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155 lines
3.5 KiB
155 lines
3.5 KiB
// 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 ([email protected]) |
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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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