File: [local] / src / usr.bin / ssh / session.c (download)
Revision 1.338, Fri May 17 00:30:24 2024 UTC (2 weeks, 1 day ago) by djm
Branch: MAIN
CVS Tags: HEAD
Changes since 1.337: +5 -18 lines
Start the process of splitting sshd into separate binaries. This step
splits sshd into a listener and a session binary. More splits are
planned.
After this changes, the listener binary will validate the configuration,
load the hostkeys, listen on port 22 and manage MaxStartups only. All
session handling will be performed by a new sshd-session binary that the
listener fork+execs.
This reduces the listener process to the minimum necessary and sets us
up for future work on the sshd-session binary.
feedback/ok markus@ deraadt@
NB. if you're updating via source, please restart sshd after installing,
otherwise you run the risk of locking yourself out.
|
/* $OpenBSD: session.c,v 1.338 2024/05/17 00:30:24 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 "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-listener",
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 = hpdelim2(&cp, NULL)) == 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;
/*
* 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);
}
}
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);
free(cp);
}
/* 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 (!mm_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__);
/* 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, *type;
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);
}
xasprintf(&type, "session:subsystem:%s",
options.subsystem_name[i]);
channel_set_xtype(ssh, s->chanid, type);
free(type);
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__);
channel_set_xtype(ssh, s->chanid, "session:shell");
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__);
channel_set_xtype(ssh, s->chanid, "session:command");
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 (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)
{
mm_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, int force, 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;
char *note = NULL;
if ((c = channel_lookup(ssh, s->chanid)) == NULL)
fatal_f("session %d: no channel %d", s->self, s->chanid);
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__);
xasprintf(¬e, "exit %d", WEXITSTATUS(status));
} 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__);
xasprintf(¬e, "signal %d%s", WTERMSIG(status),
WCOREDUMP(status) ? " core dumped" : "");
} else {
/* Some weird exit cause. Just exit. */
ssh_packet_disconnect(ssh, "wait returned status %04x.",
status);
}
debug_f("session %d channel %d pid %ld %s", s->self, s->chanid,
(long)s->pid, note == NULL ? "UNKNOWN" : note);
free(note);
/* 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, int force, 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 (unless this is a forced close),
* but release pty, since the fd's to the child are already
* closed
*/
if (s->ttyfd != -1)
session_pty_cleanup(s);
if (!force)
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 (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;
}
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