fix: Empty string defers to SDK default region

ComAmazonawsKms/runtimes/java/src/main/java/software/amazon/cryptography/services/kms/internaldafny/__default.java

@@ -53,9 +53,15 @@ public static Result<IKMSClient, Error> KMSClientForRegion(
     final DafnySequence<? extends Character> region
   ) {
     try {
-      final String regionString = new String(
-        (char[]) region.toArray().unwrap()
-      );
+      final char[] inputRegion = (char[]) region.toArray().unwrap();
+      // The ESDK uses empty string as a kind of none.
+      // In the case of an AWS KMS raw key identifier there is no region element
+      // an so "" is used in this case.
+      if (inputRegion.length == 0) {
+        return KMSClient();
+      }
+
+      final String regionString = new String(inputRegion);
       final KmsClientBuilder builder = KmsClient.builder();
       final KmsClient client = builder
         .region(Region.of(regionString))

ComAmazonawsKms/runtimes/net/Extern/KMSClient.cs

@@ -39,6 +39,10 @@ Dafny.ISequence<char> regionDafnyString
           )
         {
             string regionStr = TypeConversion.FromDafny_N6_smithy__N3_api__S6_String(regionDafnyString);
+            // The ESDK uses empty string as a kind of none.
+            // In the case of an AWS KMS raw key identifier there is no region element
+            // an so "" is used in this case.
+            if (regionStr == "") return KMSClient();
             var region = RegionEndpoint.GetBySystemName(regionStr);
             var client = new DefaultKmsClient(region);
 

ComAmazonawsKms/test/TestComAmazonawsKms.dfy

@@ -85,7 +85,7 @@ module TestComAmazonawsKms {
     nameonly expectedKeyId: Kms.Types.KeyIdType
   )
   {
-    var client :- expect Kms.KMSClient();
+    var client :- expect Kms.KMSClientForRegion(TEST_REGION);
 
     var ret := client.Decrypt(input);
 
@@ -106,7 +106,7 @@ module TestComAmazonawsKms {
   )
     requires input.NumberOfBytes.Some?
   {
-    var client :- expect Kms.KMSClient();
+    var client :- expect Kms.KMSClientForRegion(TEST_REGION);
 
     var ret := client.GenerateDataKey(input);
 
@@ -138,7 +138,7 @@ module TestComAmazonawsKms {
     nameonly input: Kms.Types.EncryptRequest
   )
   {
-    var client :- expect Kms.KMSClient();
+    var client :- expect Kms.KMSClientForRegion(TEST_REGION);
 
     var ret := client.Encrypt(input);
 
@@ -167,9 +167,14 @@ module TestComAmazonawsKms {
   // While we cannot easily test that the expected implementations
   // return Some(), we can at least ensure that the ones that do are correct.
   method {:test} RegionMatchTest() {
-    var client :- expect Kms.KMSClient();
+    var client :- expect Kms.KMSClientForRegion(TEST_REGION);
     var region := Kms.RegionMatch(client, TEST_REGION);
     expect region.None? || region.value;
   }
 
+  // This should default to whatever default SDK uses.
+  method {:test} EmptyStringIsDefaultRegion() {
+    var client :- expect Kms.KMSClientForRegion("");
+  }
+
 }