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/* $OpenBSD: pwd_check.c,v 1.16 2017/08/21 21:41:13 deraadt Exp $ */
/*
* Copyright 2000 Niels Provos <provos@citi.umich.edu>
* 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 Niels Provos.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <errno.h>
#include <err.h>
#include <regex.h>
#include <grp.h>
#include <paths.h>
#include <login_cap.h>
#include <signal.h>
int pwd_check(login_cap_t *, char *);
int pwd_gettries(login_cap_t *);
struct pattern {
char *match;
int flags;
char *response;
};
struct pattern patterns[] = {
{
"^[0-9]*$",
REG_EXTENDED|REG_NOSUB,
"Please don't use all-digit passwords."
},
{
"^[a-z]{1,9}$",
REG_EXTENDED|REG_NOSUB,
"Please don't use an all-lower case password."
},
{
"^[a-z]{1,6}[0-9]+$",
REG_EXTENDED|REG_NOSUB|REG_ICASE,
"Please use a more complicated password."
},
{
"^([a-z][0-9]){1,4}$",
REG_EXTENDED|REG_NOSUB|REG_ICASE,
"Please use a more complicated password."
},
{
"^([0-9][a-z]){1,4}$",
REG_EXTENDED|REG_NOSUB|REG_ICASE,
"Please use a more complicated password."
}
};
int
pwd_check(login_cap_t *lc, char *password)
{
regex_t rgx;
int i, res, min_len;
char *checker;
char *argp[] = { "sh", "-c", NULL, NULL};
int pipefds[2];
pid_t child;
uid_t uid;
gid_t gid;
min_len = (int)login_getcapnum(lc, "minpasswordlen", 6, 6);
if (min_len > 0 && strlen(password) < min_len) {
printf("Please enter a longer password.\n");
return (0);
}
/* External password check program */
checker = login_getcapstr(lc, "passwordcheck", NULL, NULL);
/* Pipes are only used for external checker */
if (checker != NULL && pipe(pipefds) == -1) {
warn("pipe");
goto out;
}
/* Check password in low-privileged child */
switch (child = fork()) {
case -1:
warn("fork");
goto out;
case 0:
(void)signal(SIGINT, SIG_DFL);
(void)signal(SIGQUIT, SIG_DFL);
uid = getuid();
gid = getgid();
if (setresgid(gid, gid, gid) == -1) {
warn("setresgid");
exit(1);
}
if (setgroups(1, &gid) == -1) {
warn("setgroups");
exit(1);
}
if (setresuid(uid, uid, uid) == -1) {
warn("setresuid");
exit(1);
}
if (checker == NULL) {
if (pledge("stdio", NULL) == -1)
err(1, "pledge");
for (i = 0; i < sizeof(patterns) / sizeof(*patterns); i++) {
int ret;
if (regcomp(&rgx, patterns[i].match,
patterns[i].flags) != 0)
continue;
ret = regexec(&rgx, password, 0, NULL, 0);
regfree(&rgx);
if (ret == 0) {
printf("%s\n", patterns[i].response);
exit(1);
}
}
/* no external checker in use, accept the password */
exit(0);
}
if (pledge("stdio exec", NULL) == -1)
err(1, "pledge");
/* Otherwise, pass control to checker program */
argp[2] = checker;
if (dup2(pipefds[0], STDIN_FILENO) == -1) {
warn("dup2");
exit(1);
}
close(pipefds[0]);
close(pipefds[1]);
if (execv(_PATH_BSHELL, argp) == -1) {
warn("exec");
exit(1);
}
/* NOTREACHED */
default:
break; /* parent continues below */
}
if (checker != NULL) {
/* Send the password to STDIN of child */
close(pipefds[0]);
write(pipefds[1], password, strlen(password) + 1);
close(pipefds[1]);
}
/* get the return value from the child */
while (waitpid(child, &res, 0) == -1) {
if (errno != EINTR)
break;
}
if (WIFEXITED(res) && WEXITSTATUS(res) == 0) {
free(checker);
return (1);
}
out:
free(checker);
printf("Please use a different password. Unusual capitalization,\n");
printf("control characters, or digits are suggested.\n");
return (0);
}
int
pwd_gettries(login_cap_t *lc)
{
quad_t ntries;
if ((ntries = login_getcapnum(lc, "passwordtries", -1, -1)) != -1) {
if (ntries >= 0 && ntries <= INT_MAX)
return((int)ntries);
fprintf(stderr,
"Warning: pwdtries out of range in /etc/login.conf");
}
/*
* If no amount of tries is specified, return a default of 3,
* meaning that after 3 attempts where the user is foiled by the
* password checks, it will no longer be checked and they can set
* it to whatever they like. This is the historic BSD behavior.
*/
return (3);
}
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