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/*
* base64.c - support for base64 alphabet system, described in RFC1521
*
* This file is part of the SSH Library
*
* Copyright (c) 2005-2005 by Aris Adamantiadis
*
* The SSH Library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The SSH Library 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 Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the SSH Library; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*
* vim: ts=2 sw=2 et cindent
*/
/* just the dirtiest part of code i ever made */
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include "libssh/priv.h"
static char alphabet[]="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/" ;
/* transformations */
#define SET_A(n,i) do { n |= (i&63) <<18; } while (0)
#define SET_B(n,i) do { n |= (i&63) <<12; } while (0)
#define SET_C(n,i) do { n |= (i&63) << 6; } while (0)
#define SET_D(n,i) do { n |= (i&63); } while (0)
#define GET_A(n) ((n & 0xff0000) >> 16)
#define GET_B(n) ((n & 0xff00) >> 8)
#define GET_C(n) (n & 0xff)
static int _base64_to_bin(unsigned char dest[3], char *source,int num);
static int get_equals(char *string);
/* first part : base 64 to binary */
/** \brief base64_to_bin translates a base64 string into a binary one. important,
* \returns NULL if something went wrong (ie incorrect char)
* \returns BUFFER containing the decoded string
* \internal
*/
BUFFER *base64_to_bin(char *source){
int len;
int equals;
BUFFER *buffer = NULL;
unsigned char block[3];
/* get the number of equals signs, which mirrors the padding */
equals=get_equals(source);
if(equals>2){
return NULL;
}
buffer = buffer_new();
if (buffer == NULL) {
return NULL;
}
len=strlen(source);
while(len>4){
if(_base64_to_bin(block,source,3)){
goto error;
}
if (buffer_add_data(buffer, block, 3) < 0) {
goto error;
}
len-=4;
source+=4;
}
/* depending of the number of bytes resting, there are 3 possibilities (from the rfc) */
switch(len){
/* (1) the final quantum of encoding input is an integral
multiple of 24 bits; here, the final unit of encoded output will be
an integral multiple of 4 characters with no "=" padding */
case 4:
if(equals!=0){
goto error;
}
if(_base64_to_bin(block,source,3)){
goto error;
}
if (buffer_add_data(buffer,block,3) < 0) {
goto error;
}
return buffer;
/*(2) the final quantum of encoding input is exactly 8 bits; here, the final
unit of encoded output will be two characters followed by two "="
padding characters */
case 2:
if(equals!=2){
goto error;
}
if(_base64_to_bin(block,source,1)){
goto error;
}
if (buffer_add_data(buffer,block,1) < 0) {
goto error;
}
return buffer;
/* the final quantum of encoding input is
exactly 16 bits; here, the final unit of encoded output will be three
characters followed by one "=" padding character */
case 3:
if(equals!=1){
goto error;
}
if(_base64_to_bin(block,source,2)){
goto error;
}
if (buffer_add_data(buffer,block,2) < 0) {
goto error;
}
return buffer;
default:
/* 4,3,2 are the only padding size allowed */
goto error;
}
error:
buffer_free(buffer);
return NULL;
}
#define BLOCK(letter,n) do { ptr=strchr(alphabet,source[n]);\
if(!ptr) return -1;\
i=ptr-alphabet;\
SET_##letter(*block,i);\
} while(0)
/* returns 0 if ok, -1 if not (ie invalid char into the stuff) */
static int to_block4(unsigned long *block, char *source,int num){
char *ptr;
unsigned int i;
*block=0;
if(num<1)
return 0;
BLOCK(A,0); /* 6 bits */
BLOCK(B,1); /* 12 */
if(num<2)
return 0;
BLOCK(C,2); /* 18 */
if(num < 3)
return 0;
BLOCK(D,3); /* 24 */
return 0;
}
/* num = numbers of final bytes to be decoded */
static int _base64_to_bin(unsigned char dest[3], char *source,int num){
unsigned long block;
if(to_block4(&block,source,num))
return -1;
dest[0]=GET_A(block);
dest[1]=GET_B(block);
dest[2]=GET_C(block);
return 0;
}
/* counts the number of "=" signs, and replace them by zeroes */
static int get_equals(char *string){
char *ptr=string;
int num=0;
while((ptr=strchr(ptr,'='))){
num++;
*ptr=0;
ptr++;
}
return num;
}
/* thanks sysk for debugging my mess :) */
#define BITS(n) ((1<<n)-1)
static void _bin_to_base64(unsigned char *dest, unsigned char source[3], int len){
switch (len){
case 1:
dest[0]=alphabet[(source[0]>>2)];
dest[1]=alphabet[((source[0] & BITS(2)) << 4)];
dest[2]='=';
dest[3]='=';
break;
case 2:
dest[0]=alphabet[source[0]>>2];
dest[1]=alphabet[(source[1]>>4) | ((source[0] & BITS(2)) << 4)];
dest[2]=alphabet[(source[1]&BITS(4)) << 2];
dest[3]='=';
break;
case 3:
dest[0]=alphabet[(source[0]>>2)];
dest[1]=alphabet[(source[1]>>4) | ((source[0] & BITS(2)) << 4)];
dest[2]=alphabet[ (source[2] >> 6) | (source[1]&BITS(4)) << 2];
dest[3]=alphabet[source[2]&BITS(6)];
break;
}
}
/** \brief Converts binary data to a base64 string
* \returns the converted string
* \internal
*/
unsigned char *bin_to_base64(unsigned char *source, int len){
int flen=len + (3 - (len %3)); /* round to upper 3 multiple */
unsigned char *buffer;
unsigned char *ptr;
flen=(4 * flen)/3 + 1 ;
ptr=buffer=malloc(flen);
while(len>0){
_bin_to_base64(ptr,source,len>3?3:len);
ptr+=4;
source +=3;
len -=3;
}
ptr[0]=0;
return buffer;
}
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