// SPDX-License-Identifier: GPL-2.0-or-later/* Key to pathname encoder * * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) */ #include <linux/slab.h>#include "internal.h" static const char cachefiles_charmap[64] __nonstring =	"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' -> '~' */}; static inline unsigned int how_many_hex_digits(unsigned int x){	return x ? round_up(ilog2(x) + 1, 4) / 4 : 0;} /* * turn the raw key into something cooked * - the key may be up to NAME_MAX 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) */bool cachefiles_cook_key(struct cachefiles_object *object){	const u8 *key = fscache_get_key(object->cookie), *kend;	unsigned char ch;	unsigned int acc, i, n, nle, nbe, keylen = object->cookie->key_len;	unsigned int b64len, len, print, pad;	char *name, sep; 	_enter(",%u,%*phN", keylen, keylen, key); 	BUG_ON(keylen > NAME_MAX - 3); 	print = 1;	for (i = 0; i < keylen; i++) {		ch = key[i];		print &= cachefiles_filecharmap[ch];	} 	/* If the path is usable ASCII, then we render it directly */	if (print) {		len = 1 + keylen;		name = kmalloc(len + 1, GFP_KERNEL);		if (!name)			return false; 		name[0] = 'D'; /* Data object type, string encoding */		memcpy(name + 1, key, keylen);		goto success;	} 	/* See if it makes sense to encode it as "hex,hex,hex" for each 32-bit	 * chunk.  We rely on the key having been padded out to a whole number	 * of 32-bit words.	 */	n = round_up(keylen, 4);	nbe = nle = 0;	for (i = 0; i < n; i += 4) {		u32 be = be32_to_cpu(*(__be32 *)(key + i));		u32 le = le32_to_cpu(*(__le32 *)(key + i)); 		nbe += 1 + how_many_hex_digits(be);		nle += 1 + how_many_hex_digits(le);	} 	b64len = DIV_ROUND_UP(keylen, 3);	pad = b64len * 3 - keylen;	b64len = 2 + b64len * 4; /* Length if we base64-encode it */	_debug("len=%u nbe=%u nle=%u b64=%u", keylen, nbe, nle, b64len);	if (nbe < b64len || nle < b64len) {		unsigned int nlen = min(nbe, nle) + 1;		name = kmalloc(nlen, GFP_KERNEL);		if (!name)			return false;		sep = (nbe <= nle) ? 'S' : 'T'; /* Encoding indicator */		len = 0;		for (i = 0; i < n; i += 4) {			u32 x;			if (nbe <= nle)				x = be32_to_cpu(*(__be32 *)(key + i));			else				x = le32_to_cpu(*(__le32 *)(key + i));			name[len++] = sep;			if (x != 0)				len += snprintf(name + len, nlen - len, "%x", x);			sep = ',';		}		goto success;	} 	/* We need to base64-encode it */	name = kmalloc(b64len + 1, GFP_KERNEL);	if (!name)		return false; 	name[0] = 'E';	name[1] = '0' + pad;	len = 2;	kend = key + keylen;	do {		acc  = *key++;		if (key < kend) {			acc |= *key++ << 8;			if (key < kend)				acc |= *key++ << 16;		} 		name[len++] = cachefiles_charmap[acc & 63];		acc >>= 6;		name[len++] = cachefiles_charmap[acc & 63];		acc >>= 6;		name[len++] = cachefiles_charmap[acc & 63];		acc >>= 6;		name[len++] = cachefiles_charmap[acc & 63];	} while (key < kend); success:	name[len] = 0;	object->d_name = name;	_leave(" = %s", object->d_name);	return true;}