source: vendor/current/lib/util/genrand_util.c

/*
   Unix SMB/CIFS implementation.

   Functions to create reasonable random numbers for crypto use.

   Copyright (C) Jeremy Allison 2001

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "system/locale.h"

/**
 * @file
 * @brief Random number generation
 */

/**
  generate a single random uint32_t
**/
_PUBLIC_ uint32_t generate_random(void)
{
        uint8_t v[4];
        generate_random_buffer(v, 4);
        return IVAL(v, 0);
}


/**
  Microsoft composed the following rules (among others) for quality
  checks. This is an abridgment from
  http://msdn.microsoft.com/en-us/subscriptions/cc786468%28v=ws.10%29.aspx:

  Passwords must contain characters from three of the following five
  categories:

   - Uppercase characters of European languages (A through Z, with
     diacritic marks, Greek and Cyrillic characters)
   - Lowercase characters of European languages (a through z, sharp-s,
     with diacritic marks, Greek and Cyrillic characters)
   - Base 10 digits (0 through 9)
   - Nonalphanumeric characters: ~!@#$%^&*_-+=`|\(){}[]:;"'<>,.?/
   - Any Unicode character that is categorized as an alphabetic character
     but is not uppercase or lowercase. This includes Unicode characters
     from Asian languages.

 Note: for now do not check if the unicode category is
       alphabetic character
**/
_PUBLIC_ bool check_password_quality(const char *pwd)
{
        size_t ofs = 0;
        size_t num_chars = 0;
        size_t num_digits = 0;
        size_t num_upper = 0;
        size_t num_lower = 0;
        size_t num_nonalpha = 0;
        size_t num_unicode = 0;
        size_t num_categories = 0;

        if (pwd == NULL) {
                return false;
        }

        while (true) {
                const char *s = &pwd[ofs];
                size_t len = 0;
                codepoint_t c;

                c = next_codepoint(s, &len);
                if (c == INVALID_CODEPOINT) {
                        return false;
                } else if (c == 0) {
                        break;
                }
                ofs += len;
                num_chars += 1;

                if (len == 1) {
                        const char *na = "~!@#$%^&*_-+=`|\\(){}[]:;\"'<>,.?/";

                        if (isdigit(c)) {
                                num_digits += 1;
                                continue;
                        }

                        if (isupper(c)) {
                                num_upper += 1;
                                continue;
                        }

                        if (islower(c)) {
                                num_lower += 1;
                                continue;
                        }

                        if (strchr(na, c)) {
                                num_nonalpha += 1;
                                continue;
                        }

                        /*
                         * the rest does not belong to
                         * a category.
                         */
                        continue;
                }

                if (isupper_m(c)) {
                        num_upper += 1;
                        continue;
                }

                if (islower_m(c)) {
                        num_lower += 1;
                        continue;
                }

                /*
                 * Note: for now do not check if the unicode category is
                 *       alphabetic character
                 *
                 * We would have to import the details from
                 * ftp://ftp.unicode.org/Public/6.3.0/ucd/UnicodeData-6.3.0d1.txt
                 */
                num_unicode += 1;
                continue;
        }

        if (num_digits > 0) {
                num_categories += 1;
        }
        if (num_upper > 0) {
                num_categories += 1;
        }
        if (num_lower > 0) {
                num_categories += 1;
        }
        if (num_nonalpha > 0) {
                num_categories += 1;
        }
        if (num_unicode > 0) {
                num_categories += 1;
        }

        if (num_categories >= 3) {
                return true;
        }

        return false;
}

/**
 Use the random number generator to generate a random string.
**/

_PUBLIC_ char *generate_random_str_list(TALLOC_CTX *mem_ctx, size_t len, const char *list)
{
        size_t i;
        size_t list_len = strlen(list);

        char *retstr = talloc_array(mem_ctx, char, len + 1);
        if (!retstr) return NULL;

        generate_random_buffer((uint8_t *)retstr, len);
        for (i = 0; i < len; i++) {
                retstr[i] = list[retstr[i] % list_len];
        }
        retstr[i] = '\0';

        return retstr;
}

/**
 * Generate a random text string consisting of the specified length.
 * The returned string will be allocated.
 *
 * Characters used are: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_-#.,
 */

_PUBLIC_ char *generate_random_str(TALLOC_CTX *mem_ctx, size_t len)
{
        char *retstr;
        const char *c_list = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_-#.,";

again:
        retstr = generate_random_str_list(mem_ctx, len, c_list);
        if (!retstr) return NULL;

        /* we need to make sure the random string passes basic quality tests
           or it might be rejected by windows as a password */
        if (len >= 7 && !check_password_quality(retstr)) {
                talloc_free(retstr);
                goto again;
        }

        return retstr;
}

/**
 * Generate a random text password.
 */

_PUBLIC_ char *generate_random_password(TALLOC_CTX *mem_ctx, size_t min, size_t max)
{
        char *retstr;
        /* This list does not include { or } because they cause
         * problems for our provision (it can create a substring
         * ${...}, and for Fedora DS (which treats {...} at the start
         * of a stored password as special
         *  -- Andrew Bartlett 2010-03-11
         */
        const char *c_list = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_-#.,@$%&!?:;<=>()[]~";
        size_t len = max;
        size_t diff;

        if (min > max) {
                errno = EINVAL;
                return NULL;
        }

        diff = max - min;

        if (diff > 0 ) {
                size_t tmp;

                generate_random_buffer((uint8_t *)&tmp, sizeof(tmp));

                tmp %= diff;

                len = min + tmp;
        }

again:
        retstr = generate_random_str_list(mem_ctx, len, c_list);
        if (!retstr) return NULL;

        /* we need to make sure the random string passes basic quality tests
           or it might be rejected by windows as a password */
        if (len >= 7 && !check_password_quality(retstr)) {
                talloc_free(retstr);
                goto again;
        }

        return retstr;
}

/**
 * Generate an array of unique text strings all of the same length.
 * The returned string will be allocated.
 * Returns NULL if the number of unique combinations cannot be created.
 *
 * Characters used are: abcdefghijklmnopqrstuvwxyz0123456789+_-#.,
 */
_PUBLIC_ char** generate_unique_strs(TALLOC_CTX *mem_ctx, size_t len,
                                     uint32_t num)
{
        const char *c_list = "abcdefghijklmnopqrstuvwxyz0123456789+_-#.,";
        const unsigned c_size = 42;
        size_t i, j;
        unsigned rem;
        char ** strs = NULL;

        if (num == 0 || len == 0)
                return NULL;

        strs = talloc_array(mem_ctx, char *, num);
        if (strs == NULL) return NULL;

        for (i = 0; i < num; i++) {
                char *retstr = (char *)talloc_size(strs, len + 1);
                if (retstr == NULL) {
                        talloc_free(strs);
                        return NULL;
                }
                rem = i;
                for (j = 0; j < len; j++) {
                        retstr[j] = c_list[rem % c_size];
                        rem = rem / c_size;
                }
                retstr[j] = 0;
                strs[i] = retstr;
                if (rem != 0) {
                        /* we were not able to fit the number of
                         * combinations asked for in the length
                         * specified */
                        DEBUG(0,(__location__ ": Too many combinations %u for length %u\n",
                                 num, (unsigned)len));

                        talloc_free(strs);
                        return NULL;
                }
        }

        return strs;
}