Prevent Invalid Curve Attack on 5G SUCI Feature (#20)

* Prevent Invalid Curve Attack on 5G SUCI Feature

* add test case of detecting invalid cure attack

* fix comment

* change test case err type

---------

Co-authored-by: Roy-Hu <r74774777@gmail.com>
Co-authored-by: roy19991013 <80-ChienAn@users.noreply.gitlab.nems.cs.nctu.edu.tw>

pkg/suci/suci.go

@@ -218,6 +218,20 @@ func profileA(input, supiType, privateKey string) (string, error) {
 	return calcSchemeResult(decryptPlainText, supiType), nil
 }
 
+func checkOnCurve(curve elliptic.Curve, x, y *big.Int) error {
+	// (0, 0) is the point at infinity by convention. It's ok to operate on it,
+	// although IsOnCurve is documented to return false for it. See Issue 37294.
+	if x.Sign() == 0 && y.Sign() == 0 {
+		return nil
+	}
+
+	if !curve.IsOnCurve(x, y) {
+		return fmt.Errorf("crypto/elliptic: attempted operation on invalid point")
+	}
+
+	return nil
+}
+
 func profileB(input, supiType, privateKey string) (string, error) {
 	logger.SuciLog.Infoln("SuciToSupi Profile B")
 	s, hexDecodeErr := hex.DecodeString(input)
@@ -271,6 +285,10 @@ func profileB(input, supiType, privateKey string) (string, error) {
 	}
 	// fmt.Printf("xUncom: %x\nyUncom: %x\n", xUncompressed, yUncompressed)
 
+	if err := checkOnCurve(elliptic.P256(), xUncompressed, yUncompressed); err != nil {
+		return "", err
+	}
+
 	// x-coordinate is the shared key
 	decryptSharedKey, _ := elliptic.P256().ScalarMult(xUncompressed, yUncompressed, bHNPriv)
 	// fmt.Printf("deShared: %x\n", decryptSharedKey.Bytes())

pkg/suci/suci_test.go

@@ -1,6 +1,9 @@
 package suci
 
-import "testing"
+import (
+	"fmt"
+	"testing"
+)
 
 func TestToSupi(t *testing.T) {
 	suciProfiles := []SuciProfile{
@@ -17,30 +20,42 @@ func TestToSupi(t *testing.T) {
 		},
 	}
 	testCases := []struct {
-		suci     string
-		expected string
+		suci         string
+		expectedSupi string
+		expectedErr  error
 	}{
 		{
-			suci:     "suci-0-208-93-0-0-0-00007487",
-			expected: "imsi-2089300007487",
+			suci:         "suci-0-208-93-0-0-0-00007487",
+			expectedSupi: "imsi-2089300007487",
+			expectedErr:  nil,
 		},
 		{
 			suci: "suci-0-208-93-0-1-1-b2e92f836055a255837debf850b528997ce0201cb82a" +
 				"dfe4be1f587d07d8457dcb02352410cddd9e730ef3fa87",
-			expected: "imsi-20893001002086",
+			expectedSupi: "imsi-20893001002086",
+			expectedErr:  nil,
 		},
 		{
 			suci: "suci-0-208-93-0-2-2-039aab8376597021e855679a9778ea0b67396e68c66d" +
 				"f32c0f41e9acca2da9b9d146a33fc2716ac7dae96aa30a4d",
-			expected: "imsi-20893001002086",
+			expectedSupi: "imsi-20893001002086",
+			expectedErr:  nil,
+		},
+		{
+			suci: "suci-0-208-93-0-2-2-0434a66778799d52fedd9326db4b690d092e05c9ba0ace5b413da" +
+				"fc0a40aa28ee00a79f790fa4da6a2ece892423adb130dc1b30e270b7d0088bdd716b93894891d5221a74c810d6b9350cc067c76",
+			expectedSupi: "",
+			expectedErr:  fmt.Errorf("crypto/elliptic: attempted operation on invalid point"),
 		},
 	}
 	for i, tc := range testCases {
 		supi, err := ToSupi(tc.suci, suciProfiles)
 		if err != nil {
-			t.Errorf("TC%d err: %+v\n", i, err)
-		} else if supi != tc.expected {
-			t.Errorf("TC%d fail: supi[%s], expected[%s]\n", i, supi, tc.expected)
+			if err.Error() != tc.expectedErr.Error() {
+				t.Errorf("TC%d fail: err[%s], expected[%s]\n", i, err, tc.expectedErr)
+			}
+		} else if supi != tc.expectedSupi {
+			t.Errorf("TC%d fail: supi[%s], expected[%s]\n", i, supi, tc.expectedSupi)
 		}
 	}
 }