1121cd29b6
Document what each local variable does when it isn't obvious from the name. Don't reuse a variable for different purposes. This commit has very little impact on the generated code (same code size on a sample Thumb build), although it does fix a theoretical bug that 2^32 spaces inside a line would be ignored instead of treated as an error. Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
402 lines
11 KiB
C
402 lines
11 KiB
C
/*
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* RFC 1521 base64 encoding/decoding
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "common.h"
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#if defined(MBEDTLS_BASE64_C)
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#include "mbedtls/base64.h"
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#include <stdint.h>
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#if defined(MBEDTLS_SELF_TEST)
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#include <string.h>
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#if defined(MBEDTLS_PLATFORM_C)
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#include "mbedtls/platform.h"
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#else
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#include <stdio.h>
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#define mbedtls_printf printf
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#endif /* MBEDTLS_PLATFORM_C */
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#endif /* MBEDTLS_SELF_TEST */
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static const unsigned char base64_enc_map[64] =
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{
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'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
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'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
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'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
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'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
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'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
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'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
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'8', '9', '+', '/'
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};
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#define BASE64_SIZE_T_MAX ( (size_t) -1 ) /* SIZE_T_MAX is not standard */
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/*
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* Constant flow conditional assignment to unsigned char
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*/
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static void mbedtls_base64_cond_assign_uchar( unsigned char * dest, const unsigned char * const src,
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unsigned char condition )
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{
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/* MSVC has a warning about unary minus on unsigned integer types,
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* but this is well-defined and precisely what we want to do here. */
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#if defined(_MSC_VER)
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#pragma warning( push )
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#pragma warning( disable : 4146 )
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#endif
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/* Generate bitmask from condition, mask will either be 0xFF or 0 */
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unsigned char mask = ( condition | -condition );
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mask >>= 7;
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mask = -mask;
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#if defined(_MSC_VER)
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#pragma warning( pop )
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#endif
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*dest = ( ( *src ) & mask ) | ( ( *dest ) & ~mask );
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}
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/*
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* Constant flow check for equality
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*/
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static unsigned char mbedtls_base64_eq( size_t in_a, size_t in_b )
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{
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size_t difference = in_a ^ in_b;
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/* MSVC has a warning about unary minus on unsigned integer types,
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* but this is well-defined and precisely what we want to do here. */
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#if defined(_MSC_VER)
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#pragma warning( push )
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#pragma warning( disable : 4146 )
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#endif
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difference |= -difference;
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#if defined(_MSC_VER)
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#pragma warning( pop )
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#endif
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/* cope with the varying size of size_t per platform */
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difference >>= ( sizeof( difference ) * 8 - 1 );
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return (unsigned char) ( 1 ^ difference );
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}
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/*
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* Constant flow lookup into table.
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*/
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static unsigned char mbedtls_base64_table_lookup( const unsigned char * const table,
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const size_t table_size, const size_t table_index )
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{
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size_t i;
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unsigned char result = 0;
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for( i = 0; i < table_size; ++i )
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{
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mbedtls_base64_cond_assign_uchar( &result, &table[i], mbedtls_base64_eq( i, table_index ) );
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}
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return result;
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}
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/* Return 0xff if low <= c <= high, 0 otherwise.
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*
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* Constant flow with respect to c.
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*/
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static unsigned char mask_of_range( unsigned char low, unsigned char high,
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unsigned char c )
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{
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unsigned low_mask = ( c - low ) >> 8;
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unsigned high_mask = ( c - high - 1 ) >> 8;
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return( ~low_mask & high_mask & 0xff );
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}
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/*
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* Encode a buffer into base64 format
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*/
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int mbedtls_base64_encode( unsigned char *dst, size_t dlen, size_t *olen,
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const unsigned char *src, size_t slen )
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{
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size_t i, n;
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int C1, C2, C3;
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unsigned char *p;
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if( slen == 0 )
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{
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*olen = 0;
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return( 0 );
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}
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n = slen / 3 + ( slen % 3 != 0 );
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if( n > ( BASE64_SIZE_T_MAX - 1 ) / 4 )
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{
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*olen = BASE64_SIZE_T_MAX;
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return( MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL );
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}
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n *= 4;
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if( ( dlen < n + 1 ) || ( NULL == dst ) )
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{
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*olen = n + 1;
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return( MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL );
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}
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n = ( slen / 3 ) * 3;
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for( i = 0, p = dst; i < n; i += 3 )
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{
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C1 = *src++;
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C2 = *src++;
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C3 = *src++;
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*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
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( ( C1 >> 2 ) & 0x3F ) );
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*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
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( ( ( ( C1 & 3 ) << 4 ) + ( C2 >> 4 ) ) & 0x3F ) );
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*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
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( ( ( ( C2 & 15 ) << 2 ) + ( C3 >> 6 ) ) & 0x3F ) );
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*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
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( C3 & 0x3F ) );
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}
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if( i < slen )
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{
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C1 = *src++;
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C2 = ( ( i + 1 ) < slen ) ? *src++ : 0;
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*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
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( ( C1 >> 2 ) & 0x3F ) );
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*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
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( ( ( ( C1 & 3 ) << 4 ) + ( C2 >> 4 ) ) & 0x3F ) );
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if( ( i + 1 ) < slen )
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*p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
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( ( ( C2 & 15 ) << 2 ) & 0x3F ) );
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else *p++ = '=';
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*p++ = '=';
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}
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*olen = p - dst;
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*p = 0;
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return( 0 );
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}
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/* Given a Base64 digit, return its value.
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* If c is not a Base64 digit ('A'..'Z', 'a'..'z', '0'..'9', '+' or '/'),
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* return -1.
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*
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* The implementation assumes that letters are consecutive (e.g. ASCII
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* but not EBCDIC).
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*
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* The implementation is constant-flow (no branch or memory access depending
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* on the value of c) unless the compiler inlines and optimizes a specific
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* access.
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*/
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static signed char dec_value( unsigned char c )
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{
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unsigned char val = 0;
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/* For each range of digits, if c is in that range, mask val with
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* the corresponding value. Since c can only be in a single range,
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* only at most one masking will change val. Set val to one plus
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* the desired value so that it stays 0 if c is in none of the ranges. */
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val |= mask_of_range( 'A', 'Z', c ) & ( c - 'A' + 0 + 1 );
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val |= mask_of_range( 'a', 'z', c ) & ( c - 'a' + 26 + 1 );
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val |= mask_of_range( '0', '9', c ) & ( c - '0' + 52 + 1 );
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val |= mask_of_range( '+', '+', c ) & ( c - '+' + 62 + 1 );
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val |= mask_of_range( '/', '/', c ) & ( c - '/' + 63 + 1 );
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/* At this point, val is 0 if c is an invalid digit and v+1 if c is
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* a digit with the value v. */
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return( val - 1 );
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}
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/*
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* Decode a base64-formatted buffer
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*/
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int mbedtls_base64_decode( unsigned char *dst, size_t dlen, size_t *olen,
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const unsigned char *src, size_t slen )
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{
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size_t i; /* index in source */
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size_t n; /* number of digits or trailing = in source */
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uint32_t x; /* value accumulator */
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unsigned equals = 0;
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int spaces_present = 0;
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unsigned char *p;
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/* First pass: check for validity and get output length */
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for( i = n = 0; i < slen; i++ )
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{
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/* Skip spaces before checking for EOL */
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spaces_present = 0;
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while( i < slen && src[i] == ' ' )
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{
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++i;
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spaces_present = 1;
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}
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/* Spaces at end of buffer are OK */
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if( i == slen )
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break;
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if( ( slen - i ) >= 2 &&
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src[i] == '\r' && src[i + 1] == '\n' )
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continue;
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if( src[i] == '\n' )
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continue;
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/* Space inside a line is an error */
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if( spaces_present )
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return( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
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if( src[i] > 127 )
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return( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
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if( src[i] == '=' )
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{
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if( ++equals > 2 )
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return( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
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}
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else
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{
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if( equals != 0 )
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return( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
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if( dec_value( src[i] ) < 0 )
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return( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
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}
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n++;
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}
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if( n == 0 )
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{
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*olen = 0;
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return( 0 );
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}
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/* The following expression is to calculate the following formula without
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* risk of integer overflow in n:
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* n = ( ( n * 6 ) + 7 ) >> 3;
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*/
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n = ( 6 * ( n >> 3 ) ) + ( ( 6 * ( n & 0x7 ) + 7 ) >> 3 );
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n -= equals;
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if( dst == NULL || dlen < n )
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{
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*olen = n;
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return( MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL );
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}
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equals = 0;
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for( n = x = 0, p = dst; i > 0; i--, src++ )
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{
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if( *src == '\r' || *src == '\n' || *src == ' ' )
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continue;
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x = x << 6;
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if( *src == '=' )
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++equals;
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else
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x |= dec_value( *src );
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if( ++n == 4 )
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{
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n = 0;
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*p++ = MBEDTLS_BYTE_2( x );
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if( equals <= 1 ) *p++ = MBEDTLS_BYTE_1( x );
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if( equals <= 0 ) *p++ = MBEDTLS_BYTE_0( x );
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}
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}
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*olen = p - dst;
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return( 0 );
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}
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#if defined(MBEDTLS_SELF_TEST)
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static const unsigned char base64_test_dec[64] =
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{
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0x24, 0x48, 0x6E, 0x56, 0x87, 0x62, 0x5A, 0xBD,
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0xBF, 0x17, 0xD9, 0xA2, 0xC4, 0x17, 0x1A, 0x01,
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0x94, 0xED, 0x8F, 0x1E, 0x11, 0xB3, 0xD7, 0x09,
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0x0C, 0xB6, 0xE9, 0x10, 0x6F, 0x22, 0xEE, 0x13,
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0xCA, 0xB3, 0x07, 0x05, 0x76, 0xC9, 0xFA, 0x31,
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0x6C, 0x08, 0x34, 0xFF, 0x8D, 0xC2, 0x6C, 0x38,
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0x00, 0x43, 0xE9, 0x54, 0x97, 0xAF, 0x50, 0x4B,
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0xD1, 0x41, 0xBA, 0x95, 0x31, 0x5A, 0x0B, 0x97
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};
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static const unsigned char base64_test_enc[] =
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"JEhuVodiWr2/F9mixBcaAZTtjx4Rs9cJDLbpEG8i7hPK"
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"swcFdsn6MWwINP+Nwmw4AEPpVJevUEvRQbqVMVoLlw==";
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/*
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* Checkup routine
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*/
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int mbedtls_base64_self_test( int verbose )
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{
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size_t len;
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const unsigned char *src;
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unsigned char buffer[128];
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if( verbose != 0 )
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mbedtls_printf( " Base64 encoding test: " );
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src = base64_test_dec;
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if( mbedtls_base64_encode( buffer, sizeof( buffer ), &len, src, 64 ) != 0 ||
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memcmp( base64_test_enc, buffer, 88 ) != 0 )
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{
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if( verbose != 0 )
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mbedtls_printf( "failed\n" );
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return( 1 );
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}
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if( verbose != 0 )
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mbedtls_printf( "passed\n Base64 decoding test: " );
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src = base64_test_enc;
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if( mbedtls_base64_decode( buffer, sizeof( buffer ), &len, src, 88 ) != 0 ||
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memcmp( base64_test_dec, buffer, 64 ) != 0 )
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{
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if( verbose != 0 )
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mbedtls_printf( "failed\n" );
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return( 1 );
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}
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if( verbose != 0 )
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mbedtls_printf( "passed\n\n" );
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return( 0 );
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}
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#endif /* MBEDTLS_SELF_TEST */
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#endif /* MBEDTLS_BASE64_C */
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