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integrate password quality checking, disallow all digit passwords motivated
by Solar Designer.  External password checking program can be spawned now,
number of password trials configurable.  work by me and Bob Beck.

/*	$OpenBSD: pwd_check.c,v 1.1 2000/08/01 22:27:51 provos 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 <stdio.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <unistd.h>
#include <limits.h>
#include <regex.h>
#include <grp.h>
#include <paths.h>
#include <pwd.h>
#include <sys/errno.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, char *password)
{
	regex_t rgx;
	int i, res;
	char    option[LINE_MAX];
	int pipefds[2];
	
	if (strlen(password) <= 5) {
		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 */
	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-1, ".%s", grp->gr_name);
			grpkey[LINE_MAX-1] = 0;
			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;
	}

	res = fork();
	if (res == 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 (res == -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(&res);
	if (WIFEXITED(res) && WEXITSTATUS(res) == 0)
		return (1);

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

int pwd_gettries( struct passwd *pwd ) {
	char option[LINE_MAX];
	char *ep = option; 

	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-1, ".%s", grp->gr_name);
			grpkey[LINE_MAX-1] = 0;
			pw_getconf(option, LINE_MAX, grpkey, "pwdtries");
		}
		if (*option == 0)
		        pw_getconf(option, LINE_MAX, "default", "pwdtries");
	}
	
	if (*option == 0)
		goto out;
	else {
		long lval;
		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 < INT_MIN)) {
			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);
}