tpm: Add tpm2-sys crate

This CL adds a tpm2-sys crate that builds libtpm2 from source (from a
git submodule) using the existing Makefile and then links the generated
static library as -ltpm2.

For production builds there is a flag `RUSTFLAGS='--cfg hermetic'` to
disallow building our own libtpm2. Instead it will expect to find
libtpm2 installed in the standard system location. Building from the
libtpm2 submodule is a convenience only intended for developer
environments.

The functions exposed by tpm2-sys are the ones that will be necessary to
initialize a TPM simulator in crosvm and execute TPM commands. Trunks
uses the same functions for its simulator mode here:

    https://chromium.googlesource.com/chromiumos/platform2/+/e4cf13c05773f3446bd76a13c4e37f0b80728711/trunks/tpm_simulator_handle.cc

Tested by running:

    fn main() {
        unsafe {
            tpm2_sys::TPM_Manufacture(1);
        }
    }

inside cros_sdk. Libtpm2 cannot be built outside of cros_sdk because it
requires openssl 1.0.2p, whereas dev machines come with openssl 1.1.0j.

I have not yet added any dependency on tpm2-sys from crosvm, but when it
does get added it will be behind a tpm feature flag so that crosvm can
continue to build outside of cros_sdk just without tpm support.

I published num_cpus version 1.9.0 to chromeos-localmirror.

TEST=running the code snippet above as described
BUG=chromium:911799

Change-Id: I097729bc447f9dc95e39959a426d1ac42f46b16d
Reviewed-on: https://chromium-review.googlesource.com/1396280
Commit-Ready: David Tolnay <dtolnay@chromium.org>
Tested-by: David Tolnay <dtolnay@chromium.org>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>

4 files changed, 78 insertions, 0 deletions

diff --git a/tpm2-sys/Cargo.toml b/tpm2-sys/Cargo.toml
new file mode 100644
index 0000000..0297bf0
--- /dev/null
+++ b/tpm2-sys/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "tpm2-sys"
+version = "0.1.0"
+authors = ["The Chromium OS Authors"]
+edition = "2018"
+links = "tpm2"
+
+[build-dependencies]
+num_cpus = "*"
+pkg-config = "*"
+
+[workspace]
diff --git a/tpm2-sys/build.rs b/tpm2-sys/build.rs
new file mode 100644
index 0000000..f1abd4a
--- /dev/null
+++ b/tpm2-sys/build.rs
@@ -0,0 +1,48 @@
+// Copyright 2019 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+use std::env;
+use std::io;
+use std::path::Path;
+use std::process::{self, Command};
+
+fn main() -> io::Result<()> {
+    println!("cargo:rustc-link-lib=ssl");
+    println!("cargo:rustc-link-lib=crypto");
+
+    if pkg_config::probe_library("libtpm2").is_ok() {
+        // Use tpm2 package from the standard system location if available.
+        return Ok(());
+    }
+
+    // Build with `RUSTFLAGS='--cfg hermetic'` to disallow building our own
+    // libtpm2 in a production build context. Building from the libtpm2
+    // submodule is a convenience only intended for developer environments.
+    if cfg!(hermetic) {
+        eprintln!("libtpm2 not found; unable to perform hermetic build");
+        process::exit(1);
+    }
+
+    if !Path::new("libtpm2/.git").exists() {
+        Command::new("git")
+            .args(&["submodule", "update", "--init"])
+            .status()?;
+    }
+
+    if !Path::new("libtpm2/build/libtpm2.a").exists() {
+        let ncpu = num_cpus::get();
+        let status = Command::new("make")
+            .arg(format!("-j{}", ncpu))
+            .current_dir("libtpm2")
+            .status()?;
+        if !status.success() {
+            process::exit(status.code().unwrap_or(1));
+        }
+    }
+
+    let dir = env::var("CARGO_MANIFEST_DIR").unwrap();
+    println!("cargo:rustc-link-search={}/libtpm2/build", dir);
+    println!("cargo:rustc-link-lib=static=tpm2");
+    Ok(())
+}
diff --git a/tpm2-sys/libtpm2 b/tpm2-sys/libtpm2
new file mode 160000
+Subproject 15260c8cd98eb10b4976d2161cd5cb9bc0c3ada
diff --git a/tpm2-sys/src/lib.rs b/tpm2-sys/src/lib.rs
new file mode 100644
index 0000000..456cc87
--- /dev/null
+++ b/tpm2-sys/src/lib.rs
@@ -0,0 +1,18 @@
+// Copyright 2019 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+use std::os::raw::{c_int, c_uchar, c_uint};
+
+extern "C" {
+    pub fn TPM_Manufacture(firstTime: c_int) -> c_int;
+    pub fn _plat__SetNvAvail();
+    pub fn _plat__Signal_PowerOn() -> c_int;
+    pub fn _TPM_Init();
+    pub fn ExecuteCommand(
+        requestSize: c_uint,
+        request: *mut c_uchar,
+        responseSize: *mut c_uint,
+        response: *mut *mut c_uchar,
+    );
+}