// SPDX-License-Identifier: GPL-2.0-only
/*
 * unicode.c
 *
 * PURPOSE
 *      Routines for converting between UTF-8 and OSTA Compressed Unicode.
 *      Also handles filename mangling
 *
 * DESCRIPTION
 *      OSTA Compressed Unicode is explained in the OSTA UDF specification.
 *              http://www.osta.org/
 *      UTF-8 is explained in the IETF RFC XXXX.
 *              ftp://ftp.internic.net/rfc/rfcxxxx.txt
 *
 */

#include "udfdecl.h"

#include <linux/hex.h>
#include <linux/kernel.h>
#include <linux/string.h>       /* for memset */
#include <linux/nls.h>
#include <linux/crc-itu-t.h>
#include <linux/slab.h>

#include "udf_sb.h"

#define PLANE_SIZE 0x10000
#define UNICODE_MAX 0x10ffff
#define SURROGATE_MASK 0xfffff800
#define SURROGATE_PAIR 0x0000d800
#define SURROGATE_LOW  0x00000400
#define SURROGATE_CHAR_BITS 10
#define SURROGATE_CHAR_MASK ((1 << SURROGATE_CHAR_BITS) - 1)

#define ILLEGAL_CHAR_MARK       '_'
#define EXT_MARK                '.'
#define CRC_MARK                '#'
#define EXT_SIZE                5
/* Number of chars we need to store generated CRC to make filename unique */
#define CRC_LEN                 5

static unicode_t get_utf16_char(const uint8_t *str_i, int str_i_max_len,
                                int str_i_idx, int u_ch, unicode_t *ret)
{
        unicode_t c;
        int start_idx = str_i_idx;

        /* Expand OSTA compressed Unicode to Unicode */
        c = str_i[str_i_idx++];
        if (u_ch > 1)
                c = (c << 8) | str_i[str_i_idx++];
        if ((c & SURROGATE_MASK) == SURROGATE_PAIR) {
                unicode_t next;

                /* Trailing surrogate char */
                if (str_i_idx >= str_i_max_len) {
                        c = UNICODE_MAX + 1;
                        goto out;
                }

                /* Low surrogate must follow the high one... */
                if (c & SURROGATE_LOW) {
                        c = UNICODE_MAX + 1;
                        goto out;
                }

                WARN_ON_ONCE(u_ch != 2);
                next = str_i[str_i_idx++] << 8;
                next |= str_i[str_i_idx++];
                if ((next & SURROGATE_MASK) != SURROGATE_PAIR ||
                    !(next & SURROGATE_LOW)) {
                        c = UNICODE_MAX + 1;
                        goto out;
                }

                c = PLANE_SIZE +
                    ((c & SURROGATE_CHAR_MASK) << SURROGATE_CHAR_BITS) +
                    (next & SURROGATE_CHAR_MASK);
        }
out:
        *ret = c;
        return str_i_idx - start_idx;
}


static int udf_name_conv_char(uint8_t *str_o, int str_o_max_len,
                              int *str_o_idx,
                              const uint8_t *str_i, int str_i_max_len,
                              int *str_i_idx,
                              int u_ch, int *needsCRC,
                              int (*conv_f)(wchar_t, unsigned char *, int),
                              int translate)
{
        unicode_t c;
        int illChar = 0;
        int len, gotch = 0;

        while (!gotch && *str_i_idx < str_i_max_len) {
                if (*str_o_idx >= str_o_max_len) {
                        *needsCRC = 1;
                        return gotch;
                }

                len = get_utf16_char(str_i, str_i_max_len, *str_i_idx, u_ch,
                                     &c);
                /* These chars cannot be converted. Replace them. */
                if (c == 0 || c > UNICODE_MAX || (conv_f && c > MAX_WCHAR_T) ||
                    (translate && c == '/')) {
                        illChar = 1;
                        if (!translate)
                                gotch = 1;
                } else if (illChar)
                        break;
                else
                        gotch = 1;
                *str_i_idx += len;
        }
        if (illChar) {
                *needsCRC = 1;
                c = ILLEGAL_CHAR_MARK;
                gotch = 1;
        }
        if (gotch) {
                if (conv_f) {
                        len = conv_f(c, &str_o[*str_o_idx],
                                     str_o_max_len - *str_o_idx);
                } else {
                        len = utf32_to_utf8(c, &str_o[*str_o_idx],
                                            str_o_max_len - *str_o_idx);
                        if (len < 0)
                                len = -ENAMETOOLONG;
                }
                /* Valid character? */
                if (len >= 0)
                        *str_o_idx += len;
                else if (len == -ENAMETOOLONG) {
                        *needsCRC = 1;
                        gotch = 0;
                } else {
                        str_o[(*str_o_idx)++] = ILLEGAL_CHAR_MARK;
                        *needsCRC = 1;
                }
        }
        return gotch;
}

static int udf_name_from_CS0(struct super_block *sb,
                             uint8_t *str_o, int str_max_len,
                             const uint8_t *ocu, int ocu_len,
                             int translate)
{
        uint32_t c;
        uint8_t cmp_id;
        int idx, len;
        int u_ch;
        int needsCRC = 0;
        int ext_i_len, ext_max_len;
        int str_o_len = 0;      /* Length of resulting output */
        int ext_o_len = 0;      /* Extension output length */
        int ext_crc_len = 0;    /* Extension output length if used with CRC */
        int i_ext = -1;         /* Extension position in input buffer */
        int o_crc = 0;          /* Rightmost possible output pos for CRC+ext */
        unsigned short valueCRC;
        uint8_t ext[EXT_SIZE * NLS_MAX_CHARSET_SIZE + 1];
        uint8_t crc[CRC_LEN];
        int (*conv_f)(wchar_t, unsigned char *, int);

        if (str_max_len <= 0)
                return 0;

        if (ocu_len == 0) {
                memset(str_o, 0, str_max_len);
                return 0;
        }

        if (UDF_SB(sb)->s_nls_map)
                conv_f = UDF_SB(sb)->s_nls_map->uni2char;
        else
                conv_f = NULL;

        cmp_id = ocu[0];
        if (cmp_id != 8 && cmp_id != 16) {
                memset(str_o, 0, str_max_len);
                pr_err("unknown compression code (%u)\n", cmp_id);
                return -EINVAL;
        }
        u_ch = cmp_id >> 3;

        ocu++;
        ocu_len--;

        if (ocu_len % u_ch) {
                pr_err("incorrect filename length (%d)\n", ocu_len + 1);
                return -EINVAL;
        }

        if (translate) {
                /* Look for extension */
                for (idx = ocu_len - u_ch, ext_i_len = 0;
                     (idx >= 0) && (ext_i_len < EXT_SIZE);
                     idx -= u_ch, ext_i_len++) {
                        c = ocu[idx];
                        if (u_ch > 1)
                                c = (c << 8) | ocu[idx + 1];

                        if (c == EXT_MARK) {
                                if (ext_i_len)
                                        i_ext = idx;
                                break;
                        }
                }
                if (i_ext >= 0) {
                        /* Convert extension */
                        ext_max_len = min_t(int, sizeof(ext), str_max_len);
                        ext[ext_o_len++] = EXT_MARK;
                        idx = i_ext + u_ch;
                        while (udf_name_conv_char(ext, ext_max_len, &ext_o_len,
                                                  ocu, ocu_len, &idx,
                                                  u_ch, &needsCRC,
                                                  conv_f, translate)) {
                                if ((ext_o_len + CRC_LEN) < str_max_len)
                                        ext_crc_len = ext_o_len;
                        }
                }
        }

        idx = 0;
        while (1) {
                if (translate && (idx == i_ext)) {
                        if (str_o_len > (str_max_len - ext_o_len))
                                needsCRC = 1;
                        break;
                }

                if (!udf_name_conv_char(str_o, str_max_len, &str_o_len,
                                        ocu, ocu_len, &idx,
                                        u_ch, &needsCRC, conv_f, translate))
                        break;

                if (translate &&
                    (str_o_len <= (str_max_len - ext_o_len - CRC_LEN)))
                        o_crc = str_o_len;
        }

        if (translate) {
                if (str_o_len > 0 && str_o_len <= 2 && str_o[0] == '.' &&
                    (str_o_len == 1 || str_o[1] == '.'))
                        needsCRC = 1;
                if (needsCRC) {
                        str_o_len = o_crc;
                        valueCRC = crc_itu_t(0, ocu, ocu_len);
                        crc[0] = CRC_MARK;
                        crc[1] = hex_asc_upper_hi(valueCRC >> 8);
                        crc[2] = hex_asc_upper_lo(valueCRC >> 8);
                        crc[3] = hex_asc_upper_hi(valueCRC);
                        crc[4] = hex_asc_upper_lo(valueCRC);
                        len = min_t(int, CRC_LEN, str_max_len - str_o_len);
                        memcpy(&str_o[str_o_len], crc, len);
                        str_o_len += len;
                        ext_o_len = ext_crc_len;
                }
                if (ext_o_len > 0) {
                        memcpy(&str_o[str_o_len], ext, ext_o_len);
                        str_o_len += ext_o_len;
                }
        }

        return str_o_len;
}

static int udf_name_to_CS0(struct super_block *sb,
                           uint8_t *ocu, int ocu_max_len,
                           const uint8_t *str_i, int str_len)
{
        int i, len;
        unsigned int max_val;
        int u_len, u_ch;
        unicode_t uni_char;
        int (*conv_f)(const unsigned char *, int, wchar_t *);

        if (ocu_max_len <= 0)
                return 0;

        if (UDF_SB(sb)->s_nls_map)
                conv_f = UDF_SB(sb)->s_nls_map->char2uni;
        else
                conv_f = NULL;

        memset(ocu, 0, ocu_max_len);
        ocu[0] = 8;
        max_val = 0xff;
        u_ch = 1;

try_again:
        u_len = 1;
        for (i = 0; i < str_len; i += len) {
                /* Name didn't fit? */
                if (u_len + u_ch > ocu_max_len)
                        return 0;
                if (conv_f) {
                        wchar_t wchar;

                        len = conv_f(&str_i[i], str_len - i, &wchar);
                        if (len > 0)
                                uni_char = wchar;
                } else {
                        len = utf8_to_utf32(&str_i[i], str_len - i,
                                            &uni_char);
                }
                /* Invalid character, deal with it */
                if (len <= 0 || uni_char > UNICODE_MAX) {
                        len = 1;
                        uni_char = '?';
                }

                if (uni_char > max_val) {
                        unicode_t c;

                        if (max_val == 0xff) {
                                max_val = 0xffff;
                                ocu[0] = 0x10;
                                u_ch = 2;
                                goto try_again;
                        }
                        /*
                         * Use UTF-16 encoding for chars outside we
                         * cannot encode directly.
                         */
                        if (u_len + 2 * u_ch > ocu_max_len)
                                return 0;

                        uni_char -= PLANE_SIZE;
                        c = SURROGATE_PAIR |
                            ((uni_char >> SURROGATE_CHAR_BITS) &
                             SURROGATE_CHAR_MASK);
                        ocu[u_len++] = (uint8_t)(c >> 8);
                        ocu[u_len++] = (uint8_t)(c & 0xff);
                        uni_char = SURROGATE_PAIR | SURROGATE_LOW |
                                        (uni_char & SURROGATE_CHAR_MASK);
                }

                if (max_val == 0xffff)
                        ocu[u_len++] = (uint8_t)(uni_char >> 8);
                ocu[u_len++] = (uint8_t)(uni_char & 0xff);
        }

        return u_len;
}

/*
 * Convert CS0 dstring to output charset. Warning: This function may truncate
 * input string if it is too long as it is used for informational strings only
 * and it is better to truncate the string than to refuse mounting a media.
 */
int udf_dstrCS0toChar(struct super_block *sb, uint8_t *utf_o, int o_len,
                      const uint8_t *ocu_i, int i_len)
{
        int s_len = 0;

        if (i_len > 0) {
                s_len = ocu_i[i_len - 1];
                if (s_len >= i_len) {
                        pr_warn("incorrect dstring lengths (%d/%d),"
                                " truncating\n", s_len, i_len);
                        s_len = i_len - 1;
                        /* 2-byte encoding? Need to round properly... */
                        if (ocu_i[0] == 16)
                                s_len -= (s_len - 1) & 2;
                }
        }

        return udf_name_from_CS0(sb, utf_o, o_len, ocu_i, s_len, 0);
}

int udf_get_filename(struct super_block *sb, const uint8_t *sname, int slen,
                     uint8_t *dname, int dlen)
{
        int ret;

        if (!slen)
                return -EIO;

        if (dlen <= 0)
                return 0;

        ret = udf_name_from_CS0(sb, dname, dlen, sname, slen, 1);
        /* Zero length filename isn't valid... */
        if (ret == 0)
                ret = -EINVAL;
        return ret;
}

int udf_put_filename(struct super_block *sb, const uint8_t *sname, int slen,
                     uint8_t *dname, int dlen)
{
        return udf_name_to_CS0(sb, dname, dlen, sname, slen);
}