Merge pull request #319 from lifupan/device_cgroup

Port rootfs access fix to rust agent

src/agent/src/device.rs

@@ -4,6 +4,7 @@
 //
 
 use libc::{c_uint, major, minor};
+use nix::sys::stat;
 use std::collections::HashMap;
 use std::fs;
 use std::os::unix::fs::MetadataExt;
@@ -14,7 +15,7 @@ use crate::linux_abi::*;
 use crate::mount::{DRIVERBLKTYPE, DRIVERMMIOBLKTYPE, DRIVERNVDIMMTYPE, DRIVERSCSITYPE};
 use crate::sandbox::Sandbox;
 use crate::{AGENT_CONFIG, GLOBAL_DEVICE_WATCHER};
-use oci::Spec;
+use oci::{LinuxDeviceCgroup, LinuxResources, Spec};
 use protocols::agent::Device;
 use rustjail::errors::*;
 
@@ -25,6 +26,8 @@ macro_rules! sl {
     };
 }
 
+const VM_ROOTFS: &str = "/";
+
 // DeviceHandler is the type of callback to be defined to handle every type of device driver.
 type DeviceHandler = fn(&Device, &mut Spec, &Arc<Mutex<Sandbox>>) -> Result<()>;
 
@@ -360,3 +363,63 @@ fn add_device(device: &Device, spec: &mut Spec, sandbox: &Arc<Mutex<Sandbox>>) -
         Some(dev_handler) => dev_handler(device, spec, sandbox),
     }
 }
+
+// update_device_cgroup update the device cgroup for container
+// to not allow access to the guest root partition. This prevents
+// the container from being able to access the VM rootfs.
+pub fn update_device_cgroup(spec: &mut Spec) -> Result<()> {
+    let meta = fs::metadata(VM_ROOTFS)?;
+    let rdev = meta.dev();
+    let major = stat::major(rdev) as i64;
+    let minor = stat::minor(rdev) as i64;
+
+    let linux = match spec.linux.as_mut() {
+        None => {
+            return Err(
+                ErrorKind::ErrorCode("Spec didn't container linux field".to_string()).into(),
+            )
+        }
+        Some(l) => l,
+    };
+
+    if linux.resources.is_none() {
+        linux.resources = Some(LinuxResources::default());
+    }
+
+    let resources = linux.resources.as_mut().unwrap();
+    resources.devices.push(LinuxDeviceCgroup {
+        allow: false,
+        major: Some(major),
+        minor: Some(minor),
+        r#type: String::from("b"),
+        access: String::from("rwm"),
+    });
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use oci::Linux;
+
+    #[test]
+    fn test_update_device_cgroup() {
+        let mut spec = Spec::default();
+
+        spec.linux = Some(Linux::default());
+
+        update_device_cgroup(&mut spec).unwrap();
+
+        let devices = spec.linux.unwrap().resources.unwrap().devices;
+        assert_eq!(devices.len(), 1);
+
+        let meta = fs::metadata(VM_ROOTFS).unwrap();
+        let rdev = meta.dev();
+        let major = stat::major(rdev) as i64;
+        let minor = stat::minor(rdev) as i64;
+
+        assert_eq!(devices[0].major, Some(major));
+        assert_eq!(devices[0].minor, Some(minor));
+    }
+}

src/agent/src/main.rs

@@ -31,6 +31,7 @@ use nix::fcntl::{self, OFlag};
 use nix::sys::socket::{self, AddressFamily, SockAddr, SockFlag, SockType};
 use nix::sys::wait::{self, WaitStatus};
 use nix::unistd;
+use nix::unistd::dup;
 use prctl::set_child_subreaper;
 use rustjail::errors::*;
 use signal_hook::{iterator::Signals, SIGCHLD};
@@ -117,6 +118,12 @@ fn main() -> Result<()> {
     let agentConfig = AGENT_CONFIG.clone();
 
     if unistd::getpid() == Pid::from_raw(1) {
+        // dup a new file descriptor for this temporary logger writer,
+        // since this logger would be dropped and it's writer would
+        // be closed out of this code block.
+        let newwfd = dup(wfd)?;
+        let writer = unsafe { File::from_raw_fd(newwfd) };
+
         // Init a temporary logger used by init agent as init process
         // since before do the base mount, it wouldn't access "/proc/cmdline"
         // to get the customzied debug level.

src/agent/src/rpc.rs

@@ -29,7 +29,7 @@ use nix::sys::stat;
 use nix::unistd::{self, Pid};
 use rustjail::process::ProcessOperations;
 
-use crate::device::{add_devices, rescan_pci_bus};
+use crate::device::{add_devices, rescan_pci_bus, update_device_cgroup};
 use crate::linux_abi::*;
 use crate::mount::{add_storages, remove_mounts, STORAGEHANDLERLIST};
 use crate::namespace::{NSTYPEIPC, NSTYPEPID, NSTYPEUTS};
@@ -121,6 +121,9 @@ impl agentService {
 
         update_container_namespaces(&s, &mut oci)?;
 
+        // Add the root partition to the device cgroup to prevent access
+        update_device_cgroup(&mut oci)?;
+
         // write spec to bundle path, hooks might
         // read ocispec
         let olddir = setup_bundle(&oci)?;