/* Key to pathname encoder * * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public Licence * as published by the Free Software Foundation; either version * 2 of the Licence, or (at your option) any later version. */ #include <linux/slab.h>#include "internal.h" static const char cachefiles_charmap[64] =	"0123456789"			/* 0 - 9 */	"abcdefghijklmnopqrstuvwxyz"	/* 10 - 35 */	"ABCDEFGHIJKLMNOPQRSTUVWXYZ"	/* 36 - 61 */	"_-"				/* 62 - 63 */	; static const char cachefiles_filecharmap[256] = {	/* we skip space and tab and control chars */	[33 ... 46] = 1,		/* '!' -> '.' */	/* we skip '/' as it's significant to pathwalk */	[48 ... 127] = 1,		/* '0' -> '~' */}; /* * turn the raw key into something cooked * - the raw key should include the length in the two bytes at the front * - the key may be up to 514 bytes in length (including the length word) *   - "base64" encode the strange keys, mapping 3 bytes of raw to four of *     cooked *   - need to cut the cooked key into 252 char lengths (189 raw bytes) */char *cachefiles_cook_key(const u8 *raw, int keylen, uint8_t type){	unsigned char csum, ch;	unsigned int acc;	char *key;	int loop, len, max, seg, mark, print; 	_enter(",%d", keylen); 	BUG_ON(keylen < 2 || keylen > 514); 	csum = raw[0] + raw[1];	print = 1;	for (loop = 2; loop < keylen; loop++) {		ch = raw[loop];		csum += ch;		print &= cachefiles_filecharmap[ch];	} 	if (print) {		/* if the path is usable ASCII, then we render it directly */		max = keylen - 2;		max += 2;	/* two base64'd length chars on the front */		max += 5;	/* @checksum/M */		max += 3 * 2;	/* maximum number of segment dividers (".../M")				 * is ((514 + 251) / 252) = 3				 */		max += 1;	/* NUL on end */	} else {		/* calculate the maximum length of the cooked key */		keylen = (keylen + 2) / 3; 		max = keylen * 4;		max += 5;	/* @checksum/M */		max += 3 * 2;	/* maximum number of segment dividers (".../M")				 * is ((514 + 188) / 189) = 3				 */		max += 1;	/* NUL on end */	} 	max += 1;	/* 2nd NUL on end */ 	_debug("max: %d", max); 	key = kmalloc(max, cachefiles_gfp);	if (!key)		return NULL; 	len = 0; 	/* build the cooked key */	sprintf(key, "@%02x%c+", (unsigned) csum, 0);	len = 5;	mark = len - 1; 	if (print) {		acc = *(uint16_t *) raw;		raw += 2; 		key[len + 1] = cachefiles_charmap[acc & 63];		acc >>= 6;		key[len] = cachefiles_charmap[acc & 63];		len += 2; 		seg = 250;		for (loop = keylen; loop > 0; loop--) {			if (seg <= 0) {				key[len++] = '\0';				mark = len;				key[len++] = '+';				seg = 252;			} 			key[len++] = *raw++;			ASSERT(len < max);		} 		switch (type) {		case FSCACHE_COOKIE_TYPE_INDEX:		type = 'I';	break;		case FSCACHE_COOKIE_TYPE_DATAFILE:	type = 'D';	break;		default:				type = 'S';	break;		}	} else {		seg = 252;		for (loop = keylen; loop > 0; loop--) {			if (seg <= 0) {				key[len++] = '\0';				mark = len;				key[len++] = '+';				seg = 252;			} 			acc = *raw++;			acc |= *raw++ << 8;			acc |= *raw++ << 16; 			_debug("acc: %06x", acc); 			key[len++] = cachefiles_charmap[acc & 63];			acc >>= 6;			key[len++] = cachefiles_charmap[acc & 63];			acc >>= 6;			key[len++] = cachefiles_charmap[acc & 63];			acc >>= 6;			key[len++] = cachefiles_charmap[acc & 63]; 			ASSERT(len < max);		} 		switch (type) {		case FSCACHE_COOKIE_TYPE_INDEX:		type = 'J';	break;		case FSCACHE_COOKIE_TYPE_DATAFILE:	type = 'E';	break;		default:				type = 'T';	break;		}	} 	key[mark] = type;	key[len++] = 0;	key[len] = 0; 	_leave(" = %p %d", key, len);	return key;}