365 lines
10 KiB
C
365 lines
10 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 OR GPL-2.0-or-later
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*
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* This file is provided under the Apache License 2.0, or the
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* GNU General Public License v2.0 or later.
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*
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* **********
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* Apache License 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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* **********
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*
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* **********
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* GNU General Public License v2.0 or later:
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* **********
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*/
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#if !defined(MBEDTLS_CONFIG_FILE)
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#include "mbedtls/config.h"
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#else
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#include MBEDTLS_CONFIG_FILE
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#endif
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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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#define BASE64_SIZE_T_MAX ( (size_t) -1 ) /* SIZE_T_MAX is not standard */
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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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/* low_mask is: 0 if low <= c, 0x...ff if low > c */
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unsigned low_mask = ( (unsigned) c - low ) >> 8;
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/* high_mask is: 0 if c <= high, 0x...ff if c > high */
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unsigned high_mask = ( (unsigned) high - c ) >> 8;
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return( ~( low_mask | high_mask ) & 0xff );
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}
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/* Given a value in the range 0..63, return the corresponding Base64 digit.
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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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static unsigned char enc_char( unsigned char val )
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{
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unsigned char digit = 0;
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/* For each range of values, if val is in that range, mask digit with
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* the corresponding value. Since val can only be in a single range,
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* only at most one masking will change digit. */
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digit |= mask_of_range( 0, 25, val ) & ( 'A' + val );
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digit |= mask_of_range( 26, 51, val ) & ( 'a' + val - 26 );
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digit |= mask_of_range( 52, 61, val ) & ( '0' + val - 52 );
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digit |= mask_of_range( 62, 62, val ) & '+';
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digit |= mask_of_range( 63, 63, val ) & '/';
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return( digit );
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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++ = enc_char( ( C1 >> 2 ) & 0x3F );
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*p++ = enc_char( ( ( ( C1 & 3 ) << 4 ) + ( C2 >> 4 ) ) & 0x3F );
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*p++ = enc_char( ( ( ( C2 & 15 ) << 2 ) + ( C3 >> 6 ) ) & 0x3F );
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*p++ = enc_char( 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++ = enc_char( ( C1 >> 2 ) & 0x3F );
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*p++ = enc_char( ( ( ( C1 & 3 ) << 4 ) + ( C2 >> 4 ) ) & 0x3F );
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if( ( i + 1 ) < slen )
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*p++ = enc_char( ( ( 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 accumulated_digits = 0;
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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( 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( ++accumulated_digits == 4 )
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{
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accumulated_digits = 0;
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*p++ = (unsigned char)( x >> 16 );
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if( equals <= 1 ) *p++ = (unsigned char)( x >> 8 );
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if( equals <= 0 ) *p++ = (unsigned char)( 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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