pcr phases

Author: ElvishJerricco

Cargo.lock

@@ -56,6 +56,8 @@
             };
 
             sbattach = import ./installer/patched-sbattach.nix { inherit pkgs; };
+
+            pcrTest = pkgs.callPackage ./pcr-test.nix { inherit inputs; };
           });
 
       defaultPackage = forAllSystems ({ system, ... }: self.packages.${system}.package);

flake.lock

@@ -16,6 +16,7 @@ doctest = false
 chrono = { version = "0.4.23", default-features = false, features = [ "std", "clock" ] }
 lazy_static = "1.4.0"
 regex = { version = "1.7.1" }
+serde = "1.0.137"
 serde_json = "1.0.94"
 tempfile = "3.3.0"
 structopt = { version = "0.3.26", default-features = false }

flake.nix

@@ -1,10 +1,11 @@
+use std::io::Seek;
 use std::io::Write;
-use std::path::Path;
-use std::process::Command;
+use std::path::{Path, PathBuf};
+use std::process::{Command, Stdio};
 
 use tempfile::NamedTempFile;
 
-use super::BootableToplevel;
+use super::{BootableToplevel, PcrPhase};
 use crate::Result;
 
 pub struct EfiProgram {
@@ -16,9 +17,17 @@ impl EfiProgram {
         Self { source }
     }
 
-    pub fn write_unified_efi(&self, objcopy: &Path, outpath: &Path, stub: &Path) -> Result<()> {
+    pub fn write_unified_efi(
+        &self,
+        objcopy: &Path,
+        systemd_measure: &Option<PathBuf>,
+        pcr_phases: &Option<Vec<PcrPhase>>,
+        outpath: &Path,
+        stub: &Path,
+    ) -> Result<()> {
         let generation_path = &self.source.toplevel.0;
         let mut kernel_params = NamedTempFile::new()?;
+        let mut pcr_sig = NamedTempFile::new()?;
 
         write!(
             kernel_params,
@@ -27,30 +36,75 @@ impl EfiProgram {
             self.source.kernel_params.join(" ")
         )?;
 
+        write!(pcr_sig, "{{}}")?;
+
+        if let Some(pcr_phases) = pcr_phases {
+            for phase in pcr_phases {
+                let mut cmd = Command::new(systemd_measure.as_ref().unwrap());
+                for bank in &phase.banks {
+                    cmd.args(["--bank", bank]);
+                }
+                cmd.args([
+                    "--osrel",
+                    &format!("{}/etc/os-release", generation_path.display()),
+                    "--cmdline",
+                    &format!("{}", kernel_params.path().display()),
+                    "--linux",
+                    &format!("{}/kernel", generation_path.display()),
+                    "--initrd",
+                    &format!("{}/initrd", generation_path.display()),
+                    "--phase",
+                    &phase.phase_path.to_string(),
+                    "--private-key",
+                    &format!("{}", phase.private_key_file.display()),
+                    "--public-key",
+                    &format!("{}", phase.public_key_file.display()),
+                    "--append",
+                    &format!("{}", pcr_sig.path().display()),
+                    "sign",
+                ]);
+                let output = cmd.stderr(Stdio::inherit()).output()?;
+
+                if !output.status.success() {
+                    return Err("failed to sign measurement".into());
+                }
+                pcr_sig.rewind()?;
+                pcr_sig.as_file().set_len(0)?;
+                pcr_sig.write_all(&output.stdout)?;
+            }
+        }
+
         // Offsets taken from one of systemd's EFI tests:
         // https://github.com/systemd/systemd/blob/01d0123f044d6c090b6ac2f6d304de2bdb19ae3b/test/test-efi-create-disk.sh#L32-L38
-        let status = Command::new(objcopy)
-            .args(&[
-                "--add-section",
-                &format!(".osrel={}/etc/os-release", generation_path.display()),
-                "--change-section-vma",
-                ".osrel=0x20000",
+        let mut cmd = Command::new(objcopy);
+        cmd.args([
+            "--add-section",
+            &format!(".osrel={}/etc/os-release", generation_path.display()),
+            "--change-section-vma",
+            ".osrel=0x20000",
+            "--add-section",
+            &format!(".cmdline={}", kernel_params.path().display()),
+            "--change-section-vma",
+            ".cmdline=0x30000",
+            "--add-section",
+            &format!(".linux={}/kernel", generation_path.display()),
+            "--change-section-vma",
+            ".linux=0x2000000",
+            "--add-section",
+            &format!(".initrd={}/initrd", generation_path.display()),
+            "--change-section-vma",
+            ".initrd=0x3000000",
+        ]);
+        if pcr_phases.is_some() {
+            cmd.args([
                 "--add-section",
-                &format!(".cmdline={}", kernel_params.path().display()),
+                &format!(".pcrsig={}", pcr_sig.path().display()),
                 "--change-section-vma",
-                ".cmdline=0x30000",
-                "--add-section",
-                &format!(".linux={}/kernel", generation_path.display()),
-                "--change-section-vma",
-                ".linux=0x2000000",
-                "--add-section",
-                &format!(".initrd={}/initrd", generation_path.display()),
-                "--change-section-vma",
-                ".initrd=0x3000000",
-                &stub.display().to_string(),
-                &outpath.display().to_string(),
-            ])
-            .status()?;
+                ".pcrsig=0x40000",
+            ]);
+        }
+        cmd.args([&stub.display().to_string(), &outpath.display().to_string()]);
+        let status = cmd.status()?;
 
         if !status.success() {
             return Err("failed to write unified efi".into());

generator/Cargo.toml

@@ -5,9 +5,11 @@ use bootspec::SpecialisationName;
 use crate::{Generation, Result};
 
 mod efi;
+mod pcr;
 mod toplevel;
 
 pub use efi::EfiProgram;
+pub use pcr::PcrPhase;
 pub use toplevel::BootableToplevel;
 
 pub enum Bootable {

generator/src/bootable/efi.rs

@@ -0,0 +1,11 @@
+use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
+
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct PcrPhase {
+    pub phase_path: String,
+    pub banks: Vec<String>,
+    pub private_key_file: PathBuf,
+    pub public_key_file: PathBuf,
+}

generator/src/bootable/mod.rs

@@ -1,6 +1,7 @@
+use std::fs;
 use std::path::PathBuf;
 
-use generator::bootable::{self, Bootable, EfiProgram};
+use generator::bootable::{self, Bootable, EfiProgram, PcrPhase};
 use generator::{systemd_boot, Generation, Result};
 use structopt::StructOpt;
 
@@ -13,6 +14,12 @@ struct Args {
     /// The `objcopy` binary
     #[structopt(long, requires_all = &["systemd-efi-stub", "unified-efi"])]
     objcopy: Option<PathBuf>,
+    /// The `systemd-measure` binary
+    #[structopt(long, requires_all = &["systemd-efi-stub", "unified-efi"])]
+    systemd_measure: Option<PathBuf>,
+    /// The pcr phase spec json file
+    #[structopt(long, requires_all = &["systemd-efi-stub", "unified-efi"])]
+    pcr_phases: Option<PathBuf>,
     /// Whether or not to combine the initrd and kernel into a unified EFI file
     #[structopt(long, requires_all = &["systemd-efi-stub", "objcopy"])]
     unified_efi: bool,
@@ -58,9 +65,16 @@ fn main() -> Result<()> {
         toplevels.into_iter().map(Bootable::Linux).collect()
     };
 
+    let pcr_phases: Option<Vec<PcrPhase>> = args.pcr_phases.map(|json_path| {
+        let cont = fs::read_to_string(json_path).unwrap();
+        serde_json::from_str(&cont).unwrap()
+    });
+
     systemd_boot::generate(
         bootables,
         args.objcopy,
+        args.systemd_measure,
+        pcr_phases,
         args.systemd_efi_stub,
         args.systemd_machine_id_setup,
     )?;

generator/src/bootable/pcr.rs

@@ -6,7 +6,7 @@ use std::process::Command;
 
 use bootspec::SpecialisationName;
 
-use crate::bootable::{Bootable, BootableToplevel, EfiProgram};
+use crate::bootable::{Bootable, BootableToplevel, EfiProgram, PcrPhase};
 use crate::Result;
 
 // FIXME: placeholder dir
@@ -38,6 +38,8 @@ pub struct Contents {
 pub fn generate(
     bootables: Vec<Bootable>,
     objcopy: Option<PathBuf>,
+    systemd_measure: Option<PathBuf>,
+    pcr_phases: Option<Vec<PcrPhase>>,
     systemd_efi_stub: Option<PathBuf>,
     systemd_machine_id_setup: PathBuf,
 ) -> Result<()> {
@@ -58,7 +60,13 @@ pub fn generate(
                 let objcopy = objcopy.as_ref().unwrap();
                 let systemd_efi_stub = systemd_efi_stub.as_ref().unwrap();
 
-                efi.write_unified_efi(objcopy, Path::new(&unified_dest), systemd_efi_stub)?;
+                efi.write_unified_efi(
+                    objcopy,
+                    &systemd_measure,
+                    &pcr_phases,
+                    Path::new(&unified_dest),
+                    systemd_efi_stub,
+                )?;
             }
             Bootable::Linux(toplevel) => {
                 let (path, contents) = self::linux_entry_impl(&toplevel, &machine_id)?;

generator/src/main.rs

@@ -14,9 +14,59 @@ in
         type = types.nullOr types.str;
         default = null;
       };
+
+      pcrPhases = {
+        enable = lib.mkEnableOption "pcr phases";
+
+        signatures = lib.mkOption {
+          default = {};
+          type = types.attrsOf (types.submodule ({ name, ... }: {
+            config.phasePath = lib.mkDefault name;
+            options = {
+              phasePath = lib.mkOption {
+                type = types.str;
+              };
+              banks = lib.mkOption {
+                type = types.listOf types.str;
+                default = [];
+              };
+              privateKeyFile = lib.mkOption {
+                type = types.path // { apply = toString; };
+              };
+              publicKeyFile = lib.mkOption {
+                type = types.path // { apply = toString; };
+              };
+            };
+          }));
+        };
+      };
     };
   };
   config = {
+    boot.kernelParams = lib.mkIf config.boot.loader.secureboot.pcrPhases.enable ["systemd.gpt_auto=false"];
+    boot.initrd = lib.mkIf config.boot.loader.secureboot.pcrPhases.enable {
+      availableKernelModules = ["efivarfs"];
+      systemd = {
+        package = config.systemd.package;
+        additionalUpstreamUnits = ["systemd-pcrphase-initrd.service"];
+        services.systemd-pcrphase-initrd = {
+          wantedBy = ["initrd.target"];
+          after = ["systemd-modules-load.service"];
+        };
+        storePaths = ["${config.boot.initrd.systemd.package}/lib/systemd/systemd-pcrphase"];
+        contents."/etc/tmpfiles.d/90-tpm-pcr-signature.conf".text = ''
+          C /run/systemd/tpm2-pcr-signature.json - - - - /.extra/tpm2-pcr-signature.json
+        '';
+      };
+    };
+    systemd = lib.mkIf config.boot.loader.secureboot.pcrPhases.enable {
+      additionalUpstreamSystemUnits = [
+        "systemd-pcrphase-sysinit.service"
+        "systemd-pcrphase.service"
+      ];
+      services.systemd-pcrphase-sysinit.wantedBy = ["basic.target"];
+      services.systemd-pcrphase.wantedBy = ["multi-user.target"];
+    };
     boot.loader.external = {
       enable = true;
       installHook = pkgs.writeShellScript "install-bootloader"
@@ -34,6 +84,11 @@ in
 
               "--systemd-efi-stub"
               "${config.systemd.package}/lib/systemd/boot/efi/linuxx64.efi.stub"
+            ] ++ lib.optionals config.boot.loader.secureboot.pcrPhases.enable [
+              "--systemd-measure"
+              "${config.systemd.package}/lib/systemd/systemd-measure"
+              "--pcr-phases"
+              (pkgs.writeText "pcr-phases" (builtins.toJSON (lib.mapAttrsToList (n: v: v) config.boot.loader.secureboot.pcrPhases.signatures)))
             ]));
 
             installerArgs = lib.escapeShellArgs