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Add more checks of BPB (#21)

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Rafał 2018-10-22 14:51:32 +02:00 committed by GitHub
parent a1db3e82c7
commit c4ffb2ccf5
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1 changed files with 56 additions and 10 deletions
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66
src/fs.rs
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@ -215,9 +215,10 @@ impl BiosParameterBlock {
bytes_per_cluster, maximum_compatibility_bytes_per_cluster);
}
let is_fat32 = self.is_fat32();
if self.reserved_sectors < 1 {
return Err(Error::new(ErrorKind::Other, "invalid reserved_sectors value in BPB"));
} else if !self.is_fat32() && self.reserved_sectors != 1 {
} else if !is_fat32 && self.reserved_sectors != 1 {
// Microsoft document indicates fat12 and fat16 code exists that presume this value is 1
warn!(
"fs compatibility: reserved_sectors value '{}' in BPB is not '1', and thus is incompatible with some implementations",
@ -235,10 +236,60 @@ impl BiosParameterBlock {
);
}
if is_fat32 && self.root_entries != 0 {
return Err(Error::new(
ErrorKind::Other,
"Invalid root_entries value in BPB (should be zero for FAT32)",
));
}
if is_fat32 && self.total_sectors_16 != 0 {
return Err(Error::new(
ErrorKind::Other,
"Invalid total_sectors_16 value in BPB (should be zero for FAT32)",
));
}
if (self.total_sectors_16 == 0) == (self.total_sectors_32 == 0) {
return Err(Error::new(
ErrorKind::Other,
"Invalid BPB (total_sectors_16 or total_sectors_32 should be non-zero)",
));
}
if is_fat32 && self.sectors_per_fat_32 == 0 {
return Err(Error::new(
ErrorKind::Other,
"Invalid sectors_per_fat_32 value in BPB (should be non-zero for FAT32)",
));
}
if self.fs_version != 0 {
return Err(Error::new(ErrorKind::Other, "Unknown FS version"));
}
if self.total_sectors() <= self.first_data_sector() {
return Err(Error::new(
ErrorKind::Other,
"Invalid BPB (total_sectors field value is too small)",
));
}
let total_clusters = self.total_clusters();
let fat_type = FatType::from_clusters(total_clusters);
if is_fat32 != (fat_type == FatType::Fat32) {
return Err(Error::new(
ErrorKind::Other,
"Invalid BPB (result of FAT32 determination from total number of clusters and sectors_per_fat_16 field differs)",
));
}
let fat_entries_per_sector = self.fat_entries_per_sector(fat_type);
let total_fat_entries = self.sectors_per_fat() * fat_entries_per_sector as u32;
if total_fat_entries - RESERVED_FAT_ENTRIES < total_clusters {
warn!("FAT is too small to compared to total number of clusters");
}
Ok(())
}
@ -313,7 +364,7 @@ impl BootRecord {
return Err(Error::new(ErrorKind::Other, "Invalid boot sector signature"));
}
if self.bootjmp[0] != 0xEB && self.bootjmp[0] != 0xE9 {
warn!("Unknown opcode {} in bootjmp boot sector field", self.bootjmp[0]);
warn!("Unknown opcode {:x} in bootjmp boot sector field", self.bootjmp[0]);
}
self.bpb.validate()?;
Ok(())
@ -534,14 +585,9 @@ impl<T: ReadWriteSeek> FileSystem<T> {
boot.bpb
};
let total_sectors = bpb.total_sectors();
let sectors_per_fat = bpb.sectors_per_fat();
let root_dir_bytes = bpb.root_entries as u32 * DIR_ENTRY_SIZE as u32;
let root_dir_sectors = (root_dir_bytes + (bpb.bytes_per_sector as u32 - 1)) / bpb.bytes_per_sector as u32;
let first_data_sector = bpb.reserved_sectors as u32 + (bpb.fats as u32 * sectors_per_fat) + root_dir_sectors;
let fat_sectors = bpb.fats as u32 * sectors_per_fat;
let data_sectors = total_sectors - (bpb.reserved_sectors as u32 + fat_sectors + root_dir_sectors as u32);
let total_clusters = data_sectors / bpb.sectors_per_cluster as u32;
let root_dir_sectors = bpb.root_dir_sectors();
let first_data_sector = bpb.first_data_sector();
let total_clusters = bpb.total_clusters();
let fat_type = FatType::from_clusters(total_clusters);
// read FSInfo sector if this is FAT32