Add support for OCI Image Manifest

Image like s390x/ubuntu uses OCI Image Manifest, which per
https://github.com/opencontainers/image-spec/blob/v1.0.1/manifest.md
is very similar to vnd.docker.distribution.manifest.v2.

Add a test to confirm we can deserialize an OCI Image Manifest as a ManifestSchema2Spec.

Also add a test to confirm that we can now fetch the manifest from docker.io.
Previously it would fail with MANIFEST_UNKNOWN.

src/mediatypes.rs

@@ -32,6 +32,10 @@ pub enum MediaTypes {
     #[strum(serialize = "application/vnd.docker.container.image.v1+json")]
     #[strum(props(Sub = "vnd.docker.container.image.v1+json"))]
     ContainerConfigV1,
+    /// OCI Manifest
+    #[strum(serialize = "application/vnd.oci.image.manifest.v1+json")]
+    #[strum(props(Sub = "vnd.oci.image.manifest.v1+json"))]
+    OciImageManifest,
     /// Generic JSON
     #[strum(serialize = "application/json")]
     #[strum(props(Sub = "json"))]
@@ -55,6 +59,7 @@ impl MediaTypes {
                     }
                     ("vnd.docker.image.rootfs.diff.tar.gzip", _) => Ok(MediaTypes::ImageLayerTgz),
                     ("vnd.docker.container.image.v1", "json") => Ok(MediaTypes::ContainerConfigV1),
+                    ("vnd.oci.image.manifest.v1", "json") => Ok(MediaTypes::OciImageManifest),
                     _ => Err(crate::Error::UnknownMimeType(mtype.clone())),
                 }
             }

src/v2/config.rs

@@ -114,6 +114,7 @@ impl Config {
                     (MediaTypes::ManifestV2S2, Some(0.5)),
                     (MediaTypes::ManifestV2S1Signed, Some(0.4)),
                     (MediaTypes::ManifestList, Some(0.5)),
+                    (MediaTypes::OciImageManifest, Some(0.5)),
                 ],
                 // GCR incorrectly parses `q` parameters, so we use special Accept for it.
                 // Bug: https://issuetracker.google.com/issues/159827510.
@@ -122,6 +123,7 @@ impl Config {
                     (MediaTypes::ManifestV2S2, None),
                     (MediaTypes::ManifestV2S1Signed, None),
                     (MediaTypes::ManifestList, None),
+                    (MediaTypes::OciImageManifest, None),
                 ],
             },
         };

src/v2/manifest/mod.rs

@@ -78,7 +78,7 @@ impl Client {
                     .map(Manifest::S1Signed)?,
                 content_digest,
             )),
-            mediatypes::MediaTypes::ManifestV2S2 => {
+            mediatypes::MediaTypes::ManifestV2S2 | mediatypes::MediaTypes::OciImageManifest => {
                 let m = res.json::<ManifestSchema2Spec>().await?;
                 Ok((
                     m.fetch_config_blob(client_spare0, name.to_string())

tests/fixtures/manifest_oci_image_manifest.json

@@ -0,0 +1,16 @@
+{
+	"schemaVersion": 2,
+	"mediaType": "application/vnd.oci.image.manifest.v1+json",
+	"config": {
+		"mediaType": "application/vnd.oci.image.config.v1+json",
+		"size": 2297,
+		"digest": "sha256:7324f32f94760ec1dc237858203ea520fc4e6dfbd0bc018f392e54b1392ac722"
+	},
+	"layers": [
+		{
+			"mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
+			"size": 28028344,
+			"digest": "sha256:b2afc8f0dccbc5496c814ae03ac3fff7e86393abd18b2d2910a9c489bfe64311"
+		}
+	]
+}

tests/manifest.rs

@@ -69,6 +69,13 @@ fn test_manifest_v2s2() -> Result<(), Box<dyn std::error::Error>> {
     Ok(())
 }
 
+#[test]
+fn test_deserialize_oci_image_manifest() {
+    let f = fs::File::open("tests/fixtures/manifest_oci_image_manifest.json").expect("Missing fixture");
+    let bufrd = io::BufReader::new(f);
+    let _manif: dkregistry::v2::manifest::ManifestSchema2Spec = serde_json::from_reader(bufrd).unwrap();
+}
+
 #[test]
 fn test_deserialize_manifest_list_v2() {
     let f = fs::File::open("tests/fixtures/manifest_list_v2.json").expect("Missing fixture");

tests/net/docker_io/mod.rs

@@ -111,4 +111,29 @@ fn test_dockerio_anonymous_non_existent_image() {
     let res = runtime.block_on(futcheck);
     assert_eq!(res.is_ok(), false);
     assert!(matches!(res, Err(errors::Error::Api(_))));
-}
+}
+
+/// Test that we can deserialize OCI image manifest, as is
+/// returned for s390x/ubuntu image.
+#[test]
+fn test_dockerio_anonymous_auth_oci_manifest() {
+    let runtime = Runtime::new().unwrap();
+    let image = "s390x/ubuntu";
+    let version = "latest";
+    let login_scope = format!("repository:{}:pull", image);
+    let scopes = vec![login_scope.as_str()];
+    let dclient_future = dkregistry::v2::Client::configure()
+        .registry(REGISTRY)
+        .insecure_registry(false)
+        .username(None)
+        .password(None)
+        .build()
+        .unwrap()
+        .authenticate(scopes.as_slice());
+
+    let dclient = runtime.block_on(dclient_future).unwrap();
+    let futcheck = dclient.get_manifest(image, version);
+
+    let res = runtime.block_on(futcheck);
+    assert_eq!(res.is_ok(), true);
+}