fs/ext4/hash.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  *  linux/fs/ext4/hash.c
  *
  * Copyright (C) 2002 by Theodore Ts'o
  */

 #include <linux/fs.h>
 #include <linux/unicode.h>
 #include <linux/compiler.h>
 #include <linux/bitops.h>
 #include "ext4.h"

 #define DELTA 0x9E3779B9

 static void TEA_transform(__u32 buf[4], __u32 const in[])
 {
 	__u32	sum = 0;
 	__u32	b0 = buf[0], b1 = buf[1];
 	__u32	a = in[0], b = in[1], c = in[2], d = in[3];
 	int	n = 16;

 	do {
 		sum += DELTA;
 		b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
 		b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
 	} while (--n);

 	buf[0] += b0;
 	buf[1] += b1;
 }

 /* F, G and H are basic MD4 functions: selection, majority, parity */
 #define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
 #define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z)))
 #define H(x, y, z) ((x) ^ (y) ^ (z))

 /*
  * The generic round function.  The application is so specific that
  * we don't bother protecting all the arguments with parens, as is generally
  * good macro practice, in favor of extra legibility.
  * Rotation is separate from addition to prevent recomputation
  */
 #define ROUND(f, a, b, c, d, x, s)	\
 	(a += f(b, c, d) + x, a = rol32(a, s))
 #define K1 0
 #define K2 013240474631UL
 #define K3 015666365641UL

 /*
  * Basic cut-down MD4 transform.  Returns only 32 bits of result.
  */
 static __u32 half_md4_transform(__u32 buf[4], __u32 const in[8])
 {
 	__u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3];

 	/* Round 1 */
 	ROUND(F, a, b, c, d, in[0] + K1,  3);
 	ROUND(F, d, a, b, c, in[1] + K1,  7);
 	ROUND(F, c, d, a, b, in[2] + K1, 11);
 	ROUND(F, b, c, d, a, in[3] + K1, 19);
 	ROUND(F, a, b, c, d, in[4] + K1,  3);
 	ROUND(F, d, a, b, c, in[5] + K1,  7);
 	ROUND(F, c, d, a, b, in[6] + K1, 11);
 	ROUND(F, b, c, d, a, in[7] + K1, 19);

 	/* Round 2 */
 	ROUND(G, a, b, c, d, in[1] + K2,  3);
 	ROUND(G, d, a, b, c, in[3] + K2,  5);
 	ROUND(G, c, d, a, b, in[5] + K2,  9);
 	ROUND(G, b, c, d, a, in[7] + K2, 13);
 	ROUND(G, a, b, c, d, in[0] + K2,  3);
 	ROUND(G, d, a, b, c, in[2] + K2,  5);
 	ROUND(G, c, d, a, b, in[4] + K2,  9);
 	ROUND(G, b, c, d, a, in[6] + K2, 13);

 	/* Round 3 */
 	ROUND(H, a, b, c, d, in[3] + K3,  3);
 	ROUND(H, d, a, b, c, in[7] + K3,  9);
 	ROUND(H, c, d, a, b, in[2] + K3, 11);
 	ROUND(H, b, c, d, a, in[6] + K3, 15);
 	ROUND(H, a, b, c, d, in[1] + K3,  3);
 	ROUND(H, d, a, b, c, in[5] + K3,  9);
 	ROUND(H, c, d, a, b, in[0] + K3, 11);
 	ROUND(H, b, c, d, a, in[4] + K3, 15);

 	buf[0] += a;
 	buf[1] += b;
 	buf[2] += c;
 	buf[3] += d;

 	return buf[1]; /* "most hashed" word */
 }
 #undef ROUND
 #undef K1
 #undef K2
 #undef K3
 #undef F
 #undef G
 #undef H

 /* The old legacy hash */
 static __u32 dx_hack_hash_unsigned(const char *name, int len)
 {
 	__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
 	const unsigned char *ucp = (const unsigned char *) name;

 	while (len--) {
 		hash = hash1 + (hash0 ^ (((int) *ucp++) * 7152373));

 		if (hash & 0x80000000)
 			hash -= 0x7fffffff;
 		hash1 = hash0;
 		hash0 = hash;
 	}
 	return hash0 << 1;
 }

 static __u32 dx_hack_hash_signed(const char *name, int len)
 {
 	__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
 	const signed char *scp = (const signed char *) name;

 	while (len--) {
 		hash = hash1 + (hash0 ^ (((int) *scp++) * 7152373));

 		if (hash & 0x80000000)
 			hash -= 0x7fffffff;
 		hash1 = hash0;
 		hash0 = hash;
 	}
 	return hash0 << 1;
 }

 static void str2hashbuf_signed(const char *msg, int len, __u32 *buf, int num)
 {
 	__u32	pad, val;
 	int	i;
 	const signed char *scp = (const signed char *) msg;

 	pad = (__u32)len | ((__u32)len << 8);
 	pad |= pad << 16;

 	val = pad;
 	if (len > num*4)
 		len = num * 4;
 	for (i = 0; i < len; i++) {
 		val = ((int) scp[i]) + (val << 8);
 		if ((i % 4) == 3) {
 			*buf++ = val;
 			val = pad;
 			num--;
 		}
 	}
 	if (--num >= 0)
 		*buf++ = val;
 	while (--num >= 0)
 		*buf++ = pad;
 }

 static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num)
 {
 	__u32	pad, val;
 	int	i;
 	const unsigned char *ucp = (const unsigned char *) msg;

 	pad = (__u32)len | ((__u32)len << 8);
 	pad |= pad << 16;

 	val = pad;
 	if (len > num*4)
 		len = num * 4;
 	for (i = 0; i < len; i++) {
 		val = ((int) ucp[i]) + (val << 8);
 		if ((i % 4) == 3) {
 			*buf++ = val;
 			val = pad;
 			num--;
 		}
 	}
 	if (--num >= 0)
 		*buf++ = val;
 	while (--num >= 0)
 		*buf++ = pad;
 }

 /*
  * Returns the hash of a filename.  If len is 0 and name is NULL, then
  * this function can be used to test whether or not a hash version is
  * supported.
  *
  * The seed is an 4 longword (32 bits) "secret" which can be used to
  * uniquify a hash.  If the seed is all zero's, then some default seed
  * may be used.
  *
  * A particular hash version specifies whether or not the seed is
  * represented, and whether or not the returned hash is 32 bits or 64
  * bits.  32 bit hashes will return 0 for the minor hash.
  */
 static int __ext4fs_dirhash(const char *name, int len,
 			    struct dx_hash_info *hinfo)
 {
 	__u32	hash;
 	__u32	minor_hash = 0;
 	const char	*p;
 	int		i;
 	__u32		in[8], buf[4];
 	void		(*str2hashbuf)(const char *, int, __u32 *, int) =
 				str2hashbuf_signed;

 	/* Initialize the default seed for the hash checksum functions */
 	buf[0] = 0x67452301;
 	buf[1] = 0xefcdab89;
 	buf[2] = 0x98badcfe;
 	buf[3] = 0x10325476;

 	/* Check to see if the seed is all zero's */
 	if (hinfo->seed) {
 		for (i = 0; i < 4; i++) {
 			if (hinfo->seed[i]) {
 				memcpy(buf, hinfo->seed, sizeof(buf));
 				break;
 			}
 		}
 	}

 	switch (hinfo->hash_version) {
 	case DX_HASH_LEGACY_UNSIGNED:
 		hash = dx_hack_hash_unsigned(name, len);
 		break;
 	case DX_HASH_LEGACY:
 		hash = dx_hack_hash_signed(name, len);
 		break;
 	case DX_HASH_HALF_MD4_UNSIGNED:
 		str2hashbuf = str2hashbuf_unsigned;
 		fallthrough;
 	case DX_HASH_HALF_MD4:
 		p = name;
 		while (len > 0) {
 			(*str2hashbuf)(p, len, in, 8);
 			half_md4_transform(buf, in);
 			len -= 32;
 			p += 32;
 		}
 		minor_hash = buf[2];
 		hash = buf[1];
 		break;
 	case DX_HASH_TEA_UNSIGNED:
 		str2hashbuf = str2hashbuf_unsigned;
 		fallthrough;
 	case DX_HASH_TEA:
 		p = name;
 		while (len > 0) {
 			(*str2hashbuf)(p, len, in, 4);
 			TEA_transform(buf, in);
 			len -= 16;
 			p += 16;
 		}
 		hash = buf[0];
 		minor_hash = buf[1];
 		break;
 	default:
 		hinfo->hash = 0;
 		return -1;
 	}
 	hash = hash & ~1;
 	if (hash == (EXT4_HTREE_EOF_32BIT << 1))
 		hash = (EXT4_HTREE_EOF_32BIT - 1) << 1;
 	hinfo->hash = hash;
 	hinfo->minor_hash = minor_hash;
 	return 0;
 }

 int ext4fs_dirhash(const struct inode *dir, const char *name, int len,
 		   struct dx_hash_info *hinfo)
 {
 #ifdef CONFIG_UNICODE
 	const struct unicode_map *um = dir->i_sb->s_encoding;
 	int r, dlen;
 	unsigned char *buff;
 	struct qstr qstr = {.name = name, .len = len };

 	if (len && IS_CASEFOLDED(dir) && um) {
 		buff = kzalloc(sizeof(char) * PATH_MAX, GFP_KERNEL);
 		if (!buff)
 			return -ENOMEM;

 		dlen = utf8_casefold(um, &qstr, buff, PATH_MAX);
 		if (dlen < 0) {
 			kfree(buff);
 			goto opaque_seq;
 		}

 		r = __ext4fs_dirhash(buff, dlen, hinfo);

 		kfree(buff);
 		return r;
 	}
 opaque_seq:
 #endif
 	return __ext4fs_dirhash(name, len, hinfo);
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* linux/fs/ext4/hash.c
	*
	* Copyright (C) 2002 by Theodore Ts'o
	*/

	#include <linux/fs.h>
	#include <linux/unicode.h>
	#include <linux/compiler.h>
	#include <linux/bitops.h>
	#include "ext4.h"

	#define DELTA 0x9E3779B9

	static void TEA_transform(__u32 buf[4], __u32 const in[])
	{
	__u32 sum = 0;
	__u32 b0 = buf[0], b1 = buf[1];
	__u32 a = in[0], b = in[1], c = in[2], d = in[3];
	int n = 16;

	do {
	sum += DELTA;
	b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
	b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
	} while (--n);

	buf[0] += b0;
	buf[1] += b1;
	}

	/* F, G and H are basic MD4 functions: selection, majority, parity */
	#define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
	#define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z)))
	#define H(x, y, z) ((x) ^ (y) ^ (z))

	/*
	* The generic round function. The application is so specific that
	* we don't bother protecting all the arguments with parens, as is generally
	* good macro practice, in favor of extra legibility.
	* Rotation is separate from addition to prevent recomputation
	*/
	#define ROUND(f, a, b, c, d, x, s) \
	(a += f(b, c, d) + x, a = rol32(a, s))
	#define K1 0
	#define K2 013240474631UL
	#define K3 015666365641UL

	/*
	* Basic cut-down MD4 transform. Returns only 32 bits of result.
	*/
	static __u32 half_md4_transform(__u32 buf[4], __u32 const in[8])
	{
	__u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3];

	/* Round 1 */
	ROUND(F, a, b, c, d, in[0] + K1, 3);
	ROUND(F, d, a, b, c, in[1] + K1, 7);
	ROUND(F, c, d, a, b, in[2] + K1, 11);
	ROUND(F, b, c, d, a, in[3] + K1, 19);
	ROUND(F, a, b, c, d, in[4] + K1, 3);
	ROUND(F, d, a, b, c, in[5] + K1, 7);
	ROUND(F, c, d, a, b, in[6] + K1, 11);
	ROUND(F, b, c, d, a, in[7] + K1, 19);

	/* Round 2 */
	ROUND(G, a, b, c, d, in[1] + K2, 3);
	ROUND(G, d, a, b, c, in[3] + K2, 5);
	ROUND(G, c, d, a, b, in[5] + K2, 9);
	ROUND(G, b, c, d, a, in[7] + K2, 13);
	ROUND(G, a, b, c, d, in[0] + K2, 3);
	ROUND(G, d, a, b, c, in[2] + K2, 5);
	ROUND(G, c, d, a, b, in[4] + K2, 9);
	ROUND(G, b, c, d, a, in[6] + K2, 13);

	/* Round 3 */
	ROUND(H, a, b, c, d, in[3] + K3, 3);
	ROUND(H, d, a, b, c, in[7] + K3, 9);
	ROUND(H, c, d, a, b, in[2] + K3, 11);
	ROUND(H, b, c, d, a, in[6] + K3, 15);
	ROUND(H, a, b, c, d, in[1] + K3, 3);
	ROUND(H, d, a, b, c, in[5] + K3, 9);
	ROUND(H, c, d, a, b, in[0] + K3, 11);
	ROUND(H, b, c, d, a, in[4] + K3, 15);

	buf[0] += a;
	buf[1] += b;
	buf[2] += c;
	buf[3] += d;

	return buf[1]; /* "most hashed" word */
	}
	#undef ROUND
	#undef K1
	#undef K2
	#undef K3
	#undef F
	#undef G
	#undef H

	/* The old legacy hash */
	static __u32 dx_hack_hash_unsigned(const char *name, int len)
	{
	__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
	const unsigned char ucp = (const unsigned char ) name;

	while (len--) {
	hash = hash1 + (hash0 ^ (((int) ucp++) 7152373));

	if (hash & 0x80000000)
	hash -= 0x7fffffff;
	hash1 = hash0;
	hash0 = hash;
	}
	return hash0 << 1;
	}

	static __u32 dx_hack_hash_signed(const char *name, int len)
	{
	__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
	const signed char scp = (const signed char ) name;

	while (len--) {
	hash = hash1 + (hash0 ^ (((int) scp++) 7152373));

	if (hash & 0x80000000)
	hash -= 0x7fffffff;
	hash1 = hash0;
	hash0 = hash;
	}
	return hash0 << 1;
	}

	static void str2hashbuf_signed(const char msg, int len, __u32 buf, int num)
	{
	__u32 pad, val;
	int i;
	const signed char scp = (const signed char ) msg;

	pad = (__u32)len \| ((__u32)len << 8);
	pad \|= pad << 16;

	val = pad;
	if (len > num*4)
	len = num * 4;
	for (i = 0; i < len; i++) {
	val = ((int) scp[i]) + (val << 8);
	if ((i % 4) == 3) {
	*buf++ = val;
	val = pad;
	num--;
	}
	}
	if (--num >= 0)
	*buf++ = val;
	while (--num >= 0)
	*buf++ = pad;
	}

	static void str2hashbuf_unsigned(const char msg, int len, __u32 buf, int num)
	{
	__u32 pad, val;
	int i;
	const unsigned char ucp = (const unsigned char ) msg;

	pad = (__u32)len \| ((__u32)len << 8);
	pad \|= pad << 16;

	val = pad;
	if (len > num*4)
	len = num * 4;
	for (i = 0; i < len; i++) {
	val = ((int) ucp[i]) + (val << 8);
	if ((i % 4) == 3) {
	*buf++ = val;
	val = pad;
	num--;
	}
	}
	if (--num >= 0)
	*buf++ = val;
	while (--num >= 0)
	*buf++ = pad;
	}

	/*
	* Returns the hash of a filename. If len is 0 and name is NULL, then
	* this function can be used to test whether or not a hash version is
	* supported.
	*
	* The seed is an 4 longword (32 bits) "secret" which can be used to
	* uniquify a hash. If the seed is all zero's, then some default seed
	* may be used.
	*
	* A particular hash version specifies whether or not the seed is
	* represented, and whether or not the returned hash is 32 bits or 64
	* bits. 32 bit hashes will return 0 for the minor hash.
	*/
	static int __ext4fs_dirhash(const char *name, int len,
	struct dx_hash_info *hinfo)
	{
	__u32 hash;
	__u32 minor_hash = 0;
	const char *p;
	int i;
	__u32 in[8], buf[4];
	void (str2hashbuf)(const char , int, __u32 *, int) =
	str2hashbuf_signed;

	/* Initialize the default seed for the hash checksum functions */
	buf[0] = 0x67452301;
	buf[1] = 0xefcdab89;
	buf[2] = 0x98badcfe;
	buf[3] = 0x10325476;

	/* Check to see if the seed is all zero's */
	if (hinfo->seed) {
	for (i = 0; i < 4; i++) {
	if (hinfo->seed[i]) {
	memcpy(buf, hinfo->seed, sizeof(buf));
	break;
	}
	}
	}

	switch (hinfo->hash_version) {
	case DX_HASH_LEGACY_UNSIGNED:
	hash = dx_hack_hash_unsigned(name, len);
	break;
	case DX_HASH_LEGACY:
	hash = dx_hack_hash_signed(name, len);
	break;
	case DX_HASH_HALF_MD4_UNSIGNED:
	str2hashbuf = str2hashbuf_unsigned;
	fallthrough;
	case DX_HASH_HALF_MD4:
	p = name;
	while (len > 0) {
	(*str2hashbuf)(p, len, in, 8);
	half_md4_transform(buf, in);
	len -= 32;
	p += 32;
	}
	minor_hash = buf[2];
	hash = buf[1];
	break;
	case DX_HASH_TEA_UNSIGNED:
	str2hashbuf = str2hashbuf_unsigned;
	fallthrough;
	case DX_HASH_TEA:
	p = name;
	while (len > 0) {
	(*str2hashbuf)(p, len, in, 4);
	TEA_transform(buf, in);
	len -= 16;
	p += 16;
	}
	hash = buf[0];
	minor_hash = buf[1];
	break;
	default:
	hinfo->hash = 0;
	return -1;
	}
	hash = hash & ~1;
	if (hash == (EXT4_HTREE_EOF_32BIT << 1))
	hash = (EXT4_HTREE_EOF_32BIT - 1) << 1;
	hinfo->hash = hash;
	hinfo->minor_hash = minor_hash;
	return 0;
	}

	int ext4fs_dirhash(const struct inode dir, const char name, int len,
	struct dx_hash_info *hinfo)
	{
	#ifdef CONFIG_UNICODE
	const struct unicode_map *um = dir->i_sb->s_encoding;
	int r, dlen;
	unsigned char *buff;
	struct qstr qstr = {.name = name, .len = len };

	if (len && IS_CASEFOLDED(dir) && um) {
	buff = kzalloc(sizeof(char) * PATH_MAX, GFP_KERNEL);
	if (!buff)
	return -ENOMEM;

	dlen = utf8_casefold(um, &qstr, buff, PATH_MAX);
	if (dlen < 0) {
	kfree(buff);
	goto opaque_seq;
	}

	r = __ext4fs_dirhash(buff, dlen, hinfo);

	kfree(buff);
	return r;
	}
	opaque_seq:
	#endif
	return __ext4fs_dirhash(name, len, hinfo);
	}