1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/f2fs/hash.c
4 *
5 * Copyright (c) 2012 Samsung Electronics Co., Ltd.
6 *             http://www.samsung.com/
7 *
8 * Portions of this code from linux/fs/ext3/hash.c
9 *
10 * Copyright (C) 2002 by Theodore Ts'o
11 */
12#include <linux/types.h>
13#include <linux/fs.h>
14#include <linux/f2fs_fs.h>
15#include <linux/pagemap.h>
16#include <linux/unicode.h>
17
18#include "f2fs.h"
19
20/*
21 * Hashing code copied from ext3
22 */
23#define DELTA 0x9E3779B9
24
25static void TEA_transform(unsigned int buf[4], unsigned int const in[])
26{
27	__u32 sum = 0;
28	__u32 b0 = buf[0], b1 = buf[1];
29	__u32 a = in[0], b = in[1], c = in[2], d = in[3];
30	int n = 16;
31
32	do {
33		sum += DELTA;
34		b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
35		b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
36	} while (--n);
37
38	buf[0] += b0;
39	buf[1] += b1;
40}
41
42static void str2hashbuf(const unsigned char *msg, size_t len,
43				unsigned int *buf, int num)
44{
45	unsigned pad, val;
46	int i;
47
48	pad = (__u32)len | ((__u32)len << 8);
49	pad |= pad << 16;
50
51	val = pad;
52	if (len > num * 4)
53		len = num * 4;
54	for (i = 0; i < len; i++) {
55		if ((i % 4) == 0)
56			val = pad;
57		val = msg[i] + (val << 8);
58		if ((i % 4) == 3) {
59			*buf++ = val;
60			val = pad;
61			num--;
62		}
63	}
64	if (--num >= 0)
65		*buf++ = val;
66	while (--num >= 0)
67		*buf++ = pad;
68}
69
70static u32 TEA_hash_name(const u8 *p, size_t len)
71{
72	__u32 in[8], buf[4];
73
74	/* Initialize the default seed for the hash checksum functions */
75	buf[0] = 0x67452301;
76	buf[1] = 0xefcdab89;
77	buf[2] = 0x98badcfe;
78	buf[3] = 0x10325476;
79
80	while (1) {
81		str2hashbuf(p, len, in, 4);
82		TEA_transform(buf, in);
83		p += 16;
84		if (len <= 16)
85			break;
86		len -= 16;
87	}
88	return buf[0] & ~F2FS_HASH_COL_BIT;
89}
90
91/*
92 * Compute @fname->hash.  For all directories, @fname->disk_name must be set.
93 * For casefolded directories, @fname->usr_fname must be set, and also
94 * @fname->cf_name if the filename is valid Unicode and is not "." or "..".
95 */
96void f2fs_hash_filename(const struct inode *dir, struct f2fs_filename *fname)
97{
98	const u8 *name = fname->disk_name.name;
99	size_t len = fname->disk_name.len;
100
101	WARN_ON_ONCE(!name);
102
103	if (is_dot_dotdot(name, len)) {
104		fname->hash = 0;
105		return;
106	}
107
108#if IS_ENABLED(CONFIG_UNICODE)
109	if (IS_CASEFOLDED(dir)) {
110		/*
111		 * If the casefolded name is provided, hash it instead of the
112		 * on-disk name.  If the casefolded name is *not* provided, that
113		 * should only be because the name wasn't valid Unicode or was
114		 * "." or "..", so fall back to treating the name as an opaque
115		 * byte sequence.  Note that to handle encrypted directories,
116		 * the fallback must use usr_fname (plaintext) rather than
117		 * disk_name (ciphertext).
118		 */
119		WARN_ON_ONCE(!fname->usr_fname->name);
120		if (fname->cf_name.name) {
121			name = fname->cf_name.name;
122			len = fname->cf_name.len;
123		} else {
124			name = fname->usr_fname->name;
125			len = fname->usr_fname->len;
126		}
127		if (IS_ENCRYPTED(dir)) {
128			struct qstr tmp = QSTR_INIT(name, len);
129
130			fname->hash =
131				cpu_to_le32(fscrypt_fname_siphash(dir, &tmp));
132			return;
133		}
134	}
135#endif
136	fname->hash = cpu_to_le32(TEA_hash_name(name, len));
137}
138