base64.c

/*
 * Base64 encoding/decoding (RFC1341)
 * Copyright (c) 2005-2011, Jouni Malinen <j@w1.fi>
 * Modified by Dormando
 *
 * This software may be distributed under the terms of the BSD license.
 * Original license included below:
 *
License
-------

This software may be distributed, used, and modified under the terms of
BSD license:

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

3. Neither the name(s) of the above-listed copyright holder(s) nor the
   names of its contributors may be used to endorse or promote products
   derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/* Changes from original code:
 * - decode table is pre-generated
 * - no line splitting on encoder
 * - output buffers are passed in instead of malloc'ed
 * - returns encoded/decoded length instead of pointer.
 */

#include <stddef.h>
#include "base64.h"

static const unsigned char base64_table[65] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

/* Original decode function generated the table every time. I used the code to
 * print this table and pre-generate it instead.
 */
static const unsigned char dtable[256] = {
128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
62, 128, 128, 128, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60,
61, 128, 128, 128, 0, 128, 128, 128, 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, 128, 128, 128, 128, 128, 128, 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, 128, 128, 128, 128,
128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
128, 128, 128
};

/**
 * base64_encode - Base64 encode
 * @src: Data to be encoded
 * @len: Length of the data to be encoded
 * @out: output uffer
 * @out_len: length of output buffer
 * Returns: Number of actual bytes encoded into the buffer
 * or 0 on failure
 *
 * Output buffer is nul terminated to make it easier to use as a C string.
 * The nul terminator is * not included in the return length.
 */
size_t base64_encode(const unsigned char *src, size_t len,
                  unsigned char *out, size_t out_len)
{
    unsigned char *pos;
    const unsigned char *end, *in;
    size_t olen;

    olen = len * 4 / 3 + 4; /* 3-byte blocks to 4-byte */
    olen += olen / 72; /* line feeds */
    olen++; /* nul termination */
    if (olen < len) {
        return 0; /* integer overflow */
    }
    if (olen > out_len) {
        return 0; /* not enough space in output buffer */
    }
    if (out == NULL) {
        return 0;
    }

    end = src + len;
    in = src;
    pos = out;
    while (end - in >= 3) {
        *pos++ = base64_table[in[0] >> 2];
        *pos++ = base64_table[((in[0] & 0x03) << 4) | (in[1] >> 4)];
        *pos++ = base64_table[((in[1] & 0x0f) << 2) | (in[2] >> 6)];
        *pos++ = base64_table[in[2] & 0x3f];
        in += 3;
    }

    if (end - in) {
        *pos++ = base64_table[in[0] >> 2];
        if (end - in == 1) {
            *pos++ = base64_table[(in[0] & 0x03) << 4];
            *pos++ = '=';
        } else {
            *pos++ = base64_table[((in[0] & 0x03) << 4) |
                          (in[1] >> 4)];
            *pos++ = base64_table[(in[1] & 0x0f) << 2];
        }
        *pos++ = '=';
    }

    *pos = '\0';
    return pos - out;
}


/**
 * base64_decode - Base64 decode
 * @src: Data to be decoded
 * @len: Length of the data to be decoded
 * @out: Output buffer to decode into
 * @out_len: Length of output buffer
 * Returns: Length of encoded data, or 0 on failure
 */
size_t base64_decode(const unsigned char *src, size_t len,
                  unsigned char *out, size_t out_len)
{
    unsigned char *pos, block[4], tmp;
    size_t i, count, olen;
    int pad = 0;

    count = 0;
    for (i = 0; i < len; i++) {
        if (dtable[src[i]] != 0x80)
            count++;
    }

    if (count == 0 || count % 4)
        return 0;

    olen = count / 4 * 3;
    if (olen > out_len) {
        return 0;
    }
    pos = out;
    if (out == NULL) {
        return 0;
    }

    count = 0;
    for (i = 0; i < len; i++) {
        tmp = dtable[src[i]];
        if (tmp == 0x80)
            continue;

        if (src[i] == '=')
            pad++;
        block[count] = tmp;
        count++;
        if (count == 4) {
            *pos++ = (block[0] << 2) | (block[1] >> 4);
            *pos++ = (block[1] << 4) | (block[2] >> 2);
            *pos++ = (block[2] << 6) | block[3];
            count = 0;
            if (pad) {
                if (pad == 1)
                    pos--;
                else if (pad == 2)
                    pos -= 2;
                else {
                    /* Invalid padding */
                    return 0;
                }
                break;
            }
        }
    }

    return pos - out;
}