1# ===================================================================
2#
3# Copyright (c) 2014, Legrandin <helderijs@gmail.com>
4# All rights reserved.
5#
6# Redistribution and use in source and binary forms, with or without
7# modification, are permitted provided that the following conditions
8# are met:
9#
10# 1. Redistributions of source code must retain the above copyright
11#    notice, this list of conditions and the following disclaimer.
12# 2. Redistributions in binary form must reproduce the above copyright
13#    notice, this list of conditions and the following disclaimer in
14#    the documentation and/or other materials provided with the
15#    distribution.
16#
17# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
20# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
21# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
22# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
23# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
25# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
27# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
28# POSSIBILITY OF SUCH DAMAGE.
29# ===================================================================
30
31import abc
32import sys
33from Crypto.Util.py3compat import byte_string
34from Crypto.Util._file_system import pycryptodome_filename
35
36#
37# List of file suffixes for Python extensions
38#
39if sys.version_info[0] < 3:
40
41    import imp
42    extension_suffixes = []
43    for ext, mod, typ in imp.get_suffixes():
44        if typ == imp.C_EXTENSION:
45            extension_suffixes.append(ext)
46
47else:
48
49    from importlib import machinery
50    extension_suffixes = machinery.EXTENSION_SUFFIXES
51
52# Which types with buffer interface we support (apart from byte strings)
53_buffer_type = (bytearray, memoryview)
54
55
56class _VoidPointer(object):
57    @abc.abstractmethod
58    def get(self):
59        """Return the memory location we point to"""
60        return
61
62    @abc.abstractmethod
63    def address_of(self):
64        """Return a raw pointer to this pointer"""
65        return
66
67
68try:
69    # Starting from v2.18, pycparser (used by cffi for in-line ABI mode)
70    # stops working correctly when PYOPTIMIZE==2 or the parameter -OO is
71    # passed. In that case, we fall back to ctypes.
72    # Note that PyPy ships with an old version of pycparser so we can keep
73    # using cffi there.
74    # See https://github.com/Legrandin/pycryptodome/issues/228
75    if '__pypy__' not in sys.builtin_module_names and sys.flags.optimize == 2:
76        raise ImportError("CFFI with optimize=2 fails due to pycparser bug.")
77
78    from cffi import FFI
79
80    ffi = FFI()
81    null_pointer = ffi.NULL
82    uint8_t_type = ffi.typeof(ffi.new("const uint8_t*"))
83
84    _Array = ffi.new("uint8_t[1]").__class__.__bases__
85
86    def load_lib(name, cdecl):
87        """Load a shared library and return a handle to it.
88
89        @name,  either an absolute path or the name of a library
90                in the system search path.
91
92        @cdecl, the C function declarations.
93        """
94
95        lib = ffi.dlopen(name)
96        ffi.cdef(cdecl)
97        return lib
98
99    def c_ulong(x):
100        """Convert a Python integer to unsigned long"""
101        return x
102
103    c_ulonglong = c_ulong
104    c_uint = c_ulong
105
106    def c_size_t(x):
107        """Convert a Python integer to size_t"""
108        return x
109
110    def create_string_buffer(init_or_size, size=None):
111        """Allocate the given amount of bytes (initially set to 0)"""
112
113        if isinstance(init_or_size, bytes):
114            size = max(len(init_or_size) + 1, size)
115            result = ffi.new("uint8_t[]", size)
116            result[:] = init_or_size
117        else:
118            if size:
119                raise ValueError("Size must be specified once only")
120            result = ffi.new("uint8_t[]", init_or_size)
121        return result
122
123    def get_c_string(c_string):
124        """Convert a C string into a Python byte sequence"""
125        return ffi.string(c_string)
126
127    def get_raw_buffer(buf):
128        """Convert a C buffer into a Python byte sequence"""
129        return ffi.buffer(buf)[:]
130
131    def c_uint8_ptr(data):
132        if isinstance(data, _buffer_type):
133            # This only works for cffi >= 1.7
134            return ffi.cast(uint8_t_type, ffi.from_buffer(data))
135        elif byte_string(data) or isinstance(data, _Array):
136            return data
137        else:
138            raise TypeError("Object type %s cannot be passed to C code" % type(data))
139
140    class VoidPointer_cffi(_VoidPointer):
141        """Model a newly allocated pointer to void"""
142
143        def __init__(self):
144            self._pp = ffi.new("void *[1]")
145
146        def get(self):
147            return self._pp[0]
148
149        def address_of(self):
150            return self._pp
151
152    def VoidPointer():
153        return VoidPointer_cffi()
154
155    backend = "cffi"
156
157except ImportError:
158
159    import ctypes
160    from ctypes import (CDLL, c_void_p, byref, c_ulong, c_ulonglong, c_size_t,
161                        create_string_buffer, c_ubyte, c_uint)
162    from ctypes.util import find_library
163    from ctypes import Array as _Array
164
165    null_pointer = None
166    cached_architecture = []
167
168    def load_lib(name, cdecl):
169        if not cached_architecture:
170            # platform.architecture() creates a subprocess, so caching the
171            # result makes successive imports faster.
172            import platform
173            cached_architecture[:] = platform.architecture()
174        bits, linkage = cached_architecture
175        if "." not in name and not linkage.startswith("Win"):
176            full_name = find_library(name)
177            if full_name is None:
178                raise OSError("Cannot load library '%s'" % name)
179            name = full_name
180        return CDLL(name)
181
182    def get_c_string(c_string):
183        return c_string.value
184
185    def get_raw_buffer(buf):
186        return buf.raw
187
188    # ---- Get raw pointer ---
189
190    _c_ssize_t = ctypes.c_ssize_t
191
192    _PyBUF_SIMPLE = 0
193    _PyObject_GetBuffer = ctypes.pythonapi.PyObject_GetBuffer
194    _PyBuffer_Release = ctypes.pythonapi.PyBuffer_Release
195    _py_object = ctypes.py_object
196    _c_ssize_p = ctypes.POINTER(_c_ssize_t)
197
198    # See Include/object.h for CPython
199    # and https://github.com/pallets/click/blob/master/click/_winconsole.py
200    class _Py_buffer(ctypes.Structure):
201        _fields_ = [
202            ('buf',         c_void_p),
203            ('obj',         ctypes.py_object),
204            ('len',         _c_ssize_t),
205            ('itemsize',    _c_ssize_t),
206            ('readonly',    ctypes.c_int),
207            ('ndim',        ctypes.c_int),
208            ('format',      ctypes.c_char_p),
209            ('shape',       _c_ssize_p),
210            ('strides',     _c_ssize_p),
211            ('suboffsets',  _c_ssize_p),
212            ('internal',    c_void_p)
213        ]
214
215        # Extra field for CPython 2.6/2.7
216        if sys.version_info[0] == 2:
217            _fields_.insert(-1, ('smalltable', _c_ssize_t * 2))
218
219    def c_uint8_ptr(data):
220        if byte_string(data) or isinstance(data, _Array):
221            return data
222        elif isinstance(data, _buffer_type):
223            obj = _py_object(data)
224            buf = _Py_buffer()
225            _PyObject_GetBuffer(obj, byref(buf), _PyBUF_SIMPLE)
226            try:
227                buffer_type = c_ubyte * buf.len
228                return buffer_type.from_address(buf.buf)
229            finally:
230                _PyBuffer_Release(byref(buf))
231        else:
232            raise TypeError("Object type %s cannot be passed to C code" % type(data))
233
234    # ---
235
236    class VoidPointer_ctypes(_VoidPointer):
237        """Model a newly allocated pointer to void"""
238
239        def __init__(self):
240            self._p = c_void_p()
241
242        def get(self):
243            return self._p
244
245        def address_of(self):
246            return byref(self._p)
247
248    def VoidPointer():
249        return VoidPointer_ctypes()
250
251    backend = "ctypes"
252    del ctypes
253
254
255class SmartPointer(object):
256    """Class to hold a non-managed piece of memory"""
257
258    def __init__(self, raw_pointer, destructor):
259        self._raw_pointer = raw_pointer
260        self._destructor = destructor
261
262    def get(self):
263        return self._raw_pointer
264
265    def release(self):
266        rp, self._raw_pointer = self._raw_pointer, None
267        return rp
268
269    def __del__(self):
270        try:
271            if self._raw_pointer is not None:
272                self._destructor(self._raw_pointer)
273                self._raw_pointer = None
274        except AttributeError:
275            pass
276
277
278def load_pycryptodome_raw_lib(name, cdecl):
279    """Load a shared library and return a handle to it.
280
281    @name,  the name of the library expressed as a PyCryptodome module,
282            for instance Crypto.Cipher._raw_cbc.
283
284    @cdecl, the C function declarations.
285    """
286
287    split = name.split(".")
288    dir_comps, basename = split[:-1], split[-1]
289    attempts = []
290    for ext in extension_suffixes:
291        try:
292            filename = basename + ext
293            return load_lib(pycryptodome_filename(dir_comps, filename),
294                            cdecl)
295        except OSError as exp:
296            attempts.append("Trying '%s': %s" % (filename, str(exp)))
297    raise OSError("Cannot load native module '%s': %s" % (name, ", ".join(attempts)))
298
299
300def is_buffer(x):
301    """Return True if object x supports the buffer interface"""
302    return isinstance(x, (bytes, bytearray, memoryview))
303
304
305def is_writeable_buffer(x):
306    return (isinstance(x, bytearray) or
307            (isinstance(x, memoryview) and not x.readonly))
308