// 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);
}