feat(docker,podman): add SELinux label support for bind mounts

The Docker Engine structured Mount API does not support SELinux
relabelling (:z / :Z). Move user-supplied bind mounts from the
structured `mounts` field to the legacy string-format `binds` field,
which does support these options.

Add a shared `SelinuxLabel` enum (shared/private) to openshell-core so
both Docker and Podman drivers accept an optional `selinux_label` field
on bind mount configs. For Docker, labels are appended to the bind
string; for Podman, they are pushed to the mount options vec.

Signed-off-by: Florian Bergmann <fbergman@redhat.com>

Author: bergmannf

crates/openshell-core/src/driver_mounts.rs

@@ -5,6 +5,26 @@
 
 use std::path::Path;
 
+/// `SELinux` relabelling mode for bind mounts.
+///
+/// On hosts with `SELinux` enabled (e.g. Fedora, RHEL) a bind-mounted path
+/// must be relabelled so the container process can access it.
+///
+/// * `shared` (`:z`) — the label is shared across all containers that mount
+///   the same path.  Safe when multiple sandboxes read the same data set.
+/// * `private` (`:Z`) — the label is private to *this* container.  The host
+///   directory becomes inaccessible to other containers (and potentially to
+///   the host) until the container is removed.  Use only when exclusive
+///   ownership is acceptable.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum SelinuxLabel {
+    /// Shared `SELinux` label (`:z`).
+    Shared,
+    /// Private `SELinux` label (`:Z`).
+    Private,
+}
+
 const RESERVED_MOUNT_TARGETS: &[&str] = &[
     "/opt/openshell",
     "/etc/openshell",

crates/openshell-driver-docker/src/lib.rs

@@ -303,6 +303,8 @@ impl DockerSandboxDriverConfig {
     }
 }
 
+use openshell_core::driver_mounts::SelinuxLabel;
+
 #[derive(Debug, Clone, serde::Deserialize)]
 #[serde(tag = "type", rename_all = "snake_case", deny_unknown_fields)]
 enum DockerDriverMountConfig {
@@ -311,6 +313,8 @@ enum DockerDriverMountConfig {
         target: String,
         #[serde(default = "default_true")]
         read_only: bool,
+        #[serde(default)]
+        selinux_label: Option<SelinuxLabel>,
     },
     Volume {
         source: String,
@@ -1761,23 +1765,76 @@ fn docker_driver_config(
     Ok(config)
 }
 
+/// Collect user-supplied bind mounts as string-format binds.
+///
+/// Bind mounts use the legacy `Binds` field (`-v` syntax) rather than the
+/// structured `Mount` API because the Docker Engine Mount object does not
+/// support `SELinux` relabelling (`:z` / `:Z`).  The string format does.
+fn docker_driver_bind_strings(config: &DockerSandboxDriverConfig) -> Result<Vec<String>, Status> {
+    config
+        .mounts
+        .iter()
+        .filter_map(|m| match m {
+            DockerDriverMountConfig::Bind {
+                source,
+                target,
+                read_only,
+                selinux_label,
+            } => Some(docker_bind_string(
+                source,
+                target,
+                *read_only,
+                *selinux_label,
+            )),
+            _ => None,
+        })
+        .collect()
+}
+
+fn docker_bind_string(
+    source: &str,
+    target: &str,
+    read_only: bool,
+    selinux_label: Option<SelinuxLabel>,
+) -> Result<String, Status> {
+    driver_mounts::validate_absolute_mount_source(source, "bind source")
+        .map_err(Status::failed_precondition)?;
+    driver_mounts::validate_container_mount_target(target).map_err(Status::failed_precondition)?;
+    let normalized_target = driver_mounts::normalize_mount_target(target);
+
+    let mut opts = Vec::new();
+    if read_only {
+        opts.push("ro");
+    }
+    match selinux_label {
+        Some(SelinuxLabel::Shared) => opts.push("z"),
+        Some(SelinuxLabel::Private) => opts.push("Z"),
+        None => {}
+    }
+
+    if opts.is_empty() {
+        Ok(format!("{source}:{normalized_target}"))
+    } else {
+        Ok(format!("{source}:{normalized_target}:{}", opts.join(",")))
+    }
+}
+
+/// Collect user-supplied non-bind mounts as structured `Mount` objects.
 fn docker_driver_mounts(config: &DockerSandboxDriverConfig) -> Result<Vec<Mount>, Status> {
-    config.mounts.iter().map(docker_mount_from_config).collect()
+    config
+        .mounts
+        .iter()
+        .filter(|m| !matches!(m, DockerDriverMountConfig::Bind { .. }))
+        .map(docker_mount_from_config)
+        .collect()
 }
 
 fn docker_mount_from_config(config: &DockerDriverMountConfig) -> Result<Mount, Status> {
     match config {
-        DockerDriverMountConfig::Bind {
-            source,
-            target,
-            read_only,
-        } => Ok(Mount {
-            typ: Some(MountTypeEnum::BIND),
-            source: Some(source.clone()),
-            target: Some(target.clone()),
-            read_only: Some(*read_only),
-            ..Default::default()
-        }),
+        DockerDriverMountConfig::Bind { .. } => {
+            // Bind mounts are handled via docker_driver_bind_strings.
+            unreachable!("bind mounts are filtered out before reaching docker_mount_from_config")
+        }
         DockerDriverMountConfig::Volume {
             source,
             target,
@@ -2261,6 +2318,7 @@ fn build_container_create_body_with_gpu_devices(
         .ok_or_else(|| Status::invalid_argument("sandbox.spec.template is required"))?;
     let resource_limits = docker_resource_limits(template)?;
     let user_mounts = docker_driver_mounts(driver_config)?;
+    let user_bind_strings = docker_driver_bind_strings(driver_config)?;
     let device_requests = gpu_device_ids.map(|device_ids| {
         vec![DeviceRequest {
             driver: Some("cdi".to_string()),
@@ -2298,7 +2356,11 @@ fn build_container_create_body_with_gpu_devices(
             memory: resource_limits.memory_bytes,
             pids_limit: docker_pids_limit(config.sandbox_pids_limit)?,
             device_requests,
-            binds: Some(build_binds(sandbox, config)?),
+            binds: {
+                let mut binds = build_binds(sandbox, config)?;
+                binds.extend(user_bind_strings);
+                Some(binds)
+            },
             mounts: Some(user_mounts),
             restart_policy: Some(RestartPolicy {
                 name: Some(RestartPolicyNameEnum::UNLESS_STOPPED),

crates/openshell-driver-docker/src/tests.rs

@@ -801,17 +801,25 @@ fn build_container_create_body_includes_bind_mounts_when_enabled() {
     config.enable_bind_mounts = true;
 
     let body = build_container_create_body(&sandbox, &config).unwrap();
-    let mounts = body
+    let binds = body
         .host_config
+        .as_ref()
         .unwrap()
-        .mounts
-        .expect("driver config mounts should be set");
+        .binds
+        .as_ref()
+        .expect("binds should be set");
 
-    assert_eq!(mounts.len(), 1);
-    assert_eq!(mounts[0].typ, Some(MountTypeEnum::BIND));
-    assert_eq!(mounts[0].source.as_deref(), Some("/host/path"));
-    assert_eq!(mounts[0].target.as_deref(), Some("/sandbox/host"));
-    assert_eq!(mounts[0].read_only, Some(true));
+    // User bind mount appears after the system binds.
+    assert!(
+        binds.iter().any(|b| b == "/host/path:/sandbox/host:ro"),
+        "expected bind entry '/host/path:/sandbox/host:ro', got {binds:?}"
+    );
+    // Bind mounts must not appear in the structured mounts vec.
+    let mounts = body.host_config.unwrap().mounts.unwrap_or_default();
+    assert!(
+        mounts.iter().all(|m| m.typ != Some(MountTypeEnum::BIND)),
+        "bind mounts should not appear in structured mounts"
+    );
 }
 
 #[test]
@@ -835,13 +843,122 @@ fn driver_config_defaults_enabled_bind_mounts_to_read_only() {
     config.enable_bind_mounts = true;
 
     let body = build_container_create_body(&sandbox, &config).unwrap();
-    let mounts = body
+    let binds = body
         .host_config
         .unwrap()
-        .mounts
-        .expect("driver config mounts should be set");
+        .binds
+        .expect("binds should be set");
 
-    assert_eq!(mounts[0].read_only, Some(true));
+    assert!(
+        binds
+            .iter()
+            .any(|b| b.contains("/host/path:/sandbox/host:ro")),
+        "default bind mount should be read-only, got {binds:?}"
+    );
+}
+
+#[test]
+fn bind_mount_selinux_shared_label() {
+    let mut sandbox = test_sandbox();
+    sandbox
+        .spec
+        .as_mut()
+        .unwrap()
+        .template
+        .as_mut()
+        .unwrap()
+        .driver_config = Some(json_struct(serde_json::json!({
+        "mounts": [{
+            "type": "bind",
+            "source": "/data/shared",
+            "target": "/sandbox/data",
+            "read_only": true,
+            "selinux_label": "shared"
+        }]
+    })));
+    let mut config = runtime_config();
+    config.enable_bind_mounts = true;
+
+    let body = build_container_create_body(&sandbox, &config).unwrap();
+    let binds = body
+        .host_config
+        .unwrap()
+        .binds
+        .expect("binds should be set");
+
+    assert!(
+        binds.iter().any(|b| b == "/data/shared:/sandbox/data:ro,z"),
+        "expected ':ro,z' label, got {binds:?}"
+    );
+}
+
+#[test]
+fn bind_mount_selinux_private_label() {
+    let mut sandbox = test_sandbox();
+    sandbox
+        .spec
+        .as_mut()
+        .unwrap()
+        .template
+        .as_mut()
+        .unwrap()
+        .driver_config = Some(json_struct(serde_json::json!({
+        "mounts": [{
+            "type": "bind",
+            "source": "/data/exclusive",
+            "target": "/sandbox/data",
+            "read_only": false,
+            "selinux_label": "private"
+        }]
+    })));
+    let mut config = runtime_config();
+    config.enable_bind_mounts = true;
+
+    let body = build_container_create_body(&sandbox, &config).unwrap();
+    let binds = body
+        .host_config
+        .unwrap()
+        .binds
+        .expect("binds should be set");
+
+    assert!(
+        binds.iter().any(|b| b == "/data/exclusive:/sandbox/data:Z"),
+        "expected ':Z' label, got {binds:?}"
+    );
+}
+
+#[test]
+fn bind_mount_without_selinux_label() {
+    let mut sandbox = test_sandbox();
+    sandbox
+        .spec
+        .as_mut()
+        .unwrap()
+        .template
+        .as_mut()
+        .unwrap()
+        .driver_config = Some(json_struct(serde_json::json!({
+        "mounts": [{
+            "type": "bind",
+            "source": "/host/path",
+            "target": "/sandbox/host",
+            "read_only": false
+        }]
+    })));
+    let mut config = runtime_config();
+    config.enable_bind_mounts = true;
+
+    let body = build_container_create_body(&sandbox, &config).unwrap();
+    let binds = body
+        .host_config
+        .unwrap()
+        .binds
+        .expect("binds should be set");
+
+    assert!(
+        binds.iter().any(|b| b == "/host/path:/sandbox/host"),
+        "expected no options suffix, got {binds:?}"
+    );
 }
 
 #[test]