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tdebase/kcheckpass/kcheckpass.c

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/*****************************************************************
*
* kcheckpass - Simple password checker
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the Free
* Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*
* kcheckpass is a simple password checker. Just invoke and
* send it the password on stdin.
*
* If the password was accepted, the program exits with 0;
* if it was rejected, it exits with 1. Any other exit
* code signals an error.
*
* It's hopefully simple enough to allow it to be setuid
* root.
*
* Compile with -DHAVE_VSYSLOG if you have vsyslog().
* Compile with -DHAVE_PAM if you have a PAM system,
* and link with -lpam -ldl.
* Compile with -DHAVE_SHADOW if you have a shadow
* password system.
*
* Copyright (C) 1998, Caldera, Inc.
* Released under the GNU General Public License
*
* Olaf Kirch <okir@caldera.de> General Framework and PAM support
* Christian Esken <esken@kde.org> Shadow and /etc/passwd support
* Roberto Teixeira <maragato@kde.org> other user (-U) support
* Oswald Buddenhagen <ossi@kde.org> Binary server mode
*
* Other parts were taken from tdescreensaver's passwd.cpp.
*
*****************************************************************/
#include "kcheckpass.h"
#include <stdarg.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <syslog.h>
#include <stdlib.h>
#include <errno.h>
#include <time.h>
/* Compatibility: accept some options from environment variables */
#define ACCEPT_ENV
#define THROTTLE 3
static int havetty, sfd = -1, nullpass;
static char *
conv_legacy (ConvRequest what, const char *prompt)
{
char *p, *p2;
int len;
char buf[1024];
switch (what) {
case ConvGetBinary:
break;
case ConvGetNormal:
/* there is no prompt == 0 case */
if (!havetty)
break;
/* i guess we should use /dev/tty ... */
fputs(prompt, stdout);
fflush(stdout);
if (!fgets(buf, sizeof(buf), stdin))
return 0;
len = strlen(buf);
if (len && buf[len - 1] == '\n')
buf[--len] = 0;
return strdup(buf);
case ConvGetHidden:
if (havetty) {
#ifdef HAVE_GETPASSPHRASE
p = getpassphrase(prompt ? prompt : "Password: ");
#else
p = getpass(prompt ? prompt : "Password: ");
#endif
p2 = strdup(p);
memset(p, 0, strlen(p));
return p2;
} else {
if (prompt)
break;
if ((len = read(0, buf, sizeof(buf) - 1)) < 0) {
message("Cannot read password\n");
return 0;
} else {
if (len && buf[len - 1] == '\n')
--len;
buf[len] = 0;
p2 = strdup(buf);
memset(buf, 0, len);
return p2;
}
}
case ConvPutInfo:
message("Information: %s\n", prompt);
return 0;
case ConvPutError:
message("Error: %s\n", prompt);
return 0;
}
message("Authentication backend requested data type which cannot be handled.\n");
return 0;
}
static int
Reader (void *buf, int count)
{
int ret, rlen;
for (rlen = 0; rlen < count; ) {
dord:
ret = read (sfd, (void *)((char *)buf + rlen), count - rlen);
if (ret < 0) {
if (errno == EINTR)
goto dord;
if (errno == EAGAIN)
break;
return -1;
}
if (!ret)
break;
rlen += ret;
}
return rlen;
}
static void
GRead (void *buf, int count)
{
if (Reader (buf, count) != count) {
message ("Communication breakdown on read\n");
exit(15);
}
}
static void
GWrite (const void *buf, int count)
{
if (write (sfd, buf, count) != count) {
message ("Communication breakdown on write\n");
exit(15);
}
}
static void
GSendInt (int val)
{
GWrite (&val, sizeof(val));
}
static void
GSendStr (const char *buf)
{
unsigned len = buf ? strlen (buf) + 1 : 0;
GWrite (&len, sizeof(len));
GWrite (buf, len);
}
static void
GSendArr (int len, const char *buf)
{
GWrite (&len, sizeof(len));
GWrite (buf, len);
}
static int
GRecvInt (void)
{
int val;
GRead (&val, sizeof(val));
return val;
}
static char *
GRecvStr (void)
{
unsigned len;
char *buf;
if (!(len = GRecvInt()))
return (char *)0;
if (len > 0x1000 || !(buf = malloc (len))) {
message ("No memory for read buffer\n");
exit(15);
}
GRead (buf, len);
buf[len - 1] = 0; /* we're setuid ... don't trust "them" */
return buf;
}
static char *
GRecvArr (void)
{
unsigned len;
char *arr;
if (!(len = (unsigned) GRecvInt()))
return (char *)0;
if (len > 0x10000 || !(arr = malloc (len))) {
message ("No memory for read buffer\n");
exit(15);
}
GRead (arr, len);
return arr;
}
static char *
conv_server (ConvRequest what, const char *prompt)
{
GSendInt (what);
switch (what) {
case ConvGetBinary:
{
unsigned const char *up = (unsigned const char *)prompt;
int len = up[3] | (up[2] << 8) | (up[1] << 16) | (up[0] << 24);
GSendArr (len, prompt);
return GRecvArr ();
}
case ConvGetNormal:
case ConvGetHidden:
{
char *msg;
GSendStr (prompt);
msg = GRecvStr ();
if (msg && (GRecvInt() & IsPassword) && !*msg)
nullpass = 1;
return msg;
}
case ConvPutInfo:
case ConvPutError:
default:
GSendStr (prompt);
return 0;
}
}
void
message(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
vfprintf(stderr, fmt, ap);
va_end(ap);
}
#ifndef O_NOFOLLOW
# define O_NOFOLLOW 0
#endif
static void ATTR_NORETURN
usage(int exitval)
{
message(
"usage: kcheckpass {-h|[-c caller] [-m method] [-U username|-S handle]}\n"
" options:\n"
" -h this help message\n"
" -U username authenticate the specified user instead of current user\n"
" -S handle operate in binary server mode on file descriptor handle\n"
" -c caller the calling application, effectively the PAM service basename\n"
" -m method use the specified authentication method (default: \"classic\")\n"
" exit codes:\n"
" 0 success\n"
" 1 invalid password\n"
" 2 cannot read password database\n"
" Anything else tells you something's badly hosed.\n"
);
exit(exitval);
}
int
main(int argc, char **argv)
{
#ifdef HAVE_PAM
const char *caller = KCHECKPASS_PAM_SERVICE;
#endif
const char *method = "classic";
const char *username = 0;
#ifdef ACCEPT_ENV
char *p;
#endif
struct passwd *pw;
int c, nfd, lfd;
uid_t uid;
time_t nexttime;
AuthReturn ret;
struct flock lk;
char fname[64], fcont[64];
#ifdef HAVE_OSF_C2_PASSWD
initialize_osf_security(argc, argv);
#endif
/* Make sure stdout/stderr are open */
for (c = 1; c <= 2; c++) {
if (fcntl(c, F_GETFL) == -1) {
if ((nfd = open("/dev/null", O_WRONLY)) < 0) {
message("cannot open /dev/null: %s\n", strerror(errno));
exit(10);
}
if (c != nfd) {
dup2(nfd, c);
close(nfd);
}
}
}
havetty = isatty(0);
while ((c = getopt(argc, argv, "hc:m:U:S:")) != -1) {
switch (c) {
case 'h':
usage(0);
break;
case 'c':
#ifdef HAVE_PAM
caller = optarg;
#endif
break;
case 'm':
method = optarg;
break;
case 'U':
username = optarg;
break;
case 'S':
sfd = atoi(optarg);
break;
default:
message("Command line option parsing error\n");
usage(10);
}
}
#ifdef ACCEPT_ENV
# ifdef HAVE_PAM
if ((p = getenv("TDE_PAM_ACTION")))
caller = p;
# endif
if ((p = getenv("TCHECKPASS_USER")))
username = p;
#endif
uid = getuid();
if (!username) {
if (!(p = getenv("LOGNAME")) || !(pw = getpwnam(p)) || pw->pw_uid != uid)
if (!(p = getenv("USER")) || !(pw = getpwnam(p)) || pw->pw_uid != uid)
if (!(pw = getpwuid(uid))) {
message("Cannot determinate current user\n");
return AuthError;
}
if (!(username = strdup(pw->pw_name))) {
message("Out of memory\n");
return AuthError;
}
}
/*
* Throttle kcheckpass invocations to avoid abusing it for bruteforcing
* the password. This delay belongs to the *previous* invocation, where
* we can't enforce it reliably (without risking giving away the result
* before it is due). We don't differentiate between success and failure -
* it's not expected to have a noticable adverse effect.
*/
if ( uid != geteuid() ) {
sprintf(fname, "/var/run/kcheckpass.%d", uid);
if ((lfd = open(fname, O_RDWR | O_CREAT | O_NOFOLLOW, 0600)) < 0) {
message("Cannot open lockfile\n");
return AuthError;
}
lk.l_type = F_WRLCK;
lk.l_whence = SEEK_SET;
lk.l_start = lk.l_len = 0;
if (fcntl(lfd, F_SETLKW, &lk)) {
message("Cannot obtain lock\n");
return AuthError;
}
if ((c = read(lfd, fcont, sizeof(fcont)-1)) > 0 &&
(fcont[c] = '\0', sscanf(fcont, "%ld", &nexttime) == 1))
{
time_t ct = time(0);
if (nexttime > ct && nexttime < ct + THROTTLE)
sleep(nexttime - ct);
}
lseek(lfd, 0, SEEK_SET);
write(lfd, fcont, sprintf(fcont, "%lu\n", time(0) + THROTTLE));
close(lfd);
}
/* Now do the fandango */
ret = Authenticate(
#ifdef HAVE_PAM
caller,
#endif
method,
username,
sfd < 0 ? conv_legacy : conv_server);
if (ret == AuthBad) {
message("Authentication failure\n");
if (!nullpass) {
openlog("kcheckpass", LOG_PID, LOG_AUTH);
syslog(LOG_NOTICE, "Authentication failure for %s (invoked by uid %d)", username, uid);
}
}
return ret;
}
void
dispose(char *str)
{
memset(str, 0, strlen(str));
free(str);
}
/*****************************************************************
The real authentication methods are in separate source files.
Look in checkpass_*.c
*****************************************************************/