lib: add analyzer for a null cipher being set

lib/src/analysis/null_cipher.rs

@@ -0,0 +1,115 @@
+use std::borrow::Cow;
+
+use telcom_parser::lte_rrc::{CipheringAlgorithm_r12, DL_CCCH_MessageType, DL_CCCH_MessageType_c1, DL_DCCH_MessageType, DL_DCCH_MessageType_c1, PCCH_MessageType, PCCH_MessageType_c1, PagingUE_Identity, RRCConnectionReconfiguration, RRCConnectionReconfigurationCriticalExtensions, RRCConnectionReconfigurationCriticalExtensions_c1, RRCConnectionReconfiguration_r8_IEs, RRCConnectionRelease_v890_IEs, SCG_Configuration_r12, SecurityConfigHO_v1530HandoverType_v1530, SecurityModeCommand, SecurityModeCommandCriticalExtensions, SecurityModeCommandCriticalExtensions_c1};
+
+use super::analyzer::{Analyzer, Event, EventType, Severity};
+use super::information_element::{InformationElement, LteInformationElement};
+
+pub struct NullCipherAnalyzer {
+}
+
+impl NullCipherAnalyzer {
+    fn check_rrc_connection_reconfiguration_cipher(&self, reconfiguration: &RRCConnectionReconfiguration) -> bool {
+        let RRCConnectionReconfigurationCriticalExtensions::C1(c1) = &reconfiguration.critical_extensions else {
+            return false;
+        };
+        let RRCConnectionReconfigurationCriticalExtensions_c1::RrcConnectionReconfiguration_r8(c1) = c1 else {
+            return false;
+        };
+        if let Some(handover) = &c1.security_config_ho {
+            let maybe_security_config = match &handover.handover_type {
+                telcom_parser::lte_rrc::SecurityConfigHOHandoverType::IntraLTE(lte) => lte.security_algorithm_config.as_ref(),
+                telcom_parser::lte_rrc::SecurityConfigHOHandoverType::InterRAT(rat) => Some(&rat.security_algorithm_config),
+            };
+            if let Some(security_config) = maybe_security_config {
+                if security_config.ciphering_algorithm.0 == CipheringAlgorithm_r12::EEA0 {
+                    return true;
+                }
+            }
+        }
+        // Use map/flatten to dig into a long chain of nested Option types
+        let maybe_v1250 = c1.non_critical_extension.as_ref()
+            .map(|v890| v890.non_critical_extension.as_ref()).flatten()
+            .map(|v920| v920.non_critical_extension.as_ref()).flatten()
+            .map(|v1020| v1020.non_critical_extension.as_ref()).flatten()
+            .map(|v1130| v1130.non_critical_extension.as_ref()).flatten();
+        let Some(v1250) = maybe_v1250 else {
+            return false;
+        };
+
+        if let Some(SCG_Configuration_r12::Setup(scg_setup)) = v1250.scg_configuration_r12.as_ref() {
+            let maybe_cipher = scg_setup.scg_config_part_scg_r12.as_ref()
+                .map(|scg| scg.mobility_control_info_scg_r12.as_ref()).flatten()
+                .map(|mci| mci.ciphering_algorithm_scg_r12.as_ref()).flatten();
+            if let Some(cipher) = maybe_cipher {
+                if cipher.0 == CipheringAlgorithm_r12::EEA0 {
+                    return true;
+                }
+            }
+        }
+
+        let maybe_v1530_security_config = v1250.non_critical_extension.as_ref()
+            .map(|v1310| v1310.non_critical_extension.as_ref()).flatten()
+            .map(|v1430| v1430.non_critical_extension.as_ref()).flatten()
+            .map(|v1510| v1510.non_critical_extension.as_ref()).flatten()
+            .map(|v1530| v1530.security_config_ho_v1530.as_ref()).flatten();
+        let Some(v1530_security_config) = maybe_v1530_security_config else {
+            return false;
+        };
+        let maybe_security_algorithm = match &v1530_security_config.handover_type_v1530 {
+            SecurityConfigHO_v1530HandoverType_v1530::Intra5GC(intra_5gc) => intra_5gc.security_algorithm_config_r15.as_ref(),
+            SecurityConfigHO_v1530HandoverType_v1530::Fivegc_ToEPC(to_epc) => Some(&to_epc.security_algorithm_config_r15),
+            SecurityConfigHO_v1530HandoverType_v1530::Epc_To5GC(to_5gc) => Some(&to_5gc.security_algorithm_config_r15),
+        };
+        if let Some(security_algorithm) = maybe_security_algorithm {
+            if security_algorithm.ciphering_algorithm.0 == CipheringAlgorithm_r12::EEA0 {
+                return true;
+            }
+        }
+        false
+    }
+
+    fn check_security_mode_command_cipher(&self, command: &SecurityModeCommand) -> bool {
+        let SecurityModeCommandCriticalExtensions::C1(c1) = &command.critical_extensions else {
+            return false;
+        };
+        let SecurityModeCommandCriticalExtensions_c1::SecurityModeCommand_r8(r8) = &c1 else {
+            return false;
+        };
+        if r8.security_config_smc.security_algorithm_config.ciphering_algorithm.0 == CipheringAlgorithm_r12::EEA0 {
+            return true;
+        }
+        false
+    }
+}
+
+impl Analyzer for NullCipherAnalyzer {
+    fn get_name(&self) -> Cow<str> {
+        Cow::from("Null Cipher")
+    }
+
+    fn get_description(&self) -> Cow<str> {
+        Cow::from("Tests whether the cell suggests using a null cipher (EEA0)")
+    }
+
+    fn analyze_information_element(&mut self, ie: &InformationElement) -> Option<Event> {
+        let InformationElement::LTE(LteInformationElement::DlDcch(dcch_msg)) = ie else {
+            return None;
+        };
+        let DL_DCCH_MessageType::C1(c1) = &dcch_msg.message else {
+            return None;
+        };
+        let null_cipher_detected = match c1 {
+            DL_DCCH_MessageType_c1::RrcConnectionReconfiguration(reconfiguration) => self.check_rrc_connection_reconfiguration_cipher(reconfiguration),
+            DL_DCCH_MessageType_c1::SecurityModeCommand(command) => self.check_security_mode_command_cipher(command),
+            _ => return None,
+        };
+        if null_cipher_detected {
+            return Some(Event {
+                event_type: EventType::QualitativeWarning { severity: Severity::High },
+                message: "Cell suggested use of null cipher".to_string(),
+            });
+        }
+        None
+    }
+}