Refuse compression to zstd when using schema1

manifest/docker_schema1.go

@@ -10,6 +10,7 @@ import (
 	"github.com/containers/image/v5/docker/reference"
 	"github.com/containers/image/v5/internal/manifest"
 	"github.com/containers/image/v5/internal/set"
+	compressiontypes "github.com/containers/image/v5/pkg/compression/types"
 	"github.com/containers/image/v5/types"
 	"github.com/containers/storage/pkg/regexp"
 	"github.com/docker/docker/api/types/versions"
@@ -142,6 +143,15 @@ func (m *Schema1) LayerInfos() []LayerInfo {
 	return layers
 }
 
+const fakeSchema1MIMEType = DockerV2Schema2LayerMediaType // Used only in schema1CompressionMIMETypeSets
+var schema1CompressionMIMETypeSets = []compressionMIMETypeSet{
+	{
+		mtsUncompressed:                    fakeSchema1MIMEType,
+		compressiontypes.GzipAlgorithmName: fakeSchema1MIMEType,
+		compressiontypes.ZstdAlgorithmName: mtsUnsupportedMIMEType,
+	},
+}
+
 // UpdateLayerInfos replaces the original layers with the specified BlobInfos (size+digest+urls), in order (the root layer first, and then successive layered layers)
 func (m *Schema1) UpdateLayerInfos(layerInfos []types.BlobInfo) error {
 	// Our LayerInfos includes empty layers (where m.ExtractedV1Compatibility[].ThrowAway), so expect them to be included here as well.
@@ -150,6 +160,11 @@ func (m *Schema1) UpdateLayerInfos(layerInfos []types.BlobInfo) error {
 	}
 	m.FSLayers = make([]Schema1FSLayers, len(layerInfos))
 	for i, info := range layerInfos {
+		// There are no MIME types in schema1, but we do a “conversion” here to reject unsupported compression algorithms,
+		// in a way that is consistent with the other schema implementations.
+		if _, err := updatedMIMEType(schema1CompressionMIMETypeSets, fakeSchema1MIMEType, info); err != nil {
+			return fmt.Errorf("preparing updated manifest, layer %q: %w", info.Digest, err)
+		}
 		// (docker push) sets up m.ExtractedV1Compatibility[].{Id,Parent} based on values of info.Digest,
 		// but (docker pull) ignores them in favor of computing DiffIDs from uncompressed data, except verifying the child->parent links and uniqueness.
 		// So, we don't bother recomputing the IDs in m.History.V1Compatibility.

manifest/docker_schema1_test.go

@@ -1,6 +1,7 @@
 package manifest
 
 import (
+	"encoding/json"
 	"os"
 	"path/filepath"
 	"testing"
@@ -22,6 +23,26 @@ var schema1FixtureLayerDiffIDs = []digest.Digest{
 	"sha256:8c064bb1f60e84fa8cc6079b6d2e76e0423389fd6aeb7e497dfdae5e05b2b25b",
 }
 
+// assertJSONEqualsFixture tests that jsonBytes is structurally equal to fixture,
+// possibly ignoring ignoreFields
+func assertJSONEqualsFixture(t *testing.T, jsonBytes []byte, fixture string, ignoreFields ...string) {
+	var contents map[string]any
+	err := json.Unmarshal(jsonBytes, &contents)
+	require.NoError(t, err)
+
+	fixtureBytes, err := os.ReadFile(filepath.Join("fixtures", fixture))
+	require.NoError(t, err)
+	var fixtureContents map[string]any
+
+	err = json.Unmarshal(fixtureBytes, &fixtureContents)
+	require.NoError(t, err)
+	for _, f := range ignoreFields {
+		delete(contents, f)
+		delete(fixtureContents, f)
+	}
+	assert.Equal(t, fixtureContents, contents)
+}
+
 func manifestSchema1FromFixture(t *testing.T, fixture string) *Schema1 {
 	manifest, err := os.ReadFile(filepath.Join("fixtures", fixture))
 	require.NoError(t, err)
@@ -185,7 +206,78 @@ func TestSchema1UpdateLayerInfos(t *testing.T) {
 		updates         []types.BlobInfo
 		expectedFixture string // or "" to indicate an expected failure
 	}{
-		// Many more tests cases could be added here
+		{
+			name:          "gzip → uncompressed",
+			sourceFixture: "v2s1.manifest.json",
+			updates: []types.BlobInfo{
+				{
+					Digest:               "sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef",
+					Size:                 32654,
+					CompressionOperation: types.Decompress,
+				},
+				{
+					Digest:               "sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef",
+					Size:                 16724,
+					CompressionOperation: types.Decompress,
+				},
+				{
+					Digest:               "sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef",
+					Size:                 73109,
+					CompressionOperation: types.Decompress,
+				},
+			},
+			expectedFixture: "v2s1.manifest.json", // MIME type is not stored, and we didn’t change the digests in this test, so we should not see any changes.
+		},
+		{
+			name:          "uncompressed → gzip",
+			sourceFixture: "v2s1.manifest.json",
+			updates: []types.BlobInfo{
+				{
+					Digest:               "sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef",
+					Size:                 32654,
+					CompressionOperation: types.Compress,
+					CompressionAlgorithm: &compression.Gzip,
+				},
+				{
+					Digest:               "sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef",
+					Size:                 16724,
+					CompressionOperation: types.Compress,
+					CompressionAlgorithm: &compression.Gzip,
+				},
+				{
+					Digest:               "sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef",
+					Size:                 73109,
+					CompressionOperation: types.Compress,
+					CompressionAlgorithm: &compression.Gzip,
+				},
+			},
+			expectedFixture: "v2s1.manifest.json", // MIME type is not stored, and we didn’t change the digests in this test, so we should not see any changes.
+		},
+		{
+			name:          "gzip → zstd",
+			sourceFixture: "v2s1.manifest.json",
+			updates: []types.BlobInfo{
+				{
+					Digest:               "sha256:e692418e4cbaf90ca69d05a66403747baa33ee08806650b51fab815ad7fc331f",
+					Size:                 32654,
+					CompressionOperation: types.Compress,
+					CompressionAlgorithm: &compression.Zstd,
+				},
+				{
+					Digest:               "sha256:3c3a4604a545cdc127456d94e421cd355bca5b528f4a9c1905b15da2eb4a4c6b",
+					Size:                 16724,
+					CompressionOperation: types.Compress,
+					CompressionAlgorithm: &compression.Zstd,
+				},
+				{
+					Digest:               "sha256:ec4b8955958665577945c89419d1af06b5f7636b4ac3da7f12184802ad867736",
+					Size:                 73109,
+					CompressionOperation: types.Compress,
+					CompressionAlgorithm: &compression.Zstd,
+				},
+			},
+			expectedFixture: "", // zstd is not supported for docker images
+		},
 		{
 			name:          "uncompressed → gzip encrypted",
 			sourceFixture: "v2s1.manifest.json",
@@ -254,11 +346,8 @@ func TestSchema1UpdateLayerInfos(t *testing.T) {
 			updatedManifestBytes, err := manifest.Serialize()
 			require.NoError(t, err, c.name)
 
-			expectedManifest := manifestSchema1FromFixture(t, c.expectedFixture)
-			expectedManifestBytes, err := expectedManifest.Serialize()
-			require.NoError(t, err, c.name)
-
-			assert.Equal(t, string(expectedManifestBytes), string(updatedManifestBytes), c.name)
+			// Drop "signatures" which is generated by AddDummyV2S1Signature
+			assertJSONEqualsFixture(t, updatedManifestBytes, c.expectedFixture, "signatures")
 		}
 	}
 }