Rewrite our 2G downgrade analyzer

lib/src/analysis/analyzer.rs

@@ -7,7 +7,7 @@ use crate::{diag::MessagesContainer, gsmtap_parser};
 use super::{
     imsi_requested::ImsiRequestedAnalyzer,
     information_element::InformationElement,
-    lte_downgrade::LteSib6And7DowngradeAnalyzer,
+    lte_downgrade::ConnectionRedirect2GDowngradeAnalyzer,
     null_cipher::NullCipherAnalyzer,
 };
 
@@ -117,7 +117,7 @@ impl Harness {
 
     pub fn new_with_all_analyzers() -> Self {
         let mut harness = Harness::new();
-        harness.add_analyzer(Box::new(LteSib6And7DowngradeAnalyzer{}));
+        harness.add_analyzer(Box::new(ConnectionRedirect2GDowngradeAnalyzer{}));
         harness.add_analyzer(Box::new(ImsiRequestedAnalyzer::new()));
         harness.add_analyzer(Box::new(NullCipherAnalyzer{}));
 

lib/src/analysis/lte_downgrade.rs

@@ -2,80 +2,40 @@ use std::borrow::Cow;
 
 use super::analyzer::{Analyzer, Event, EventType, Severity};
 use super::information_element::{InformationElement, LteInformationElement};
-use telcom_parser::lte_rrc::{BCCH_DL_SCH_MessageType, BCCH_DL_SCH_MessageType_c1, CellReselectionPriority, SystemInformationBlockType7, SystemInformationCriticalExtensions, SystemInformation_r8_IEsSib_TypeAndInfo, SystemInformation_r8_IEsSib_TypeAndInfo_Entry};
+use telcom_parser::lte_rrc::{DL_DCCH_Message, DL_DCCH_MessageType, DL_DCCH_MessageType_c1, RRCConnectionReleaseCriticalExtensions, RRCConnectionReleaseCriticalExtensions_c1, RedirectedCarrierInfo};
+use super::util::unpack;
 
 /// Based on heuristic T7 from Shinjo Park's "Why We Cannot Win".
-pub struct LteSib6And7DowngradeAnalyzer {
+pub struct ConnectionRedirect2GDowngradeAnalyzer {
-}
-
-impl LteSib6And7DowngradeAnalyzer {
-    fn unpack_system_information<'a>(&self, ie: &'a InformationElement) -> Option<&'a SystemInformation_r8_IEsSib_TypeAndInfo> {
-        if let InformationElement::LTE(LteInformationElement::BcchDlSch(bcch_dl_sch_message)) = ie {
-            if let BCCH_DL_SCH_MessageType::C1(BCCH_DL_SCH_MessageType_c1::SystemInformation(system_information)) = &bcch_dl_sch_message.message {
-                if let SystemInformationCriticalExtensions::SystemInformation_r8(sib) = &system_information.critical_extensions {
-                    return Some(&sib.sib_type_and_info);
-                }
-            }
-        }
-        None
-    }
 }
 
 // TODO: keep track of SIB state to compare LTE reselection blocks w/ 2g/3g ones
-impl Analyzer for LteSib6And7DowngradeAnalyzer {
+impl Analyzer for ConnectionRedirect2GDowngradeAnalyzer {
     fn get_name(&self) -> Cow<str> {
-        Cow::from("LTE SIB 6/7 Downgrade")
+        Cow::from("Connection Release/Redirected Carrier 2G Downgrade")
     }
 
     fn get_description(&self) -> Cow<str> {
-        Cow::from("Tests for LTE cells broadcasting a SIB type 6 and 7 which include 2G/3G frequencies with higher priorities.")
+        Cow::from("Tests if a cell releases our connection and redirects us to a 2G cell.")
     }
 
-    fn analyze_information_element(&mut self, ie: &InformationElement) -> Option<super::analyzer::Event> {
+    fn analyze_information_element(&mut self, ie: &InformationElement) -> Option<Event> {
-        let sibs = &self.unpack_system_information(ie)?.0;
+        unpack!(InformationElement::LTE(lte_ie) = ie);
-        for sib in sibs {
+        unpack!(LteInformationElement::DlDcch(DL_DCCH_Message { message }) = lte_ie);
-            match sib {
+        unpack!(DL_DCCH_MessageType::C1(c1) = message);
-                SystemInformation_r8_IEsSib_TypeAndInfo_Entry::Sib6(sib6) => {
+        unpack!(DL_DCCH_MessageType_c1::RrcConnectionRelease(release) = c1);
-                    if let Some(carrier_info_list) = sib6.carrier_freq_list_utra_fdd.as_ref() {
+        unpack!(RRCConnectionReleaseCriticalExtensions::C1(c1) = &release.critical_extensions);
-                        for carrier_info in &carrier_info_list.0 {
+        unpack!(RRCConnectionReleaseCriticalExtensions_c1::RrcConnectionRelease_r8(r8_ies) = c1);
-                            if let Some(CellReselectionPriority(p)) = carrier_info.cell_reselection_priority {
+        unpack!(Some(carrier_info) = &r8_ies.redirected_carrier_info);
-                                if p == 0 {
+        match carrier_info {
-                                    return Some(Event {
+            RedirectedCarrierInfo::Geran(_carrier_freqs_geran) => Some(Event {
-                                        event_type: EventType::QualitativeWarning { severity: Severity::High },
+                event_type: EventType::QualitativeWarning { severity: Severity::High },
-                                        message: "LTE cell advertised a 3G cell for priority 0 reselection".to_string(),
+                message: format!("Detected 2G downgrade"),
-                                    });
+            }),
-                                }
+            _ => Some(Event {
-                            }
+                event_type: EventType::Informational,
-                        }
+                message: format!("RRCConnectionRelease CarrierInfo: {:?}", carrier_info),
-                    }
+            }),
-                    if let Some(carrier_info_list) = sib6.carrier_freq_list_utra_tdd.as_ref() {
-                        for carrier_info in &carrier_info_list.0 {
-                            if let Some(CellReselectionPriority(p)) = carrier_info.cell_reselection_priority {
-                                if p == 0 {
-                                    return Some(Event {
-                                        event_type: EventType::QualitativeWarning { severity: Severity::High },
-                                        message: "LTE cell advertised a 3G cell for priority 0 reselection".to_string(),
-                                    });
-                                }
-                            }
-                        }
-                    }
-                },
-                SystemInformation_r8_IEsSib_TypeAndInfo_Entry::Sib7(SystemInformationBlockType7 { carrier_freqs_info_list: Some(carrier_info_list), .. }) => {
-                    for carrier_info in &carrier_info_list.0 {
-                        if let Some(CellReselectionPriority(p)) = carrier_info.common_info.cell_reselection_priority {
-                            if p == 0 {
-                                return Some(Event {
-                                    event_type: EventType::QualitativeWarning { severity: Severity::High },
-                                    message: "LTE cell advertised a 2G cell for priority 0 reselection".to_string(),
-                                });
-                            }
-                        }
-                    }
-                },
-                _ => {},
-            }
         }
-        None
     }
 }

lib/src/analysis/mod.rs

@@ -4,3 +4,4 @@ pub mod lte_downgrade;
 pub mod imsi_provided;
 pub mod imsi_requested;
 pub mod null_cipher;
+pub mod util;

lib/src/analysis/util.rs

@@ -0,0 +1,7 @@
+macro_rules! unpack {
+    ($pat:pat = $val:expr) => {
+        let $pat = $val else { return None; };
+    };
+}
+
+pub(crate) use unpack;