MFC r275680:

Add fstyp(8).  This utility, named after its SVR4 counterpart, detects
filesystems.  It differs from file(1) in that it gives machine-parseable
output, it outputs filesystem labels, doesn't get confused by other
formats metadata, and runs in Capsicum sandbox.

Differential Revision:	https://reviews.freebsd.org/D1255
Relnotes:	yes
Sponsored by:	The FreeBSD Foundation

1 files changed, 183 insertions, 0 deletions

diff --git a/usr.sbin/fstyp/msdosfs.c b/usr.sbin/fstyp/msdosfs.c
new file mode 100644
index 0000000..b299243
--- /dev/null
+++ b/usr.sbin/fstyp/msdosfs.c
@@ -0,0 +1,183 @@
+/*-
+ * Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
+ * Copyright (c) 2006 Tobias Reifenberger
+ * Copyright (c) 2014 The FreeBSD Foundation
+ * All rights reserved.
+ *
+ * This software was developed by Edward Tomasz Napierala under sponsorship
+ * from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "fstyp.h"
+#include "msdosfs.h"
+
+#define LABEL_NO_NAME		"NO NAME    "
+
+int
+fstyp_msdosfs(FILE *fp, char *label, size_t size)
+{
+	FAT_BSBPB *pfat_bsbpb;
+	FAT32_BSBPB *pfat32_bsbpb;
+	FAT_DES *pfat_entry;
+	uint8_t *sector0, *sector;
+	uint32_t i;
+
+	sector0 = NULL;
+	sector = NULL;
+
+	/* Load 1st sector with boot sector and boot parameter block. */
+	sector0 = (uint8_t *)read_buf(fp, 0, 512);
+	if (sector0 == NULL)
+		return (1);
+
+	/* Check for the FAT boot sector signature. */
+	if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
+		goto error;
+	}
+
+	/*
+	 * Test if this is really a FAT volume and determine the FAT type.
+	 */
+
+	pfat_bsbpb = (FAT_BSBPB *)sector0;
+	pfat32_bsbpb = (FAT32_BSBPB *)sector0;
+
+	if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
+		/*
+		 * If the BPB_FATSz16 field is not zero and the string "FAT" is
+		 * at the right place, this should be a FAT12 or FAT16 volume.
+		 */
+		if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
+			goto error;
+		}
+
+		/* A volume with no name should have "NO NAME    " as label. */
+		if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
+		    sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
+			goto endofchecks;
+		}
+		strlcpy(label, pfat_bsbpb->BS_VolLab,
+		    MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
+	} else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
+		uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
+
+		/*
+		 * If the BPB_FATSz32 field is not zero and the string "FAT" is
+		 * at the right place, this should be a FAT32 volume.
+		 */
+		if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
+			goto error;
+		}
+
+		/*
+		 * If the volume label is not "NO NAME    " we're done.
+		 */
+		if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
+		    sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
+			strlcpy(label, pfat32_bsbpb->BS_VolLab,
+			    MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
+			goto endofchecks;
+		}
+
+		/*
+		 * If the volume label "NO NAME    " is in the boot sector, the
+		 * label of FAT32 volumes may be stored as a special entry in
+		 * the root directory.
+		 */
+		fat_FirstDataSector =
+		    UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
+		    (pfat32_bsbpb->BPB_NumFATs *
+		     UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
+		fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
+
+		//    fat_FirstDataSector, fat_BytesPerSector);
+
+		for (offset = fat_BytesPerSector * fat_FirstDataSector;;
+		    offset += fat_BytesPerSector) {
+			sector = (uint8_t *)read_buf(fp, offset, fat_BytesPerSector);
+			if (sector == NULL)
+				goto error;
+
+			pfat_entry = (FAT_DES *)sector;
+			do {
+				/* No more entries available. */
+				if (pfat_entry->DIR_Name[0] == 0) {
+					goto endofchecks;
+				}
+
+				/* Skip empty or long name entries. */
+				if (pfat_entry->DIR_Name[0] == 0xe5 ||
+				    (pfat_entry->DIR_Attr &
+				     FAT_DES_ATTR_LONG_NAME) ==
+				    FAT_DES_ATTR_LONG_NAME) {
+					continue;
+				}
+
+				/*
+				 * The name of the entry is the volume label if
+				 * ATTR_VOLUME_ID is set.
+				 */
+				if (pfat_entry->DIR_Attr &
+				    FAT_DES_ATTR_VOLUME_ID) {
+					strlcpy(label, pfat_entry->DIR_Name,
+					    MIN(size,
+					    sizeof(pfat_entry->DIR_Name) + 1));
+					goto endofchecks;
+				}
+			} while((uint8_t *)(++pfat_entry) <
+			    (uint8_t *)(sector + fat_BytesPerSector));
+			free(sector);
+		}
+	} else {
+		goto error;
+	}
+
+endofchecks:
+	for (i = size - 1; i > 0; i--) {
+		if (label[i] == '\0')
+			continue;
+		else if (label[i] == ' ')
+			label[i] = '\0';
+		else
+			break;
+	}
+
+	free(sector0);
+	free(sector);
+
+	return (0);
+
+error:
+	free(sector0);
+	free(sector);
+
+	return (1);
+}