genpolicy: container.exec_commands args validation

Keep track of individual exec args instead of joining them in the
policy text. Verifying each arg results in a more precise policy,
because some of the args might include space characters.

This improved validation applies to commands specified in K8s YAML
files using:

- livenessProbe
- readinessProbe
- startupProbe
- lifecycle.postStart
- lifecycle.preStop

Signed-off-by: Dan Mihai <dmihai@microsoft.com>

src/tools/genpolicy/rules.rego

@@ -1124,15 +1124,12 @@ ExecProcessRequest {
     print("ExecProcessRequest 2: input =", input)
 
     # TODO: match input container ID with its corresponding container.exec_commands.
-    i_command = concat(" ", input.process.Args)
-    print("ExecProcessRequest 3: i_command =", i_command)
-
     some container in policy_data.containers
     some p_command in container.exec_commands
     print("ExecProcessRequest 2: p_command =", p_command)
 
     # TODO: should other input data fields be validated as well?
-    p_command == i_command
+    p_command == input.process.Args
 
     print("ExecProcessRequest 2: true")
 }

src/tools/genpolicy/src/pod.rs

@@ -614,36 +614,36 @@ impl Container {
         (yaml_has_command, yaml_has_args)
     }
 
-    pub fn get_exec_commands(&self) -> Vec<String> {
+    pub fn get_exec_commands(&self) -> Vec<Vec<String>> {
         let mut commands = Vec::new();
 
         if let Some(probe) = &self.livenessProbe {
             if let Some(exec) = &probe.exec {
-                commands.push(exec.command.join(" "));
+                commands.push(exec.command.clone());
             }
         }
 
         if let Some(probe) = &self.readinessProbe {
             if let Some(exec) = &probe.exec {
-                commands.push(exec.command.join(" "));
+                commands.push(exec.command.clone());
             }
         }
 
         if let Some(probe) = &self.startupProbe {
             if let Some(exec) = &probe.exec {
-                commands.push(exec.command.join(" "));
+                commands.push(exec.command.clone());
             }
         }
 
         if let Some(lifecycle) = &self.lifecycle {
             if let Some(postStart) = &lifecycle.postStart {
                 if let Some(exec) = &postStart.exec {
-                    commands.push(exec.command.join(" "));
+                    commands.push(exec.command.clone());
                 }
             }
             if let Some(preStop) = &lifecycle.preStop {
                 if let Some(exec) = &preStop.exec {
-                    commands.push(exec.command.join(" "));
+                    commands.push(exec.command.clone());
                 }
             }
         }

src/tools/genpolicy/src/policy.rs

@@ -271,7 +271,7 @@ pub struct ContainerPolicy {
     /// Allow list of ommand lines that are allowed to be executed using
     /// ExecProcessRequest. By default, all ExecProcessRequest calls are blocked
     /// by the policy.
-    exec_commands: Vec<String>,
+    exec_commands: Vec<Vec<String>>,
 }
 
 /// See Reference / Kubernetes API / Config and Storage Resources / Volume.

tests/integration/kubernetes/k8s-policy-pod.bats

@@ -205,12 +205,8 @@ test_pod_policy_error() {
 	pod_exec_allowed_command "${pod_name}" "sh" "-c" "ls -l /"
 	pod_exec_allowed_command "${pod_name}" "echo" "startupProbe" "test"
 
-	# This test should fail but it passes because genpolicy joins the exec args from its
-	# input K8s YAML file and from the command being executed, and compares the joined
-	# command lines instead of comparing each argument.
-	pod_exec_allowed_command "${pod_name}" "echo" "livenessProbe test"
-
 	# Try to execute commands disallowed by the policy.
+	pod_exec_blocked_command "${pod_name}" "echo" "livenessProbe test"
 	pod_exec_blocked_command "${pod_name}" "echo" "livenessProbe" "test2"
 	pod_exec_blocked_command "${pod_name}" "echo" "livenessProbe" "test" "yes"
 	pod_exec_blocked_command "${pod_name}" "echo" "livenessProbe" "test foo"