From 35a2e4d002f244b7b97ddf6be847ffc86ed73e34 Mon Sep 17 00:00:00 2001
From: Aaron Kaiser <a_kaiser@posteo.de>
Date: Thu, 18 Apr 2024 15:41:29 +0200
Subject: [PATCH] Initial commit

---
 .gitignore          |  1 +
 Cargo.lock          | 31 +++++++++++++++
 Cargo.toml          | 11 ++++++
 rust-toolchain.toml |  2 +
 src/agent.rs        | 92 +++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs          | 25 ++++++++++++
 6 files changed, 162 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 rust-toolchain.toml
 create mode 100644 src/agent.rs
 create mode 100644 src/lib.rs

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..de82d80
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,31 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "agent_lib"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "libc",
+ "shared_memory_heap",
+]
+
+[[package]]
+name = "anyhow"
+version = "1.0.82"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f538837af36e6f6a9be0faa67f9a314f8119e4e4b5867c6ab40ed60360142519"
+
+[[package]]
+name = "libc"
+version = "0.2.153"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c198f91728a82281a64e1f4f9eeb25d82cb32a5de251c6bd1b5154d63a8e7bd"
+
+[[package]]
+name = "shared_memory_heap"
+version = "0.1.0"
+dependencies = [
+ "libc",
+]
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..f17db80
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "agent_lib"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0.82"
+libc = "0.2.153"
+shared_memory_heap = { path = "../shared_memory_heap" }
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
new file mode 100644
index 0000000..5d56faf
--- /dev/null
+++ b/rust-toolchain.toml
@@ -0,0 +1,2 @@
+[toolchain]
+channel = "nightly"
diff --git a/src/agent.rs b/src/agent.rs
new file mode 100644
index 0000000..490b565
--- /dev/null
+++ b/src/agent.rs
@@ -0,0 +1,92 @@
+use anyhow::{bail, Result};
+use libc::{
+    c_char, c_void, execve, fork, ftruncate, memfd_create, mmap, syscall, SYS_futex, FUTEX_WAIT,
+    FUTEX_WAKE, MAP_SHARED, PROT_READ,
+};
+use shared_memory_heap::get_shared_mem_fd;
+use std::{ffi::CString, path::Path, ptr, usize};
+
+pub struct Agent {
+    sync_mem: *mut usize,
+}
+
+unsafe impl Send for Agent {}
+
+impl Agent {
+    pub(crate) unsafe fn new(path: &Path) -> Result<Self> {
+        let data_fd = get_shared_mem_fd();
+        let sync_fd = memfd_create("sync\x00".as_ptr() as *const c_char, 0);
+
+        let err = ftruncate(sync_fd, 1024);
+        if err != 0 {
+            bail!("ftruncate failed");
+        }
+
+        let sync_mem = mmap(
+            ptr::null_mut::<c_void>(),
+            1024,
+            PROT_READ | PROT_READ,
+            MAP_SHARED,
+            sync_fd,
+            0,
+        ) as *mut usize;
+
+        if sync_mem == ptr::null_mut() {
+            bail!("mmap failed");
+        }
+
+        let child = fork();
+
+        if child == 0 {
+            // child
+
+            let data_fd = CString::new(data_fd.to_string()).unwrap();
+            let sync_fd = CString::new(sync_fd.to_string()).unwrap();
+            let args = [data_fd.as_ptr(), sync_fd.as_ptr()];
+
+            execve(
+                path.as_os_str().as_encoded_bytes().as_ptr() as *const c_char,
+                args.as_ptr(),
+                ptr::null(),
+            );
+
+            panic!("execve failed");
+        }
+
+        // parent
+
+        Ok(Agent {
+            sync_mem,
+        })
+    }
+
+    pub(crate) unsafe fn perform_ipc_call(&mut self, call_id: usize, ptrs: &[usize]) {
+        *self.sync_mem.add(1) = call_id;
+
+        for (i, ptr) in ptrs.iter().enumerate() {
+            *self.sync_mem.add(i + 1) = *ptr;
+        }
+
+        // wake agent
+        syscall(
+            SYS_futex,
+            self.sync_mem,
+            FUTEX_WAKE,
+            1,
+            ptr::null::<u8>(),
+            ptr::null::<u8>(),
+            0,
+        );
+
+        // wait for agent to be finished
+        syscall(
+            SYS_futex,
+            self.sync_mem,
+            FUTEX_WAIT,
+            0,
+            ptr::null::<u8>(),
+            ptr::null::<u8>(),
+            0,
+        );
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..1148e8b
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,25 @@
+#![feature(lazy_cell)]
+
+mod agent;
+
+pub use shared_memory_heap::sharedptr::SharedPtr;
+
+use agent::Agent;
+use std::{
+    path::Path,
+    sync::{LazyLock, Mutex},
+};
+
+static AGENT: LazyLock<Mutex<Agent>> = LazyLock::new(|| {
+    let agent_path = std::env::var("AGENT_PATH").expect("AGENT_PATH environment variable missing");
+    let agent = unsafe { Agent::new(Path::new(&agent_path)).expect("Agent failed to start") };
+    Mutex::new(agent)
+});
+
+pub fn x25519(out: &mut SharedPtr, pk: &SharedPtr, sk: &SharedPtr) {
+    let mut agent = AGENT.lock().unwrap();
+
+    unsafe {
+        agent.perform_ipc_call(1, &[out.get_offset(), pk.get_offset(), sk.get_offset()]);
+    }
+}