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fix: preserve UE security capability on path switch #224

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fix: preserve UE security capability on path switch #224

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e4f9bcb
fix: preserve UE security capability on path switch
wiwi878 Jun 24, 2026
dedba76
fix: address path switch CI failures
wiwi878 Jun 24, 2026
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39 changes: 32 additions & 7 deletions internal/ngap/handler.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1300,13 +1300,15 @@ func handlePathSwitchRequestMain(ran *context.AmfRan,
}

if uESecurityCapabilities != nil {
amfUe.UESecurityCapability.SetEA1_128_5G(uESecurityCapabilities.NRencryptionAlgorithms.Value.Bytes[0] & 0x80)
amfUe.UESecurityCapability.SetEA2_128_5G(uESecurityCapabilities.NRencryptionAlgorithms.Value.Bytes[0] & 0x40)
amfUe.UESecurityCapability.SetEA3_128_5G(uESecurityCapabilities.NRencryptionAlgorithms.Value.Bytes[0] & 0x20)
amfUe.UESecurityCapability.SetIA1_128_5G(uESecurityCapabilities.NRintegrityProtectionAlgorithms.Value.Bytes[0] & 0x80)
amfUe.UESecurityCapability.SetIA2_128_5G(uESecurityCapabilities.NRintegrityProtectionAlgorithms.Value.Bytes[0] & 0x40)
amfUe.UESecurityCapability.SetIA3_128_5G(uESecurityCapabilities.NRintegrityProtectionAlgorithms.Value.Bytes[0] & 0x20)
// not support any E-UTRA algorithms
storedEA, storedIA := storedNRUESecurityCapability(amfUe)
receivedEA, receivedIA := receivedNRUESecurityCapability(uESecurityCapabilities)
if storedEA != receivedEA || storedIA != receivedIA {
// TODO: Include E-UTRA capability once AmfUe stores it; current NGAP builders only preserve NR bits.
ranUe.Log.Warnf("UESecurityCapabilities mismatch in PathSwitchRequest: "+
"stored NR(EA=0x%02x, IA=0x%02x), received NR(EA=0x%02x, IA=0x%02x); "+
"keep stored UE security capability",
storedEA, storedIA, receivedEA, receivedIA)
}
}

if rANUENGAPID != nil {
Expand Down Expand Up @@ -1410,6 +1412,29 @@ func handlePathSwitchRequestMain(ran *context.AmfRan,
}
}

func storedNRUESecurityCapability(amfUe *context.AmfUe) (nrEncryptionAlgorithm, nrIntegrityAlgorithm byte) {
nrEncryptionAlgorithm |= amfUe.UESecurityCapability.GetEA1_128_5G() << 7
nrEncryptionAlgorithm |= amfUe.UESecurityCapability.GetEA2_128_5G() << 6
nrEncryptionAlgorithm |= amfUe.UESecurityCapability.GetEA3_128_5G() << 5

nrIntegrityAlgorithm |= amfUe.UESecurityCapability.GetIA1_128_5G() << 7
nrIntegrityAlgorithm |= amfUe.UESecurityCapability.GetIA2_128_5G() << 6
nrIntegrityAlgorithm |= amfUe.UESecurityCapability.GetIA3_128_5G() << 5
return
}

func receivedNRUESecurityCapability(
uESecurityCapabilities *ngapType.UESecurityCapabilities,
) (nrEncryptionAlgorithm, nrIntegrityAlgorithm byte) {
if len(uESecurityCapabilities.NRencryptionAlgorithms.Value.Bytes) > 0 {
nrEncryptionAlgorithm = uESecurityCapabilities.NRencryptionAlgorithms.Value.Bytes[0] & 0xe0
}
if len(uESecurityCapabilities.NRintegrityProtectionAlgorithms.Value.Bytes) > 0 {
nrIntegrityAlgorithm = uESecurityCapabilities.NRintegrityProtectionAlgorithms.Value.Bytes[0] & 0xe0
}
return
}

func handleHandoverRequestAcknowledgeMain(ran *context.AmfRan,
targetUe *context.RanUe,
rANUENGAPID *ngapType.RANUENGAPID,
Expand Down
46 changes: 46 additions & 0 deletions internal/ngap/handler_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ import (
"encoding/hex"
"fmt"
"net"
"strings"
"testing"

"github.com/google/uuid"
Expand Down Expand Up @@ -156,6 +157,51 @@ func NewAmfContext(amfCtx *amf_context.AMFContext) {
}
}

func TestHandlePathSwitchRequestKeepsStoredUESecurityCapabilityOnMismatch(t *testing.T) {
amfSelf := amf_context.GetSelf()
NewAmfContext(amfSelf)

sourceRan := NewAmfRan(nil)
sourceRan.AnType = "3GPP_ACCESS"
ranUe := &amf_context.RanUe{
Ran: sourceRan,
RanUeNgapId: 1,
AmfUeNgapId: 1,
Log: sourceRan.Log,
}
sourceRan.RanUeList.Store(ranUe.RanUeNgapId, ranUe)
amfSelf.RanUePool.Store(ranUe.AmfUeNgapId, ranUe)

amfUe := amfSelf.NewAmfUe("imsi-208930000007487")
amfUe.SecurityContextAvailable = true
amfUe.NgKsi.Ksi = 1
amfUe.Kamf = strings.Repeat("11", 32)
amfUe.NH = []byte(strings.Repeat("\x22", 32))
amfUe.UESecurityCapability = nasType.UESecurityCapability{
Iei: nasMessage.RegistrationRequestUESecurityCapabilityType,
Len: 2,
Buffer: []uint8{0x00, 0x00},
}
amfUe.UESecurityCapability.SetIA2_128_5G(1)

ranUe.AmfUe = amfUe
amfUe.RanUe["3GPP_ACCESS"] = ranUe

targetRan := NewAmfRan(nil)
targetRan.AnType = "3GPP_ACCESS"
sourceAMFUeNgapID := ngapType.AMFUENGAPID{Value: ranUe.AmfUeNgapId}
ranUeNgapID := ngapType.RANUENGAPID{Value: 2}
received := &ngapType.UESecurityCapabilities{}
received.NRencryptionAlgorithms.Value = aper.BitString{Bytes: []byte{0x00, 0x00}, BitLength: 16}
received.NRintegrityProtectionAlgorithms.Value = aper.BitString{Bytes: []byte{0x00, 0x00}, BitLength: 16}

handlePathSwitchRequestMain(targetRan, &ranUeNgapID, &sourceAMFUeNgapID, nil, received, nil, nil)

require.Equal(t, uint8(1), amfUe.UESecurityCapability.GetIA2_128_5G())
require.Equal(t, uint8(0), amfUe.UESecurityCapability.GetIA1_128_5G())
require.Equal(t, uint8(0), amfUe.UESecurityCapability.GetIA3_128_5G())
}

func BuildInitialUEMessage(ranUeNgapID int64, nasPdu []byte, fiveGSTmsi string) ngapType.NGAPPDU {
var TestPlmn ngapType.PLMNIdentity
var tmsi aper.OctetString
Expand Down
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