Load ELF from memory using memfd_create

unshell-lib/src/module/mod.rs

@@ -1,6 +1,8 @@
 mod manager;
 mod module;
 
+mod proc_load;
+
 // use std::any::Any;
 
 // pub use logger::setup_logger;

unshell-lib/src/module/module.rs

@@ -1,5 +1,6 @@
 use libloading::{Library, Symbol};
 
+use crate::module::proc_load::memfd_create_dlopen;
 use crate::{ModuleError, logger::SetupLogger, logger::logger};
 
 use crate::*;
@@ -22,26 +23,27 @@ impl Module {
 
         Ok(this)
     }
+
+    // TODO: Implement actual reflective ELF loading (possibly even custom format)
+    // Look at https://github.com/weizhiao/rust-elfloader
+    pub fn new_bytes(bytes: &[u8]) -> Result<Self, ModuleError> {
+        let lib =
+            memfd_create_dlopen(bytes).map_err(|e| ModuleError::Error(e.to_string().into()))?;
+
+        let this = Self { lib };
+
+        if let Ok(setup_logger) = this.get_symbol::<SetupLogger>(b"setup_logger") {
+            setup_logger(logger());
+        } else {
+            warn!("setup_logger not found");
+        }
+
+        Ok(this)
+    }
     pub fn get_symbol<T>(&self, symbol: &[u8]) -> Result<Symbol<'_, T>, ModuleError> {
         let symbol = unsafe { self.lib.get::<T>(symbol) }
             .map_err(|e| ModuleError::LinkError(format!("Failed to load symbol: {}", e)))?;
 
         Ok(symbol)
     }
-    // pub fn get_id(&self) -> &str {
-    //     self.id
-    // }
-    // pub fn get_interface<T>(&self) -> Result<T, ModuleError> {
-    //     if let Ok(interface_function) = self.get_symbol::<fn() -> T>(b"interface") {
-    //         Ok(interface_function())
-    //     } else {
-    //         Err(ModuleError::LinkError(format!(
-    //             "Interface function not found!"
-    //         )))
-    //     }
-    // }
 }
-
-// extern "C" fn test1234() {
-//     info!("Test1234!");
-// }

unshell-lib/src/module/proc_load.rs

@@ -0,0 +1,56 @@
+// Load a shared object by saving bytes to a filesystem in /proc
+
+use std::{error::Error, ffi::CString, io}; // 0.8
+
+use libloading::Library;
+
+use crate::debug;
+
+// The `memfd_create` syscall flags (MFD_CLOEXEC is common and good practice)
+const MFD_CLOEXEC: u32 = 0x0001;
+const MFD_ALLOW_SEALING: u32 = 0x0002;
+
+pub fn memfd_create_dlopen(payload: &[u8]) -> Result<Library, Box<dyn Error>> {
+    use rand::distr::{Alphanumeric, SampleString};
+
+    let string = Alphanumeric.sample_string(&mut rand::rng(), 16);
+
+    // 1. Create the anonymous in-memory file descriptor using the raw syscall
+    let c_name = CString::new(string).expect("CString conversion failed");
+
+    let fd = unsafe { libc::memfd_create(c_name.as_ptr(), MFD_CLOEXEC | MFD_ALLOW_SEALING) };
+
+    if fd < 0 {
+        return Err(io::Error::last_os_error().to_string().into());
+    }
+
+    // 2. Write the payload bytes to the in-memory file
+    let bytes_written =
+        unsafe { libc::write(fd, payload.as_ptr() as *const libc::c_void, payload.len()) };
+
+    if bytes_written != payload.len() as isize {
+        // If write fails or is incomplete, clean up the file descriptor
+        unsafe {
+            libc::close(fd);
+        }
+        return Err("Failed to write full payload to memfd".into());
+    }
+
+    // Optional: Seal the file to prevent modification, common for security/integrity
+    // Note: The MFD_ALLOW_SEALING flag must be set during creation for this to work.
+    let seals = libc::F_SEAL_GROW | libc::F_SEAL_SHRINK | libc::F_SEAL_WRITE;
+    if unsafe { libc::fcntl(fd, libc::F_ADD_SEALS, seals) } == -1 {
+        // Log a warning but continue if sealing fails (e.g., due to permissions)
+        debug!(
+            "memfd_create_dlopen: Failed to apply seals. Error: {}",
+            io::Error::last_os_error()
+        );
+    }
+
+    // 3. Construct the virtual path to the in-memory file
+    // This path is necessary for dlopen to work, as dlopen expects a filesystem path.
+    let dl_path = format!("/proc/self/fd/{}", fd);
+
+    // 4. Use dlopen (via libloading) on the virtual path
+    Ok(unsafe { Library::new(&dl_path)? })
+}