Skip site navigation (1)Skip section navigation (2)
Date:      Sun, 22 Dec 2019 03:19:17 +0000 (UTC)
From:      Conrad Meyer <cem@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r355996 - in head/usr.sbin/fstyp: . tests
Message-ID:  <201912220319.xBM3JHPu058403@repo.freebsd.org>

next in thread | raw e-mail | index | archive | help
Author: cem
Date: Sun Dec 22 03:19:17 2019
New Revision: 355996
URL: https://svnweb.freebsd.org/changeset/base/355996

Log:
  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>

Modified:
  head/usr.sbin/fstyp/exfat.c
  head/usr.sbin/fstyp/fstyp.c
  head/usr.sbin/fstyp/fstyp.h
  head/usr.sbin/fstyp/tests/fstyp_test.sh

Modified: head/usr.sbin/fstyp/exfat.c
==============================================================================
--- head/usr.sbin/fstyp/exfat.c	Sun Dec 22 01:22:51 2019	(r355995)
+++ head/usr.sbin/fstyp/exfat.c	Sun Dec 22 03:19:17 2019	(r355996)
@@ -27,6 +27,14 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <sys/param.h>
+#include <sys/endian.h>
+
+#include <assert.h>
+#include <err.h>
+#include <errno.h>
+#include <iconv.h>
+#include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -34,6 +42,10 @@ __FBSDID("$FreeBSD$");
 
 #include "fstyp.h"
 
+/*
+ * https://docs.microsoft.com/en-us/windows/win32/fileio/exfat-specification
+ */
+
 struct exfat_vbr {
 	char		ev_jmp[3];
 	char		ev_fsname[8];
@@ -55,19 +67,300 @@ struct exfat_vbr {
 	uint8_t		ev_percent_used;
 } __packed;
 
+struct exfat_dirent {
+	uint8_t		xde_type;
+#define	XDE_TYPE_INUSE_MASK	0x80	/* 1=in use */
+#define	XDE_TYPE_INUSE_SHIFT	7
+#define	XDE_TYPE_CATEGORY_MASK	0x40	/* 0=primary */
+#define	XDE_TYPE_CATEGORY_SHIFT	6
+#define	XDE_TYPE_IMPORTNC_MASK	0x20	/* 0=critical */
+#define	XDE_TYPE_IMPORTNC_SHIFT	5
+#define	XDE_TYPE_CODE_MASK	0x1f
+/* InUse=0, ..., TypeCode=0: EOD. */
+#define	XDE_TYPE_EOD		0x00
+#define	XDE_TYPE_ALLOC_BITMAP	(XDE_TYPE_INUSE_MASK | 0x01)
+#define	XDE_TYPE_UPCASE_TABLE	(XDE_TYPE_INUSE_MASK | 0x02)
+#define	XDE_TYPE_VOL_LABEL	(XDE_TYPE_INUSE_MASK | 0x03)
+#define	XDE_TYPE_FILE		(XDE_TYPE_INUSE_MASK | 0x05)
+#define	XDE_TYPE_VOL_GUID	(XDE_TYPE_INUSE_MASK | XDE_TYPE_IMPORTNC_MASK)
+#define	XDE_TYPE_STREAM_EXT	(XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK)
+#define	XDE_TYPE_FILE_NAME	(XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | 0x01)
+#define	XDE_TYPE_VENDOR		(XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | XDE_TYPE_IMPORTNC_MASK)
+#define	XDE_TYPE_VENDOR_ALLOC	(XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | XDE_TYPE_IMPORTNC_MASK | 0x01)
+	union {
+		uint8_t	xde_generic_[19];
+		struct exde_primary {
+			/*
+			 * Count of "secondary" dirents following this one.
+			 *
+			 * A single logical entity may be composed of a
+			 * sequence of several dirents, starting with a primary
+			 * one; the rest are secondary dirents.
+			 */
+			uint8_t		xde_secondary_count_;
+			uint16_t	xde_set_chksum_;
+			uint16_t	xde_prim_flags_;
+			uint8_t		xde_prim_generic_[14];
+		} __packed xde_primary_;
+		struct exde_secondary {
+			uint8_t		xde_sec_flags_;
+			uint8_t		xde_sec_generic_[18];
+		} __packed xde_secondary_;
+	} u;
+	uint32_t	xde_first_cluster;
+	uint64_t	xde_data_len;
+} __packed;
+#define	xde_generic		u.xde_generic_
+#define	xde_secondary_count	u.xde_primary_.xde_secondary_count
+#define	xde_set_chksum		u.xde_primary_.xde_set_chksum_
+#define	xde_prim_flags		u.xde_primary_.xde_prim_flags_
+#define	xde_sec_flags		u.xde_secondary_.xde_sec_flags_
+_Static_assert(sizeof(struct exfat_dirent) == 32, "spec");
+
+struct exfat_de_label {
+	uint8_t		xdel_type;	/* XDE_TYPE_VOL_LABEL */
+	uint8_t		xdel_char_cnt;	/* Length of UCS-2 label */
+	uint16_t	xdel_vol_lbl[11];
+	uint8_t		xdel_reserved[8];
+} __packed;
+_Static_assert(sizeof(struct exfat_de_label) == 32, "spec");
+
+#define	MAIN_BOOT_REGION_SECT	0
+#define	BACKUP_BOOT_REGION_SECT	12
+
+#define	SUBREGION_CHKSUM_SECT	11
+
+#define	FIRST_CLUSTER		2
+#define	BAD_BLOCK_SENTINEL	0xfffffff7u
+#define	END_CLUSTER_SENTINEL	0xffffffffu
+
+static inline void *
+read_sectn(FILE *fp, off_t sect, unsigned count, unsigned bytespersec)
+{
+	return (read_buf(fp, sect * bytespersec, bytespersec * count));
+}
+
+static inline void *
+read_sect(FILE *fp, off_t sect, unsigned bytespersec)
+{
+	return (read_sectn(fp, sect, 1, bytespersec));
+}
+
+/*
+ * Compute the byte-by-byte multi-sector checksum of the given boot region
+ * (MAIN or BACKUP), for a given bytespersec (typically 512 or 4096).
+ *
+ * Endian-safe; result is host endian.
+ */
+static int
+exfat_compute_boot_chksum(FILE *fp, unsigned region, unsigned bytespersec,
+    uint32_t *result)
+{
+	unsigned char *sector;
+	unsigned n, sect;
+	uint32_t checksum;
+
+	checksum = 0;
+	for (sect = 0; sect < 11; sect++) {
+		sector = read_sect(fp, region + sect, bytespersec);
+		if (sector == NULL)
+			return (ENXIO);
+		for (n = 0; n < bytespersec; n++) {
+			if (sect == 0) {
+				switch (n) {
+				case 106:
+				case 107:
+				case 112:
+					continue;
+				}
+			}
+			checksum = ((checksum & 1) ? 0x80000000u : 0u) +
+			    (checksum >> 1) + (uint32_t)sector[n];
+		}
+		free(sector);
+	}
+
+	*result = checksum;
+	return (0);
+}
+
+static void
+convert_label(const uint16_t *ucs2label /* LE */, unsigned ucs2len, char
+    *label_out, size_t label_sz)
+{
+	const char *label;
+	char *label_out_orig;
+	iconv_t cd;
+	size_t srcleft, rc;
+
+	/* Currently hardcoded in fstyp.c as 256 or so. */
+	assert(label_sz > 1);
+
+	if (ucs2len == 0) {
+		/*
+		 * Kind of seems bogus, but the spec allows an empty label
+		 * entry with the same meaning as no label.
+		 */
+		return;
+	}
+
+	if (ucs2len > 11) {
+		warnx("exfat: Bogus volume label length: %u", ucs2len);
+		return;
+	}
+
+	/* dstname="" means convert to the current locale. */
+	cd = iconv_open("", EXFAT_ENC);
+	if (cd == (iconv_t)-1) {
+		warn("exfat: Could not open iconv");
+		return;
+	}
+
+	label_out_orig = label_out;
+
+	/* Dummy up the byte pointer and byte length iconv's API wants. */
+	label = (const void *)ucs2label;
+	srcleft = ucs2len * sizeof(*ucs2label);
+
+	rc = iconv(cd, __DECONST(char **, &label), &srcleft, &label_out,
+	    &label_sz);
+	if (rc == (size_t)-1) {
+		warn("exfat: iconv()");
+		*label_out_orig = '\0';
+	} else {
+		/* NUL-terminate result (iconv advances label_out). */
+		if (label_sz == 0)
+			label_out--;
+		*label_out = '\0';
+	}
+
+	iconv_close(cd);
+}
+
+/*
+ * Using the FAT table, look up the next cluster in this chain.
+ */
+static uint32_t
+exfat_fat_next(FILE *fp, const struct exfat_vbr *ev, unsigned BPS,
+    uint32_t cluster)
+{
+	uint32_t fat_offset_sect, clsect, clsectoff;
+	uint32_t *fatsect, nextclust;
+
+	fat_offset_sect = le32toh(ev->ev_fat_offset);
+	clsect = fat_offset_sect + (cluster / (BPS / sizeof(cluster)));
+	clsectoff = (cluster % (BPS / sizeof(cluster)));
+
+	/* XXX This is pretty wasteful without a block cache for the FAT. */
+	fatsect = read_sect(fp, clsect, BPS);
+	nextclust = le32toh(fatsect[clsectoff]);
+	free(fatsect);
+
+	return (nextclust);
+}
+
+static void
+exfat_find_label(FILE *fp, const struct exfat_vbr *ev, unsigned BPS,
+    char *label_out, size_t label_sz)
+{
+	uint32_t rootdir_cluster, sects_per_clust, cluster_offset_sect;
+	off_t rootdir_sect;
+	struct exfat_dirent *declust, *it;
+
+	cluster_offset_sect = le32toh(ev->ev_cluster_offset);
+	rootdir_cluster = le32toh(ev->ev_rootdir_cluster);
+	sects_per_clust = (1u << ev->ev_log_sect_per_clust);
+
+	if (rootdir_cluster < FIRST_CLUSTER) {
+		warnx("%s: invalid rootdir cluster %u < %d", __func__,
+		    rootdir_cluster, FIRST_CLUSTER);
+		return;
+	}
+
+
+	for (; rootdir_cluster != END_CLUSTER_SENTINEL;
+	    rootdir_cluster = exfat_fat_next(fp, ev, BPS, rootdir_cluster)) {
+		if (rootdir_cluster == BAD_BLOCK_SENTINEL) {
+			warnx("%s: Bogus bad block in root directory chain",
+			    __func__);
+			return;
+		}
+
+		rootdir_sect = (rootdir_cluster - FIRST_CLUSTER) *
+		    sects_per_clust + cluster_offset_sect;
+		declust = read_sectn(fp, rootdir_sect, sects_per_clust, BPS);
+		for (it = declust;
+		    it < declust + (sects_per_clust * BPS / sizeof(*it)); it++) {
+			bool eod = false;
+
+			/*
+			 * Simplistic directory traversal; doesn't do any
+			 * validation of "MUST" requirements in spec.
+			 */
+			switch (it->xde_type) {
+			case XDE_TYPE_EOD:
+				eod = true;
+				break;
+			case XDE_TYPE_VOL_LABEL: {
+				struct exfat_de_label *lde = (void*)it;
+				convert_label(lde->xdel_vol_lbl,
+				    lde->xdel_char_cnt, label_out, label_sz);
+				free(declust);
+				return;
+				}
+			}
+
+			if (eod)
+				break;
+		}
+		free(declust);
+	}
+}
+
 int
 fstyp_exfat(FILE *fp, char *label, size_t size)
 {
 	struct exfat_vbr *ev;
+	uint32_t *cksect;
+	unsigned bytespersec;
+	uint32_t chksum;
+	int error;
 
+	cksect = NULL;
 	ev = (struct exfat_vbr *)read_buf(fp, 0, 512);
 	if (ev == NULL || strncmp(ev->ev_fsname, "EXFAT   ", 8) != 0)
 		goto fail;
 
+	if (ev->ev_log_bytes_per_sect < 9 || ev->ev_log_bytes_per_sect > 12) {
+		warnx("exfat: Invalid BytesPerSectorShift");
+		goto done;
+	}
+
+	bytespersec = (1u << ev->ev_log_bytes_per_sect);
+
+	error = exfat_compute_boot_chksum(fp, MAIN_BOOT_REGION_SECT,
+	    bytespersec, &chksum);
+	if (error != 0)
+		goto done;
+
+	cksect = read_sect(fp, MAIN_BOOT_REGION_SECT + SUBREGION_CHKSUM_SECT,
+	    bytespersec);
+
 	/*
-	 * Reading the volume label requires walking the root directory to look
-	 * for a special label file.  Left as an exercise for the reader.
+	 * Technically the entire sector should be full of repeating 4-byte
+	 * checksum pattern, but we only verify the first.
 	 */
+	if (chksum != le32toh(cksect[0])) {
+		warnx("exfat: Found checksum 0x%08x != computed 0x%08x",
+		    le32toh(cksect[0]), chksum);
+		goto done;
+	}
+
+	if (show_label)
+		exfat_find_label(fp, ev, bytespersec, label, size);
+
+done:
+	free(cksect);
 	free(ev);
 	return (0);
 

Modified: head/usr.sbin/fstyp/fstyp.c
==============================================================================
--- head/usr.sbin/fstyp/fstyp.c	Sun Dec 22 01:22:51 2019	(r355995)
+++ head/usr.sbin/fstyp/fstyp.c	Sun Dec 22 03:19:17 2019	(r355996)
@@ -38,6 +38,8 @@ __FBSDID("$FreeBSD$");
 #include <capsicum_helpers.h>
 #include <err.h>
 #include <errno.h>
+#include <iconv.h>
+#include <locale.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdio.h>
@@ -50,24 +52,27 @@ __FBSDID("$FreeBSD$");
 
 #define	LABEL_LEN	256
 
+bool show_label = false;
+
 typedef int (*fstyp_function)(FILE *, char *, size_t);
 
 static struct {
 	const char	*name;
 	fstyp_function	function;
 	bool		unmountable;
+	char		*precache_encoding;
 } fstypes[] = {
-	{ "cd9660", &fstyp_cd9660, false },
-	{ "exfat", &fstyp_exfat, false },
-	{ "ext2fs", &fstyp_ext2fs, false },
-	{ "geli", &fstyp_geli, true },
-	{ "msdosfs", &fstyp_msdosfs, false },
-	{ "ntfs", &fstyp_ntfs, false },
-	{ "ufs", &fstyp_ufs, false },
+	{ "cd9660", &fstyp_cd9660, false, NULL },
+	{ "exfat", &fstyp_exfat, false, EXFAT_ENC },
+	{ "ext2fs", &fstyp_ext2fs, false, NULL },
+	{ "geli", &fstyp_geli, true, NULL },
+	{ "msdosfs", &fstyp_msdosfs, false, NULL },
+	{ "ntfs", &fstyp_ntfs, false, NULL },
+	{ "ufs", &fstyp_ufs, false, NULL },
 #ifdef HAVE_ZFS
-	{ "zfs", &fstyp_zfs, true },
+	{ "zfs", &fstyp_zfs, true, NULL },
 #endif
-	{ NULL, NULL, NULL }
+	{ NULL, NULL, NULL, NULL }
 };
 
 void *
@@ -159,7 +164,7 @@ int
 main(int argc, char **argv)
 {
 	int ch, error, i, nbytes;
-	bool ignore_type = false, show_label = false, show_unmountable = false;
+	bool ignore_type = false, show_unmountable = false;
 	char label[LABEL_LEN + 1], strvised[LABEL_LEN * 4 + 1];
 	char *path;
 	FILE *fp;
@@ -187,6 +192,26 @@ main(int argc, char **argv)
 		usage();
 
 	path = argv[0];
+
+	if (setlocale(LC_CTYPE, "") == NULL)
+		err(1, "setlocale");
+	caph_cache_catpages();
+
+	/* Cache iconv conversion data before entering capability mode. */
+	if (show_label) {
+		for (i = 0; i < nitems(fstypes); i++) {
+			iconv_t cd;
+
+			if (fstypes[i].precache_encoding == NULL)
+				continue;
+			cd = iconv_open("", fstypes[i].precache_encoding);
+			if (cd == (iconv_t)-1)
+				err(1, "%s: iconv_open %s", fstypes[i].name,
+				    fstypes[i].precache_encoding);
+			/* Iconv keeps a small cache of unused encodings. */
+			iconv_close(cd);
+		}
+	}
 
 	fp = fopen(path, "r");
 	if (fp == NULL)

Modified: head/usr.sbin/fstyp/fstyp.h
==============================================================================
--- head/usr.sbin/fstyp/fstyp.h	Sun Dec 22 01:22:51 2019	(r355995)
+++ head/usr.sbin/fstyp/fstyp.h	Sun Dec 22 03:19:17 2019	(r355996)
@@ -32,7 +32,14 @@
 #ifndef FSTYP_H
 #define	FSTYP_H
 
+#include <stdbool.h>
+
 #define	MIN(a,b) (((a)<(b))?(a):(b))
+
+/* The spec doesn't seem to permit UTF-16 surrogates; definitely LE. */
+#define	EXFAT_ENC	"UCS-2LE"
+
+extern bool	show_label;	/* -l flag */
 
 void	*read_buf(FILE *fp, off_t off, size_t len);
 char	*checked_strdup(const char *s);

Modified: head/usr.sbin/fstyp/tests/fstyp_test.sh
==============================================================================
--- head/usr.sbin/fstyp/tests/fstyp_test.sh	Sun Dec 22 01:22:51 2019	(r355995)
+++ head/usr.sbin/fstyp/tests/fstyp_test.sh	Sun Dec 22 03:19:17 2019	(r355996)
@@ -68,6 +68,15 @@ exfat_body() {
 	atf_check -s exit:0 -o inline:"exfat\n" fstyp -u exfat.img
 }
 
+atf_test_case exfat_label
+exfat_label_head() {
+	atf_set "descr" "fstyp(8) can read exFAT labels"
+}
+exfat_label_body() {
+	bzcat $(atf_get_srcdir)/dfr-01-xfat.img.bz2 > exfat.img
+	atf_check -s exit:0 -o inline:"exfat exFat\n" fstyp -u -l exfat.img
+}
+
 atf_test_case empty
 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



Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201912220319.xBM3JHPu058403>