Merge pull request #723 from ReFirmLabs/btrfs_support

Btrfs support

Cargo.toml

@@ -17,6 +17,7 @@ entropy = "0.4.2"
 colored = "2.1.0"
 termsize = "0.1"
 crc32-v2 = "0.0.4"
+crc32c = "0.6.8"
 plotters = "0.3.6"
 xz2 = "0.1.7"
 bzip2 = "0.4.4"

src/magic.rs

@@ -921,6 +921,17 @@ pub fn patterns() -> Vec<signatures::common::Signature> {
             description: signatures::apfs::DESCRIPTION.to_string(),
             extractor: Some(extractors::apfs::apfs_extractor()),
         },
+        // BTRFS
+        signatures::common::Signature {
+            name: "btrfs".to_string(),
+            short: false,
+            magic_offset: 0,
+            always_display: true,
+            magic: signatures::btrfs::btrfs_magic(),
+            parser: signatures::btrfs::btrfs_parser,
+            description: signatures::btrfs::DESCRIPTION.to_string(),
+            extractor: None,
+        },
     ];
 
     binary_signatures

src/signatures.rs

@@ -111,6 +111,7 @@ pub mod apfs;
 pub mod arcadyan;
 pub mod autel;
 pub mod binhdr;
+pub mod btrfs;
 pub mod bzip2;
 pub mod cab;
 pub mod cfe;

src/signatures/btrfs.rs

@@ -0,0 +1,41 @@
+use crate::signatures::common::{SignatureError, SignatureResult, CONFIDENCE_MEDIUM};
+use crate::structures::btrfs::parse_btrfs_header;
+
+/// Human readable description
+pub const DESCRIPTION: &str = "BTRFS file system";
+
+/// BTRFS magic bytes
+pub fn btrfs_magic() -> Vec<Vec<u8>> {
+    vec![b"_BHRfS_M".to_vec()]
+}
+
+/// Validates the BTRFS header
+pub fn btrfs_parser(file_data: &[u8], offset: usize) -> Result<SignatureResult, SignatureError> {
+    // Offset of the superblock magic bytes in a BTRFS image
+    const MAGIC_OFFSET: usize = 0x10040;
+
+    // Successful return value
+    let mut result = SignatureResult {
+        description: DESCRIPTION.to_string(),
+        confidence: CONFIDENCE_MEDIUM,
+        ..Default::default()
+    };
+
+    // Sanity check the reported offset
+    if offset >= MAGIC_OFFSET {
+        // Actual offset is the location of the magic bytes minus the magic byte offset
+        result.offset = offset - MAGIC_OFFSET;
+
+        // Parse the superblock header; this also validates the superblock CRC
+        if let Ok(btrfs_header) = parse_btrfs_header(&file_data[result.offset..]) {
+            result.size = btrfs_header.total_size;
+            result.description = format!(
+                "{}, node size: {}, sector size: {}, leaf size: {}, stripe size: {}, bytes used: {}, total size: {} bytes",
+                result.description, btrfs_header.node_size, btrfs_header.sector_size, btrfs_header.leaf_size, btrfs_header.stripe_size, btrfs_header.bytes_used, result.size
+            );
+            return Ok(result);
+        }
+    }
+
+    Err(SignatureError)
+}

src/structures.rs

@@ -100,6 +100,7 @@ pub mod androidsparse;
 pub mod apfs;
 pub mod autel;
 pub mod binhdr;
+pub mod btrfs;
 pub mod cab;
 pub mod chk;
 pub mod common;

src/structures/btrfs.rs

@@ -0,0 +1,68 @@
+use crate::structures::common::{self, StructureError};
+use crc32c::crc32c;
+
+/// Struct to store BTRFS super block info
+#[derive(Debug, Default, Clone)]
+pub struct BTRFSHeader {
+    pub bytes_used: usize,
+    pub total_size: usize,
+    pub leaf_size: usize,
+    pub node_size: usize,
+    pub stripe_size: usize,
+    pub sector_size: usize,
+}
+
+/// Parse and validate a BTRFS super block
+pub fn parse_btrfs_header(btrfs_data: &[u8]) -> Result<BTRFSHeader, StructureError> {
+    const SUPERBLOCK_OFFSET: usize = 0x10000;
+    const SUPERBLOCK_END: usize = SUPERBLOCK_OFFSET + 0x1000;
+    const CRC_START: usize = 0x20;
+
+    // Partial BTRFS superblock structure for obtaining image size and CRC validation
+    // https://archive.kernel.org/oldwiki/btrfs.wiki.kernel.org/index.php/On-disk_Format.html#Superblock
+    let btrfs_structure = vec![
+        ("header_checksum", "u32"),
+        ("unused1", "u32"),
+        ("unused2", "u64"),
+        ("unused3", "u64"),
+        ("unused4", "u64"),
+        ("uuid_p1", "u64"),
+        ("uuid_p2", "u64"),
+        ("block_phys_addr", "u64"),
+        ("flags", "u64"),
+        ("magic", "u64"),
+        ("generation", "u64"),
+        ("root_tree_address", "u64"),
+        ("chunk_tree_address", "u64"),
+        ("log_tree_address", "u64"),
+        ("log_root_transid", "u64"),
+        ("total_bytes", "u64"),
+        ("bytes_used", "u64"),
+        ("root_dir_objid", "u64"),
+        ("num_devices", "u64"),
+        ("sector_size", "u32"),
+        ("node_size", "u32"),
+        ("leaf_size", "u32"),
+        ("stripe_size", "u32"),
+    ];
+
+    // Parse the header
+    if let Some(btrfs_header_data) = btrfs_data.get(SUPERBLOCK_OFFSET..SUPERBLOCK_END) {
+        if let Ok(btrfs_header) = common::parse(btrfs_header_data, &btrfs_structure, "little") {
+            // Validate the superblock CRC
+            if btrfs_header["header_checksum"] == (crc32c(&btrfs_header_data[CRC_START..]) as usize)
+            {
+                return Ok(BTRFSHeader {
+                    sector_size: btrfs_header["sector_size"],
+                    node_size: btrfs_header["node_size"],
+                    leaf_size: btrfs_header["leaf_size"],
+                    stripe_size: btrfs_header["stripe_size"],
+                    bytes_used: btrfs_header["bytes_used"],
+                    total_size: btrfs_header["total_bytes"],
+                });
+            }
+        }
+    }
+
+    Err(StructureError)
+}