Unwrap initrd from PE image for Linux

rust/lanzaboote/src/linux_loader.rs

@@ -1,19 +1,21 @@
 //! This module implements the protocols to hand an initrd to the
 //! Linux kernel.
 
-use core::{ffi::c_void, pin::Pin, ptr::slice_from_raw_parts_mut};
+use core::{ffi::c_void, ops::Range, pin::Pin, ptr::slice_from_raw_parts_mut};
 
-use alloc::{boxed::Box, vec};
+use alloc::boxed::Box;
 use uefi::{
     prelude::BootServices,
     proto::{
         device_path::{DevicePath, FfiDevicePath},
-        media::file::{File, FileInfo, RegularFile},
+        media::file::RegularFile,
         Protocol,
     },
     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
@@ -56,9 +58,22 @@ struct LoadFile2Protocol {
 
     // This is not part of the official protocol struct.
     file: RegularFile,
+    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,
@@ -66,20 +81,19 @@ impl LoadFile2Protocol {
         buffer_size: *mut usize,
         buffer: *mut c_void,
     ) -> Result<()> {
-        let mut fs_info_buf = vec![0; 128];
-        let fs_info = self
-            .file
-            .get_info::<FileInfo>(&mut fs_info_buf)
-            .map_err(|_| Status::INVALID_PARAMETER)?;
-        let fs_size = usize::try_from(fs_info.file_size()).unwrap();
-
-        if buffer.is_null() || unsafe { *buffer_size } < fs_size {
+        if buffer.is_null() || unsafe { *buffer_size } < self.initrd_size() {
             unsafe {
-                *buffer_size = fs_size;
+                *buffer_size = self.initrd_size();
             }
             return Err(Status::BUFFER_TOO_SMALL.into());
         };
 
+        self.file
+            .set_position(self.initrd_start().try_into().unwrap())?;
+        unsafe {
+            *buffer_size = self.initrd_size();
+        }
+
         let output_slice: &mut [u8] =
             unsafe { &mut *slice_from_raw_parts_mut(buffer as *mut u8, *buffer_size) };
 
@@ -107,11 +121,38 @@ pub struct InitrdLoader {
     registered: bool,
 }
 
+/// Returns the data range of the initrd in the PE binary.
+fn initrd_location(initrd_efi: &mut RegularFile) -> Result<Range<usize>> {
+    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")
+        .and_then(|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();
+
+            Some(Range {
+                start: section_start,
+                end: section_start + section_size,
+            })
+        })
+        .ok_or(Status::END_OF_FILE.into())
+}
+
 impl InitrdLoader {
-    pub fn new(boot_services: &BootServices, handle: Handle, file: RegularFile) -> Result<Self> {
+    pub fn new(
+        boot_services: &BootServices,
+        handle: Handle,
+        mut file: RegularFile,
+    ) -> Result<Self> {
+        let range = initrd_location(&mut file)?;
         let mut proto = Box::pin(LoadFile2Protocol {
             load_file: raw_load_file,
             file,
+            range,
         });
 
         unsafe {

rust/lanzaboote/src/main.rs

@@ -9,7 +9,6 @@ mod linux_loader;
 mod pe_section;
 mod uefi_helpers;
 
-use log::{debug, info};
 use uefi::{
     prelude::*,
     proto::{
@@ -21,8 +20,7 @@ use uefi::{
 
 use crate::{
     linux_loader::InitrdLoader,
-    pe_section::pe_section,
-    uefi_helpers::{booted_image_cmdline, booted_image_file, read_all},
+    uefi_helpers::{booted_image_cmdline, read_all},
 };
 
 fn print_logo(output: &mut Output) {
@@ -49,15 +47,6 @@ fn main(handle: Handle, mut system_table: SystemTable<Boot>) -> Status {
 
     print_logo(system_table.stdout());
 
-    {
-        let image_data =
-            read_all(&mut booted_image_file(system_table.boot_services()).unwrap()).unwrap();
-
-        if let Some(data) = pe_section(&image_data, ".osrel") {
-            info!("osrel = {}", core::str::from_utf8(data).unwrap_or("???"))
-        }
-    }
-
     let mut file_system = system_table
         .boot_services()
         .get_image_file_system(handle)
@@ -71,7 +60,11 @@ fn main(handle: Handle, mut system_table: SystemTable<Boot>) -> Status {
         .unwrap();
 
     let initrd = root
-        .open(cstr16!("initrd"), FileMode::Read, FileAttribute::empty())
+        .open(
+            cstr16!("initrd.efi"),
+            FileMode::Read,
+            FileAttribute::empty(),
+        )
         .unwrap()
         .into_regular_file()
         .unwrap();
@@ -80,8 +73,6 @@ fn main(handle: Handle, mut system_table: SystemTable<Boot>) -> Status {
     drop(root);
     drop(file_system);
 
-    debug!("Opened file");
-
     let kernel_cmdline = booted_image_cmdline(system_table.boot_services()).unwrap();
 
     let kernel_data = read_all(&mut file).unwrap();