policy: support policy document versioning

On genpolicy side, encode the policy docuemtn version being used.

On the agent side, read the version from the policy document and allow request accordingly.

This allows the agent to handle multiple policy document versions.

Signed-off-by: Saul Paredes <saulparedes@microsoft.com>

Author: Redent0r

src/agent/policy/src/policy.rs

@@ -63,6 +63,8 @@ pub struct AgentPolicy {
 
     /// Regorus engine
     engine: regorus::Engine,
+
+    policy_document_version: PolicyDocumentVersion,
 }
 
 #[derive(serde::Deserialize, Debug)]
@@ -127,6 +129,7 @@ impl AgentPolicy {
 
         self.engine.add_policy_from_file(default_policy_file)?;
         self.update_allow_failures_flag().await?;
+        self.update_policy_version().await?;
         Ok(())
     }
 
@@ -149,6 +152,12 @@ impl AgentPolicy {
 
     /// Ask regorus if an API call should be allowed or not.
     pub async fn allow_request(&mut self, ep: &str, ep_input: &str) -> Result<(bool, String)> {
+        match self.policy_document_version {
+            PolicyDocumentVersion::V1 => self.allow_request_default(ep, ep_input).await,
+        }
+    }
+
+    async fn allow_request_default(&mut self, ep: &str, ep_input: &str) -> Result<(bool, String)> {
         debug!(sl!(), "policy check: {ep}");
         self.log_request(ep, ep_input).await;
 
@@ -266,6 +275,35 @@ impl AgentPolicy {
         };
         Ok(())
     }
+
+    async fn update_policy_version(&mut self) -> Result<()> {
+        let query = format!("data.agent_policy.policy_data.version");
+        self.engine.set_input_json("{}")?;
+
+        let results = self.engine.eval_query(query.clone(), false)?;
+
+        if results.result.len() < 1 || results.result[0].expressions.len() < 1 {
+            warn!(
+                sl!(),
+                "policy: failed to parse policy version. Assuming default policy version"
+            );
+            return Ok(());
+        }
+
+        self.policy_document_version =
+            match serde_json::from_str(&results.result[0].expressions[0].value.to_string()) {
+                Ok(v) => v,
+                Err(e) => {
+                    warn!(
+                    sl!(),
+                    "policy: failed to parse policy version: {e}. Assuming default policy version"
+                );
+                    PolicyDocumentVersion::default()
+                }
+            };
+
+        return Ok(());
+    }
 }
 
 pub fn check_policy_hash(policy: &str) -> Result<()> {
@@ -288,3 +326,9 @@ pub fn check_policy_hash(policy: &str) -> Result<()> {
 
     Ok(())
 }
+
+#[derive(Debug, serde::Serialize, serde::Deserialize, Default)]
+pub enum PolicyDocumentVersion {
+    #[default]
+    V1,
+}

src/tools/genpolicy/Cargo.toml

@@ -65,9 +65,10 @@ tonic = "0.9.2"
 tower = "0.4.13"
 [target.'cfg(target_os = "linux")'.dependencies]
 containerd-client = "0.4.0"
-
-[dev-dependencies]
 kata-agent-policy = { path = "../../agent/policy" }
-slog = "2.5.2"
 # Kata Agent protocol.
 protocols = { path = "../../libs/protocols", features = ["with-serde"] }
+
+[dev-dependencies]
+slog = "2.5.2"
+

src/tools/genpolicy/src/policy.rs

@@ -74,6 +74,9 @@ pub struct PolicyData {
     /// Settings read from genpolicy-settings.json, related directly to each
     /// kata agent endpoint, that get added to the output policy.
     pub request_defaults: RequestDefaults,
+
+    /// Policy Document version
+    pub version: kata_agent_policy::policy::PolicyDocumentVersion,
 }
 
 /// OCI Container spec. This struct is very similar to the Spec struct from
@@ -560,6 +563,7 @@ impl AgentPolicy {
             request_defaults: self.settings.request_defaults.clone(),
             common: self.settings.common.clone(),
             sandbox: self.settings.sandbox.clone(),
+            version: kata_agent_policy::policy::PolicyDocumentVersion::V1,
         };
 
         let json_data = serde_json::to_string_pretty(&policy_data).unwrap();