/*
 *  RFC 1521 base64 encoding/decoding
 *
 *  Copyright (C) 2006-2014, Brainspark B.V.
 *
 *  This file is part of PolarSSL (http://www.polarssl.org)
 *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
 *
 *  All rights reserved.
 *
 *  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 2 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, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "base64.h"

static const unsigned char base64_enc_map[64] = {
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
    'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
    'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
};

static const unsigned char base64_dec_map[128] = {
    127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
    127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
    127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 62,  127,
    127, 127, 63,  52,  53,  54,  55,  56,  57,  58,  59,  60,  61,  127, 127,
    127, 64,  127, 127, 127, 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,  127, 127, 127, 127, 127, 127, 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,  127, 127, 127, 127, 127
};

/*
 * Encode a buffer into base64 format
 */
int
b64_encode(
    unsigned char* dst,
    size_t* dlen,
    const unsigned char* src,
    size_t slen)
{
    size_t i, n;
    int C1, C2, C3;
    unsigned char* p;

    if (slen == 0) return (0);

    n = (slen << 3) / 6;

    switch ((slen << 3) - (n * 6)) {
        case 2: n += 3; break;
        case 4: n += 2; break;
        default: break;
    }

    if (*dlen < n + 1) {
        *dlen = n + 1;
        return (POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL);
    }

    n = (slen / 3) * 3;

    for (i = 0, p = dst; i < n; i += 3) {
        C1 = *src++;
        C2 = *src++;
        C3 = *src++;

        *p++ = base64_enc_map[(C1 >> 2) & 0x3F];
        *p++ = base64_enc_map[(((C1 & 3) << 4) + (C2 >> 4)) & 0x3F];
        *p++ = base64_enc_map[(((C2 & 15) << 2) + (C3 >> 6)) & 0x3F];
        *p++ = base64_enc_map[C3 & 0x3F];
    }

    if (i < slen) {
        C1 = *src++;
        C2 = ((i + 1) < slen) ? *src++ : 0;

        *p++ = base64_enc_map[(C1 >> 2) & 0x3F];
        *p++ = base64_enc_map[(((C1 & 3) << 4) + (C2 >> 4)) & 0x3F];

        if ((i + 1) < slen)
            *p++ = base64_enc_map[((C2 & 15) << 2) & 0x3F];
        else
            *p++ = '=';

        *p++ = '=';
    }

    *dlen = p - dst;
    *p = 0;

    return (0);
}

/*
 * Decode a base64-formatted buffer
 */
int
b64_decode(
    unsigned char* dst,
    size_t* dlen,
    const unsigned char* src,
    size_t slen)
{
    size_t i, n;
    uint32_t j, x;
    unsigned char* p;

    /* First pass: check for validity and get output length */
    for (i = n = j = 0; i < slen; i++) {
        /* Skip spaces before checking for EOL */
        x = 0;
        while (i < slen && src[i] == ' ') {
            ++i;
            ++x;
        }

        /* Spaces at end of buffer are OK */
        if (i == slen) break;

        if ((slen - i) >= 2 && src[i] == '\r' && src[i + 1] == '\n') continue;

        if (src[i] == '\n') continue;

        /* Space inside a line is an error */
        if (x != 0) return (POLARSSL_ERR_BASE64_INVALID_CHARACTER);

        if (src[i] == '=' && ++j > 2)
            return (POLARSSL_ERR_BASE64_INVALID_CHARACTER);

        if (src[i] > 127 || base64_dec_map[src[i]] == 127)
            return (POLARSSL_ERR_BASE64_INVALID_CHARACTER);

        if (base64_dec_map[src[i]] < 64 && j != 0)
            return (POLARSSL_ERR_BASE64_INVALID_CHARACTER);

        n++;
    }

    if (n == 0) return (0);

    n = ((n * 6) + 7) >> 3;
    n -= j;

    if (dst == NULL || *dlen < n) {
        *dlen = n;
        return (POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL);
    }

    for (j = 3, n = x = 0, p = dst; i > 0; i--, src++) {
        if (*src == '\r' || *src == '\n' || *src == ' ') continue;

        j -= (base64_dec_map[*src] == 64);
        x = (x << 6) | (base64_dec_map[*src] & 0x3F);

        if (++n == 4) {
            n = 0;
            if (j > 0) *p++ = (unsigned char)(x >> 16);
            if (j > 1) *p++ = (unsigned char)(x >> 8);
            if (j > 2) *p++ = (unsigned char)(x);
        }
    }

    *dlen = p - dst;

    return (0);
}