/*

   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 "replace.h"

#include "system/locale.h"

#include <tevent.h>

#include "lib/util/samba_util.h"

#include "lib/util/debug.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);

}

/**

  @brief generate a random uint64

**/

_PUBLIC_ uint64_t generate_random_u64(void)

{

  uint8_t v[8];

  generate_random_buffer(v, 8);

  return BVAL(v, 0);

}

/**

 * @brief Generate a random number in the given range.

 *

 * @param lower    The lower value of the range

 * @param upper    The upper value of the range

 *

 * @return A random number bigger than than lower and smaller than upper.

 */

_PUBLIC_ uint64_t generate_random_u64_range(uint64_t lower, uint64_t upper)

{

  return generate_random_u64() % (upper - lower) + lower;

}

_PUBLIC_ uint64_t generate_unique_u64(uint64_t veto_value)

{

  static struct generate_unique_u64_state {

    uint64_t next_value;

    int pid;

  } generate_unique_u64_state;

  int pid = tevent_cached_getpid();

  if (unlikely(pid != generate_unique_u64_state.pid)) {

    generate_unique_u64_state = (struct generate_unique_u64_state) {

      .pid = pid,

      .next_value = veto_value,

    };

  }

  generate_unique_u64_state.next_value++;

  while (unlikely(generate_unique_u64_state.next_value == veto_value)) {

    generate_nonce_buffer(

        (void *)&generate_unique_u64_state.next_value,

        sizeof(generate_unique_u64_state.next_value));

  }

  return generate_unique_u64_state.next_value;

}

/**

  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_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;

    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;

}

_PUBLIC_ char *generate_random_str_list_buf(char *buf,

              size_t buflen,

              const char *list)

{

  const size_t list_len = strlen(list);

  size_t i, len;

  if (buflen == 0) {

    return buf;

  }

  buf[buflen-1] = '\0';

  if (buflen == 1) {

    return buf;

  }

  len = buflen-1;

  generate_secret_buffer((uint8_t *)buf, len);

  for (i=0; i<len; i++) {

    buf[i] = list[(uint8_t)buf[i] % list_len];

  }

  return buf;

}

/**

 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)

{

  char *retstr = talloc_array(mem_ctx, char, len + 1);

  if (!retstr) return NULL;

  return generate_random_str_list_buf(retstr, len+1, list);

}

/**

 * 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 (based on printable ascii characters).

 */

_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_secret_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 a random machine password (based on random utf16 characters,

 * converted to utf8). min must be at least 14, max must be at most 255.

 *

 * If 'unix charset' is not utf8, the password consist of random ascii

 * values!

 *

 * The return value is a talloc string with destructor talloc_keep_secret() set.

 * The content will be overwritten by zeros when the mem_ctx is destroyed.

 */

_PUBLIC_ char *generate_random_machine_password(TALLOC_CTX *mem_ctx, size_t min, size_t max)

{

  TALLOC_CTX *frame = NULL;

  struct generate_random_machine_password_state {

    uint8_t password_buffer[256 * 2];

    uint8_t tmp;

  } *state;

  char *new_pw = NULL;

  size_t len = max;

  char *utf8_pw = NULL;

  size_t utf8_len = 0;

  char *unix_pw = NULL;

  size_t unix_len = 0;

  size_t diff;

  size_t i;

  bool ok;

  int cmp;

  if (max > 255) {

    errno = EINVAL;

    return NULL;

  }

  if (min < 14) {

    errno = EINVAL;

    return NULL;

  }

  if (min > max) {

    errno = EINVAL;

    return NULL;

  }

  frame = talloc_stackframe_pool(2048);

  state = talloc_zero(frame, struct generate_random_machine_password_state);

  talloc_keep_secret(state);

  diff = max - min;

  if (diff > 0) {

    size_t tmp;

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

    tmp %= diff;

    len = min + tmp;

  }

  /*

   * Create a random machine account password

   * We create a random buffer and convert that to utf8.

   * This is similar to what windows is doing.

   *

   * In future we may store the raw random buffer,

   * but for now we need to pass the password as

   * char pointer through some layers.

   *

   * As most kerberos keys are derived from the

   * utf8 password we need to fallback to

   * ASCII passwords if "unix charset" is not utf8.

   */

  generate_secret_buffer(state->password_buffer, len * 2);

  for (i = 0; i < len; i++) {

    size_t idx = i*2;

    uint16_t c;

    /*

     * both MIT krb5 and HEIMDAL only

     * handle codepoints up to 0xffff.

     *

     * It means we need to avoid

     * 0xD800 - 0xDBFF (high surrogate)

     * and

     * 0xDC00 - 0xDFFF (low surrogate)

     * in the random utf16 data.

     *

     * 55296 0xD800 0154000 0b1101100000000000

     * 57343 0xDFFF 0157777 0b1101111111111111

     * 8192  0x2000  020000   0b10000000000000

     *

     * The above values show that we can check

     * for 0xD800 and just add 0x2000 to avoid

     * the surrogate ranges.

     *

     * The rest will be handled by CH_UTF16MUNGED

     * see utf16_munged_pull().

     */

    c = SVAL(state->password_buffer, idx);

    if (c & 0xD800) {

      c |= 0x2000;

    }

    SSVAL(state->password_buffer, idx, c);

  }

  ok = convert_string_talloc(frame,

           CH_UTF16MUNGED, CH_UTF8,

           state->password_buffer, len * 2,

           (void *)&utf8_pw, &utf8_len);

  if (!ok) {

    DEBUG(0, ("%s: convert_string_talloc() failed\n",

        __func__));

    TALLOC_FREE(frame);

    return NULL;

  }

  talloc_keep_secret(utf8_pw);

  ok = convert_string_talloc(frame,

           CH_UTF16MUNGED, CH_UNIX,

           state->password_buffer, len * 2,

           (void *)&unix_pw, &unix_len);

  if (!ok) {

    goto ascii_fallback;

  }

  talloc_keep_secret(unix_pw);

  if (utf8_len != unix_len) {

    goto ascii_fallback;

  }

  cmp = memcmp((const uint8_t *)utf8_pw,

         (const uint8_t *)unix_pw,

         utf8_len);

  if (cmp != 0) {

    goto ascii_fallback;

  }

  new_pw = talloc_strdup(mem_ctx, utf8_pw);

  if (new_pw == NULL) {

    TALLOC_FREE(frame);

    return NULL;

  }

  talloc_keep_secret(new_pw);

  TALLOC_FREE(frame);

  return new_pw;

ascii_fallback:

  for (i = 0; i < len; i++) {

    /*

     * truncate to ascii

     */

    state->tmp = state->password_buffer[i] & 0x7f;

    if (state->tmp == 0) {

      state->tmp = state->password_buffer[i] >> 1;

    }

    if (state->tmp == 0) {

      state->tmp = 0x01;

    }

    state->password_buffer[i] = state->tmp;

  }

  state->password_buffer[i] = '\0';

  new_pw = talloc_strdup(mem_ctx, (const char *)state->password_buffer);

  if (new_pw == NULL) {

    TALLOC_FREE(frame);

    return NULL;

  }

  talloc_keep_secret(new_pw);

  talloc_set_name_const(new_pw, __func__);

  TALLOC_FREE(frame);

  return new_pw;

}

/**

 * 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;

}