lfn.c

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/* lfn.c - Functions for handling VFAT long filenames
 
   Copyright (C) 1998 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
   Copyright (C) 2008-2014 Daniel Baumann <mail@daniel-baumann.ch>
   Copyright (C) 2015 Andreas Bombe <aeb@debian.org>
 
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
   GNU General Public License for more details.
 
   You should have received a copy of the GNU General Public License
   along with this program. If not, see <http://www.gnu.org/licenses/>.
 
   The complete text of the GNU General Public License
   can be found in /usr/share/common-licenses/GPL-3 file.
*/
 
#include "vfatlib.h"
 
#define NDEBUG
#include <debug.h>
 
typedef struct {
    uint8_t id;         /* sequence number for slot */
    uint8_t name0_4[10];    /* first 5 characters in name */
    uint8_t attr;       /* attribute byte */
    uint8_t reserved;       /* always 0 */
    uint8_t alias_checksum; /* checksum for 8.3 alias */
    uint8_t name5_10[12];   /* 6 more characters in name */
    uint16_t start;     /* starting cluster number, 0 in long slots */
    uint8_t name11_12[4];   /* last 2 characters in name */
} LFN_ENT;
 
#define LFN_ID_START    0x40
#define LFN_ID_SLOTMASK 0x1f
 
#define CHARS_PER_LFN   13
 
/* These modul-global vars represent the state of the LFN parser */
unsigned char *lfn_unicode = NULL;
unsigned char lfn_checksum;
int lfn_slot = -1;
off_t *lfn_offsets = NULL;
int lfn_parts = 0;
 
static unsigned char fat_uni2esc[64] = {
    '0', '1', '2', '3', '4', '5', '6', '7',
    '8', '9', 'A', 'B', 'C', 'D', 'E', 'F',
    'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
    'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
    'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
    'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
    'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
    'u', 'v', 'w', 'x', 'y', 'z', '+', '-'
};
 
/* This defines which unicode chars are directly convertable to ISO-8859-1 */
#define UNICODE_CONVERTABLE(cl,ch)  (ch == 0 && (cl < 0x80 || cl >= 0xa0))
 
/* for maxlen param */
#define UNTIL_0     INT_MAX
 
#ifdef __REACTOS__
static void copy_lfn_part(unsigned char *dst, LFN_ENT * lfn);
static char *cnv_unicode(const unsigned char *uni, int maxlen, int use_q);
#endif
 
/* Convert name part in 'lfn' from unicode to ASCII */
#ifndef __REACTOS__
#define CNV_THIS_PART(lfn)              \
    ({                          \
    unsigned char __part_uni[CHARS_PER_LFN*2];      \
    copy_lfn_part( __part_uni, lfn );       \
    cnv_unicode( __part_uni, CHARS_PER_LFN, 0 );    \
    })
#else
static __inline char* CNV_THIS_PART(LFN_ENT * lfn)
{
    unsigned char __part_uni[CHARS_PER_LFN*2];
    copy_lfn_part(__part_uni, lfn);
    return cnv_unicode(__part_uni, CHARS_PER_LFN, 0);
}
#endif
 
/* Convert name parts collected so far (from previous slots) from unicode to
 * ASCII */
#define CNV_PARTS_SO_FAR()                  \
    (cnv_unicode( lfn_unicode+(lfn_slot*CHARS_PER_LFN*2),   \
              lfn_parts*CHARS_PER_LFN, 0 ))
 
#define BYTES_TO_WCHAR(cl,ch) ((wchar_t)((unsigned)(cl) + ((unsigned)(ch) << 8)))
static size_t mbslen(wchar_t x)
{
    wchar_t wstr[] = { x, 0 };
    return wcstombs(NULL, wstr, 0);
}
 
static size_t wctombs(char *dest, wchar_t x)
{
    wchar_t wstr[] = { x, 0 };
    size_t size = wcstombs(NULL, wstr, 0);
    if (size != (size_t) - 1)
    size = wcstombs(dest, wstr, size + 1);
    return size;
}
 
/* This function converts an unicode string to a normal ASCII string, assuming
 * ISO-8859-1 charset. Characters not in 8859-1 are converted to the same
 * escape notation as used by the kernel, i.e. the uuencode-like ":xxx" */
static char *cnv_unicode(const unsigned char *uni, int maxlen, int use_q)
{
    const unsigned char *up;
    unsigned char *out, *cp;
    int len, val;
    size_t x;
 
    for (len = 0, up = uni; (up - uni) / 2 < maxlen && (up[0] || up[1]);
     up += 2) {
    if ((x = mbslen(BYTES_TO_WCHAR(up[0], up[1]))) != (size_t) - 1)
        len += x;
    else if (UNICODE_CONVERTABLE(up[0], up[1]))
        ++len;
    else
        len += 4;
    }
    cp = out = use_q ? qalloc(&mem_queue, len + 1) : alloc(len + 1);
 
    for (up = uni; (up - uni) / 2 < maxlen && (up[0] || up[1]); up += 2) {
    if ((x =
         wctombs((char *)cp, BYTES_TO_WCHAR(up[0], up[1]))) != (size_t) - 1)
        cp += x;
    else if (UNICODE_CONVERTABLE(up[0], up[1]))
        *cp++ = up[0];
    else {
        /* here the same escape notation is used as in the Linux kernel */
        *cp++ = ':';
        val = (up[1] << 8) + up[0];
        cp[2] = fat_uni2esc[val & 0x3f];
        val >>= 6;
        cp[1] = fat_uni2esc[val & 0x3f];
        val >>= 6;
        cp[0] = fat_uni2esc[val & 0x3f];
        cp += 3;
    }
    }
    *cp = 0;
 
    return (char *)out;
}
 
static void copy_lfn_part(unsigned char *dst, LFN_ENT * lfn)
{
    memcpy(dst, lfn->name0_4, 10);
    memcpy(dst + 10, lfn->name5_10, 12);
    memcpy(dst + 22, lfn->name11_12, 4);
}
 
static void clear_lfn_slots(int start, int end)
{
    int i;
    LFN_ENT empty;
 
    /* New dir entry is zeroed except first byte, which is set to 0xe5.
     * This is to avoid that some FAT-reading OSes (not Linux! ;) stop reading
     * a directory at the first zero entry...
     */
    memset(&empty, 0, sizeof(empty));
    empty.id = DELETED_FLAG;
 
    for (i = start; i <= end; ++i) {
    fs_write(lfn_offsets[i], sizeof(LFN_ENT), &empty);
    }
}
 
void lfn_fix_checksum(off_t from, off_t to, const char *short_name)
{
    int i;
    uint8_t sum;
    for (sum = 0, i = 0; i < 11; i++)
    sum = (((sum & 1) << 7) | ((sum & 0xfe) >> 1)) + short_name[i];
 
    for (; from < to; from += sizeof(LFN_ENT)) {
    fs_write(from + offsetof(LFN_ENT, alias_checksum), sizeof(sum), &sum);
    }
}
 
void lfn_reset(void)
{
    if (lfn_unicode)
    free(lfn_unicode);
    lfn_unicode = NULL;
    if (lfn_offsets)
    free(lfn_offsets);
    lfn_offsets = NULL;
    lfn_slot = -1;
}
 
/* This function is only called with de->attr == VFAT_LN_ATTR. It stores part
 * of the long name. */
void lfn_add_slot(DIR_ENT * de, off_t dir_offset)
{
    LFN_ENT *lfn = (LFN_ENT *) de;
    int slot = lfn->id & LFN_ID_SLOTMASK;
    unsigned offset;
 
    if (lfn_slot == 0)
    lfn_check_orphaned();
 
    if (de->attr != VFAT_LN_ATTR)
    die("lfn_add_slot called with non-LFN directory entry");
 
    if (lfn->id & LFN_ID_START && slot != 0) {
    if (lfn_slot != -1) {
        int can_clear = 0;
        /* There is already a LFN "in progess", so it is an error that a
         * new start entry is here. */
        /* Causes: 1) if slot# == expected: start bit set mysteriously, 2)
         *         old LFN overwritten by new one */
        /* Fixes: 1) delete previous LFN 2) if slot# == expected and
         *        checksum ok: clear start bit */
        /* XXX: Should delay that until next LFN known (then can better
         * display the name) */
        printf("A new long file name starts within an old one.\n");
        if (slot == lfn_slot && lfn->alias_checksum == lfn_checksum) {
        char *part1 = CNV_THIS_PART(lfn);
        char *part2 = CNV_PARTS_SO_FAR();
        printf("  It could be that the LFN start bit is wrong here\n"
               "  if \"%s\" seems to match \"%s\".\n", part1, part2);
        free(part1);
        free(part2);
        can_clear = 1;
        }
        if (interactive) {
        printf("1: Delete previous LFN\n2: Leave it as it is.\n");
        if (can_clear)
            printf("3: Clear start bit and concatenate LFNs\n");
        } else
        printf("  Not auto-correcting this.\n");
        if (interactive) {
        switch (get_key(can_clear ? "123" : "12", "?")) {
        case '1':
            clear_lfn_slots(0, lfn_parts - 1);
            lfn_reset();
            break;
        case '2':
            break;
        case '3':
            lfn->id &= ~LFN_ID_START;
            fs_write(dir_offset + offsetof(LFN_ENT, id),
                 sizeof(lfn->id), &lfn->id);
            break;
        }
        }
    }
    lfn_slot = slot;
    lfn_checksum = lfn->alias_checksum;
    lfn_unicode = alloc((lfn_slot * CHARS_PER_LFN + 1) * 2);
    lfn_offsets = alloc(lfn_slot * sizeof(off_t));
    lfn_parts = 0;
    } else if (lfn_slot == -1 && slot != 0) {
    /* No LFN in progress, but slot found; start bit missing */
    /* Causes: 1) start bit got lost, 2) Previous slot with start bit got
     *         lost */
    /* Fixes: 1) delete LFN, 2) set start bit */
    char *part = CNV_THIS_PART(lfn);
    printf("Long filename fragment \"%s\" found outside a LFN "
           "sequence.\n  (Maybe the start bit is missing on the "
           "last fragment)\n", part);
    free(part);
    if (interactive) {
        printf("1: Delete fragment\n2: Leave it as it is.\n"
           "3: Set start bit\n");
    } else
        printf("  Not auto-correcting this.\n");
    switch (interactive ? get_key("123", "?") : '2') {
    case '1':
        if (!lfn_offsets)
        lfn_offsets = alloc(sizeof(off_t));
        lfn_offsets[0] = dir_offset;
        clear_lfn_slots(0, 0);
        lfn_reset();
        return;
    case '2':
        lfn_reset();
        return;
    case '3':
        lfn->id |= LFN_ID_START;
        fs_write(dir_offset + offsetof(LFN_ENT, id),
             sizeof(lfn->id), &lfn->id);
        lfn_slot = slot;
        lfn_checksum = lfn->alias_checksum;
        lfn_unicode = alloc((lfn_slot * CHARS_PER_LFN + 1) * 2);
        lfn_offsets = alloc(lfn_slot * sizeof(off_t));
        lfn_parts = 0;
        break;
    }
    } else if (slot != lfn_slot) {
    /* wrong sequence number */
    /* Causes: 1) seq-no destroyed */
    /* Fixes: 1) delete LFN, 2) fix number (maybe only if following parts
     *        are ok?, maybe only if checksum is ok?) (Attention: space
     *        for name was allocated before!) */
    int can_fix = 0;
    printf("Unexpected long filename sequence number "
           "(%d vs. expected %d).\n", slot, lfn_slot);
    if (lfn->alias_checksum == lfn_checksum && lfn_slot > 0) {
        char *part1 = CNV_THIS_PART(lfn);
        char *part2 = CNV_PARTS_SO_FAR();
        printf("  It could be that just the number is wrong\n"
           "  if \"%s\" seems to match \"%s\".\n", part1, part2);
        free(part1);
        free(part2);
        can_fix = 1;
    }
    if (interactive) {
        printf
        ("1: Delete LFN\n2: Leave it as it is (and ignore LFN so far)\n");
        if (can_fix)
        printf("3: Correct sequence number\n");
    } else
        printf("  Not auto-correcting this.\n");
    switch (interactive ? get_key(can_fix ? "123" : "12", "?") : '2') {
    case '1':
        if (!lfn_offsets) {
        lfn_offsets = alloc(sizeof(off_t));
        lfn_parts = 0;
        }
        lfn_offsets[lfn_parts++] = dir_offset;
        clear_lfn_slots(0, lfn_parts - 1);
        lfn_reset();
        return;
    case '2':
        lfn_reset();
        return;
    case '3':
        lfn->id = (lfn->id & ~LFN_ID_SLOTMASK) | lfn_slot;
        fs_write(dir_offset + offsetof(LFN_ENT, id),
             sizeof(lfn->id), &lfn->id);
        break;
    }
    }
 
    if (lfn->alias_checksum != lfn_checksum) {
    /* checksum mismatch */
    /* Causes: 1) checksum field here destroyed */
    /* Fixes: 1) delete LFN, 2) fix checksum */
    printf("Checksum in long filename part wrong "
           "(%02x vs. expected %02x).\n",
           lfn->alias_checksum, lfn_checksum);
    if (interactive) {
        printf("1: Delete LFN\n2: Leave it as it is.\n"
           "3: Correct checksum\n");
    } else
        printf("  Not auto-correcting this.\n");
    if (interactive) {
        switch (get_key("123", "?")) {
        case '1':
        lfn_offsets[lfn_parts++] = dir_offset;
        clear_lfn_slots(0, lfn_parts - 1);
        lfn_reset();
        return;
        case '2':
        break;
        case '3':
        lfn->alias_checksum = lfn_checksum;
        fs_write(dir_offset + offsetof(LFN_ENT, alias_checksum),
             sizeof(lfn->alias_checksum), &lfn->alias_checksum);
        break;
        }
    }
    }
 
    if (lfn_slot != -1) {
    lfn_slot--;
    offset = lfn_slot * CHARS_PER_LFN * 2;
    copy_lfn_part(lfn_unicode + offset, lfn);
    if (lfn->id & LFN_ID_START)
        lfn_unicode[offset + 26] = lfn_unicode[offset + 27] = 0;
    lfn_offsets[lfn_parts++] = dir_offset;
    }
 
    if (lfn->reserved != 0) {
    printf("Reserved field in VFAT long filename slot is not 0 "
           "(but 0x%02x).\n", lfn->reserved);
    if (interactive)
        printf("1: Fix.\n2: Leave it.\n");
    else
        printf("Auto-setting to 0.\n");
    if (!interactive || get_key("12", "?") == '1') {
        lfn->reserved = 0;
        fs_write(dir_offset + offsetof(LFN_ENT, reserved),
             sizeof(lfn->reserved), &lfn->reserved);
    }
    }
    if (lfn->start != htole16(0)) {
    printf("Start cluster field in VFAT long filename slot is not 0 "
           "(but 0x%04x).\n", lfn->start);
    if (interactive)
        printf("1: Fix.\n2: Leave it.\n");
    else
        printf("Auto-setting to 0.\n");
    if (!interactive || get_key("12", "?") == '1') {
        lfn->start = htole16(0);
        fs_write(dir_offset + offsetof(LFN_ENT, start),
             sizeof(lfn->start), &lfn->start);
    }
    }
}
 
/* This function is always called when de->attr != VFAT_LN_ATTR is found, to
 * retrieve the previously constructed LFN. */
char *lfn_get(DIR_ENT * de, off_t * lfn_offset)
{
    char *lfn;
    uint8_t sum;
    int i;
 
    *lfn_offset = 0;
    if (de->attr == VFAT_LN_ATTR)
    die("lfn_get called with LFN directory entry");
 
#if 0
    if (de->lcase)
    printf("lcase=%02x\n", de->lcase);
#endif
 
    if (lfn_slot == -1)
    /* no long name for this file */
    return NULL;
 
    if (lfn_slot != 0) {
    /* The long name isn't finished yet. */
    /* Causes: 1) LFN slot overwritten by non-VFAT aware tool */
    /* Fixes: 1) delete LFN 2) move overwriting entry to somewhere else
     * and let user enter missing part of LFN (hard to do :-()
     * 3) renumber entries and truncate name */
    char *long_name = CNV_PARTS_SO_FAR();
    char *short_name = file_name(de->name);
    printf("Unfinished long file name \"%s\".\n"
           "  (Start may have been overwritten by %s)\n",
           long_name, short_name);
    free(long_name);
    if (interactive) {
        printf("1: Delete LFN\n2: Leave it as it is.\n"
           "3: Fix numbering (truncates long name and attaches "
           "it to short name %s)\n", short_name);
    } else
        printf("  Not auto-correcting this.\n");
    switch (interactive ? get_key("123", "?") : '2') {
    case '1':
        clear_lfn_slots(0, lfn_parts - 1);
        lfn_reset();
        return NULL;
    case '2':
        lfn_reset();
        return NULL;
    case '3':
        for (i = 0; i < lfn_parts; ++i) {
        uint8_t id = (lfn_parts - i) | (i == 0 ? LFN_ID_START : 0);
        fs_write(lfn_offsets[i] + offsetof(LFN_ENT, id),
             sizeof(id), &id);
        }
        memmove(lfn_unicode, lfn_unicode + lfn_slot * CHARS_PER_LFN * 2,
            lfn_parts * CHARS_PER_LFN * 2);
        break;
    }
    }
 
    for (sum = 0, i = 0; i < MSDOS_NAME; i++)
    sum = (((sum & 1) << 7) | ((sum & 0xfe) >> 1)) + de->name[i];
    if (sum != lfn_checksum) {
    /* checksum doesn't match, long name doesn't apply to this alias */
    /* Causes: 1) alias renamed */
    /* Fixes: 1) Fix checksum in LFN entries */
    char *long_name = CNV_PARTS_SO_FAR();
    char *short_name = file_name(de->name);
    printf("Wrong checksum for long file name \"%s\".\n"
           "  (Short name %s may have changed without updating the long name)\n",
           long_name, short_name);
    free(long_name);
    if (interactive) {
        printf("1: Delete LFN\n2: Leave it as it is.\n"
           "3: Fix checksum (attaches to short name %s)\n", short_name);
    } else
        printf("  Not auto-correcting this.\n");
    if (interactive) {
        switch (get_key("123", "?")) {
        case '1':
        clear_lfn_slots(0, lfn_parts - 1);
        lfn_reset();
        return NULL;
        case '2':
        lfn_reset();
        return NULL;
        case '3':
        for (i = 0; i < lfn_parts; ++i) {
            fs_write(lfn_offsets[i] + offsetof(LFN_ENT, alias_checksum),
                 sizeof(sum), &sum);
        }
        break;
        }
    }
    }
 
    *lfn_offset = lfn_offsets[0];
    lfn = cnv_unicode(lfn_unicode, UNTIL_0, 1);
    lfn_reset();
    return (lfn);
}
 
void lfn_check_orphaned(void)
{
    char *long_name;
 
    if (lfn_slot == -1)
    return;
 
    long_name = CNV_PARTS_SO_FAR();
    printf("Orphaned long file name part \"%s\"\n", long_name);
    free(long_name);
    if (interactive)
    printf("1: Delete.\n2: Leave it.\n");
#ifdef __REACTOS__
    else if (rw)
#else
    else
#endif
    printf("  Auto-deleting.\n");
#ifdef __REACTOS__
    if ((!interactive && rw) || (interactive && get_key("12", "?") == '1')) {
#else
    if (!interactive || get_key("12", "?") == '1') {
#endif
    clear_lfn_slots(0, lfn_parts - 1);
    }
    lfn_reset();
}