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mbedtls/library/base64.c
Paul Elliott 6f69d4c7e2 Remove multiplication from conditional assignments 
Multiplication is not constant flow on any CPU we are generally
targetting, so replace this with bit twiddling.

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
2021-03-04 14:08:13 +00:00

425 lines
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C
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/*
* RFC 1521 base64 encoding/decoding
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*
* This file is provided under the Apache License 2.0, or the
* GNU General Public License v2.0 or later.
*
* **********
* Apache License 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.
*
* **********
*
* **********
* GNU General Public License v2.0 or later:
*
* 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.
*
* **********
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_BASE64_C)
#include "mbedtls/base64.h"
#include <stdint.h>
#if defined(MBEDTLS_SELF_TEST)
#include <string.h>
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdio.h>
#define mbedtls_printf printf
#endif /* MBEDTLS_PLATFORM_C */
#endif /* MBEDTLS_SELF_TEST */
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 */
/*
* Constant flow conditional assignment to unsigned char
*/
static void mbedtls_base64_cond_assign_uchar(unsigned char * dest, const unsigned char * const src,
unsigned char condition)
{
/* MSVC has a warning about unary minus on unsigned integer types,
* but this is well-defined and precisely what we want to do here. */
#if defined(_MSC_VER)
#pragma warning( push )
#pragma warning( disable : 4146 )
#endif
/* Generate bitmask from condition, mask will either be 0xFFFFFFFF or 0 */
unsigned char mask = -( unsigned char )( ( condition | -condition ) >> 7 );
#if defined(_MSC_VER)
#pragma warning( pop )
#endif
*dest = ( ( *src ) & mask ) | ( ( *dest ) & ~mask );
}
/*
* Constant flow conditional assignment to uint_32
*/
static void mbedtls_base64_cond_assign_uint32(uint32_t * dest, const uint32_t src,
uint32_t condition)
{
/* MSVC has a warning about unary minus on unsigned integer types,
* but this is well-defined and precisely what we want to do here. */
#if defined(_MSC_VER)
#pragma warning( push )
#pragma warning( disable : 4146 )
#endif
/* Generate bitmask from condition, mask will either be 0xFFFFFFFF or 0 */
uint32_t mask = -( uint32_t )( ( condition | -condition ) >> 31 );
#if defined(_MSC_VER)
#pragma warning( pop )
#endif
*dest = ( src & mask ) | ( ( *dest ) & ~mask );
}
/*
* Constant flow check for equality
*/
static unsigned char mbedtls_base64_eq(size_t in_a, size_t in_b)
{
size_t difference = in_a ^ in_b;
/* MSVC has a warning about unary minus on unsigned integer types,
* but this is well-defined and precisely what we want to do here. */
#if defined(_MSC_VER)
#pragma warning( push )
#pragma warning( disable : 4146 )
#endif
difference |= -difference;
#if defined(_MSC_VER)
#pragma warning( pop )
#endif
/* cope with the varying size of size_t per platform */
difference >>= ( sizeof( difference ) * 8 - 1 );
return (unsigned char) ( 1 ^ difference );
}
/*
* Constant flow lookup into table.
*/
static unsigned char mbedtls_base64_table_lookup(const unsigned char * const table,
const size_t table_size, const size_t table_index)
{
size_t i;
unsigned char result = 0;
for( i = 0; i < table_size; ++i )
{
mbedtls_base64_cond_assign_uchar(&result, &table[i], mbedtls_base64_eq(i, table_index));
}
return result;
}
/*
* Encode a buffer into base64 format
*/
int mbedtls_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( MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL );
}
n *= 4;
if( ( dlen < n + 1 ) || ( NULL == dst ) )
{
*olen = n + 1;
return( MBEDTLS_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++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
( ( C1 >> 2 ) & 0x3F ) );
*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
( ( ( ( C1 & 3 ) << 4 ) + ( C2 >> 4 ) ) & 0x3F ) );
*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
( ( ( ( C2 & 15 ) << 2 ) + ( C3 >> 6 ) ) & 0x3F ) );
*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
( C3 & 0x3F ) );
}
if( i < slen )
{
C1 = *src++;
C2 = ( ( i + 1 ) < slen ) ? *src++ : 0;
*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
( ( C1 >> 2 ) & 0x3F ) );
*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
( ( ( ( C1 & 3 ) << 4 ) + ( C2 >> 4 ) ) & 0x3F ) );
if( ( i + 1 ) < slen )
*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
( ( ( C2 & 15 ) << 2 ) & 0x3F ) );
else *p++ = '=';
*p++ = '=';
}
*olen = p - dst;
*p = 0;
return( 0 );
}
/*
* Decode a base64-formatted buffer
*/
int mbedtls_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;
unsigned char dec_map_lookup;
/* 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( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
if( src[i] == '=' && ++j > 2 )
return( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
dec_map_lookup = mbedtls_base64_table_lookup( base64_dec_map, sizeof( base64_dec_map ), src[i] );
if( src[i] > 127 || dec_map_lookup == 127 )
return( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
if( dec_map_lookup < 64 && j != 0 )
return( MBEDTLS_ERR_BASE64_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( MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL );
}
for( j = 3, n = x = 0, p = dst; i > 0; i--, src++ )
{
if( *src == '\r' || *src == '\n' || *src == ' ' )
continue;
dec_map_lookup = mbedtls_base64_table_lookup(base64_dec_map, sizeof( base64_dec_map ), *src );
mbedtls_base64_cond_assign_uint32( &j, j - 1, mbedtls_base64_eq( dec_map_lookup, 64 ) );
x = ( x << 6 ) | ( dec_map_lookup & 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 );
}
#if defined(MBEDTLS_SELF_TEST)
static const unsigned char base64_test_dec[64] =
{
0x24, 0x48, 0x6E, 0x56, 0x87, 0x62, 0x5A, 0xBD,
0xBF, 0x17, 0xD9, 0xA2, 0xC4, 0x17, 0x1A, 0x01,
0x94, 0xED, 0x8F, 0x1E, 0x11, 0xB3, 0xD7, 0x09,
0x0C, 0xB6, 0xE9, 0x10, 0x6F, 0x22, 0xEE, 0x13,
0xCA, 0xB3, 0x07, 0x05, 0x76, 0xC9, 0xFA, 0x31,
0x6C, 0x08, 0x34, 0xFF, 0x8D, 0xC2, 0x6C, 0x38,
0x00, 0x43, 0xE9, 0x54, 0x97, 0xAF, 0x50, 0x4B,
0xD1, 0x41, 0xBA, 0x95, 0x31, 0x5A, 0x0B, 0x97
};
static const unsigned char base64_test_enc[] =
"JEhuVodiWr2/F9mixBcaAZTtjx4Rs9cJDLbpEG8i7hPK"
"swcFdsn6MWwINP+Nwmw4AEPpVJevUEvRQbqVMVoLlw==";
/*
* Checkup routine
*/
int mbedtls_base64_self_test( int verbose )
{
size_t len;
const unsigned char *src;
unsigned char buffer[128];
if( verbose != 0 )
mbedtls_printf( " Base64 encoding test: " );
src = base64_test_dec;
if( mbedtls_base64_encode( buffer, sizeof( buffer ), &len, src, 64 ) != 0 ||
memcmp( base64_test_enc, buffer, 88 ) != 0 )
{
if( verbose != 0 )
mbedtls_printf( "failed\n" );
return( 1 );
}
if( verbose != 0 )
mbedtls_printf( "passed\n Base64 decoding test: " );
src = base64_test_enc;
if( mbedtls_base64_decode( buffer, sizeof( buffer ), &len, src, 88 ) != 0 ||
memcmp( base64_test_dec, buffer, 64 ) != 0 )
{
if( verbose != 0 )
mbedtls_printf( "failed\n" );
return( 1 );
}
if( verbose != 0 )
mbedtls_printf( "passed\n\n" );
return( 0 );
}
#endif /* MBEDTLS_SELF_TEST */
#endif /* MBEDTLS_BASE64_C */
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