base64.c

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/*
 * Copyright (C) 2009 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * 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 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.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdint.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <assert.h>
#include <ipxe/base64.h>

/** @file
 *
 * Base64 encoding
 *
 */

static const char base64[ 64 + 1 /* NUL */ ] =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

/**
 * Base64-encode data
 *
 * @v raw               Raw data
 * @v raw_len           Length of raw data
 * @v data              Buffer
 * @v len               Length of buffer
 * @ret len             Encoded length
 */
size_t base64_encode ( const void *raw, size_t raw_len, char *data,
                       size_t len ) {
        const uint8_t *raw_bytes = ( ( const uint8_t * ) raw );
        size_t raw_bit_len = ( 8 * raw_len );
        size_t used = 0;
        unsigned int bit;
        unsigned int byte;
        unsigned int shift;
        unsigned int tmp;

        for ( bit = 0 ; bit < raw_bit_len ; bit += 6, used++ ) {
                byte = ( bit / 8 );
                shift = ( bit % 8 );
                tmp = ( raw_bytes[byte] << shift );
                if ( ( byte + 1 ) < raw_len )
                        tmp |= ( raw_bytes[ byte + 1 ] >> ( 8 - shift ) );
                tmp = ( ( tmp >> 2 ) & 0x3f );
                if ( used < len )
                        data[used] = base64[tmp];
        }
        for ( ; ( bit % 8 ) != 0 ; bit += 6, used++ ) {
                if ( used < len )
                        data[used] = '=';
        }
        if ( used < len )
                data[used] = '\0';
        if ( len )
                data[ len - 1 ] = '\0'; /* Ensure terminator exists */

        return used;
}

/**
 * Base64-decode string
 *
 * @v encoded           Encoded string
 * @v data              Buffer
 * @v len               Length of buffer
 * @ret len             Length of data, or negative error
 */
int base64_decode ( const char *encoded, void *data, size_t len ) {
        const char *in = encoded;
        uint8_t *out = data;
        uint8_t in_char;
        char *match;
        int in_bits;
        unsigned int bit = 0;
        unsigned int pad_count = 0;
        size_t offset;

        /* Zero the output buffer */
        memset ( data, 0, len );

        /* Decode string */
        while ( ( in_char = *(in++) ) ) {

                /* Ignore whitespace characters */
                if ( isspace ( in_char ) )
                        continue;

                /* Process pad characters */
                if ( in_char == '=' ) {
                        if ( pad_count >= 2 ) {
                                DBG ( "Base64-encoded string \"%s\" has too "
                                      "many pad characters\n", encoded );
                                return -EINVAL;
                        }
                        pad_count++;
                        bit -= 2; /* unused_bits = ( 2 * pad_count ) */
                        continue;
                }
                if ( pad_count ) {
                        DBG ( "Base64-encoded string \"%s\" has invalid pad "
                              "sequence\n", encoded );
                        return -EINVAL;
                }

                /* Process normal characters */
                match = strchr ( base64, in_char );
                if ( ! match ) {
                        DBG ( "Base64-encoded string \"%s\" contains invalid "
                              "character '%c'\n", encoded, in_char );
                        return -EINVAL;
                }
                in_bits = ( match - base64 );

                /* Add to raw data */
                in_bits <<= 2;
                offset = ( bit / 8 );
                if ( offset < len )
                        out[offset] |= ( in_bits >> ( bit % 8 ) );
                offset++;
                if ( offset < len )
                        out[offset] |= ( in_bits << ( 8 - ( bit % 8 ) ) );
                bit += 6;
        }

        /* Check that we decoded a whole number of bytes */
        if ( ( bit % 8 ) != 0 ) {
                DBG ( "Base64-encoded string \"%s\" has invalid bit length "
                      "%d\n", encoded, bit );
                return -EINVAL;
        }

        /* Return length in bytes */
        return ( bit / 8 );
}