src/core/base64.c

   1 /*
   2  * Copyright (C) 2009 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 FILE_LICENCE ( GPL2_OR_LATER );
  20
  21 #include <stdint.h>
  22 #include <string.h>
  23 #include <ctype.h>
  24 #include <errno.h>
  25 #include <assert.h>
  26 #include <gpxe/base64.h>
  27
  28 /** @file
  29  *
  30  * Base64 encoding
  31  *
  32  */
  33
  34 static const char base64[64] =
  35         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  36
  37 /**
  38  * Base64-encode data
  39  *
  40  * @v raw               Raw data
  41  * @v len               Length of raw data
  42  * @v encoded           Buffer for encoded string
  43  *
  44  * The buffer must be the correct length for the encoded string.  Use
  45  * something like
  46  *
  47  *     char buf[ base64_encoded_len ( len ) + 1 ];
  48  *
  49  * (the +1 is for the terminating NUL) to provide a buffer of the
  50  * correct size.
  51  */
  52 void base64_encode ( const uint8_t *raw, size_t len, char *encoded ) {
  53         const uint8_t *raw_bytes = ( ( const uint8_t * ) raw );
  54         uint8_t *encoded_bytes = ( ( uint8_t * ) encoded );
  55         size_t raw_bit_len = ( 8 * len );
  56         unsigned int bit;
  57         unsigned int tmp;
  58
  59         for ( bit = 0 ; bit < raw_bit_len ; bit += 6 ) {
  60                 tmp = ( ( raw_bytes[ bit / 8 ] << ( bit % 8 ) ) |
  61                         ( raw_bytes[ bit / 8 + 1 ] >> ( 8 - ( bit % 8 ) ) ) );
  62                 tmp = ( ( tmp >> 2 ) & 0x3f );
  63                 *(encoded_bytes++) = base64[tmp];
  64         }
  65         for ( ; ( bit % 8 ) != 0 ; bit += 6 )
  66                 *(encoded_bytes++) = '=';
  67         *(encoded_bytes++) = '\0';
  68
  69         DBG ( "Base64-encoded to \"%s\":\n", encoded );
  70         DBG_HDA ( 0, raw, len );
  71         assert ( strlen ( encoded ) == base64_encoded_len ( len ) );
  72 }
  73
  74 /**
  75  * Base64-decode string
  76  *
  77  * @v encoded           Encoded string
  78  * @v raw               Raw data
  79  * @ret len             Length of raw data, or negative error
  80  *
  81  * The buffer must be large enough to contain the decoded data.  Use
  82  * something like
  83  *
  84  *     char buf[ base64_decoded_max_len ( encoded ) ];
  85  *
  86  * to provide a buffer of the correct size.
  87  */
  88 int base64_decode ( const char *encoded, uint8_t *raw ) {
  89         const uint8_t *encoded_bytes = ( ( const uint8_t * ) encoded );
  90         uint8_t *raw_bytes = ( ( uint8_t * ) raw );
  91         uint8_t encoded_byte;
  92         char *match;
  93         int decoded;
  94         unsigned int bit = 0;
  95         unsigned int pad_count = 0;
  96         size_t len;
  97
  98         /* Zero the raw data */
  99         memset ( raw, 0, base64_decoded_max_len ( encoded ) );
 100
 101         /* Decode string */
 102         while ( ( encoded_byte = *(encoded_bytes++) ) ) {
 103
 104                 /* Ignore whitespace characters */
 105                 if ( isspace ( encoded_byte ) )
 106                         continue;
 107
 108                 /* Process pad characters */
 109                 if ( encoded_byte == '=' ) {
 110                         if ( pad_count >= 2 ) {
 111                                 DBG ( "Base64-encoded string \"%s\" has too "
 112                                       "many pad characters\n", encoded );
 113                                 return -EINVAL;
 114                         }
 115                         pad_count++;
 116                         bit -= 2; /* unused_bits = ( 2 * pad_count ) */
 117                         continue;
 118                 }
 119                 if ( pad_count ) {
 120                         DBG ( "Base64-encoded string \"%s\" has invalid pad "
 121                               "sequence\n", encoded );
 122                         return -EINVAL;
 123                 }
 124
 125                 /* Process normal characters */
 126                 match = strchr ( base64, encoded_byte );
 127                 if ( ! match ) {
 128                         DBG ( "Base64-encoded string \"%s\" contains invalid "
 129                               "character '%c'\n", encoded, encoded_byte );
 130                         return -EINVAL;
 131                 }
 132                 decoded = ( match - base64 );
 133
 134                 /* Add to raw data */
 135                 decoded <<= 2;
 136                 raw_bytes[ bit / 8 ] |= ( decoded >> ( bit % 8 ) );
 137                 raw_bytes[ bit / 8 + 1 ] |= ( decoded << ( 8 - ( bit % 8 ) ) );
 138                 bit += 6;
 139         }
 140
 141         /* Check that we decoded a whole number of bytes */
 142         if ( ( bit % 8 ) != 0 ) {
 143                 DBG ( "Base64-encoded string \"%s\" has invalid bit length "
 144                       "%d\n", encoded, bit );
 145                 return -EINVAL;
 146         }
 147         len = ( bit / 8 );
 148
 149         DBG ( "Base64-decoded \"%s\" to:\n", encoded );
 150         DBG_HDA ( 0, raw, len );
 151         assert ( len <= base64_decoded_max_len ( encoded ) );
 152
 153         /* Return length in bytes */
 154         return ( len );
 155 }