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Issue #19619: Blacklist non-text codecs in method API

Browse source 
str.encode, bytes.decode and bytearray.decode now use an
internal API to throw LookupError for known non-text encodings,
rather than attempting the encoding or decoding operation and
then throwing a TypeError for an unexpected output type.

The latter mechanism remains in place for third party non-text
encodings.
This commit is contained in:
Nick Coghlan 2013-11-22 22:39:36 +10:00
parent 322f5ba0d8
commit c72e4e6dcc
13 changed files with 291 additions and 93 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

27
Include/codecs.h
View file

@ -94,6 +94,33 @@ PyAPI_FUNC(PyObject *) PyCodec_Decode(
const char *errors
);
#ifndef PY_LIMITED_API
/* Text codec specific encoding and decoding API.
Checks the encoding against a list of codecs which do not
implement a str<->bytes encoding before attempting the
operation.
Please note that these APIs are internal and should not
be used in Python C extensions.
*/
PyAPI_FUNC(PyObject *) _PyCodec_EncodeText(
PyObject *object,
const char *encoding,
const char *errors
);
PyAPI_FUNC(PyObject *) _PyCodec_DecodeText(
PyObject *object,
const char *encoding,
const char *errors
);
#endif
/* --- Codec Lookup APIs --------------------------------------------------
All APIs return a codec object with incremented refcount and are

14
Lib/codecs.py
View file

@ -73,9 +73,19 @@
### Codec base classes (defining the API)
class CodecInfo(tuple):
"""Codec details when looking up the codec registry"""
# Private API to allow Python 3.4 to blacklist the known non-Unicode
# codecs in the standard library. A more general mechanism to
# reliably distinguish test encodings from other codecs will hopefully
# be defined for Python 3.5
#
# See http://bugs.python.org/issue19619
_is_text_encoding = True # Assume codecs are text encodings by default
def __new__(cls, encode, decode, streamreader=None, streamwriter=None,
incrementalencoder=None, incrementaldecoder=None, name=None):
incrementalencoder=None, incrementaldecoder=None, name=None,
*, _is_text_encoding=None):
self = tuple.__new__(cls, (encode, decode, streamreader, streamwriter))
self.name = name
self.encode = encode
@ -84,6 +94,8 @@ def __new__(cls, encode, decode, streamreader=None, streamwriter=None,
self.incrementaldecoder = incrementaldecoder
self.streamwriter = streamwriter
self.streamreader = streamreader
if _is_text_encoding is not None:
self._is_text_encoding = _is_text_encoding
return self
def __repr__(self):

1
Lib/encodings/base64_codec.py
View file

@ -52,4 +52,5 @@ def getregentry():
incrementaldecoder=IncrementalDecoder,
streamwriter=StreamWriter,
streamreader=StreamReader,
_is_text_encoding=False,
)

1
Lib/encodings/bz2_codec.py
View file

@ -74,4 +74,5 @@ def getregentry():
incrementaldecoder=IncrementalDecoder,
streamwriter=StreamWriter,
streamreader=StreamReader,
_is_text_encoding=False,
)

1
Lib/encodings/hex_codec.py
View file

@ -52,4 +52,5 @@ def getregentry():
incrementaldecoder=IncrementalDecoder,
streamwriter=StreamWriter,
streamreader=StreamReader,
_is_text_encoding=False,
)

1
Lib/encodings/quopri_codec.py
View file

@ -53,4 +53,5 @@ def getregentry():
incrementaldecoder=IncrementalDecoder,
streamwriter=StreamWriter,
streamreader=StreamReader,
_is_text_encoding=False,
)

1
Lib/encodings/rot_13.py
View file

@ -43,6 +43,7 @@ def getregentry():
incrementaldecoder=IncrementalDecoder,
streamwriter=StreamWriter,
streamreader=StreamReader,
_is_text_encoding=False,
)
### Map

1
Lib/encodings/uu_codec.py
View file

@ -96,4 +96,5 @@ def getregentry():
incrementaldecoder=IncrementalDecoder,
streamreader=StreamReader,
streamwriter=StreamWriter,
_is_text_encoding=False,
)

1
Lib/encodings/zlib_codec.py
View file

@ -74,4 +74,5 @@ def getregentry():
incrementaldecoder=IncrementalDecoder,
streamreader=StreamReader,
streamwriter=StreamWriter,
_is_text_encoding=False,
)

188
Lib/test/test_codecs.py
View file

@ -6,6 +6,7 @@
import sys
import unittest
import warnings
import encodings
from test import support
@ -2381,67 +2382,68 @@ def test_buffer_api_usage(self):
view_decoded = codecs.decode(view, encoding)
self.assertEqual(view_decoded, data)
def test_type_error_for_text_input(self):
def test_text_to_binary_blacklists_binary_transforms(self):
# Check binary -> binary codecs give a good error for str input
bad_input = "bad input type"
for encoding in bytes_transform_encodings:
with self.subTest(encoding=encoding):
msg = "^encoding with '{}' codec failed".format(encoding)
with self.assertRaisesRegex(TypeError, msg) as failure:
fmt = ( "{!r} is not a text encoding; "
"use codecs.encode\(\) to handle arbitrary codecs")
msg = fmt.format(encoding)
with self.assertRaisesRegex(LookupError, msg) as failure:
bad_input.encode(encoding)
self.assertTrue(isinstance(failure.exception.__cause__,
TypeError))
self.assertIsNone(failure.exception.__cause__)
def test_type_error_for_binary_input(self):
# Check str -> str codec gives a good error for binary input
for bad_input in (b"immutable", bytearray(b"mutable")):
with self.subTest(bad_input=bad_input):
msg = "^decoding with 'rot_13' codec failed"
with self.assertRaisesRegex(AttributeError, msg) as failure:
bad_input.decode("rot_13")
self.assertTrue(isinstance(failure.exception.__cause__,
AttributeError))
def test_text_to_binary_blacklists_text_transforms(self):
# Check str.encode gives a good error message for str -> str codecs
msg = (r"^'rot_13' is not a text encoding; "
"use codecs.encode\(\) to handle arbitrary codecs")
with self.assertRaisesRegex(LookupError, msg):
"just an example message".encode("rot_13")
def test_custom_zlib_error_is_wrapped(self):
# Check zlib codec gives a good error for malformed input
msg = "^decoding with 'zlib_codec' codec failed"
with self.assertRaisesRegex(Exception, msg) as failure:
b"hello".decode("zlib_codec")
self.assertTrue(isinstance(failure.exception.__cause__,
type(failure.exception)))
def test_custom_hex_error_is_wrapped(self):
# Check hex codec gives a good error for malformed input
msg = "^decoding with 'hex_codec' codec failed"
with self.assertRaisesRegex(Exception, msg) as failure:
b"hello".decode("hex_codec")
self.assertTrue(isinstance(failure.exception.__cause__,
type(failure.exception)))
# Unfortunately, the bz2 module throws OSError, which the codec
# machinery currently can't wrap :(
def test_bad_decoding_output_type(self):
def test_binary_to_text_blacklists_binary_transforms(self):
# Check bytes.decode and bytearray.decode give a good error
# message for binary -> binary codecs
data = b"encode first to ensure we meet any format restrictions"
for encoding in bytes_transform_encodings:
with self.subTest(encoding=encoding):
encoded_data = codecs.encode(data, encoding)
fmt = ("'{}' decoder returned 'bytes' instead of 'str'; "
"use codecs.decode\(\) to decode to arbitrary types")
fmt = (r"{!r} is not a text encoding; "
"use codecs.decode\(\) to handle arbitrary codecs")
msg = fmt.format(encoding)
with self.assertRaisesRegex(TypeError, msg):
with self.assertRaisesRegex(LookupError, msg):
encoded_data.decode(encoding)
with self.assertRaisesRegex(TypeError, msg):
with self.assertRaisesRegex(LookupError, msg):
bytearray(encoded_data).decode(encoding)
def test_bad_encoding_output_type(self):
# Check str.encode gives a good error message for str -> str codecs
msg = ("'rot_13' encoder returned 'str' instead of 'bytes'; "
"use codecs.encode\(\) to encode to arbitrary types")
with self.assertRaisesRegex(TypeError, msg):
"just an example message".encode("rot_13")
def test_binary_to_text_blacklists_text_transforms(self):
# Check str -> str codec gives a good error for binary input
for bad_input in (b"immutable", bytearray(b"mutable")):
with self.subTest(bad_input=bad_input):
msg = (r"^'rot_13' is not a text encoding; "
"use codecs.decode\(\) to handle arbitrary codecs")
with self.assertRaisesRegex(LookupError, msg) as failure:
bad_input.decode("rot_13")
self.assertIsNone(failure.exception.__cause__)
def test_custom_zlib_error_is_wrapped(self):
# Check zlib codec gives a good error for malformed input
msg = "^decoding with 'zlib_codec' codec failed"
with self.assertRaisesRegex(Exception, msg) as failure:
codecs.decode(b"hello", "zlib_codec")
self.assertIsInstance(failure.exception.__cause__,
type(failure.exception))
def test_custom_hex_error_is_wrapped(self):
# Check hex codec gives a good error for malformed input
msg = "^decoding with 'hex_codec' codec failed"
with self.assertRaisesRegex(Exception, msg) as failure:
codecs.decode(b"hello", "hex_codec")
self.assertIsInstance(failure.exception.__cause__,
type(failure.exception))
# Unfortunately, the bz2 module throws OSError, which the codec
# machinery currently can't wrap :(
# The codec system tries to wrap exceptions in order to ensure the error
@ -2466,27 +2468,44 @@ def setUp(self):
# case finishes by using the test case repr as the codec name
# The codecs module normalizes codec names, although this doesn't
# appear to be formally documented...
self.codec_name = repr(self).lower().replace(" ", "-")
# We also make sure we use a truly unique id for the custom codec
# to avoid issues with the codec cache when running these tests
# multiple times (e.g. when hunting for refleaks)
unique_id = repr(self) + str(id(self))
self.codec_name = encodings.normalize_encoding(unique_id).lower()
# We store the object to raise on the instance because of a bad
# interaction between the codec caching (which means we can't
# recreate the codec entry) and regrtest refleak hunting (which
# runs the same test instance multiple times). This means we
# need to ensure the codecs call back in to the instance to find
# out which exception to raise rather than binding them in a
# closure to an object that may change on the next run
self.obj_to_raise = RuntimeError
def tearDown(self):
_TEST_CODECS.pop(self.codec_name, None)
def set_codec(self, obj_to_raise):
def raise_obj(*args, **kwds):
raise obj_to_raise
codec_info = codecs.CodecInfo(raise_obj, raise_obj,
def set_codec(self, encode, decode):
codec_info = codecs.CodecInfo(encode, decode,
name=self.codec_name)
_TEST_CODECS[self.codec_name] = codec_info
@contextlib.contextmanager
def assertWrapped(self, operation, exc_type, msg):
full_msg = "{} with '{}' codec failed \({}: {}\)".format(
full_msg = r"{} with {!r} codec failed \({}: {}\)".format(
operation, self.codec_name, exc_type.__name__, msg)
with self.assertRaisesRegex(exc_type, full_msg) as caught:
yield caught
self.assertIsInstance(caught.exception.__cause__, exc_type)
def raise_obj(self, *args, **kwds):
# Helper to dynamically change the object raised by a test codec
raise self.obj_to_raise
def check_wrapped(self, obj_to_raise, msg, exc_type=RuntimeError):
self.set_codec(obj_to_raise)
self.obj_to_raise = obj_to_raise
self.set_codec(self.raise_obj, self.raise_obj)
with self.assertWrapped("encoding", exc_type, msg):
"str_input".encode(self.codec_name)
with self.assertWrapped("encoding", exc_type, msg):
@ -2515,23 +2534,17 @@ class MyRuntimeError(RuntimeError):
pass
self.check_wrapped(MyRuntimeError(msg), msg, MyRuntimeError)
@contextlib.contextmanager
def assertNotWrapped(self, operation, exc_type, msg_re, msg=None):
if msg is None:
msg = msg_re
with self.assertRaisesRegex(exc_type, msg) as caught:
yield caught
self.assertEqual(str(caught.exception), msg)
def check_not_wrapped(self, obj_to_raise, msg_re, msg=None):
self.set_codec(obj_to_raise)
with self.assertNotWrapped("encoding", RuntimeError, msg_re, msg):
def check_not_wrapped(self, obj_to_raise, msg):
def raise_obj(*args, **kwds):
raise obj_to_raise
self.set_codec(raise_obj, raise_obj)
with self.assertRaisesRegex(RuntimeError, msg):
"str input".encode(self.codec_name)
with self.assertNotWrapped("encoding", RuntimeError, msg_re, msg):
with self.assertRaisesRegex(RuntimeError, msg):
codecs.encode("str input", self.codec_name)
with self.assertNotWrapped("decoding", RuntimeError, msg_re, msg):
with self.assertRaisesRegex(RuntimeError, msg):
b"bytes input".decode(self.codec_name)
with self.assertNotWrapped("decoding", RuntimeError, msg_re, msg):
with self.assertRaisesRegex(RuntimeError, msg):
codecs.decode(b"bytes input", self.codec_name)
def test_init_override_is_not_wrapped(self):
@ -2550,29 +2563,56 @@ def test_instance_attribute_is_not_wrapped(self):
msg = "This should NOT be wrapped"
exc = RuntimeError(msg)
exc.attr = 1
self.check_not_wrapped(exc, msg)
self.check_not_wrapped(exc, "^{}$".format(msg))
def test_non_str_arg_is_not_wrapped(self):
self.check_not_wrapped(RuntimeError(1), "1")
def test_multiple_args_is_not_wrapped(self):
msg_re = "\('a', 'b', 'c'\)"
msg = "('a', 'b', 'c')"
self.check_not_wrapped(RuntimeError('a', 'b', 'c'), msg_re, msg)
msg_re = r"^\('a', 'b', 'c'\)$"
self.check_not_wrapped(RuntimeError('a', 'b', 'c'), msg_re)
# http://bugs.python.org/issue19609
def test_codec_lookup_failure_not_wrapped(self):
msg = "unknown encoding: %s" % self.codec_name
msg = "^unknown encoding: {}$".format(self.codec_name)
# The initial codec lookup should not be wrapped
with self.assertNotWrapped("encoding", LookupError, msg):
with self.assertRaisesRegex(LookupError, msg):
"str input".encode(self.codec_name)
with self.assertNotWrapped("encoding", LookupError, msg):
with self.assertRaisesRegex(LookupError, msg):
codecs.encode("str input", self.codec_name)
with self.assertNotWrapped("decoding", LookupError, msg):
with self.assertRaisesRegex(LookupError, msg):
b"bytes input".decode(self.codec_name)
with self.assertNotWrapped("decoding", LookupError, msg):
with self.assertRaisesRegex(LookupError, msg):
codecs.decode(b"bytes input", self.codec_name)
def test_unflagged_non_text_codec_handling(self):
# The stdlib non-text codecs are now marked so they're
# pre-emptively skipped by the text model related methods
# However, third party codecs won't be flagged, so we still make
# sure the case where an inappropriate output type is produced is
# handled appropriately
def encode_to_str(*args, **kwds):
return "not bytes!", 0
def decode_to_bytes(*args, **kwds):
return b"not str!", 0
self.set_codec(encode_to_str, decode_to_bytes)
# No input or output type checks on the codecs module functions
encoded = codecs.encode(None, self.codec_name)
self.assertEqual(encoded, "not bytes!")
decoded = codecs.decode(None, self.codec_name)
self.assertEqual(decoded, b"not str!")
# Text model methods should complain
fmt = (r"^{!r} encoder returned 'str' instead of 'bytes'; "
"use codecs.encode\(\) to encode to arbitrary types$")
msg = fmt.format(self.codec_name)
with self.assertRaisesRegex(TypeError, msg):
"str_input".encode(self.codec_name)
fmt = (r"^{!r} decoder returned 'bytes' instead of 'str'; "
"use codecs.decode\(\) to decode to arbitrary types$")
msg = fmt.format(self.codec_name)
with self.assertRaisesRegex(TypeError, msg):
b"bytes input".decode(self.codec_name)
@unittest.skipUnless(sys.platform == 'win32',

6
Misc/NEWS
View file

@ -10,6 +10,12 @@ Projected release date: 2013-11-24
Core and Builtins
-----------------
- Issue #19619: str.encode, bytes.decode and bytearray.decode now use an
internal API to throw LookupError for known non-text encodings, rather
than attempting the encoding or decoding operation and then throwing a
TypeError for an unexpected output type. (The latter mechanism remains
in place for third party non-text encodings)
- Issue #19183: Implement PEP 456 'secure and interchangeable hash algorithm'.
Python now uses SipHash24 on all major platforms.

4
Objects/unicodeobject.c
View file

@ -3044,7 +3044,7 @@ PyUnicode_Decode(const char *s,
buffer = PyMemoryView_FromBuffer(&info);
if (buffer == NULL)
goto onError;
unicode = PyCodec_Decode(buffer, encoding, errors);
unicode = _PyCodec_DecodeText(buffer, encoding, errors);
if (unicode == NULL)
goto onError;
if (!PyUnicode_Check(unicode)) {
@ -3410,7 +3410,7 @@ PyUnicode_AsEncodedString(PyObject *unicode,
}
/* Encode via the codec registry */
v = PyCodec_Encode(unicode, encoding, errors);
v = _PyCodec_EncodeText(unicode, encoding, errors);
if (v == NULL)
return NULL;

138
Python/codecs.c
View file

@ -353,18 +353,15 @@ wrap_codec_error(const char *operation,
errors is passed to the encoder factory as argument if non-NULL. */
PyObject *PyCodec_Encode(PyObject *object,
const char *encoding,
const char *errors)
static PyObject *
_PyCodec_EncodeInternal(PyObject *object,
PyObject *encoder,
const char *encoding,
const char *errors)
{
PyObject *encoder = NULL;
PyObject *args = NULL, *result = NULL;
PyObject *v = NULL;
encoder = PyCodec_Encoder(encoding);
if (encoder == NULL)
goto onError;
args = args_tuple(object, errors);
if (args == NULL)
goto onError;
@ -402,18 +399,15 @@ PyObject *PyCodec_Encode(PyObject *object,
errors is passed to the decoder factory as argument if non-NULL. */
PyObject *PyCodec_Decode(PyObject *object,
const char *encoding,
const char *errors)
static PyObject *
_PyCodec_DecodeInternal(PyObject *object,
PyObject *decoder,
const char *encoding,
const char *errors)
{
PyObject *decoder = NULL;
PyObject *args = NULL, *result = NULL;
PyObject *v;
decoder = PyCodec_Decoder(encoding);
if (decoder == NULL)
goto onError;
args = args_tuple(object, errors);
if (args == NULL)
goto onError;
@ -445,6 +439,118 @@ PyObject *PyCodec_Decode(PyObject *object,
return NULL;
}
/* Generic encoding/decoding API */
PyObject *PyCodec_Encode(PyObject *object,
const char *encoding,
const char *errors)
{
PyObject *encoder;
encoder = PyCodec_Encoder(encoding);
if (encoder == NULL)
return NULL;
return _PyCodec_EncodeInternal(object, encoder, encoding, errors);
}
PyObject *PyCodec_Decode(PyObject *object,
const char *encoding,
const char *errors)
{
PyObject *decoder;
decoder = PyCodec_Decoder(encoding);
if (decoder == NULL)
return NULL;
return _PyCodec_DecodeInternal(object, decoder, encoding, errors);
}
/* Text encoding/decoding API */
static
PyObject *codec_getitem_checked(const char *encoding,
const char *operation_name,
int index)
{
_Py_IDENTIFIER(_is_text_encoding);
PyObject *codec;
PyObject *attr;
PyObject *v;
int is_text_codec;
codec = _PyCodec_Lookup(encoding);
if (codec == NULL)
return NULL;
/* Backwards compatibility: assume any raw tuple describes a text
* encoding, and the same for anything lacking the private
* attribute.
*/
if (!PyTuple_CheckExact(codec)) {
attr = _PyObject_GetAttrId(codec, &PyId__is_text_encoding);
if (attr == NULL) {
if (PyErr_ExceptionMatches(PyExc_AttributeError)) {
PyErr_Clear();
} else {
Py_DECREF(codec);
return NULL;
}
} else {
is_text_codec = PyObject_IsTrue(attr);
Py_DECREF(attr);
if (!is_text_codec) {
Py_DECREF(codec);
PyErr_Format(PyExc_LookupError,
"'%.400s' is not a text encoding; "
"use codecs.%s() to handle arbitrary codecs",
encoding, operation_name);
return NULL;
}
}
}
v = PyTuple_GET_ITEM(codec, index);
Py_DECREF(codec);
Py_INCREF(v);
return v;
}
static PyObject * _PyCodec_TextEncoder(const char *encoding)
{
return codec_getitem_checked(encoding, "encode", 0);
}
static PyObject * _PyCodec_TextDecoder(const char *encoding)
{
return codec_getitem_checked(encoding, "decode", 1);
}
PyObject *_PyCodec_EncodeText(PyObject *object,
const char *encoding,
const char *errors)
{
PyObject *encoder;
encoder = _PyCodec_TextEncoder(encoding);
if (encoder == NULL)
return NULL;
return _PyCodec_EncodeInternal(object, encoder, encoding, errors);
}
PyObject *_PyCodec_DecodeText(PyObject *object,
const char *encoding,
const char *errors)
{
PyObject *decoder;
decoder = _PyCodec_TextDecoder(encoding);
if (decoder == NULL)
return NULL;
return _PyCodec_DecodeInternal(object, decoder, encoding, errors);
}
/* Register the error handling callback function error under the name
name. This function will be called by the codec when it encounters
an unencodable characters/undecodable bytes and doesn't know the