Merge pull request #21 from nix-community/boot-file-integrity

Verify Kernel/Initrd Integrity using Blake3

flake.nix

@@ -54,21 +54,12 @@
         });
       };
 
-      # This is basically an empty EFI application that we use as a
-      # carrier for the initrd.
-      initrdStubCrane = buildRustApp {
-        src = ./rust/initrd-stub;
-        target = "x86_64-unknown-uefi";
-        doCheck = false;
-      };
-
       lanzabooteCrane = buildRustApp {
         src = ./rust/lanzaboote;
         target = "x86_64-unknown-uefi";
         doCheck = false;
       };
 
-      initrd-stub = initrdStubCrane.package;
       lanzaboote = lanzabooteCrane.package;
 
       lanzatoolCrane = buildRustApp {
@@ -87,8 +78,7 @@
         makeWrapper ${lanzatool-unwrapped}/bin/lanzatool $out/bin/lanzatool \
           --set PATH ${lib.makeBinPath [ pkgs.binutils-unwrapped pkgs.sbsigntool ]} \
           --set RUST_BACKTRACE full \
-          --set LANZABOOTE_STUB ${lanzaboote}/bin/lanzaboote.efi \
+          --set LANZABOOTE_STUB ${lanzaboote}/bin/lanzaboote.efi
-          --set LANZABOOTE_INITRD_STUB ${initrd-stub}/bin/initrd-stub.efi \
       '';
     in {
       overlays.default = final: prev: {
@@ -98,7 +88,7 @@
       nixosModules.lanzaboote = import ./nix/lanzaboote.nix;
 
       packages.x86_64-linux = {
-        inherit initrd-stub lanzaboote lanzatool;
+        inherit lanzaboote lanzatool;
         default = lanzatool;
       };
 
@@ -149,7 +139,10 @@
             };
           };
         };
-        mkUnsignedTest = { name, path }: mkSecureBootTest {
+
+        # Execute a boot test that is intended to fail.
+        #
+        mkUnsignedTest = { name, path, appendCrap ? false }: mkSecureBootTest {
           inherit name;
           testScript = ''
             import json
@@ -166,10 +159,14 @@
             src_path = ${path.src}
             dst_path = ${path.dst}
             machine.succeed(f"cp -rf {src_path} {dst_path}")
+          '' + lib.optionalString appendCrap ''
+            machine.succeed(f"echo Foo >> {dst_path}")
+          '' +
+          ''
             machine.succeed("sync")
             machine.crash()
             machine.start()
-            machine.wait_for_console_text("panicked")
+            machine.wait_for_console_text("Hash mismatch")
           '';
         };
       in
@@ -221,13 +218,21 @@
             assert "Secure Boot: enabled (user)" in machine.succeed("bootctl status")
           '';
           };
+
+          # The initrd is not directly signed. Its hash is embedded
+          # into lanzaboote. To make integrity verification fail, we
+          # actually have to modify the initrd. Appending crap to the
+          # end is a harmless way that would make the kernel still
+          # accept it.
           is-initrd-secured = mkUnsignedTest {
             name = "unsigned-initrd-do-not-boot-under-secureboot";
             path = {
               src = "bootspec.get('initrd')";
               dst = "convert_to_esp(bootspec.get('initrd'))";
             };
+            appendCrap = true;
           };
+
           is-kernel-secured = mkUnsignedTest {
             name = "unsigned-kernel-do-not-boot-under-secureboot";
             path = {

rust/initrd-stub/.cargo/config

@@ -1,2 +0,0 @@
-[build]
-target = "x86_64-unknown-uefi"

rust/initrd-stub/Cargo.lock

@@ -1,104 +0,0 @@
-# This file is automatically @generated by Cargo.
-# It is not intended for manual editing.
-version = 3
-
-[[package]]
-name = "bit_field"
-version = "0.10.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dcb6dd1c2376d2e096796e234a70e17e94cc2d5d54ff8ce42b28cef1d0d359a4"
-
-[[package]]
-name = "bitflags"
-version = "1.3.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
-
-[[package]]
-name = "cfg-if"
-version = "1.0.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
-
-[[package]]
-name = "initrd-stub"
-version = "0.1.0"
-dependencies = [
- "uefi",
-]
-
-[[package]]
-name = "log"
-version = "0.4.17"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "abb12e687cfb44aa40f41fc3978ef76448f9b6038cad6aef4259d3c095a2382e"
-dependencies = [
- "cfg-if",
-]
-
-[[package]]
-name = "proc-macro2"
-version = "1.0.47"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5ea3d908b0e36316caf9e9e2c4625cdde190a7e6f440d794667ed17a1855e725"
-dependencies = [
- "unicode-ident",
-]
-
-[[package]]
-name = "quote"
-version = "1.0.21"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bbe448f377a7d6961e30f5955f9b8d106c3f5e449d493ee1b125c1d43c2b5179"
-dependencies = [
- "proc-macro2",
-]
-
-[[package]]
-name = "syn"
-version = "1.0.103"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a864042229133ada95abf3b54fdc62ef5ccabe9515b64717bcb9a1919e59445d"
-dependencies = [
- "proc-macro2",
- "quote",
- "unicode-ident",
-]
-
-[[package]]
-name = "ucs2"
-version = "0.3.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bad643914094137d475641b6bab89462505316ec2ce70907ad20102d28a79ab8"
-dependencies = [
- "bit_field",
-]
-
-[[package]]
-name = "uefi"
-version = "0.18.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "07b87700863d65dd4841556be3374d8d4f9f8dbb577ad93a39859e70b3b91f35"
-dependencies = [
- "bitflags",
- "log",
- "ucs2",
- "uefi-macros",
-]
-
-[[package]]
-name = "uefi-macros"
-version = "0.9.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "275f054a1d9fd7e43a2ce91cc24298a87b281117dea8afc120ae95faa0e96b94"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn",
-]
-
-[[package]]
-name = "unicode-ident"
-version = "1.0.5"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6ceab39d59e4c9499d4e5a8ee0e2735b891bb7308ac83dfb4e80cad195c9f6f3"

rust/initrd-stub/Cargo.toml

@@ -1,12 +0,0 @@
-[package]
-name = "initrd-stub"
-version = "0.1.0"
-edition = "2021"
-publish = false
-
-[dependencies]
-uefi = { version = "0.18.0", default-features = false, features = [ ] }
-
-[profile.release]
-opt-level = "s"
-lto = true

rust/initrd-stub/src/main.rs

@@ -1,19 +0,0 @@
-#![no_main]
-#![no_std]
-#![feature(abi_efiapi)]
-
-use core::panic::PanicInfo;
-use uefi::{
-    prelude::{entry, Boot, SystemTable},
-    Handle, Status,
-};
-
-#[panic_handler]
-fn panic(_info: &PanicInfo) -> ! {
-    loop {}
-}
-
-#[entry]
-fn main(_handle: Handle, mut _system_table: SystemTable<Boot>) -> Status {
-    Status::UNSUPPORTED
-}

rust/lanzaboote/Cargo.lock

@@ -2,6 +2,18 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "arrayref"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4c527152e37cf757a3f78aae5a06fbeefdb07ccc535c980a3208ee3060dd544"
+
+[[package]]
+name = "arrayvec"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8da52d66c7071e2e3fa2a1e5c6d088fec47b593032b254f5e980de8ea54454d6"
+
 [[package]]
 name = "bit_field"
 version = "0.10.1"
@@ -14,12 +26,37 @@ version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
+[[package]]
+name = "blake3"
+version = "1.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "42ae2468a89544a466886840aa467a25b766499f4f04bf7d9fcd10ecee9fccef"
+dependencies = [
+ "arrayref",
+ "arrayvec",
+ "cc",
+ "cfg-if",
+ "constant_time_eq",
+]
+
+[[package]]
+name = "cc"
+version = "1.0.77"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e9f73505338f7d905b19d18738976aae232eb46b8efc15554ffc56deb5d9ebe4"
+
 [[package]]
 name = "cfg-if"
 version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
+[[package]]
+name = "constant_time_eq"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f3ad85c1f65dc7b37604eb0e89748faf0b9653065f2a8ef69f96a687ec1e9279"
+
 [[package]]
 name = "ed25519-compact"
 version = "2.0.2"
@@ -41,6 +78,7 @@ dependencies = [
 name = "lanzaboote"
 version = "0.1.0"
 dependencies = [
+ "blake3",
  "ed25519-compact",
  "goblin",
  "log",

rust/lanzaboote/Cargo.toml

@@ -11,6 +11,9 @@ log = "0.4.17"
 ed25519-compact = { version = "2.0.2", default-features = false, features = [] }
 goblin = { version = "0.6.0", default-features = false, features = [ "pe64", "alloc" ]}
 
+# We don't want the assembly implementations for now.
+blake3 = { version = "1.3.3", default-features = false, features = [ "pure" ]}
+
 [profile.release]
 opt-level = "s"
 lto = true

rust/lanzaboote/src/linux_loader.rs

@@ -5,22 +5,18 @@
 //! because we read the initrd multiple times. The code needs to be
 //! restructured to solve this.
 
-use core::{ffi::c_void, ops::Range, pin::Pin, ptr::slice_from_raw_parts_mut};
+use core::{ffi::c_void, pin::Pin, ptr::slice_from_raw_parts_mut};
 
-use alloc::boxed::Box;
+use alloc::{boxed::Box, vec::Vec};
 use uefi::{
     prelude::BootServices,
     proto::{
         device_path::{DevicePath, FfiDevicePath},
-        media::file::RegularFile,
         Protocol,
     },
-    table::boot::LoadImageSource,
     unsafe_guid, Handle, Identify, Result, ResultExt, Status,
 };
 
-use crate::uefi_helpers::read_all;
-
 /// The Linux kernel's initrd loading device path.
 ///
 /// The Linux kernel points us to
@@ -65,23 +61,10 @@ struct LoadFile2Protocol {
     ) -> Status,
 
     // This is not part of the official protocol struct.
-    file: RegularFile,
+    initrd_data: Vec<u8>,
-    range: Range<usize>,
 }
 
 impl LoadFile2Protocol {
-    fn initrd_start(&self) -> usize {
-        self.range.start
-    }
-
-    fn initrd_size(&self) -> usize {
-        if self.range.is_empty() {
-            0
-        } else {
-            self.range.end - self.range.start
-        }
-    }
-
     fn load_file(
         &mut self,
         _file_path: *const FfiDevicePath,
@@ -89,24 +72,21 @@ impl LoadFile2Protocol {
         buffer_size: *mut usize,
         buffer: *mut c_void,
     ) -> Result<()> {
-        if buffer.is_null() || unsafe { *buffer_size } < self.initrd_size() {
+        if buffer.is_null() || unsafe { *buffer_size } < self.initrd_data.len() {
             unsafe {
-                *buffer_size = self.initrd_size();
+                *buffer_size = self.initrd_data.len();
             }
             return Err(Status::BUFFER_TOO_SMALL.into());
         };
 
-        self.file
-            .set_position(self.initrd_start().try_into().unwrap())?;
         unsafe {
-            *buffer_size = self.initrd_size();
+            *buffer_size = self.initrd_data.len();
         }
 
         let output_slice: &mut [u8] =
             unsafe { &mut *slice_from_raw_parts_mut(buffer as *mut u8, *buffer_size) };
 
-        let read_bytes = self.file.read(output_slice).map_err(|e| e.status())?;
+        output_slice.copy_from_slice(&self.initrd_data);
-        assert_eq!(read_bytes, unsafe { *buffer_size });
 
         Ok(())
     }
@@ -134,73 +114,15 @@ pub struct InitrdLoader {
     registered: bool,
 }
 
-/// Returns the data range of the initrd in the PE binary.
-///
-/// The initrd has to be embedded in the file as a .initrd PE section.
-fn initrd_location(initrd_efi: &mut RegularFile) -> Result<Range<usize>> {
-    initrd_efi.set_position(0)?;
-
-    let file_data = read_all(initrd_efi)?;
-    let pe_binary = goblin::pe::PE::parse(&file_data).map_err(|_| Status::INVALID_PARAMETER)?;
-
-    pe_binary
-        .sections
-        .iter()
-        .find(|s| s.name().unwrap() == ".initrd")
-        .map(|s| {
-            let section_start: usize = s.pointer_to_raw_data.try_into().unwrap();
-            let section_size: usize = s.size_of_raw_data.try_into().unwrap();
-
-            Range {
-                start: section_start,
-                end: section_start + section_size,
-            }
-        })
-        .ok_or_else(|| Status::END_OF_FILE.into())
-}
-
-/// Check the signature of the initrd.
-///
-/// For this to work, the initrd needs to be a PE binary. We misuse
-/// [`BootServices::load_image`] for this.
-fn initrd_verify(boot_services: &BootServices, initrd_efi: &mut RegularFile) -> Result<()> {
-    initrd_efi.set_position(0)?;
-    let file_data = read_all(initrd_efi)?;
-
-    let initrd_handle = boot_services.load_image(
-        boot_services.image_handle(),
-        LoadImageSource::FromBuffer {
-            buffer: &file_data,
-            file_path: None,
-        },
-    )?;
-
-    // If we get here, the security policy allowed loading the
-    // image. This means that it was signed with an acceptable key in
-    // the Secure Boot scenario.
-
-    boot_services.unload_image(initrd_handle)?;
-
-    Ok(())
-}
-
 impl InitrdLoader {
     /// Create a new [`InitrdLoader`].
     ///
     /// `handle` is the handle where the protocols are registered
     /// on. `file` is the file that is served to Linux.
-    pub fn new(
+    pub fn new(boot_services: &BootServices, handle: Handle, initrd_data: Vec<u8>) -> Result<Self> {
-        boot_services: &BootServices,
-        handle: Handle,
-        mut file: RegularFile,
-    ) -> Result<Self> {
-        initrd_verify(boot_services, &mut file)?;
-
-        let range = initrd_location(&mut file)?;
         let mut proto = Box::pin(LoadFile2Protocol {
             load_file: raw_load_file,
-            file,
+            initrd_data,
-            range,
         });
 
         // Linux finds the right handle by looking for something that

rust/lanzaboote/src/main.rs

@@ -9,7 +9,8 @@ mod linux_loader;
 mod pe_section;
 mod uefi_helpers;
 
-use pe_section::pe_section_as_string;
+use blake3::Hash;
+use pe_section::{pe_section, pe_section_as_string};
 use uefi::{
     prelude::*,
     proto::{
@@ -52,9 +53,33 @@ struct EmbeddedConfiguration {
     /// lanzaboote binary.
     kernel_filename: CString16,
 
+    /// The cryptographic hash of the kernel.
+    kernel_hash: Hash,
+
     /// The filename of the initrd to be passed to the kernel. See
     /// `kernel_filename` for how to interpret these filenames.
     initrd_filename: CString16,
+
+    /// The cryptographic hash of the initrd. This hash is computed
+    /// over the whole PE binary, not only the embedded initrd.
+    initrd_hash: Hash,
+}
+
+/// Extract a filename from a PE section. The filename is stored as UTF-8.
+fn extract_filename(file_data: &[u8], section: &str) -> Result<CString16> {
+    let filename = pe_section_as_string(file_data, section).ok_or(Status::INVALID_PARAMETER)?;
+
+    Ok(CString16::try_from(filename.as_str()).map_err(|_| Status::INVALID_PARAMETER)?)
+}
+
+/// Extract a Blake3 hash from a PE section.
+fn extract_hash(file_data: &[u8], section: &str) -> Result<Hash> {
+    let array: [u8; 32] = pe_section(file_data, section)
+        .ok_or(Status::INVALID_PARAMETER)?
+        .try_into()
+        .map_err(|_| Status::INVALID_PARAMETER)?;
+
+    Ok(array.into())
 }
 
 impl EmbeddedConfiguration {
@@ -62,14 +87,12 @@ impl EmbeddedConfiguration {
         file.set_position(0)?;
         let file_data = read_all(file)?;
 
-        let kernel_filename =
-            pe_section_as_string(&file_data, ".kernelp").ok_or(Status::INVALID_PARAMETER)?;
-        let initrd_filename =
-            pe_section_as_string(&file_data, ".initrdp").ok_or(Status::INVALID_PARAMETER)?;
-
         Ok(Self {
-            kernel_filename: CString16::try_from(kernel_filename.as_str()).unwrap(),
+            kernel_filename: extract_filename(&file_data, ".kernelp")?,
-            initrd_filename: CString16::try_from(initrd_filename.as_str()).unwrap(),
+            kernel_hash: extract_hash(&file_data, ".kernelh")?,
+
+            initrd_filename: extract_filename(&file_data, ".initrdp")?,
+            initrd_hash: extract_hash(&file_data, ".initrdh")?,
         })
     }
 }
@@ -84,8 +107,10 @@ fn main(handle: Handle, mut system_table: SystemTable<Boot>) -> Status {
         EmbeddedConfiguration::new(&mut booted_image_file(system_table.boot_services()).unwrap())
             .expect("Failed to extract configuration from binary. Did you run lanzatool?");
 
-    let mut kernel_file;
+    let kernel_data;
-    let initrd = {
+    let initrd_data;
+
+    {
         let mut file_system = system_table
             .boot_services()
             .get_image_file_system(handle)
@@ -94,7 +119,7 @@ fn main(handle: Handle, mut system_table: SystemTable<Boot>) -> Status {
             .open_volume()
             .expect("Failed to find ESP root directory");
 
-        kernel_file = root
+        let mut kernel_file = root
             .open(
                 &config.kernel_filename,
                 FileMode::Read,
@@ -104,23 +129,41 @@ fn main(handle: Handle, mut system_table: SystemTable<Boot>) -> Status {
             .into_regular_file()
             .expect("Kernel is not a regular file");
 
-        root.open(
+        kernel_data = read_all(&mut kernel_file).expect("Failed to read kernel file into memory");
+
+        let mut initrd_file = root
+            .open(
                 &config.initrd_filename,
                 FileMode::Read,
                 FileAttribute::empty(),
             )
             .expect("Failed to open initrd for reading")
             .into_regular_file()
-        .expect("Initrd is not a regular file")
+            .expect("Initrd is not a regular file");
-    };
+
+        initrd_data = read_all(&mut initrd_file).expect("Failed to read kernel file into memory");
+    }
+
+    if blake3::hash(&kernel_data) != config.kernel_hash {
+        system_table
+            .stdout()
+            .output_string(cstr16!("Hash mismatch for kernel. Refusing to load!\r\n"))
+            .unwrap();
+        return Status::SECURITY_VIOLATION;
+    }
+
+    if blake3::hash(&initrd_data) != config.initrd_hash {
+        system_table
+            .stdout()
+            .output_string(cstr16!("Hash mismatch for initrd. Refusing to load!\r\n"))
+            .unwrap();
+        return Status::SECURITY_VIOLATION;
+    }
 
     let kernel_cmdline =
         booted_image_cmdline(system_table.boot_services()).expect("Failed to fetch command line");
 
     let kernel_handle = {
-        let kernel_data =
-            read_all(&mut kernel_file).expect("Failed to read kernel file into memory");
-
         system_table
             .boot_services()
             .load_image(
@@ -145,7 +188,7 @@ fn main(handle: Handle, mut system_table: SystemTable<Boot>) -> Status {
         );
     }
 
-    let mut initrd_loader = InitrdLoader::new(system_table.boot_services(), handle, initrd)
+    let mut initrd_loader = InitrdLoader::new(system_table.boot_services(), handle, initrd_data)
         .expect("Failed to load the initrd. It may not be there or it is not signed");
     let status = system_table
         .boot_services()

rust/lanzatool/Cargo.lock

@@ -8,6 +8,18 @@ version = "1.0.66"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "216261ddc8289130e551ddcd5ce8a064710c0d064a4d2895c67151c92b5443f6"
 
+[[package]]
+name = "arrayref"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4c527152e37cf757a3f78aae5a06fbeefdb07ccc535c980a3208ee3060dd544"
+
+[[package]]
+name = "arrayvec"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8da52d66c7071e2e3fa2a1e5c6d088fec47b593032b254f5e980de8ea54454d6"
+
 [[package]]
 name = "atty"
 version = "0.2.14"
@@ -31,6 +43,35 @@ version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
+[[package]]
+name = "blake3"
+version = "1.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "42ae2468a89544a466886840aa467a25b766499f4f04bf7d9fcd10ecee9fccef"
+dependencies = [
+ "arrayref",
+ "arrayvec",
+ "cc",
+ "cfg-if",
+ "constant_time_eq",
+ "digest",
+]
+
+[[package]]
+name = "block-buffer"
+version = "0.10.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69cce20737498f97b993470a6e536b8523f0af7892a4f928cceb1ac5e52ebe7e"
+dependencies = [
+ "generic-array",
+]
+
+[[package]]
+name = "cc"
+version = "1.0.77"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e9f73505338f7d905b19d18738976aae232eb46b8efc15554ffc56deb5d9ebe4"
+
 [[package]]
 name = "cfg-if"
 version = "1.0.0"
@@ -74,6 +115,33 @@ dependencies = [
  "os_str_bytes",
 ]
 
+[[package]]
+name = "constant_time_eq"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f3ad85c1f65dc7b37604eb0e89748faf0b9653065f2a8ef69f96a687ec1e9279"
+
+[[package]]
+name = "crypto-common"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1bfb12502f3fc46cca1bb51ac28df9d618d813cdc3d2f25b9fe775a34af26bb3"
+dependencies = [
+ "generic-array",
+ "typenum",
+]
+
+[[package]]
+name = "digest"
+version = "0.10.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8168378f4e5023e7218c89c891c0fd8ecdb5e5e4f18cb78f38cf245dd021e76f"
+dependencies = [
+ "block-buffer",
+ "crypto-common",
+ "subtle",
+]
+
 [[package]]
 name = "fastrand"
 version = "1.8.0"
@@ -83,6 +151,16 @@ dependencies = [
  "instant",
 ]
 
+[[package]]
+name = "generic-array"
+version = "0.14.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bff49e947297f3312447abdca79f45f4738097cc82b06e72054d2223f601f1b9"
+dependencies = [
+ "typenum",
+ "version_check",
+]
+
 [[package]]
 name = "goblin"
 version = "0.6.0"
@@ -129,6 +207,7 @@ name = "lanzatool"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "blake3",
  "clap",
  "goblin",
  "nix",
@@ -305,6 +384,12 @@ version = "0.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
 
+[[package]]
+name = "subtle"
+version = "2.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6bdef32e8150c2a081110b42772ffe7d7c9032b606bc226c8260fd97e0976601"
+
 [[package]]
 name = "syn"
 version = "1.0.103"
@@ -339,6 +424,12 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "typenum"
+version = "1.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dcf81ac59edc17cc8697ff311e8f5ef2d99fcbd9817b34cec66f90b6c3dfd987"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.5"

rust/lanzatool/Cargo.toml

@@ -13,3 +13,4 @@ nix = { version = "0.25.0", default-features = false, features = [ "fs" ] }
 serde = { version = "1.0.147", features = ["derive"] }
 serde_json = "1.0.89"
 tempfile = "3.3.0"
+blake3 = "1.3.3"

rust/lanzatool/src/cli.rs

@@ -59,14 +59,11 @@ impl Commands {
 fn install(args: InstallCommand) -> Result<()> {
     let lanzaboote_stub =
         std::env::var("LANZABOOTE_STUB").context("Failed to read LANZABOOTE_STUB env variable")?;
-    let initrd_stub = std::env::var("LANZABOOTE_INITRD_STUB")
-        .context("Failed to read LANZABOOTE_INITRD_STUB env variable")?;
 
     let key_pair = KeyPair::new(&args.public_key, &args.private_key);
 
     install::Installer::new(
         PathBuf::from(lanzaboote_stub),
-        PathBuf::from(initrd_stub),
         key_pair,
         args.pki_bundle,
         args.auto_enroll,

rust/lanzatool/src/install.rs

@@ -14,7 +14,6 @@ use crate::signature::KeyPair;
 
 pub struct Installer {
     lanzaboote_stub: PathBuf,
-    initrd_stub: PathBuf,
     key_pair: KeyPair,
     _pki_bundle: Option<PathBuf>,
     _auto_enroll: bool,
@@ -25,7 +24,6 @@ pub struct Installer {
 impl Installer {
     pub fn new(
         lanzaboote_stub: PathBuf,
-        initrd_stub: PathBuf,
         key_pair: KeyPair,
         _pki_bundle: Option<PathBuf>,
         _auto_enroll: bool,
@@ -34,7 +32,6 @@ impl Installer {
     ) -> Self {
         Self {
             lanzaboote_stub,
-            initrd_stub,
             key_pair,
             _pki_bundle,
             _auto_enroll,
@@ -68,14 +65,10 @@ impl Installer {
     }
 
     fn install_generation(&self, generation: &Generation) -> Result<()> {
-        println!("Reading bootspec...");
-
         let bootspec = &generation.bootspec;
 
         let esp_paths = EspPaths::new(&self.esp, generation)?;
 
-        println!("Assembling lanzaboote image...");
-
         let kernel_cmdline =
             assemble_kernel_cmdline(&bootspec.init, bootspec.kernel_params.clone());
 
@@ -87,6 +80,31 @@ impl Installer {
         // TODO(Raito): prove to niksnur this is actually acceptable.
         let secure_temp_dir = tempdir()?;
 
+        println!("Appending secrets to initrd...");
+
+        let initrd_location = secure_temp_dir.path().join("initrd");
+        copy(&bootspec.initrd, &initrd_location)?;
+        if let Some(initrd_secrets_script) = &bootspec.initrd_secrets {
+            append_initrd_secrets(initrd_secrets_script, &initrd_location)?;
+        }
+
+        let systemd_boot = bootspec
+            .toplevel
+            .join("systemd/lib/systemd/boot/efi/systemd-bootx64.efi");
+
+        [
+            (&systemd_boot, &esp_paths.efi_fallback),
+            (&systemd_boot, &esp_paths.systemd_boot),
+            (&bootspec.kernel, &esp_paths.kernel),
+        ]
+        .into_iter()
+        .try_for_each(|(from, to)| install_signed(&self.key_pair, from, to))?;
+
+        // The initrd doesn't need to be signed. Lanzaboote has its
+        // hash embedded and will refuse loading it when the hash
+        // mismatches.
+        install(&initrd_location, &esp_paths.initrd).context("Failed to install initrd to ESP")?;
+
         let lanzaboote_image = pe::lanzaboote_image(
             &secure_temp_dir,
             &self.lanzaboote_stub,
@@ -98,40 +116,17 @@ impl Installer {
         )
         .context("Failed to assemble stub")?;
 
-        println!("Wrapping initrd into a PE binary...");
+        install_signed(
+            &self.key_pair,
+            &lanzaboote_image,
+            &esp_paths.lanzaboote_image,
+        )
+        .context("Failed to install lanzaboote")?;
 
-        let initrd_location = secure_temp_dir.path().join("initrd");
+        // Sync files to persistent storage. This may improve the
-        copy(&bootspec.initrd, &initrd_location)?;
+        // chance of a consistent boot directory in case the system
-        if let Some(initrd_secrets_script) = &bootspec.initrd_secrets {
+        // crashes.
-            append_initrd_secrets(initrd_secrets_script, &initrd_location)?;
-        }
-        let wrapped_initrd = pe::wrap_initrd(&secure_temp_dir, &self.initrd_stub, &initrd_location)
-            .context("Failed to assemble stub")?;
-
-        println!("Sign and copy files to EFI system partition...");
-
-        let systemd_boot = bootspec
-            .toplevel
-            .join("systemd/lib/systemd/boot/efi/systemd-bootx64.efi");
-
-        let files_to_copy_and_sign = [
-            (&systemd_boot, &esp_paths.efi_fallback),
-            (&systemd_boot, &esp_paths.systemd_boot),
-            (&lanzaboote_image, &esp_paths.lanzaboote_image),
-            (&bootspec.kernel, &esp_paths.kernel),
-            (&wrapped_initrd, &esp_paths.initrd),
-        ];
-
-        for (from, to) in files_to_copy_and_sign {
-            println!("Signing {}...", to.display());
-
-            ensure_parent_dir(to);
-            self.key_pair.sign_and_copy(from, to).with_context(|| {
-                format!("Failed to copy and sign file from {:?} to {:?}", from, to)
-            })?;
-            // Call sync to improve the likelihood that file is actually written to disk
         sync();
-        }
 
         println!(
             "Successfully installed lanzaboote to '{}'",
@@ -142,6 +137,38 @@ impl Installer {
     }
 }
 
+/// Install a PE file. The PE gets signed in the process.
+///
+/// The file is only signed and copied if it doesn't exist at the destination
+fn install_signed(key_pair: &KeyPair, from: &Path, to: &Path) -> Result<()> {
+    if to.exists() {
+        println!("{} already exists, skipping...", to.display());
+    } else {
+        println!("Signing and installing {}...", to.display());
+        ensure_parent_dir(to);
+        key_pair
+            .sign_and_copy(from, to)
+            .with_context(|| format!("Failed to copy and sign file from {:?} to {:?}", from, to))?;
+    }
+
+    Ok(())
+}
+
+/// Install an arbitrary file
+///
+/// The file is only copied if it doesn't exist at the destination
+fn install(from: &Path, to: &Path) -> Result<()> {
+    if to.exists() {
+        println!("{} already exists, skipping...", to.display());
+    } else {
+        println!("Installing {}...", to.display());
+        ensure_parent_dir(to);
+        copy(from, to)?;
+    }
+
+    Ok(())
+}
+
 pub fn append_initrd_secrets(
     append_initrd_secrets_path: &Path,
     initrd_path: &PathBuf,

rust/lanzatool/src/pe.rs

@@ -12,6 +12,11 @@ use crate::utils;
 
 use tempfile::TempDir;
 
+/// Attach all information that lanzaboote needs into the PE binary.
+///
+/// When this function is called the referenced files already need to
+/// be present in the ESP. This is required, because we need to read
+/// them to compute hashes.
 pub fn lanzaboote_image(
     target_dir: &TempDir,
     lanzaboote_stub: &Path,
@@ -21,49 +26,67 @@ pub fn lanzaboote_image(
     initrd_path: &Path,
     esp: &Path,
 ) -> Result<PathBuf> {
-    // objcopy copies files into the PE binary. That's why we have to write the contents
+    // objcopy can only copy files into the PE binary. That's why we
-    // of some bootspec properties to disk
+    // have to write the contents of some bootspec properties to disk.
-    let (kernel_cmdline_file, _) =
+    let kernel_cmdline_file = write_to_tmp(target_dir, "kernel-cmdline", kernel_cmdline.join(" "))?;
-        write_to_tmp(target_dir, "kernel-cmdline", kernel_cmdline.join(" "))?;
+
-    let (kernel_path_file, _) = write_to_tmp(
+    let kernel_path_file = write_to_tmp(
         target_dir,
         "kernel-esp-path",
         esp_relative_path_string(esp, kernel_path),
     )?;
-    let (initrd_path_file, _) = write_to_tmp(
+    let kernel_hash_file = write_to_tmp(
+        target_dir,
+        "kernel-hash",
+        file_hash(kernel_path)?.as_bytes(),
+    )?;
+
+    let initrd_path_file = write_to_tmp(
         target_dir,
         "initrd-esp-path",
         esp_relative_path_string(esp, initrd_path),
     )?;
+    let initrd_hash_file = write_to_tmp(
+        target_dir,
+        "initrd-hash",
+        file_hash(initrd_path)?.as_bytes(),
+    )?;
 
     let os_release_offs = stub_offset(lanzaboote_stub)?;
     let kernel_cmdline_offs = os_release_offs + file_size(os_release)?;
     let initrd_path_offs = kernel_cmdline_offs + file_size(&kernel_cmdline_file)?;
     let kernel_path_offs = initrd_path_offs + file_size(&initrd_path_file)?;
+    let initrd_hash_offs = kernel_path_offs + file_size(&kernel_path_file)?;
+    let kernel_hash_offs = initrd_hash_offs + file_size(&initrd_hash_file)?;
 
     let sections = vec![
         s(".osrel", os_release, os_release_offs),
         s(".cmdline", kernel_cmdline_file, kernel_cmdline_offs),
         s(".initrdp", initrd_path_file, initrd_path_offs),
         s(".kernelp", kernel_path_file, kernel_path_offs),
+        s(".initrdh", initrd_hash_file, initrd_hash_offs),
+        s(".kernelh", kernel_hash_file, kernel_hash_offs),
     ];
 
     wrap_in_pe(target_dir, "lanzaboote-stub.efi", lanzaboote_stub, sections)
 }
 
-pub fn wrap_initrd(target_dir: &TempDir, initrd_stub: &Path, initrd: &Path) -> Result<PathBuf> {
+/// Compute the blake3 hash of a file.
-    let initrd_offs = stub_offset(initrd_stub)?;
+fn file_hash(file: &Path) -> Result<blake3::Hash> {
-    let sections = vec![s(".initrd", initrd, initrd_offs)];
+    Ok(blake3::hash(&fs::read(file)?))
-    wrap_in_pe(target_dir, "wrapped-initrd.exe", initrd_stub, sections)
 }
 
+/// Take a PE binary stub and attach sections to it.
+///
+/// The result is then written to a new file. Returns the filename of
+/// the generated file.
 fn wrap_in_pe(
     target_dir: &TempDir,
-    filename: &str,
+    output_filename: &str,
     stub: &Path,
     sections: Vec<Section>,
 ) -> Result<PathBuf> {
-    let image_path = target_dir.path().join(filename);
+    let image_path = target_dir.path().join(output_filename);
     let _ = fs::OpenOptions::new()
         .create(true)
         .write(true)
@@ -117,21 +140,26 @@ fn s(name: &'static str, file_path: impl AsRef<Path>, offset: u64) -> Section {
     }
 }
 
+/// Write a `u8` slice to a temporary file.
 fn write_to_tmp(
     secure_temp: &TempDir,
     filename: &str,
     contents: impl AsRef<[u8]>,
-) -> Result<(PathBuf, fs::File)> {
+) -> Result<PathBuf> {
+    let path = secure_temp.path().join(filename);
+
     let mut tmpfile = fs::OpenOptions::new()
         .create(true)
         .write(true)
         .mode(0o600)
-        .open(secure_temp.path().join(filename))
+        .open(&path)
         .context("Failed to create tempfile")?;
+
     tmpfile
         .write_all(contents.as_ref())
         .context("Failed to write to tempfile")?;
-    Ok((secure_temp.path().join(filename), tmpfile))
+
+    Ok(path)
 }
 
 fn esp_relative_path_string(esp: &Path, path: &Path) -> String {