base64.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file LICENSE, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the LICENSE file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * SPDX-License-Identifier: curl
 *
 ***************************************************************************/

// Modified for standalone inclusion in SimpleGraphic.

 /* Base64 encoding/decoding */

#include "base64.h"

#include <stdlib.h>
#include <string.h>

/* ---- Base64 Encoding/Decoding Table --- */
/* Padding character string starts at offset 64. */
static const char base64encdec[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

/* The Base 64 encoding with a URL and filename safe alphabet, RFC 4648
   section 5 */
static const char base64url[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";

static const unsigned char decodetable[] =
{ 62, 255, 255, 255, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255, 255,
  255, 255, 255, 255, 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, 255, 255, 255, 255, 255, 255, 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 };
/*
 * Base64Decode() n�e Curl_base64_decode()
 *
 * Given a base64 NUL-terminated string at src, decode it and return a
 * pointer in *outptr to a newly allocated memory area holding decoded
 * data. Size of decoded data is returned in variable pointed by outlen.
 *
 * Returns CURLE_OK on success, otherwise specific error code. Function
 * output shall not be considered valid unless CURLE_OK is returned.
 *
 * When decoded data length is 0, returns NULL in *outptr.
 *
 * @unittest: 1302
 */
bool Base64Decode(const char* src, unsigned char** outptr, size_t* outlen)
{
    size_t srclen = 0;
    size_t padding = 0;
    size_t i;
    size_t numQuantums;
    size_t fullQuantums;
    size_t rawlen = 0;
    unsigned char* pos;
    unsigned char* newstr;
    unsigned char lookup[256];

    *outptr = NULL;
    *outlen = 0;
    srclen = strlen(src);

    /* Check the length of the input string is valid */
    if (!srclen || srclen % 4)
        return false;

    /* srclen is at least 4 here */
    while (src[srclen - 1 - padding] == '=') {
        /* count padding characters */
        padding++;
        /* A maximum of two = padding characters is allowed */
        if (padding > 2)
            return false;
    }

    /* Calculate the number of quantums */
    numQuantums = srclen / 4;
    fullQuantums = numQuantums - (padding ? 1 : 0);

    /* Calculate the size of the decoded string */
    rawlen = (numQuantums * 3) - padding;

    /* Allocate our buffer including room for a null-terminator */
    newstr = malloc(rawlen + 1);
    if (!newstr)
        return false;

    pos = newstr;

    memset(lookup, 0xff, sizeof(lookup));
    memcpy(&lookup['+'], decodetable, sizeof(decodetable));
    /* replaces
    {
      unsigned char c;
      const unsigned char *p = (const unsigned char *)base64encdec;
      for(c = 0; *p; c++, p++)
        lookup[*p] = c;
    }
    */

    /* Decode the complete quantums first */
    for (i = 0; i < fullQuantums; i++) {
        unsigned char val;
        unsigned int x = 0;
        int j;

        for (j = 0; j < 4; j++) {
            val = lookup[(unsigned char)*src++];
            if (val == 0xff) /* bad symbol */
                goto bad;
            x = (x << 6) | val;
        }
        pos[2] = x & 0xff;
        pos[1] = (x >> 8) & 0xff;
        pos[0] = (x >> 16) & 0xff;
        pos += 3;
    }
    if (padding) {
        /* this means either 8 or 16 bits output */
        unsigned char val;
        unsigned int x = 0;
        int j;
        size_t padc = 0;
        for (j = 0; j < 4; j++) {
            if (*src == '=') {
                x <<= 6;
                src++;
                if (++padc > padding)
                    /* this is a badly placed '=' symbol! */
                    goto bad;
            }
            else {
                val = lookup[(unsigned char)*src++];
                if (val == 0xff) /* bad symbol */
                    goto bad;
                x = (x << 6) | val;
            }
        }
        if (padding == 1)
            pos[1] = (x >> 8) & 0xff;
        pos[0] = (x >> 16) & 0xff;
        pos += 3 - padding;
    }

    /* Zero terminate */
    *pos = '\0';

    /* Return the decoded data */
    *outptr = newstr;
    *outlen = rawlen;

    return true;
bad:
    free(newstr);
    return false;
}

static bool base64_encode(const char* table64,
    const char* inputbuff, size_t insize,
    char** outptr, size_t* outlen)
{
    char* output;
    char* base64data;
    const unsigned char* in = (unsigned char*)inputbuff;
    const char* padstr = &table64[64];    /* Point to padding string. */

    *outptr = NULL;
    *outlen = 0;

    if (!insize)
        insize = strlen(inputbuff);

#if SIZEOF_SIZE_T == 4
    if (insize > UINT_MAX / 4)
        return false;
#endif

    base64data = output = malloc((insize + 2) / 3 * 4 + 1);
    if (!output)
        return false;

    while (insize >= 3) {
        *output++ = table64[in[0] >> 2];
        *output++ = table64[((in[0] & 0x03) << 4) | (in[1] >> 4)];
        *output++ = table64[((in[1] & 0x0F) << 2) | ((in[2] & 0xC0) >> 6)];
        *output++ = table64[in[2] & 0x3F];
        insize -= 3;
        in += 3;
    }
    if (insize) {
        /* this is only one or two bytes now */
        *output++ = table64[in[0] >> 2];
        if (insize == 1) {
            *output++ = table64[((in[0] & 0x03) << 4)];
            if (*padstr) {
                *output++ = *padstr;
                *output++ = *padstr;
            }
        }
        else {
            /* insize == 2 */
            *output++ = table64[((in[0] & 0x03) << 4) | ((in[1] & 0xF0) >> 4)];
            *output++ = table64[((in[1] & 0x0F) << 2)];
            if (*padstr)
                *output++ = *padstr;
        }
    }

    /* Zero terminate */
    *output = '\0';

    /* Return the pointer to the new data (allocated memory) */
    *outptr = base64data;

    /* Return the length of the new data */
    *outlen = output - base64data;

    return true;
}

/*
 * Base64Encode() n�e Curl_base64_encode()
 *
 * Given a pointer to an input buffer and an input size, encode it and
 * return a pointer in *outptr to a newly allocated memory area holding
 * encoded data. Size of encoded data is returned in variable pointed by
 * outlen.
 *
 * Input length of 0 indicates input buffer holds a NUL-terminated string.
 *
 * Returns CURLE_OK on success, otherwise specific error code. Function
 * output shall not be considered valid unless CURLE_OK is returned.
 *
 * @unittest: 1302
 */
bool Base64Encode(const char* inputbuff, size_t insize,
    char** outptr, size_t* outlen)
{
    return base64_encode(base64encdec, inputbuff, insize, outptr, outlen);
}

/*
 * Base64UrlEncode() n�e Curl_base64url_encode()
 *
 * Given a pointer to an input buffer and an input size, encode it and
 * return a pointer in *outptr to a newly allocated memory area holding
 * encoded data. Size of encoded data is returned in variable pointed by
 * outlen.
 *
 * Input length of 0 indicates input buffer holds a NUL-terminated string.
 *
 * Returns CURLE_OK on success, otherwise specific error code. Function
 * output shall not be considered valid unless CURLE_OK is returned.
 *
 * @unittest: 1302
 */
bool Base64UrlEncode(const char* inputbuff, size_t insize,
    char** outptr, size_t* outlen)
{
    return base64_encode(base64url, inputbuff, insize, outptr, outlen);
}