_ Git - youtube-dl/blob - youtube_dl/swfinterp.py

   1 from __future__ import unicode_literals
   2
   3 import collections
   4 import io
   5 import struct
   6 import zlib
   7
   8 from .utils import ExtractorError
   9
  10
  11 def _extract_tags(file_contents):
  12     if file_contents[1:3] != b'WS':
  13         raise ExtractorError(
  14             'Not an SWF file; header is %r' % file_contents[:3])
  15     if file_contents[:1] == b'C':
  16         content = zlib.decompress(file_contents[8:])
  17     else:
  18         raise NotImplementedError(
  19             'Unsupported compression format %r' %
  20             file_contents[:1])
  21
  22     # Determine number of bits in framesize rectangle
  23     framesize_nbits = struct.unpack('!B', content[:1])[0] >> 3
  24     framesize_len = (5 + 4 * framesize_nbits + 7) // 8
  25
  26     pos = framesize_len + 2 + 2
  27     while pos < len(content):
  28         header16 = struct.unpack('<H', content[pos:pos + 2])[0]
  29         pos += 2
  30         tag_code = header16 >> 6
  31         tag_len = header16 & 0x3f
  32         if tag_len == 0x3f:
  33             tag_len = struct.unpack('<I', content[pos:pos + 4])[0]
  34             pos += 4
  35         assert pos + tag_len <= len(content), \
  36             ('Tag %d ends at %d+%d - that\'s longer than the file (%d)'
  37                 % (tag_code, pos, tag_len, len(content)))
  38         yield (tag_code, content[pos:pos + tag_len])
  39         pos += tag_len
  40
  41
  42 class _AVM_Object(object):
  43     def __init__(self, value=None, name_hint=None):
  44         self.value = value
  45         self.name_hint = name_hint
  46
  47     def __repr__(self):
  48         nh = '' if self.name_hint is None else (' %s' % self.name_hint)
  49         return 'AVMObject%s(%r)' % (nh, self.value)
  50
  51
  52 class _AVMClass_Object(object):
  53     def __init__(self, avm_class):
  54         self.avm_class = avm_class
  55
  56     def __repr__(self):
  57         return '%s#%x' % (self.avm_class.name, id(self))
  58
  59
  60 class _AVMClass(object):
  61     def __init__(self, name_idx, name):
  62         self.name_idx = name_idx
  63         self.name = name
  64         self.method_names = {}
  65         self.method_idxs = {}
  66         self.methods = {}
  67         self.method_pyfunctions = {}
  68         self.variables = {}
  69
  70     def make_object(self):
  71         return _AVMClass_Object(self)
  72
  73
  74 def _read_int(reader):
  75     res = 0
  76     shift = 0
  77     for _ in range(5):
  78         buf = reader.read(1)
  79         assert len(buf) == 1
  80         b = struct.unpack('<B', buf)[0]
  81         res = res | ((b & 0x7f) << shift)
  82         if b & 0x80 == 0:
  83             break
  84         shift += 7
  85     return res
  86
  87
  88 def _u30(reader):
  89     res = _read_int(reader)
  90     assert res & 0xf0000000 == 0
  91     return res
  92 u32 = _read_int
  93
  94
  95 def _s32(reader):
  96     v = _read_int(reader)
  97     if v & 0x80000000 != 0:
  98         v = - ((v ^ 0xffffffff) + 1)
  99     return v
 100
 101
 102 def _s24(reader):
 103     bs = reader.read(3)
 104     assert len(bs) == 3
 105     last_byte = b'\xff' if (ord(bs[2:3]) >= 0x80) else b'\x00'
 106     return struct.unpack('<i', bs + last_byte)[0]
 107
 108
 109 def _read_string(reader):
 110     slen = _u30(reader)
 111     resb = reader.read(slen)
 112     assert len(resb) == slen
 113     return resb.decode('utf-8')
 114
 115
 116 def _read_bytes(count, reader):
 117     assert count >= 0
 118     resb = reader.read(count)
 119     assert len(resb) == count
 120     return resb
 121
 122
 123 def _read_byte(reader):
 124     resb = _read_bytes(1, reader=reader)
 125     res = struct.unpack('<B', resb)[0]
 126     return res
 127
 128
 129 class SWFInterpreter(object):
 130     def __init__(self, file_contents):
 131         code_tag = next(tag
 132                         for tag_code, tag in _extract_tags(file_contents)
 133                         if tag_code == 82)
 134         p = code_tag.index(b'\0', 4) + 1
 135         code_reader = io.BytesIO(code_tag[p:])
 136
 137         # Parse ABC (AVM2 ByteCode)
 138
 139         # Define a couple convenience methods
 140         u30 = lambda *args: _u30(*args, reader=code_reader)
 141         s32 = lambda *args: _s32(*args, reader=code_reader)
 142         u32 = lambda *args: _u32(*args, reader=code_reader)
 143         read_bytes = lambda *args: _read_bytes(*args, reader=code_reader)
 144         read_byte = lambda *args: _read_byte(*args, reader=code_reader)
 145
 146         # minor_version + major_version
 147         read_bytes(2 + 2)
 148
 149         # Constant pool
 150         int_count = u30()
 151         for _c in range(1, int_count):
 152             s32()
 153         uint_count = u30()
 154         for _c in range(1, uint_count):
 155             u32()
 156         double_count = u30()
 157         read_bytes(max(0, (double_count - 1)) * 8)
 158         string_count = u30()
 159         constant_strings = ['']
 160         for _c in range(1, string_count):
 161             s = _read_string(code_reader)
 162             constant_strings.append(s)
 163         namespace_count = u30()
 164         for _c in range(1, namespace_count):
 165             read_bytes(1)  # kind
 166             u30()  # name
 167         ns_set_count = u30()
 168         for _c in range(1, ns_set_count):
 169             count = u30()
 170             for _c2 in range(count):
 171                 u30()
 172         multiname_count = u30()
 173         MULTINAME_SIZES = {
 174             0x07: 2,  # QName
 175             0x0d: 2,  # QNameA
 176             0x0f: 1,  # RTQName
 177             0x10: 1,  # RTQNameA
 178             0x11: 0,  # RTQNameL
 179             0x12: 0,  # RTQNameLA
 180             0x09: 2,  # Multiname
 181             0x0e: 2,  # MultinameA
 182             0x1b: 1,  # MultinameL
 183             0x1c: 1,  # MultinameLA
 184         }
 185         self.multinames = ['']
 186         for _c in range(1, multiname_count):
 187             kind = u30()
 188             assert kind in MULTINAME_SIZES, 'Invalid multiname kind %r' % kind
 189             if kind == 0x07:
 190                 u30()  # namespace_idx
 191                 name_idx = u30()
 192                 self.multinames.append(constant_strings[name_idx])
 193             else:
 194                 self.multinames.append('[MULTINAME kind: %d]' % kind)
 195                 for _c2 in range(MULTINAME_SIZES[kind]):
 196                     u30()
 197
 198         # Methods
 199         method_count = u30()
 200         MethodInfo = collections.namedtuple(
 201             'MethodInfo',
 202             ['NEED_ARGUMENTS', 'NEED_REST'])
 203         method_infos = []
 204         for method_id in range(method_count):
 205             param_count = u30()
 206             u30()  # return type
 207             for _ in range(param_count):
 208                 u30()  # param type
 209             u30()  # name index (always 0 for youtube)
 210             flags = read_byte()
 211             if flags & 0x08 != 0:
 212                 # Options present
 213                 option_count = u30()
 214                 for c in range(option_count):
 215                     u30()  # val
 216                     read_bytes(1)  # kind
 217             if flags & 0x80 != 0:
 218                 # Param names present
 219                 for _ in range(param_count):
 220                     u30()  # param name
 221             mi = MethodInfo(flags & 0x01 != 0, flags & 0x04 != 0)
 222             method_infos.append(mi)
 223
 224         # Metadata
 225         metadata_count = u30()
 226         for _c in range(metadata_count):
 227             u30()  # name
 228             item_count = u30()
 229             for _c2 in range(item_count):
 230                 u30()  # key
 231                 u30()  # value
 232
 233         def parse_traits_info():
 234             trait_name_idx = u30()
 235             kind_full = read_byte()
 236             kind = kind_full & 0x0f
 237             attrs = kind_full >> 4
 238             methods = {}
 239             if kind in [0x00, 0x06]:  # Slot or Const
 240                 u30()  # Slot id
 241                 u30()  # type_name_idx
 242                 vindex = u30()
 243                 if vindex != 0:
 244                     read_byte()  # vkind
 245             elif kind in [0x01, 0x02, 0x03]:  # Method / Getter / Setter
 246                 u30()  # disp_id
 247                 method_idx = u30()
 248                 methods[self.multinames[trait_name_idx]] = method_idx
 249             elif kind == 0x04:  # Class
 250                 u30()  # slot_id
 251                 u30()  # classi
 252             elif kind == 0x05:  # Function
 253                 u30()  # slot_id
 254                 function_idx = u30()
 255                 methods[function_idx] = self.multinames[trait_name_idx]
 256             else:
 257                 raise ExtractorError('Unsupported trait kind %d' % kind)
 258
 259             if attrs & 0x4 != 0:  # Metadata present
 260                 metadata_count = u30()
 261                 for _c3 in range(metadata_count):
 262                     u30()  # metadata index
 263
 264             return methods
 265
 266         # Classes
 267         class_count = u30()
 268         classes = []
 269         for class_id in range(class_count):
 270             name_idx = u30()
 271             classes.append(_AVMClass(name_idx, self.multinames[name_idx]))
 272             u30()  # super_name idx
 273             flags = read_byte()
 274             if flags & 0x08 != 0:  # Protected namespace is present
 275                 u30()  # protected_ns_idx
 276             intrf_count = u30()
 277             for _c2 in range(intrf_count):
 278                 u30()
 279             u30()  # iinit
 280             trait_count = u30()
 281             for _c2 in range(trait_count):
 282                 parse_traits_info()
 283         assert len(classes) == class_count
 284         self._classes_by_name = dict((c.name, c) for c in classes)
 285
 286         for avm_class in classes:
 287             u30()  # cinit
 288             trait_count = u30()
 289             for _c2 in range(trait_count):
 290                 trait_methods = parse_traits_info()
 291                 avm_class.method_names.update(trait_methods.items())
 292                 avm_class.method_idxs.update(dict(
 293                     (idx, name)
 294                     for name, idx in trait_methods.items()))
 295
 296         # Scripts
 297         script_count = u30()
 298         for _c in range(script_count):
 299             u30()  # init
 300             trait_count = u30()
 301             for _c2 in range(trait_count):
 302                 parse_traits_info()
 303
 304         # Method bodies
 305         method_body_count = u30()
 306         Method = collections.namedtuple('Method', ['code', 'local_count'])
 307         for _c in range(method_body_count):
 308             method_idx = u30()
 309             u30()  # max_stack
 310             local_count = u30()
 311             u30()  # init_scope_depth
 312             u30()  # max_scope_depth
 313             code_length = u30()
 314             code = read_bytes(code_length)
 315             for avm_class in classes:
 316                 if method_idx in avm_class.method_idxs:
 317                     m = Method(code, local_count)
 318                     avm_class.methods[avm_class.method_idxs[method_idx]] = m
 319             exception_count = u30()
 320             for _c2 in range(exception_count):
 321                 u30()  # from
 322                 u30()  # to
 323                 u30()  # target
 324                 u30()  # exc_type
 325                 u30()  # var_name
 326             trait_count = u30()
 327             for _c2 in range(trait_count):
 328                 parse_traits_info()
 329
 330         assert p + code_reader.tell() == len(code_tag)
 331
 332     def extract_class(self, class_name):
 333         try:
 334             return self._classes_by_name[class_name]
 335         except KeyError:
 336             raise ExtractorError('Class %r not found' % class_name)
 337
 338     def extract_function(self, avm_class, func_name):
 339         if func_name in avm_class.method_pyfunctions:
 340             return avm_class.method_pyfunctions[func_name]
 341         if func_name in self._classes_by_name:
 342             return self._classes_by_name[func_name].make_object()
 343         if func_name not in avm_class.methods:
 344             raise ExtractorError('Cannot find function %r' % func_name)
 345         m = avm_class.methods[func_name]
 346
 347         def resfunc(args):
 348             # Helper functions
 349             coder = io.BytesIO(m.code)
 350             s24 = lambda: _s24(coder)
 351             u30 = lambda: _u30(coder)
 352
 353             print('Invoking %s.%s(%r)' % (avm_class.name, func_name, tuple(args)))
 354             registers = [avm_class.variables] + list(args) + [None] * m.local_count
 355             stack = []
 356             scopes = collections.deque([avm_class.variables])
 357             while True:
 358                 opcode = _read_byte(coder)
 359                 print('opcode: %r, stack(%d): %r' % (opcode, len(stack), stack))
 360                 if opcode == 17:  # iftrue
 361                     offset = s24()
 362                     value = stack.pop()
 363                     if value:
 364                         coder.seek(coder.tell() + offset)
 365                 elif opcode == 18:  # iffalse
 366                     offset = s24()
 367                     value = stack.pop()
 368                     if not value:
 369                         coder.seek(coder.tell() + offset)
 370                 elif opcode == 36:  # pushbyte
 371                     v = _read_byte(coder)
 372                     stack.append(v)
 373                 elif opcode == 42:  # dup
 374                     value = stack[-1]
 375                     stack.append(value)
 376                 elif opcode == 44:  # pushstring
 377                     idx = u30()
 378                     stack.append(constant_strings[idx])
 379                 elif opcode == 48:  # pushscope
 380                     new_scope = stack.pop()
 381                     scopes.append(new_scope)
 382                 elif opcode == 70:  # callproperty
 383                     index = u30()
 384                     mname = self.multinames[index]
 385                     arg_count = u30()
 386                     args = list(reversed(
 387                         [stack.pop() for _ in range(arg_count)]))
 388                     obj = stack.pop()
 389                     if mname == 'split':
 390                         assert len(args) == 1
 391                         assert isinstance(args[0], compat_str)
 392                         assert isinstance(obj, compat_str)
 393                         if args[0] == '':
 394                             res = list(obj)
 395                         else:
 396                             res = obj.split(args[0])
 397                         stack.append(res)
 398                     elif mname == 'slice':
 399                         assert len(args) == 1
 400                         assert isinstance(args[0], int)
 401                         assert isinstance(obj, list)
 402                         res = obj[args[0]:]
 403                         stack.append(res)
 404                     elif mname == 'join':
 405                         assert len(args) == 1
 406                         assert isinstance(args[0], compat_str)
 407                         assert isinstance(obj, list)
 408                         res = args[0].join(obj)
 409                         stack.append(res)
 410                     elif mname in avm_class.method_pyfunctions:
 411                         stack.append(avm_class.method_pyfunctions[mname](args))
 412                     else:
 413                         raise NotImplementedError(
 414                             'Unsupported property %r on %r'
 415                             % (mname, obj))
 416                 elif opcode == 72:  # returnvalue
 417                     res = stack.pop()
 418                     return res
 419                 elif opcode == 74:  # constructproperty
 420                     index = u30()
 421                     arg_count = u30()
 422                     args = list(reversed(
 423                         [stack.pop() for _ in range(arg_count)]))
 424                     obj = stack.pop()
 425
 426                     mname = self.multinames[index]
 427                     construct_method = self.extract_function(
 428                         obj.avm_class, mname)
 429                     # We do not actually call the constructor for now;
 430                     # we just pretend it does nothing
 431                     stack.append(obj)
 432                 elif opcode == 79:  # callpropvoid
 433                     index = u30()
 434                     mname = self.multinames[index]
 435                     arg_count = u30()
 436                     args = list(reversed(
 437                         [stack.pop() for _ in range(arg_count)]))
 438                     obj = stack.pop()
 439                     if mname == 'reverse':
 440                         assert isinstance(obj, list)
 441                         obj.reverse()
 442                     else:
 443                         raise NotImplementedError(
 444                             'Unsupported (void) property %r on %r'
 445                             % (mname, obj))
 446                 elif opcode == 86:  # newarray
 447                     arg_count = u30()
 448                     arr = []
 449                     for i in range(arg_count):
 450                         arr.append(stack.pop())
 451                     arr = arr[::-1]
 452                     stack.append(arr)
 453                 elif opcode == 94:  # findproperty
 454                     index = u30()
 455                     mname = self.multinames[index]
 456                     for s in reversed(scopes):
 457                         if mname in s:
 458                             res = s
 459                             break
 460                     else:
 461                         res = scopes[0]
 462                     stack.append(res)
 463                 elif opcode == 96:  # getlex
 464                     index = u30()
 465                     mname = self.multinames[index]
 466                     for s in reversed(scopes):
 467                         if mname in s:
 468                             scope = s
 469                             break
 470                     else:
 471                         scope = scopes[0]
 472                     # I cannot find where static variables are initialized
 473                     # so let's just return None
 474                     res = scope.get(mname)
 475                     stack.append(res)
 476                 elif opcode == 97:  # setproperty
 477                     index = u30()
 478                     value = stack.pop()
 479                     idx = self.multinames[index]
 480                     obj = stack.pop()
 481                     obj[idx] = value
 482                 elif opcode == 98:  # getlocal
 483                     index = u30()
 484                     stack.append(registers[index])
 485                 elif opcode == 99:  # setlocal
 486                     index = u30()
 487                     value = stack.pop()
 488                     registers[index] = value
 489                 elif opcode == 102:  # getproperty
 490                     index = u30()
 491                     pname = self.multinames[index]
 492                     if pname == 'length':
 493                         obj = stack.pop()
 494                         assert isinstance(obj, list)
 495                         stack.append(len(obj))
 496                     else:  # Assume attribute access
 497                         idx = stack.pop()
 498                         assert isinstance(idx, int)
 499                         obj = stack.pop()
 500                         assert isinstance(obj, list)
 501                         stack.append(obj[idx])
 502                 elif opcode == 115:  # convert_
 503                     value = stack.pop()
 504                     intvalue = int(value)
 505                     stack.append(intvalue)
 506                 elif opcode == 128:  # coerce
 507                     u30()
 508                 elif opcode == 133:  # coerce_s
 509                     assert isinstance(stack[-1], (type(None), compat_str))
 510                 elif opcode == 160:  # add
 511                     value2 = stack.pop()
 512                     value1 = stack.pop()
 513                     res = value1 + value2
 514                     stack.append(res)
 515                 elif opcode == 161:  # subtract
 516                     value2 = stack.pop()
 517                     value1 = stack.pop()
 518                     res = value1 - value2
 519                     stack.append(res)
 520                 elif opcode == 164:  # modulo
 521                     value2 = stack.pop()
 522                     value1 = stack.pop()
 523                     res = value1 % value2
 524                     stack.append(res)
 525                 elif opcode == 175:  # greaterequals
 526                     value2 = stack.pop()
 527                     value1 = stack.pop()
 528                     result = value1 >= value2
 529                     stack.append(result)
 530                 elif opcode == 208:  # getlocal_0
 531                     stack.append(registers[0])
 532                 elif opcode == 209:  # getlocal_1
 533                     stack.append(registers[1])
 534                 elif opcode == 210:  # getlocal_2
 535                     stack.append(registers[2])
 536                 elif opcode == 211:  # getlocal_3
 537                     stack.append(registers[3])
 538                 elif opcode == 214:  # setlocal_2
 539                     registers[2] = stack.pop()
 540                 elif opcode == 215:  # setlocal_3
 541                     registers[3] = stack.pop()
 542                 else:
 543                     raise NotImplementedError(
 544                         'Unsupported opcode %d' % opcode)
 545
 546         avm_class.method_pyfunctions[func_name] = resfunc
 547         return resfunc
 548