1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* Key to pathname encoder 3 * 4 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. 5 * Written by David Howells (dhowells@redhat.com) 6 */ 7 8 #include <linux/slab.h> 9 #include "internal.h" 10 11 static const char cachefiles_charmap[64] = 12 "0123456789" /* 0 - 9 */ 13 "abcdefghijklmnopqrstuvwxyz" /* 10 - 35 */ 14 "ABCDEFGHIJKLMNOPQRSTUVWXYZ" /* 36 - 61 */ 15 "_-" /* 62 - 63 */ 16 ; 17 18 static const char cachefiles_filecharmap[256] = { 19 /* we skip space and tab and control chars */ 20 [33 ... 46] = 1, /* '!' -> '.' */ 21 /* we skip '/' as it's significant to pathwalk */ 22 [48 ... 127] = 1, /* '0' -> '~' */ 23 }; 24 25 /* 26 * turn the raw key into something cooked 27 * - the raw key should include the length in the two bytes at the front 28 * - the key may be up to 514 bytes in length (including the length word) 29 * - "base64" encode the strange keys, mapping 3 bytes of raw to four of 30 * cooked 31 * - need to cut the cooked key into 252 char lengths (189 raw bytes) 32 */ 33 char *cachefiles_cook_key(const u8 *raw, int keylen, uint8_t type) 34 { 35 unsigned char csum, ch; 36 unsigned int acc; 37 char *key; 38 int loop, len, max, seg, mark, print; 39 40 _enter(",%d", keylen); 41 42 BUG_ON(keylen < 2 || keylen > 514); 43 44 csum = raw[0] + raw[1]; 45 print = 1; 46 for (loop = 2; loop < keylen; loop++) { 47 ch = raw[loop]; 48 csum += ch; 49 print &= cachefiles_filecharmap[ch]; 50 } 51 52 if (print) { 53 /* if the path is usable ASCII, then we render it directly */ 54 max = keylen - 2; 55 max += 2; /* two base64'd length chars on the front */ 56 max += 5; /* @checksum/M */ 57 max += 3 * 2; /* maximum number of segment dividers (".../M") 58 * is ((514 + 251) / 252) = 3 59 */ 60 max += 1; /* NUL on end */ 61 } else { 62 /* calculate the maximum length of the cooked key */ 63 keylen = (keylen + 2) / 3; 64 65 max = keylen * 4; 66 max += 5; /* @checksum/M */ 67 max += 3 * 2; /* maximum number of segment dividers (".../M") 68 * is ((514 + 188) / 189) = 3 69 */ 70 max += 1; /* NUL on end */ 71 } 72 73 max += 1; /* 2nd NUL on end */ 74 75 _debug("max: %d", max); 76 77 key = kmalloc(max, cachefiles_gfp); 78 if (!key) 79 return NULL; 80 81 len = 0; 82 83 /* build the cooked key */ 84 sprintf(key, "@%02x%c+", (unsigned) csum, 0); 85 len = 5; 86 mark = len - 1; 87 88 if (print) { 89 acc = *(uint16_t *) raw; 90 raw += 2; 91 92 key[len + 1] = cachefiles_charmap[acc & 63]; 93 acc >>= 6; 94 key[len] = cachefiles_charmap[acc & 63]; 95 len += 2; 96 97 seg = 250; 98 for (loop = keylen; loop > 0; loop--) { 99 if (seg <= 0) { 100 key[len++] = '\0'; 101 mark = len; 102 key[len++] = '+'; 103 seg = 252; 104 } 105 106 key[len++] = *raw++; 107 ASSERT(len < max); 108 } 109 110 switch (type) { 111 case FSCACHE_COOKIE_TYPE_INDEX: type = 'I'; break; 112 case FSCACHE_COOKIE_TYPE_DATAFILE: type = 'D'; break; 113 default: type = 'S'; break; 114 } 115 } else { 116 seg = 252; 117 for (loop = keylen; loop > 0; loop--) { 118 if (seg <= 0) { 119 key[len++] = '\0'; 120 mark = len; 121 key[len++] = '+'; 122 seg = 252; 123 } 124 125 acc = *raw++; 126 acc |= *raw++ << 8; 127 acc |= *raw++ << 16; 128 129 _debug("acc: %06x", acc); 130 131 key[len++] = cachefiles_charmap[acc & 63]; 132 acc >>= 6; 133 key[len++] = cachefiles_charmap[acc & 63]; 134 acc >>= 6; 135 key[len++] = cachefiles_charmap[acc & 63]; 136 acc >>= 6; 137 key[len++] = cachefiles_charmap[acc & 63]; 138 139 ASSERT(len < max); 140 } 141 142 switch (type) { 143 case FSCACHE_COOKIE_TYPE_INDEX: type = 'J'; break; 144 case FSCACHE_COOKIE_TYPE_DATAFILE: type = 'E'; break; 145 default: type = 'T'; break; 146 } 147 } 148 149 key[mark] = type; 150 key[len++] = 0; 151 key[len] = 0; 152 153 _leave(" = %s %d", key, len); 154 return key; 155 } 156