fstyp(8): Show exFAT volume labels with -l flag
exfat is fundamentally the same design as fat32. The superblock differs marginally, and there are some additional optional features irrelevant to fstype(8); the structure of dirents has changed slightly to enable, among other things, larger files; the directory entries are no longer DOS 8.3 ASCII or local 8-bit encoding, but instead explicitly UCS-2-LE. (As a result, this change uses iconv to convert a found exfat volume label to the user's locale.) Locating the volume label is identical to FAT32: locate the root directory and walk through dirents until you find a volume label. Like FAT32, follow the FAT chain between root directory clusters as necessary. PR: 242225 Reported by: Victor Sudakov <vas AT sibptus.ru>
This commit is contained in:
cem
parent
9f0058d673
commit
73773fcda9
@ -27,6 +27,14 @@
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/endian.h>
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#include <assert.h>
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#include <err.h>
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#include <errno.h>
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#include <iconv.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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@ -34,6 +42,10 @@ __FBSDID("$FreeBSD$");
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#include "fstyp.h"
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/*
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* https://docs.microsoft.com/en-us/windows/win32/fileio/exfat-specification
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*/
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struct exfat_vbr {
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char ev_jmp[3];
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char ev_fsname[8];
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@ -55,19 +67,300 @@ struct exfat_vbr {
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uint8_t ev_percent_used;
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} __packed;
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struct exfat_dirent {
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uint8_t xde_type;
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#define XDE_TYPE_INUSE_MASK 0x80 /* 1=in use */
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#define XDE_TYPE_INUSE_SHIFT 7
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#define XDE_TYPE_CATEGORY_MASK 0x40 /* 0=primary */
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#define XDE_TYPE_CATEGORY_SHIFT 6
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#define XDE_TYPE_IMPORTNC_MASK 0x20 /* 0=critical */
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#define XDE_TYPE_IMPORTNC_SHIFT 5
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#define XDE_TYPE_CODE_MASK 0x1f
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/* InUse=0, ..., TypeCode=0: EOD. */
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#define XDE_TYPE_EOD 0x00
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#define XDE_TYPE_ALLOC_BITMAP (XDE_TYPE_INUSE_MASK | 0x01)
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#define XDE_TYPE_UPCASE_TABLE (XDE_TYPE_INUSE_MASK | 0x02)
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#define XDE_TYPE_VOL_LABEL (XDE_TYPE_INUSE_MASK | 0x03)
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#define XDE_TYPE_FILE (XDE_TYPE_INUSE_MASK | 0x05)
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#define XDE_TYPE_VOL_GUID (XDE_TYPE_INUSE_MASK | XDE_TYPE_IMPORTNC_MASK)
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#define XDE_TYPE_STREAM_EXT (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK)
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#define XDE_TYPE_FILE_NAME (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | 0x01)
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#define XDE_TYPE_VENDOR (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | XDE_TYPE_IMPORTNC_MASK)
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#define XDE_TYPE_VENDOR_ALLOC (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | XDE_TYPE_IMPORTNC_MASK | 0x01)
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union {
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uint8_t xde_generic_[19];
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struct exde_primary {
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/*
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* Count of "secondary" dirents following this one.
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*
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* A single logical entity may be composed of a
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* sequence of several dirents, starting with a primary
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* one; the rest are secondary dirents.
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*/
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uint8_t xde_secondary_count_;
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uint16_t xde_set_chksum_;
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uint16_t xde_prim_flags_;
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uint8_t xde_prim_generic_[14];
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} __packed xde_primary_;
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struct exde_secondary {
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uint8_t xde_sec_flags_;
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uint8_t xde_sec_generic_[18];
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} __packed xde_secondary_;
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} u;
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uint32_t xde_first_cluster;
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uint64_t xde_data_len;
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} __packed;
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#define xde_generic u.xde_generic_
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#define xde_secondary_count u.xde_primary_.xde_secondary_count
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#define xde_set_chksum u.xde_primary_.xde_set_chksum_
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#define xde_prim_flags u.xde_primary_.xde_prim_flags_
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#define xde_sec_flags u.xde_secondary_.xde_sec_flags_
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_Static_assert(sizeof(struct exfat_dirent) == 32, "spec");
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struct exfat_de_label {
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uint8_t xdel_type; /* XDE_TYPE_VOL_LABEL */
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uint8_t xdel_char_cnt; /* Length of UCS-2 label */
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uint16_t xdel_vol_lbl[11];
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uint8_t xdel_reserved[8];
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} __packed;
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_Static_assert(sizeof(struct exfat_de_label) == 32, "spec");
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#define MAIN_BOOT_REGION_SECT 0
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#define BACKUP_BOOT_REGION_SECT 12
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#define SUBREGION_CHKSUM_SECT 11
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#define FIRST_CLUSTER 2
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#define BAD_BLOCK_SENTINEL 0xfffffff7u
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#define END_CLUSTER_SENTINEL 0xffffffffu
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static inline void *
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read_sectn(FILE *fp, off_t sect, unsigned count, unsigned bytespersec)
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{
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return (read_buf(fp, sect * bytespersec, bytespersec * count));
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}
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static inline void *
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read_sect(FILE *fp, off_t sect, unsigned bytespersec)
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{
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return (read_sectn(fp, sect, 1, bytespersec));
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}
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/*
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* Compute the byte-by-byte multi-sector checksum of the given boot region
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* (MAIN or BACKUP), for a given bytespersec (typically 512 or 4096).
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*
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* Endian-safe; result is host endian.
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*/
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static int
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exfat_compute_boot_chksum(FILE *fp, unsigned region, unsigned bytespersec,
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uint32_t *result)
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{
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unsigned char *sector;
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unsigned n, sect;
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uint32_t checksum;
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checksum = 0;
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for (sect = 0; sect < 11; sect++) {
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sector = read_sect(fp, region + sect, bytespersec);
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if (sector == NULL)
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return (ENXIO);
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for (n = 0; n < bytespersec; n++) {
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if (sect == 0) {
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switch (n) {
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case 106:
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case 107:
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case 112:
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continue;
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}
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}
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checksum = ((checksum & 1) ? 0x80000000u : 0u) +
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(checksum >> 1) + (uint32_t)sector[n];
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}
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free(sector);
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}
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*result = checksum;
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return (0);
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}
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static void
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convert_label(const uint16_t *ucs2label /* LE */, unsigned ucs2len, char
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*label_out, size_t label_sz)
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{
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const char *label;
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char *label_out_orig;
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iconv_t cd;
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size_t srcleft, rc;
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/* Currently hardcoded in fstyp.c as 256 or so. */
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assert(label_sz > 1);
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if (ucs2len == 0) {
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/*
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* Kind of seems bogus, but the spec allows an empty label
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* entry with the same meaning as no label.
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*/
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return;
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}
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if (ucs2len > 11) {
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warnx("exfat: Bogus volume label length: %u", ucs2len);
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return;
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}
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/* dstname="" means convert to the current locale. */
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cd = iconv_open("", EXFAT_ENC);
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if (cd == (iconv_t)-1) {
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warn("exfat: Could not open iconv");
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return;
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}
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label_out_orig = label_out;
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/* Dummy up the byte pointer and byte length iconv's API wants. */
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label = (const void *)ucs2label;
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srcleft = ucs2len * sizeof(*ucs2label);
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rc = iconv(cd, __DECONST(char **, &label), &srcleft, &label_out,
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&label_sz);
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if (rc == (size_t)-1) {
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warn("exfat: iconv()");
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*label_out_orig = '\0';
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} else {
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/* NUL-terminate result (iconv advances label_out). */
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if (label_sz == 0)
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label_out--;
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*label_out = '\0';
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}
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iconv_close(cd);
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}
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/*
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* Using the FAT table, look up the next cluster in this chain.
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*/
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static uint32_t
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exfat_fat_next(FILE *fp, const struct exfat_vbr *ev, unsigned BPS,
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uint32_t cluster)
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{
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uint32_t fat_offset_sect, clsect, clsectoff;
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uint32_t *fatsect, nextclust;
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fat_offset_sect = le32toh(ev->ev_fat_offset);
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clsect = fat_offset_sect + (cluster / (BPS / sizeof(cluster)));
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clsectoff = (cluster % (BPS / sizeof(cluster)));
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/* XXX This is pretty wasteful without a block cache for the FAT. */
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fatsect = read_sect(fp, clsect, BPS);
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nextclust = le32toh(fatsect[clsectoff]);
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free(fatsect);
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return (nextclust);
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}
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static void
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exfat_find_label(FILE *fp, const struct exfat_vbr *ev, unsigned BPS,
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char *label_out, size_t label_sz)
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{
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uint32_t rootdir_cluster, sects_per_clust, cluster_offset_sect;
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off_t rootdir_sect;
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struct exfat_dirent *declust, *it;
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cluster_offset_sect = le32toh(ev->ev_cluster_offset);
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rootdir_cluster = le32toh(ev->ev_rootdir_cluster);
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sects_per_clust = (1u << ev->ev_log_sect_per_clust);
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if (rootdir_cluster < FIRST_CLUSTER) {
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warnx("%s: invalid rootdir cluster %u < %d", __func__,
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rootdir_cluster, FIRST_CLUSTER);
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return;
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}
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for (; rootdir_cluster != END_CLUSTER_SENTINEL;
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rootdir_cluster = exfat_fat_next(fp, ev, BPS, rootdir_cluster)) {
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if (rootdir_cluster == BAD_BLOCK_SENTINEL) {
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warnx("%s: Bogus bad block in root directory chain",
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__func__);
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return;
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}
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rootdir_sect = (rootdir_cluster - FIRST_CLUSTER) *
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sects_per_clust + cluster_offset_sect;
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declust = read_sectn(fp, rootdir_sect, sects_per_clust, BPS);
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for (it = declust;
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it < declust + (sects_per_clust * BPS / sizeof(*it)); it++) {
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bool eod = false;
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/*
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* Simplistic directory traversal; doesn't do any
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* validation of "MUST" requirements in spec.
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*/
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switch (it->xde_type) {
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case XDE_TYPE_EOD:
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eod = true;
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break;
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case XDE_TYPE_VOL_LABEL: {
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struct exfat_de_label *lde = (void*)it;
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convert_label(lde->xdel_vol_lbl,
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lde->xdel_char_cnt, label_out, label_sz);
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free(declust);
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return;
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}
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}
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if (eod)
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break;
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}
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free(declust);
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}
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}
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int
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fstyp_exfat(FILE *fp, char *label, size_t size)
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{
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struct exfat_vbr *ev;
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uint32_t *cksect;
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unsigned bytespersec;
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uint32_t chksum;
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int error;
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cksect = NULL;
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ev = (struct exfat_vbr *)read_buf(fp, 0, 512);
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if (ev == NULL || strncmp(ev->ev_fsname, "EXFAT ", 8) != 0)
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goto fail;
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if (ev->ev_log_bytes_per_sect < 9 || ev->ev_log_bytes_per_sect > 12) {
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warnx("exfat: Invalid BytesPerSectorShift");
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goto done;
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}
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bytespersec = (1u << ev->ev_log_bytes_per_sect);
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error = exfat_compute_boot_chksum(fp, MAIN_BOOT_REGION_SECT,
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bytespersec, &chksum);
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if (error != 0)
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goto done;
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cksect = read_sect(fp, MAIN_BOOT_REGION_SECT + SUBREGION_CHKSUM_SECT,
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bytespersec);
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/*
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* Reading the volume label requires walking the root directory to look
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* for a special label file. Left as an exercise for the reader.
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* Technically the entire sector should be full of repeating 4-byte
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* checksum pattern, but we only verify the first.
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*/
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if (chksum != le32toh(cksect[0])) {
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warnx("exfat: Found checksum 0x%08x != computed 0x%08x",
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le32toh(cksect[0]), chksum);
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goto done;
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}
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if (show_label)
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exfat_find_label(fp, ev, bytespersec, label, size);
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done:
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free(cksect);
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free(ev);
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return (0);
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@ -38,6 +38,8 @@ __FBSDID("$FreeBSD$");
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#include <capsicum_helpers.h>
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#include <err.h>
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#include <errno.h>
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#include <iconv.h>
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#include <locale.h>
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdio.h>
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@ -50,24 +52,27 @@ __FBSDID("$FreeBSD$");
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#define LABEL_LEN 256
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bool show_label = false;
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typedef int (*fstyp_function)(FILE *, char *, size_t);
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static struct {
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const char *name;
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fstyp_function function;
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bool unmountable;
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char *precache_encoding;
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} fstypes[] = {
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{ "cd9660", &fstyp_cd9660, false },
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{ "exfat", &fstyp_exfat, false },
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{ "ext2fs", &fstyp_ext2fs, false },
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{ "geli", &fstyp_geli, true },
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{ "msdosfs", &fstyp_msdosfs, false },
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{ "ntfs", &fstyp_ntfs, false },
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{ "ufs", &fstyp_ufs, false },
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{ "cd9660", &fstyp_cd9660, false, NULL },
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{ "exfat", &fstyp_exfat, false, EXFAT_ENC },
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{ "ext2fs", &fstyp_ext2fs, false, NULL },
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{ "geli", &fstyp_geli, true, NULL },
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{ "msdosfs", &fstyp_msdosfs, false, NULL },
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{ "ntfs", &fstyp_ntfs, false, NULL },
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{ "ufs", &fstyp_ufs, false, NULL },
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#ifdef HAVE_ZFS
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{ "zfs", &fstyp_zfs, true },
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{ "zfs", &fstyp_zfs, true, NULL },
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#endif
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{ NULL, NULL, NULL }
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{ NULL, NULL, NULL, NULL }
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};
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void *
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@ -159,7 +164,7 @@ int
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main(int argc, char **argv)
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{
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int ch, error, i, nbytes;
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bool ignore_type = false, show_label = false, show_unmountable = false;
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bool ignore_type = false, show_unmountable = false;
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char label[LABEL_LEN + 1], strvised[LABEL_LEN * 4 + 1];
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char *path;
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FILE *fp;
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@ -188,6 +193,26 @@ main(int argc, char **argv)
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path = argv[0];
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if (setlocale(LC_CTYPE, "") == NULL)
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err(1, "setlocale");
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caph_cache_catpages();
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/* Cache iconv conversion data before entering capability mode. */
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if (show_label) {
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for (i = 0; i < nitems(fstypes); i++) {
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iconv_t cd;
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if (fstypes[i].precache_encoding == NULL)
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continue;
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cd = iconv_open("", fstypes[i].precache_encoding);
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if (cd == (iconv_t)-1)
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err(1, "%s: iconv_open %s", fstypes[i].name,
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fstypes[i].precache_encoding);
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/* Iconv keeps a small cache of unused encodings. */
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iconv_close(cd);
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}
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}
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fp = fopen(path, "r");
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if (fp == NULL)
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err(1, "%s", path);
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@ -32,8 +32,15 @@
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#ifndef FSTYP_H
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#define FSTYP_H
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#include <stdbool.h>
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#define MIN(a,b) (((a)<(b))?(a):(b))
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/* The spec doesn't seem to permit UTF-16 surrogates; definitely LE. */
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#define EXFAT_ENC "UCS-2LE"
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extern bool show_label; /* -l flag */
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void *read_buf(FILE *fp, off_t off, size_t len);
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char *checked_strdup(const char *s);
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void rtrim(char *label, size_t size);
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@ -68,6 +68,15 @@ exfat_body() {
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atf_check -s exit:0 -o inline:"exfat\n" fstyp -u exfat.img
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}
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atf_test_case exfat_label
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exfat_label_head() {
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atf_set "descr" "fstyp(8) can read exFAT labels"
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}
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exfat_label_body() {
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bzcat $(atf_get_srcdir)/dfr-01-xfat.img.bz2 > exfat.img
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atf_check -s exit:0 -o inline:"exfat exFat\n" fstyp -u -l exfat.img
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}
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atf_test_case empty
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empty_head() {
|
||||
atf_set "descr" "fstyp(8) should fail on an empty file"
|
||||
@ -253,6 +262,7 @@ atf_init_test_cases() {
|
||||
atf_add_test_case dir
|
||||
atf_add_test_case empty
|
||||
atf_add_test_case exfat
|
||||
atf_add_test_case exfat_label
|
||||
atf_add_test_case ext2
|
||||
atf_add_test_case ext3
|
||||
atf_add_test_case ext4
|
||||
|
||||
Loading…
Reference in New Issue
Block a user