add nas null cipher analyzer

lib/src/analysis/analyzer.rs

@@ -11,6 +11,7 @@ use super::{
     connection_redirect_downgrade::ConnectionRedirect2GDowngradeAnalyzer,
     imsi_requested::ImsiRequestedAnalyzer, information_element::InformationElement,
     null_cipher::NullCipherAnalyzer, priority_2g_downgrade::LteSib6And7DowngradeAnalyzer,
+    nas_null_cipher::NasNullCipherAnalyzer,
 };
 
 #[derive(Debug, Clone, Deserialize, Serialize)]
@@ -20,6 +21,7 @@ pub struct AnalyzerConfig {
     pub connection_redirect_2g_downgrade: bool,
     pub lte_sib6_and_7_downgrade: bool,
     pub null_cipher: bool,
+    pub nas_null_cipher: bool,
 }
 
 impl Default for AnalyzerConfig {
@@ -29,6 +31,7 @@ impl Default for AnalyzerConfig {
             connection_redirect_2g_downgrade: true,
             lte_sib6_and_7_downgrade: true,
             null_cipher: true,
+            nas_null_cipher: true
         }
     }
 }
@@ -162,6 +165,10 @@ impl Harness {
             harness.add_analyzer(Box::new(NullCipherAnalyzer {}));
         }
 
+        if analyzer_config.nas_null_cipher {
+            harness.add_analyzer(Box::new(NasNullCipherAnalyzer::new()))
+        }
+
         harness
     }
 

lib/src/analysis/mod.rs

@@ -4,5 +4,6 @@ pub mod imsi_provided;
 pub mod imsi_requested;
 pub mod information_element;
 pub mod null_cipher;
+pub mod nas_null_cipher;
 pub mod priority_2g_downgrade;
 pub mod util;

lib/src/analysis/nas_null_cipher.rs

@@ -0,0 +1,60 @@
+use std::borrow::Cow;
+
+use pycrate_rs::nas::emm::EMMMessage;
+use pycrate_rs::nas::generated::emm::emm_security_mode_command::NASSecAlgoCiphAlgo::EPSEncryptionAlgorithmEEA0Null;
+use pycrate_rs::nas::NASMessage;
+
+use super::analyzer::{Analyzer, Event, EventType, Severity};
+use super::information_element::{InformationElement, LteInformationElement};
+
+pub struct NasNullCipherAnalyzer {
+    packet_num: usize,
+}
+
+impl Default for NasNullCipherAnalyzer {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl NasNullCipherAnalyzer {
+    pub fn new() -> Self {
+        Self { packet_num: 0 }
+    }
+}
+
+impl Analyzer for NasNullCipherAnalyzer {
+    fn get_name(&self) -> Cow<str> {
+        Cow::from("NAS Null Cipher Requested")
+    }
+
+    fn get_description(&self) -> Cow<str> {
+        Cow::from("Tests whether the MME requests to use a null cipher in the security mode command")
+    }
+
+    fn analyze_information_element(&mut self, ie: &InformationElement) -> Option<Event> {
+        self.packet_num += 1;
+        let payload = match ie {
+            InformationElement::LTE(inner) => match &**inner {
+                LteInformationElement::NAS(payload) => payload,
+                _ => return None,
+            },
+            _ => return None,
+        };
+
+        if let NASMessage::EMMMessage(EMMMessage::EMMSecurityModeCommand(req)) = payload {
+            if req.nas_sec_algo.inner.ciph_algo == EPSEncryptionAlgorithmEEA0Null {
+                    return Some(Event {
+                        event_type: EventType::QualitativeWarning {
+                            severity: Severity::High,
+                        },
+                        message: format!(
+                            "NAS Security mode command requested null cipher(packet {})",
+                            self.packet_num
+                        ),
+                    });
+            }
+        }
+        None
+    }
+}