/* Copyright (c) 2015-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"

#include "buffer.h"

#include "str.h"

#include "password-scheme.h"

#include "hex-binary.h"

#include "hash-method.h"

#include "pkcs5.h"

#define PBKDF2_KEY_SIZE_SHA1 20

#define PBKDF2_GENERATE_SALT_LEN      16

#define PBKDF2_ROUNDS_DEFAULT          5000

static void

pbkdf_run(const char *plaintext, const char *salt,

    unsigned int rounds, unsigned char key_r[PBKDF2_KEY_SIZE_SHA1])

{

  memset(key_r, 0, PBKDF2_KEY_SIZE_SHA1);

  buffer_t buf;

  buffer_create_from_data(&buf, key_r, PBKDF2_KEY_SIZE_SHA1);

  pkcs5_pbkdf(PKCS5_PBKDF2, hash_method_lookup("sha1"),

    (const unsigned char *)plaintext, strlen(plaintext),

    (const unsigned char *)salt, strlen(salt),

    rounds, PBKDF2_KEY_SIZE_SHA1, &buf);

}

void pbkdf2_generate(const char *plaintext, const struct password_generate_params *params ATTR_UNUSED,

    const unsigned char **raw_password_r, size_t *size_r)

{

  unsigned char key[PBKDF2_KEY_SIZE_SHA1];

  const char *salt;

  string_t *str = t_str_new(64);

  unsigned int rounds = params->rounds;

  if (rounds == 0)

    rounds = PBKDF2_ROUNDS_DEFAULT;

  salt = password_generate_salt(PBKDF2_GENERATE_SALT_LEN);

  pbkdf_run(plaintext, salt, rounds, key);

  str_printfa(str, "$1$%s$%u$", salt, rounds);

  binary_to_hex_append(str, key, sizeof(key));

  *raw_password_r = str_data(str);

  *size_r = str_len(str);

}

int pbkdf2_verify(const char *plaintext, const struct password_generate_params *params ATTR_UNUSED,

        const unsigned char *raw_password, size_t size,

        const char **error_r)

{

  const char *const *fields;

  const char *salt;

  unsigned int rounds;

  unsigned char key1[PBKDF2_KEY_SIZE_SHA1], key2[PBKDF2_KEY_SIZE_SHA1];

  buffer_t buf;

  /* $1$salt$rounds$hash */

  if (size < 3 || memcmp(raw_password, "$1$", 3) != 0) {

    *error_r = "Invalid PBKDF2 passdb entry prefix";

    return -1;

  }

  fields = t_strsplit(t_strndup(raw_password + 3, size - 3), "$");

  salt = fields[0];

  if (str_array_length(fields) != 3 ||

      str_to_uint(fields[1], &rounds) < 0) {

    *error_r = "Invalid PBKDF2 passdb entry format";

    return -1;

  }

  buffer_create_from_data(&buf, key1, sizeof(key1));

  if (strlen(fields[2]) != sizeof(key1)*2 ||

      hex_to_binary(fields[2], &buf) < 0) {

    *error_r = "PBKDF2 hash not 160bit hex-encoded";

    return -1;

  }

  pbkdf_run(plaintext, salt, rounds, key2);

  return mem_equals_timing_safe(key1, key2, sizeof(key1)) ? 1 : 0;

}