bplist-universal/src/bplistParser.ts

Binary plist parser for node

import bigInt from "big-integer";

const defaultMaxObjectSize = 100 * 1000 * 1000; // 100Meg
const defaultMaxObjectCount = 32768;
interface Opts {
  maxObjectSize?: number;
  maxObjectCount?: number;
}
// EPOCH = new SimpleDateFormat("yyyy MM dd zzz").parse("2001 01 01 GMT").getTime();
// ...but that's annoying in a static initializer because it can throw exceptions, ick.
// So we just hardcode the correct value.
const EPOCH = 978307200000;

export const parseBuffer = function (buffer: Buffer, opts?: Opts) {
  const { maxObjectSize = defaultMaxObjectSize, maxObjectCount = defaultMaxObjectCount } = opts || {};
  // check header
  const header = buffer.subarray(0, "bplist".length).toString("utf8");
  if (header !== "bplist") {
    throw new Error("Invalid binary plist. Expected 'bplist' at offset 0.");
  }

  // Handle trailer, last 32 bytes of the file
  const trailer = buffer.subarray(buffer.length - 32, buffer.length);
  // 6 null bytes (index 0 to 5)
  const offsetSize = trailer.readUInt8(6);
  const objectRefSize = trailer.readUInt8(7);
  const numObjects = readUInt64BE(trailer, 8);
  const topObject = readUInt64BE(trailer, 16);
  const offsetTableOffset = readUInt64BE(trailer, 24);
  if (numObjects > maxObjectCount) {
    throw new Error("maxObjectCount exceeded");
  }

  // Handle offset table
  const offsetTable: number[] = [];

  for (let i = 0; i < numObjects; i++) {
    const offsetBytes = buffer.subarray(offsetTableOffset + i * offsetSize, offsetTableOffset + (i + 1) * offsetSize);
    offsetTable[i] = readUInt(offsetBytes, 0);
  }

  // Parses an object inside the currently parsed binary property list.
  // For the format specification check
  // <a href="https://www.opensource.apple.com/source/CF/CF-635/CFBinaryPList.c">
  // Apple's binary property list parser implementation</a>.
  function parseObject(tableOffset: number): any {
    const offset = offsetTable[tableOffset];
    const type = buffer[offset];
    const objType = (type & 0xf0) >> 4; //First  4 bits
    const objInfo = type & 0x0f; //Second 4 bits
    switch (objType) {
      case 0x0:
        return parseSimple();
      case 0x1:
        return parseInteger();
      case 0x8:
        return parseUID();
      case 0x2:
        return parseReal();
      case 0x3:
        return parseDate();
      case 0x4:
        return parseData();
      case 0x5: // ASCII
        return parsePlistString();
      case 0x6: // UTF-16
        return parsePlistString(1);
      case 0xa:
        return parseArray();
      case 0xd:
        return parseDictionary();
      default:
        throw new Error("Unhandled type 0x" + objType.toString(16));
    }

    function parseSimple() {
      //Simple
      switch (objInfo) {
        case 0x0: // null
          return null;
        case 0x8: // false
          return false;
        case 0x9: // true
          return true;
        case 0xf: // filler byte
          return null;
        default:
          throw new Error("Unhandled simple type 0x" + objType.toString(16));
      }
    }

    function bufferToHexString(buffer: Buffer) {
      let str = "";
      let i;
      for (i = 0; i < buffer.length; i++) {
        if (buffer[i] != 0x00) {
          break;
        }
      }
      for (; i < buffer.length; i++) {
        const part = "00" + buffer[i].toString(16);
        str += part.substr(part.length - 2);
      }
      return str;
    }

    function parseInteger(): number | bigInt.BigInteger {
      const length = Math.pow(2, objInfo);
      if (length < maxObjectSize) {
        const data = buffer.subarray(offset + 1, offset + 1 + length);
        if (length === 16) {
          const str = bufferToHexString(data);
          return bigInt(str, 16);
        }
        return data.reduce((acc, curr) => {
          acc <<= 8;
          acc |= curr & 255;
          return acc;
        });
      }
      throw new Error(
        `Too little heap space available! Wanted to read ${length} bytes, but only ${maxObjectSize} are available.`,
      );
    }

    function parseUID() {
      const length = objInfo + 1;
      if (length < maxObjectSize) {
        const uint = readUInt(buffer.subarray(offset + 1, offset + 1 + length));
        return { UID: uint };
      }
      throw new Error(
        `Too little heap space available! Wanted to read ${length} bytes, but only ${maxObjectSize} are available.`,
      );
    }

    function parseReal() {
      const length = Math.pow(2, objInfo);
      if (length < maxObjectSize) {
        const realBuffer = buffer.subarray(offset + 1, offset + 1 + length);
        if (length === 4) {
          return realBuffer.readFloatBE(0);
        }
        if (length === 8) {
          return realBuffer.readDoubleBE(0);
        }
        throw new Error("Unhandled real length " + length);
      } else {
        throw new Error(
          `Too little heap space available! Wanted to read ${length} bytes, but only ${maxObjectSize} are available.`,
        );
      }
    }

    function parseDate() {
      if (objInfo != 0x3) {
        console.error("Unknown date type :" + objInfo + ". Parsing anyway...");
      }
      const dateBuffer = buffer.subarray(offset + 1, offset + 9);
      return new Date(EPOCH + 1000 * dateBuffer.readDoubleBE(0));
    }

    function parseData() {
      let dataoffset = 1;
      let length = objInfo;
      if (objInfo == 0xf) {
        const int_type = buffer[offset + 1];
        const intType = (int_type & 0xf0) / 0x10;
        if (intType != 0x1) {
          console.error("0x4: UNEXPECTED LENGTH-INT TYPE! " + intType);
        }
        const intInfo = int_type & 0x0f;
        const intLength = Math.pow(2, intInfo);
        dataoffset = 2 + intLength;
        if (intLength < 3) {
          length = readUInt(buffer.subarray(offset + 2, offset + 2 + intLength));
        } else {
          length = readUInt(buffer.subarray(offset + 2, offset + 2 + intLength));
        }
      }
      if (length < maxObjectSize) {
        return buffer.subarray(offset + dataoffset, offset + dataoffset + length);
      }
      throw new Error(
        `Too little heap space available! Wanted to read ${length} bytes, but only ${maxObjectSize} are available.`,
      );
    }

    function parsePlistString(isUtf16: 0 | 1 = 0) {
      let enc: BufferEncoding = "utf8";
      let length = objInfo;
      let stroffset = 1;
      if (objInfo == 0xf) {
        const int_type = buffer[offset + 1];
        const intType = (int_type & 0xf0) / 0x10;
        if (intType != 0x1) {
          console.error("UNEXPECTED LENGTH-INT TYPE! " + intType);
        }
        const intInfo = int_type & 0x0f;
        const intLength = Math.pow(2, intInfo);
        stroffset = 2 + intLength;
        if (intLength < 3) {
          length = readUInt(buffer.subarray(offset + 2, offset + 2 + intLength));
        } else {
          length = readUInt(buffer.subarray(offset + 2, offset + 2 + intLength));
        }
      }
      // length is String length -> to get byte length multiply by 2, as 1 character takes 2 bytes in UTF-16
      length *= isUtf16 + 1;
      if (length < maxObjectSize) {
        let plistString = Buffer.from(buffer.subarray(offset + stroffset, offset + stroffset + length));
        if (isUtf16) {
          plistString = swapBytes(plistString);
          enc = "ucs2";
        }
        return plistString.toString(enc);
      }
      throw new Error(
        `Too little heap space available! Wanted to read ${length} bytes, but only ${maxObjectSize} are available.`,
      );
    }

    function parseArray(): any[] {
      let length = objInfo;
      let arrayoffset = 1;
      if (objInfo == 0xf) {
        const int_type = buffer[offset + 1];
        const intType = (int_type & 0xf0) / 0x10;
        if (intType != 0x1) {
          console.error("0xa: UNEXPECTED LENGTH-INT TYPE! " + intType);
        }
        const intInfo = int_type & 0x0f;
        const intLength = Math.pow(2, intInfo);
        arrayoffset = 2 + intLength;
        if (intLength < 3) {
          length = readUInt(buffer.subarray(offset + 2, offset + 2 + intLength));
        } else {
          length = readUInt(buffer.subarray(offset + 2, offset + 2 + intLength));
        }
      }
      if (length * objectRefSize > maxObjectSize) {
        throw new Error("Too little heap space available!");
      }
      const array = [];
      for (let i = 0; i < length; i++) {
        const objRef = readUInt(
          buffer.subarray(offset + arrayoffset + i * objectRefSize, offset + arrayoffset + (i + 1) * objectRefSize),
        );
        array[i] = parseObject(objRef);
      }
      return array;
    }

    function parseDictionary() {
      let length = objInfo;
      let dictoffset = 1;
      if (objInfo == 0xf) {
        const int_type = buffer[offset + 1];
        const intType = (int_type & 0xf0) / 0x10;
        if (intType != 0x1) {
          console.error("0xD: UNEXPECTED LENGTH-INT TYPE! " + intType);
        }
        const intInfo = int_type & 0x0f;
        const intLength = Math.pow(2, intInfo);
        dictoffset = 2 + intLength;
        if (intLength < 3) {
          length = readUInt(buffer.subarray(offset + 2, offset + 2 + intLength));
        } else {
          length = readUInt(buffer.subarray(offset + 2, offset + 2 + intLength));
        }
      }
      if (length * 2 * objectRefSize > maxObjectSize) {
        throw new Error("Too little heap space available!");
      }
      const dict = {};
      for (let i = 0; i < length; i++) {
        const keyRef = readUInt(
          buffer.subarray(offset + dictoffset + i * objectRefSize, offset + dictoffset + (i + 1) * objectRefSize),
        );
        const valRef = readUInt(
          buffer.subarray(
            offset + dictoffset + length * objectRefSize + i * objectRefSize,
            offset + dictoffset + length * objectRefSize + (i + 1) * objectRefSize,
          ),
        );
        const key = parseObject(keyRef);
        const val = parseObject(valRef);
        // @ts-ignore
        dict[key] = val;
      }
      return dict;
    }
  }

  return [parseObject(topObject)];
};
export default parseBuffer;
function readUInt(buffer: Buffer, start = 0) {
  start = start || 0;

  let l = 0;
  for (let i = start; i < buffer.length; i++) {
    l <<= 8;
    l |= buffer[i] & 0xff;
  }
  return l;
}

// we're just going to toss the high order bits because javascript doesn't have 64-bit ints
function readUInt64BE(buffer: Buffer, start: number) {
  const data = buffer.subarray(start, start + 8);
  return data.readUInt32BE(4);
}

function swapBytes(buffer: Buffer) {
  const len = buffer.length;
  for (let i = 0; i < len; i += 2) {
    const a = buffer[i];
    buffer[i] = buffer[i + 1];
    buffer[i + 1] = a;
  }
  return buffer;
}