/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

/*  Fluent Bit

 *  ==========

 *  Copyright (C) 2019-2021 The Fluent Bit Authors

 *

 *  Licensed under the Apache License, Version 2.0 (the "License");

 *  you may not use this file except in compliance with the License.

 *  You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 *  Unless required by applicable law or agreed to in writing, software

 *  distributed under the License is distributed on an "AS IS" BASIS,

 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 *  See the License for the specific language governing permissions and

 *  limitations under the License.

 */

/* This code is based on base64.c from the mbedtls-2.25.0 Library distribution,

 * as originally written by Paul Bakker, et al., and forked by the Fluent Bit

 * project to provide performant base64 encoding and decoding routines.

 * The 2.25.0 implementation is included rather than 2.26.0+ implementation due

 * to performance degradation introduced in 2.26.0.

 *

 * Method and variable names are changed by the Fluent Bit authors to maintain

 * consistency with the Fluent Bit project.

 * The self test section of the code was removed by the Fluent Bit authors.

 * Other minor changes are made by the Fluent Bit authors.

 *

 * The original source file base64.c is copyright and licensed as follows;

 *

 *  RFC 1521 base64 encoding/decoding

 *

 *  Copyright The Mbed TLS Contributors

 *  SPDX-License-Identifier: Apache-2.0

 *

 *  Licensed under the Apache License, Version 2.0 (the "License"); you may

 *  not use this file except in compliance with the License.

 *  You may obtain a copy of the License at

 *

 *  http://www.apache.org/licenses/LICENSE-2.0

 *

 *  Unless required by applicable law or agreed to in writing, software

 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT

 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 *  See the License for the specific language governing permissions and

 *  limitations under the License.

 */

#include <fluent-bit/flb_base64.h>

#include <stdint.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

};

#define BASE64_SIZE_T_MAX   ( (size_t) -1 ) /* SIZE_T_MAX is not standard */

/*

 * Encode a buffer into base64 format

 */

int flb_base64_encode( unsigned char *dst, size_t dlen, size_t *olen,

                   const unsigned char *src, size_t slen )

{

    size_t i, n;

    int C1, C2, C3;

    unsigned char *p;

    if( slen == 0 )

    {

        *olen = 0;

        return( 0 );

    }

    n = slen / 3 + ( slen % 3 != 0 );

    if( n > ( BASE64_SIZE_T_MAX - 1 ) / 4 )

    {

        *olen = BASE64_SIZE_T_MAX;

        return( FLB_BASE64_ERR_BUFFER_TOO_SMALL );

    }

    n *= 4;

    if( ( dlen < n + 1 ) || ( NULL == dst ) )

    {

        *olen = n + 1;

        return( FLB_BASE64_ERR_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++ = '=';

    }

    *olen = p - dst;

    *p = 0;

    return( 0 );

}

/*

 * Decode a base64-formatted buffer

 */

int flb_base64_decode( unsigned char *dst, size_t dlen, size_t *olen,

                   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( FLB_BASE64_ERR_INVALID_CHARACTER );

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

            return( FLB_BASE64_ERR_INVALID_CHARACTER );

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

            return( FLB_BASE64_ERR_INVALID_CHARACTER );

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

            return( FLB_BASE64_ERR_INVALID_CHARACTER );

        n++;

    }

    if( n == 0 )

    {

        *olen = 0;

        return( 0 );

    }

    /* The following expression is to calculate the following formula without

     * risk of integer overflow in n:

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

     */

    n = ( 6 * ( n >> 3 ) ) + ( ( 6 * ( n & 0x7 ) + 7 ) >> 3 );

    n -= j;

    if( dst == NULL || dlen < n )

    {

        *olen = n;

        return( FLB_BASE64_ERR_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       );

        }

    }

    *olen = p - dst;

    return( 0 );

}