Verify entry output location when extracting zip

Closes gh-16028

Author: wilkinsona

spring-boot-cli/src/main/java/org/springframework/boot/cli/command/init/ProjectGenerator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -122,8 +122,17 @@ private void extractProject(ProjectGenerationResponse entity, String output,
 	private void extractFromStream(ZipInputStream zipStream, boolean overwrite,
 			File outputFolder) throws IOException {
 		ZipEntry entry = zipStream.getNextEntry();
+		String canonicalOutputPath = outputFolder.getCanonicalPath() + File.separator;
 		while (entry != null) {
 			File file = new File(outputFolder, entry.getName());
+			String canonicalEntryPath = file.getCanonicalPath();
+			if (!canonicalEntryPath.startsWith(canonicalOutputPath)) {
+				throw new ReportableException("Entry '" + entry.getName()
+						+ "' would be written to '" + canonicalEntryPath
+						+ "'. This is outside the output location of '"
+						+ canonicalOutputPath
+						+ "'. Verify your target server configuration.");
+			}
 			if (file.exists() && !overwrite) {
 				throw new ReportableException((file.isDirectory() ? "Directory" : "File")
 						+ " '" + file.getName()

spring-boot-cli/src/test/java/org/springframework/boot/cli/command/init/InitCommandTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2016 the original author or authors.
+ * Copyright 2012-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -125,6 +125,20 @@ public void generateProjectAndExtract() throws Exception {
 		assertThat(archiveFile).exists();
 	}
 
+	@Test
+	public void generateProjectAndExtractWillNotWriteEntriesOutsideOutputLocation()
+			throws Exception {
+		File folder = this.temporaryFolder.newFolder();
+		byte[] archive = createFakeZipArchive("../outside.txt", "Fake content");
+		MockHttpProjectGenerationRequest request = new MockHttpProjectGenerationRequest(
+				"application/zip", "demo.zip", archive);
+		mockSuccessfulProjectGeneration(request);
+		assertThat(this.command.run("--extract", folder.getAbsolutePath()))
+				.isEqualTo(ExitStatus.ERROR);
+		File archiveFile = new File(folder.getParentFile(), "outside.txt");
+		assertThat(archiveFile).doesNotExist();
+	}
+
 	@Test
 	public void generateProjectAndExtractWithConvention() throws Exception {
 		File folder = this.temporaryFolder.newFolder();