Fix Docker multi-architecture image platform handling in buildpack operations

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/build/Builder.java

@@ -105,14 +105,22 @@ public void build(BuildRequest request) throws DockerEngineException, IOExceptio
 		Assert.notNull(request, "'request' must not be null");
 		this.log.start(request);
 		validateBindings(request.getBindings());
-		PullPolicy pullPolicy = request.getPullPolicy();
-		ImageFetcher imageFetcher = new ImageFetcher(this.dockerConfiguration.builderRegistryAuthentication(),
-				pullPolicy, request.getImagePlatform());
+        PullPolicy pullPolicy = request.getPullPolicy();
+        ImagePlatform requestedPlatform = request.getImagePlatform();
+        ImageFetcher imageFetcher = new ImageFetcher(this.dockerConfiguration.builderRegistryAuthentication(),
+                pullPolicy, requestedPlatform);
 		Image builderImage = imageFetcher.fetchImage(ImageType.BUILDER, request.getBuilder());
 		BuilderMetadata builderMetadata = BuilderMetadata.fromImage(builderImage);
 		request = withRunImageIfNeeded(request, builderMetadata);
-		Assert.state(request.getRunImage() != null, "'request.getRunImage()' must not be null");
-		Image runImage = imageFetcher.fetchImage(ImageType.RUNNER, request.getRunImage());
+        ImageReference imageReference = request.getRunImage();
+        Assert.state(imageReference != null, "'imageReference' must not be null");
+		Image runImage = imageFetcher.fetchImage(ImageType.RUNNER, imageReference);
+		String digest = this.docker.image().resolveManifestDigest(imageReference, requestedPlatform);
+		if (StringUtils.hasText(digest)) {
+			imageReference = imageReference.withDigest(digest);
+			runImage = imageFetcher.fetchImage(ImageType.RUNNER, imageReference);
+		}
+        request = request.withRunImage(imageReference);
 		assertStackIdsMatch(runImage, builderImage);
 		BuildOwner buildOwner = BuildOwner.fromEnv(builderImage.getConfig().getEnv());
 		BuildpackLayersMetadata buildpackLayersMetadata = BuildpackLayersMetadata.fromImage(builderImage);
@@ -355,8 +363,16 @@ public Image fetchImage(ImageReference reference, ImageType imageType) throws IO
 		@Override
 		public void exportImageLayers(ImageReference reference, IOBiConsumer<String, TarArchive> exports)
 				throws IOException {
-			Builder.this.docker.image().exportLayers(reference, exports);
-		}
+			String digest = Builder.this.docker.image().resolveManifestDigest(reference,
+					this.imageFetcher.defaultPlatform);
+			if (StringUtils.hasText(digest)) {
+				ImageReference pinned = reference.withDigest(digest);
+				Builder.this.docker.image().exportLayers(pinned, null, exports);
+			}
+			else {
+				Builder.this.docker.image().exportLayers(reference, this.imageFetcher.defaultPlatform, exports);
+			}
+        }
 
 	}
 

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/DockerApi.java

@@ -68,6 +68,10 @@ public class DockerApi {
 
 	static final ApiVersion PLATFORM_API_VERSION = ApiVersion.of(1, 41);
 
+	static final ApiVersion EXPORT_PLATFORM_API_VERSION = ApiVersion.of(1, 48);
+
+    static final ApiVersion INSPECT_PLATFORM_API_VERSION = ApiVersion.of(1, 49);
+
 	static final ApiVersion UNKNOWN_API_VERSION = ApiVersion.of(0, 0);
 
 	static final String API_VERSION_HEADER_NAME = "API-Version";
@@ -239,7 +243,10 @@ public Image pull(ImageReference reference, @Nullable ImagePlatform platform,
 						listener.onUpdate(event);
 					});
 				}
-				return inspect((platform != null) ? PLATFORM_API_VERSION : API_VERSION, reference);
+				if (platform != null) {
+					return inspect(INSPECT_PLATFORM_API_VERSION, reference, platform);
+				}
+                return inspect(API_VERSION, reference);
 			}
 			finally {
 				listener.onFinish();
@@ -311,16 +318,59 @@ public void load(ImageArchive archive, UpdateListener<LoadImageUpdateEvent> list
 		 */
 		public void exportLayers(ImageReference reference, IOBiConsumer<String, TarArchive> exports)
 				throws IOException {
+			exportLayers(reference, null, exports);
+		}
+
+		/**
+		 * Export the layers of an image as {@link TarArchive TarArchives}.
+		 * @param reference the reference to export
+		 * @param platform the platform (os/architecture/variant) of the image to export
+		 * @param exports a consumer to receive the layers (contents can only be accessed
+		 * during the callback)
+		 * @throws IOException on IO error
+		 */
+		public void exportLayers(ImageReference reference, @Nullable ImagePlatform platform,
+				IOBiConsumer<String, TarArchive> exports) throws IOException {
 			Assert.notNull(reference, "'reference' must not be null");
 			Assert.notNull(exports, "'exports' must not be null");
 			URI uri = buildUrl("/images/" + reference + "/get");
+			if (platform != null) {
+				uri = buildUrl(EXPORT_PLATFORM_API_VERSION, "/images/" + reference + "/get", "platform",
+						platform.toJson());
+			}
 			try (Response response = http().get(uri)) {
 				try (ExportedImageTar exportedImageTar = new ExportedImageTar(reference, response.getContent())) {
 					exportedImageTar.exportLayers(exports);
 				}
 			}
 		}
 
+        /**
+         * Resolve an image manifest digest via Docker inspect.
+         * If {@code platform} is provided, performs a platform-aware inspect.
+         * Preference order: {@code Descriptor.digest} then first {@code RepoDigest}.
+         * Returns an empty string if no digest can be determined.
+         * @param reference image reference
+         * @param platform desired platform
+         * @return resolved digest or empty string
+         * @throws IOException on IO error
+         */
+		public String resolveManifestDigest(ImageReference reference, @Nullable ImagePlatform platform)
+				throws IOException {
+			Assert.notNull(reference, "'reference' must not be null");
+			Image image = inspect(API_VERSION, reference);
+			if (platform != null) {
+				 image = inspect(INSPECT_PLATFORM_API_VERSION, reference, platform);
+			}
+            Image.Descriptor descriptor = image.getDescriptor();
+            if (descriptor != null && StringUtils.hasText(descriptor.getDigest())) {
+                return descriptor.getDigest();
+            }
+            List<String> repoDigests = image.getDigests();
+			String digest = repoDigests.isEmpty() ? "" : repoDigests.get(0);
+			return digest.substring(digest.indexOf('@') + 1);
+		}
+
 		/**
 		 * Remove a specific image.
 		 * @param reference the reference the remove
@@ -345,8 +395,15 @@ public Image inspect(ImageReference reference) throws IOException {
 		}
 
 		private Image inspect(ApiVersion apiVersion, ImageReference reference) throws IOException {
+			return inspect(apiVersion, reference, null);
+		}
+
+		private Image inspect(ApiVersion apiVersion, ImageReference reference, @Nullable ImagePlatform platform)
+				throws IOException {
 			Assert.notNull(reference, "'reference' must not be null");
-			URI imageUri = buildUrl(apiVersion, "/images/" + reference + "/json");
+            URI imageUri = (platform != null)
+                    ? buildUrl(apiVersion, "/images/" + reference + "/json", "platform", platform.toJson())
+                    : buildUrl(apiVersion, "/images/" + reference + "/json");
 			try (Response response = http().get(imageUri)) {
 				return Image.of(response.getContent());
 			}

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/type/Image.java

@@ -22,6 +22,7 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 
 import org.jspecify.annotations.Nullable;
 import tools.jackson.databind.JsonNode;
@@ -52,6 +53,8 @@ public class Image extends MappedObject {
 
 	private final @Nullable String created;
 
+    private final @Nullable Descriptor descriptor;
+
 	Image(JsonNode node) {
 		super(node, MethodHandles.lookup());
 		this.digests = childrenAt("/RepoDigests", JsonNode::asString);
@@ -61,6 +64,8 @@ public class Image extends MappedObject {
 		this.architecture = valueAt("/Architecture", String.class);
 		this.variant = valueAt("/Variant", String.class);
 		this.created = valueAt("/Created", String.class);
+		JsonNode descriptorNode = getNode().path("Descriptor");
+		this.descriptor = (descriptorNode.isMissingNode() || descriptorNode.isNull()) ? null : new Descriptor(descriptorNode);
 	}
 
 	private List<LayerId> extractLayers(String @Nullable [] layers) {
@@ -126,6 +131,46 @@ public String getOs() {
 		return this.created;
 	}
 
+	/**
+	 * Return the descriptor for this image as reported by Docker Engine inspect.
+	 * @return the image descriptor or {@code null}
+	 */
+	public @Nullable Descriptor getDescriptor() {
+		return this.descriptor;
+	}
+
+	/**
+	 * Descriptor details as reported by the Docker Engine inspect response.
+	 */
+    public static final class Descriptor extends MappedObject {
+
+        private final @Nullable String mediaType;
+
+        private final String digest;
+
+        private final @Nullable Long size;
+
+        Descriptor(JsonNode node) {
+            super(node, MethodHandles.lookup());
+            this.mediaType = valueAt("/mediaType", String.class);
+            this.digest = Objects.requireNonNull(valueAt("/digest", String.class));
+            this.size = valueAt("/size", Long.class);
+        }
+
+        public @Nullable String getMediaType() {
+            return this.mediaType;
+        }
+
+        public String getDigest() {
+            return this.digest;
+        }
+
+        public @Nullable Long getSize() {
+            return this.size;
+        }
+
+	}
+
 	/**
 	 * Create a new {@link Image} instance from the specified JSON content.
 	 * @param content the JSON content

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/type/ImagePlatform.java

@@ -101,4 +101,22 @@ public static ImagePlatform from(Image image) {
 		return new ImagePlatform(image.getOs(), image.getArchitecture(), image.getVariant());
 	}
 
+	/**
+	 * Return a JSON-encoded representation of this platform for use with Docker Engine
+	 * API 1.48+ endpoints that require the platform parameter in JSON format
+	 * (e.g., image inspect and export operations).
+	 * @return a JSON object in the form {@code {"os":"...","architecture":"...","variant":"..."}}
+	 */
+	public String toJson() {
+		StringBuilder json = new StringBuilder("{");
+		json.append("\"os\":\"").append(this.os).append("\"");
+		if (this.architecture != null && !this.architecture.isEmpty()) {
+			json.append(",\"architecture\":\"").append(this.architecture).append("\"");
+		}
+		if (this.variant != null && !this.variant.isEmpty()) {
+			json.append(",\"variant\":\"").append(this.variant).append("\"");
+		}
+		json.append("}");
+		return json.toString();
+	}
 }

buildpack/spring-boot-buildpack-platform/src/test/java/org/springframework/boot/buildpack/platform/docker/DockerApiTests.java

@@ -91,12 +91,16 @@ class DockerApiTests {
 
 	private static final String PLATFORM_API_URL = "/v" + DockerApi.PLATFORM_API_VERSION;
 
+	private static final String INSPECT_PLATFORM_API_URL = "/v" + DockerApi.INSPECT_PLATFORM_API_VERSION;
+
 	public static final String PING_URL = "/_ping";
 
 	private static final String IMAGES_URL = API_URL + "/images";
 
 	private static final String PLATFORM_IMAGES_URL = PLATFORM_API_URL + "/images";
 
+	private static final String INSPECT_PLATFORM_IMAGES_URL = INSPECT_PLATFORM_API_URL + "/images";
+
 	private static final String CONTAINERS_URL = API_URL + "/containers";
 
 	private static final String PLATFORM_CONTAINERS_URL = PLATFORM_API_URL + "/containers";
@@ -239,9 +243,10 @@ void pullWithPlatformPullsImageAndProducesEvents() throws Exception {
 			ImagePlatform platform = ImagePlatform.of("linux/arm64/v1");
 			URI createUri = new URI(PLATFORM_IMAGES_URL
 					+ "/create?fromImage=gcr.io%2Fpaketo-buildpacks%2Fbuilder%3Abase&platform=linux%2Farm64%2Fv1");
-			URI imageUri = new URI(PLATFORM_IMAGES_URL + "/gcr.io/paketo-buildpacks/builder:base/json");
+			URI imageUri = new URI(INSPECT_PLATFORM_IMAGES_URL
+					+ "/gcr.io/paketo-buildpacks/builder:base/json?platform=%7B%22os%22%3A%22linux%22%2C%22architecture%22%3A%22arm64%22%2C%22variant%22%3A%22v1%22%7D");
 			given(http().head(eq(new URI(PING_URL))))
-				.willReturn(responseWithHeaders(new BasicHeader(DockerApi.API_VERSION_HEADER_NAME, "1.41")));
+				.willReturn(responseWithHeaders(new BasicHeader(DockerApi.API_VERSION_HEADER_NAME, "1.49")));
 			given(http().post(eq(createUri), isNull())).willReturn(responseOf("pull-stream.json"));
 			given(http().get(imageUri)).willReturn(responseOf("type/image.json"));
 			Image image = this.api.pull(reference, platform, this.pullListener);