test: add unit tests for plugin payload attribute validation

signer/payload_test.go

@@ -0,0 +1,140 @@
+// Copyright The Notary Project Authors.
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package signer
+
+import (
+	"reflect"
+	"sort"
+	"testing"
+
+	"github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// baseDescriptor returns a descriptor that mirrors the subject a notation
+// client hands to a plugin for signing. Tests mutate copies of it to model a
+// plugin that tampers with the payload during the generate-envelope flow.
+func baseDescriptor() ocispec.Descriptor {
+	return ocispec.Descriptor{
+		MediaType: "application/vnd.oci.image.manifest.v1+json",
+		Digest:    digest.FromString("hello world"),
+		Size:      11,
+		Annotations: map[string]string{
+			"identity": "test.registry.io/test:example",
+		},
+	}
+}
+
+func TestIsPayloadDescriptorValid(t *testing.T) {
+	original := baseDescriptor()
+
+	mismatchedDigest := baseDescriptor()
+	mismatchedDigest.Digest = digest.FromString("tampered")
+
+	mismatchedSize := baseDescriptor()
+	mismatchedSize.Size = 22
+
+	mismatchedMediaType := baseDescriptor()
+	mismatchedMediaType.MediaType = "application/vnd.oci.image.index.v1+json"
+
+	// A plugin is allowed to append annotations but not replace existing ones.
+	overriddenAnnotation := baseDescriptor()
+	overriddenAnnotation.Annotations = map[string]string{
+		"identity": "attacker.registry.io/evil:latest",
+	}
+
+	addedAnnotation := baseDescriptor()
+	addedAnnotation.Annotations = map[string]string{
+		"identity": "test.registry.io/test:example",
+		"foo":      "bar",
+	}
+
+	tests := map[string]struct {
+		newDesc ocispec.Descriptor
+		want    bool
+	}{
+		"matching descriptor is valid": {
+			newDesc: baseDescriptor(),
+			want:    true,
+		},
+		"appended annotation is valid": {
+			newDesc: addedAnnotation,
+			want:    true,
+		},
+		"mismatched digest is rejected": {
+			newDesc: mismatchedDigest,
+			want:    false,
+		},
+		"mismatched size is rejected": {
+			newDesc: mismatchedSize,
+			want:    false,
+		},
+		"mismatched mediaType is rejected": {
+			newDesc: mismatchedMediaType,
+			want:    false,
+		},
+		"overridden annotation is rejected": {
+			newDesc: overriddenAnnotation,
+			want:    false,
+		},
+	}
+
+	for name, tc := range tests {
+		t.Run(name, func(t *testing.T) {
+			if got := isPayloadDescriptorValid(original, tc.newDesc); got != tc.want {
+				t.Fatalf("isPayloadDescriptorValid() = %v, want %v", got, tc.want)
+			}
+		})
+	}
+}
+
+func TestAreUnknownAttributesAdded(t *testing.T) {
+	tests := map[string]struct {
+		content string
+		want    []string
+	}{
+		"all known attributes are accepted": {
+			content: `{"targetArtifact":{"mediaType":"application/vnd.oci.image.manifest.v1+json","digest":"sha256:abc","size":11,"urls":["https://example.com"],"annotations":{"identity":"test.registry.io/test:example"},"data":"aGk=","platform":{"architecture":"amd64","os":"linux"},"artifactType":"application/example"}}`,
+			want:    []string{},
+		},
+		"unknown attribute inside descriptor is reported": {
+			content: `{"targetArtifact":{"mediaType":"application/vnd.oci.image.manifest.v1+json","digest":"sha256:abc","size":11,"injected":"value"}}`,
+			want:    []string{"injected"},
+		},
+		"reserved-style attribute inside descriptor is reported": {
+			content: `{"targetArtifact":{"digest":"sha256:abc","size":11,"$schema":"evil"}}`,
+			want:    []string{"$schema"},
+		},
+		"unknown attribute at payload top level is reported": {
+			content: `{"targetArtifact":{"digest":"sha256:abc","size":11},"extra":"value"}`,
+			want:    []string{"extra"},
+		},
+		"unknown attributes at both levels are reported": {
+			content: `{"targetArtifact":{"digest":"sha256:abc","size":11,"injected":"value"},"extra":"value"}`,
+			want:    []string{"extra", "injected"},
+		},
+	}
+
+	for name, tc := range tests {
+		t.Run(name, func(t *testing.T) {
+			got := areUnknownAttributesAdded([]byte(tc.content))
+			sort.Strings(got)
+			want := append([]string{}, tc.want...)
+			sort.Strings(want)
+			if !reflect.DeepEqual(got, want) {
+				t.Fatalf("areUnknownAttributesAdded() = %+q, want %+q", got, want)
+			}
+		})
+	}
+}