156 lines
3.5 KiB
C
156 lines
3.5 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* Key to pathname encoder
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*
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#include <linux/slab.h>
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#include "internal.h"
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static const char cachefiles_charmap[64] =
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"0123456789" /* 0 - 9 */
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"abcdefghijklmnopqrstuvwxyz" /* 10 - 35 */
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"ABCDEFGHIJKLMNOPQRSTUVWXYZ" /* 36 - 61 */
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"_-" /* 62 - 63 */
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;
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static const char cachefiles_filecharmap[256] = {
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/* we skip space and tab and control chars */
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[33 ... 46] = 1, /* '!' -> '.' */
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/* we skip '/' as it's significant to pathwalk */
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[48 ... 127] = 1, /* '0' -> '~' */
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};
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/*
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* turn the raw key into something cooked
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* - the raw key should include the length in the two bytes at the front
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* - the key may be up to 514 bytes in length (including the length word)
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* - "base64" encode the strange keys, mapping 3 bytes of raw to four of
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* cooked
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* - need to cut the cooked key into 252 char lengths (189 raw bytes)
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*/
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char *cachefiles_cook_key(const u8 *raw, int keylen, uint8_t type)
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{
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unsigned char csum, ch;
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unsigned int acc;
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char *key;
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int loop, len, max, seg, mark, print;
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_enter(",%d", keylen);
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BUG_ON(keylen < 2 || keylen > 514);
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csum = raw[0] + raw[1];
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print = 1;
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for (loop = 2; loop < keylen; loop++) {
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ch = raw[loop];
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csum += ch;
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print &= cachefiles_filecharmap[ch];
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}
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if (print) {
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/* if the path is usable ASCII, then we render it directly */
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max = keylen - 2;
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max += 2; /* two base64'd length chars on the front */
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max += 5; /* @checksum/M */
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max += 3 * 2; /* maximum number of segment dividers (".../M")
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* is ((514 + 251) / 252) = 3
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*/
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max += 1; /* NUL on end */
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} else {
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/* calculate the maximum length of the cooked key */
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keylen = (keylen + 2) / 3;
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max = keylen * 4;
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max += 5; /* @checksum/M */
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max += 3 * 2; /* maximum number of segment dividers (".../M")
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* is ((514 + 188) / 189) = 3
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*/
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max += 1; /* NUL on end */
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}
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max += 1; /* 2nd NUL on end */
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_debug("max: %d", max);
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key = kmalloc(max, cachefiles_gfp);
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if (!key)
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return NULL;
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len = 0;
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/* build the cooked key */
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sprintf(key, "@%02x%c+", (unsigned) csum, 0);
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len = 5;
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mark = len - 1;
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if (print) {
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acc = *(uint16_t *) raw;
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raw += 2;
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key[len + 1] = cachefiles_charmap[acc & 63];
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acc >>= 6;
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key[len] = cachefiles_charmap[acc & 63];
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len += 2;
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seg = 250;
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for (loop = keylen; loop > 0; loop--) {
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if (seg <= 0) {
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key[len++] = '\0';
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mark = len;
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key[len++] = '+';
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seg = 252;
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}
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key[len++] = *raw++;
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ASSERT(len < max);
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}
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switch (type) {
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case FSCACHE_COOKIE_TYPE_INDEX: type = 'I'; break;
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case FSCACHE_COOKIE_TYPE_DATAFILE: type = 'D'; break;
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default: type = 'S'; break;
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}
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} else {
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seg = 252;
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for (loop = keylen; loop > 0; loop--) {
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if (seg <= 0) {
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key[len++] = '\0';
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mark = len;
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key[len++] = '+';
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seg = 252;
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}
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acc = *raw++;
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acc |= *raw++ << 8;
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acc |= *raw++ << 16;
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_debug("acc: %06x", acc);
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key[len++] = cachefiles_charmap[acc & 63];
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acc >>= 6;
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key[len++] = cachefiles_charmap[acc & 63];
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acc >>= 6;
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key[len++] = cachefiles_charmap[acc & 63];
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acc >>= 6;
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key[len++] = cachefiles_charmap[acc & 63];
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ASSERT(len < max);
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}
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switch (type) {
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case FSCACHE_COOKIE_TYPE_INDEX: type = 'J'; break;
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case FSCACHE_COOKIE_TYPE_DATAFILE: type = 'E'; break;
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default: type = 'T'; break;
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}
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}
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key[mark] = type;
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key[len++] = 0;
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key[len] = 0;
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_leave(" = %p %d", key, len);
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return key;
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}
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