1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
|
from __future__ import unicode_literals
import json
import operator
import re
from .utils import (
ExtractorError,
)
_OPERATORS = [
('|', operator.or_),
('^', operator.xor),
('&', operator.and_),
('>>', operator.rshift),
('<<', operator.lshift),
('-', operator.sub),
('+', operator.add),
('%', operator.mod),
('/', operator.div),
('*', operator.mul),
]
_ASSIGN_OPERATORS = [(op + '=', opfunc) for op, opfunc in _OPERATORS]
_ASSIGN_OPERATORS.append(('=', lambda cur, right: right))
_NAME_RE = r'[a-zA-Z_$][a-zA-Z_$0-9]*'
class JSInterpreter(object):
def __init__(self, code, objects=None):
if objects is None:
objects = {}
self.code = self._remove_comments(code)
self._functions = {}
self._objects = objects
def _remove_comments(self, code):
return re.sub(r'(?s)/\*.*?\*/', '', code)
def interpret_statement(self, stmt, local_vars, allow_recursion=100):
if allow_recursion < 0:
raise ExtractorError('Recursion limit reached')
should_abort = False
stmt = stmt.lstrip()
stmt_m = re.match(r'var\s', stmt)
if stmt_m:
expr = stmt[len(stmt_m.group(0)):]
else:
return_m = re.match(r'return(?:\s+|$)', stmt)
if return_m:
expr = stmt[len(return_m.group(0)):]
should_abort = True
else:
# Try interpreting it as an expression
expr = stmt
v = self.interpret_expression(expr, local_vars, allow_recursion)
return v, should_abort
def interpret_expression(self, expr, local_vars, allow_recursion):
expr = expr.strip()
if expr == '': # Empty expression
return None
if expr.startswith('('):
parens_count = 0
for m in re.finditer(r'[()]', expr):
if m.group(0) == '(':
parens_count += 1
else:
parens_count -= 1
if parens_count == 0:
sub_expr = expr[1:m.start()]
sub_result = self.interpret_expression(
sub_expr, local_vars, allow_recursion)
remaining_expr = expr[m.end():].strip()
if not remaining_expr:
return sub_result
else:
expr = json.dumps(sub_result) + remaining_expr
break
else:
raise ExtractorError('Premature end of parens in %r' % expr)
for op, opfunc in _ASSIGN_OPERATORS:
m = re.match(r'''(?x)
(?P<out>%s)(?:\[(?P<index>[^\]]+?)\])?
\s*%s
(?P<expr>.*)$''' % (_NAME_RE, re.escape(op)), expr)
if not m:
continue
right_val = self.interpret_expression(
m.group('expr'), local_vars, allow_recursion - 1)
if m.groupdict().get('index'):
lvar = local_vars[m.group('out')]
idx = self.interpret_expression(
m.group('index'), local_vars, allow_recursion)
assert isinstance(idx, int)
cur = lvar[idx]
val = opfunc(cur, right_val)
lvar[idx] = val
return val
else:
cur = local_vars.get(m.group('out'))
val = opfunc(cur, right_val)
local_vars[m.group('out')] = val
return val
if expr.isdigit():
return int(expr)
var_m = re.match(
r'(?!if|return|true|false)(?P<name>%s)$' % _NAME_RE,
expr)
if var_m:
return local_vars[var_m.group('name')]
try:
return json.loads(expr)
except ValueError:
pass
m = re.match(
r'(?P<var>%s)\.(?P<member>[^(]+)(?:\(+(?P<args>[^()]*)\))?$' % _NAME_RE,
expr)
if m:
variable = m.group('var')
member = m.group('member')
arg_str = m.group('args')
if variable in local_vars:
obj = local_vars[variable]
else:
if variable not in self._objects:
self._objects[variable] = self.extract_object(variable)
obj = self._objects[variable]
if arg_str is None:
# Member access
if member == 'length':
return len(obj)
return obj[member]
assert expr.endswith(')')
# Function call
if arg_str == '':
argvals = tuple()
else:
argvals = tuple([
self.interpret_expression(v, local_vars, allow_recursion)
for v in arg_str.split(',')])
if member == 'split':
assert argvals == ('',)
return list(obj)
if member == 'join':
assert len(argvals) == 1
return argvals[0].join(obj)
if member == 'reverse':
assert len(argvals) == 0
obj.reverse()
return obj
if member == 'slice':
assert len(argvals) == 1
return obj[argvals[0]:]
if member == 'splice':
assert isinstance(obj, list)
index, howMany = argvals
res = []
for i in range(index, min(index + howMany, len(obj))):
res.append(obj.pop(index))
return res
return obj[member](argvals)
m = re.match(
r'(?P<in>%s)\[(?P<idx>.+)\]$' % _NAME_RE, expr)
if m:
val = local_vars[m.group('in')]
idx = self.interpret_expression(
m.group('idx'), local_vars, allow_recursion - 1)
return val[idx]
for op, opfunc in _OPERATORS:
m = re.match(r'(?P<x>.+?)%s(?P<y>.+)' % re.escape(op), expr)
if not m:
continue
x, abort = self.interpret_statement(
m.group('x'), local_vars, allow_recursion - 1)
if abort:
raise ExtractorError(
'Premature left-side return of %s in %r' % (op, expr))
y, abort = self.interpret_statement(
m.group('y'), local_vars, allow_recursion - 1)
if abort:
raise ExtractorError(
'Premature right-side return of %s in %r' % (op, expr))
return opfunc(x, y)
m = re.match(
r'^(?P<func>%s)\((?P<args>[a-zA-Z0-9_$,]+)\)$' % _NAME_RE, expr)
if m:
fname = m.group('func')
argvals = tuple([
int(v) if v.isdigit() else local_vars[v]
for v in m.group('args').split(',')])
if fname not in self._functions:
self._functions[fname] = self.extract_function(fname)
return self._functions[fname](argvals)
raise ExtractorError('Unsupported JS expression %r' % expr)
def extract_object(self, objname):
obj = {}
obj_m = re.search(
(r'(?:var\s+)?%s\s*=\s*\{' % re.escape(objname)) +
r'\s*(?P<fields>([a-zA-Z$0-9]+\s*:\s*function\(.*?\)\s*\{.*?\})*)' +
r'\}\s*;',
self.code)
fields = obj_m.group('fields')
# Currently, it only supports function definitions
fields_m = re.finditer(
r'(?P<key>[a-zA-Z$0-9]+)\s*:\s*function'
r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
fields)
for f in fields_m:
argnames = f.group('args').split(',')
obj[f.group('key')] = self.build_function(argnames, f.group('code'))
return obj
def extract_function(self, funcname):
func_m = re.search(
r'''(?x)
(?:function\s+%s|[{;]%s\s*=\s*function)\s*
\((?P<args>[^)]*)\)\s*
\{(?P<code>[^}]+)\}''' % (
re.escape(funcname), re.escape(funcname)),
self.code)
if func_m is None:
raise ExtractorError('Could not find JS function %r' % funcname)
argnames = func_m.group('args').split(',')
return self.build_function(argnames, func_m.group('code'))
def call_function(self, funcname, *args):
f = self.extract_function(funcname)
return f(args)
def build_function(self, argnames, code):
def resf(args):
local_vars = dict(zip(argnames, args))
for stmt in code.split(';'):
res, abort = self.interpret_statement(stmt, local_vars)
if abort:
break
return res
return resf
|
