feat(secure-boot): add support for SBAT section

Author: azenla

build.rs

@@ -0,0 +1,57 @@
+use std::path::PathBuf;
+use std::{env, fs};
+
+/// The size of the sbat.csv file.
+const SBAT_SIZE: usize = 512;
+
+/// Generate the sbat.csv for the .sbat link section.
+///
+/// We intake a sbat.template.tsv and output a sbat.csv which is included by src/sbat.rs
+fn generate_sbat_csv() {
+    // Notify Cargo that if the Sprout version changes, we need to regenerate the sbat.csv.
+    println!("cargo:rerun-if-env-changed=CARGO_PKG_VERSION");
+
+    // The version of the sprout crate.
+    let sprout_version = env::var("CARGO_PKG_VERSION").expect("CARGO_PKG_VERSION not set");
+
+    // The output directory to place the sbat.csv into.
+    let output_dir = PathBuf::from(env::var("OUT_DIR").expect("OUT_DIR not set"));
+
+    // The output path to the sbat.csv.
+    let output_file = output_dir.join("sbat.csv");
+
+    // The path to the root of the sprout crate.
+    let sprout_root =
+        PathBuf::from(env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR not set"));
+
+    // The path to the sbat.template.tsv file is in the source directory of the sprout crate.
+    let template_path = sprout_root.join("src/sbat.template.csv");
+
+    // Read the sbat.csv template file.
+    let template = fs::read_to_string(&template_path).expect("unable to read template file");
+
+    // Replace the version placeholder in the template with the actual version.
+    let sbat = template.replace("{version}", &sprout_version);
+
+    // Encode the sbat.csv as bytes.
+    let mut encoded = sbat.as_bytes().to_vec();
+
+    if encoded.len() > SBAT_SIZE {
+        panic!("sbat.csv is too large");
+    }
+
+    // Pad the sbat.csv to the required size.
+    while encoded.len() < SBAT_SIZE {
+        encoded.push(0);
+    }
+
+    // Write the sbat.csv to the output directory.
+    fs::write(&output_file, encoded).expect("unable to write sbat.csv");
+}
+
+/// Build script entry point.
+/// Right now, all we need to do is generate the sbat.csv file.
+fn main() {
+    // Generate the sbat.csv file.
+    generate_sbat_csv();
+}

src/main.rs

@@ -59,6 +59,9 @@ pub mod integrations;
 /// phases: Hooks into specific parts of the boot process.
 pub mod phases;
 
+/// sbat: Secure Boot Attestation section.
+pub mod sbat;
+
 /// secure: Secure Boot support.
 pub mod secure;
 

src/sbat.rs

@@ -0,0 +1,8 @@
+/// SBAT must be aligned by 512 bytes.
+const SBAT_SIZE: usize = 512;
+
+/// Define the SBAT attestation by including the sbat.csv file.
+/// See this document for more details: https://github.com/rhboot/shim/blob/main/SBAT.md
+#[used]
+#[unsafe(link_section = ".sbat")]
+static SBAT: [u8; SBAT_SIZE] = *include_bytes!(concat!(env!("OUT_DIR"), "/sbat.csv"));

src/sbat.template.csv

@@ -0,0 +1,2 @@
+sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
+sprout,1,Edera,sprout,{version},https://sprout.edera.dev