Remove rexecd(8), a server that implements a particularly insecure

method of executing commands remotely.  There are no rexec clients in
the FreeBSD tree, and the client function rexec(3) is present only in
libcompat.  It has been documented as "obsolete" since 4.3BSD, and its
use has been discouraged in the man page for over 10 years.
This commit is contained in:
Jacques Vidrine 2005-06-10 20:52:36 +00:00
parent 1b5a39d368
commit a8e0b2e8ab
Notes: svn2git 2020-12-20 02:59:44 +00:00
svn path=/head/; revision=147270
10 changed files with 1 additions and 536 deletions

View File

@ -18,7 +18,6 @@
#login stream tcp6 nowait root /usr/libexec/rlogind rlogind
#finger stream tcp nowait/3/10 nobody /usr/libexec/fingerd fingerd -s
#finger stream tcp6 nowait/3/10 nobody /usr/libexec/fingerd fingerd -s
#exec stream tcp nowait root /usr/libexec/rexecd rexecd
#
# run comsat as root to be able to print partial mailbox contents w/ biff,
# or use the safer tty:tty to just print that new mail has been received.

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@ -2,7 +2,7 @@
NO_OBJ=
FILES= README ftpd gdm imap kde login other passwd pop3 \
rexecd rsh sshd su system telnetd xdm
rsh sshd su system telnetd xdm
FILESDIR= /etc/pam.d
FILESMODE= 644
FILESMODE_README= 444

View File

@ -1,19 +0,0 @@
#
# $FreeBSD$
#
# PAM configuration for the "rexecd" service
#
# auth
auth required pam_nologin.so no_warn
auth required pam_unix.so no_warn use_first_pass
# account
account required pam_ftpusers.so no_warn disallow
account required pam_unix.so no_warn
# session
session required pam_permit.so
# password
password required pam_deny.so

View File

@ -264,8 +264,6 @@ is overloaded to mean ``All network ports in use.''
.Xr rlogin 1 ,
.Xr rsh 1 ,
.Xr intro 2 ,
.Xr rexec 3 ,
.Xr rexecd 8 ,
.Xr rlogind 8 ,
.Xr rshd 8
.Pp

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@ -16,7 +16,6 @@ SUBDIR= atrun \
pt_chown \
rbootd \
revnetgroup \
${_rexecd} \
${_rlogind} \
rpc.rquotad \
rpc.rstatd \
@ -47,7 +46,6 @@ _rtld-elf= rtld-elf
.endif
.if !defined(NO_RCMDS)
_rexecd= rexecd
_rlogind= rlogind
_rshd= rshd
.endif

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@ -1,12 +0,0 @@
# @(#)Makefile 8.1 (Berkeley) 6/4/93
# $FreeBSD$
PROG= rexecd
MAN= rexecd.8
WARNS?= 6
WFORMAT=0
DPADD= ${LIBPAM} ${LIBUTIL}
LDADD= ${MINUSLPAM} -lutil
.include <bsd.prog.mk>

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@ -1,169 +0,0 @@
.\" Copyright (c) 1983, 1991, 1993
.\" The Regents of the University of California. 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.
.\" 3. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
.\"
.\" @(#)rexecd.8 8.2 (Berkeley) 12/11/93
.\" $FreeBSD$
.\"
.Dd September 23, 1994
.Dt REXECD 8
.Os
.Sh NAME
.Nm rexecd
.Nd remote execution server
.Sh SYNOPSIS
.Nm
.Op Fl i
.Sh DESCRIPTION
The
.Nm
utility is the server for the
.Xr rexec 3
routine.
The server provides remote execution facilities
with authentication based on user names and
passwords.
.Pp
The
.Nm
utility listens for service requests at the port indicated in
the ``exec'' service specification; see
.Xr services 5 .
When a service request is received the following protocol
is initiated:
.Bl -enum
.It
The server reads characters from the socket up
to a NUL
.Pq Ql \e0
byte.
The resultant string is
interpreted as an
.Tn ASCII
number, base 10.
.It
If the number received in step 1 is non-zero,
it is interpreted as the port number of a secondary
stream to be used for the
.Em stderr .
A second connection is then created to the specified
port on the client's machine.
.It
A NUL terminated user name of at most 16 characters
is retrieved on the initial socket.
.It
A NUL terminated, unencrypted password of at most
16 characters is retrieved on the initial socket.
.It
A NUL terminated command to be passed to a
shell is retrieved on the initial socket.
The length of
the command is limited by the upper bound on the size of
the system's argument list.
.It
The
.Nm
utility then validates the user as is done at login time
and, if the authentication was successful, changes
to the user's home directory, and establishes the user
and group protections of the user.
If any of these steps fail the connection is
aborted with a diagnostic message returned.
.It
A NUL byte is returned on the initial socket
and the command line is passed to the normal login
shell of the user.
The
shell inherits the network connections established
by
.Nm .
.El
.Sh CAVEATS
The
.Nm
utility will not allow root logins unless the
.Fl i
option is given on the command line (typically in
.Pa /etc/inetd.conf ) .
It will also disallow access for users listed in
.Pa /etc/ftpusers ,
or users with no passwords, which were all serious security holes.
The entire concept of rexec/rexecd is a major security hole and an example
of how not to do things.
The
.Nm
utility is disabled by default in
.Pa /etc/inetd.conf .
.Sh DIAGNOSTICS
Except for the last one listed below,
all diagnostic messages are returned on the initial socket,
after which any network connections are closed.
An error is indicated by a leading byte with a value of
1 (0 is returned in step 7 above upon successful completion
of all the steps prior to the command execution).
.Pp
.Bl -tag -width Ds
.It Sy username too long
The name is
longer than 16 characters.
.It Sy password too long
The password is longer than 16 characters.
.It Sy command too long
The command line passed exceeds the size of the argument
list (as configured into the system).
.It Sy Login incorrect.
No password file entry for the user name existed.
.It Sy Password incorrect.
The wrong password was supplied.
.It Sy \&No remote directory.
The
.Xr chdir 1
command to the home directory failed.
.It Sy Try again.
A
.Xr fork 2
by the server failed.
.It Sy <shellname>: ...
The user's login shell could not be started.
This message is returned
on the connection associated with the
.Em stderr ,
and is not preceded by a flag byte.
.El
.Sh SEE ALSO
.Xr rexec 3
.Sh HISTORY
The
.Nm
utility appeared in
.Bx 4.2 .
.Sh BUGS
A facility to allow all data and password exchanges to be encrypted should be
present.

View File

@ -1,326 +0,0 @@
/*
* Copyright (c) 1983, 1993
* The Regents of the University of California. 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
*/
#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1983, 1993\n\
The Regents of the University of California. All rights reserved.\n";
#endif /* not lint */
#ifndef lint
#if 0
static char sccsid[] = "@(#)rexecd.c 8.1 (Berkeley) 6/4/93";
#endif
static const char rcsid[] =
"$FreeBSD$";
#endif /* not lint */
#include <sys/param.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <err.h>
#include <errno.h>
#include <libutil.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <security/pam_appl.h>
#include <security/openpam.h>
static pam_handle_t *pamh;
static struct pam_conv pamc = {
openpam_nullconv,
NULL
};
static int pam_flags = PAM_SILENT|PAM_DISALLOW_NULL_AUTHTOK;
static int pam_err;
#define pam_ok(err) ((pam_err = (err)) == PAM_SUCCESS)
char **environ;
char remote[MAXHOSTNAMELEN];
struct sockaddr_storage sa;
char default_shell[] = _PATH_BSHELL;
static void doit(struct sockaddr *);
static void getstr(char *, size_t, const char *);
static void error(const char *fmt, ...);
int no_uid_0 = 1;
/*
* remote execute server:
* username\0
* password\0
* command\0
* data
*/
/*ARGSUSED*/
int
main(int argc, char *argv[])
{
struct sockaddr_storage from;
socklen_t fromlen;
int ch;
openlog("rexecd", LOG_PID, LOG_AUTH);
while ((ch = getopt(argc, argv, "i")) != -1)
switch (ch) {
case 'i':
no_uid_0 = 0;
break;
default:
syslog(LOG_ERR, "usage: rexecd [-i]");
exit(1);
}
argc -= optind;
argv += optind;
fromlen = sizeof (from);
if (getpeername(0, (struct sockaddr *)&from, &fromlen) < 0)
err(1, "getpeername");
realhostname_sa(remote, sizeof(remote) - 1,
(struct sockaddr *)&from, fromlen);
doit((struct sockaddr *)&from);
return(0);
}
static void
doit(struct sockaddr *fromp)
{
char *cmdbuf, *cp;
size_t maxcmdlen;
char user[16], pass[16];
struct passwd *pwd;
const void *item;
int fd, r, sd;
u_short port;
int pv[2], pid, cc, nfds;
fd_set rfds, fds;
char buf[BUFSIZ], sig;
int one = 1;
maxcmdlen = sysconf(_SC_ARG_MAX);
if (maxcmdlen <= 0 || (cmdbuf = malloc(maxcmdlen)) == NULL)
exit(1);
(void) signal(SIGINT, SIG_DFL);
(void) signal(SIGQUIT, SIG_DFL);
(void) signal(SIGTERM, SIG_DFL);
dup2(STDIN_FILENO, STDOUT_FILENO);
dup2(STDIN_FILENO, STDOUT_FILENO);
(void) alarm(60);
port = 0;
sd = -1;
for (;;) {
char c;
if (read(STDIN_FILENO, &c, 1) != 1)
exit(1);
if (c == 0)
break;
port = port * 10 + c - '0';
}
if (port != 0) {
sd = socket(fromp->sa_family, SOCK_STREAM, 0);
if (sd < 0)
exit(1);
bzero(&sa, sizeof(sa));
sa.ss_family = fromp->sa_family;
sa.ss_len = fromp->sa_len;
if (bind(sd, (struct sockaddr *)&sa, sa.ss_len) < 0)
exit(1);
switch (fromp->sa_family) {
case AF_INET:
((struct sockaddr_in *)(void *)fromp)->sin_port = htons(port);
break;
case AF_INET6:
((struct sockaddr_in6 *)(void *)fromp)->sin6_port = htons(port);
break;
default:
exit(1);
}
if (connect(sd, fromp, fromp->sa_len) < 0)
exit(1);
}
getstr(user, sizeof(user), "username");
getstr(pass, sizeof(pass), "password");
getstr(cmdbuf, maxcmdlen, "command");
(void) alarm(0);
if (!pam_ok(pam_start("rexecd", user, &pamc, &pamh)) ||
!pam_ok(pam_set_item(pamh, PAM_RHOST, remote)) ||
!pam_ok(pam_set_item(pamh, PAM_AUTHTOK, pass)) ||
!pam_ok(pam_authenticate(pamh, pam_flags)) ||
!pam_ok(pam_acct_mgmt(pamh, pam_flags)) ||
!pam_ok(pam_get_item(pamh, PAM_USER, &item)) || item == NULL ||
strlen(item) >= sizeof(user) || strcpy(user, item) == NULL ||
(pwd = getpwnam(user)) == NULL ||
(pwd->pw_uid == 0 && no_uid_0)) {
syslog(LOG_ERR, "%s LOGIN REFUSED from %s", user, remote);
error("Login incorrect.\n");
exit(1);
}
syslog(LOG_INFO, "login from %s as %s", remote, user);
(void) write(STDERR_FILENO, "\0", 1);
if (port != 0) {
(void) pipe(pv);
pid = fork();
if (pid == -1) {
error("Try again.\n");
exit(1);
}
if (pid) {
/* parent */
(void) pam_end(pamh, pam_err);
(void) close(STDIN_FILENO);
(void) close(STDOUT_FILENO);
(void) close(STDERR_FILENO);
(void) close(pv[1]);
ioctl(pv[0], FIONBIO, (char *)&one);
/* should set sd nbio! */
FD_ZERO(&fds);
FD_SET(sd, &fds);
nfds = sd + 1;
FD_SET(pv[0], &fds);
if (pv[0] >= nfds)
nfds = pv[0] + 1;
do {
rfds = fds;
for (;;) {
r = select(nfds, &rfds, NULL, NULL, NULL);
if (r > 0)
break;
if (r < 0 && errno != EINTR)
exit(0);
}
if (FD_ISSET(sd, &rfds)) {
if (read(sd, &sig, 1) <= 0)
FD_CLR(sd, &fds);
else
killpg(pid, sig);
}
if (FD_ISSET(pv[0], &fds)) {
cc = read(pv[0], buf, sizeof (buf));
if (cc <= 0) {
shutdown(sd, SHUT_RDWR);
FD_CLR(pv[0], &fds);
} else {
(void) write(sd, buf, cc);
}
}
} while (FD_ISSET(sd, &fds) || FD_ISSET(pv[0], &fds));
exit(0);
}
/* child */
(void) close(sd);
(void) close(pv[0]);
dup2(pv[1], 2);
}
for (fd = getdtablesize(); fd > 2; fd--)
(void) close(fd);
if (*pwd->pw_shell == '\0')
pwd->pw_shell = default_shell;
if (setsid() == -1)
syslog(LOG_ERR, "setsid() failed: %m");
if (setlogin(pwd->pw_name) < 0)
syslog(LOG_ERR, "setlogin() failed: %m");
(void) setgid((gid_t)pwd->pw_gid);
initgroups(pwd->pw_name, pwd->pw_gid);
if (!pam_ok(pam_setcred(pamh, PAM_ESTABLISH_CRED)))
syslog(LOG_ERR, "pam_setcred() failed: %s",
pam_strerror(pamh, pam_err));
(void) pam_setenv(pamh, "HOME", pwd->pw_dir, 1);
(void) pam_setenv(pamh, "SHELL", pwd->pw_shell, 1);
(void) pam_setenv(pamh, "USER", pwd->pw_name, 1);
(void) pam_setenv(pamh, "PATH", _PATH_DEFPATH, 1);
environ = pam_getenvlist(pamh);
(void) pam_end(pamh, pam_err);
(void) setuid((uid_t)pwd->pw_uid);
cp = strrchr(pwd->pw_shell, '/');
if (cp)
cp++;
else
cp = pwd->pw_shell;
if (chdir(pwd->pw_dir) < 0) {
error("No remote directory.\n");
exit(1);
}
execl(pwd->pw_shell, cp, "-c", cmdbuf, (char *)0);
err(1, "%s", pwd->pw_shell);
}
static void
error(const char *fmt, ...)
{
char buf[BUFSIZ];
va_list ap;
va_start(ap, fmt);
buf[0] = 1;
(void)vsnprintf(buf + 1, sizeof(buf) - 1, fmt, ap);
(void)write(STDERR_FILENO, buf, strlen(buf));
va_end(ap);
}
static void
getstr(char *buf, size_t cnt, const char *field)
{
char c;
do {
if (read(STDIN_FILENO, &c, 1) != 1)
exit(1);
*buf++ = c;
if (--cnt == 0) {
error("%s too long\n", field);
exit(1);
}
} while (c != 0);
}

View File

@ -902,7 +902,6 @@ socket but was unable to.
.Xr comsat 8 ,
.Xr fingerd 8 ,
.Xr ftpd 8 ,
.Xr rexecd 8 ,
.Xr rlogind 8 ,
.Xr rpcbind 8 ,
.Xr rshd 8 ,

View File

@ -43,8 +43,6 @@ utility is used by the remote dump and restore programs
in manipulating a magnetic tape drive through an interprocess
communication connection.
It is normally started up with an
.Xr rexec 3
or
.Xr rcmd 3
call.
.Pp
@ -210,7 +208,6 @@ to exit.
All responses are of the form described above.
.Sh SEE ALSO
.Xr rcmd 3 ,
.Xr rexec 3 ,
.Xr mtio 4 ,
.Xr rdump 8 ,
.Xr rrestore 8