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

@@ -355,7 +355,7 @@ 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);
+			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 +243,17 @@ public Image pull(ImageReference reference, @Nullable ImagePlatform platform,
 						listener.onUpdate(event);
 					});
 				}
-				return inspect((platform != null) ? PLATFORM_API_VERSION : API_VERSION, reference);
+                if (platform != null) {
+                    if (getApiVersion().supports(INSPECT_PLATFORM_API_VERSION)) {
+                        return inspect(INSPECT_PLATFORM_API_VERSION, reference, platform);
+                    }
+					String digest = digestCapture.getDigest();
+					if (digest != null) {
+						ImageReference digestRef = reference.withDigest(digest);
+						return inspect(PLATFORM_API_VERSION, digestRef);
+					}
+                }
+                return inspect(API_VERSION, reference);
 			}
 			finally {
 				listener.onFinish();
@@ -311,9 +325,28 @@ 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) {
+				if (getApiVersion().supports(EXPORT_PLATFORM_API_VERSION)) {
+					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);
@@ -345,8 +378,15 @@ 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());
 			}
@@ -549,6 +589,10 @@ public void onUpdate(ProgressUpdateEvent event) {
 			}
 		}
 
+		private @Nullable String getDigest() {
+			return this.digest;
+		}
+
 	}
 
 	/**

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

@@ -239,7 +239,8 @@ 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(PLATFORM_IMAGES_URL
+					+ "/gcr.io/paketo-buildpacks/builder@sha256:4acb6bfd6c4f0cabaf7f3690e444afe51f1c7de54d51da7e63fac709c56f1c30/json");
 			given(http().head(eq(new URI(PING_URL))))
 				.willReturn(responseWithHeaders(new BasicHeader(DockerApi.API_VERSION_HEADER_NAME, "1.41")));
 			given(http().post(eq(createUri), isNull())).willReturn(responseOf("pull-stream.json"));