */ temporarily_use_uid(pw); /* Allocate a buffer for the socket name, and format the name. */ auth_sock_dir = xstrdup("/tmp/ssh-XXXXXXXXXX"); /* Create private directory for socket */ if (mkdtemp(auth_sock_dir) == NULL) { ssh_packet_send_debug(ssh, "Agent forwarding disabled: " "mkdtemp() failed: %.100s", strerror(errno)); restore_uid(); free(auth_sock_dir); auth_sock_dir = NULL; goto authsock_err; } xasprintf(&auth_sock_name, "%s/agent.%ld", auth_sock_dir, (long) getpid()); /* Start a Unix listener on auth_sock_name. */ sock = unix_listener(auth_sock_name, SSH_LISTEN_BACKLOG, 0); /* Restore the privileged uid. */ restore_uid(); /* Check for socket/bind/listen failure. */ if (sock < 0) goto authsock_err; /* Allocate a channel for the authentication agent socket. */ nc = channel_new(ssh, "auth socket", SSH_CHANNEL_AUTH_SOCKET, sock, sock, -1, CHAN_X11_WINDOW_DEFAULT, CHAN_X11_PACKET_DEFAULT, 0, "auth socket", 1); nc->path = xstrdup(auth_sock_name); return 1; authsock_err: free(auth_sock_name); if (auth_sock_dir != NULL) { temporarily_use_uid(pw); rmdir(auth_sock_dir); restore_uid(); free(auth_sock_dir); } if (sock != -1) close(sock); auth_sock_name = NULL; auth_sock_dir = NULL; return 0; } static void display_loginmsg(void) { int r; if (sshbuf_len(loginmsg) == 0) return; if ((r = sshbuf_put_u8(loginmsg, 0)) != 0) fatal_fr(r, "sshbuf_put_u8"); printf("%s", (char *)sshbuf_ptr(loginmsg)); sshbuf_reset(loginmsg); } static void prepare_auth_info_file(struct passwd *pw, struct sshbuf *info) { int fd = -1, success = 0; if (!options.expose_userauth_info || info == NULL) return; temporarily_use_uid(pw); auth_info_file = xstrdup("/tmp/sshauth.XXXXXXXXXXXXXXX"); if ((fd = mkstemp(auth_info_file)) == -1) { error_f("mkstemp: %s", strerror(errno)); goto out; } if (atomicio(vwrite, fd, sshbuf_mutable_ptr(info), sshbuf_len(info)) != sshbuf_len(info)) { error_f("write: %s", strerror(errno)); goto out; } if (close(fd) != 0) { error_f("close: %s", strerror(errno)); goto out; } success = 1; out: if (!success) { if (fd != -1) close(fd); free(auth_info_file); auth_info_file = NULL; } restore_uid(); } static void set_fwdpermit_from_authopts(struct ssh *ssh, const struct sshauthopt *opts) { char *tmp, *cp, *host; int port; size_t i; if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0) { channel_clear_permission(ssh, FORWARD_USER, FORWARD_LOCAL); for (i = 0; i < auth_opts->npermitopen; i++) { tmp = cp = xstrdup(auth_opts->permitopen[i]); /* This shouldn't fail as it has already been checked */ if ((host = hpdelim(&cp)) == NULL) fatal_f("internal error: hpdelim"); host = cleanhostname(host); if (cp == NULL || (port = permitopen_port(cp)) < 0) fatal_f("internal error: permitopen port"); channel_add_permission(ssh, FORWARD_USER, FORWARD_LOCAL, host, port); free(tmp); } } if ((options.allow_tcp_forwarding & FORWARD_REMOTE) != 0) { channel_clear_permission(ssh, FORWARD_USER, FORWARD_REMOTE); for (i = 0; i < auth_opts->npermitlisten; i++) { tmp = cp = xstrdup(auth_opts->permitlisten[i]); /* This shouldn't fail as it has already been checked */ if ((host = hpdelim(&cp)) == NULL) fatal_f("internal error: hpdelim"); host = cleanhostname(host); if (cp == NULL || (port = permitopen_port(cp)) < 0) fatal_f("internal error: permitlisten port"); channel_add_permission(ssh, FORWARD_USER, FORWARD_REMOTE, host, port); free(tmp); } } } void do_authenticated(struct ssh *ssh, Authctxt *authctxt) { setproctitle("%s", authctxt->pw->pw_name); auth_log_authopts("active", auth_opts, 0); /* setup the channel layer */ /* XXX - streamlocal? */ set_fwdpermit_from_authopts(ssh, auth_opts); if (!auth_opts->permit_port_forwarding_flag || options.disable_forwarding) { channel_disable_admin(ssh, FORWARD_LOCAL); channel_disable_admin(ssh, FORWARD_REMOTE); } else { if ((options.allow_tcp_forwarding & FORWARD_LOCAL) == 0) channel_disable_admin(ssh, FORWARD_LOCAL); else channel_permit_all(ssh, FORWARD_LOCAL); if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0) channel_disable_admin(ssh, FORWARD_REMOTE); else channel_permit_all(ssh, FORWARD_REMOTE); } auth_debug_send(ssh); prepare_auth_info_file(authctxt->pw, authctxt->session_info); do_authenticated2(ssh, authctxt); do_cleanup(ssh, authctxt); } /* Check untrusted xauth strings for metacharacters */ static int xauth_valid_string(const char *s) { size_t i; for (i = 0; s[i] != '\0'; i++) { if (!isalnum((u_char)s[i]) && s[i] != '.' && s[i] != ':' && s[i] != '/' && s[i] != '-' && s[i] != '_') return 0; } return 1; } #define USE_PIPES 1 /* * 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. */ int do_exec_no_pty(struct ssh *ssh, Session *s, const char *command) { pid_t pid; #ifdef USE_PIPES int pin[2], pout[2], perr[2]; if (s == NULL) fatal("do_exec_no_pty: no session"); /* Allocate pipes for communicating with the program. */ if (pipe(pin) == -1) { error_f("pipe in: %.100s", strerror(errno)); return -1; } if (pipe(pout) == -1) { error_f("pipe out: %.100s", strerror(errno)); close(pin[0]); close(pin[1]); return -1; } if (pipe(perr) == -1) { error_f("pipe err: %.100s", strerror(errno)); close(pin[0]); close(pin[1]); close(pout[0]); close(pout[1]); return -1; } #else int inout[2], err[2]; if (s == NULL) fatal("do_exec_no_pty: no session"); /* Uses socket pairs to communicate with the program. */ if (socketpair(AF_UNIX, SOCK_STREAM, 0, inout) == -1) { error_f("socketpair #1: %.100s", strerror(errno)); return -1; } if (socketpair(AF_UNIX, SOCK_STREAM, 0, err) == -1) { error_f("socketpair #2: %.100s", strerror(errno)); close(inout[0]); close(inout[1]); return -1; } #endif session_proctitle(s); /* Fork the child. */ switch ((pid = fork())) { case -1: error_f("fork: %.100s", strerror(errno)); #ifdef USE_PIPES close(pin[0]); close(pin[1]); close(pout[0]); close(pout[1]); close(perr[0]); close(perr[1]); #else close(inout[0]); close(inout[1]); close(err[0]); close(err[1]); #endif return -1; case 0: is_child = 1; /* * Create a new session and process group since the 4.4BSD * setlogin() affects the entire process group. */ if (setsid() == -1) 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) == -1) perror("dup2 stdin"); close(pin[0]); /* Redirect stdout. */ close(pout[0]); if (dup2(pout[1], 1) == -1) perror("dup2 stdout"); close(pout[1]); /* Redirect stderr. */ close(perr[0]); if (dup2(perr[1], 2) == -1) perror("dup2 stderr"); close(perr[1]); #else /* * 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) == -1) /* stdin */ perror("dup2 stdin"); if (dup2(inout[0], 1) == -1) /* stdout (same as stdin) */ perror("dup2 stdout"); close(inout[0]); if (dup2(err[0], 2) == -1) /* stderr */ perror("dup2 stderr"); close(err[0]); #endif /* Do processing for the child (exec command etc). */ do_child(ssh, s, command); /* NOTREACHED */ default: break; } s->pid = pid; /* Set interactive/non-interactive mode. */ ssh_packet_set_interactive(ssh, s->display != NULL, options.ip_qos_interactive, options.ip_qos_bulk); #ifdef USE_PIPES /* We are the parent. Close the child sides of the pipes. */ close(pin[0]); close(pout[1]); close(perr[1]); session_set_fds(ssh, s, pin[1], pout[0], perr[0], s->is_subsystem, 0); #else /* 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. */ session_set_fds(ssh, s, inout[1], inout[1], err[1], s->is_subsystem, 0); #endif return 0; } /* * 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. */ int do_exec_pty(struct ssh *ssh, Session *s, const char *command) { int fdout, ptyfd, ttyfd, ptymaster; pid_t pid; if (s == NULL) fatal("do_exec_pty: no session"); ptyfd = s->ptyfd; ttyfd = s->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. * Do this before forking (and cleanup in the child) so as to * detect and gracefully fail out-of-fd conditions. */ if ((fdout = dup(ptyfd)) == -1) { error_f("dup #1: %s", strerror(errno)); close(ttyfd); close(ptyfd); return -1; } /* we keep a reference to the pty master */ if ((ptymaster = dup(ptyfd)) == -1) { error_f("dup #2: %s", strerror(errno)); close(ttyfd); close(ptyfd); close(fdout); return -1; } /* Fork the child. */ switch ((pid = fork())) { case -1: error_f("fork: %.100s", strerror(errno)); close(fdout); close(ptymaster); close(ttyfd); close(ptyfd); return -1; case 0: is_child = 1; close(fdout); close(ptymaster); /* Close the master side of the pseudo tty. */ close(ptyfd); /* Make the pseudo tty our controlling tty. */ pty_make_controlling_tty(&ttyfd, s->tty); /* Redirect stdin/stdout/stderr from the pseudo tty. */ if (dup2(ttyfd, 0) == -1) error("dup2 stdin: %s", strerror(errno)); if (dup2(ttyfd, 1) == -1) error("dup2 stdout: %s", strerror(errno)); if (dup2(ttyfd, 2) == -1) error("dup2 stderr: %s", strerror(errno)); /* Close the extra descriptor for the pseudo tty. */ close(ttyfd); /* record login, etc. similar to login(1) */ do_login(ssh, s, command); /* * Do common processing for the child, such as execing * the command. */ do_child(ssh, s, command); /* NOTREACHED */ default: break; } s->pid = pid; /* Parent. Close the slave side of the pseudo tty. */ close(ttyfd); /* Enter interactive session. */ s->ptymaster = ptymaster; ssh_packet_set_interactive(ssh, 1, options.ip_qos_interactive, options.ip_qos_bulk); session_set_fds(ssh, s, ptyfd, fdout, -1, 1, 1); return 0; } /* * This is called to fork and execute a command. If another command is * to be forced, execute that instead. */ int do_exec(struct ssh *ssh, Session *s, const char *command) { int ret; const char *forced = NULL, *tty = NULL; char session_type[1024]; if (options.adm_forced_command) { original_command = command; command = options.adm_forced_command; forced = "(config)"; } else if (auth_opts->force_command != NULL) { original_command = command; command = auth_opts->force_command; forced = "(key-option)"; } s->forced = 0; if (forced != NULL) { s->forced = 1; if (IS_INTERNAL_SFTP(command)) { s->is_subsystem = s->is_subsystem ? SUBSYSTEM_INT_SFTP : SUBSYSTEM_INT_SFTP_ERROR; } else if (s->is_subsystem) s->is_subsystem = SUBSYSTEM_EXT; snprintf(session_type, sizeof(session_type), "forced-command %s '%.900s'", forced, command); } else if (s->is_subsystem) { snprintf(session_type, sizeof(session_type), "subsystem '%.900s'", s->subsys); } else if (command == NULL) { snprintf(session_type, sizeof(session_type), "shell"); } else { /* NB. we don't log unforced commands to preserve privacy */ snprintf(session_type, sizeof(session_type), "command"); } if (s->ttyfd != -1) { tty = s->tty; if (strncmp(tty, "/dev/", 5) == 0) tty += 5; } verbose("Starting session: %s%s%s for %s from %.200s port %d id %d", session_type, tty == NULL ? "" : " on ", tty == NULL ? "" : tty, s->pw->pw_name, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), s->self); #ifdef GSSAPI if (options.gss_authentication) { temporarily_use_uid(s->pw); ssh_gssapi_storecreds(); restore_uid(); } #endif if (s->ttyfd != -1) ret = do_exec_pty(ssh, s, command); else ret = do_exec_no_pty(ssh, s, command); original_command = NULL; /* * Clear loginmsg: it's the child's responsibility to display * it to the user, otherwise multiple sessions may accumulate * multiple copies of the login messages. */ sshbuf_reset(loginmsg); return ret; } /* administrative, login(1)-like work */ void do_login(struct ssh *ssh, Session *s, const char *command) { socklen_t fromlen; struct sockaddr_storage from; struct passwd * pw = s->pw; pid_t pid = getpid(); /* * Get IP address of client. If the connection is not a socket, let * the address be 0.0.0.0. */ memset(&from, 0, sizeof(from)); fromlen = sizeof(from); if (ssh_packet_connection_is_on_socket(ssh)) { if (getpeername(ssh_packet_get_connection_in(ssh), (struct sockaddr *)&from, &fromlen) == -1) { debug("getpeername: %.100s", strerror(errno)); cleanup_exit(255); } } /* Record that there was a login on that tty from the remote host. */ if (!use_privsep) record_login(pid, s->tty, pw->pw_name, pw->pw_uid, session_get_remote_name_or_ip(ssh, utmp_len, options.use_dns), (struct sockaddr *)&from, fromlen); if (check_quietlogin(s, command)) return; display_loginmsg(); do_motd(); } /* * Display the message of the day. */ void do_motd(void) { FILE *f; char buf[256]; if (options.print_motd) { f = fopen(login_getcapstr(lc, "welcome", "/etc/motd", "/etc/motd"), "r"); if (f) { while (fgets(buf, sizeof(buf), f)) fputs(buf, stdout); fclose(f); } } } /* * Check for quiet login, either .hushlogin or command given. */ int check_quietlogin(Session *s, const char *command) { char buf[256]; struct passwd *pw = s->pw; struct stat st; /* Return 1 if .hushlogin exists or a command given. */ if (command != NULL) return 1; snprintf(buf, sizeof(buf), "%.200s/.hushlogin", pw->pw_dir); if (login_getcapbool(lc, "hushlogin", 0) || stat(buf, &st) >= 0) return 1; return 0; } /* * 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. * If allowlist is not NULL, then it is interpreted as a pattern list and * only variable names that match it will be accepted. */ static void read_environment_file(char ***env, u_int *envsize, const char *filename, const char *allowlist) { FILE *f; char *line = NULL, *cp, *value; size_t linesize = 0; u_int lineno = 0; f = fopen(filename, "r"); if (!f) return; while (getline(&line, &linesize, f) != -1) { if (++lineno > 1000) fatal("Too many lines in environment file %s", filename); for (cp = line; *cp == ' ' || *cp == '\t'; cp++) ; if (!*cp || *cp == '#' || *cp == '\n') continue; cp[strcspn(cp, "\n")] = '\0'; value = strchr(cp, '='); if (value == NULL) { fprintf(stderr, "Bad line %u in %.100s\n", lineno, filename); continue; } /* * Replace the equals sign by nul, and advance value to * the value string. */ *value = '\0'; value++; if (allowlist != NULL && match_pattern_list(cp, allowlist, 0) != 1) continue; child_set_env(env, envsize, cp, value); } free(line); fclose(f); } static char ** do_setup_env(struct ssh *ssh, Session *s, const char *shell) { char buf[256]; size_t n; u_int i, envsize; char *ocp, *cp, *value, **env, *laddr; struct passwd *pw = s->pw; /* Initialize the environment. */ envsize = 100; env = xcalloc(envsize, sizeof(char *)); env[0] = NULL; #ifdef GSSAPI /* Allow any GSSAPI methods that we've used to alter * the child's environment as they see fit */ ssh_gssapi_do_child(&env, &envsize); #endif /* Set basic environment. */ for (i = 0; i < s->num_env; i++) child_set_env(&env, &envsize, s->env[i].name, s->env[i].val); 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); if (setusercontext(lc, pw, pw->pw_uid, LOGIN_SETPATH) < 0) child_set_env(&env, &envsize, "PATH", _PATH_STDPATH); else child_set_env(&env, &envsize, "PATH", getenv("PATH")); 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); if (getenv("TZ")) child_set_env(&env, &envsize, "TZ", getenv("TZ")); if (s->term) child_set_env(&env, &envsize, "TERM", s->term); if (s->display) child_set_env(&env, &envsize, "DISPLAY", s->display); #ifdef KRB5 if (s->authctxt->krb5_ticket_file) child_set_env(&env, &envsize, "KRB5CCNAME", s->authctxt->krb5_ticket_file); #endif if (auth_sock_name != NULL) child_set_env(&env, &envsize, SSH_AUTHSOCKET_ENV_NAME, auth_sock_name); /* Set custom environment options from pubkey authentication. */ if (options.permit_user_env) { for (n = 0 ; n < auth_opts->nenv; n++) { ocp = xstrdup(auth_opts->env[n]); cp = strchr(ocp, '='); if (cp != NULL) { *cp = '\0'; /* Apply PermitUserEnvironment allowlist */ if (options.permit_user_env_allowlist == NULL || match_pattern_list(ocp, options.permit_user_env_allowlist, 0) == 1) child_set_env(&env, &envsize, ocp, cp + 1); } free(ocp); } } /* read $HOME/.ssh/environment. */ if (options.permit_user_env) { snprintf(buf, sizeof buf, "%.200s/%s/environment", pw->pw_dir, _PATH_SSH_USER_DIR); read_environment_file(&env, &envsize, buf, options.permit_user_env_allowlist); } /* Environment specified by admin */ for (i = 0; i < options.num_setenv; i++) { cp = xstrdup(options.setenv[i]); if ((value = strchr(cp, '=')) == NULL) { /* shouldn't happen; vars are checked in servconf.c */ fatal("Invalid config SetEnv: %s", options.setenv[i]); } *value++ = '\0'; child_set_env(&env, &envsize, cp, value); } /* SSH_CLIENT deprecated */ snprintf(buf, sizeof buf, "%.50s %d %d", ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), ssh_local_port(ssh)); child_set_env(&env, &envsize, "SSH_CLIENT", buf); laddr = get_local_ipaddr(ssh_packet_get_connection_in(ssh)); snprintf(buf, sizeof buf, "%.50s %d %.50s %d", ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), laddr, ssh_local_port(ssh)); free(laddr); child_set_env(&env, &envsize, "SSH_CONNECTION", buf); if (tun_fwd_ifnames != NULL) child_set_env(&env, &envsize, "SSH_TUNNEL", tun_fwd_ifnames); if (auth_info_file != NULL) child_set_env(&env, &envsize, "SSH_USER_AUTH", auth_info_file); if (s->ttyfd != -1) child_set_env(&env, &envsize, "SSH_TTY", s->tty); if (original_command) child_set_env(&env, &envsize, "SSH_ORIGINAL_COMMAND", original_command); if (debug_flag) { /* dump the environment */ fprintf(stderr, "Environment:\n"); for (i = 0; env[i]; i++) fprintf(stderr, " %.200s\n", env[i]); } return env; } /* * Run $HOME/.ssh/rc, /etc/ssh/sshrc, or xauth (whichever is found * first in this order). */ static void do_rc_files(struct ssh *ssh, Session *s, const char *shell) { FILE *f = NULL; char *cmd = NULL, *user_rc = NULL; int do_xauth; struct stat st; do_xauth = s->display != NULL && s->auth_proto != NULL && s->auth_data != NULL; xasprintf(&user_rc, "%s/%s", s->pw->pw_dir, _PATH_SSH_USER_RC); /* ignore _PATH_SSH_USER_RC for subsystems and admin forced commands */ if (!s->is_subsystem && options.adm_forced_command == NULL && auth_opts->permit_user_rc && options.permit_user_rc && stat(user_rc, &st) >= 0) { if (xasprintf(&cmd, "%s -c '%s %s'", shell, _PATH_BSHELL, user_rc) == -1) fatal_f("xasprintf: %s", strerror(errno)); if (debug_flag) fprintf(stderr, "Running %s\n", cmd); f = popen(cmd, "w"); if (f) { if (do_xauth) fprintf(f, "%s %s\n", s->auth_proto, s->auth_data); pclose(f); } else fprintf(stderr, "Could not run %s\n", user_rc); } else if (stat(_PATH_SSH_SYSTEM_RC, &st) >= 0) { if (debug_flag) fprintf(stderr, "Running %s %s\n", _PATH_BSHELL, _PATH_SSH_SYSTEM_RC); f = popen(_PATH_BSHELL " " _PATH_SSH_SYSTEM_RC, "w"); if (f) { if (do_xauth) fprintf(f, "%s %s\n", s->auth_proto, s->auth_data); pclose(f); } else fprintf(stderr, "Could not run %s\n", _PATH_SSH_SYSTEM_RC); } else if (do_xauth && options.xauth_location != NULL) { /* Add authority data to .Xauthority if appropriate. */ if (debug_flag) { fprintf(stderr, "Running %.500s remove %.100s\n", options.xauth_location, s->auth_display); fprintf(stderr, "%.500s add %.100s %.100s %.100s\n", options.xauth_location, s->auth_display, s->auth_proto, s->auth_data); } if (xasprintf(&cmd, "%s -q -", options.xauth_location) == -1) fatal_f("xasprintf: %s", strerror(errno)); f = popen(cmd, "w"); if (f) { fprintf(f, "remove %s\n", s->auth_display); fprintf(f, "add %s %s %s\n", s->auth_display, s->auth_proto, s->auth_data); pclose(f); } else { fprintf(stderr, "Could not run %s\n", cmd); } } free(cmd); free(user_rc); } static void do_nologin(struct passwd *pw) { FILE *f = NULL; char buf[1024], *nl, *def_nl = _PATH_NOLOGIN; struct stat sb; if (login_getcapbool(lc, "ignorenologin", 0) || pw->pw_uid == 0) return; nl = login_getcapstr(lc, "nologin", def_nl, def_nl); if (stat(nl, &sb) == -1) { if (nl != def_nl) free(nl); return; } /* /etc/nologin exists. Print its contents if we can and exit. */ logit("User %.100s not allowed because %s exists", pw->pw_name, nl); if ((f = fopen(nl, "r")) != NULL) { while (fgets(buf, sizeof(buf), f)) fputs(buf, stderr); fclose(f); } exit(254); } /* * Chroot into a directory after checking it for safety: all path components * must be root-owned directories with strict permissions. */ static void safely_chroot(const char *path, uid_t uid) { const char *cp; char component[PATH_MAX]; struct stat st; if (!path_absolute(path)) fatal("chroot path does not begin at root"); if (strlen(path) >= sizeof(component)) fatal("chroot path too long"); /* * Descend the path, checking that each component is a * root-owned directory with strict permissions. */ for (cp = path; cp != NULL;) { if ((cp = strchr(cp, '/')) == NULL) strlcpy(component, path, sizeof(component)); else { cp++; memcpy(component, path, cp - path); component[cp - path] = '\0'; } debug3_f("checking '%s'", component); if (stat(component, &st) != 0) fatal_f("stat(\"%s\"): %s", component, strerror(errno)); if (st.st_uid != 0 || (st.st_mode & 022) != 0) fatal("bad ownership or modes for chroot " "directory %s\"%s\"", cp == NULL ? "" : "component ", component); if (!S_ISDIR(st.st_mode)) fatal("chroot path %s\"%s\" is not a directory", cp == NULL ? "" : "component ", component); } if (chdir(path) == -1) fatal("Unable to chdir to chroot path \"%s\": " "%s", path, strerror(errno)); if (chroot(path) == -1) fatal("chroot(\"%s\"): %s", path, strerror(errno)); if (chdir("/") == -1) fatal_f("chdir(/) after chroot: %s", strerror(errno)); verbose("Changed root directory to \"%s\"", path); } /* Set login name, uid, gid, and groups. */ void do_setusercontext(struct passwd *pw) { char uidstr[32], *chroot_path, *tmp; if (getuid() == 0 || geteuid() == 0) { /* Prepare groups */ if (setusercontext(lc, pw, pw->pw_uid, (LOGIN_SETALL & ~(LOGIN_SETPATH|LOGIN_SETUSER))) < 0) { perror("unable to set user context"); exit(1); } if (!in_chroot && options.chroot_directory != NULL && strcasecmp(options.chroot_directory, "none") != 0) { tmp = tilde_expand_filename(options.chroot_directory, pw->pw_uid); snprintf(uidstr, sizeof(uidstr), "%llu", (unsigned long long)pw->pw_uid); chroot_path = percent_expand(tmp, "h", pw->pw_dir, "u", pw->pw_name, "U", uidstr, (char *)NULL); safely_chroot(chroot_path, pw->pw_uid); free(tmp); free(chroot_path); /* Make sure we don't attempt to chroot again */ free(options.chroot_directory); options.chroot_directory = NULL; in_chroot = 1; } /* Set UID */ if (setusercontext(lc, pw, pw->pw_uid, LOGIN_SETUSER) < 0) { perror("unable to set user context (setuser)"); exit(1); } } else if (options.chroot_directory != NULL && strcasecmp(options.chroot_directory, "none") != 0) { fatal("server lacks privileges to chroot to ChrootDirectory"); } if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) fatal("Failed to set uids to %u.", (u_int) pw->pw_uid); } static void do_pwchange(Session *s) { fflush(NULL); fprintf(stderr, "WARNING: Your password has expired.\n"); if (s->ttyfd != -1) { fprintf(stderr, "You must change your password now and login again!\n"); execl(_PATH_PASSWD_PROG, "passwd", (char *)NULL); perror("passwd"); } else { fprintf(stderr, "Password change required but no TTY available.\n"); } exit(1); } static void child_close_fds(struct ssh *ssh) { extern int auth_sock; if (auth_sock != -1) { close(auth_sock); auth_sock = -1; } if (ssh_packet_get_connection_in(ssh) == ssh_packet_get_connection_out(ssh)) close(ssh_packet_get_connection_in(ssh)); else { close(ssh_packet_get_connection_in(ssh)); close(ssh_packet_get_connection_out(ssh)); } /* * Close all descriptors related to channels. They will still remain * open in the parent. */ /* XXX better use close-on-exec? -markus */ channel_close_all(ssh); /* * Close any extra file descriptors. Note that there may still be * descriptors left by system functions. They will be closed later. */ endpwent(); /* Stop directing logs to a high-numbered fd before we close it */ log_redirect_stderr_to(NULL); /* * 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. */ closefrom(STDERR_FILENO + 1); } /* * 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. */ #define ARGV_MAX 10 void do_child(struct ssh *ssh, Session *s, const char *command) { extern char **environ; char **env, *argv[ARGV_MAX], remote_id[512]; const char *shell, *shell0; struct passwd *pw = s->pw; int r = 0; sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); /* remove hostkey from the child's memory */ destroy_sensitive_data(); ssh_packet_clear_keys(ssh); /* Force a password change */ if (s->authctxt->force_pwchange) { do_setusercontext(pw); child_close_fds(ssh); do_pwchange(s); exit(1); } /* * Login(1) does this as well, and it needs uid 0 for the "-h" * switch, so we let login(1) to this for us. */ do_nologin(pw); do_setusercontext(pw); /* * 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; /* * Make sure $SHELL points to the shell from the password file, * even if shell is overridden from login.conf */ env = do_setup_env(ssh, s, shell); shell = login_getcapstr(lc, "shell", (char *)shell, (char *)shell); /* * 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 * ssh_remote_ipaddr there. */ child_close_fds(ssh); /* * Must take new environment into use so that .ssh/rc, * /etc/ssh/sshrc and xauth are run in the proper environment. */ environ = env; #ifdef KRB5 /* * At this point, we check to see if AFS is active and if we have * a valid Kerberos 5 TGT. If so, it seems like a good idea to see * if we can (and need to) extend the ticket into an AFS token. If * we don't do this, we run into potential problems if the user's * home directory is in AFS and it's not world-readable. */ if (options.kerberos_get_afs_token && k_hasafs() && (s->authctxt->krb5_ctx != NULL)) { char cell[64]; debug("Getting AFS token"); k_setpag(); if (k_afs_cell_of_file(pw->pw_dir, cell, sizeof(cell)) == 0) krb5_afslog(s->authctxt->krb5_ctx, s->authctxt->krb5_fwd_ccache, cell, NULL); krb5_afslog_home(s->authctxt->krb5_ctx, s->authctxt->krb5_fwd_ccache, NULL, NULL, pw->pw_dir); } #endif /* Change current directory to the user's home directory. */ if (chdir(pw->pw_dir) == -1) { /* Suppress missing homedir warning for chroot case */ r = login_getcapbool(lc, "requirehome", 0); if (r || !in_chroot) { fprintf(stderr, "Could not chdir to home " "directory %s: %s\n", pw->pw_dir, strerror(errno)); } if (r) exit(1); } closefrom(STDERR_FILENO + 1); do_rc_files(ssh, s, shell); /* restore SIGPIPE for child */ ssh_signal(SIGPIPE, SIG_DFL); if (s->is_subsystem == SUBSYSTEM_INT_SFTP_ERROR) { error("Connection from %s: refusing non-sftp session", remote_id); printf("This service allows sftp connections only.\n"); fflush(NULL); exit(1); } else if (s->is_subsystem == SUBSYSTEM_INT_SFTP) { extern int optind, optreset; int i; char *p, *args; setproctitle("%s@%s", s->pw->pw_name, INTERNAL_SFTP_NAME); args = xstrdup(command ? command : "sftp-server"); for (i = 0, (p = strtok(args, " ")); p; (p = strtok(NULL, " "))) if (i < ARGV_MAX - 1) argv[i++] = p; argv[i] = NULL; optind = optreset = 1; __progname = argv[0]; exit(sftp_server_main(i, argv, s->pw)); } fflush(NULL); /* Get the last component of the shell name. */ if ((shell0 = strrchr(shell, '/')) != NULL) shell0++; else shell0 = 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) { char argv0[256]; /* Start the shell. Set initial character to '-'. */ argv0[0] = '-'; if (strlcpy(argv0 + 1, shell0, sizeof(argv0) - 1) >= sizeof(argv0) - 1) { errno = EINVAL; perror(shell); exit(1); } /* Execute the shell. */ argv[0] = argv0; argv[1] = NULL; execve(shell, argv, env); /* Executing the shell failed. */ perror(shell); exit(1); } /* * Execute the command using the user's shell. This uses the -c * option to execute the command. */ argv[0] = (char *) shell0; argv[1] = "-c"; argv[2] = (char *) command; argv[3] = NULL; execve(shell, argv, env); perror(shell); exit(1); } void session_unused(int id) { debug3_f("session id %d unused", id); if (id >= options.max_sessions || id >= sessions_nalloc) { fatal_f("insane session id %d (max %d nalloc %d)", id, options.max_sessions, sessions_nalloc); } memset(&sessions[id], 0, sizeof(*sessions)); sessions[id].self = id; sessions[id].used = 0; sessions[id].chanid = -1; sessions[id].ptyfd = -1; sessions[id].ttyfd = -1; sessions[id].ptymaster = -1; sessions[id].x11_chanids = NULL; sessions[id].next_unused = sessions_first_unused; sessions_first_unused = id; } Session * session_new(void) { Session *s, *tmp; if (sessions_first_unused == -1) { if (sessions_nalloc >= options.max_sessions) return NULL; debug2_f("allocate (allocated %d max %d)", sessions_nalloc, options.max_sessions); tmp = xrecallocarray(sessions, sessions_nalloc, sessions_nalloc + 1, sizeof(*sessions)); if (tmp == NULL) { error_f("cannot allocate %d sessions", sessions_nalloc + 1); return NULL; } sessions = tmp; session_unused(sessions_nalloc++); } if (sessions_first_unused >= sessions_nalloc || sessions_first_unused < 0) { fatal_f("insane first_unused %d max %d nalloc %d", sessions_first_unused, options.max_sessions, sessions_nalloc); } s = &sessions[sessions_first_unused]; if (s->used) fatal_f("session %d already used", sessions_first_unused); sessions_first_unused = s->next_unused; s->used = 1; s->next_unused = -1; debug("session_new: session %d", s->self); return s; } static void session_dump(void) { int i; for (i = 0; i < sessions_nalloc; i++) { Session *s = &sessions[i]; debug("dump: used %d next_unused %d session %d " "channel %d pid %ld", s->used, s->next_unused, s->self, s->chanid, (long)s->pid); } } int session_open(Authctxt *authctxt, int chanid) { Session *s = session_new(); debug("session_open: channel %d", chanid); if (s == NULL) { error("no more sessions"); return 0; } s->authctxt = authctxt; s->pw = authctxt->pw; if (s->pw == NULL || !authctxt->valid) fatal("no user for session %d", s->self); debug("session_open: session %d: link with channel %d", s->self, chanid); s->chanid = chanid; return 1; } Session * session_by_tty(char *tty) { int i; for (i = 0; i < sessions_nalloc; i++) { Session *s = &sessions[i]; if (s->used && s->ttyfd != -1 && strcmp(s->tty, tty) == 0) { debug("session_by_tty: session %d tty %s", i, tty); return s; } } debug("session_by_tty: unknown tty %.100s", tty); session_dump(); return NULL; } static Session * session_by_channel(int id) { int i; for (i = 0; i < sessions_nalloc; i++) { Session *s = &sessions[i]; if (s->used && s->chanid == id) { debug("session_by_channel: session %d channel %d", i, id); return s; } } debug("session_by_channel: unknown channel %d", id); session_dump(); return NULL; } static Session * session_by_x11_channel(int id) { int i, j; for (i = 0; i < sessions_nalloc; i++) { Session *s = &sessions[i]; if (s->x11_chanids == NULL || !s->used) continue; for (j = 0; s->x11_chanids[j] != -1; j++) { if (s->x11_chanids[j] == id) { debug("session_by_x11_channel: session %d " "channel %d", s->self, id); return s; } } } debug("session_by_x11_channel: unknown channel %d", id); session_dump(); return NULL; } static Session * session_by_pid(pid_t pid) { int i; debug("session_by_pid: pid %ld", (long)pid); for (i = 0; i < sessions_nalloc; i++) { Session *s = &sessions[i]; if (s->used && s->pid == pid) return s; } error("session_by_pid: unknown pid %ld", (long)pid); session_dump(); return NULL; } static int session_window_change_req(struct ssh *ssh, Session *s) { int r; if ((r = sshpkt_get_u32(ssh, &s->col)) != 0 || (r = sshpkt_get_u32(ssh, &s->row)) != 0 || (r = sshpkt_get_u32(ssh, &s->xpixel)) != 0 || (r = sshpkt_get_u32(ssh, &s->ypixel)) != 0 || (r = sshpkt_get_end(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: parse packet", __func__); pty_change_window_size(s->ptyfd, s->row, s->col, s->xpixel, s->ypixel); return 1; } static int session_pty_req(struct ssh *ssh, Session *s) { int r; if (!auth_opts->permit_pty_flag || !options.permit_tty) { debug("Allocating a pty not permitted for this connection."); return 0; } if (s->ttyfd != -1) { ssh_packet_disconnect(ssh, "Protocol error: you already have a pty."); return 0; } if ((r = sshpkt_get_cstring(ssh, &s->term, NULL)) != 0 || (r = sshpkt_get_u32(ssh, &s->col)) != 0 || (r = sshpkt_get_u32(ssh, &s->row)) != 0 || (r = sshpkt_get_u32(ssh, &s->xpixel)) != 0 || (r = sshpkt_get_u32(ssh, &s->ypixel)) != 0) sshpkt_fatal(ssh, r, "%s: parse packet", __func__); if (strcmp(s->term, "") == 0) { free(s->term); s->term = NULL; } /* Allocate a pty and open it. */ debug("Allocating pty."); if (!PRIVSEP(pty_allocate(&s->ptyfd, &s->ttyfd, s->tty, sizeof(s->tty)))) { free(s->term); s->term = NULL; s->ptyfd = -1; s->ttyfd = -1; error("session_pty_req: session %d alloc failed", s->self); return 0; } debug("session_pty_req: session %d alloc %s", s->self, s->tty); ssh_tty_parse_modes(ssh, s->ttyfd); if ((r = sshpkt_get_end(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: parse packet", __func__); if (!use_privsep) pty_setowner(s->pw, s->tty); /* Set window size from the packet. */ pty_change_window_size(s->ptyfd, s->row, s->col, s->xpixel, s->ypixel); session_proctitle(s); return 1; } static int session_subsystem_req(struct ssh *ssh, Session *s) { struct stat st; int r, success = 0; char *prog, *cmd; u_int i; if ((r = sshpkt_get_cstring(ssh, &s->subsys, NULL)) != 0 || (r = sshpkt_get_end(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: parse packet", __func__); debug2("subsystem request for %.100s by user %s", s->subsys, s->pw->pw_name); for (i = 0; i < options.num_subsystems; i++) { if (strcmp(s->subsys, options.subsystem_name[i]) == 0) { prog = options.subsystem_command[i]; cmd = options.subsystem_args[i]; if (strcmp(INTERNAL_SFTP_NAME, prog) == 0) { s->is_subsystem = SUBSYSTEM_INT_SFTP; debug("subsystem: %s", prog); } else { if (stat(prog, &st) == -1) debug("subsystem: cannot stat %s: %s", prog, strerror(errno)); s->is_subsystem = SUBSYSTEM_EXT; debug("subsystem: exec() %s", cmd); } success = do_exec(ssh, s, cmd) == 0; break; } } if (!success) logit("subsystem request for %.100s by user %s failed, " "subsystem not found", s->subsys, s->pw->pw_name); return success; } static int session_x11_req(struct ssh *ssh, Session *s) { int r, success; u_char single_connection = 0; if (s->auth_proto != NULL || s->auth_data != NULL) { error("session_x11_req: session %d: " "x11 forwarding already active", s->self); return 0; } if ((r = sshpkt_get_u8(ssh, &single_connection)) != 0 || (r = sshpkt_get_cstring(ssh, &s->auth_proto, NULL)) != 0 || (r = sshpkt_get_cstring(ssh, &s->auth_data, NULL)) != 0 || (r = sshpkt_get_u32(ssh, &s->screen)) != 0 || (r = sshpkt_get_end(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: parse packet", __func__); s->single_connection = single_connection; if (xauth_valid_string(s->auth_proto) && xauth_valid_string(s->auth_data)) success = session_setup_x11fwd(ssh, s); else { success = 0; error("Invalid X11 forwarding data"); } if (!success) { free(s->auth_proto); free(s->auth_data); s->auth_proto = NULL; s->auth_data = NULL; } return success; } static int session_shell_req(struct ssh *ssh, Session *s) { int r; if ((r = sshpkt_get_end(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: parse packet", __func__); return do_exec(ssh, s, NULL) == 0; } static int session_exec_req(struct ssh *ssh, Session *s) { u_int success; int r; char *command = NULL; if ((r = sshpkt_get_cstring(ssh, &command, NULL)) != 0 || (r = sshpkt_get_end(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: parse packet", __func__); success = do_exec(ssh, s, command) == 0; free(command); return success; } static int session_break_req(struct ssh *ssh, Session *s) { int r; if ((r = sshpkt_get_u32(ssh, NULL)) != 0 || /* ignore */ (r = sshpkt_get_end(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: parse packet", __func__); if (s->ptymaster == -1 || tcsendbreak(s->ptymaster, 0) == -1) return 0; return 1; } static int session_env_req(struct ssh *ssh, Session *s) { char *name, *val; u_int i; int r; if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0 || (r = sshpkt_get_cstring(ssh, &val, NULL)) != 0 || (r = sshpkt_get_end(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: parse packet", __func__); /* Don't set too many environment variables */ if (s->num_env > 128) { debug2("Ignoring env request %s: too many env vars", name); goto fail; } for (i = 0; i < options.num_accept_env; i++) { if (match_pattern(name, options.accept_env[i])) { debug2("Setting env %d: %s=%s", s->num_env, name, val); s->env = xrecallocarray(s->env, s->num_env, s->num_env + 1, sizeof(*s->env)); s->env[s->num_env].name = name; s->env[s->num_env].val = val; s->num_env++; return (1); } } debug2("Ignoring env request %s: disallowed name", name); fail: free(name); free(val); return (0); } /* * Conversion of signals from ssh channel request names. * Subset of signals from RFC 4254 section 6.10C, with SIGINFO as * local extension. */ static int name2sig(char *name) { #define SSH_SIG(x) if (strcmp(name, #x) == 0) return SIG ## x SSH_SIG(HUP); SSH_SIG(INT); SSH_SIG(KILL); SSH_SIG(QUIT); SSH_SIG(TERM); SSH_SIG(USR1); SSH_SIG(USR2); #undef SSH_SIG if (strcmp(name, "INFO@openssh.com") == 0) return SIGINFO; return -1; } static int session_signal_req(struct ssh *ssh, Session *s) { char *signame = NULL; int r, sig, success = 0; if ((r = sshpkt_get_cstring(ssh, &signame, NULL)) != 0 || (r = sshpkt_get_end(ssh)) != 0) { error_fr(r, "parse"); goto out; } if ((sig = name2sig(signame)) == -1) { error_f("unsupported signal \"%s\"", signame); goto out; } if (s->pid <= 0) { error_f("no pid for session %d", s->self); goto out; } if (s->forced || s->is_subsystem) { error_f("refusing to send signal %s to %s session", signame, s->forced ? "forced-command" : "subsystem"); goto out; } if (!use_privsep || mm_is_monitor()) { error_f("session signalling requires privilege separation"); goto out; } debug_f("signal %s, killpg(%ld, %d)", signame, (long)s->pid, sig); temporarily_use_uid(s->pw); r = killpg(s->pid, sig); restore_uid(); if (r != 0) { error_f("killpg(%ld, %d): %s", (long)s->pid, sig, strerror(errno)); goto out; } /* success */ success = 1; out: free(signame); return success; } static int session_auth_agent_req(struct ssh *ssh, Session *s) { static int called = 0; int r; if ((r = sshpkt_get_end(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: parse packet", __func__); if (!auth_opts->permit_agent_forwarding_flag || !options.allow_agent_forwarding) { debug_f("agent forwarding disabled"); return 0; } if (called) { return 0; } else { called = 1; return auth_input_request_forwarding(ssh, s->pw); } } int session_input_channel_req(struct ssh *ssh, Channel *c, const char *rtype) { int success = 0; Session *s; if ((s = session_by_channel(c->self)) == NULL) { logit_f("no session %d req %.100s", c->self, rtype); return 0; } debug_f("session %d req %s", s->self, rtype); /* * a session is in LARVAL state until a shell, a command * or a subsystem is executed */ if (c->type == SSH_CHANNEL_LARVAL) { if (strcmp(rtype, "shell") == 0) { success = session_shell_req(ssh, s); } else if (strcmp(rtype, "exec") == 0) { success = session_exec_req(ssh, s); } else if (strcmp(rtype, "pty-req") == 0) { success = session_pty_req(ssh, s); } else if (strcmp(rtype, "x11-req") == 0) { success = session_x11_req(ssh, s); } else if (strcmp(rtype, "auth-agent-req@openssh.com") == 0) { success = session_auth_agent_req(ssh, s); } else if (strcmp(rtype, "subsystem") == 0) { success = session_subsystem_req(ssh, s); } else if (strcmp(rtype, "env") == 0) { success = session_env_req(ssh, s); } } if (strcmp(rtype, "window-change") == 0) { success = session_window_change_req(ssh, s); } else if (strcmp(rtype, "break") == 0) { success = session_break_req(ssh, s); } else if (strcmp(rtype, "signal") == 0) { success = session_signal_req(ssh, s); } return success; } void session_set_fds(struct ssh *ssh, Session *s, int fdin, int fdout, int fderr, int ignore_fderr, int is_tty) { /* * now that have a child and a pipe to the child, * we can activate our channel and register the fd's */ if (s->chanid == -1) fatal("no channel for session %d", s->self); channel_set_fds(ssh, s->chanid, fdout, fdin, fderr, ignore_fderr ? CHAN_EXTENDED_IGNORE : CHAN_EXTENDED_READ, 1, is_tty, CHAN_SES_WINDOW_DEFAULT); } /* * Function to perform pty cleanup. Also called if we get aborted abnormally * (e.g., due to a dropped connection). */ void session_pty_cleanup2(Session *s) { if (s == NULL) { error_f("no session"); return; } if (s->ttyfd == -1) return; debug_f("session %d release %s", s->self, s->tty); /* Record that the user has logged out. */ if (s->pid != 0) record_logout(s->pid, s->tty); /* Release the pseudo-tty. */ if (getuid() == 0) pty_release(s->tty); /* * 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. */ if (s->ptymaster != -1 && close(s->ptymaster) == -1) error("close(s->ptymaster/%d): %s", s->ptymaster, strerror(errno)); /* unlink pty from session */ s->ttyfd = -1; } void session_pty_cleanup(Session *s) { PRIVSEP(session_pty_cleanup2(s)); } static char * sig2name(int sig) { #define SSH_SIG(x) if (sig == SIG ## x) return #x SSH_SIG(ABRT); SSH_SIG(ALRM); SSH_SIG(FPE); SSH_SIG(HUP); SSH_SIG(ILL); SSH_SIG(INT); SSH_SIG(KILL); SSH_SIG(PIPE); SSH_SIG(QUIT); SSH_SIG(SEGV); SSH_SIG(TERM); SSH_SIG(USR1); SSH_SIG(USR2); #undef SSH_SIG return "SIG@openssh.com"; } static void session_close_x11(struct ssh *ssh, int id) { Channel *c; if ((c = channel_by_id(ssh, id)) == NULL) { debug_f("x11 channel %d missing", id); } else { /* Detach X11 listener */ debug_f("detach x11 channel %d", id); channel_cancel_cleanup(ssh, id); if (c->ostate != CHAN_OUTPUT_CLOSED) chan_mark_dead(ssh, c); } } static void session_close_single_x11(struct ssh *ssh, int id, void *arg) { Session *s; u_int i; debug3_f("channel %d", id); channel_cancel_cleanup(ssh, id); if ((s = session_by_x11_channel(id)) == NULL) fatal_f("no x11 channel %d", id); for (i = 0; s->x11_chanids[i] != -1; i++) { debug_f("session %d: closing channel %d", s->self, s->x11_chanids[i]); /* * The channel "id" is already closing, but make sure we * close all of its siblings. */ if (s->x11_chanids[i] != id) session_close_x11(ssh, s->x11_chanids[i]); } free(s->x11_chanids); s->x11_chanids = NULL; free(s->display); s->display = NULL; free(s->auth_proto); s->auth_proto = NULL; free(s->auth_data); s->auth_data = NULL; free(s->auth_display); s->auth_display = NULL; } static void session_exit_message(struct ssh *ssh, Session *s, int status) { Channel *c; int r; if ((c = channel_lookup(ssh, s->chanid)) == NULL) fatal_f("session %d: no channel %d", s->self, s->chanid); debug_f("session %d channel %d pid %ld", s->self, s->chanid, (long)s->pid); if (WIFEXITED(status)) { channel_request_start(ssh, s->chanid, "exit-status", 0); if ((r = sshpkt_put_u32(ssh, WEXITSTATUS(status))) != 0 || (r = sshpkt_send(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: exit reply", __func__); } else if (WIFSIGNALED(status)) { channel_request_start(ssh, s->chanid, "exit-signal", 0); if ((r = sshpkt_put_cstring(ssh, sig2name(WTERMSIG(status)))) != 0 || (r = sshpkt_put_u8(ssh, WCOREDUMP(status)? 1 : 0)) != 0 || (r = sshpkt_put_cstring(ssh, "")) != 0 || (r = sshpkt_put_cstring(ssh, "")) != 0 || (r = sshpkt_send(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: exit reply", __func__); } else { /* Some weird exit cause. Just exit. */ ssh_packet_disconnect(ssh, "wait returned status %04x.", status); } /* disconnect channel */ debug_f("release channel %d", s->chanid); /* * Adjust cleanup callback attachment to send close messages when * the channel gets EOF. The session will be then be closed * by session_close_by_channel when the child sessions close their fds. */ channel_register_cleanup(ssh, c->self, session_close_by_channel, 1); /* * emulate a write failure with 'chan_write_failed', nobody will be * interested in data we write. * Note that we must not call 'chan_read_failed', since there could * be some more data waiting in the pipe. */ if (c->ostate != CHAN_OUTPUT_CLOSED) chan_write_failed(ssh, c); } void session_close(struct ssh *ssh, Session *s) { u_int i; verbose("Close session: user %s from %.200s port %d id %d", s->pw->pw_name, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), s->self); if (s->ttyfd != -1) session_pty_cleanup(s); free(s->term); free(s->display); free(s->x11_chanids); free(s->auth_display); free(s->auth_data); free(s->auth_proto); free(s->subsys); if (s->env != NULL) { for (i = 0; i < s->num_env; i++) { free(s->env[i].name); free(s->env[i].val); } free(s->env); } session_proctitle(s); session_unused(s->self); } void session_close_by_pid(struct ssh *ssh, pid_t pid, int status) { Session *s = session_by_pid(pid); if (s == NULL) { debug_f("no session for pid %ld", (long)pid); return; } if (s->chanid != -1) session_exit_message(ssh, s, status); if (s->ttyfd != -1) session_pty_cleanup(s); s->pid = 0; } /* * this is called when a channel dies before * the session 'child' itself dies */ void session_close_by_channel(struct ssh *ssh, int id, void *arg) { Session *s = session_by_channel(id); u_int i; if (s == NULL) { debug_f("no session for id %d", id); return; } debug_f("channel %d child %ld", id, (long)s->pid); if (s->pid != 0) { debug_f("channel %d: has child, ttyfd %d", id, s->ttyfd); /* * delay detach of session, but release pty, since * the fd's to the child are already closed */ if (s->ttyfd != -1) session_pty_cleanup(s); return; } /* detach by removing callback */ channel_cancel_cleanup(ssh, s->chanid); /* Close any X11 listeners associated with this session */ if (s->x11_chanids != NULL) { for (i = 0; s->x11_chanids[i] != -1; i++) { session_close_x11(ssh, s->x11_chanids[i]); s->x11_chanids[i] = -1; } } s->chanid = -1; session_close(ssh, s); } void session_destroy_all(struct ssh *ssh, void (*closefunc)(Session *)) { int i; for (i = 0; i < sessions_nalloc; i++) { Session *s = &sessions[i]; if (s->used) { if (closefunc != NULL) closefunc(s); else session_close(ssh, s); } } } static char * session_tty_list(void) { static char buf[1024]; int i; buf[0] = '\0'; for (i = 0; i < sessions_nalloc; i++) { Session *s = &sessions[i]; if (s->used && s->ttyfd != -1) { if (buf[0] != '\0') strlcat(buf, ",", sizeof buf); strlcat(buf, strrchr(s->tty, '/') + 1, sizeof buf); } } if (buf[0] == '\0') strlcpy(buf, "notty", sizeof buf); return buf; } void session_proctitle(Session *s) { if (s->pw == NULL) error("no user for session %d", s->self); else setproctitle("%s@%s", s->pw->pw_name, session_tty_list()); } int session_setup_x11fwd(struct ssh *ssh, Session *s) { struct stat st; char display[512], auth_display[512]; char hostname[NI_MAXHOST]; u_int i; if (!auth_opts->permit_x11_forwarding_flag) { ssh_packet_send_debug(ssh, "X11 forwarding disabled by key options."); return 0; } if (!options.x11_forwarding) { debug("X11 forwarding disabled in server configuration file."); return 0; } if (options.xauth_location == NULL || (stat(options.xauth_location, &st) == -1)) { ssh_packet_send_debug(ssh, "No xauth program; cannot forward X11."); return 0; } if (s->display != NULL) { debug("X11 display already set."); return 0; } if (x11_create_display_inet(ssh, options.x11_display_offset, options.x11_use_localhost, s->single_connection, &s->display_number, &s->x11_chanids) == -1) { debug("x11_create_display_inet failed."); return 0; } for (i = 0; s->x11_chanids[i] != -1; i++) { channel_register_cleanup(ssh, s->x11_chanids[i], session_close_single_x11, 0); } /* Set up a suitable value for the DISPLAY variable. */ if (gethostname(hostname, sizeof(hostname)) == -1) fatal("gethostname: %.100s", strerror(errno)); /* * auth_display must be used as the displayname when the * authorization entry is added with xauth(1). This will be * different than the DISPLAY string for localhost displays. */ if (options.x11_use_localhost) { snprintf(display, sizeof display, "localhost:%u.%u", s->display_number, s->screen); snprintf(auth_display, sizeof auth_display, "unix:%u.%u", s->display_number, s->screen); s->display = xstrdup(display); s->auth_display = xstrdup(auth_display); } else { snprintf(display, sizeof display, "%.400s:%u.%u", hostname, s->display_number, s->screen); s->display = xstrdup(display); s->auth_display = xstrdup(display); } return 1; } static void do_authenticated2(struct ssh *ssh, Authctxt *authctxt) { server_loop2(ssh, authctxt); } void do_cleanup(struct ssh *ssh, Authctxt *authctxt) { static int called = 0; debug("do_cleanup"); /* no cleanup if we're in the child for login shell */ if (is_child) return; /* avoid double cleanup */ if (called) return; called = 1; if (authctxt == NULL || !authctxt->authenticated) return; #ifdef KRB5 if (options.kerberos_ticket_cleanup && authctxt->krb5_ctx) krb5_cleanup_proc(authctxt); #endif #ifdef GSSAPI if (options.gss_cleanup_creds) ssh_gssapi_cleanup_creds(); #endif /* remove agent socket */ auth_sock_cleanup_proc(authctxt->pw); /* remove userauth info */ if (auth_info_file != NULL) { temporarily_use_uid(authctxt->pw); unlink(auth_info_file); restore_uid(); free(auth_info_file); auth_info_file = NULL; } /* * Cleanup ptys/utmp only if privsep is disabled, * or if running in monitor. */ if (!use_privsep || mm_is_monitor()) session_destroy_all(ssh, session_pty_cleanup2); } /* Return a name for the remote host that fits inside utmp_size */ const char * session_get_remote_name_or_ip(struct ssh *ssh, u_int utmp_size, int use_dns) { const char *remote = ""; if (utmp_size > 0) remote = auth_get_canonical_hostname(ssh, use_dns); if (utmp_size == 0 || strlen(remote) > utmp_size) remote = ssh_remote_ipaddr(ssh); return remote; }