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use crate::structures::common::{self, StructureError};
use std::collections::HashMap;
/// Struct to store MBR partition info
#[derive(Debug, Default, Clone)]
pub struct MBRPartition {
pub start: usize,
pub size: usize,
pub name: String,
}
/// Struct to store MBR info
#[derive(Debug, Default, Clone)]
pub struct MBRHeader {
pub image_size: usize,
pub partitions: Vec<MBRPartition>,
}
/// Parse a Master Boot Record image
pub fn parse_mbr_image(mbr_data: &[u8]) -> Result<MBRHeader, StructureError> {
const BLOCK_SIZE: usize = 512;
const MIN_IMAGE_SIZE: usize = BLOCK_SIZE * 2;
const PARTITION_COUNT: usize = 4;
const PARTITION_TABLE_OFFSET: usize = 446;
let partition_entry_structure = vec![
("status", "u8"),
("chs_start", "u24"),
("os_type", "u8"),
("chs_end", "u24"),
("lba_start", "u32"),
("lba_size", "u32"),
];
let known_os_types = HashMap::from([
(0x07, "NTFS_IFS_HPFS_exFAT"),
(0x0B, "FAT32"),
(0x0C, "FAT32"),
(0x43, "Linux"),
(0x4D, "QNX Primary Volume"),
(0x4E, "QNX Secondary Volume"),
(0x81, "Minix"),
(0x83, "Linux"),
(0x8E, "Linux LVM"),
(0x96, "ISO-9660"),
(0xB1, "QNXv6 File System"),
(0xB2, "QNXv6 File System"),
(0xB3, "QNXv6 File System"),
(0xEE, "EFI GPT Protective"),
(0xEF, "EFI System Partition"),
]);
let allowed_status_values: Vec<usize> = vec![0, 0x80];
let partition_structure_size = common::size(&partition_entry_structure);
let partition_table_start: usize = PARTITION_TABLE_OFFSET;
let partition_table_end: usize =
partition_table_start + (partition_structure_size * PARTITION_COUNT);
let mut mbr_header = MBRHeader {
..Default::default()
};
// Get the partition table raw bytes
if let Some(partition_table) = mbr_data.get(partition_table_start..partition_table_end) {
// Parse each partition table entry
for i in 0..PARTITION_COUNT {
// Offset in the partition table for this entry
let partition_entry_start: usize = i * partition_structure_size;
// Parse this partition table entry
match common::parse(
&partition_table[partition_entry_start..],
&partition_entry_structure,
"little",
) {
Err(_) => {
return Err(StructureError);
}
Ok(partition_entry) => {
// OS type of zero or LBA size of 0 can be ignored
if partition_entry["os_type"] != 0 || partition_entry["lba_size"] != 0 {
// Validate the reported MBR status value
if allowed_status_values.contains(&partition_entry["status"]) {
// Default to unknown partition type
let mut this_partition_name: &str = "Unknown";
// If partition type is known, provide a descriptive name
if known_os_types.contains_key(&partition_entry["os_type"]) {
this_partition_name = known_os_types[&partition_entry["os_type"]];
}
// Create an MBRPartition structure for this entry
let this_partition = MBRPartition {
start: partition_entry["lba_start"] * BLOCK_SIZE,
size: partition_entry["lba_size"] * BLOCK_SIZE,
name: this_partition_name.to_string(),
};
// Calculate where this partition ends
let this_partition_end_offset =
this_partition.start + this_partition.size;
// Some valid MBRs have partitions that start/end out of bounds WRT the disk image.
// Not sure why? At any rate, don't include them in the reported partitions.
if this_partition_end_offset <= mbr_data.len() {
// Don't report the partition where the MBR header resides
if this_partition.start != 0 {
// Add it to the list of partitions
mbr_header.partitions.push(this_partition.clone());
}
// Image size is the end of the farthest away partition
if this_partition_end_offset > mbr_header.image_size {
mbr_header.image_size = this_partition_end_offset;
}
}
}
}
}
}
}
// There should be at least one valid partition
if !mbr_header.partitions.is_empty() {
// Total size should be greater than minimum size
if mbr_header.image_size > MIN_IMAGE_SIZE {
return Ok(mbr_header);
}
}
}
Err(StructureError)
}