OpenSolaris_b135/cmd/ssh/sshd/session.c
/*
* 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.
*/
/*
* Copyright 2010 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#include "includes.h"
RCSID("$OpenBSD: session.c,v 1.150 2002/09/16 19:55:33 stevesk Exp $");
#ifdef HAVE_DEFOPEN
#include <deflt.h>
#include <ulimit.h>
#endif /* HAVE_DEFOPEN */
#ifdef HAVE_LIBGEN_H
#include <libgen.h>
#endif
#include <priv.h>
#include "ssh.h"
#include "ssh1.h"
#include "ssh2.h"
#include "xmalloc.h"
#include "sshpty.h"
#include "packet.h"
#include "buffer.h"
#include "mpaux.h"
#include "uidswap.h"
#include "compat.h"
#include "channels.h"
#include "bufaux.h"
#include "auth.h"
#include "auth-options.h"
#include "pathnames.h"
#include "log.h"
#include "servconf.h"
#include "sshlogin.h"
#include "serverloop.h"
#include "canohost.h"
#include "session.h"
#include "tildexpand.h"
#include "misc.h"
#include "sftp.h"
#ifdef USE_PAM
#include <security/pam_appl.h>
#endif /* USE_PAM */
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#ifdef ALTPRIVSEP
#include "altprivsep.h"
#endif /* ALTPRIVSEP */
#ifdef HAVE_CYGWIN
#include <windows.h>
#include <sys/cygwin.h>
#define is_winnt (GetVersion() < 0x80000000)
#endif
/* func */
Session *session_new(void);
void session_set_fds(Session *, int, int, int);
void session_pty_cleanup(void *);
void session_xauthfile_cleanup(void *s);
void session_proctitle(Session *);
int session_setup_x11fwd(Session *);
void do_exec_pty(Session *, const char *);
void do_exec_no_pty(Session *, const char *);
void do_exec(Session *, const char *);
void do_login(Session *, const char *);
void do_child(Session *, const char *);
void do_motd(void);
int check_quietlogin(Session *, const char *);
static void do_authenticated1(Authctxt *);
static void do_authenticated2(Authctxt *);
static int session_pty_req(Session *);
static int session_env_req(Session *s);
static void session_free_env(char ***envp);
static void safely_chroot(const char *path, uid_t uid);
static void drop_privs(uid_t uid);
#ifdef USE_PAM
static void session_do_pam(Session *, int);
#endif /* USE_PAM */
/* import */
extern ServerOptions options;
extern char *__progname;
extern int log_stderr;
extern int debug_flag;
extern u_int utmp_len;
extern void destroy_sensitive_data(void);
#ifdef GSSAPI
extern Gssctxt *xxx_gssctxt;
#endif /* GSSAPI */
/* original command from peer. */
const char *original_command = NULL;
/* data */
#define MAX_SESSIONS 10
Session sessions[MAX_SESSIONS];
#define SUBSYSTEM_NONE 0
#define SUBSYSTEM_EXT 1
#define SUBSYSTEM_INT_SFTP 2
#ifdef HAVE_LOGIN_CAP
login_cap_t *lc;
#endif
/* 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(void *_pw)
{
struct passwd *pw = _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 passwd * pw)
{
Channel *nc;
int sock;
struct sockaddr_un sunaddr;
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_name = xmalloc(MAXPATHLEN);
auth_sock_dir = xmalloc(MAXPATHLEN);
strlcpy(auth_sock_dir, "/tmp/ssh-XXXXXXXX", MAXPATHLEN);
/* Create private directory for socket */
if (mkdtemp(auth_sock_dir) == NULL) {
packet_send_debug("Agent forwarding disabled: "
"mkdtemp() failed: %.100s", strerror(errno));
restore_uid();
xfree(auth_sock_name);
xfree(auth_sock_dir);
auth_sock_name = NULL;
auth_sock_dir = NULL;
return 0;
}
snprintf(auth_sock_name, MAXPATHLEN, "%s/agent.%ld",
auth_sock_dir, (long) getpid());
/* delete agent socket on fatal() */
fatal_add_cleanup(auth_sock_cleanup_proc, pw);
/* Create the socket. */
sock = socket(AF_UNIX, SOCK_STREAM, 0);
if (sock < 0)
packet_disconnect("socket: %.100s", strerror(errno));
/* Bind it to the name. */
memset(&sunaddr, 0, sizeof(sunaddr));
sunaddr.sun_family = AF_UNIX;
strlcpy(sunaddr.sun_path, auth_sock_name, sizeof(sunaddr.sun_path));
if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0)
packet_disconnect("bind: %.100s", strerror(errno));
/* Restore the privileged uid. */
restore_uid();
/* Start listening on the socket. */
if (listen(sock, 5) < 0)
packet_disconnect("listen: %.100s", strerror(errno));
/* Allocate a channel for the authentication agent socket. */
nc = channel_new("auth socket",
SSH_CHANNEL_AUTH_SOCKET, sock, sock, -1,
CHAN_X11_WINDOW_DEFAULT, CHAN_X11_PACKET_DEFAULT,
0, xstrdup("auth socket"), 1);
strlcpy(nc->path, auth_sock_name, sizeof(nc->path));
return 1;
}
void
do_authenticated(Authctxt *authctxt)
{
/* setup the channel layer */
if (!no_port_forwarding_flag && options.allow_tcp_forwarding)
channel_permit_all_opens();
if (compat20)
do_authenticated2(authctxt);
else
do_authenticated1(authctxt);
/* remove agent socket */
if (auth_sock_name != NULL)
auth_sock_cleanup_proc(authctxt->pw);
#ifdef KRB4
if (options.kerberos_ticket_cleanup)
krb4_cleanup_proc(authctxt);
#endif
#ifdef KRB5
if (options.kerberos_ticket_cleanup)
krb5_cleanup_proc(authctxt);
#endif
}
/*
* Prepares for an interactive session. This is called after the user has
* been successfully authenticated. During this message exchange, pseudo
* terminals are allocated, X11, TCP/IP, and authentication agent forwardings
* are requested, etc.
*/
static void
do_authenticated1(Authctxt *authctxt)
{
Session *s;
char *command;
int success, type, screen_flag;
int enable_compression_after_reply = 0;
u_int proto_len, data_len, dlen, compression_level = 0;
s = session_new();
s->authctxt = authctxt;
s->pw = authctxt->pw;
/*
* We stay in this loop until the client requests to execute a shell
* or a command.
*/
for (;;) {
success = 0;
/* Get a packet from the client. */
type = packet_read();
/* Process the packet. */
switch (type) {
case SSH_CMSG_REQUEST_COMPRESSION:
compression_level = packet_get_int();
packet_check_eom();
if (compression_level < 1 || compression_level > 9) {
packet_send_debug("Received illegal compression level %d.",
compression_level);
break;
}
if (!options.compression) {
debug2("compression disabled");
break;
}
/* Enable compression after we have responded with SUCCESS. */
enable_compression_after_reply = 1;
success = 1;
break;
case SSH_CMSG_REQUEST_PTY:
success = session_pty_req(s);
break;
case SSH_CMSG_X11_REQUEST_FORWARDING:
s->auth_proto = packet_get_string(&proto_len);
s->auth_data = packet_get_string(&data_len);
screen_flag = packet_get_protocol_flags() &
SSH_PROTOFLAG_SCREEN_NUMBER;
debug2("SSH_PROTOFLAG_SCREEN_NUMBER: %d", screen_flag);
if (packet_remaining() == 4) {
if (!screen_flag)
debug2("Buggy client: "
"X11 screen flag missing");
s->screen = packet_get_int();
} else {
s->screen = 0;
}
packet_check_eom();
success = session_setup_x11fwd(s);
if (!success) {
xfree(s->auth_proto);
xfree(s->auth_data);
s->auth_proto = NULL;
s->auth_data = NULL;
}
break;
case SSH_CMSG_AGENT_REQUEST_FORWARDING:
if (no_agent_forwarding_flag || compat13) {
debug("Authentication agent forwarding not permitted for this authentication.");
break;
}
debug("Received authentication agent forwarding request.");
success = auth_input_request_forwarding(s->pw);
break;
case SSH_CMSG_PORT_FORWARD_REQUEST:
if (no_port_forwarding_flag) {
debug("Port forwarding not permitted for this authentication.");
break;
}
if (!options.allow_tcp_forwarding) {
debug("Port forwarding not permitted.");
break;
}
debug("Received TCP/IP port forwarding request.");
channel_input_port_forward_request(s->pw->pw_uid == 0, options.gateway_ports);
success = 1;
break;
case SSH_CMSG_MAX_PACKET_SIZE:
if (packet_set_maxsize(packet_get_int()) > 0)
success = 1;
break;
#if defined(AFS) || defined(KRB5)
case SSH_CMSG_HAVE_KERBEROS_TGT:
if (!options.kerberos_tgt_passing) {
verbose("Kerberos TGT passing disabled.");
} else {
char *kdata = packet_get_string(&dlen);
packet_check_eom();
/* XXX - 0x41, see creds_to_radix version */
if (kdata[0] != 0x41) {
#ifdef KRB5
krb5_data tgt;
tgt.data = kdata;
tgt.length = dlen;
if (auth_krb5_tgt(s->authctxt, &tgt))
success = 1;
else
verbose("Kerberos v5 TGT refused for %.100s", s->authctxt->user);
#endif /* KRB5 */
} else {
#ifdef AFS
if (auth_krb4_tgt(s->authctxt, kdata))
success = 1;
else
verbose("Kerberos v4 TGT refused for %.100s", s->authctxt->user);
#endif /* AFS */
}
xfree(kdata);
}
break;
#endif /* AFS || KRB5 */
#ifdef AFS
case SSH_CMSG_HAVE_AFS_TOKEN:
if (!options.afs_token_passing || !k_hasafs()) {
verbose("AFS token passing disabled.");
} else {
/* Accept AFS token. */
char *token = packet_get_string(&dlen);
packet_check_eom();
if (auth_afs_token(s->authctxt, token))
success = 1;
else
verbose("AFS token refused for %.100s",
s->authctxt->user);
xfree(token);
}
break;
#endif /* AFS */
case SSH_CMSG_EXEC_SHELL:
case SSH_CMSG_EXEC_CMD:
if (type == SSH_CMSG_EXEC_CMD) {
command = packet_get_string(&dlen);
debug("Exec command '%.500s'", command);
do_exec(s, command);
xfree(command);
} else {
do_exec(s, NULL);
}
packet_check_eom();
session_close(s);
return;
default:
/*
* Any unknown messages in this phase are ignored,
* and a failure message is returned.
*/
log("Unknown packet type received after authentication: %d", type);
}
packet_start(success ? SSH_SMSG_SUCCESS : SSH_SMSG_FAILURE);
packet_send();
packet_write_wait();
/* Enable compression now that we have replied if appropriate. */
if (enable_compression_after_reply) {
enable_compression_after_reply = 0;
packet_start_compression(compression_level);
}
}
}
/*
* This is called to fork and execute a command when we have no tty. This
* will call do_child from the child, and server_loop from the parent after
* setting up file descriptors and such.
*/
void
do_exec_no_pty(Session *s, const char *command)
{
pid_t pid;
int inout[2], err[2];
/* Uses socket pairs to communicate with the program. */
if (socketpair(AF_UNIX, SOCK_STREAM, 0, inout) < 0 ||
socketpair(AF_UNIX, SOCK_STREAM, 0, err) < 0)
packet_disconnect("Could not create socket pairs: %.100s",
strerror(errno));
if (s == NULL)
fatal("do_exec_no_pty: no session");
session_proctitle(s);
/* Fork the child. */
if ((pid = fork()) == 0) {
fatal_remove_all_cleanups();
/* Child. Reinitialize the log since the pid has changed. */
log_init(__progname, options.log_level, options.log_facility, log_stderr);
/*
* Create a new session and process group since the 4.4BSD
* setlogin() affects the entire process group.
*/
if (setsid() < 0)
error("setsid failed: %.100s", strerror(errno));
/*
* Redirect stdin, stdout, and stderr. Stdin and stdout will
* use the same socket, as some programs (particularly rdist)
* seem to depend on it.
*/
close(inout[1]);
close(err[1]);
if (dup2(inout[0], 0) < 0) /* stdin */
perror("dup2 stdin");
if (dup2(inout[0], 1) < 0) /* stdout. Note: same socket as stdin. */
perror("dup2 stdout");
if (s->is_subsystem) {
/*
* Redirect the subsystem's stderr to /dev/null. We might send it
* over to the other side but changing that might break existing
* SSH clients.
*/
close(err[0]);
if ((err[0] = open(_PATH_DEVNULL, O_WRONLY)) == -1)
fatal("Cannot open /dev/null: %.100s", strerror(errno));
}
if (dup2(err[0], 2) < 0) /* stderr */
perror("dup2 stderr");
#ifdef _UNICOS
cray_init_job(s->pw); /* set up cray jid and tmpdir */
#endif
/* Do processing for the child (exec command etc). */
do_child(s, command);
/* NOTREACHED */
}
#ifdef _UNICOS
signal(WJSIGNAL, cray_job_termination_handler);
#endif /* _UNICOS */
#ifdef HAVE_CYGWIN
if (is_winnt)
cygwin_set_impersonation_token(INVALID_HANDLE_VALUE);
#endif
if (pid < 0)
packet_disconnect("fork failed: %.100s", strerror(errno));
s->pid = pid;
/* Set interactive/non-interactive mode. */
packet_set_interactive(s->display != NULL);
/* 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.
*/
if (compat20) {
session_set_fds(s, inout[1], inout[1], s->is_subsystem ? -1 : err[1]);
if (s->is_subsystem)
close(err[1]);
/* Don't close channel before sending exit-status! */
channel_set_wait_for_exit(s->chanid, 1);
} else {
server_loop(pid, inout[1], inout[1], err[1]);
/* server_loop has closed inout[1] and err[1]. */
}
}
/*
* This is called to fork and execute a command when we have a tty. This
* will call do_child from the child, and server_loop from the parent after
* setting up file descriptors, controlling tty, updating wtmp, utmp,
* lastlog, and other such operations.
*/
void
do_exec_pty(Session *s, const char *command)
{
int fdout, ptyfd, ttyfd, ptymaster, pipe_fds[2];
pid_t pid;
if (s == NULL)
fatal("do_exec_pty: no session");
ptyfd = s->ptyfd;
ttyfd = s->ttyfd;
#ifdef USE_PAM
session_do_pam(s, 1); /* pam_open_session() */
#endif /* USE_PAM */
/*
* This pipe lets sshd wait for child to exec or exit. This is
* particularly important for ALTPRIVSEP because the child is
* the one to call the monitor to request a record_login() and
* we don't want the child and the parent to compete for the
* monitor's attention. But this is generic code and doesn't
* hurt to have here even if ALTPRIVSEP is not used.
*/
if (pipe(pipe_fds) != 0)
packet_disconnect("pipe failed: %.100s", strerror(errno));
(void) fcntl(pipe_fds[0], F_SETFD, FD_CLOEXEC);
(void) fcntl(pipe_fds[1], F_SETFD, FD_CLOEXEC);
/* Fork the child. */
if ((pid = fork()) == 0) {
(void) close(pipe_fds[0]);
fatal_remove_all_cleanups();
/* Child. Reinitialize the log because the pid has changed. */
log_init(__progname, options.log_level, options.log_facility, log_stderr);
/* 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) < 0)
error("dup2 stdin: %s", strerror(errno));
if (dup2(ttyfd, 1) < 0)
error("dup2 stdout: %s", strerror(errno));
if (dup2(ttyfd, 2) < 0)
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(s, command);
/*
* Close the pipe to the parent so it can re-enter its event
* loop and service the ptm; if enough debug messages get
* written to the pty before this happens there will be a
* deadlock.
*/
close(pipe_fds[1]);
/*
* do_motd() was called originally in do_login(). However,
* when the /etc/motd file is large, a deadlock would happen,
* because
* - The child is blocked at fputs() to pty, when pty buffer
* is full.
* - The parent can not consume the pty buffer, because it is
* still blocked at read(pipe_fds[0]).
*
* To resolve the deadlock issue, we defer do_motd() after
* close(pipe_fds[1]).
*/
do_motd();
/* Do common processing for the child, such as execing the command. */
do_child(s, command);
/* NOTREACHED */
}
/* Wait for child to exec() or exit() */
(void) close(pipe_fds[1]);
(void) read(pipe_fds[0], &pipe_fds[1], sizeof(int));
#ifdef _UNICOS
signal(WJSIGNAL, cray_job_termination_handler);
#endif /* _UNICOS */
#ifdef HAVE_CYGWIN
if (is_winnt)
cygwin_set_impersonation_token(INVALID_HANDLE_VALUE);
#endif
if (pid < 0)
packet_disconnect("fork failed: %.100s", strerror(errno));
s->pid = pid;
/* Parent. Close the slave side of the pseudo tty. */
close(ttyfd);
/*
* Create another descriptor of the pty master side for use as the
* standard input. We could use the original descriptor, but this
* simplifies code in server_loop. The descriptor is bidirectional.
*/
fdout = dup(ptyfd);
if (fdout < 0)
packet_disconnect("dup #1 failed: %.100s", strerror(errno));
/* we keep a reference to the pty master */
ptymaster = dup(ptyfd);
if (ptymaster < 0)
packet_disconnect("dup #2 failed: %.100s", strerror(errno));
s->ptymaster = ptymaster;
/* Enter interactive session. */
packet_set_interactive(1);
if (compat20) {
session_set_fds(s, ptyfd, fdout, -1);
/* Don't close channel before sending exit-status! */
channel_set_wait_for_exit(s->chanid, 1);
} else {
server_loop(pid, ptyfd, fdout, -1);
/* server_loop _has_ closed ptyfd and fdout. */
}
}
/*
* This is called to fork and execute a command. If another command is
* to be forced, execute that instead.
*/
void
do_exec(Session *s, const char *command)
{
if (command)
s->command = xstrdup(command);
if (forced_command) {
original_command = command;
command = forced_command;
debug("Forced command '%.900s'", command);
}
if (s->ttyfd != -1)
do_exec_pty(s, command);
else
do_exec_no_pty(s, command);
original_command = NULL;
}
/* administrative, login(1)-like work */
void
do_login(Session *s, const char *command)
{
char *time_string;
#ifndef ALTPRIVSEP
struct passwd * pw = s->pw;
#endif /* ALTPRIVSEP*/
pid_t pid = getpid();
/* Record that there was a login on that tty from the remote host. */
#ifdef ALTPRIVSEP
debug3("Recording SSHv2 channel login in utmpx/wtmpx");
altprivsep_record_login(pid, s->tty);
#endif /* ALTPRIVSEP*/
if (check_quietlogin(s, command))
return;
#ifdef USE_PAM
print_pam_messages();
#endif /* USE_PAM */
#ifdef WITH_AIXAUTHENTICATE
if (aixloginmsg && *aixloginmsg)
printf("%s\n", aixloginmsg);
#endif /* WITH_AIXAUTHENTICATE */
#ifndef NO_SSH_LASTLOG
if (options.print_lastlog && s->last_login_time != 0) {
time_string = ctime(&s->last_login_time);
if (strchr(time_string, '\n'))
*strchr(time_string, '\n') = 0;
if (strcmp(s->hostname, "") == 0)
printf("Last login: %s\r\n", time_string);
else
printf("Last login: %s from %s\r\n", time_string,
s->hostname);
}
#endif /* NO_SSH_LASTLOG */
}
/*
* Display the message of the day.
*/
void
do_motd(void)
{
FILE *f;
char buf[256];
if (options.print_motd) {
#ifdef HAVE_LOGIN_CAP
f = fopen(login_getcapstr(lc, "welcome", "/etc/motd",
"/etc/motd"), "r");
#else
f = fopen("/etc/motd", "r");
#endif
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);
#ifdef HAVE_LOGIN_CAP
if (login_getcapbool(lc, "hushlogin", 0) || stat(buf, &st) >= 0)
return 1;
#else
if (stat(buf, &st) >= 0)
return 1;
#endif
return 0;
}
/*
* Sets the value of the given variable in the environment. If the variable
* already exists, its value is overriden.
*/
void
child_set_env(char ***envp, u_int *envsizep, const char *name,
const char *value)
{
debug3("child_set_env(%s, %s)", name, value);
child_set_env_silent(envp, envsizep, name, value);
}
void
child_set_env_silent(char ***envp, u_int *envsizep, const char *name,
const char *value)
{
u_int i, namelen;
char **env;
/*
* Find the slot where the value should be stored. If the variable
* already exists, we reuse the slot; otherwise we append a new slot
* at the end of the array, expanding if necessary.
*/
env = *envp;
namelen = strlen(name);
for (i = 0; env[i]; i++)
if (strncmp(env[i], name, namelen) == 0 && env[i][namelen] == '=')
break;
if (env[i]) {
/* Reuse the slot. */
xfree(env[i]);
} else {
/* New variable. Expand if necessary. */
if (i >= (*envsizep) - 1) {
if (*envsizep >= 1000)
fatal("child_set_env: too many env vars,"
" skipping: %.100s", name);
(*envsizep) += 50;
env = (*envp) = xrealloc(env, (*envsizep) * sizeof(char *));
}
/* Need to set the NULL pointer at end of array beyond the new slot. */
env[i + 1] = NULL;
}
/* Allocate space and format the variable in the appropriate slot. */
env[i] = xmalloc(strlen(name) + 1 + strlen(value) + 1);
snprintf(env[i], strlen(name) + 1 + strlen(value) + 1, "%s=%s", name, value);
}
/*
* Reads environment variables from the given file and adds/overrides them
* into the environment. If the file does not exist, this does nothing.
* Otherwise, it must consist of empty lines, comments (line starts with '#')
* and assignments of the form name=value. No other forms are allowed.
*/
static void
read_environment_file(char ***env, u_int *envsize,
const char *filename)
{
FILE *f;
char buf[4096];
char *cp, *value;
u_int lineno = 0;
f = fopen(filename, "r");
if (!f)
return;
while (fgets(buf, sizeof(buf), f)) {
if (++lineno > 1000)
fatal("Too many lines in environment file %s", filename);
for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
;
if (!*cp || *cp == '#' || *cp == '\n')
continue;
if (strchr(cp, '\n'))
*strchr(cp, '\n') = '\0';
value = strchr(cp, '=');
if (value == NULL) {
fprintf(stderr, gettext("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++;
child_set_env(env, envsize, cp, value);
}
fclose(f);
}
void copy_environment(char **source, char ***env, u_int *envsize)
{
char *var_name, *var_val;
int i;
if (source == NULL)
return;
for(i = 0; source[i] != NULL; i++) {
var_name = xstrdup(source[i]);
if ((var_val = strstr(var_name, "=")) == NULL) {
xfree(var_name);
continue;
}
*var_val++ = '\0';
debug3("Copy environment: %s=%s", var_name, var_val);
child_set_env(env, envsize, var_name, var_val);
xfree(var_name);
}
}
#ifdef HAVE_DEFOPEN
static
void
deflt_do_setup_env(Session *s, const char *shell, char ***env, u_int *envsize)
{
int flags;
char *ptr;
mode_t Umask = 022;
if (defopen(_PATH_DEFAULT_LOGIN))
return;
/* Ignore case */
flags = defcntl(DC_GETFLAGS, 0);
TURNOFF(flags, DC_CASE);
(void) defcntl(DC_SETFLAGS, flags);
/* TZ & HZ */
if ((ptr = defread("TIMEZONE=")) != NULL)
child_set_env(env, envsize, "TZ", ptr);
if ((ptr = defread("HZ=")) != NULL)
child_set_env(env, envsize, "HZ", ptr);
/* PATH */
if (s->pw->pw_uid != 0 && (ptr = defread("PATH=")) != NULL)
child_set_env(env, envsize, "PATH", ptr);
if (s->pw->pw_uid == 0 && (ptr = defread("SUPATH=")) != NULL)
child_set_env(env, envsize, "PATH", ptr);
/* SHELL */
if ((ptr = defread("ALTSHELL=")) != NULL) {
if (strcasecmp("YES", ptr) == 0)
child_set_env(env, envsize, "SHELL", shell);
else
child_set_env(env, envsize, "SHELL", "");
}
/* UMASK */
if ((ptr = defread("UMASK=")) != NULL &&
sscanf(ptr, "%lo", &Umask) == 1 &&
Umask <= (mode_t)0777)
(void) umask(Umask);
else
(void) umask(022);
/* ULIMIT */
if ((ptr = defread("ULIMIT=")) != NULL && atol(ptr) > 0L &&
ulimit(UL_SETFSIZE, atol(ptr)) < 0L)
error("Could not set ULIMIT to %ld from %s\n", atol(ptr),
_PATH_DEFAULT_LOGIN);
(void) defopen(NULL);
}
#endif /* HAVE_DEFOPEN */
static char **
do_setup_env(Session *s, const char *shell)
{
char buf[256];
char path_maildir[] = _PATH_MAILDIR;
u_int i, envsize, pm_len;
char **env;
struct passwd *pw = s->pw;
/* Initialize the environment. */
envsize = 100;
env = xmalloc(envsize * sizeof(char *));
env[0] = NULL;
#ifdef HAVE_CYGWIN
/*
* The Windows environment contains some setting which are
* important for a running system. They must not be dropped.
*/
copy_environment(environ, &env, &envsize);
#endif
#ifdef GSSAPI
/* Allow any GSSAPI methods that we've used to alter
* the childs environment as they see fit
*/
ssh_gssapi_do_child(xxx_gssctxt, &env,&envsize);
#endif
/* Set basic environment. */
child_set_env(&env, &envsize, "USER", pw->pw_name);
child_set_env(&env, &envsize, "LOGNAME", pw->pw_name);
child_set_env(&env, &envsize, "HOME", pw->pw_dir);
#ifdef HAVE_LOGIN_CAP
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"));
#else /* HAVE_LOGIN_CAP */
# ifndef HAVE_CYGWIN
/*
* There's no standard path on Windows. The path contains
* important components pointing to the system directories,
* needed for loading shared libraries. So the path better
* remains intact here.
*/
# ifdef SUPERUSER_PATH
child_set_env(&env, &envsize, "PATH",
s->pw->pw_uid == 0 ? SUPERUSER_PATH : _PATH_STDPATH);
# else
child_set_env(&env, &envsize, "PATH", _PATH_STDPATH);
# endif /* SUPERUSER_PATH */
# endif /* HAVE_CYGWIN */
#endif /* HAVE_LOGIN_CAP */
pm_len = strlen(path_maildir);
if (path_maildir[pm_len - 1] == '/' && pm_len > 1)
path_maildir[pm_len - 1] = NULL;
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);
#ifdef HAVE_DEFOPEN
deflt_do_setup_env(s, shell, &env, &envsize);
#endif /* HAVE_DEFOPEN */
#define PASS_ENV(x) \
if (getenv(x)) \
child_set_env(&env, &envsize, x, getenv(x));
if (getenv("TZ"))
child_set_env(&env, &envsize, "TZ", getenv("TZ"));
if (s->auth_file != NULL)
child_set_env(&env, &envsize, "XAUTHORITY", s->auth_file);
PASS_ENV("LANG")
PASS_ENV("LC_ALL")
PASS_ENV("LC_CTYPE")
PASS_ENV("LC_COLLATE")
PASS_ENV("LC_TIME")
PASS_ENV("LC_NUMERIC")
PASS_ENV("LC_MONETARY")
PASS_ENV("LC_MESSAGES")
#undef PASS_ENV
if (s->env != NULL)
copy_environment(s->env, &env, &envsize);
/* Set custom environment options from RSA authentication. */
while (custom_environment) {
struct envstring *ce = custom_environment;
char *str = ce->s;
for (i = 0; str[i] != '=' && str[i]; i++)
;
if (str[i] == '=') {
str[i] = 0;
child_set_env(&env, &envsize, str, str + i + 1);
}
custom_environment = ce->next;
xfree(ce->s);
xfree(ce);
}
/* SSH_CLIENT deprecated */
snprintf(buf, sizeof buf, "%.50s %d %d",
get_remote_ipaddr(), get_remote_port(), get_local_port());
child_set_env(&env, &envsize, "SSH_CLIENT", buf);
snprintf(buf, sizeof buf, "%.50s %d %.50s %d",
get_remote_ipaddr(), get_remote_port(),
get_local_ipaddr(packet_get_connection_in()), get_local_port());
child_set_env(&env, &envsize, "SSH_CONNECTION", buf);
if (s->ttyfd != -1)
child_set_env(&env, &envsize, "SSH_TTY", s->tty);
if (s->term)
child_set_env(&env, &envsize, "TERM", s->term);
if (s->display)
child_set_env(&env, &envsize, "DISPLAY", s->display);
if (original_command)
child_set_env(&env, &envsize, "SSH_ORIGINAL_COMMAND",
original_command);
#ifdef _UNICOS
if (cray_tmpdir[0] != '\0')
child_set_env(&env, &envsize, "TMPDIR", cray_tmpdir);
#endif /* _UNICOS */
#ifdef _AIX
{
char *cp;
if ((cp = getenv("AUTHSTATE")) != NULL)
child_set_env(&env, &envsize, "AUTHSTATE", cp);
if ((cp = getenv("KRB5CCNAME")) != NULL)
child_set_env(&env, &envsize, "KRB5CCNAME", cp);
read_environment_file(&env, &envsize, "/etc/environment");
}
#endif
#ifdef KRB4
if (s->authctxt->krb4_ticket_file)
child_set_env(&env, &envsize, "KRBTKFILE",
s->authctxt->krb4_ticket_file);
#endif
#ifdef KRB5
if (s->authctxt->krb5_ticket_file)
child_set_env(&env, &envsize, "KRB5CCNAME",
s->authctxt->krb5_ticket_file);
#endif
#ifdef USE_PAM
/*
* Pull in any environment variables that may have
* been set by PAM.
*/
{
char **p;
p = fetch_pam_environment(s->authctxt);
copy_environment(p, &env, &envsize);
free_pam_environment(p);
}
#endif /* USE_PAM */
if (auth_sock_name != NULL)
child_set_env(&env, &envsize, SSH_AUTHSOCKET_ENV_NAME,
auth_sock_name);
/* read $HOME/.ssh/environment. */
if (options.permit_user_env) {
snprintf(buf, sizeof buf, "%.200s/.ssh/environment",
strcmp(pw->pw_dir, "/") ? pw->pw_dir : "");
read_environment_file(&env, &envsize, buf);
}
if (debug_flag) {
/* dump the environment */
fprintf(stderr, gettext("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(Session *s, const char *shell)
{
FILE *f = NULL;
char cmd[1024];
int do_xauth;
struct stat st;
do_xauth =
s->display != NULL && s->auth_proto != NULL && s->auth_data != NULL;
/* ignore _PATH_SSH_USER_RC for subsystems */
if (!s->is_subsystem && (stat(_PATH_SSH_USER_RC, &st) >= 0)) {
snprintf(cmd, sizeof cmd, "%s -c '%s %s'",
shell, _PATH_BSHELL, _PATH_SSH_USER_RC);
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",
_PATH_SSH_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 add "
"%.100s %.100s %.100s\n",
options.xauth_location, s->auth_display,
s->auth_proto, s->auth_data);
}
snprintf(cmd, sizeof cmd, "%s -q -",
options.xauth_location);
f = popen(cmd, "w");
if (f) {
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);
}
}
}
/* Disallow logins if /etc/nologin exists. This does not apply to root. */
static void
do_nologin(struct passwd *pw)
{
FILE *f = NULL;
char buf[1024];
struct stat sb;
if (pw->pw_uid == 0)
return;
if (stat(_PATH_NOLOGIN, &sb) == -1)
return;
/* /etc/nologin exists. Print its contents if we can and exit. */
log("User %.100s not allowed because %s exists.", pw->pw_name,
_PATH_NOLOGIN);
if ((f = fopen(_PATH_NOLOGIN, "r")) != NULL) {
while (fgets(buf, sizeof(buf), f))
fputs(buf, stderr);
fclose(f);
}
exit(254);
}
/* Chroot into ChrootDirectory if the option is set. */
void
chroot_if_needed(struct passwd *pw)
{
char *chroot_path, *tmp;
if (chroot_requested(options.chroot_directory)) {
tmp = tilde_expand_filename(options.chroot_directory,
pw->pw_uid);
chroot_path = percent_expand(tmp, "h", pw->pw_dir,
"u", pw->pw_name, (char *)NULL);
safely_chroot(chroot_path, pw->pw_uid);
free(tmp);
free(chroot_path);
}
}
/*
* 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[MAXPATHLEN];
struct stat st;
if (*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("%s: checking '%s'", __func__, component);
if (stat(component, &st) != 0)
fatal("%s: stat(\"%s\"): %s", __func__,
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("%s: chdir(/) after chroot: %s",
__func__, strerror(errno));
verbose("Changed root directory to \"%s\"", path);
}
static void
launch_login(struct passwd *pw, const char *hostname)
{
/* Launch login(1). */
execl(LOGIN_PROGRAM, "login", "-h", hostname,
#ifdef xxxLOGIN_NEEDS_TERM
(s->term ? s->term : "unknown"),
#endif /* LOGIN_NEEDS_TERM */
#ifdef LOGIN_NO_ENDOPT
"-p", "-f", pw->pw_name, (char *)NULL);
#else
"-p", "-f", "--", pw->pw_name, (char *)NULL);
#endif
/* Login couldn't be executed, die. */
perror("login");
exit(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(Session *s, const char *command)
{
extern char **environ;
char **env;
char *argv[ARGV_MAX];
const char *shell, *shell0;
struct passwd *pw = s->pw;
/* remove hostkey from the child's memory */
destroy_sensitive_data();
do_nologin(pw);
chroot_if_needed(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;
#ifdef HAVE_LOGIN_CAP
shell = login_getcapstr(lc, "shell", (char *)shell, (char *)shell);
#endif
env = do_setup_env(s, 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
* get_remote_ipaddr there.
*/
if (packet_get_connection_in() == packet_get_connection_out())
close(packet_get_connection_in());
else {
close(packet_get_connection_in());
close(packet_get_connection_out());
}
/*
* Close all descriptors related to channels. They will still remain
* open in the parent.
*/
/* XXX better use close-on-exec? -markus */
channel_close_all();
/*
* Close any extra file descriptors. Note that there may still be
* descriptors left by system functions. They will be closed later.
*/
endpwent();
/*
* Must switch to the new environment variables so that .ssh/rc,
* /etc/ssh/sshrc, and xauth are run in the proper environment.
*/
environ = env;
/*
* New environment has been installed. We need to update locale
* so that error messages beyond this point have the proper
* character encoding.
*/
(void) setlocale(LC_ALL, "");
/*
* 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);
#ifdef AFS
/* Try to get AFS tokens for the local cell. */
if (k_hasafs()) {
char cell[64];
if (k_afs_cell_of_file(pw->pw_dir, cell, sizeof(cell)) == 0)
krb_afslog(cell, 0);
krb_afslog(0, 0);
}
#endif /* AFS */
/* Change current directory to the user's home directory. */
if (chdir(pw->pw_dir) < 0) {
/* Suppress missing homedir warning for chroot case */
if (!chroot_requested(options.chroot_directory))
fprintf(stderr, "Could not chdir to home "
"directory %s: %s\n", pw->pw_dir,
strerror(errno));
}
do_rc_files(s, shell);
/* restore SIGPIPE for child */
signal(SIGPIPE, SIG_DFL);
if (s->is_subsystem == SUBSYSTEM_INT_SFTP) {
int i;
char *p, *args;
extern int optind, optreset;
/* This will set the E/P sets here, simulating exec(2). */
drop_privs(pw->pw_uid);
setproctitle("%s@internal-sftp-server", s->pw->pw_name);
args = xstrdup(command ? command : "sftp-server");
i = 0;
for ((p = strtok(args, " ")); p != NULL; (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));
}
/* 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);
}
Session *
session_new(void)
{
int i;
static int did_init = 0;
if (!did_init) {
debug("session_new: init");
for (i = 0; i < MAX_SESSIONS; i++) {
sessions[i].used = 0;
}
did_init = 1;
}
for (i = 0; i < MAX_SESSIONS; i++) {
Session *s = &sessions[i];
if (! s->used) {
memset(s, 0, sizeof(*s));
s->chanid = -1;
s->ptyfd = -1;
s->ttyfd = -1;
s->used = 1;
s->self = i;
s->env = NULL;
debug("session_new: session %d", i);
return s;
}
}
return NULL;
}
static void
session_dump(void)
{
int i;
for (i = 0; i < MAX_SESSIONS; i++) {
Session *s = &sessions[i];
debug("dump: used %d session %d %p channel %d pid %ld",
s->used,
s->self,
s,
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)
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;
}
#ifndef lint
Session *
session_by_tty(char *tty)
{
int i;
for (i = 0; i < MAX_SESSIONS; 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;
}
#endif /* lint */
static Session *
session_by_channel(int id)
{
int i;
for (i = 0; i < MAX_SESSIONS; 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_pid(pid_t pid)
{
int i;
debug("session_by_pid: pid %ld", (long)pid);
for (i = 0; i < MAX_SESSIONS; 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(Session *s)
{
s->col = packet_get_int();
s->row = packet_get_int();
s->xpixel = packet_get_int();
s->ypixel = packet_get_int();
packet_check_eom();
pty_change_window_size(s->ptyfd, s->row, s->col, s->xpixel, s->ypixel);
return 1;
}
static int
session_pty_req(Session *s)
{
u_int len;
int n_bytes;
if (no_pty_flag) {
debug("Allocating a pty not permitted for this authentication.");
return 0;
}
if (s->ttyfd != -1) {
packet_disconnect("Protocol error: you already have a pty.");
return 0;
}
/* Get the time and hostname when the user last logged in. */
if (options.print_lastlog) {
s->hostname[0] = '\0';
s->last_login_time = get_last_login_time(s->pw->pw_uid,
s->pw->pw_name, s->hostname, sizeof(s->hostname));
/*
* PAM may update the last login date.
*
* Ideally PAM would also show the last login date as a
* PAM_TEXT_INFO conversation message, and then we could just
* always force the use of keyboard-interactive just so we can
* pass any such PAM prompts and messages from the account and
* session stacks, but skip pam_authenticate() if other userauth
* has succeeded and the user's password isn't expired.
*
* Unfortunately this depends on support for keyboard-
* interactive in the client, and support for lastlog messages
* in some PAM module.
*
* As it is Solaris updates the lastlog in PAM, but does
* not show the lastlog date in PAM. If and when this state of
* affairs changes this hack can be reconsidered, and, maybe,
* removed.
*
* So we're stuck with a crude hack: get the lastlog
* time before calling pam_open_session() and store it
* in the Authctxt and then use it here once. After
* that, if the client opens any more pty sessions we'll
* show the last lastlog entry since userauth.
*/
if (s->authctxt != NULL && s->authctxt->last_login_time > 0) {
s->last_login_time = s->authctxt->last_login_time;
(void) strlcpy(s->hostname,
s->authctxt->last_login_host,
sizeof(s->hostname));
s->authctxt->last_login_time = 0;
s->authctxt->last_login_host[0] = '\0';
}
}
s->term = packet_get_string(&len);
if (compat20) {
s->col = packet_get_int();
s->row = packet_get_int();
} else {
s->row = packet_get_int();
s->col = packet_get_int();
}
s->xpixel = packet_get_int();
s->ypixel = packet_get_int();
if (strcmp(s->term, "") == 0) {
xfree(s->term);
s->term = NULL;
}
/* Allocate a pty and open it. */
debug("Allocating pty.");
if (!pty_allocate(&s->ptyfd, &s->ttyfd, s->tty, sizeof(s->tty))) {
if (s->term)
xfree(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);
/* for SSH1 the tty modes length is not given */
if (!compat20)
n_bytes = packet_remaining();
tty_parse_modes(s->ttyfd, &n_bytes);
/*
* Add a cleanup function to clear the utmp entry and record logout
* time in case we call fatal() (e.g., the connection gets closed).
*/
fatal_add_cleanup(session_pty_cleanup, (void *)s);
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);
packet_check_eom();
session_proctitle(s);
return 1;
}
static int
session_subsystem_req(Session *s)
{
struct stat st;
u_int len;
int success = 0;
char *prog, *cmd, *subsys = packet_get_string(&len);
u_int i;
packet_check_eom();
log("subsystem request for %.100s", subsys);
for (i = 0; i < options.num_subsystems; i++) {
if (strcmp(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;
/*
* We must stat(2) the subsystem before we chroot in
* order to be able to send a proper error message.
*/
} else if (chroot_requested(options.chroot_directory)) {
char chdirsub[MAXPATHLEN];
strlcpy(chdirsub, options.chroot_directory,
sizeof (chdirsub));
strlcat(chdirsub, "/", sizeof (chdirsub));
strlcat(chdirsub, prog, sizeof (chdirsub));
if (stat(chdirsub, &st) < 0) {
error("subsystem: cannot stat %s under "
"chroot directory %s: %s", prog,
options.chroot_directory,
strerror(errno));
if (strcmp(subsys, "sftp") == 0)
error("subsystem: please see "
"the Subsystem option in "
"sshd_config(4) for an "
"explanation of '%s'.",
INTERNAL_SFTP_NAME);
break;
}
} else if (stat(prog, &st) < 0) {
error("subsystem: cannot stat %s: %s", prog,
strerror(errno));
break;
} else {
s->is_subsystem = SUBSYSTEM_EXT;
}
debug("subsystem: exec() %s", cmd);
do_exec(s, cmd);
success = 1;
break;
}
}
if (!success)
log("subsystem request for %.100s failed, subsystem not found",
subsys);
xfree(subsys);
return success;
}
/*
* Serve "x11-req" channel request for X11 forwarding for the current session
* channel.
*/
static int
session_x11_req(Session *s)
{
int success, fd;
char xauthdir[] = "/tmp/ssh-xauth-XXXXXX";
s->single_connection = packet_get_char();
s->auth_proto = packet_get_string(NULL);
s->auth_data = packet_get_string(NULL);
s->screen = packet_get_int();
packet_check_eom();
success = session_setup_x11fwd(s);
if (!success) {
xfree(s->auth_proto);
xfree(s->auth_data);
s->auth_proto = NULL;
s->auth_data = NULL;
return (success);
}
/*
* Create per session X authority file so that different sessions
* don't contend for one common file. The reason for this is that
* xauth(1) locking doesn't work too well over network filesystems.
*
* If mkdtemp() or open() fails then s->auth_file remains NULL which
* means that we won't set XAUTHORITY variable in child's environment
* and xauth(1) will use the default location for the authority file.
*/
if (mkdtemp(xauthdir) != NULL) {
s->auth_file = xmalloc(MAXPATHLEN);
snprintf(s->auth_file, MAXPATHLEN, "%s/xauthfile",
xauthdir);
/*
* we don't want that "creating new authority file" message to
* be printed by xauth(1) so we must create that file
* beforehand.
*/
if ((fd = open(s->auth_file, O_CREAT | O_EXCL | O_RDONLY,
S_IRUSR | S_IWUSR)) == -1) {
error("failed to create the temporary X authority "
"file %s: %.100s; will use the default one",
s->auth_file, strerror(errno));
xfree(s->auth_file);
s->auth_file = NULL;
if (rmdir(xauthdir) == -1) {
error("cannot remove xauth directory %s: %.100s",
xauthdir, strerror(errno));
}
} else {
close(fd);
debug("temporary X authority file %s created",
s->auth_file);
/*
* add a cleanup function to remove the temporary
* xauth file in case we call fatal() (e.g., the
* connection gets closed).
*/
fatal_add_cleanup(session_xauthfile_cleanup, (void *)s);
}
}
else {
error("failed to create a directory for the temporary X "
"authority file: %.100s; will use the default xauth file",
strerror(errno));
}
return (success);
}
static int
session_shell_req(Session *s)
{
packet_check_eom();
do_exec(s, NULL);
return 1;
}
static int
session_exec_req(Session *s)
{
u_int len;
char *command = packet_get_string(&len);
packet_check_eom();
do_exec(s, command);
xfree(command);
return 1;
}
static int
session_auth_agent_req(Session *s)
{
static int called = 0;
packet_check_eom();
if (no_agent_forwarding_flag) {
debug("session_auth_agent_req: no_agent_forwarding_flag");
return 0;
}
if (called) {
return 0;
} else {
called = 1;
return auth_input_request_forwarding(s->pw);
}
}
static int
session_loc_env_check(char *var, char *val)
{
char *current;
int cat, ret;
if (strcmp(var, "LANG") == 0)
cat = LC_ALL;
else if (strcmp(var, "LC_ALL") == 0)
cat = LC_ALL;
else if (strcmp(var, "LC_CTYPE") == 0)
cat = LC_CTYPE;
else if (strcmp(var, "LC_COLLATE") == 0)
cat = LC_COLLATE;
else if (strcmp(var, "LC_TIME") == 0)
cat = LC_TIME;
else if (strcmp(var, "LC_NUMERIC") == 0)
cat = LC_NUMERIC;
else if (strcmp(var, "LC_MONETARY") == 0)
cat = LC_MONETARY;
else if (strcmp(var, "LC_MESSAGES") == 0)
cat = LC_MESSAGES;
current = setlocale(cat, NULL);
ret = (setlocale(cat, val) != NULL);
(void) setlocale(cat, current);
return (ret);
}
static int
session_env_req(Session *s)
{
Channel *c;
char *var, *val, *e;
char **p;
size_t len;
int ret = 0;
/* Get var/val from the rest of this packet */
var = packet_get_string(NULL);
val = packet_get_string(NULL);
/*
* We'll need the channel ID for the packet_send_debug messages,
* so get it now.
*/
if ((c = channel_lookup(s->chanid)) == NULL)
goto done; /* shouldn't happen! */
debug2("Received request for environment variable %s=%s", var, val);
/* For now allow only LANG and LC_* */
if (strcmp(var, "LANG") != 0 && strncmp(var, "LC_", 3) != 0) {
debug2("Rejecting request for environment variable %s", var);
goto done;
}
if (!session_loc_env_check(var, val)) {
packet_send_debug(gettext("Missing locale support for %s=%s"),
var, val);
goto done;
}
packet_send_debug(gettext("Channel %d set: %s=%s"), c->remote_id,
var, val);
/*
* Always append new environment variables without regard to old
* ones being overriden. The way these are actually added to
* the environment of the session process later settings
* override earlier ones; see copy_environment().
*/
if (s->env == NULL) {
char **env;
env = xmalloc(sizeof (char **) * 2);
memset(env, 0, sizeof (char **) * 2);
s->env = env;
p = env;
} else {
for (p = s->env; *p != NULL ; p++);
s->env = xrealloc(s->env, (p - s->env + 2) * sizeof (char **));
for (p = s->env; *p != NULL ; p++);
}
len = snprintf(NULL, 0, "%s=%s", var, val);
e = xmalloc(len + 1);
(void) snprintf(e, len + 1, "%s=%s", var, val);
(*p++) = e;
*p = NULL;
ret = 1;
done:
xfree(var);
xfree(val);
return (ret);
}
static void
session_free_env(char ***envp)
{
char **env, **p;
if (envp == NULL || *envp == NULL)
return;
env = *envp;
*envp = NULL;
for (p = env; *p != NULL; p++)
xfree(*p);
xfree(env);
}
int
session_input_channel_req(Channel *c, const char *rtype)
{
int success = 0;
Session *s;
if ((s = session_by_channel(c->self)) == NULL) {
log("session_input_channel_req: no session %d req %.100s",
c->self, rtype);
return 0;
}
debug("session_input_channel_req: 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(s);
} else if (strcmp(rtype, "exec") == 0) {
success = session_exec_req(s);
} else if (strcmp(rtype, "pty-req") == 0) {
success = session_pty_req(s);
} else if (strcmp(rtype, "x11-req") == 0) {
success = session_x11_req(s);
} else if (strcmp(rtype, "auth-agent-req@openssh.com") == 0) {
success = session_auth_agent_req(s);
} else if (strcmp(rtype, "subsystem") == 0) {
success = session_subsystem_req(s);
} else if (strcmp(rtype, "env") == 0) {
success = session_env_req(s);
}
}
if (strcmp(rtype, "window-change") == 0) {
success = session_window_change_req(s);
}
return success;
}
void
session_set_fds(Session *s, int fdin, int fdout, int fderr)
{
if (!compat20)
fatal("session_set_fds: called for proto != 2.0");
/*
* 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(s->chanid,
fdout, fdin, fderr,
fderr == -1 ? CHAN_EXTENDED_IGNORE : CHAN_EXTENDED_READ,
1,
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(void *session)
{
Session *s = session;
if (s == NULL) {
error("session_pty_cleanup: no session");
return;
}
if (s->ttyfd == -1)
return;
debug("session_pty_cleanup: session %d release %s", s->self, s->tty);
#ifdef USE_PAM
session_do_pam(s, 0);
#endif /* USE_PAM */
/* Record that the user has logged out. */
if (s->pid != 0) {
debug3("Recording SSHv2 channel logout in utmpx/wtmpx");
#ifdef ALTPRIVSEP
altprivsep_record_logout(s->pid);
#endif /* ALTPRIVSEP */
}
/* 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 (close(s->ptymaster) < 0)
error("close(s->ptymaster/%d): %s", s->ptymaster, strerror(errno));
/* unlink pty from session */
s->ttyfd = -1;
}
void
session_pty_cleanup(void *session)
{
session_pty_cleanup2(session);
}
/*
* We use a different temporary X authority file per every session so we
* should remove those files when fatal() is called.
*/
void
session_xauthfile_cleanup(void *session)
{
Session *s = session;
if (s == NULL) {
error("session_xauthfile_cleanup: no session");
return;
}
debug("session_xauthfile_cleanup: session %d removing %s", s->self,
s->auth_file);
if (unlink(s->auth_file) == -1) {
error("session_xauthfile_cleanup: cannot remove xauth file: "
"%.100s", strerror(errno));
return;
}
/* dirname() will modify s->auth_file but that's ok */
if (rmdir(dirname(s->auth_file)) == -1) {
error("session_xauthfile_cleanup: "
"cannot remove xauth directory: %.100s", strerror(errno));
return;
}
}
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_exit_message(Session *s, int status)
{
Channel *c;
if ((c = channel_lookup(s->chanid)) == NULL)
fatal("session_exit_message: session %d: no channel %d",
s->self, s->chanid);
debug("session_exit_message: session %d channel %d pid %ld",
s->self, s->chanid, (long)s->pid);
if (WIFEXITED(status)) {
channel_request_start(s->chanid, "exit-status", 0);
packet_put_int(WEXITSTATUS(status));
packet_send();
} else if (WIFSIGNALED(status)) {
channel_request_start(s->chanid, "exit-signal", 0);
packet_put_cstring(sig2name(WTERMSIG(status)));
#ifdef WCOREDUMP
packet_put_char(WCOREDUMP(status));
#else /* WCOREDUMP */
packet_put_char(0);
#endif /* WCOREDUMP */
packet_put_cstring("");
packet_put_cstring("");
packet_send();
} else {
/* Some weird exit cause. Just exit. */
packet_disconnect("wait returned status %04x.", status);
}
/* Ok to close channel now */
channel_set_wait_for_exit(s->chanid, 0);
/* disconnect channel */
debug("session_exit_message: release channel %d", s->chanid);
channel_cancel_cleanup(s->chanid);
/*
* 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(c);
s->chanid = -1;
}
void
session_close(Session *s)
{
debug("session_close: session %d pid %ld", s->self, (long)s->pid);
if (s->ttyfd != -1) {
fatal_remove_cleanup(session_pty_cleanup, (void *)s);
session_pty_cleanup(s);
}
if (s->auth_file != NULL) {
fatal_remove_cleanup(session_xauthfile_cleanup, (void *)s);
session_xauthfile_cleanup(s);
xfree(s->auth_file);
}
if (s->term)
xfree(s->term);
if (s->display)
xfree(s->display);
if (s->auth_display)
xfree(s->auth_display);
if (s->auth_data)
xfree(s->auth_data);
if (s->auth_proto)
xfree(s->auth_proto);
if (s->command)
xfree(s->command);
session_free_env(&s->env);
s->used = 0;
session_proctitle(s);
}
void
session_close_by_pid(pid_t pid, int status)
{
Session *s = session_by_pid(pid);
if (s == NULL) {
debug("session_close_by_pid: no session for pid %ld",
(long)pid);
return;
}
if (s->chanid != -1)
session_exit_message(s, status);
session_close(s);
}
/*
* This is called when a channel dies before the session 'child' itself dies.
* It can happen for example if we exit from an interactive shell before we
* exit from forwarded X11 applications.
*/
void
session_close_by_channel(int id, void *arg)
{
Session *s = session_by_channel(id);
if (s == NULL) {
debug("session_close_by_channel: no session for id %d", id);
return;
}
debug("session_close_by_channel: channel %d child %ld",
id, (long)s->pid);
if (s->pid != 0) {
debug("session_close_by_channel: channel %d: has child", id);
/*
* delay detach of session, but release pty, since
* the fd's to the child are already closed
*/
if (s->ttyfd != -1) {
fatal_remove_cleanup(session_pty_cleanup, (void *)s);
session_pty_cleanup(s);
}
return;
}
/* detach by removing callback */
channel_cancel_cleanup(s->chanid);
s->chanid = -1;
session_close(s);
}
void
session_destroy_all(void (*closefunc)(Session *))
{
int i;
for (i = 0; i < MAX_SESSIONS; i++) {
Session *s = &sessions[i];
if (s->used) {
if (closefunc != NULL)
closefunc(s);
else
session_close(s);
}
}
}
static char *
session_tty_list(void)
{
static char buf[1024];
int i;
buf[0] = '\0';
for (i = 0; i < MAX_SESSIONS; 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(Session *s)
{
struct stat st;
char display[512], auth_display[512];
char hostname[MAXHOSTNAMELEN];
if (no_x11_forwarding_flag) {
packet_send_debug("X11 forwarding disabled in user configuration file.");
return 0;
}
if (!options.x11_forwarding) {
debug("X11 forwarding disabled in server configuration file.");
return 0;
}
if (!options.xauth_location ||
(stat(options.xauth_location, &st) == -1)) {
packet_send_debug("No xauth program; cannot forward with spoofing.");
return 0;
}
if (s->display != NULL) {
debug("X11 display already set.");
return 0;
}
if (x11_create_display_inet(options.x11_display_offset,
options.x11_use_localhost, s->single_connection,
&s->display_number) == -1) {
debug("x11_create_display_inet failed.");
return 0;
}
/* Set up a suitable value for the DISPLAY variable. */
if (gethostname(hostname, sizeof(hostname)) < 0)
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 {
#ifdef IPADDR_IN_DISPLAY
struct hostent *he;
struct in_addr my_addr;
he = gethostbyname(hostname);
if (he == NULL) {
error("Can't get IP address for X11 DISPLAY.");
packet_send_debug("Can't get IP address for X11 DISPLAY.");
return 0;
}
memcpy(&my_addr, he->h_addr_list[0], sizeof(struct in_addr));
snprintf(display, sizeof display, "%.50s:%u.%u", inet_ntoa(my_addr),
s->display_number, s->screen);
#else
snprintf(display, sizeof display, "%.400s:%u.%u", hostname,
s->display_number, s->screen);
#endif
s->display = xstrdup(display);
s->auth_display = xstrdup(display);
}
return 1;
}
#ifdef USE_PAM
int session_do_pam_conv(int, struct pam_message **,
struct pam_response **, void *);
static struct pam_conv session_pam_conv = {
session_do_pam_conv,
NULL
};
static void
session_do_pam(Session *s, int do_open)
{
int pam_retval;
char *where, *old_tty, *old_tty_copy = NULL;
struct pam_conv old_conv, *old_conv_ptr;
if (!s || !s->authctxt || !s->authctxt->pam || !s->authctxt->pam->h)
return;
/* Save current PAM item values */
where = "getting PAM_CONV";
pam_retval = pam_get_item(s->authctxt->pam->h, PAM_CONV,
(void **) &old_conv_ptr);
if (pam_retval != PAM_SUCCESS)
goto done;
old_conv = *old_conv_ptr;
where = "getting PAM_TTY";
pam_retval = pam_get_item(s->authctxt->pam->h, PAM_TTY,
(void **) &old_tty);
if (pam_retval != PAM_SUCCESS)
goto done;
old_tty_copy = xstrdup(old_tty);
/* Change PAM_TTY and PAM_CONV items */
where = "setting PAM_TTY";
pam_retval = pam_set_item(s->authctxt->pam->h, PAM_TTY, s->tty);
if (pam_retval != PAM_SUCCESS)
goto done;
where = "setting PAM_CONV";
session_pam_conv.appdata_ptr = s;
pam_retval = pam_set_item(s->authctxt->pam->h,
PAM_CONV, &session_pam_conv);
if (pam_retval != PAM_SUCCESS)
goto done;
/* Call pam_open/close_session() */
if (do_open) {
where = "calling pam_open_session()";
pam_retval = pam_open_session(s->authctxt->pam->h, 0);
}
else {
where = "calling pam_close_session()";
pam_retval = pam_close_session(s->authctxt->pam->h, 0);
}
/* Reset PAM_TTY and PAM_CONV items to previous values */
where = "setting PAM_TTY";
pam_retval = pam_set_item(s->authctxt->pam->h, PAM_TTY, old_tty_copy);
if (pam_retval != PAM_SUCCESS)
goto done;
where = "setting PAM_CONV";
pam_retval = pam_set_item(s->authctxt->pam->h, PAM_CONV, &old_conv);
if (pam_retval != PAM_SUCCESS)
goto done;
session_pam_conv.appdata_ptr = NULL;
done:
if (old_tty_copy)
xfree(old_tty_copy);
if (pam_retval == PAM_SUCCESS)
return;
/* fatal()? probably not... */
log("PAM failed[%d] while %s: %s", pam_retval, where,
PAM_STRERROR(s->authctxt->pam->h, pam_retval));
}
int
session_do_pam_conv(int num_prompts,
struct pam_message **prompts,
struct pam_response **resp,
void *app_data)
{
Session *s = (Session *) app_data;
struct pam_response *reply;
int count;
char *prompt;
if (channel_lookup(s->chanid) == NULL)
return PAM_CONV_ERR;
/* PAM will free this later */
reply = xmalloc(num_prompts * sizeof(*reply));
(void) memset(reply, 0, num_prompts * sizeof(*reply));
for (count = 0; count < num_prompts; count++) {
switch(PAM_MSG_MEMBER(prompts, count, msg_style)) {
case PAM_TEXT_INFO:
/* Write to stdout of channel */
prompt = PAM_MSG_MEMBER(prompts, count, msg);
if (prompt != NULL && s->ttyfd != -1) {
debug2("session_do_pam_conv: text info "
"prompt: %s", prompt);
(void) write(s->ttyfd, prompt, strlen(prompt));
(void) write(s->ttyfd, "\n", 1);
}
reply[count].resp = xstrdup("");
reply[count].resp_retcode = PAM_SUCCESS;
break;
case PAM_ERROR_MSG:
/* Write to stderr of channel */
prompt = PAM_MSG_MEMBER(prompts, count, msg);
if (prompt != NULL && s->ttyfd != -1) {
debug2("session_do_pam_conv: error "
"prompt: %s", prompt);
(void) write(s->ttyfd, prompt, strlen(prompt));
(void) write(s->ttyfd, "\n", 1);
}
reply[count].resp = xstrdup("");
reply[count].resp_retcode = PAM_SUCCESS;
break;
case PAM_PROMPT_ECHO_ON:
case PAM_PROMPT_ECHO_OFF:
/*
* XXX Someday add support for echo on/off prompts
* here on sessions with ttys.
*/
default:
xfree(reply);
return PAM_CONV_ERR;
}
}
*resp = reply;
return PAM_SUCCESS;
}
#endif /* USE_PAM */
static void
do_authenticated2(Authctxt *authctxt)
{
server_loop2(authctxt);
}
/*
* Drop the privileges. We need this for the in-process SFTP server only. For
* the shell and the external subsystem the exec(2) call will do the P = E = I
* assignment itself. Never change the privileges if the connecting user is
* root. See privileges(5) if the terminology used here is not known to you.
*/
static void
drop_privs(uid_t uid)
{
priv_set_t *priv_inherit;
/* If root is connecting we are done. */
if (uid == 0)
return;
if ((priv_inherit = priv_allocset()) == NULL)
fatal("priv_allocset: %s", strerror(errno));
if (getppriv(PRIV_INHERITABLE, priv_inherit) != 0)
fatal("getppriv: %s", strerror(errno));
/*
* This will limit E as well. Note that before this P was a
* superset of I, see permanently_set_uid().
*/
if (setppriv(PRIV_SET, PRIV_PERMITTED, priv_inherit) == -1)
fatal("setppriv: %s", strerror(errno));
priv_freeset(priv_inherit);
/*
* By manipulating the P set above we entered a PA mode which we
* do not need to retain in.
*/
if (setpflags(PRIV_AWARE, 0) == -1)
fatal("setpflags: %s", strerror(errno));
}