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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Key to pathname encoder
3 *
4 * Copyright (C) 2021 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
11static const char cachefiles_charmap[64] =
12 "0123456789" /* 0 - 9 */
13 "abcdefghijklmnopqrstuvwxyz" /* 10 - 35 */
14 "ABCDEFGHIJKLMNOPQRSTUVWXYZ" /* 36 - 61 */
15 "_-" /* 62 - 63 */
16 ;
17
18static 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
25static inline unsigned int how_many_hex_digits(unsigned int x)
26{
27 return x ? round_up(ilog2(x) + 1, 4) / 4 : 0;
28}
29
30/*
31 * turn the raw key into something cooked
32 * - the key may be up to NAME_MAX in length (including the length word)
33 * - "base64" encode the strange keys, mapping 3 bytes of raw to four of
34 * cooked
35 * - need to cut the cooked key into 252 char lengths (189 raw bytes)
36 */
37bool cachefiles_cook_key(struct cachefiles_object *object)
38{
39 const u8 *key = fscache_get_key(object->cookie), *kend;
40 unsigned char ch;
41 unsigned int acc, i, n, nle, nbe, keylen = object->cookie->key_len;
42 unsigned int b64len, len, print, pad;
43 char *name, sep;
44
45 _enter(",%u,%*phN", keylen, keylen, key);
46
47 BUG_ON(keylen > NAME_MAX - 3);
48
49 print = 1;
50 for (i = 0; i < keylen; i++) {
51 ch = key[i];
52 print &= cachefiles_filecharmap[ch];
53 }
54
55 /* If the path is usable ASCII, then we render it directly */
56 if (print) {
57 len = 1 + keylen;
58 name = kmalloc(len + 1, GFP_KERNEL);
59 if (!name)
60 return false;
61
62 name[0] = 'D'; /* Data object type, string encoding */
63 memcpy(name + 1, key, keylen);
64 goto success;
65 }
66
67 /* See if it makes sense to encode it as "hex,hex,hex" for each 32-bit
68 * chunk. We rely on the key having been padded out to a whole number
69 * of 32-bit words.
70 */
71 n = round_up(keylen, 4);
72 nbe = nle = 0;
73 for (i = 0; i < n; i += 4) {
74 u32 be = be32_to_cpu(*(__be32 *)(key + i));
75 u32 le = le32_to_cpu(*(__le32 *)(key + i));
76
77 nbe += 1 + how_many_hex_digits(be);
78 nle += 1 + how_many_hex_digits(le);
79 }
80
81 b64len = DIV_ROUND_UP(keylen, 3);
82 pad = b64len * 3 - keylen;
83 b64len = 2 + b64len * 4; /* Length if we base64-encode it */
84 _debug("len=%u nbe=%u nle=%u b64=%u", keylen, nbe, nle, b64len);
85 if (nbe < b64len || nle < b64len) {
86 unsigned int nlen = min(nbe, nle) + 1;
87 name = kmalloc(nlen, GFP_KERNEL);
88 if (!name)
89 return false;
90 sep = (nbe <= nle) ? 'S' : 'T'; /* Encoding indicator */
91 len = 0;
92 for (i = 0; i < n; i += 4) {
93 u32 x;
94 if (nbe <= nle)
95 x = be32_to_cpu(*(__be32 *)(key + i));
96 else
97 x = le32_to_cpu(*(__le32 *)(key + i));
98 name[len++] = sep;
99 if (x != 0)
100 len += snprintf(name + len, nlen - len, "%x", x);
101 sep = ',';
102 }
103 goto success;
104 }
105
106 /* We need to base64-encode it */
107 name = kmalloc(b64len + 1, GFP_KERNEL);
108 if (!name)
109 return false;
110
111 name[0] = 'E';
112 name[1] = '0' + pad;
113 len = 2;
114 kend = key + keylen;
115 do {
116 acc = *key++;
117 if (key < kend) {
118 acc |= *key++ << 8;
119 if (key < kend)
120 acc |= *key++ << 16;
121 }
122
123 name[len++] = cachefiles_charmap[acc & 63];
124 acc >>= 6;
125 name[len++] = cachefiles_charmap[acc & 63];
126 acc >>= 6;
127 name[len++] = cachefiles_charmap[acc & 63];
128 acc >>= 6;
129 name[len++] = cachefiles_charmap[acc & 63];
130 } while (key < kend);
131
132success:
133 name[len] = 0;
134 object->d_name = name;
135 object->d_name_len = len;
136 _leave(" = %s", object->d_name);
137 return true;
138}
1/* Key to pathname encoder
2 *
3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#include <linux/slab.h>
13#include "internal.h"
14
15static const char cachefiles_charmap[64] =
16 "0123456789" /* 0 - 9 */
17 "abcdefghijklmnopqrstuvwxyz" /* 10 - 35 */
18 "ABCDEFGHIJKLMNOPQRSTUVWXYZ" /* 36 - 61 */
19 "_-" /* 62 - 63 */
20 ;
21
22static const char cachefiles_filecharmap[256] = {
23 /* we skip space and tab and control chars */
24 [33 ... 46] = 1, /* '!' -> '.' */
25 /* we skip '/' as it's significant to pathwalk */
26 [48 ... 127] = 1, /* '0' -> '~' */
27};
28
29/*
30 * turn the raw key into something cooked
31 * - the raw key should include the length in the two bytes at the front
32 * - the key may be up to 514 bytes in length (including the length word)
33 * - "base64" encode the strange keys, mapping 3 bytes of raw to four of
34 * cooked
35 * - need to cut the cooked key into 252 char lengths (189 raw bytes)
36 */
37char *cachefiles_cook_key(const u8 *raw, int keylen, uint8_t type)
38{
39 unsigned char csum, ch;
40 unsigned int acc;
41 char *key;
42 int loop, len, max, seg, mark, print;
43
44 _enter(",%d", keylen);
45
46 BUG_ON(keylen < 2 || keylen > 514);
47
48 csum = raw[0] + raw[1];
49 print = 1;
50 for (loop = 2; loop < keylen; loop++) {
51 ch = raw[loop];
52 csum += ch;
53 print &= cachefiles_filecharmap[ch];
54 }
55
56 if (print) {
57 /* if the path is usable ASCII, then we render it directly */
58 max = keylen - 2;
59 max += 2; /* two base64'd length chars on the front */
60 max += 5; /* @checksum/M */
61 max += 3 * 2; /* maximum number of segment dividers (".../M")
62 * is ((514 + 251) / 252) = 3
63 */
64 max += 1; /* NUL on end */
65 } else {
66 /* calculate the maximum length of the cooked key */
67 keylen = (keylen + 2) / 3;
68
69 max = keylen * 4;
70 max += 5; /* @checksum/M */
71 max += 3 * 2; /* maximum number of segment dividers (".../M")
72 * is ((514 + 188) / 189) = 3
73 */
74 max += 1; /* NUL on end */
75 }
76
77 max += 1; /* 2nd NUL on end */
78
79 _debug("max: %d", max);
80
81 key = kmalloc(max, GFP_KERNEL);
82 if (!key)
83 return NULL;
84
85 len = 0;
86
87 /* build the cooked key */
88 sprintf(key, "@%02x%c+", (unsigned) csum, 0);
89 len = 5;
90 mark = len - 1;
91
92 if (print) {
93 acc = *(uint16_t *) raw;
94 raw += 2;
95
96 key[len + 1] = cachefiles_charmap[acc & 63];
97 acc >>= 6;
98 key[len] = cachefiles_charmap[acc & 63];
99 len += 2;
100
101 seg = 250;
102 for (loop = keylen; loop > 0; loop--) {
103 if (seg <= 0) {
104 key[len++] = '\0';
105 mark = len;
106 key[len++] = '+';
107 seg = 252;
108 }
109
110 key[len++] = *raw++;
111 ASSERT(len < max);
112 }
113
114 switch (type) {
115 case FSCACHE_COOKIE_TYPE_INDEX: type = 'I'; break;
116 case FSCACHE_COOKIE_TYPE_DATAFILE: type = 'D'; break;
117 default: type = 'S'; break;
118 }
119 } else {
120 seg = 252;
121 for (loop = keylen; loop > 0; loop--) {
122 if (seg <= 0) {
123 key[len++] = '\0';
124 mark = len;
125 key[len++] = '+';
126 seg = 252;
127 }
128
129 acc = *raw++;
130 acc |= *raw++ << 8;
131 acc |= *raw++ << 16;
132
133 _debug("acc: %06x", acc);
134
135 key[len++] = cachefiles_charmap[acc & 63];
136 acc >>= 6;
137 key[len++] = cachefiles_charmap[acc & 63];
138 acc >>= 6;
139 key[len++] = cachefiles_charmap[acc & 63];
140 acc >>= 6;
141 key[len++] = cachefiles_charmap[acc & 63];
142
143 ASSERT(len < max);
144 }
145
146 switch (type) {
147 case FSCACHE_COOKIE_TYPE_INDEX: type = 'J'; break;
148 case FSCACHE_COOKIE_TYPE_DATAFILE: type = 'E'; break;
149 default: type = 'T'; break;
150 }
151 }
152
153 key[mark] = type;
154 key[len++] = 0;
155 key[len] = 0;
156
157 _leave(" = %p %d", key, len);
158 return key;
159}