1 files changed, 427 insertions, 0 deletions

diff --git a/libblkid/vfat.c b/libblkid/vfat.c
new file mode 100644
index 000000000..2feb818a9
--- /dev/null
+++ b/libblkid/vfat.c
@@ -0,0 +1,427 @@
+/*
+ * Copyright (C) 1999 by Andries Brouwer
+ * Copyright (C) 1999, 2000, 2003 by Theodore Ts'o
+ * Copyright (C) 2001 by Andreas Dilger
+ * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
+ * Copyright (C) 2008 Karel Zak <kzak@redhat.com>
+ *
+ * This file may be redistributed under the terms of the
+ * GNU Lesser General Public License.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <ctype.h>
+#include <stdint.h>
+
+#include "superblocks.h"
+
+/* Yucky misaligned values */
+struct vfat_super_block {
+/* 00*/	unsigned char	vs_ignored[3];
+/* 03*/	unsigned char	vs_sysid[8];
+/* 0b*/	unsigned char	vs_sector_size[2];
+/* 0d*/	uint8_t		vs_cluster_size;
+/* 0e*/	uint16_t	vs_reserved;
+/* 10*/	uint8_t		vs_fats;
+/* 11*/	unsigned char	vs_dir_entries[2];
+/* 13*/	unsigned char	vs_sectors[2];
+/* 15*/	unsigned char	vs_media;
+/* 16*/	uint16_t	vs_fat_length;
+/* 18*/	uint16_t	vs_secs_track;
+/* 1a*/	uint16_t	vs_heads;
+/* 1c*/	uint32_t	vs_hidden;
+/* 20*/	uint32_t	vs_total_sect;
+/* 24*/	uint32_t	vs_fat32_length;
+/* 28*/	uint16_t	vs_flags;
+/* 2a*/	uint8_t		vs_version[2];
+/* 2c*/	uint32_t	vs_root_cluster;
+/* 30*/	uint16_t	vs_fsinfo_sector;
+/* 32*/	uint16_t	vs_backup_boot;
+/* 34*/	uint16_t	vs_reserved2[6];
+/* 40*/	unsigned char	vs_unknown[3];
+/* 43*/	unsigned char	vs_serno[4];
+/* 47*/	unsigned char	vs_label[11];
+/* 52*/	unsigned char   vs_magic[8];
+/* 5a*/	unsigned char	vs_dummy2[0x1fe - 0x5a];
+/*1fe*/	unsigned char	vs_pmagic[2];
+} __attribute__((packed));
+
+/* Yucky misaligned values */
+struct msdos_super_block {
+/* 00*/	unsigned char	ms_ignored[3];
+/* 03*/	unsigned char	ms_sysid[8];
+/* 0b*/	unsigned char	ms_sector_size[2];
+/* 0d*/	uint8_t		ms_cluster_size;
+/* 0e*/	uint16_t	ms_reserved;
+/* 10*/	uint8_t		ms_fats;
+/* 11*/	unsigned char	ms_dir_entries[2];
+/* 13*/	unsigned char	ms_sectors[2]; /* =0 iff V3 or later */
+/* 15*/	unsigned char	ms_media;
+/* 16*/	uint16_t	ms_fat_length; /* Sectors per FAT */
+/* 18*/	uint16_t	ms_secs_track;
+/* 1a*/	uint16_t	ms_heads;
+/* 1c*/	uint32_t	ms_hidden;
+/* V3 BPB */
+/* 20*/	uint32_t	ms_total_sect; /* iff ms_sectors == 0 */
+/* V4 BPB */
+/* 24*/	unsigned char	ms_unknown[3]; /* Phys drive no., resvd, V4 sig (0x29) */
+/* 27*/	unsigned char	ms_serno[4];
+/* 2b*/	unsigned char	ms_label[11];
+/* 36*/	unsigned char   ms_magic[8];
+/* 3e*/	unsigned char	ms_dummy2[0x1fe - 0x3e];
+/*1fe*/	unsigned char	ms_pmagic[2];
+} __attribute__((packed));
+
+struct vfat_dir_entry {
+	uint8_t		name[11];
+	uint8_t		attr;
+	uint16_t	time_creat;
+	uint16_t	date_creat;
+	uint16_t	time_acc;
+	uint16_t	date_acc;
+	uint16_t	cluster_high;
+	uint16_t	time_write;
+	uint16_t	date_write;
+	uint16_t	cluster_low;
+	uint32_t	size;
+} __attribute__((packed));
+
+struct fat32_fsinfo {
+	uint8_t signature1[4];
+	uint32_t reserved1[120];
+	uint8_t signature2[4];
+	uint32_t free_clusters;
+	uint32_t next_cluster;
+	uint32_t reserved2[4];
+} __attribute__((packed));
+
+/* maximum number of clusters */
+#define FAT12_MAX 0xFF4
+#define FAT16_MAX 0xFFF4
+#define FAT32_MAX 0x0FFFFFF6
+
+#define FAT_ATTR_VOLUME_ID		0x08
+#define FAT_ATTR_DIR			0x10
+#define FAT_ATTR_LONG_NAME		0x0f
+#define FAT_ATTR_MASK			0x3f
+#define FAT_ENTRY_FREE			0xe5
+
+static const char *no_name = "NO NAME    ";
+
+#define unaligned_le16(x) \
+		(((unsigned char *) x)[0] + (((unsigned char *) x)[1] << 8))
+
+/*
+ * Look for LABEL (name) in the FAT root directory.
+ */
+static unsigned char *search_fat_label(blkid_probe pr,
+				uint64_t offset, uint32_t entries)
+{
+	struct vfat_dir_entry *ent, *dir = NULL;
+	uint32_t i;
+
+	DBG(DEBUG_LOWPROBE,
+		printf("\tlook for label in root-dir "
+			"(entries: %d, offset: %jd)\n", entries, offset));
+
+	if (!blkid_probe_is_tiny(pr)) {
+		/* large disk, read whole root directory */
+		dir = (struct vfat_dir_entry *)
+			blkid_probe_get_buffer(pr,
+					offset,
+					(blkid_loff_t) entries *
+						sizeof(struct vfat_dir_entry));
+		if (!dir)
+			return NULL;
+	}
+
+	for (i = 0; i < entries; i++) {
+		/*
+		 * The root directory could be relatively large (4-16kB).
+		 * Fortunately, the LABEL is usually the first entry in the
+		 * directory. On tiny disks we call read() per entry.
+		 */
+		if (!dir)
+			ent = (struct vfat_dir_entry *)
+				blkid_probe_get_buffer(pr,
+					(blkid_loff_t) offset + (i *
+						sizeof(struct vfat_dir_entry)),
+					sizeof(struct vfat_dir_entry));
+		else
+			ent = &dir[i];
+
+		if (!ent || ent->name[0] == 0x00)
+			break;
+
+		if ((ent->name[0] == FAT_ENTRY_FREE) ||
+		    (ent->cluster_high != 0 || ent->cluster_low != 0) ||
+		    ((ent->attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME))
+			continue;
+
+		if ((ent->attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) ==
+		    FAT_ATTR_VOLUME_ID) {
+			DBG(DEBUG_LOWPROBE,
+				printf("\tfound fs LABEL at entry %d\n", i));
+			return ent->name;
+		}
+	}
+	return NULL;
+}
+
+static int fat_valid_superblock(const struct blkid_idmag *mag,
+			struct msdos_super_block *ms,
+			struct vfat_super_block *vs,
+			uint32_t *cluster_count, uint32_t *fat_size)
+{
+	uint16_t sector_size, dir_entries, reserved;
+	uint32_t sect_count, __fat_size, dir_size, __cluster_count, fat_length;
+	uint32_t max_count;
+
+	/* extra check for FATs without magic strings */
+	if (mag->len <= 2) {
+		/* Old floppies have a valid MBR signature */
+		if (ms->ms_pmagic[0] != 0x55 || ms->ms_pmagic[1] != 0xAA)
+			return 0;
+
+		/*
+		 * OS/2 and apparently DFSee will place a FAT12/16-like
+		 * pseudo-superblock in the first 512 bytes of non-FAT
+		 * filesystems --- at least JFS and HPFS, and possibly others.
+		 * So we explicitly check for those filesystems at the
+		 * FAT12/16 filesystem magic field identifier, and if they are
+		 * present, we rule this out as a FAT filesystem, despite the
+		 * FAT-like pseudo-header.
+		 */
+		if ((memcmp(ms->ms_magic, "JFS     ", 8) == 0) ||
+		    (memcmp(ms->ms_magic, "HPFS    ", 8) == 0))
+			return 0;
+	}
+
+	/* fat counts(Linux kernel expects at least 1 FAT table) */
+	if (!ms->ms_fats)
+		return 0;
+	if (!ms->ms_reserved)
+		return 0;
+	if (!(0xf8 <= ms->ms_media || ms->ms_media == 0xf0))
+		return 0;
+	if (!is_power_of_2(ms->ms_cluster_size))
+		return 0;
+
+	sector_size = unaligned_le16(&ms->ms_sector_size);
+	if (!is_power_of_2(sector_size) ||
+	    sector_size < 512 || sector_size > 4096)
+		return 0;
+
+	dir_entries = unaligned_le16(&ms->ms_dir_entries);
+	reserved =  le16_to_cpu(ms->ms_reserved);
+	sect_count = unaligned_le16(&ms->ms_sectors);
+
+	if (sect_count == 0)
+		sect_count = le32_to_cpu(ms->ms_total_sect);
+
+	fat_length = le16_to_cpu(ms->ms_fat_length);
+	if (fat_length == 0)
+		fat_length = le32_to_cpu(vs->vs_fat32_length);
+
+	__fat_size = fat_length * ms->ms_fats;
+	dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
+					(sector_size-1)) / sector_size;
+
+	__cluster_count = (sect_count - (reserved + __fat_size + dir_size)) /
+							ms->ms_cluster_size;
+	if (!ms->ms_fat_length && vs->vs_fat32_length)
+		max_count = FAT32_MAX;
+	else
+		max_count = __cluster_count > FAT12_MAX ? FAT16_MAX : FAT12_MAX;
+
+	if (__cluster_count > max_count)
+		return 0;
+
+	if (fat_size)
+		*fat_size = __fat_size;
+	if (cluster_count)
+		*cluster_count = __cluster_count;
+
+	return 1;	/* valid */
+}
+
+/*
+ * This function is used by MBR partition table parser to avoid
+ * misinterpretation of FAT filesystem.
+ */
+int blkid_probe_is_vfat(blkid_probe pr)
+{
+	struct vfat_super_block *vs;
+	struct msdos_super_block *ms;
+	const struct blkid_idmag *mag = NULL;
+
+	if (blkid_probe_get_idmag(pr, &vfat_idinfo, NULL, &mag) || !mag)
+		return 0;
+
+	ms = blkid_probe_get_sb(pr, mag, struct msdos_super_block);
+	if (!ms)
+		return 0;
+	vs = blkid_probe_get_sb(pr, mag, struct vfat_super_block);
+	if (!vs)
+		return 0;
+
+	return fat_valid_superblock(mag, ms, vs, NULL, NULL);
+}
+
+/* FAT label extraction from the root directory taken from Kay
+ * Sievers's volume_id library */
+static int probe_vfat(blkid_probe pr, const struct blkid_idmag *mag)
+{
+	struct vfat_super_block *vs;
+	struct msdos_super_block *ms;
+	const unsigned char *vol_label = 0;
+	unsigned char *vol_serno = NULL, vol_label_buf[11];
+	uint16_t sector_size = 0, reserved;
+	uint32_t cluster_count, fat_size;
+	const char *version = NULL;
+
+	ms = blkid_probe_get_sb(pr, mag, struct msdos_super_block);
+	if (!ms)
+		return 0;
+	vs = blkid_probe_get_sb(pr, mag, struct vfat_super_block);
+	if (!vs)
+		return 0;
+	if (!fat_valid_superblock(mag, ms, vs, &cluster_count, &fat_size))
+		return 1;
+
+	sector_size = unaligned_le16(&ms->ms_sector_size);
+	reserved =  le16_to_cpu(ms->ms_reserved);
+
+	if (ms->ms_fat_length) {
+		/* the label may be an attribute in the root directory */
+		uint32_t root_start = (reserved + fat_size) * sector_size;
+		uint32_t root_dir_entries = unaligned_le16(&vs->vs_dir_entries);
+
+		vol_label = search_fat_label(pr, root_start, root_dir_entries);
+		if (vol_label) {
+			memcpy(vol_label_buf, vol_label, 11);
+			vol_label = vol_label_buf;
+		}
+
+		if (!vol_label || !memcmp(vol_label, no_name, 11))
+			vol_label = ms->ms_label;
+		vol_serno = ms->ms_serno;
+
+		blkid_probe_set_value(pr, "SEC_TYPE", (unsigned char *) "msdos",
+                              sizeof("msdos"));
+
+		if (cluster_count < FAT12_MAX)
+			version = "FAT12";
+		else if (cluster_count < FAT16_MAX)
+			version = "FAT16";
+
+	} else if (vs->vs_fat32_length) {
+		unsigned char *buf;
+		uint16_t fsinfo_sect;
+		int maxloop = 100;
+
+		/* Search the FAT32 root dir for the label attribute */
+		uint32_t buf_size = vs->vs_cluster_size * sector_size;
+		uint32_t start_data_sect = reserved + fat_size;
+		uint32_t entries = le32_to_cpu(vs->vs_fat32_length) *
+					sector_size / sizeof(uint32_t);
+		uint32_t next = le32_to_cpu(vs->vs_root_cluster);
+
+		while (next && next < entries && --maxloop) {
+			uint32_t next_sect_off;
+			uint64_t next_off, fat_entry_off;
+			int count;
+
+			next_sect_off = (next - 2) * vs->vs_cluster_size;
+			next_off = (uint64_t)(start_data_sect + next_sect_off) *
+				sector_size;
+
+			count = buf_size / sizeof(struct vfat_dir_entry);
+
+			vol_label = search_fat_label(pr, next_off, count);
+			if (vol_label) {
+				memcpy(vol_label_buf, vol_label, 11);
+				vol_label = vol_label_buf;
+				break;
+			}
+
+			/* get FAT entry */
+			fat_entry_off = ((uint64_t) reserved * sector_size) +
+				(next * sizeof(uint32_t));
+			buf = blkid_probe_get_buffer(pr, fat_entry_off, buf_size);
+			if (buf == NULL)
+				break;
+
+			/* set next cluster */
+			next = le32_to_cpu(*((uint32_t *) buf)) & 0x0fffffff;
+		}
+
+		version = "FAT32";
+
+		if (!vol_label || !memcmp(vol_label, no_name, 11))
+			vol_label = vs->vs_label;
+		vol_serno = vs->vs_serno;
+
+		/*
+		 * FAT32 should have a valid signature in the fsinfo block,
+		 * but also allow all bytes set to '\0', because some volumes
+		 * do not set the signature at all.
+		 */
+		fsinfo_sect = le16_to_cpu(vs->vs_fsinfo_sector);
+		if (fsinfo_sect) {
+			struct fat32_fsinfo *fsinfo;
+
+			buf = blkid_probe_get_buffer(pr,
+					(blkid_loff_t) fsinfo_sect * sector_size,
+					sizeof(struct fat32_fsinfo));
+			if (buf == NULL)
+				return -1;
+
+			fsinfo = (struct fat32_fsinfo *) buf;
+			if (memcmp(fsinfo->signature1, "\x52\x52\x61\x41", 4) != 0 &&
+			    memcmp(fsinfo->signature1, "\x52\x52\x64\x41", 4) != 0 &&
+			    memcmp(fsinfo->signature1, "\x00\x00\x00\x00", 4) != 0)
+				return -1;
+			if (memcmp(fsinfo->signature2, "\x72\x72\x41\x61", 4) != 0 &&
+			    memcmp(fsinfo->signature2, "\x00\x00\x00\x00", 4) != 0)
+				return -1;
+		}
+	}
+
+	if (vol_label && memcmp(vol_label, no_name, 11))
+		blkid_probe_set_label(pr, (unsigned char *) vol_label, 11);
+
+	/* We can't just print them as %04X, because they are unaligned */
+	if (vol_serno)
+		blkid_probe_sprintf_uuid(pr, vol_serno, 4, "%02X%02X-%02X%02X",
+			vol_serno[3], vol_serno[2], vol_serno[1], vol_serno[0]);
+	if (version)
+		blkid_probe_set_version(pr, version);
+
+	return 0;
+}
+
+
+const struct blkid_idinfo vfat_idinfo =
+{
+	.name		= "vfat",
+	.usage		= BLKID_USAGE_FILESYSTEM,
+	.probefunc	= probe_vfat,
+	.magics		=
+	{
+		{ .magic = "MSWIN",    .len = 5, .sboff = 0x52 },
+		{ .magic = "FAT32   ", .len = 8, .sboff = 0x52 },
+		{ .magic = "MSDOS",    .len = 5, .sboff = 0x36 },
+		{ .magic = "FAT16   ", .len = 8, .sboff = 0x36 },
+		{ .magic = "FAT12   ", .len = 8, .sboff = 0x36 },
+		{ .magic = "FAT     ", .len = 8, .sboff = 0x36 },
+		{ .magic = "\353",     .len = 1, },
+		{ .magic = "\351",     .len = 1, },
+		{ .magic = "\125\252", .len = 2, .sboff = 0x1fe },
+		{ NULL }
+	}
+};
+