xref: /openbsd/usr.bin/passwd/pwd_check.c (revision 6528d8bd)

/*	$OpenBSD: pwd_check.c,v 1.7 2004/03/14 22:53:18 tedu 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 <pwd.h>
#include <util.h>
#include <login_cap.h>

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(struct passwd *pwd, login_cap_t *lc, char *password)
{
	regex_t rgx;
	int i, res, min_len;
	char *cp, option[LINE_MAX];
	int pipefds[2];
	pid_t child;

	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);
	}

	for (i = 0; i < sizeof(patterns)/sizeof(struct pattern); i++) {
		if (regcomp(&rgx, patterns[i].match, patterns[i].flags) != 0)
			continue;
		res = regexec(&rgx, password, 0, NULL, 0);
		regfree(&rgx);
		if (!res) {
			printf("%s\nUnusual capitalization, control characters or digits are suggested.\n", patterns[i].response);
			return (0);
		}
	}

	/* Okay, now pass control to an external program */

	/*
	 * Check login.conf, falling back onto the deprecated passwd.conf
	 */
	if ((cp = login_getcapstr(lc, "passwordcheck", NULL, NULL)) != NULL) {
		strlcpy(option, cp, sizeof(option));
		free(cp);
	} else {
		pw_getconf(option, LINE_MAX, pwd->pw_name, "pwdcheck");

		/* Try to find an entry for the group */
		if (*option == 0) {
			struct group *grp;
			char grpkey[LINE_MAX];

			grp = getgrgid(pwd->pw_gid);
			if (grp != NULL) {
				snprintf(grpkey, LINE_MAX, ":%s",
				    grp->gr_name);
				pw_getconf(option, LINE_MAX, grpkey,
				    "pwdcheck");
			}
			if (grp != NULL && *option == 0 &&
			    strchr(pwd->pw_name, '.') == NULL) {
				snprintf(grpkey, LINE_MAX, ".%s",
				    grp->gr_name);
				pw_getconf(option, LINE_MAX, grpkey,
				    "pwdcheck");
			}
			if (*option == 0)
				pw_getconf(option, LINE_MAX, "default",
				    "pwdcheck");
		}
	}

	/* If no checker is specified, we accept the password */
	if (*option == 0)
		return (1);

	if (pipe(pipefds) == -1) {
		warn("pipe");
		goto out;
	}

	child = fork();
	if (child == 0) {
		char *argp[] = { "sh", "-c", NULL, NULL};

		/* Drop privileges */
		seteuid(getuid());
		setuid(getuid());

		if (dup2(pipefds[0], STDIN_FILENO) == -1)
			exit(1);

		close(pipefds[0]);
		close(pipefds[1]);

		argp[2] = option;
		if (execv(_PATH_BSHELL, argp) == -1)
			exit(1);
		/* NOT REACHED */
	} else if (child == -1) {
		warn("fork");
		goto out;
	}
	close(pipefds[0]);

	/* Send the password to STDIN of child */
	write(pipefds[1], password, strlen(password) + 1);
	close(pipefds[1]);

	/* get the return value from the child */
	wait(&child);
	if (WIFEXITED(child) && WEXITSTATUS(child) == 0)
		return (1);

 out:
	printf("Please use a different password. Unusual capitalization,\n");
	printf("control characters, or digits are suggested.\n");
	return (0);
}

int
pwd_gettries(struct passwd *pwd, login_cap_t *lc)
{
	char option[LINE_MAX];
	char *ep = option;
	quad_t ntries;
	long lval;

	/*
	 * Check login.conf, falling back onto the deprecated passwd.conf
	 */
	if ((ntries = login_getcapnum(lc, "passwordtries", -1, -1)) != -1) {
		if (ntries > INT_MAX || ntries < 0) {
			fprintf(stderr,
			    "Warning: pwdtries out of range in /etc/login.conf");
			goto out;
		}
		return((int)ntries);
	}

	pw_getconf(option, LINE_MAX, pwd->pw_name, "pwdtries");

	/* Try to find an entry for the group */
	if (*option == 0) {
		struct group *grp;
		char grpkey[LINE_MAX];

		grp = getgrgid(pwd->pw_gid);
		if (grp != NULL) {
			snprintf(grpkey, LINE_MAX, ":%s", grp->gr_name);
			pw_getconf(option, LINE_MAX, grpkey, "pwdtries");
		}
		if (grp != NULL && *option == 0 &&
		    strchr(pwd->pw_name, '.') == NULL) {
			snprintf(grpkey, LINE_MAX, ".%s", grp->gr_name);
			pw_getconf(option, LINE_MAX, grpkey, "pwdtries");
		}
		if (*option == 0)
			pw_getconf(option, LINE_MAX, "default", "pwdtries");
	}

	if (*option == 0)
		goto out;

	errno = 0;
	lval = strtol(option, &ep, 10);
	if (option[0] == '\0' || *ep != '\0') {
		fprintf(stderr,
		    "Warning: Bad pwdtries line in /etc/passwd.conf");
		goto out;
	}
	if ((errno == ERANGE && (lval == LONG_MAX || lval == LONG_MIN)) ||
	    (lval > INT_MAX || lval < 0)) {
		fprintf(stderr,
		    "Warning: pwdtries out of range in /etc/passwd.conf");
		goto out;
	}
	return((int) lval);

	/* 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.
	 */
	out:
		return (3);
}