Merge pull request #4813 from ManaSugi/fix/add-selinux-agent

runtime,agent: Add SELinux support for containers inside the guest

docs/Developer-Guide.md

@@ -86,6 +86,27 @@ $ sudo sed -i '/^disable_guest_seccomp/ s/true/false/' /etc/kata-containers/conf
 
 This will pass container seccomp profiles to the kata agent.
 
+## Enable SELinux on the guest
+
+> **Note:**
+>
+> - To enable SELinux on the guest, SELinux MUST be also enabled on the host.
+> - You MUST create and build a rootfs image for SELinux in advance.
+>   See [Create a rootfs image](#create-a-rootfs-image) and [Build a rootfs image](#build-a-rootfs-image).
+> - SELinux on the guest is supported in only a rootfs image currently, so
+>   you cannot enable SELinux with the agent init (`AGENT_INIT=yes`) yet.
+
+Enable guest SELinux in Enforcing mode as follows:
+
+```
+$ sudo sed -i '/^disable_guest_selinux/ s/true/false/g' /etc/kata-containers/configuration.toml
+```
+
+The runtime automatically will set `selinux=1` to the kernel parameters and `xattr` option to
+`virtiofsd` when `disable_guest_selinux` is set to `false`.
+
+If you want to enable SELinux in Permissive mode, add `enforcing=0` to the kernel parameters.
+
 ## Enable full debug
 
 Enable full debug as follows:
@@ -256,6 +277,12 @@ If you want to build the agent without seccomp capability, you need to run the `
 $ script -fec 'sudo -E AGENT_INIT=yes USE_DOCKER=true SECCOMP=no ./rootfs.sh "${distro}"'
 ```
 
+If you want to enable SELinux on the guest, you MUST choose `centos` and run the `rootfs.sh` script with `SELINUX=yes` as follows.
+
+```
+$ script -fec 'sudo -E GOPATH=$GOPATH USE_DOCKER=true SELINUX=yes ./rootfs.sh centos'
+```
+
 > **Note:**
 >
 > - Check the [compatibility matrix](../tools/osbuilder/README.md#platform-distro-compatibility-matrix) before creating rootfs.
@@ -283,6 +310,19 @@ $ script -fec 'sudo -E USE_DOCKER=true ./image_builder.sh "${ROOTFS_DIR}"'
 $ popd
 ```
 
+If you want to enable SELinux on the guest, you MUST run the `image_builder.sh` script with `SELINUX=yes`
+to label the guest image as follows.
+To label the image on the host, you need to make sure that SELinux is enabled (`selinuxfs` is mounted) on the host
+and the rootfs MUST be created by running the `rootfs.sh` with `SELINUX=yes`.
+
+```
+$ script -fec 'sudo -E USE_DOCKER=true SELINUX=yes ./image_builder.sh ${ROOTFS_DIR}'
+```
+
+Currently, the `image_builder.sh` uses `chcon` as an interim solution in order to apply `container_runtime_exec_t`
+to the `kata-agent`. Hence, if you run `restorecon` to the guest image after running the `image_builder.sh`,
+the `kata-agent` needs to be labeled `container_runtime_exec_t` again by yourself.
+
 > **Notes:**
 >
 > - You must ensure that the *default Docker runtime* is `runc` to make use of

src/agent/Cargo.lock

@@ -1705,6 +1705,7 @@ dependencies = [
  "tempfile",
  "test-utils",
  "tokio",
+ "xattr",
  "zbus",
 ]
 
@@ -2478,6 +2479,15 @@ version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c811ca4a8c853ef420abd8592ba53ddbbac90410fab6903b3e79972a631f7680"
 
+[[package]]
+name = "xattr"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6d1526bbe5aaeb5eb06885f4d987bcdfa5e23187055de9b83fe00156a821fabc"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "zbus"
 version = "2.3.2"

src/agent/rustjail/Cargo.toml

@@ -35,6 +35,7 @@ inotify = "0.9.2"
 libseccomp = { version = "0.3.0", optional = true }
 zbus = "2.3.0"
 bit-vec= "0.6.3"
+xattr = "0.2.3"
 
 [dev-dependencies]
 serial_test = "0.5.0"

src/agent/rustjail/src/container.rs

@@ -30,6 +30,7 @@ use crate::log_child;
 use crate::process::Process;
 #[cfg(feature = "seccomp")]
 use crate::seccomp;
+use crate::selinux;
 use crate::specconv::CreateOpts;
 use crate::{mount, validator};
 
@@ -526,6 +527,8 @@ fn do_init_child(cwfd: RawFd) -> Result<()> {
         }
     }
 
+    let selinux_enabled = selinux::is_enabled()?;
+
     sched::unshare(to_new & !CloneFlags::CLONE_NEWUSER)?;
 
     if userns {
@@ -627,6 +630,18 @@ fn do_init_child(cwfd: RawFd) -> Result<()> {
         capctl::prctl::set_no_new_privs().map_err(|_| anyhow!("cannot set no new privileges"))?;
     }
 
+    // Set SELinux label
+    if !oci_process.selinux_label.is_empty() {
+        if !selinux_enabled {
+            return Err(anyhow!(
+                "SELinux label for the process is provided but SELinux is not enabled on the running kernel"
+            ));
+        }
+
+        log_child!(cfd_log, "Set SELinux label to the container process");
+        selinux::set_exec_label(&oci_process.selinux_label)?;
+    }
+
     // Log unknown seccomp system calls in advance before the log file descriptor closes.
     #[cfg(feature = "seccomp")]
     if let Some(ref scmp) = linux.seccomp {

src/agent/rustjail/src/lib.rs

@@ -38,6 +38,7 @@ pub mod pipestream;
 pub mod process;
 #[cfg(feature = "seccomp")]
 pub mod seccomp;
+pub mod selinux;
 pub mod specconv;
 pub mod sync;
 pub mod sync_with_async;

src/agent/rustjail/src/mount.rs

@@ -25,6 +25,7 @@ use std::fs::File;
 use std::io::{BufRead, BufReader};
 
 use crate::container::DEFAULT_DEVICES;
+use crate::selinux;
 use crate::sync::write_count;
 use std::string::ToString;
 
@@ -181,6 +182,8 @@ pub fn init_rootfs(
         None => flags |= MsFlags::MS_SLAVE,
     }
 
+    let label = &linux.mount_label;
+
     let root = spec
         .root
         .as_ref()
@@ -244,7 +247,7 @@ pub fn init_rootfs(
                 }
             }
 
-            mount_from(cfd_log, m, rootfs, flags, &data, "")?;
+            mount_from(cfd_log, m, rootfs, flags, &data, label)?;
             // bind mount won't change mount options, we need remount to make mount options
             // effective.
             // first check that we have non-default options required before attempting a
@@ -524,7 +527,6 @@ pub fn pivot_rootfs<P: ?Sized + NixPath + std::fmt::Debug>(path: &P) -> Result<(
 
 fn rootfs_parent_mount_private(path: &str) -> Result<()> {
     let mount_infos = parse_mount_table(MOUNTINFO_PATH)?;
-
     let mut max_len = 0;
     let mut mount_point = String::from("");
     let mut options = String::from("");
@@ -767,9 +769,9 @@ fn mount_from(
     rootfs: &str,
     flags: MsFlags,
     data: &str,
-    _label: &str,
+    label: &str,
 ) -> Result<()> {
-    let d = String::from(data);
+    let mut d = String::from(data);
     let dest = secure_join(rootfs, &m.destination);
 
     let src = if m.r#type.as_str() == "bind" {
@@ -822,6 +824,37 @@ fn mount_from(
         e
     })?;
 
+    // Set the SELinux context for the mounts
+    let mut use_xattr = false;
+    if !label.is_empty() {
+        if selinux::is_enabled()? {
+            let device = Path::new(&m.source)
+                .file_name()
+                .ok_or_else(|| anyhow!("invalid device source path: {}", &m.source))?
+                .to_str()
+                .ok_or_else(|| anyhow!("failed to convert device source path: {}", &m.source))?;
+
+            match device {
+                // SELinux does not support labeling of /proc or /sys
+                "proc" | "sysfs" => (),
+                // SELinux does not support mount labeling against /dev/mqueue,
+                // so we use setxattr instead
+                "mqueue" => {
+                    use_xattr = true;
+                }
+                _ => {
+                    log_child!(cfd_log, "add SELinux mount label to {}", dest.as_str());
+                    selinux::add_mount_label(&mut d, label);
+                }
+            }
+        } else {
+            log_child!(
+                cfd_log,
+                "SELinux label for the mount is provided but SELinux is not enabled on the running kernel"
+            );
+        }
+    }
+
     mount(
         Some(src.as_str()),
         dest.as_str(),
@@ -834,6 +867,10 @@ fn mount_from(
         e
     })?;
 
+    if !label.is_empty() && selinux::is_enabled()? && use_xattr {
+        xattr::set(dest.as_str(), "security.selinux", label.as_bytes())?;
+    }
+
     if flags.contains(MsFlags::MS_BIND)
         && flags.intersects(
             !(MsFlags::MS_REC

src/agent/rustjail/src/selinux.rs

@@ -0,0 +1,80 @@
+// Copyright 2022 Sony Group Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+use anyhow::{Context, Result};
+use nix::unistd::gettid;
+use std::fs::{self, OpenOptions};
+use std::io::prelude::*;
+use std::path::Path;
+
+pub fn is_enabled() -> Result<bool> {
+    let buf = fs::read_to_string("/proc/mounts")?;
+    let enabled = buf.contains("selinuxfs");
+
+    Ok(enabled)
+}
+
+pub fn add_mount_label(data: &mut String, label: &str) {
+    if data.is_empty() {
+        let context = format!("context=\"{}\"", label);
+        data.push_str(&context);
+    } else {
+        let context = format!(",context=\"{}\"", label);
+        data.push_str(&context);
+    }
+}
+
+pub fn set_exec_label(label: &str) -> Result<()> {
+    let mut attr_path = Path::new("/proc/thread-self/attr/exec").to_path_buf();
+    if !attr_path.exists() {
+        // Fall back to the old convention
+        attr_path = Path::new("/proc/self/task")
+            .join(gettid().to_string())
+            .join("attr/exec")
+    }
+
+    let mut file = OpenOptions::new()
+        .write(true)
+        .truncate(true)
+        .open(attr_path)?;
+    file.write_all(label.as_bytes())
+        .with_context(|| "failed to apply SELinux label")?;
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const TEST_LABEL: &str = "system_u:system_r:unconfined_t:s0";
+
+    #[test]
+    fn test_is_enabled() {
+        let ret = is_enabled();
+        assert!(ret.is_ok(), "Expecting Ok, Got {:?}", ret);
+    }
+
+    #[test]
+    fn test_add_mount_label() {
+        let mut data = String::new();
+        add_mount_label(&mut data, TEST_LABEL);
+        assert_eq!(data, format!("context=\"{}\"", TEST_LABEL));
+
+        let mut data = String::from("defaults");
+        add_mount_label(&mut data, TEST_LABEL);
+        assert_eq!(data, format!("defaults,context=\"{}\"", TEST_LABEL));
+    }
+
+    #[test]
+    fn test_set_exec_label() {
+        let ret = set_exec_label(TEST_LABEL);
+        if is_enabled().unwrap() {
+            assert!(ret.is_ok(), "Expecting Ok, Got {:?}", ret);
+        } else {
+            assert!(ret.is_err(), "Expecting error, Got {:?}", ret);
+        }
+    }
+}

src/agent/rustjail/src/validator.rs

@@ -6,6 +6,7 @@
 use crate::container::Config;
 use anyhow::{anyhow, Context, Result};
 use oci::{Linux, LinuxIdMapping, LinuxNamespace, Spec};
+use regex::Regex;
 use std::collections::HashMap;
 use std::path::{Component, PathBuf};
 
@@ -86,6 +87,23 @@ fn hostname(oci: &Spec) -> Result<()> {
 
 fn security(oci: &Spec) -> Result<()> {
     let linux = get_linux(oci)?;
+    let label_pattern = r".*_u:.*_r:.*_t:s[0-9]|1[0-5].*";
+    let label_regex = Regex::new(label_pattern)?;
+
+    if let Some(ref process) = oci.process {
+        if !process.selinux_label.is_empty() && !label_regex.is_match(&process.selinux_label) {
+            return Err(anyhow!(
+                "SELinux label for the process is invalid format: {}",
+                &process.selinux_label
+            ));
+        }
+    }
+    if !linux.mount_label.is_empty() && !label_regex.is_match(&linux.mount_label) {
+        return Err(anyhow!(
+            "SELinux label for the mount is invalid format: {}",
+            &linux.mount_label
+        ));
+    }
 
     if linux.masked_paths.is_empty() && linux.readonly_paths.is_empty() {
         return Ok(());
@@ -95,8 +113,6 @@ fn security(oci: &Spec) -> Result<()> {
         return Err(anyhow!("Linux namespace does not contain mount"));
     }
 
-    // don't care about selinux at present
-
     Ok(())
 }
 
@@ -285,7 +301,7 @@ pub fn validate(conf: &Config) -> Result<()> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use oci::Mount;
+    use oci::{Mount, Process};
 
     #[test]
     fn test_namespace() {
@@ -388,6 +404,29 @@ mod tests {
         ];
         spec.linux = Some(linux);
         security(&spec).unwrap();
+
+        // SELinux
+        let valid_label = "system_u:system_r:container_t:s0:c123,c456";
+        let mut process = Process::default();
+        process.selinux_label = valid_label.to_string();
+        spec.process = Some(process);
+        security(&spec).unwrap();
+
+        let mut linux = Linux::default();
+        linux.mount_label = valid_label.to_string();
+        spec.linux = Some(linux);
+        security(&spec).unwrap();
+
+        let invalid_label = "system_u:system_r:container_t";
+        let mut process = Process::default();
+        process.selinux_label = invalid_label.to_string();
+        spec.process = Some(process);
+        security(&spec).unwrap_err();
+
+        let mut linux = Linux::default();
+        linux.mount_label = invalid_label.to_string();
+        spec.linux = Some(linux);
+        security(&spec).unwrap_err();
     }
 
     #[test]

src/runtime/Makefile

@@ -171,6 +171,11 @@ DEFDISABLEGUESTEMPTYDIR := false
 DEFAULTEXPFEATURES := []
 
 DEFDISABLESELINUX := false
+
+# Default guest SELinux configuration
+DEFDISABLEGUESTSELINUX := true
+DEFGUESTSELINUXLABEL := system_u:system_r:container_t
+
 #Default SeccomSandbox param
 #The same default policy is used by libvirt
 #More explanation on https://lists.gnu.org/archive/html/qemu-devel/2017-02/msg03348.html
@@ -460,6 +465,8 @@ USER_VARS += DEFNETWORKMODEL_QEMU
 USER_VARS += DEFDISABLEGUESTEMPTYDIR
 USER_VARS += DEFDISABLEGUESTSECCOMP
 USER_VARS += DEFDISABLESELINUX
+USER_VARS += DEFDISABLEGUESTSELINUX
+USER_VARS += DEFGUESTSELINUXLABEL
 USER_VARS += DEFAULTEXPFEATURES
 USER_VARS += DEFDISABLEBLOCK
 USER_VARS += DEFBLOCKSTORAGEDRIVER_ACRN

src/runtime/cmd/kata-runtime/kata-env.go

@@ -76,6 +76,7 @@ type RuntimeConfigInfo struct {
 type RuntimeInfo struct {
 	Config              RuntimeConfigInfo
 	Path                string
+	GuestSeLinuxLabel   string
 	Experimental        []exp.Feature
 	Version             RuntimeVersionInfo
 	Debug               bool
@@ -186,6 +187,7 @@ func getRuntimeInfo(configFile string, config oci.RuntimeConfig) RuntimeInfo {
 		SandboxCgroupOnly:   config.SandboxCgroupOnly,
 		Experimental:        config.Experimental,
 		DisableGuestSeccomp: config.DisableGuestSeccomp,
+		GuestSeLinuxLabel:   config.GuestSeLinuxLabel,
 	}
 }
 

src/runtime/config/configuration-clh.toml.in

@@ -38,6 +38,13 @@ image = "@IMAGEPATH@"
 # disable applying SELinux on the VMM process (default false)
 disable_selinux=@DEFDISABLESELINUX@
 
+# disable applying SELinux on the container process
+# If set to false, the type `container_t` is applied to the container process by default.
+# Note: To enable guest SELinux, the guest rootfs must be CentOS that is created and built
+# with `SELINUX=yes`.
+# (default: true)
+disable_guest_selinux=@DEFDISABLEGUESTSELINUX@
+
 # Path to the firmware.
 # If you want Cloud Hypervisor to use a specific firmware, set its path below.
 # This is option is only used when confidential_guest is enabled.
@@ -321,6 +328,14 @@ internetworking_model="@DEFNETWORKMODEL_CLH@"
 # (default: true)
 disable_guest_seccomp=@DEFDISABLEGUESTSECCOMP@
 
+# Apply a custom SELinux security policy to the container process inside the VM.
+# This is used when you want to apply a type other than the default `container_t`,
+# so general users should not uncomment and apply it.
+# (format: "user:role:type")
+# Note: You cannot specify MCS policy with the label because the sensitivity levels and
+# categories are determined automatically by high-level container runtimes such as containerd.
+#guest_selinux_label="@DEFGUESTSELINUXLABEL@"
+
 # If enabled, the runtime will create opentracing.io traces and spans.
 # (See https://www.jaegertracing.io/docs/getting-started).
 # (default: disabled)

src/runtime/config/configuration-qemu.toml.in

@@ -438,6 +438,14 @@ valid_entropy_sources = @DEFVALIDENTROPYSOURCES@
 # disable applying SELinux on the VMM process (default false)
 disable_selinux=@DEFDISABLESELINUX@
 
+# disable applying SELinux on the container process
+# If set to false, the type `container_t` is applied to the container process by default.
+# Note: To enable guest SELinux, the guest rootfs must be CentOS that is created and built
+# with `SELINUX=yes`.
+# (default: true)
+disable_guest_selinux=@DEFDISABLEGUESTSELINUX@
+
+
 [factory]
 # VM templating support. Once enabled, new VMs are created from template
 # using vm cloning. They will share the same initial kernel, initramfs and
@@ -555,6 +563,14 @@ internetworking_model="@DEFNETWORKMODEL_QEMU@"
 # (default: true)
 disable_guest_seccomp=@DEFDISABLEGUESTSECCOMP@
 
+# Apply a custom SELinux security policy to the container process inside the VM.
+# This is used when you want to apply a type other than the default `container_t`,
+# so general users should not uncomment and apply it.
+# (format: "user:role:type")
+# Note: You cannot specify MCS policy with the label because the sensitivity levels and
+# categories are determined automatically by high-level container runtimes such as containerd.
+#guest_selinux_label="@DEFGUESTSELINUXLABEL@"
+
 # If enabled, the runtime will create opentracing.io traces and spans.
 # (See https://www.jaegertracing.io/docs/getting-started).
 # (default: disabled)

src/runtime/pkg/katautils/config-settings.go.in

@@ -90,6 +90,7 @@ const defaultSevSnpGuest = false
 const defaultGuestSwap = false
 const defaultRootlessHypervisor = false
 const defaultDisableSeccomp = false
+const defaultDisableGuestSeLinux = true
 const defaultVfioMode = "guest-kernel"
 const defaultLegacySerial = false
 

src/runtime/pkg/katautils/config.go

@@ -59,9 +59,9 @@ const (
 type tomlConfig struct {
 	Hypervisor map[string]hypervisor
 	Agent      map[string]agent
-	Runtime    runtime
 	Image      image
 	Factory    factory
+	Runtime    runtime
 }
 
 type image struct {
@@ -154,6 +154,7 @@ type hypervisor struct {
 	Rootless                       bool     `toml:"rootless"`
 	DisableSeccomp                 bool     `toml:"disable_seccomp"`
 	DisableSeLinux                 bool     `toml:"disable_selinux"`
+	DisableGuestSeLinux            bool     `toml:"disable_guest_selinux"`
 	LegacySerial                   bool     `toml:"use_legacy_serial"`
 	EnableVCPUsPinning             bool     `toml:"enable_vcpus_pinning"`
 }
@@ -164,12 +165,13 @@ type runtime struct {
 	JaegerUser                string   `toml:"jaeger_user"`
 	JaegerPassword            string   `toml:"jaeger_password"`
 	VfioMode                  string   `toml:"vfio_mode"`
+	GuestSeLinuxLabel         string   `toml:"guest_selinux_label"`
 	SandboxBindMounts         []string `toml:"sandbox_bind_mounts"`
 	Experimental              []string `toml:"experimental"`
-	Debug                     bool     `toml:"enable_debug"`
 	Tracing                   bool     `toml:"enable_tracing"`
 	DisableNewNetNs           bool     `toml:"disable_new_netns"`
 	DisableGuestSeccomp       bool     `toml:"disable_guest_seccomp"`
+	Debug                     bool     `toml:"enable_debug"`
 	SandboxCgroupOnly         bool     `toml:"sandbox_cgroup_only"`
 	StaticSandboxResourceMgmt bool     `toml:"static_sandbox_resource_mgmt"`
 	EnablePprof               bool     `toml:"enable_pprof"`
@@ -690,6 +692,7 @@ func newFirecrackerHypervisorConfig(h hypervisor) (vc.HypervisorConfig, error) {
 		TxRateLimiterMaxRate:  txRateLimiterMaxRate,
 		EnableAnnotations:     h.EnableAnnotations,
 		DisableSeLinux:        h.DisableSeLinux,
+		DisableGuestSeLinux:   true, // Guest SELinux is not supported in Firecracker
 	}, nil
 }
 
@@ -836,6 +839,7 @@ func newQemuHypervisorConfig(h hypervisor) (vc.HypervisorConfig, error) {
 		LegacySerial:            h.LegacySerial,
 		DisableSeLinux:          h.DisableSeLinux,
 		EnableVCPUsPinning:      h.EnableVCPUsPinning,
+		DisableGuestSeLinux:     h.DisableGuestSeLinux,
 	}, nil
 }
 
@@ -902,6 +906,7 @@ func newAcrnHypervisorConfig(h hypervisor) (vc.HypervisorConfig, error) {
 		GuestHookPath:         h.guestHookPath(),
 		DisableSeLinux:        h.DisableSeLinux,
 		EnableAnnotations:     h.EnableAnnotations,
+		DisableGuestSeLinux:   true, // Guest SELinux is not supported in ACRN
 	}, nil
 }
 
@@ -1007,6 +1012,7 @@ func newClhHypervisorConfig(h hypervisor) (vc.HypervisorConfig, error) {
 		DisableSeccomp:                 h.DisableSeccomp,
 		ConfidentialGuest:              h.ConfidentialGuest,
 		DisableSeLinux:                 h.DisableSeLinux,
+		DisableGuestSeLinux:            h.DisableGuestSeLinux,
 		NetRateLimiterBwMaxRate:        h.getNetRateLimiterBwMaxRate(),
 		NetRateLimiterBwOneTimeBurst:   h.getNetRateLimiterBwOneTimeBurst(),
 		NetRateLimiterOpsMaxRate:       h.getNetRateLimiterOpsMaxRate(),
@@ -1230,6 +1236,7 @@ func GetDefaultHypervisorConfig() vc.HypervisorConfig {
 		GuestSwap:               defaultGuestSwap,
 		Rootless:                defaultRootlessHypervisor,
 		DisableSeccomp:          defaultDisableSeccomp,
+		DisableGuestSeLinux:     defaultDisableGuestSeLinux,
 		LegacySerial:            defaultLegacySerial,
 	}
 }
@@ -1317,7 +1324,7 @@ func LoadConfiguration(configPath string, ignoreLogging bool) (resolvedConfigPat
 	}
 
 	config.DisableGuestSeccomp = tomlConf.Runtime.DisableGuestSeccomp
-
+	config.GuestSeLinuxLabel = tomlConf.Runtime.GuestSeLinuxLabel
 	config.StaticSandboxResourceMgmt = tomlConf.Runtime.StaticSandboxResourceMgmt
 	config.SandboxCgroupOnly = tomlConf.Runtime.SandboxCgroupOnly
 	config.DisableNewNetNs = tomlConf.Runtime.DisableNewNetNs

src/runtime/pkg/katautils/config_test.go

@@ -554,6 +554,7 @@ func TestMinimalRuntimeConfig(t *testing.T) {
 		VhostUserStorePath:    defaultVhostUserStorePath,
 		VirtioFSCache:         defaultVirtioFSCacheMode,
 		BlockDeviceAIO:        defaultBlockDeviceAIO,
+		DisableGuestSeLinux:   defaultDisableGuestSeLinux,
 	}
 
 	expectedAgentConfig := vc.KataAgentConfig{

src/runtime/pkg/oci/utils.go

@@ -128,6 +128,9 @@ type RuntimeConfig struct {
 	//Determines if seccomp should be applied inside guest
 	DisableGuestSeccomp bool
 
+	//SELinux security context applied to the container process inside guest.
+	GuestSeLinuxLabel string
+
 	// Sandbox sizing information which, if provided, indicates the size of
 	// the sandbox needed for the workload(s)
 	SandboxCPUs  uint32
@@ -945,6 +948,8 @@ func SandboxConfig(ocispec specs.Spec, runtime RuntimeConfig, bundlePath, cid st
 
 		DisableGuestSeccomp: runtime.DisableGuestSeccomp,
 
+		GuestSeLinuxLabel: runtime.GuestSeLinuxLabel,
+
 		Experimental: runtime.Experimental,
 	}
 

src/runtime/virtcontainers/hypervisor.go

@@ -74,6 +74,8 @@ const (
 	MinHypervisorMemory = 256
 
 	defaultMsize9p = 8192
+
+	defaultDisableGuestSeLinux = true
 )
 
 var (
@@ -560,6 +562,9 @@ type HypervisorConfig struct {
 	// Disable selinux from the hypervisor process
 	DisableSeLinux bool
 
+	// Disable selinux from the container process
+	DisableGuestSeLinux bool
+
 	// Use legacy serial for the guest console
 	LegacySerial bool
 

src/runtime/virtcontainers/hypervisor_config_linux_test.go

@@ -92,22 +92,24 @@ func TestHypervisorConfigValidTemplateConfig(t *testing.T) {
 func TestHypervisorConfigDefaults(t *testing.T) {
 	assert := assert.New(t)
 	hypervisorConfig := &HypervisorConfig{
-		KernelPath:     fmt.Sprintf("%s/%s", testDir, testKernel),
-		ImagePath:      fmt.Sprintf("%s/%s", testDir, testImage),
-		HypervisorPath: "",
+		KernelPath:          fmt.Sprintf("%s/%s", testDir, testKernel),
+		ImagePath:           fmt.Sprintf("%s/%s", testDir, testImage),
+		HypervisorPath:      "",
+		DisableGuestSeLinux: defaultDisableGuestSeLinux,
 	}
 	testHypervisorConfigValid(t, hypervisorConfig, true)
 
 	hypervisorConfigDefaultsExpected := &HypervisorConfig{
-		KernelPath:        fmt.Sprintf("%s/%s", testDir, testKernel),
-		ImagePath:         fmt.Sprintf("%s/%s", testDir, testImage),
-		HypervisorPath:    "",
-		NumVCPUs:          defaultVCPUs,
-		MemorySize:        defaultMemSzMiB,
-		DefaultBridges:    defaultBridges,
-		BlockDeviceDriver: defaultBlockDriver,
-		DefaultMaxVCPUs:   defaultMaxVCPUs,
-		Msize9p:           defaultMsize9p,
+		KernelPath:          fmt.Sprintf("%s/%s", testDir, testKernel),
+		ImagePath:           fmt.Sprintf("%s/%s", testDir, testImage),
+		HypervisorPath:      "",
+		NumVCPUs:            defaultVCPUs,
+		MemorySize:          defaultMemSzMiB,
+		DefaultBridges:      defaultBridges,
+		BlockDeviceDriver:   defaultBlockDriver,
+		DefaultMaxVCPUs:     defaultMaxVCPUs,
+		Msize9p:             defaultMsize9p,
+		DisableGuestSeLinux: defaultDisableGuestSeLinux,
 	}
 
 	assert.Exactly(hypervisorConfig, hypervisorConfigDefaultsExpected)

src/runtime/virtcontainers/kata_agent.go

@@ -36,6 +36,7 @@ import (
 	"context"
 	"github.com/gogo/protobuf/proto"
 	"github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/opencontainers/selinux/go-selinux"
 	"github.com/sirupsen/logrus"
 	"golang.org/x/sys/unix"
 	"google.golang.org/grpc/codes"
@@ -69,6 +70,9 @@ const (
 	kernelParamDebugConsole           = "agent.debug_console"
 	kernelParamDebugConsoleVPort      = "agent.debug_console_vport"
 	kernelParamDebugConsoleVPortValue = "1026"
+
+	// Default SELinux type applied to the container process inside guest
+	defaultSeLinuxContainerType = "container_t"
 )
 
 var (
@@ -895,7 +899,7 @@ func (k *kataAgent) removeIgnoredOCIMount(spec *specs.Spec, ignoredMounts map[st
 	return nil
 }
 
-func (k *kataAgent) constrainGRPCSpec(grpcSpec *grpc.Spec, passSeccomp bool, stripVfio bool) {
+func (k *kataAgent) constrainGRPCSpec(grpcSpec *grpc.Spec, passSeccomp bool, disableGuestSeLinux bool, guestSeLinuxLabel string, stripVfio bool) error {
 	// Disable Hooks since they have been handled on the host and there is
 	// no reason to send them to the agent. It would make no sense to try
 	// to apply them on the guest.
@@ -907,11 +911,34 @@ func (k *kataAgent) constrainGRPCSpec(grpcSpec *grpc.Spec, passSeccomp bool, str
 		grpcSpec.Linux.Seccomp = nil
 	}
 
-	// Disable SELinux inside of the virtual machine, the label will apply
-	// to the KVM process
+	// Pass SELinux label for the container process to the agent.
 	if grpcSpec.Process.SelinuxLabel != "" {
-		k.Logger().Info("SELinux label from config will be applied to the hypervisor process, not the VM workload")
-		grpcSpec.Process.SelinuxLabel = ""
+		if !disableGuestSeLinux {
+			k.Logger().Info("SELinux label will be applied to the container process inside guest")
+
+			var label string
+			if guestSeLinuxLabel != "" {
+				label = guestSeLinuxLabel
+			} else {
+				label = grpcSpec.Process.SelinuxLabel
+			}
+
+			processContext, err := selinux.NewContext(label)
+			if err != nil {
+				return err
+			}
+
+			// Change the type from KVM to container because the type passed from the high-level
+			// runtime is for KVM process.
+			if guestSeLinuxLabel == "" {
+				processContext["type"] = defaultSeLinuxContainerType
+			}
+			grpcSpec.Process.SelinuxLabel = processContext.Get()
+		} else {
+			k.Logger().Info("Empty SELinux label for the process and the mount because guest SELinux is disabled")
+			grpcSpec.Process.SelinuxLabel = ""
+			grpcSpec.Linux.MountLabel = ""
+		}
 	}
 
 	// By now only CPU constraints are supported
@@ -973,6 +1000,8 @@ func (k *kataAgent) constrainGRPCSpec(grpcSpec *grpc.Spec, passSeccomp bool, str
 		}
 		grpcSpec.Linux.Devices = linuxDevices
 	}
+
+	return nil
 }
 
 func (k *kataAgent) handleShm(mounts []specs.Mount, sandbox *Sandbox) {
@@ -1256,9 +1285,20 @@ func (k *kataAgent) createContainer(ctx context.Context, sandbox *Sandbox, c *Co
 
 	passSeccomp := !sandbox.config.DisableGuestSeccomp && sandbox.seccompSupported
 
+	// Currently, guest SELinux can be enabled only when SELinux is enabled on the host side.
+	if !sandbox.config.HypervisorConfig.DisableGuestSeLinux && !selinux.GetEnabled() {
+		return nil, fmt.Errorf("Guest SELinux is enabled, but SELinux is disabled on the host side")
+	}
+	if sandbox.config.HypervisorConfig.DisableGuestSeLinux && sandbox.config.GuestSeLinuxLabel != "" {
+		return nil, fmt.Errorf("Custom SELinux security policy is provided, but guest SELinux is disabled")
+	}
+
 	// We need to constrain the spec to make sure we're not
 	// passing irrelevant information to the agent.
-	k.constrainGRPCSpec(grpcSpec, passSeccomp, sandbox.config.VfioMode == config.VFIOModeGuestKernel)
+	err = k.constrainGRPCSpec(grpcSpec, passSeccomp, sandbox.config.HypervisorConfig.DisableGuestSeLinux, sandbox.config.GuestSeLinuxLabel, sandbox.config.VfioMode == config.VFIOModeGuestKernel)
+	if err != nil {
+		return nil, err
+	}
 
 	req := &grpc.CreateContainerRequest{
 		ContainerId:  c.id,

src/runtime/virtcontainers/kata_agent_test.go

@@ -619,7 +619,7 @@ func TestConstrainGRPCSpec(t *testing.T) {
 	}
 
 	k := kataAgent{}
-	k.constrainGRPCSpec(g, true, true)
+	k.constrainGRPCSpec(g, true, true, "", true)
 
 	// Check nil fields
 	assert.Nil(g.Hooks)

src/runtime/virtcontainers/persist.go

@@ -189,6 +189,7 @@ func (s *Sandbox) dumpConfig(ss *persistapi.SandboxState) {
 		SystemdCgroup:       sconfig.SystemdCgroup,
 		SandboxCgroupOnly:   sconfig.SandboxCgroupOnly,
 		DisableGuestSeccomp: sconfig.DisableGuestSeccomp,
+		GuestSeLinuxLabel:   sconfig.GuestSeLinuxLabel,
 	}
 
 	ss.Config.SandboxBindMounts = append(ss.Config.SandboxBindMounts, sconfig.SandboxBindMounts...)
@@ -429,6 +430,7 @@ func loadSandboxConfig(id string) (*SandboxConfig, error) {
 		SystemdCgroup:       savedConf.SystemdCgroup,
 		SandboxCgroupOnly:   savedConf.SandboxCgroupOnly,
 		DisableGuestSeccomp: savedConf.DisableGuestSeccomp,
+		GuestSeLinuxLabel:   savedConf.GuestSeLinuxLabel,
 	}
 	sconfig.SandboxBindMounts = append(sconfig.SandboxBindMounts, savedConf.SandboxBindMounts...)
 

src/runtime/virtcontainers/persist/api/config.go

@@ -243,19 +243,6 @@ type ContainerConfig struct {
 // SandboxConfig is a sandbox configuration.
 // Refs: virtcontainers/sandbox.go:SandboxConfig
 type SandboxConfig struct {
-	// Information for fields not saved:
-	// * Annotation: this is kind of casual data, we don't need casual data in persist file,
-	// 				if you know this data needs to persist, please gives it
-	//				a specific field
-
-	ContainerConfigs []ContainerConfig
-
-	// SandboxBindMounts - list of paths to mount into guest
-	SandboxBindMounts []string
-
-	// Experimental enables experimental features
-	Experimental []string
-
 	// Cgroups specifies specific cgroup settings for the various subsystems that the container is
 	// placed into to limit the resources the container has available
 	Cgroups *configs.Cgroup `json:"cgroups"`
@@ -265,8 +252,24 @@ type SandboxConfig struct {
 
 	KataShimConfig *ShimConfig
 
-	HypervisorType   string
-	NetworkConfig    NetworkConfig
+	// Custom SELinux security policy to the container process inside the VM
+	GuestSeLinuxLabel string
+
+	HypervisorType string
+
+	// SandboxBindMounts - list of paths to mount into guest
+	SandboxBindMounts []string
+
+	// Experimental enables experimental features
+	Experimental []string
+
+	// Information for fields not saved:
+	// * Annotation: this is kind of casual data, we don't need casual data in persist file,
+	// if you know this data needs to persist, please gives it a specific field
+	ContainerConfigs []ContainerConfig
+
+	NetworkConfig NetworkConfig
+
 	HypervisorConfig HypervisorConfig
 
 	ShmSize uint64

src/runtime/virtcontainers/pkg/annotations/annotations.go

@@ -247,6 +247,9 @@ const (
 	// DisableGuestSeccomp is a sandbox annotation that determines if seccomp should be applied inside guest.
 	DisableGuestSeccomp = kataAnnotRuntimePrefix + "disable_guest_seccomp"
 
+	// GuestSeLinuxLabel is a SELinux security policy that is applied to a container process inside guest.
+	GuestSeLinuxLabel = kataAnnotRuntimePrefix + "guest_selinux_label"
+
 	// SandboxCgroupOnly is a sandbox annotation that determines if kata processes are managed only in sandbox cgroup.
 	SandboxCgroupOnly = kataAnnotRuntimePrefix + "sandbox_cgroup_only"
 

src/runtime/virtcontainers/qemu.go

@@ -181,6 +181,15 @@ func (q *qemu) kernelParameters() string {
 	// set the maximum number of vCPUs
 	params = append(params, Param{"nr_cpus", fmt.Sprintf("%d", q.config.DefaultMaxVCPUs)})
 
+	// set the SELinux params in accordance with the runtime configuration, disable_guest_selinux.
+	if q.config.DisableGuestSeLinux {
+		q.Logger().Info("Set selinux=0 to kernel params because SELinux on the guest is disabled")
+		params = append(params, Param{"selinux", "0"})
+	} else {
+		q.Logger().Info("Set selinux=1 to kernel params because SELinux on the guest is enabled")
+		params = append(params, Param{"selinux", "1"})
+	}
+
 	// add the params specified by the provided config. As the kernel
 	// honours the last parameter value set and since the config-provided
 	// params are added here, they will take priority over the defaults.
@@ -476,6 +485,13 @@ func (q *qemu) createVirtiofsDaemon(sharedPath string) (VirtiofsDaemon, error) {
 		return nd, nil
 	}
 
+	// Set the xattr option for virtiofsd daemon to enable extended attributes
+	// in virtiofs if SELinux on the guest side is enabled.
+	if !q.config.DisableGuestSeLinux {
+		q.Logger().Info("Set the xattr option for virtiofsd")
+		q.config.VirtioFSExtraArgs = append(q.config.VirtioFSExtraArgs, "-o", "xattr")
+	}
+
 	// default use virtiofsd
 	return &virtiofsd{
 		path:       q.config.VirtioFSDaemon,
@@ -846,7 +862,6 @@ func (q *qemu) StartVM(ctx context.Context, timeout int) error {
 	// the SELinux label. If these processes require privileged, we do
 	// notwant to run them under confinement.
 	if !q.config.DisableSeLinux {
-
 		if err := label.SetProcessLabel(q.config.SELinuxProcessLabel); err != nil {
 			return err
 		}

src/runtime/virtcontainers/qemu_test.go

@@ -27,15 +27,16 @@ import (
 
 func newQemuConfig() HypervisorConfig {
 	return HypervisorConfig{
-		KernelPath:        testQemuKernelPath,
-		InitrdPath:        testQemuInitrdPath,
-		HypervisorPath:    testQemuPath,
-		NumVCPUs:          defaultVCPUs,
-		MemorySize:        defaultMemSzMiB,
-		DefaultBridges:    defaultBridges,
-		BlockDeviceDriver: defaultBlockDriver,
-		DefaultMaxVCPUs:   defaultMaxVCPUs,
-		Msize9p:           defaultMsize9p,
+		KernelPath:          testQemuKernelPath,
+		InitrdPath:          testQemuInitrdPath,
+		HypervisorPath:      testQemuPath,
+		NumVCPUs:            defaultVCPUs,
+		MemorySize:          defaultMemSzMiB,
+		DefaultBridges:      defaultBridges,
+		BlockDeviceDriver:   defaultBlockDriver,
+		DefaultMaxVCPUs:     defaultMaxVCPUs,
+		Msize9p:             defaultMsize9p,
+		DisableGuestSeLinux: defaultDisableGuestSeLinux,
 	}
 }
 
@@ -58,7 +59,7 @@ func testQemuKernelParameters(t *testing.T, kernelParams []Param, expected strin
 }
 
 func TestQemuKernelParameters(t *testing.T) {
-	expectedOut := fmt.Sprintf("panic=1 nr_cpus=%d foo=foo bar=bar", govmm.MaxVCPUs())
+	expectedOut := fmt.Sprintf("panic=1 nr_cpus=%d selinux=0 foo=foo bar=bar", govmm.MaxVCPUs())
 	params := []Param{
 		{
 			Key:   "foo",

src/runtime/virtcontainers/sandbox.go

@@ -126,14 +126,17 @@ type SandboxResourceSizing struct {
 
 // SandboxConfig is a Sandbox configuration.
 type SandboxConfig struct {
-	// Volumes is a list of shared volumes between the host and the Sandbox.
-	Volumes []types.Volume
+	// Annotations keys must be unique strings and must be name-spaced
+	Annotations map[string]string
 
-	// Containers describe the list of containers within a Sandbox.
-	// This list can be empty and populated by adding containers
-	// to the Sandbox a posteriori.
-	//TODO: this should be a map to avoid duplicated containers
-	Containers []ContainerConfig
+	// Custom SELinux security policy to the container process inside the VM
+	GuestSeLinuxLabel string
+
+	HypervisorType HypervisorType
+
+	ID string
+
+	Hostname string
 
 	// SandboxBindMounts - list of paths to mount into guest
 	SandboxBindMounts []string
@@ -141,31 +144,29 @@ type SandboxConfig struct {
 	// Experimental features enabled
 	Experimental []exp.Feature
 
-	// Annotations keys must be unique strings and must be name-spaced
-	// with e.g. reverse domain notation (org.clearlinux.key).
-	Annotations map[string]string
+	// Containers describe the list of containers within a Sandbox.
+	// This list can be empty and populated by adding containers
+	// to the Sandbox a posteriori.
+	// TODO: this should be a map to avoid duplicated containers
+	Containers []ContainerConfig
 
-	ID string
-
-	Hostname string
-
-	HypervisorType HypervisorType
-
-	AgentConfig KataAgentConfig
+	Volumes []types.Volume
 
 	NetworkConfig NetworkConfig
 
+	AgentConfig KataAgentConfig
+
 	HypervisorConfig HypervisorConfig
 
-	SandboxResources SandboxResourceSizing
-
-	// StaticResourceMgmt indicates if the shim should rely on statically sizing the sandbox (VM)
-	StaticResourceMgmt bool
-
 	ShmSize uint64
 
+	SandboxResources SandboxResourceSizing
+
 	VfioMode config.VFIOModeType
 
+	// StaticResourceMgmt indicates if the shim should rely on statically sizing the sandbox (VM)
+	StaticResourceMgmt bool
+
 	// SharePidNs sets all containers to share the same sandbox level pid namespace.
 	SharePidNs bool
 

tools/osbuilder/image-builder/image_builder.sh

@@ -64,6 +64,8 @@ readonly -a systemd_files=(
 
 # Set a default value
 AGENT_INIT=${AGENT_INIT:-no}
+SELINUX=${SELINUX:-no}
+SELINUXFS="/sys/fs/selinux"
 
 # Align image to 128M
 readonly mem_boundary_mb=128
@@ -93,6 +95,10 @@ Extra environment variables:
 	                DEFAULT: not set
 	USE_PODMAN:     If set and USE_DOCKER not set, will build image in a Podman Container (requries podman)
 	                DEFAULT: not set
+	SELINUX:        If set to "yes", the rootfs is labeled for SELinux.
+	                Make sure that selinuxfs is mounted to /sys/fs/selinux on the host
+	                and the rootfs is built with SELINUX=yes.
+	                DEFAULT value: "no"
 
 
 Following diagram shows how the resulting image will look like
@@ -134,6 +140,7 @@ build_with_container() {
 	local nsdax_bin="$9"
 	local container_image_name="image-builder-osbuilder"
 	local shared_files=""
+	local selinuxfs=""
 
 	image_dir=$(readlink -f "$(dirname "${image}")")
 	image_name=$(basename "${image}")
@@ -157,6 +164,14 @@ build_with_container() {
 		shared_files+="-v ${mke2fs_conf}:${mke2fs_conf}:ro "
 	fi
 
+	if [ "${SELINUX}" == "yes" ]; then
+		if mountpoint $SELINUXFS > /dev/null; then
+			selinuxfs="-v ${SELINUXFS}:${SELINUXFS}"
+		else
+			die "Make sure that SELinux is enabled on the host"
+		fi
+	fi
+
 	#Make sure we use a compatible runtime to build rootfs
 	# In case Clear Containers Runtime is installed we dont want to hit issue:
 	#https://github.com/clearcontainers/runtime/issues/828
@@ -170,12 +185,14 @@ build_with_container() {
 		   --env BLOCK_SIZE="${block_size}" \
 		   --env ROOT_FREE_SPACE="${root_free_space}" \
 		   --env NSDAX_BIN="${nsdax_bin}" \
+		   --env SELINUX="${SELINUX}" \
 		   --env DEBUG="${DEBUG}" \
 		   -v /dev:/dev \
 		   -v "${script_dir}":"/osbuilder" \
 		   -v "${script_dir}/../scripts":"/scripts" \
 		   -v "${rootfs}":"/rootfs" \
 		   -v "${image_dir}":"/image" \
+		   ${selinuxfs} \
 		   ${shared_files} \
 		   ${container_image_name} \
 		   bash "/osbuilder/${script_name}" -o "/image/${image_name}" /rootfs
@@ -384,6 +401,7 @@ create_rootfs_image() {
 	local img_size="$3"
 	local fs_type="$4"
 	local block_size="$5"
+	local agent_bin="$6"
 
 	create_disk "${image}" "${img_size}" "${fs_type}" "${rootfs_start}"
 
@@ -402,6 +420,31 @@ create_rootfs_image() {
 
 	info "Copying content from rootfs to root partition"
 	cp -a "${rootfs}"/* "${mount_dir}"
+
+	if [ "${SELINUX}" == "yes" ]; then
+		if [ "${AGENT_INIT}" == "yes" ]; then
+			die "Guest SELinux with the agent init is not supported yet"
+		fi
+
+		info "Labeling rootfs for SELinux"
+		selinuxfs_path="${mount_dir}${SELINUXFS}"
+		mkdir -p $selinuxfs_path
+		if mountpoint $SELINUXFS > /dev/null && \
+			chroot "${mount_dir}" command -v restorecon > /dev/null; then
+			mount -t selinuxfs selinuxfs $selinuxfs_path
+			chroot "${mount_dir}" restorecon -RF -e ${SELINUXFS} /
+			# TODO: This operation will be removed after the updated container-selinux that
+			# includes the following commit is released.
+			# https://github.com/containers/container-selinux/commit/39f83cc74d50bd10ab6be4d0bdd98bc04857469f
+			# We use chcon as an interim solution until then.
+			chroot "${mount_dir}" chcon -t container_runtime_exec_t "/usr/bin/${agent_bin}"
+			umount $selinuxfs_path
+		else
+			die "Could not label the rootfs. Make sure that SELinux is enabled on the host \
+and the rootfs is built with SELINUX=yes"
+		fi
+	fi
+
 	sync
 	OK "rootfs copied"
 
@@ -529,7 +572,7 @@ main() {
 	# consider in calculate_img_size
 	rootfs_img_size=$((img_size - dax_header_sz))
 	create_rootfs_image "${rootfs}" "${image}" "${rootfs_img_size}" \
-						"${fs_type}" "${block_size}"
+						"${fs_type}" "${block_size}" "${agent_bin}"
 
 	# insert at the beginning of the image the MBR + DAX header
 	set_dax_header "${image}" "${img_size}" "${fs_type}" "${nsdax_bin}"

tools/osbuilder/rootfs-builder/centos/config.sh

@@ -8,10 +8,15 @@ OS_VERSION=${OS_VERSION:-stream9}
 PACKAGES="chrony iptables"
 [ "$AGENT_INIT" = no ] && PACKAGES+=" systemd"
 [ "$SECCOMP" = yes ] && PACKAGES+=" libseccomp"
+[ "$SELINUX" = yes ] && PACKAGES+=" container-selinux"
 
 # Container registry tag is different from metalink repo, e.g. "stream9" => "9-stream"
 os_repo_version="$(sed -E "s/(stream)(.+)/\2-\1/" <<< "$OS_VERSION")"
 
 METALINK="https://mirrors.centos.org/metalink?repo=centos-baseos-$os_repo_version&arch=\$basearch"
+if [ "$SELINUX" == yes ]; then
+    # AppStream repository is required for the container-selinux package
+    METALINK_APPSTREAM="https://mirrors.centos.org/metalink?repo=centos-appstream-$os_repo_version&arch=\$basearch"
+fi
 GPG_KEY_FILE=RPM-GPG-KEY-CentOS-Official
 GPG_KEY_URL="https://centos.org/keys/$GPG_KEY_FILE"

tools/osbuilder/rootfs-builder/rootfs.sh

@@ -25,6 +25,7 @@ LIBC=${LIBC:-musl}
 # The kata agent enables seccomp feature.
 # However, it is not enforced by default: you need to enable that in the main configuration file.
 SECCOMP=${SECCOMP:-"yes"}
+SELINUX=${SELINUX:-"no"}
 
 lib_file="${script_dir}/../scripts/lib.sh"
 source "$lib_file"
@@ -142,6 +143,11 @@ ROOTFS_DIR          Path to the directory that is populated with the rootfs.
 SECCOMP             When set to "no", the kata-agent is built without seccomp capability.
                     Default value: "yes"
 
+SELINUX             When set to "yes", build the rootfs with the required packages to
+                    enable SELinux in the VM.
+                    Make sure the guest kernel is compiled with SELinux enabled.
+                    Default value: "no"
+
 USE_DOCKER          If set, build the rootfs inside a container (requires
                     Docker).
                     Default value: <not set>
@@ -346,6 +352,15 @@ build_rootfs_distro()
 
 	echo "Required rust version: $RUST_VERSION"
 
+	if [ "${SELINUX}" == "yes" ]; then
+		if [ "${AGENT_INIT}" == "yes" ]; then
+			die "Guest SELinux with the agent init is not supported yet"
+		fi
+		if [ "${distro}" != "centos" ]; then
+			die "The guest rootfs must be CentOS to enable guest SELinux"
+		fi
+	fi
+
 	if [ -z "${USE_DOCKER}" ] && [ -z "${USE_PODMAN}" ]; then
 		info "build directly"
 		build_rootfs ${ROOTFS_DIR}
@@ -426,6 +441,7 @@ build_rootfs_distro()
 			--env OS_VERSION="${OS_VERSION}" \
 			--env INSIDE_CONTAINER=1 \
 			--env SECCOMP="${SECCOMP}" \
+			--env SELINUX="${SELINUX}" \
 			--env DEBUG="${DEBUG}" \
 			--env HOME="/root" \
 			-v "${repo_dir}":"/kata-containers" \

tools/osbuilder/scripts/lib.sh

@@ -79,7 +79,23 @@ gpgcheck=1
 gpgkey=file://${CONFIG_DIR}/${GPG_KEY_FILE}
 EOF
 	fi
-
+	if [ "$SELINUX" == "yes" ]; then
+		cat > "${DNF_CONF}" << EOF
+[appstream]
+name=${OS_NAME}-${OS_VERSION} upstream
+releasever=${OS_VERSION}
+EOF
+		echo "metalink=$METALINK_APPSTREAM" >> "$DNF_CONF"
+		if [ -n "$GPG_KEY_URL" ]; then
+			if [ ! -f "${CONFIG_DIR}/${GPG_KEY_FILE}" ]; then
+				curl -L "${GPG_KEY_URL}" -o "${CONFIG_DIR}/${GPG_KEY_FILE}"
+			fi
+			cat >> "${DNF_CONF}" << EOF
+gpgcheck=1
+gpgkey=file://${CONFIG_DIR}/${GPG_KEY_FILE}
+EOF
+		fi
+	fi
 }
 
 build_rootfs()

tools/packaging/kernel/configs/fragments/common/lsm.conf

@@ -0,0 +1,12 @@
+# SELinux support:
+CONFIG_AUDIT=y
+CONFIG_AUDITSYSCALL=y
+CONFIG_LSM_MMAP_MIN_ADDR=6553
+CONFIG_NETWORK_SECMARK=y
+CONFIG_SECURITY_NETWORK=y
+CONFIG_SECURITY_SELINUX=y
+CONFIG_SECURITY_SELINUX_BOOTPARAM=y
+CONFIG_SECURITY_SELINUX_DEVELOP=y
+CONFIG_SECURITY_SELINUX_CHECKREQPROT_VALUE=0
+CONFIG_SECURITY_SELINUX_SIDTAB_HASH_BITS=9
+CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE=256