localstack · MEPalma · Jun 3, 2025 · May 19, 2025 · May 20, 2025 · May 21, 2025
@@ -426,6 +426,7 @@ def __init__(self, scope: Scope, value: Any):
 FnSelect: Final[str] = "Fn::Select"
 FnSplit: Final[str] = "Fn::Split"
 FnGetAZs: Final[str] = "Fn::GetAZs"
+FnBase64: Final[str] = "Fn::Base64"
 INTRINSIC_FUNCTIONS: Final[set[str]] = {
     RefKey,
     FnIfKey,
@@ -439,6 +440,7 @@ def __init__(self, scope: Scope, value: Any):
     FnSelect,
     FnSplit,
     FnGetAZs,
+    FnBase64,
 }
 
 

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import base64
 import re
 from typing import Any, Final, Generic, Optional, TypeVar
 
@@ -45,6 +46,8 @@
 from localstack.services.cloudformation.stores import get_cloudformation_store
 from localstack.services.cloudformation.v2.entities import ChangeSet
 from localstack.utils.aws.arns import get_partition
+from localstack.utils.run import to_str
+from localstack.utils.strings import to_bytes
 from localstack.utils.urls import localstack_host
 
 _AWS_URL_SUFFIX = localstack_host().host  # The value in AWS is "amazonaws.com"
@@ -748,6 +751,31 @@ def _compute_fn_get_a_zs(region) -> Any:
 
         return PreprocEntityDelta(before=before, after=after)
 
+    def visit_node_intrinsic_function_fn_base64(
+        self, node_intrinsic_function: NodeIntrinsicFunction
+    ) -> PreprocEntityDelta:
+        # TODO: add further support for schema validation
+        arguments_delta = self.visit(node_intrinsic_function.arguments)
+        arguments_before = arguments_delta.before
+        arguments_after = arguments_delta.after
+
+        def _compute_fn_base_64(string) -> Any:
+            if not isinstance(string, str):
+                raise RuntimeError(f"Invalid valueToEncode for Fn::Base64: '{string}'")
+            # Ported from v1:
+            base64_string = to_str(base64.b64encode(to_bytes(string)))
+            return base64_string
+
+        before = Nothing
+        if not is_nothing(arguments_before):
+            before = _compute_fn_base_64(arguments_before)
+
+        after = Nothing
+        if not is_nothing(arguments_after):
+            after = _compute_fn_base_64(arguments_after)
+
+        return PreprocEntityDelta(before=before, after=after)
+
     def visit_node_intrinsic_function_fn_find_in_map(
         self, node_intrinsic_function: NodeIntrinsicFunction
     ) -> PreprocEntityDelta:

@@ -133,6 +133,11 @@ def visit_node_intrinsic_function_fn_get_a_zs(
     ):
         self.visit_children(node_intrinsic_function)
 
+    def visit_node_intrinsic_function_fn_base64(
+        self, node_intrinsic_function: NodeIntrinsicFunction
+    ):
+        self.visit_children(node_intrinsic_function)
+
     def visit_node_intrinsic_function_fn_sub(self, node_intrinsic_function: NodeIntrinsicFunction):
         self.visit_children(node_intrinsic_function)
 

@@ -109,7 +109,6 @@ def test_and_or_functions(
         bucket_names = [b["Name"] for b in buckets["Buckets"]]
         assert (bucket_name in bucket_names) == expected_bucket_created
 
-    @pytest.mark.skip(reason="CFNV2:Fn::Base64")
     @markers.aws.validated
     def test_base64_sub_and_getatt_functions(self, deploy_cfn_template):
         template_path = os.path.join(

@@ -0,0 +1,97 @@
+import pytest
+from localstack_snapshot.snapshots.transformer import RegexTransformer
+
+from localstack.services.cloudformation.v2.utils import is_v2_engine
+from localstack.testing.aws.util import is_aws_cloud
+from localstack.testing.pytest import markers
+from localstack.utils.strings import long_uid
+
+
+@pytest.mark.skipif(
+    condition=not is_v2_engine() and not is_aws_cloud(), reason="Requires the V2 engine"
+)
+@markers.snapshot.skip_snapshot_verify(
+    paths=[
+        "per-resource-events..*",
+        "delete-describe..*",
+        #
+        # Before/After Context
+        "$..Capabilities",
+        "$..NotificationARNs",
+        "$..IncludeNestedStacks",
+        "$..Scope",
+        "$..Details",
+        "$..Parameters",
+        "$..Replacement",
+    ]
+)
+class TestChangeSetFnBase64:
+    @markers.aws.validated
+    def test_fn_base64_add_to_static_property(
+        self,
+        snapshot,
+        capture_update_process,
+    ):
+        name1 = f"topic-name-1-{long_uid()}"
+        snapshot.add_transformer(RegexTransformer(name1, "topic-name-1"))
+        template_1 = {
+            "Resources": {
+                "Topic1": {"Type": "AWS::SNS::Topic", "Properties": {"DisplayName": name1}}
+            }
+        }
+        template_2 = {
+            "Resources": {
+                "Topic1": {
+                    "Type": "AWS::SNS::Topic",
+                    "Properties": {"DisplayName": {"Fn::Base64": "HelloWorld"}},
+                }
+            }
+        }
+        capture_update_process(snapshot, template_1, template_2)
+
+    @markers.aws.validated
+    def test_fn_base64_remove_from_static_property(
+        self,
+        snapshot,
+        capture_update_process,
+    ):
+        name1 = f"topic-name-1-{long_uid()}"
+        snapshot.add_transformer(RegexTransformer(name1, "topic-name-1"))
+        template_1 = {
+            "Resources": {
+                "Topic1": {
+                    "Type": "AWS::SNS::Topic",
+                    "Properties": {"DisplayName": {"Fn::Base64": "HelloWorld"}},
+                }
+            }
+        }
+        template_2 = {
+            "Resources": {
+                "Topic1": {"Type": "AWS::SNS::Topic", "Properties": {"DisplayName": name1}}
+            }
+        }
+        capture_update_process(snapshot, template_1, template_2)
+
+    @markers.aws.validated
+    def test_fn_base64_change_input_string(
+        self,
+        snapshot,
+        capture_update_process,
+    ):
+        template_1 = {
+            "Resources": {
+                "Topic1": {
+                    "Type": "AWS::SNS::Topic",
+                    "Properties": {"DisplayName": {"Fn::Base64": "OldValue"}},
+                }
+            }
+        }
+        template_2 = {
+            "Resources": {
+                "Topic1": {
+                    "Type": "AWS::SNS::Topic",
+                    "Properties": {"DisplayName": {"Fn::Base64": "NewValue"}},
+                }
+            }
+        }
+        capture_update_process(snapshot, template_1, template_2)