source: MondoRescue/branches/2.2.5/mindi-busybox/libbb/obscure.c@ 1765

/* vi: set sw=4 ts=4: */
/*
 * Mini weak password checker implementation for busybox
 *
 * Copyright (C) 2006 Tito Ragusa <farmatito@tiscali.it>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

/*  A good password:
    1)  should contain at least six characters (man passwd);
    2)  empty passwords are not permitted;
    3)  should contain a mix of four different types of characters
        upper case letters,
        lower case letters,
        numbers,
        special characters such as !@#$%^&*,;".
    This password types should not  be permitted:
    a)  pure numbers: birthdates, social security number, license plate, phone numbers;
    b)  words and all letters only passwords (uppercase, lowercase or mixed)
        as palindromes, consecutive or repetitive letters
        or adjacent letters on your keyboard;
    c)  username, real name, company name or (e-mail?) address
        in any form (as-is, reversed, capitalized, doubled, etc.).
        (we can check only against username, gecos and hostname)
    d)  common and obvious letter-number replacements
        (e.g. replace the letter O with number 0)
        such as "M1cr0$0ft" or "P@ssw0rd" (CAVEAT: we cannot check for them
        without the use of a dictionary).

    For each missing type of characters an increase of password length is
    requested.

    If user is root we warn only.

    CAVEAT: some older versions of crypt() truncates passwords to 8 chars,
    so that aaaaaaaa1Q$ is equal to aaaaaaaa making it possible to fool
    some of our checks. We don't test for this special case as newer versions
    of crypt do not truncate passwords.
*/

#include "libbb.h"

static int string_checker_helper(const char *p1, const char *p2) __attribute__ ((__pure__));

static int string_checker_helper(const char *p1, const char *p2)
{
    /* as-is or capitalized */
    if (strcasecmp(p1, p2) == 0
    /* as sub-string */
    || strcasestr(p2, p1) != NULL
    /* invert in case haystack is shorter than needle */
    || strcasestr(p1, p2) != NULL)
        return 1;
    return 0;
}

static int string_checker(const char *p1, const char *p2)
{
    int size;
    /* check string */
    int ret = string_checker_helper(p1, p2);
    /* Make our own copy */
    char *p = xstrdup(p1);
    /* reverse string */
    size = strlen(p);

    while (size--) {
        *p = p1[size];
        p++;
    }
    /* restore pointer */
    p -= strlen(p1);
    /* check reversed string */
    ret |= string_checker_helper(p, p2);
    /* clean up */
    memset(p, 0, strlen(p1));
    free(p);
    return ret;
}

#define LOWERCASE          1
#define UPPERCASE          2
#define NUMBERS            4
#define SPECIAL            8

static const char *obscure_msg(const char *old_p, const char *new_p, const struct passwd *pw)
{
    int i;
    int c;
    int length;
    int mixed = 0;
    /* Add 2 for each type of characters to the minlen of password */
    int size = CONFIG_PASSWORD_MINLEN + 8;
    const char *p;
    char hostname[255];

    /* size */
    if (!new_p || (length = strlen(new_p)) < CONFIG_PASSWORD_MINLEN)
        return "too short";

    /* no username as-is, as sub-string, reversed, capitalized, doubled */
    if (string_checker(new_p, pw->pw_name)) {
        return "similar to username";
    }
    /* no gecos as-is, as sub-string, reversed, capitalized, doubled */
    if (*pw->pw_gecos && string_checker(new_p, pw->pw_gecos)) {
        return "similar to gecos";
    }
    /* hostname as-is, as sub-string, reversed, capitalized, doubled */
    if (gethostname(hostname, 255) == 0) {
        hostname[254] = '\0';
        if (string_checker(new_p, hostname)) {
            return "similar to hostname";
        }
    }

    /* Should / Must contain a mix of: */
    for (i = 0; i < length; i++) {
        if (islower(new_p[i])) {        /* a-z */
            mixed |= LOWERCASE;
        } else if (isupper(new_p[i])) { /* A-Z */
            mixed |= UPPERCASE;
        } else if (isdigit(new_p[i])) { /* 0-9 */
            mixed |= NUMBERS;
        } else  {                       /* special characters */
            mixed |= SPECIAL;
        }
        /* More than 50% similar characters ? */
        c = 0;
        p = new_p;
        while (1) {
            if ((p = strchr(p, new_p[i])) == NULL) {
                break;
            }
            c++;
            if (!++p) {
                break; /* move past the matched char if possible */
            }
        }

        if (c >= (length / 2)) {
            return "too many similar characters";
        }
    }
    for (i=0; i<4; i++)
        if (mixed & (1<<i)) size -= 2;
    if (length < size)
        return "too weak";

    if (old_p && old_p[0] != '\0') {
        /* check vs. old password */
        if (string_checker(new_p, old_p)) {
            return "similar to old password";
        }
    }
    return NULL;
}

int obscure(const char *old, const char *newval, const struct passwd *pw)
{
    const char *msg;

    msg = obscure_msg(old, newval, pw);
    if (msg) {
        printf("Bad password: %s\n", msg);
        return 1;
    }
    return 0;
}