fix: IMEI/IMEISV validation and test cases

nasConvert/MobileIdentity5GS.go

@@ -7,6 +7,7 @@ import (
 	"math/bits"
 	"strconv"
 	"strings"
+	"unicode"
 
 	"github.com/free5gc/nas/logger"
 	"github.com/free5gc/nas/nasMessage"
@@ -282,5 +283,52 @@ func PeiToStringWithError(buf []byte) (string, error) {
 		digitStr = digitStr[:len(digitStr)-1] // remove the last digit
 	}
 
+	if prefix == "imei-" {
+		// Validate IMEI before returning
+		if len(digitStr) != 15 {
+			return "", fmt.Errorf("invalid IMEI length: expected 15 digits, got %d", len(digitStr))
+		}
+		valid, err := validateIMEI(digitStr)
+		if err != nil {
+			return "", fmt.Errorf("IMEI validation error: %w", err)
+		}
+		if !valid {
+			return "", fmt.Errorf("invalid IMEI checksum")
+		}
+	} else {
+		if len(digitStr) != 16 {
+			return "", fmt.Errorf("invalid IMEISV length: expected 16 digits, got %d", len(digitStr))
+		}
+	}
+
 	return prefix + digitStr, nil
 }
+
+func validateIMEI(imei string) (bool, error) {
+	// Remove any non-digit characters
+	cleanIMEI := strings.ReplaceAll(imei, "-", "")
+	cleanIMEI = strings.ReplaceAll(cleanIMEI, " ", "")
+
+	// Check if all characters are digits
+	for _, char := range cleanIMEI {
+		if !unicode.IsDigit(char) {
+			return false, fmt.Errorf("IMEI contains non-digit character: %c", char)
+		}
+	}
+
+	// Luhn algorithm validation
+	sum := 0
+	for i := len(cleanIMEI) - 1; i >= 0; i-- {
+		digit := int(cleanIMEI[i] - '0')
+
+		if (len(cleanIMEI)-i)%2 == 0 {
+			digit *= 2
+			if digit > 9 {
+				digit = digit/10 + digit%10
+			}
+		}
+		sum += digit
+	}
+
+	return sum%10 == 0, nil
+}

nasConvert/MobileIdentity5GS_test.go

@@ -311,40 +311,53 @@ func TestPeiToStringWithError(t *testing.T) {
 		wantErr bool
 	}{
 		{
-			name: "PEI-IMEI-even",
+			name: "Complete-Valid-IMEI",
 			args: args{
-				buf: []byte{0x3, 0xf1},
+				// Example encoding for a valid 15-digit IMEI
+				buf: []byte{
+					0x4b, 0x09, 0x51, 0x24, 0x30, 0x32, 0x57, 0x81,
+				},
 			},
-			want:    "imei-01",
+			want:    "imei-490154203237518",
 			wantErr: false,
 		},
 		{
-			name: "PEI-IMEISV-odd",
+			name: "Complete-Ivalid-IMEI",
 			args: args{
-				buf: []byte{0xd, 0x21},
+				// Not valid 15-digit IMEI: CD(Check Digit) not valid
+				buf: []byte{
+					0x4b, 0x09, 0x51, 0x24, 0x30, 0x32, 0x57, 0x82,
+				},
 			},
-			want:    "imeisv-012",
-			wantErr: false,
-		},
-		{
-			name:    "PEI-nil",
 			wantErr: true,
 		},
 		{
-			name: "PEI-IMEI-len1",
+			name: "Complete-Valid-IMEISV",
 			args: args{
-				buf: []byte{0xb},
+				buf: []byte{
+					0x90, 0x87, 0x65, 0x43, 0x21, 0x01, 0x23, 0x45, 0x60,
+				},
 			},
-			want:    "imei-0",
+			want:    "imeisv-9785634121032540",
 			wantErr: false,
 		},
 		{
-			name: "PEI-IMEI-len0",
+			name: "IMEI-TooLong",
 			args: args{
-				buf: []byte{0x3},
+				buf: []byte{
+					0x4b, 0x09, 0x51, 0x24, 0x30, 0x32, 0x57, 0x81, 0x20,
+				},
 			},
-			want:    "imei-",
-			wantErr: false,
+			wantErr: true,
+		},
+		{
+			name: "IMEI-TooShort",
+			args: args{
+				buf: []byte{
+					0x4b, 0x09, 0x51, 0x24, 0x30, 0x32,
+				},
+			},
+			wantErr: true,
 		},
 	}
 	for _, tt := range tests {