diff options
Diffstat (limited to 'fs/cachefiles/key.c')
| -rw-r--r-- | fs/cachefiles/key.c | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/fs/cachefiles/key.c b/fs/cachefiles/key.c new file mode 100644 index 00000000000..81b8b2b3a67 --- /dev/null +++ b/fs/cachefiles/key.c @@ -0,0 +1,159 @@ +/* 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, GFP_KERNEL); + 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; +} |