libblkid: add BitLocker detection

Supported:
* WinVista version
* Win7 and later versions (based on NTFS)
* BitLockerToGo (for removable media; based on FAT32)

Unfortunately, it's without LABEL and UUID. It seems BitLocker does
not use volume_label and volume_serial stuff from NTFS header.

Addresses: https://github.com/karelzak/util-linux/issues/617
Signed-off-by: Karel Zak <kzak@redhat.com>

5 files changed, 199 insertions, 0 deletions

diff --git a/libblkid/src/Makemodule.am b/libblkid/src/Makemodule.am
index 0e1c765fb..ea0230702 100644
--- a/libblkid/src/Makemodule.am
+++ b/libblkid/src/Makemodule.am
@@ -47,6 +47,7 @@ libblkid_la_SOURCES = \
 	libblkid/src/superblocks/bcache.c \
 	libblkid/src/superblocks/befs.c \
 	libblkid/src/superblocks/bfs.c \
+	libblkid/src/superblocks/bitlocker.c \
 	libblkid/src/superblocks/btrfs.c \
 	libblkid/src/superblocks/cramfs.c \
 	libblkid/src/superblocks/ddf_raid.c \
diff --git a/libblkid/src/superblocks/bitlocker.c b/libblkid/src/superblocks/bitlocker.c
new file mode 100644
index 000000000..032839d7e
--- /dev/null
+++ b/libblkid/src/superblocks/bitlocker.c
@@ -0,0 +1,191 @@
+/*
+ * Copyright (C) 2018 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"
+
+#define BDE_HDR_SIZE	512
+#define BDE_HDR_OFFSET	0
+
+struct bde_header_win7 {
+/*   0 */ unsigned char	boot_entry_point[3];
+/*   3 */ unsigned char	fs_signature[8];
+/*  11 */ unsigned char	__dummy1[67 - 11];
+/*  67 */ uint32_t      volume_serial;		/* NTFS uses 64bit serial number */
+/*  71 */ unsigned char volume_label[11];	/* "NO NAME\x20\x20\x20\x20" only */
+/*  82 */ unsigned char __dummy2[160 - 82];
+/* 160 */ unsigned char guid[16];		/* BitLocker specific GUID */
+/* 176 */ uint64_t      fve_metadata_offset;
+} __attribute__((packed));
+
+
+struct bde_header_togo {
+/*   0 */ unsigned char	boot_entry_point[3];
+/*   3 */ unsigned char	fs_signature[8];
+/*  11 */ unsigned char	__dummy[424 - 11];
+/* 424 */ unsigned char guid[16];
+/* 440 */ uint64_t      fve_metadata_offset;
+} __attribute__((packed));
+
+
+struct bde_fve_metadata {
+/*   0 */ unsigned char  signature[8];
+/*   8 */ uint16_t       size;
+/*  10 */ uint16_t       version;
+};
+
+enum {
+	BDE_VERSION_VISTA = 0,
+	BDE_VERSION_WIN7,
+	BDE_VERSION_TOGO
+};
+
+#define BDE_MAGIC_VISTA		"\xeb\x52\x90-FVE-FS-"
+#define BDE_MAGIC_WIN7		"\xeb\x58\x90-FVE-FS-"
+#define BDE_MAGIC_TOGO		"\xeb\x58\x90MSWIN4.1"
+
+#define BDE_MAGIC_FVE		"-FVE-FS-"
+
+static int get_bitlocker_type(const unsigned char *buf)
+{
+	size_t i;
+	static const char *map[] = {
+		[BDE_VERSION_VISTA] = BDE_MAGIC_VISTA,
+		[BDE_VERSION_WIN7]  = BDE_MAGIC_WIN7,
+		[BDE_VERSION_TOGO]  = BDE_MAGIC_TOGO
+	};
+
+	for (i = 0; i < ARRAY_SIZE(map); i++) {
+		if (memcmp(buf, map[i], 11) == 0)
+			return (int) i;
+	}
+
+	return -1;
+}
+
+/* Returns: < 0 error, 1 nothing, 0 success
+ */
+static int get_bitlocker_headers(blkid_probe pr,
+				int *type,
+				const unsigned char **buf_hdr,
+				const unsigned char **buf_fve)
+{
+
+	const unsigned char *buf;
+	struct bde_fve_metadata *fve;
+	uint64_t off = 0;
+	int kind;
+
+	if (buf_hdr)
+		*buf_hdr = NULL;
+	if (buf_fve)
+		*buf_fve = NULL;
+	if (type)
+		*type = -1;
+
+	buf = blkid_probe_get_buffer(pr, BDE_HDR_OFFSET, BDE_HDR_SIZE);
+	if (!buf)
+		return errno ? -errno : 1;
+
+	kind = get_bitlocker_type(buf);
+
+	/* Check BitLocker header */
+	switch (kind) {
+	case BDE_VERSION_WIN7:
+		off = le64_to_cpu(((struct bde_header_win7 *) buf)->fve_metadata_offset);
+		break;
+	case BDE_VERSION_TOGO:
+		off = le64_to_cpu(((struct bde_header_togo *) buf)->fve_metadata_offset);
+		break;
+	case BDE_VERSION_VISTA:
+		goto done;
+	default:
+		goto nothing;
+	}
+
+	if (!off)
+		goto nothing;
+	if (buf_hdr)
+		*buf_hdr = buf;
+
+	/* Check Bitlocker FVE metadata header */
+	buf = blkid_probe_get_buffer(pr, off, sizeof(struct bde_fve_metadata));
+	if (!buf)
+		return errno ? -errno : 1;
+
+	fve = (struct bde_fve_metadata *) buf;
+	if (memcmp(fve->signature, BDE_MAGIC_FVE, sizeof(fve->signature)) != 0)
+		goto nothing;
+	if (buf_fve)
+		*buf_fve = buf;
+done:
+	if (type)
+		*type = kind;
+	return 0;
+nothing:
+	return 1;
+}
+
+/*
+ * This is used by vFAT and NTFS prober to avoid collisions with bitlocker.
+ */
+int blkid_probe_is_bitlocker(blkid_probe pr)
+{
+	return get_bitlocker_headers(pr, NULL, NULL, NULL) == 0;
+}
+
+static int probe_bitlocker(blkid_probe pr,
+		const struct blkid_idmag *mag __attribute__((__unused__)))
+{
+	const unsigned char *buf_fve = NULL;
+	const unsigned char *buf_hdr = NULL;
+	int rc, kind;
+
+	rc = get_bitlocker_headers(pr, &kind, &buf_hdr, &buf_fve);
+	if (rc)
+		return rc;
+
+	if (kind == BDE_VERSION_WIN7) {
+		struct bde_header_win7 *hdr = (struct bde_header_win7 *) buf_hdr;
+
+		/* Unfortunately, it seems volume_serial is always zero */
+		blkid_probe_sprintf_uuid(pr,
+				(unsigned char *) &hdr->volume_serial,
+				sizeof(hdr->volume_serial),
+				"%016d", le32_to_cpu(hdr->volume_serial));
+	}
+
+	if (buf_fve) {
+		struct bde_fve_metadata *fve = (struct bde_fve_metadata *) buf_fve;
+
+		blkid_probe_sprintf_version(pr, "%d", fve->version);
+	}
+	return 0;
+}
+
+/* See header details:
+ * https://github.com/libyal/libbde/blob/master/documentation/BitLocker%20Drive%20Encryption%20(BDE)%20format.asciidoc
+ */
+const struct blkid_idinfo bitlocker_idinfo =
+{
+	.name		= "BitLocker",
+	.usage		= BLKID_USAGE_CRYPTO,
+	.probefunc	= probe_bitlocker,
+	.magics		=
+	{
+		{ .magic = BDE_MAGIC_VISTA, .len = 11 },
+		{ .magic = BDE_MAGIC_WIN7,  .len = 11 },
+		{ .magic = BDE_MAGIC_TOGO,  .len = 11 },
+		{ NULL }
+	}
+};
diff --git a/libblkid/src/superblocks/superblocks.c b/libblkid/src/superblocks/superblocks.c
index 076541d1a..6dfd2be64 100644
--- a/libblkid/src/superblocks/superblocks.c
+++ b/libblkid/src/superblocks/superblocks.c
@@ -115,6 +115,7 @@ static const struct blkid_idinfo *idinfos[] =
 	&ubi_idinfo,
 	&vdo_idinfo,
 	&stratis_idinfo,
+	&bitlocker_idinfo,
 
 	/* Filesystems */
 	&vfat_idinfo,
diff --git a/libblkid/src/superblocks/superblocks.h b/libblkid/src/superblocks/superblocks.h
index 2723fb1d5..d677f85bc 100644
--- a/libblkid/src/superblocks/superblocks.h
+++ b/libblkid/src/superblocks/superblocks.h
@@ -81,6 +81,7 @@ extern const struct blkid_idinfo bcache_idinfo;
 extern const struct blkid_idinfo mpool_idinfo;
 extern const struct blkid_idinfo vdo_idinfo;
 extern const struct blkid_idinfo stratis_idinfo;
+extern const struct blkid_idinfo bitlocker_idinfo;
 
 /*
  * superblock functions
@@ -105,4 +106,6 @@ extern int blkid_probe_set_id_label(blkid_probe pr, const char *name,
 extern int blkid_probe_set_utf8_id_label(blkid_probe pr, const char *name,
 			     unsigned char *data, size_t len, int enc);
 
+extern int blkid_probe_is_bitlocker(blkid_probe pr);
+
 #endif /* _BLKID_SUPERBLOCKS_H */
diff --git a/libblkid/src/superblocks/vfat.c b/libblkid/src/superblocks/vfat.c
index df4ebe371..f4628da4a 100644
--- a/libblkid/src/superblocks/vfat.c
+++ b/libblkid/src/superblocks/vfat.c
@@ -268,6 +268,9 @@ static int fat_valid_superblock(blkid_probe pr,
 		}
 	}
 
+	if (blkid_probe_is_bitlocker(pr))
+		return 0;
+
 	return 1;	/* valid */
 }