Soft reboot: Detect SELinux policy deltas

Add check to prevent soft reboot when SELinux policies differ
between booted and target deployments, since policy is not
reloaded across soft reboots.

Assisted-by: Cursor (Auto)
Signed-off-by: gursewak1997 <[email protected]>

Author: gursewak1997

crates/lib/src/status.rs

@@ -93,7 +93,45 @@ impl From<ImageReference> for OstreeImageReference {
     }
 }
 
+/// Check if SELinux policies are compatible between booted and target deployments.
+/// Returns false if SELinux is enabled and the policies differ or have mismatched presence.
+fn check_selinux_policy_compatible(
+    sysroot: &SysrootLock,
+    booted_deployment: &ostree::Deployment,
+    target_deployment: &ostree::Deployment,
+) -> Result<bool> {
+    // Only check if SELinux is enabled
+    if !crate::lsm::selinux_enabled()? {
+        return Ok(true);
+    }
+
+    let booted_fd = crate::utils::deployment_fd(sysroot, booted_deployment)
+        .context("Failed to get file descriptor for booted deployment")?;
+    let booted_policy = crate::lsm::new_sepolicy_at(&booted_fd)
+        .context("Failed to load SELinux policy from booted deployment")?;
+    let target_fd = crate::utils::deployment_fd(sysroot, target_deployment)
+        .context("Failed to get file descriptor for target deployment")?;
+    let target_policy = crate::lsm::new_sepolicy_at(&target_fd)
+        .context("Failed to load SELinux policy from target deployment")?;
+
+    let booted_csum = booted_policy.and_then(|p| p.csum());
+    let target_csum = target_policy.and_then(|p| p.csum());
+
+    match (booted_csum, target_csum) {
+        (None, None) => Ok(true), // Both absent, compatible
+        (Some(_), None) | (None, Some(_)) => {
+            // Incompatible: one has policy, other doesn't
+            Ok(false)
+        }
+        (Some(booted_csum), Some(target_csum)) => {
+            // Both have policies, checksums must match
+            Ok(booted_csum == target_csum)
+        }
+    }
+}
+
 /// Check if a deployment has soft reboot capability
+// TODO: Lower SELinux policy check into ostree's deployment_can_soft_reboot API
 fn has_soft_reboot_capability(sysroot: &SysrootLock, deployment: &ostree::Deployment) -> bool {
     if !ostree_ext::systemd_has_soft_reboot() {
         return false;
@@ -113,7 +151,22 @@ fn has_soft_reboot_capability(sysroot: &SysrootLock, deployment: &ostree::Deploy
         return false;
     }
 
-    sysroot.deployment_can_soft_reboot(deployment)
+    if !sysroot.deployment_can_soft_reboot(deployment) {
+        return false;
+    }
+
+    // Check SELinux policy compatibility with booted deployment
+    // Block soft reboot if SELinux policies differ, as policy is not reloaded across soft reboots
+    if let Some(booted_deployment) = sysroot.booted_deployment() {
+        // deployment_fd should not fail for valid deployments
+        if !check_selinux_policy_compatible(sysroot, &booted_deployment, deployment)
+            .expect("deployment_fd should not fail for valid deployments")
+        {
+            return false;
+        }
+    }
+
+    true
 }
 
 /// Parse an ostree origin file (a keyfile) and extract the targeted

tmt/plans/integration.fmf

@@ -112,3 +112,14 @@ execute:
     how: fmf
     test:
         - /tmt/tests/test-28-factory-reset
+
+/test-29-soft-reboot-selinux-policy:
+  summary: Test soft reboot with SELinux policy changes
+  discover:
+    how: fmf
+    test:
+        - /tmt/tests/test-29-soft-reboot-selinux-policy
+  adjust:
+    - when: running_env != image_mode
+      enabled: false
+      because: tmt-reboot does not work with systemd reboot in testing farm environment (see bug-soft-reboot.md)

tmt/tests/booted/test-soft-reboot-selinux-policy.nu

@@ -0,0 +1,102 @@
+# Verify that soft reboot is blocked when SELinux policies differ
+use std assert
+use tap.nu
+
+let soft_reboot_capable = "/usr/lib/systemd/system/soft-reboot.target" | path exists
+if not $soft_reboot_capable {
+    echo "Skipping, system is not soft reboot capable"
+    return
+}
+
+# Check if SELinux is enabled
+let selinux_enabled = "/sys/fs/selinux/enforce" | path exists
+if not $selinux_enabled {
+    echo "Skipping, SELinux is not enabled"
+    return
+}
+
+# This code runs on *each* boot.
+bootc status
+
+# Run on the first boot
+def initial_build [] {
+    tap begin "Build base image and test soft reboot with SELinux policy change"
+
+    let td = mktemp -d
+    cd $td
+
+    bootc image copy-to-storage
+
+    # Create a derived container that installs a custom SELinux policy module
+    # Installing a policy module will change the compiled policy checksum
+    # Following Colin's suggestion and the composefs-rs example
+    # We create a minimal policy module and install it
+    "FROM localhost/bootc
+# Install tools needed to build and install SELinux policy modules
+RUN dnf install -y selinux-policy-devel checkpolicy policycoreutils
+
+# Create a minimal SELinux policy module that will change the policy checksum
+# We install it to ensure it's part of the deployment filesystem
+RUN mkdir -p /tmp/bootc-test-policy && \\
+    cd /tmp/bootc-test-policy && \\
+    echo 'module bootc_test_policy 1.0;' > bootc_test_policy.te && \\
+    echo 'require {' >> bootc_test_policy.te && \\
+    echo '    type unconfined_t;' >> bootc_test_policy.te && \\
+    echo '    class file { read write };' >> bootc_test_policy.te && \\
+    echo '}' >> bootc_test_policy.te && \\
+    echo 'type bootc_test_t;' >> bootc_test_policy.te && \\
+    checkmodule -M -m -o bootc_test_policy.mod bootc_test_policy.te && \\
+    semodule_package -o bootc_test_policy.pp -m bootc_test_policy.mod && \\
+    semodule -i bootc_test_policy.pp && \\
+    # Ensure the policy module is in /usr/etc/selinux for the deployment
+    mkdir -p /usr/etc/selinux/targeted/modules/active/modules && \\
+    if [ -d /etc/selinux/targeted/modules/active/modules ]; then \\
+        cp -a /etc/selinux/targeted/modules/active/modules/* /usr/etc/selinux/targeted/modules/active/modules/ 2>/dev/null || true; \\
+    fi && \\
+    rm -rf /tmp/bootc-test-policy
+" | save Dockerfile
+    
+    # Build the derived image
+    podman build --quiet -t localhost/bootc-derived-policy .
+    
+    # Verify soft reboot preparation hasn't happened yet
+    assert (not ("/run/nextroot" | path exists))
+    
+    # Try to soft reboot - this should fail because policies differ
+    bootc switch --soft-reboot=auto --transport containers-storage localhost/bootc-derived-policy
+    let st = bootc status --json | from json
+    
+    # Verify staged deployment exists
+    assert ($st.status.staged != null) "Expected staged deployment to exist"
+    
+    # The staged deployment should NOT be soft-reboot capable because policies differ
+    assert (not $st.status.staged.softRebootCapable) "Expected soft reboot to be blocked due to SELinux policy difference, but softRebootCapable is true"
+    
+    # Verify soft reboot preparation didn't happen
+    assert (not ("/run/nextroot" | path exists)) "Soft reboot should not be prepared when policies differ"
+    
+    # Reset and do a full reboot instead
+    ostree admin prepare-soft-reboot --reset
+    tmt-reboot
+}
+
+# The second boot; verify we're in the derived image
+def second_boot [] {
+    tap begin "Verify deployment with different SELinux policy"
+    
+    # Verify we're in the new deployment
+    let st = bootc status --json | from json
+    let booted = $st.status.booted.image
+    assert ($booted.image.image | str contains "bootc-derived-policy") $"Expected booted image to contain 'bootc-derived-policy', got: ($booted.image.image)"
+    
+    tap ok
+}
+
+def main [] {
+    # See https://tmt.readthedocs.io/en/stable/stories/features.html#reboot-during-test
+    match $env.TMT_REBOOT_COUNT? {
+        null | "0" => initial_build,
+        "1" => second_boot,
+        $o => { error make { msg: $"Invalid TMT_REBOOT_COUNT ($o)" } },
+    }
+}

tmt/tests/test-29-soft-reboot-selinux-policy.fmf

@@ -0,0 +1,3 @@
+summary: Test soft reboot with SELinux policy changes
+test: nu booted/test-soft-reboot-selinux-policy.nu
+duration: 30m