/*

 * Copyright (c) 2012 Tim Ruehsen

 * Copyright (c) 2015-2024 Free Software Foundation, Inc.

 *

 * This file is part of libwget.

 *

 * Libwget is free software: you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * Libwget 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 Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with libwget.  If not, see <https://www.gnu.org/licenses/>.

 *

 *

 * base64 conversion routines

 *

 * Changelog

 * 21.12.2012  Tim Ruehsen  created

 *

 */

#include <config.h>

#include <stddef.h>

#include <stdarg.h>

#include <wget.h>

#include "private.h"

/**

 * \file

 * \brief Base64 functions

 * \defgroup libwget-base64 Base64 functions

 * @{

 *

 * This is a collection base64 encoding/decoding functions used in Wget2.

 */

static const unsigned char base64_2_bin[256] = {

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 62, 0, 62, 0, 63,

  52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, 0, 0, 0, 0,

  0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,

  15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 0, 0, 0, 0, 63,

  0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,

  41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

};

static bool WGET_GCC_CONST isbase64(char c)

{

  // isalnum(c) does not work for all locales

  return base64_2_bin[(unsigned char) c] != 0;

//  return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') || c == '+' || c == '/' || c == '-' || c == '_';

}

/**

 * \param[in] src String to be checked

 * \return 1 if \p src is a base64 string, 0 otherwise

 *

 * Checks whether \p src is a base64 string.

 * Returns 0 if \p src is NULL.

 */

bool wget_base64_is_string(const char *src)

{

  if (src) {

    while (isbase64(*src)) src++;

    if (!*src || (*src == '=' && src[1]) || (*src == '=' && src[1] == '=' && src[2]))

      return 1;

  }

  return 0;

}

/**

 * \param[out] dst Output buffer

 * \param[in] src Base64 string to be decoded

 * \param[in] n Length of \p src

 * \return Number of bytes written into \p dst

 *

 * Decodes \p n bytes of the base64 string \p src.

 * The decoded bytes are written into \p dst and are 0-terminated.

 *

 * The size of \p dst has to be at minimum ((\p n + 3) / 4) * 3 + 1 bytes.

 */

size_t wget_base64_decode(char *dst, const char *src, size_t n)

{

  const unsigned char *usrc = (const unsigned char *)src;

  char *old = dst;

  int extra;

  // trim '=' at the end

  while (n > 0 && !isbase64(src[n - 1]))

    n--;

  extra = n & 3;

  for (n /= 4; n > 0; n--, usrc += 4) {

    *dst++ = (char)(base64_2_bin[usrc[0]] << 2 | base64_2_bin[usrc[1]] >> 4);

    *dst++ = (char)((base64_2_bin[usrc[1]]&0x0F) << 4 | base64_2_bin[usrc[2]] >> 2);

    *dst++ = (char)((base64_2_bin[usrc[2]]&0x03) << 6 | base64_2_bin[usrc[3]]);

  }

  switch (extra) {

  case 1:

    // this should not happen

    *dst++ = (char) (base64_2_bin[usrc[0]] << 2);

    break;

  case 2:

    *dst++ = (char)(base64_2_bin[usrc[0]] << 2 | base64_2_bin[usrc[1]] >> 4);

    *dst = (char)((base64_2_bin[usrc[1]]&0x0F) << 4);

    if (*dst) dst++;

    break;

  case 3:

    *dst++ = (char)(base64_2_bin[usrc[0]] << 2 | base64_2_bin[usrc[1]] >> 4);

    *dst++ = (char)((base64_2_bin[usrc[1]]&0x0F) << 4 | base64_2_bin[usrc[2]] >> 2);

    *dst = (char)((base64_2_bin[usrc[2]]&0x03) << 6);

    if (*dst) dst++;

    break;

  default: // 0: ignore

    break;

  }

  *dst = 0;

  return (size_t) (dst - old);

}

/**

 * \param[in] src Base64 string to be decoded

 * \param[in] n Length of \p src

 * \param[out] outlen Length of returned string, may be NULL.

 * \return Decoded bytes, zero terminated. Returns NULL if memory allocation failed.

 *

 * Decodes \p n bytes of the base64 string \p src.

 * The decoded bytes are returned in an allocated buffer.

 *

 * You should free() the returned string when not needed any more.

 */

char *wget_base64_decode_alloc(const char *src, size_t n, size_t *outlen)

{

  char *dst = wget_malloc(wget_base64_get_decoded_length(n));

  if (!dst)

    return NULL;

  size_t _outlen = wget_base64_decode(dst, src, n);

  if (outlen)

    *outlen = _outlen;

  return dst;

}

#define WGET_BASE64_URLENCODE 1

static size_t base64_encode(char *dst, const char *src, size_t n, int flags)

{

  static const char base64unsafe[64] =

    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

  static const char base64urlsafe[64] =

    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";

  const char *base64 = (flags & WGET_BASE64_URLENCODE) ? base64urlsafe : base64unsafe;

  const unsigned char *usrc = (const unsigned char *)src;

  char *start = dst;

  int extra = n % 3;

  // convert line by line

  for (n /= 3; n > 0; n--, usrc += 3) {

    *dst++ = base64[usrc[0] >> 2];

    *dst++ = base64[((usrc[0]&3) << 4) | (usrc[1] >> 4)];

    *dst++ = base64[((usrc[1]&15) << 2) | (usrc[2] >> 6)];

    *dst++ = base64[usrc[2]&0x3f];

  }

  // special case

  if (extra == 1) {

    *dst++ = base64[usrc[0] >> 2];

    *dst++ = base64[(usrc[0]&3) << 4];

    *dst++ = '=';

    *dst++ = '=';

  } else if (extra == 2) {

    *dst++ = base64[usrc[0] >> 2];

    *dst++ = base64[((usrc[0]&3) << 4) | (usrc[1] >> 4)];

    *dst++ = base64[((usrc[1]&15) << 2)];

    *dst++ = '=';

  }

  *dst = 0;

  return (size_t) (dst - start);

}

/**

 * \param[out] dst Base64 output string

 * \param[in] src Input buffer

 * \param[in] n Number of bytes to be encoded

 * \return Length of output string \p dst

 *

 * Encodes \p n bytes from \p src into a base64 string.

 * The encoded string is written into \p dst (0-terminated).

 *

 * The length of \p dst has to be at minimum ((\p n + 2) / 3) * 4 + 1 bytes.

 */

size_t wget_base64_encode(char *dst, const char *src, size_t n)

{

  return base64_encode(dst, src, n, 0);

}

/**

 * \param[out] dst Base64 output string (URL and filename safe)

 * \param[in] src Input buffer

 * \param[in] n Number of bytes to be encoded

 * \return Length of output string \p dst

 *

 * Encodes \p n bytes from \p src into a base64 URL and filename safe string (see RFC 4648, 5.).

 * The encoded string is written into \p dst (0-terminated).

 *

 * The length of \p dst has to be at minimum ((\p n + 2) / 3) * 4 + 1 bytes.

 */

size_t wget_base64_urlencode(char *dst, const char *src, size_t n)

{

  return base64_encode(dst, src, n, WGET_BASE64_URLENCODE);

}

/**

 * \param[in] src Input buffer

 * \param[in] n Number of bytes to be encoded

 * \return Base64 encoded string or NULL if memory allocation failed

 *

 * Encodes \p n bytes from input buffer \p src.

 * The encoded string is returned in an allocated buffer.

 *

 * You should free() the returned string when not needed any more.

 */

char *wget_base64_encode_alloc(const char *src, size_t n)

{

  char *dst = wget_malloc(wget_base64_get_encoded_length(n));

  if (dst)

    wget_base64_encode(dst, src, n);

  return dst;

}

/**

 * \param[in] fmt Printf-like format string

 * \param[in] args Argument list

 * \return Base64 encoded string

 *

 * Encodes the string constructed by \p fmt and \p args.

 * The encoded string is returned in an allocated buffer.

 *

 * You should free() the returned string when not needed any more.

 */

char *wget_base64_encode_vprintf_alloc(const char *fmt, va_list args)

{

  char *data = NULL;

  size_t n;

  n = wget_vasprintf(&data, fmt, args);

  if (data) {

    char *dst = wget_base64_encode_alloc(data, n);

    xfree(data);

    return dst;

  }

  return NULL;

}

/**

 * \param[in] fmt Printf-like format string

 * \param[in] ... Argument list

 * \return Base64 encoded string

 *

 * Encodes the string constructed by \p fmt and the arguments.

 * The encoded string is returned in an allocated buffer.

 *

 * You should free() the returned string when not needed any more.

 */

char *wget_base64_encode_printf_alloc(const char *fmt, ...)

{

  char *dst;

  va_list args;

  va_start(args, fmt);

  dst = wget_base64_encode_vprintf_alloc(fmt, args);

  va_end(args);

  return dst;

}

/**

 * \fn static inline size_t wget_base64_get_decoded_length(size_t len)

 * \param[in] len Length of base64 sequence

 * \return Number of decoded bytes plus one (for 0-byte termination)

 *

 * Calculate the number of bytes needed for decoding a base64 sequence with length \p len.

 */

size_t wget_base64_get_decoded_length(size_t len)

{

  return ((len + 3) / 4) * 3 + 1;

}

/**

 * \fn static inline size_t wget_base64_get_encoded_length(size_t len)

 * \param[in] len Number of (un-encoded) bytes

 * \return Length of base64 encoding plus one (for 0-byte termination)

 *

 * Calculate the number of bytes needed for base64 encoding a byte sequence with length \p len,

 * including the padding and 0-termination bytes.

 */

size_t wget_base64_get_encoded_length(size_t len)

{

  return ((len + 2) / 3) * 4 + 1;

}

/**@}*/