cregit-Linux how code gets into the kernel

Release 4.11 fs/cachefiles/key.c

Directory: fs/cachefiles
/* 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; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells606100.00%2100.00%
Total606100.00%2100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
David Howells662100.00%2100.00%
Total662100.00%2100.00%
Directory: fs/cachefiles
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