Check BPB-reported sizes more thoroughly, improve error messages.

Fixes #1
Thanks to 5225225 <5225225@mailbox.org> for the report!

src/boot_sector.rs

@@ -47,7 +47,7 @@ impl BiosParameterBlock {
         const MAXIMUM_CLUSTER_SIZE: u32 = 2097152;
 
         let cluster_size = self.sectors_per_cluster as u32 * self.sector_size as u32;
-        if cluster_size > MAXIMUM_CLUSTER_SIZE {
+        if cluster_size > MAXIMUM_CLUSTER_SIZE || !cluster_size.is_power_of_two() {
             return Err(NtfsError::UnsupportedClusterSize {
                 expected: MAXIMUM_CLUSTER_SIZE,
                 actual: cluster_size,
@@ -104,8 +104,21 @@ impl BiosParameterBlock {
         }
     }
 
-    pub(crate) fn sector_size(&self) -> u16 {
-        self.sector_size
+    pub(crate) fn sector_size(&self) -> Result<u16> {
+        // NTFS-3G supports more sector sizes, but I haven't got Windows to accept an NTFS partition
+        // with a sector size other than 512 bytes.
+        // This restriction is arbitrary and can be lifted once you show me a Windows NTFS partition
+        // with a different sector size.
+        const SUPPORTED_SECTOR_SIZE: u16 = 512;
+
+        if self.sector_size != SUPPORTED_SECTOR_SIZE {
+            return Err(NtfsError::UnsupportedSectorSize {
+                expected: SUPPORTED_SECTOR_SIZE,
+                actual: self.sector_size,
+            });
+        }
+
+        Ok(self.sector_size)
     }
 
     pub(crate) fn serial_number(&self) -> u64 {

src/error.rs

@@ -44,7 +44,7 @@ pub enum NtfsError {
         expected: u8,
         actual: u8,
     },
-    /// The cluster count {cluster_count} is too big
+    /// The NTFS Data Run cluster count {cluster_count} is too big to be multiplied by the cluster size
     InvalidClusterCount { cluster_count: u64 },
     /// The NTFS File Record at byte position {position:#010x} indicates an allocated size of {expected} bytes, but the record only has a size of {actual} bytes
     InvalidFileAllocatedSize {
@@ -147,12 +147,14 @@ pub enum NtfsError {
     },
     /// I/O error: {0:?}
     Io(binread::io::Error),
-    /// The Logical Cluster Number (LCN) {lcn} is too big to be processed
+    /// The Logical Cluster Number (LCN) {lcn} is too big to be multiplied by the cluster size
     LcnTooBig { lcn: Lcn },
     /// The index root at byte position {position:#010x} is a large index, but no matching index allocation attribute was provided
     MissingIndexAllocation { position: u64 },
-    /// The NTFS file at byte position {position:#010x} is not a directory.
+    /// The NTFS file at byte position {position:#010x} is not a directory
     NotADirectory { position: u64 },
+    /// The total sector count is too big to be multiplied by the sector size
+    TotalSectorsTooBig { total_sectors: u64 },
     /// The NTFS Attribute at byte position {position:#010x} should not belong to an Attribute List, but it does
     UnexpectedAttributeListAttribute { position: u64 },
     /// The NTFS Attribute at byte position {position:#010x} should be resident, but it is non-resident
@@ -165,6 +167,8 @@ pub enum NtfsError {
     UnsupportedClusterSize { expected: u32, actual: u32 },
     /// The namespace of the NTFS file name starting at byte position {position:#010x} is {actual}, which is not supported
     UnsupportedFileNamespace { position: u64, actual: u8 },
+    /// The sector size is {actual} bytes, but the only supported one is {expected}
+    UnsupportedSectorSize { expected: u16, actual: u16 },
     /// The Update Sequence Array (USA) of the record at byte position {position:#010x} has entries for {array_count} sectors of {sector_size} bytes, but the record is only {record_size} bytes long
     UpdateSequenceArrayExceedsRecordSize {
         position: u64,
@@ -184,9 +188,9 @@ pub enum NtfsError {
         expected: Vcn,
         actual: Vcn,
     },
-    /// The index allocation at byte position {position:#010x} references a Virtual Cluster Number (VCN) {vcn}, but this VCN exceeds the boundaries of the filesystem.
+    /// The index allocation at byte position {position:#010x} references a Virtual Cluster Number (VCN) {vcn}, but this VCN exceeds the boundaries of the filesystem
     VcnOutOfBoundsInIndexAllocation { position: u64, vcn: Vcn },
-    /// The Virtual Cluster Number (VCN) {vcn} is too big to be processed
+    /// The Virtual Cluster Number (VCN) {vcn} is too big to be multiplied by the cluster size
     VcnTooBig { vcn: Vcn },
 }
 

src/ntfs.rs

@@ -46,8 +46,11 @@ impl Ntfs {
 
         let bpb = boot_sector.bpb();
         let cluster_size = bpb.cluster_size()?;
-        let sector_size = bpb.sector_size();
-        let size = bpb.total_sectors() * sector_size as u64;
+        let sector_size = bpb.sector_size()?;
+        let total_sectors = bpb.total_sectors();
+        let size = total_sectors
+            .checked_mul(sector_size as u64)
+            .ok_or(NtfsError::TotalSectorsTooBig { total_sectors })?;
         let mft_position = 0;
         let file_record_size = bpb.file_record_size()?;
         let serial_number = bpb.serial_number();