Attachment 209495 Details for Bug 242225 – Fixes the bug and adds matching test case

[patch] Fixes the bug and adds matching test case

fstyp_exfat_label.patch (text/plain), 13.74 KB, created by Conrad Meyer on 2019-11-27 20:52:14 UTC

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Creator: Conrad Meyer

Created: 2019-11-27 20:52:14 UTC

Size: 13.74 KB

patch

obsolete

>From 6fb69526612904b61f6f6d07eb84c4968d13a37a Mon Sep 17 00:00:00 2001
>From: Conrad Meyer <cem@FreeBSD.org>
>Date: Wed, 27 Nov 2019 12:40:18 -0800
>Subject: [PATCH] fstyp(8): Read exFAT volume labels
>
>The superblock is slightly different from FAT32 and the dirent structure is
>a little different, but basically it's the same process: find the root
>directory data cluster, walk it (including chasing the FAT chain for the
>next data cluster if needed) until we find the special dirent indicating a
>volume label, and then return it to the generic fstyp code.
>
>Unlike msdosfs, exFAT labels are UCS-2LE, so this change uses iconv to
>convert it to the user's locale.
>
>It isn't clear to me if any of it is covered by the OIN (previously:
>Microsoft) patents on exFAT, as I have no familiarity with them.
>If one squints a little and considers 'fstyp' a Linux Component (OIN term),
>the patent coverage might not be an issue.  (fstyp could easily run on a
>Linux System with a Linux Kernel.)
>---
> usr.sbin/fstyp/exfat.c             | 290 ++++++++++++++++++++++++++++-
> usr.sbin/fstyp/fstyp.c             |  41 +++-
> usr.sbin/fstyp/fstyp.h             |   2 +
> usr.sbin/fstyp/tests/fstyp_test.sh |  10 +
> 4 files changed, 332 insertions(+), 11 deletions(-)
>
>diff --git a/usr.sbin/fstyp/exfat.c b/usr.sbin/fstyp/exfat.c
>index 9c379df0c3f6..d2bbc53e4654 100644
>--- a/usr.sbin/fstyp/exfat.c
>+++ b/usr.sbin/fstyp/exfat.c
>@@ -25,17 +25,29 @@
>  */
> 
> #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>
> #include <string.h>
> 
> #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];
> 	char		ev_zeros[53];
> 	uint64_t	ev_part_offset;
>@@ -53,23 +65,297 @@ struct exfat_vbr {
> 	uint8_t		ev_num_fats;
> 	uint8_t		ev_drive_sel;
> 	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 {
>+			// XXX: count of following dirents, "secondary"
>+			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 fstype.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;
>+	}
>+
>+	exfat_find_label(fp, ev, bytespersec, label, size);
>+
>+done:
>+	free(cksect);
> 	free(ev);
> 	return (0);
> 
> fail:
> 	free(ev);
>diff --git a/usr.sbin/fstyp/fstyp.c b/usr.sbin/fstyp/fstyp.c
>index 31f7b34bde40..dabaf1c88bb2 100644
>--- a/usr.sbin/fstyp/fstyp.c
>+++ b/usr.sbin/fstyp/fstyp.c
>@@ -36,10 +36,12 @@ __FBSDID("$FreeBSD$");
> #include <sys/ioctl.h>
> #include <sys/stat.h>
> #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>
> #include <stdlib.h>
> #include <string.h>
>@@ -54,22 +56,23 @@ 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 *
> read_buf(FILE *fp, off_t off, size_t len)
> {
>@@ -186,10 +189,30 @@ main(int argc, char **argv)
> 	if (argc != 1)
> 		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)
> 		err(1, "%s", path);
> 
> 	if (caph_enter() < 0)
>diff --git a/usr.sbin/fstyp/fstyp.h b/usr.sbin/fstyp/fstyp.h
>index f858b0c53827..b3be13235d22 100644
>--- a/usr.sbin/fstyp/fstyp.h
>+++ b/usr.sbin/fstyp/fstyp.h
>@@ -31,10 +31,12 @@
> 
> #ifndef FSTYP_H
> #define	FSTYP_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"
> 
> void	*read_buf(FILE *fp, off_t off, size_t len);
> char	*checked_strdup(const char *s);
> void	rtrim(char *label, size_t size);
> 
>diff --git a/usr.sbin/fstyp/tests/fstyp_test.sh b/usr.sbin/fstyp/tests/fstyp_test.sh
>index 5103ba042746..c6f35dda38c4 100755
>--- a/usr.sbin/fstyp/tests/fstyp_test.sh
>+++ b/usr.sbin/fstyp/tests/fstyp_test.sh
>@@ -66,10 +66,19 @@ exfat_head() {
> exfat_body() {
> 	bzcat $(atf_get_srcdir)/dfr-01-xfat.img.bz2 > exfat.img
> 	atf_check -s exit:0 -o inline:"exfat\n" fstyp -u exfat.img
> }
> 
>+atf_test_case exfat_label
>+exfat_head() {
>+	atf_set "descr" "fstyp(8) can read exFAT labels"
>+}
>+exfat_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"
> }
> empty_body() {
>@@ -251,10 +260,11 @@ atf_init_test_cases() {
> 	atf_add_test_case cd9660
> 	atf_add_test_case cd9660_label
> 	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
> 	atf_add_test_case ext4_label
> 	atf_add_test_case fat12
>-- 
>2.23.0
>

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Attachments on bug 242225: 209495 | 209496