fix(security): add archive extraction containment validation

Validate tar and zip entries before extraction to prevent path traversal: - Reject absolute paths in archives - Reject .. traversal paths - Reject symlinks pointing outside extraction dir - New archive-entry-validator module with comprehensive tests Addresses: security audit finding for unsafe archive extraction.
2026-04-02 15:01:15 +09:00
parent a637cca702
commit d861d51959
5 changed files with 454 additions and 0 deletions
@@ -0,0 +1,184 @@
+/// <reference types="bun-types" />
+
+import { afterEach, describe, expect, it } from "bun:test"
+import { lstatSync, mkdirSync, mkdtempSync, readFileSync, rmSync, symlinkSync, writeFileSync } from "node:fs"
+import { tmpdir } from "node:os"
+import { join } from "node:path"
+import { spawnSync } from "bun"
+
+import { extractTarGz } from "./binary-downloader"
+import { validateArchiveEntries } from "./archive-entry-validator"
+import { extractZip } from "./zip-extractor"
+
+const testDirs: string[] = []
+
+function createTestDir(): string {
+	const dir = mkdtempSync(join(tmpdir(), "archive-entry-validator-"))
+	testDirs.push(dir)
+	return dir
+}
+
+function runCommand(command: string, cwd?: string): void {
+	const result = spawnSync(["bash", "-lc", command], { cwd, stderr: "pipe", stdout: "pipe" })
+	if (result.exitCode !== 0) {
+		throw new Error(result.stderr.toString())
+	}
+}
+
+function writePythonScript(dir: string, filename: string, content: string): string {
+	const scriptPath = join(dir, filename)
+	writeFileSync(scriptPath, content)
+	return scriptPath
+}
+
+afterEach(() => {
+	for (const dir of testDirs.splice(0)) {
+		rmSync(dir, { recursive: true, force: true })
+	}
+})
+
+describe("validateArchiveEntries", () => {
+	it("rejects absolute paths and traversal entries", () => {
+		//#given
+		const destDir = "/tmp/archive-root"
+
+		//#when
+		const rejectAbsolutePath = () =>
+			validateArchiveEntries([{ path: "/etc/passwd", type: "file" }], destDir)
+		const rejectTraversalPath = () =>
+			validateArchiveEntries([{ path: "nested/../../evil.txt", type: "file" }], destDir)
+
+		//#then
+		expect(rejectAbsolutePath).toThrow(/absolute path/i)
+		expect(rejectTraversalPath).toThrow(/path traversal/i)
+	})
+
+	it("rejects symlink targets that escape the extraction directory", () => {
+		//#given
+		const destDir = "/tmp/archive-root"
+
+		//#when
+		const rejectEscapeSymlink = () =>
+			validateArchiveEntries(
+				[{ path: "bin/tool", type: "symlink", linkPath: "../../outside/tool" }],
+				destDir
+			)
+
+		//#then
+		expect(rejectEscapeSymlink).toThrow(/symlink target/i)
+	})
+
+	it("accepts contained files, directories, and symlinks", () => {
+		//#given
+		const destDir = "/tmp/archive-root"
+		const entries = [
+			{ path: "bin/", type: "directory" as const },
+			{ path: "bin/tool", type: "file" as const },
+			{ path: "bin/tool-link", type: "symlink" as const, linkPath: "tool" },
+		]
+
+		//#when
+		const validateContainedEntries = () => validateArchiveEntries(entries, destDir)
+
+		//#then
+		expect(validateContainedEntries).not.toThrow()
+	})
+})
+
+describe("archive extraction preflight", () => {
+	it("rejects tar archives with traversal entries before extraction", async () => {
+		//#given
+		const rootDir = createTestDir()
+		const archivePath = join(rootDir, "malicious.tar.gz")
+		const destDir = join(rootDir, "dest")
+		mkdirSync(destDir, { recursive: true })
+		const scriptPath = writePythonScript(
+			rootDir,
+			"make-malicious-tar.py",
+			[
+				"import io",
+				"import sys",
+				"import tarfile",
+				"with tarfile.open(sys.argv[1], 'w:gz') as archive:",
+				"    data = b'owned'",
+				"    info = tarfile.TarInfo('../escape.txt')",
+				"    info.size = len(data)",
+				"    archive.addfile(info, io.BytesIO(data))",
+			].join("\n")
+		)
+		runCommand(`python3 "${scriptPath}" "${archivePath}"`)
+
+		//#when
+		let errorMessage = ""
+		try {
+			await extractTarGz(archivePath, destDir)
+		} catch (error) {
+			errorMessage = error instanceof Error ? error.message : String(error)
+		}
+
+		//#then
+		expect(errorMessage).toMatch(/path traversal/i)
+	})
+
+	it("rejects zip archives with symlink escapes before extraction", async () => {
+		//#given
+		const rootDir = createTestDir()
+		const archivePath = join(rootDir, "malicious.zip")
+		const destDir = join(rootDir, "dest")
+		mkdirSync(destDir, { recursive: true })
+		const scriptPath = writePythonScript(
+			rootDir,
+			"make-malicious-zip.py",
+			[
+				"import stat",
+				"import sys",
+				"import zipfile",
+				"archive = zipfile.ZipFile(sys.argv[1], 'w')",
+				"entry = zipfile.ZipInfo('bin/tool-link')",
+				"entry.create_system = 3",
+				"entry.external_attr = (stat.S_IFLNK | 0o777) << 16",
+				"archive.writestr(entry, '../../escape.txt')",
+				"archive.close()",
+			].join("\n")
+		)
+		runCommand(`python3 "${scriptPath}" "${archivePath}"`)
+
+		//#when
+		let errorMessage = ""
+		try {
+			await extractZip(archivePath, destDir)
+		} catch (error) {
+			errorMessage = error instanceof Error ? error.message : String(error)
+		}
+
+		//#then
+		expect(errorMessage).toMatch(/symlink target/i)
+	})
+
+	it("extracts safe tar and zip archives into the destination directory", async () => {
+		//#given
+		const rootDir = createTestDir()
+		const sourceDir = join(rootDir, "source")
+		const tarArchivePath = join(rootDir, "safe.tar.gz")
+		const zipArchivePath = join(rootDir, "safe.zip")
+		const tarDestDir = join(rootDir, "tar-dest")
+		const zipDestDir = join(rootDir, "zip-dest")
+		mkdirSync(join(sourceDir, "bin"), { recursive: true })
+		mkdirSync(tarDestDir, { recursive: true })
+		mkdirSync(zipDestDir, { recursive: true })
+		writeFileSync(join(sourceDir, "bin", "tool.txt"), "safe")
+		symlinkSync("tool.txt", join(sourceDir, "bin", "tool-link"))
+		runCommand(`tar -czf "${tarArchivePath}" -C "${sourceDir}" .`)
+		runCommand(`zip -qry "${zipArchivePath}" .`, sourceDir)
+
+		//#when
+		await extractTarGz(tarArchivePath, tarDestDir)
+		await extractZip(zipArchivePath, zipDestDir)
+
+		//#then
+		expect(readFileSync(join(tarDestDir, "bin", "tool.txt"), "utf8")).toBe("safe")
+		expect(readFileSync(join(zipDestDir, "bin", "tool.txt"), "utf8")).toBe("safe")
+		expect(lstatSync(join(tarDestDir, "bin", "tool-link")).isSymbolicLink()).toBe(true)
+		expect(lstatSync(join(zipDestDir, "bin", "tool-link")).isSymbolicLink()).toBe(true)
+	})
+})