/*
* Copyright (c) 2000-2002 by Solar Designer. See LICENSE.
*/
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <pwd.h>
#include "passwdqc.h"
#define REASON_ERROR \
"check failed"
#define REASON_SAME \
"is the same as the old one"
#define REASON_SIMILAR \
"is based on the old one"
#define REASON_SHORT \
"too short"
#define REASON_LONG \
"too long"
#define REASON_SIMPLESHORT \
"not enough different characters or classes for this length"
#define REASON_SIMPLE \
"not enough different characters or classes"
#define REASON_PERSONAL \
"based on personal login information"
#define REASON_WORD \
"based on a dictionary word and not a passphrase"
#define FIXED_BITS 15
typedef unsigned long fixed;
/*
* Calculates the expected number of different characters for a random
* password of a given length. The result is rounded down. We use this
* with the _requested_ minimum length (so longer passwords don't have
* to meet this strict requirement for their length).
*/
static int expected_different(int charset, int length)
{
fixed x, y, z;
x = ((fixed)(charset - 1) << FIXED_BITS) / charset;
y = x;
while (--length > 0) y = (y * x) >> FIXED_BITS;
z = (fixed)charset * (((fixed)1 << FIXED_BITS) - y);
return (int)(z >> FIXED_BITS);
}
/*
* A password is too simple if it is too short for its class, or doesn't
* contain enough different characters for its class, or doesn't contain
* enough words for a passphrase.
*/
static int is_simple(passwdqc_params_t *params, const char *newpass)
{
int length, classes, words, chars;
int digits, lowers, uppers, others, unknowns;
int c, p;
length = classes = words = chars = 0;
digits = lowers = uppers = others = unknowns = 0;
p = ' ';
while ((c = (unsigned char)newpass[length])) {
length++;
if (!isascii(c)) unknowns++; else
if (isdigit(c)) digits++; else
if (islower(c)) lowers++; else
if (isupper(c)) uppers++; else
others++;
if (isascii(c) && isalpha(c) && isascii(p) && !isalpha(p))
words++;
p = c;
if (!strchr(&newpass[length], c))
chars++;
}
if (!length) return 1;
/* Upper case characters and digits used in common ways don't increase the
* strength of a password */
c = (unsigned char)newpass[0];
if (uppers && isascii(c) && isupper(c)) uppers--;
c = (unsigned char)newpass[length - 1];
if (digits && isascii(c) && isdigit(c)) digits--;
/* Count the number of different character classes we've seen. We assume
* that there're no non-ASCII characters for digits. */
classes = 0;
if (digits) classes++;
if (lowers) classes++;
if (uppers) classes++;
if (others) classes++;
if (unknowns && (!classes || (digits && classes == 1))) classes++;
for (; classes > 0; classes--)
switch (classes) {
case 1:
if (length >= params->min[0] &&
chars >= expected_different(10, params->min[0]) - 1)
return 0;
return 1;
case 2:
if (length >= params->min[1] &&
chars >= expected_different(36, params->min[1]) - 1)
return 0;
if (!params->passphrase_words ||
words < params->passphrase_words)
continue;
if (length >= params->min[2] &&
chars >= expected_different(27, params->min[2]) - 1)
return 0;
continue;
case 3:
if (length >= params->min[3] &&
chars >= expected_different(62, params->min[3]) - 1)
return 0;
continue;
case 4:
if (length >= params->min[4] &&
chars >= expected_different(95, params->min[4]) - 1)
return 0;
continue;
}
return 1;
}
static char *unify(const char *src)
{
const char *sptr;
char *dst, *dptr;
int c;
if (!(dst = malloc(strlen(src) + 1)))
return NULL;
sptr = src;
dptr = dst;
do {
c = (unsigned char)*sptr;
if (isascii(c) && isupper(c))
*dptr++ = tolower(c);
else
*dptr++ = *sptr;
} while (*sptr++);
return dst;
}
static char *reverse(const char *src)
{
const char *sptr;
char *dst, *dptr;
if (!(dst = malloc(strlen(src) + 1)))
return NULL;
sptr = &src[strlen(src)];
dptr = dst;
while (sptr > src)
*dptr++ = *--sptr;
*dptr = '\0';
return dst;
}
static void clean(char *dst)
{
if (dst) {
memset(dst, 0, strlen(dst));
free(dst);
}
}
/*
* Needle is based on haystack if both contain a long enough common
* substring and needle would be too simple for a password with the
* substring removed.
*/
static int is_based(passwdqc_params_t *params,
const char *haystack, const char *needle, const char *original)
{
char *scratch;
int length;
int i, j;
const char *p;
int match;
if (!params->match_length) /* disabled */
return 0;
if (params->match_length < 0) /* misconfigured */
return 1;
if (strstr(haystack, needle)) /* based on haystack entirely */
return 1;
scratch = NULL;
length = strlen(needle);
for (i = 0; i <= length - params->match_length; i++)
for (j = params->match_length; i + j <= length; j++) {
match = 0;
for (p = haystack; *p; p++)
if (*p == needle[i] && !strncmp(p, &needle[i], j)) {
match = 1;
if (!scratch) {
if (!(scratch = malloc(length + 1)))
return 1;
}
memcpy(scratch, original, i);
memcpy(&scratch[i], &original[i + j],
length + 1 - (i + j));
if (is_simple(params, scratch)) {
clean(scratch);
return 1;
}
}
if (!match) break;
}
clean(scratch);
return 0;
}
/*
* This wordlist check is now the least important given the checks above
* and the support for passphrases (which are based on dictionary words,
* and checked by other means). It is still useful to trap simple short
* passwords (if short passwords are allowed) that are word-based, but
* passed the other checks due to uncommon capitalization, digits, and
* special characters. We (mis)use the same set of words that are used
* to generate random passwords. This list is much smaller than those
* used for password crackers, and it doesn't contain common passwords
* that aren't short English words. Perhaps support for large wordlists
* should still be added, even though this is now of little importance.
*/
static int is_word_based(passwdqc_params_t *params,
const char *needle, const char *original)
{
char word[7];
char *unified;
int i;
word[6] = '\0';
for (i = 0; i < 0x1000; i++) {
memcpy(word, _passwdqc_wordset_4k[i], 6);
if ((int)strlen(word) < params->match_length) continue;
unified = unify(word);
if (is_based(params, unified, needle, original)) {
clean(unified);
return 1;
}
clean(unified);
}
return 0;
}
const char *_passwdqc_check(passwdqc_params_t *params,
const char *newpass, const char *oldpass, struct passwd *pw)
{
char truncated[9], *reversed;
char *u_newpass, *u_reversed;
char *u_oldpass;
char *u_name, *u_gecos;
const char *reason;
int length;
reversed = NULL;
u_newpass = u_reversed = NULL;
u_oldpass = NULL;
u_name = u_gecos = NULL;
reason = NULL;
if (oldpass && !strcmp(oldpass, newpass))
reason = REASON_SAME;
length = strlen(newpass);
if (!reason && length < params->min[4])
reason = REASON_SHORT;
if (!reason && length > params->max) {
if (params->max == 8) {
truncated[0] = '\0';
strncat(truncated, newpass, 8);
newpass = truncated;
if (oldpass && !strncmp(oldpass, newpass, 8))
reason = REASON_SAME;
} else
reason = REASON_LONG;
}
if (!reason && is_simple(params, newpass)) {
if (length < params->min[1] && params->min[1] <= params->max)
reason = REASON_SIMPLESHORT;
else
reason = REASON_SIMPLE;
}
if (!reason) {
if ((reversed = reverse(newpass))) {
u_newpass = unify(newpass);
u_reversed = unify(reversed);
if (oldpass)
u_oldpass = unify(oldpass);
if (pw) {
u_name = unify(pw->pw_name);
u_gecos = unify(pw->pw_gecos);
}
}
if (!reversed ||
!u_newpass || !u_reversed ||
(oldpass && !u_oldpass) ||
(pw && (!u_name || !u_gecos)))
reason = REASON_ERROR;
}
if (!reason && oldpass && params->similar_deny &&
(is_based(params, u_oldpass, u_newpass, newpass) ||
is_based(params, u_oldpass, u_reversed, reversed)))
reason = REASON_SIMILAR;
if (!reason && pw &&
(is_based(params, u_name, u_newpass, newpass) ||
is_based(params, u_name, u_reversed, reversed) ||
is_based(params, u_gecos, u_newpass, newpass) ||
is_based(params, u_gecos, u_reversed, reversed)))
reason = REASON_PERSONAL;
if (!reason && (int)strlen(newpass) < params->min[2] &&
(is_word_based(params, u_newpass, newpass) ||
is_word_based(params, u_reversed, reversed)))
reason = REASON_WORD;
memset(truncated, 0, sizeof(truncated));
clean(reversed);
clean(u_newpass); clean(u_reversed);
clean(u_oldpass);
clean(u_name); clean(u_gecos);
return reason;
}
