Disallow empty country code in negative reports

src/negative_report.rs

@@ -12,6 +12,7 @@ pub enum NegativeReportError {
     DateInFuture,
     FailedToDeserialize, // couldn't deserialize to SerializableNegativeReport
     InvalidCountryCode,
+    MissingCountryCode,
 }
 
 /// A report that the user was unable to connect to the bridge
@@ -20,7 +21,7 @@ pub struct NegativeReport {
     pub fingerprint: [u8; 20],
     /// some way to prove knowledge of bridge
     bridge_pok: ProofOfBridgeKnowledge,
-    /// user's country code, may be an empty string
+    /// user's country code
     pub country: String,
     /// today's Julian date
     pub date: u32,
@@ -116,7 +117,10 @@ pub struct SerializableNegativeReport {
 
 impl SerializableNegativeReport {
     pub fn to_report(self) -> Result<NegativeReport, NegativeReportError> {
-        if self.country != "" && !COUNTRY_CODES.contains(self.country.as_str()) {
+        if self.country == "" {
+            return Err(NegativeReportError::MissingCountryCode);
+        }
+        if !COUNTRY_CODES.contains(self.country.as_str()) {
             return Err(NegativeReportError::InvalidCountryCode);
         }
         if self.date > get_date().into() {