reverse-engineering-anything/src/domain/binaryTarget.ts

import { constants } from "node:fs";
import { createHash } from "node:crypto";
import {
  access,
  open,
  readFile,
  realpath,
  stat,
  type FileHandle,
} from "node:fs/promises";
import { execFile } from "node:child_process";
import { extname, isAbsolute, join, relative, resolve, sep } from "node:path";
import { promisify } from "node:util";

import { BinaryTargetError } from "./errors.js";
import type { BinaryArchitecture, BinaryTarget } from "./binaryTargetTypes.js";
import { err, ok, type Result } from "./result.js";
import { zipPackageFormatForPath } from "./zipPackageFormat.js";

export type { BinaryArchitecture, BinaryTarget } from "./binaryTargetTypes.js";

const execFileAsync = promisify(execFile);

/**
 * Resolve and classify a readable local target before a provider is selected.
 * FAT Mach-O inputs select only a host-compatible architecture so setup remains
 * non-interactive; unsupported or ambiguous inputs are returned as typed errors.
 */
export const parseBinaryTarget = async (
  input: string,
  cwd = process.cwd(),
  hostArchitecture: NodeJS.Architecture = process.arch,
  targetKind?: BinaryTarget["kind"],
): Promise<Result<BinaryTarget, BinaryTargetError>> => {
  const candidate = isAbsolute(input) ? input : resolve(cwd, input);
  try {
    await access(candidate, constants.R_OK);
    const canonical = await realpath(candidate);
    const resolved = await resolveAppBundle(canonical);
    if (!resolved.ok) return err(resolved.error);
    const path = resolved.value;
    const handle = await open(path, "r");
    try {
      if (!(await handle.stat()).isFile())
        return err(new BinaryTargetError(path, "target is not a regular file"));
      if (
        targetKind === "database" ||
        (targetKind === undefined && path.toLowerCase().endsWith(".hop"))
      )
        return ok({
          path,
          sourcePath: canonical,
          sha256: await sha256Handle(handle),
          kind: "database",
          format: "analysis-database",
        });
      const artifactFormat = await detectArtifactFormat(path, handle);
      if (artifactFormat !== undefined) {
        const identity = {
          path,
          sourcePath: canonical,
          sha256: await sha256Handle(handle),
        };
        return isArchiveFormat(artifactFormat)
          ? ok({ ...identity, kind: "archive", format: artifactFormat })
          : ok({ ...identity, kind: "artifact", format: artifactFormat });
      }
      const detected = await readExecutableMetadata(handle, hostArchitecture);
      if (!detected.ok) return err(new BinaryTargetError(path, detected.error));
      return ok({
        path,
        sourcePath: canonical,
        sha256: await sha256Handle(handle),
        kind: "executable",
        ...detected.value,
      });
    } finally {
      await handle.close();
    }
  } catch (cause: unknown) {
    return err(
      new BinaryTargetError(candidate, "path is not readable", { cause }),
    );
  }
};

const detectArtifactFormat = async (
  path: string,
  handle: FileHandle,
): Promise<
  | Exclude<
      BinaryTarget["format"],
      "analysis-database" | "mach-o" | "elf" | "pe"
    >
  | undefined
> => {
  const lower = path.toLowerCase();
  const magic = Buffer.alloc(8);
  const observed = await handle.read(magic, 0, magic.length, 0);
  if (
    observed.bytesRead >= 4 &&
    magic[0] === 0x50 &&
    magic[1] === 0x4b &&
    [0x03, 0x05, 0x07].includes(magic[2] ?? -1) &&
    [0x04, 0x06, 0x08].includes(magic[3] ?? -1)
  ) {
    return zipPackageFormatForPath(lower) ?? "zip";
  }
  const named = namedArtifactFormat(lower);
  if (named !== undefined) return named;
  if (
    lower.endsWith(".pkg") &&
    observed.bytesRead >= 4 &&
    magic.subarray(0, 4).toString("ascii") === "xar!"
  )
    return "pkg";
  if (lower.endsWith(".dmg")) {
    const size = (await handle.stat()).size;
    if (size >= 512) {
      const trailer = Buffer.alloc(4);
      const read = await handle.read(trailer, 0, trailer.length, size - 512);
      if (read.bytesRead === 4 && trailer.toString("ascii") === "koly")
        return "dmg";
    }
  }
  return undefined;
};

const namedArtifactFormat = (
  lowerPath: string,
): "asar" | "plist" | "source-map" | "javascript" | undefined => {
  if (lowerPath.endsWith(".asar")) return "asar";
  if (lowerPath.endsWith(".plist")) return "plist";
  if (lowerPath.endsWith(".map")) return "source-map";
  return /\.(?:m?js|cjs)$/u.test(lowerPath) ? "javascript" : undefined;
};

const isArchiveFormat = (
  format: Exclude<
    BinaryTarget["format"],
    "analysis-database" | "mach-o" | "elf" | "pe"
  >,
): format is Extract<BinaryTarget, { kind: "archive" }>["format"] =>
  ["zip", "ipa", "apk", "msix", "appx", "asar", "dmg", "pkg"].includes(format);

const sha256Handle = async (handle: FileHandle): Promise<string> => {
  const hash = createHash("sha256");
  const chunk = Buffer.allocUnsafe(64 * 1024);
  let position = 0;
  while (true) {
    const observed = await handle.read(chunk, 0, chunk.length, position);
    if (observed.bytesRead === 0) break;
    hash.update(chunk.subarray(0, observed.bytesRead));
    position += observed.bytesRead;
  }
  return hash.digest("hex");
};

const resolveAppBundle = async (
  path: string,
): Promise<Result<string, BinaryTargetError>> => {
  const metadata = await stat(path);
  if (!metadata.isDirectory()) return ok(path);
  if (extname(path).toLowerCase() !== ".app")
    return err(new BinaryTargetError(path, "target is not an app or file"));
  const plistPath = join(path, "Contents", "Info.plist");
  let name: string;
  try {
    const plist = await readFile(plistPath);
    name =
      plist.subarray(0, 6).toString("ascii") === "bplist"
        ? await readBinaryPlistExecutable(plistPath)
        : parseXmlPlistExecutable(plist.toString("utf8"));
  } catch (cause: unknown) {
    return err(
      new BinaryTargetError(path, "app has no readable CFBundleExecutable", {
        cause,
      }),
    );
  }
  if (!isSafeExecutableName(name))
    return err(
      new BinaryTargetError(path, "app has an unsafe CFBundleExecutable"),
    );
  const programs = join(path, "Contents", "MacOS");
  const executable = join(programs, name);
  try {
    const [canonicalPrograms, canonicalExecutable] = await Promise.all([
      realpath(programs),
      realpath(executable),
    ]);
    const location = relative(canonicalPrograms, canonicalExecutable);
    if (
      location === ".." ||
      location.startsWith(`..${sep}`) ||
      isAbsolute(location)
    )
      return err(
        new BinaryTargetError(path, "app program file leaves Contents/MacOS"),
      );
    return ok(canonicalExecutable);
  } catch (cause: unknown) {
    return err(
      new BinaryTargetError(path, "app program file is missing", { cause }),
    );
  }
};

const parseXmlPlistExecutable = (plist: string): string => {
  const match =
    /<key>\s*CFBundleExecutable\s*<\/key>\s*<string>([^<]+)<\/string>/u.exec(
      plist,
    );
  if (match?.[1] === undefined)
    throw new Error("CFBundleExecutable is missing");
  return decodeXml(match[1].trim());
};

const readBinaryPlistExecutable = async (plistPath: string): Promise<string> =>
  (
    await execFileAsync("/usr/bin/plutil", [
      "-extract",
      "CFBundleExecutable",
      "raw",
      "-o",
      "-",
      plistPath,
    ])
  ).stdout.trim();

const isSafeExecutableName = (name: string): boolean =>
  name.length > 0 &&
  name !== "." &&
  name !== ".." &&
  !name.includes("\0") &&
  !/[/\\]/u.test(name);

const decodeXml = (value: string): string =>
  value
    .replaceAll("&amp;", "&")
    .replaceAll("&lt;", "<")
    .replaceAll("&gt;", ">")
    .replaceAll("&quot;", '"')
    .replaceAll("&apos;", "'");

type ExecutableMetadata =
  | {
      readonly format: "mach-o" | "elf";
      readonly architecture: BinaryArchitecture;
      readonly availableArchitectures: readonly BinaryArchitecture[];
    }
  | {
      readonly format: "pe";
      readonly architecture: BinaryArchitecture;
      readonly availableArchitectures: readonly BinaryArchitecture[];
      readonly executableRole:
        | "application"
        | "shared-library"
        | "non-executable";
      readonly managed: boolean;
    };

const readExecutableMetadata = async (
  handle: FileHandle,
  hostArchitecture: NodeJS.Architecture,
): Promise<Result<ExecutableMetadata, string>> => {
  const prefix = Buffer.alloc(4096);
  const prefixRead = await handle.read(prefix, 0, prefix.length, 0);
  const bytes = prefix.subarray(0, prefixRead.bytesRead);
  if (bytes.length >= 64 && bytes[0] === 0x4d && bytes[1] === 0x5a) {
    const offset = bytes.readUInt32LE(0x3c);
    return readPeMetadata(handle, offset);
  }
  if (bytes.length >= 8) {
    const magic = bytes.readUInt32BE(0);
    if ([0xcafebabf, 0xbfbafeca].includes(magic)) {
      const little = magic === 0xbfbafeca;
      const count = little ? bytes.readUInt32LE(4) : bytes.readUInt32BE(4);
      const required = 8 + count * 32;
      if (count <= 128 && required > bytes.length) {
        const header = Buffer.alloc(required);
        const headerRead = await handle.read(header, 0, header.length, 0);
        return parseExecutableHeader(
          header.subarray(0, headerRead.bytesRead),
          hostArchitecture,
        );
      }
    }
  }
  return parseExecutableHeader(bytes, hostArchitecture);
};

const readPeMetadata = async (
  handle: FileHandle,
  offset: number,
): Promise<Result<ExecutableMetadata, string>> => {
  const fileHeader = Buffer.alloc(24);
  const fileHeaderRead = await handle.read(
    fileHeader,
    0,
    fileHeader.length,
    offset,
  );
  if (fileHeaderRead.bytesRead !== fileHeader.length)
    return err("invalid or truncated PE header");
  const optionalHeaderSize = fileHeader.readUInt16LE(20);
  if (optionalHeaderSize > 4096) return err("invalid PE optional header size");
  const record = Buffer.alloc(24 + optionalHeaderSize);
  const recordRead = await handle.read(record, 0, record.length, offset);
  return recordRead.bytesRead === record.length
    ? parsePeRecord(record)
    : err("invalid or truncated PE header");
};

/**
 * Parse supported executable headers without I/O. The caller supplies the host
 * architecture used for deterministic FAT Mach-O slice selection.
 */
export const parseExecutableHeader = (
  bytes: Buffer,
  hostArchitecture: NodeJS.Architecture,
): Result<ExecutableMetadata, string> => {
  if (
    bytes.length >= 4 &&
    bytes.subarray(0, 4).equals(Buffer.from([0x7f, 0x45, 0x4c, 0x46]))
  )
    return parseElf(bytes);
  if (bytes.length >= 2 && bytes[0] === 0x4d && bytes[1] === 0x5a)
    return parsePe(bytes);
  if (bytes.length < 8) return err("truncated or unsupported binary header");
  const magic = bytes.readUInt32BE(0);
  if ([0xfeedface, 0xfeedfacf, 0xcefaedfe, 0xcffaedfe].includes(magic))
    return parseThinMachO(bytes, magic);
  if ([0xcafebabe, 0xbebafeca, 0xcafebabf, 0xbfbafeca].includes(magic))
    return parseFatMachO(bytes, magic, hostArchitecture);
  return err("unsupported binary format");
};

const parseThinMachO = (
  bytes: Buffer,
  magic: number,
): Result<ExecutableMetadata, string> => {
  if (bytes.length < 8) return err("truncated Mach-O header");
  const little = magic === 0xcefaedfe || magic === 0xcffaedfe;
  const architecture = machArchitecture(
    little ? bytes.readUInt32LE(4) : bytes.readUInt32BE(4),
  );
  if (architecture === undefined) return err("unsupported Mach-O architecture");
  return ok({
    format: "mach-o",
    architecture,
    availableArchitectures: [architecture],
  });
};

const parseFatMachO = (
  bytes: Buffer,
  magic: number,
  host: NodeJS.Architecture,
): Result<ExecutableMetadata, string> => {
  const little = magic === 0xbebafeca || magic === 0xbfbafeca;
  const is64 = magic === 0xcafebabf || magic === 0xbfbafeca;
  if (bytes.length < 8) return err("truncated FAT header");
  const read = (offset: number): number =>
    little ? bytes.readUInt32LE(offset) : bytes.readUInt32BE(offset);
  const count = read(4);
  const entrySize = is64 ? 32 : 20;
  if (count === 0 || count > 128 || bytes.length < 8 + count * entrySize)
    return err("truncated or invalid FAT architecture table");
  const architectures: BinaryArchitecture[] = [];
  for (let index = 0; index < count; index += 1) {
    const architecture = machArchitecture(read(8 + index * entrySize));
    if (architecture !== undefined && !architectures.includes(architecture))
      architectures.push(architecture);
  }
  const preferred =
    host === "arm64"
      ? "arm64"
      : host === "x64"
        ? "x86_64"
        : host === "ia32"
          ? "x86"
          : host === "arm"
            ? "arm"
            : undefined;
  if (preferred === undefined || !architectures.includes(preferred))
    return err(`FAT binary has no host-compatible ${host} architecture`);
  return ok({
    format: "mach-o",
    architecture: preferred,
    availableArchitectures: architectures,
  });
};

const parseElf = (bytes: Buffer): Result<ExecutableMetadata, string> => {
  if (bytes.length < 20) return err("truncated ELF header");
  if (bytes[4] !== 1 && bytes[4] !== 2) return err("unsupported ELF class");
  const little = bytes[5] === 1;
  if (!little && bytes[5] !== 2) return err("unsupported ELF endianness");
  const machine = little ? bytes.readUInt16LE(18) : bytes.readUInt16BE(18);
  const architecture = elfArchitecture(machine);
  if (architecture === undefined) return err("unsupported ELF architecture");
  return ok({
    format: "elf",
    architecture,
    availableArchitectures: [architecture],
  });
};

const parsePe = (bytes: Buffer): Result<ExecutableMetadata, string> => {
  if (bytes.length < 64) return err("truncated PE DOS header");
  const offset = bytes.readUInt32LE(0x3c);
  if (offset > bytes.length - 24) return err("invalid or truncated PE header");
  return parsePeRecord(bytes.subarray(offset));
};

const parsePeRecord = (record: Buffer): Result<ExecutableMetadata, string> => {
  if (
    record.length < 24 ||
    record.toString("binary", 0, 4) !== "PE\u0000\u0000"
  )
    return err("invalid or truncated PE header");
  const architecture = peArchitecture(record.readUInt16LE(4));
  if (architecture === undefined) return err("unsupported PE architecture");
  const optionalHeaderSize = record.readUInt16LE(20);
  if (optionalHeaderSize > 4096 || record.length < 24 + optionalHeaderSize)
    return err("invalid or truncated PE optional header");
  const optionalHeader = record.subarray(24, 24 + optionalHeaderSize);
  const managed = peManagedStatus(optionalHeader, architecture);
  if (!managed.ok) return managed;
  const characteristics = record.readUInt16LE(22);
  return ok({
    format: "pe",
    architecture,
    availableArchitectures: [architecture],
    executableRole:
      (characteristics & 0x0002) === 0
        ? "non-executable"
        : (characteristics & 0x2000) === 0
          ? "application"
          : "shared-library",
    managed: managed.value,
  });
};

const peManagedStatus = (
  optionalHeader: Buffer,
  architecture: BinaryArchitecture,
): Result<boolean, string> => {
  if (optionalHeader.length < 2) return err("truncated PE optional header");
  const magic = optionalHeader.readUInt16LE(0);
  const expectedMagic =
    architecture === "x86_64" || architecture === "arm64" ? 0x20b : 0x10b;
  if (magic !== expectedMagic)
    return err("PE optional-header magic does not match its architecture");
  const directoryOffset = magic === 0x20b ? 112 : 96;
  const directoryCountOffset = directoryOffset - 4;
  if (optionalHeader.length < directoryCountOffset + 4)
    return err("truncated PE optional header");
  const directoryCount = optionalHeader.readUInt32LE(directoryCountOffset);
  const requiredBytes = directoryOffset + directoryCount * 8;
  if (
    !Number.isSafeInteger(requiredBytes) ||
    requiredBytes > optionalHeader.length
  )
    return err("truncated PE data-directory table");
  if (directoryCount <= 14) return ok(false);
  const cliDirectory = directoryOffset + 14 * 8;
  return ok(
    optionalHeader.readUInt32LE(cliDirectory) !== 0 ||
      optionalHeader.readUInt32LE(cliDirectory + 4) !== 0,
  );
};

const machArchitecture = (cpu: number): BinaryArchitecture | undefined => {
  switch (cpu) {
    case 7:
      return "x86";
    case 0x01000007:
      return "x86_64";
    case 12:
      return "arm";
    case 0x0100000c:
      return "arm64";
  }
  return undefined;
};

const elfArchitecture = (machine: number): BinaryArchitecture | undefined => {
  switch (machine) {
    case 3:
      return "x86";
    case 62:
      return "x86_64";
    case 40:
      return "arm";
    case 183:
      return "arm64";
  }
  return undefined;
};

const peArchitecture = (machine: number): BinaryArchitecture | undefined => {
  switch (machine) {
    case 0x14c:
      return "x86";
    case 0x8664:
      return "x86_64";
    case 0x1c0:
      return "arm";
    case 0xaa64:
      return "arm64";
  }
  return undefined;
};