fix: do not allow non C-contiguous buffer

They were not allowed in the C-extension but given a bug exists in PyPy, they could be accepted and return the wrong result.

Add a workaround for the PyPy bug and disallow non C-contiguous buffer in the pure python fallback implementation.

The `encodebytes` buffer check is also a bit stricter in the C-extension to mimic CPython behavior.

noxfile.py

@@ -9,6 +9,10 @@
 
 nox.options.sessions = ["lint", "test"]
 
+ALL_CPYTHON = [f"3.{minor}" for minor in range(6, 12 + 1)]
+ALL_PYPY = [f"pypy3.{minor}" for minor in range(8, 10 + 1)]
+ALL_PYTHON = ALL_CPYTHON + ALL_PYPY
+
 
 @nox.session
 def lint(session: nox.Session) -> None:
@@ -46,19 +50,19 @@ def remove_extension(session: nox.Session, in_place: bool = False) -> None:
         assert removed
 
 
-@nox.session(python=["3.6", "3.7", "3.8", "3.9", "3.10"])
+@nox.session(python=ALL_PYTHON)
 def test(session: nox.Session) -> None:
     """Run tests."""
     session.install("-r", "requirements-test.txt")
     # make extension mandatory by exporting CIBUILDWHEEL=1
     env = {"CIBUILDWHEEL": "1"}
     update_env_macos(session, env)
     session.install(".", env=env)
-    session.run("pytest", env=env)
+    session.run("pytest", *session.posargs, env=env)
     # run without extension as well
     env.pop("CIBUILDWHEEL")
     remove_extension(session)
-    session.run("pytest", env=env)
+    session.run("pytest", *session.posargs, env=env)
 
 
 @nox.session(python=["3.8", "3.11"])

src/pybase64/_fallback.py

@@ -35,7 +35,10 @@ def _get_bytes(s: Any) -> Union[bytes, bytearray]:
     if isinstance(s, _bytes_types):
         return s
     try:
-        return memoryview(s).tobytes()
+        mv = memoryview(s)
+        if not mv.c_contiguous:
+            raise BufferError("memoryview: underlying buffer is not C-contiguous")
+        return mv.tobytes()
     except TypeError:
         raise TypeError(
             "argument should be a bytes-like object or ASCII "
@@ -63,24 +66,25 @@ def b64decode(s: Any, altchars: Any = None, validate: bool = False) -> bytes:
 
     A :exc:`binascii.Error` is raised if ``s`` is incorrectly padded.
     """
+    s = _get_bytes(s)
+    if altchars is not None:
+        altchars = _get_bytes(altchars)
     if validate:
         if len(s) % 4 != 0:
             raise BinAsciiError("Incorrect padding")
-        s = _get_bytes(s)
-        if altchars is not None:
-            altchars = _get_bytes(altchars)
-            assert len(altchars) == 2, repr(altchars)
-            map = bytes.maketrans(altchars, b"+/")
-            s = s.translate(map)
         result = builtin_decode(s, altchars, validate=False)
 
         # check length of result vs length of input
-        padding = 0
-        if len(s) > 1 and s[-2] in (b"=", 61):
-            padding = padding + 1
-        if len(s) > 0 and s[-1] in (b"=", 61):
-            padding = padding + 1
-        if 3 * (len(s) / 4) - padding != len(result):
+        expected_len = 0
+        if len(s) > 0:
+            padding = 0
+            # len(s) % 4 != 0 implies len(s) >= 4 here
+            if s[-2] == 61:  # 61 == ord("=")
+                padding += 1
+            if s[-1] == 61:
+                padding += 1
+            expected_len = 3 * (len(s) // 4) - padding
+        if expected_len != len(result):
             raise BinAsciiError("Non-base64 digit found")
         return result
     return builtin_decode(s, altchars, validate=False)
@@ -122,9 +126,11 @@ def b64encode(s: Any, altchars: Any = None) -> bytes:
 
     The result is returned as a :class:`bytes` object.
     """
+    mv = memoryview(s)
+    if not mv.c_contiguous:
+        raise BufferError("memoryview: underlying buffer is not C-contiguous")
     if altchars is not None:
         altchars = _get_bytes(altchars)
-        assert len(altchars) == 2, repr(altchars)
     return builtin_encode(s, altchars)
 
 
@@ -151,4 +157,7 @@ def encodebytes(s: Any) -> bytes:
 
     The result is returned as a :class:`bytes` object.
     """
+    mv = memoryview(s)
+    if not mv.c_contiguous:
+        raise BufferError("memoryview: underlying buffer is not C-contiguous")
     return builtin_encodebytes(s)

src/pybase64/_pybase64.c

@@ -24,6 +24,25 @@ static int libbase64_simd_flag = 0;
 static uint32_t active_simd_flag = 0U;
 static uint32_t simd_flags;
 
+
+/* returns 0 on success */
+static int get_buffer(PyObject* object, Py_buffer* buffer)
+{
+    if (PyObject_GetBuffer(object, buffer, PyBUF_RECORDS_RO | PyBUF_C_CONTIGUOUS) != 0) {
+        return -1;
+    }
+#if defined(PYPY_VERSION)
+    /* PyPy does not respect PyBUF_C_CONTIGUOUS */
+    if (!PyBuffer_IsContiguous(buffer, 'C')) {
+        PyBuffer_Release(buffer);
+        PyErr_Format(PyExc_BufferError, "%R: underlying buffer is not C-contiguous", Py_TYPE(object));
+        return -1;
+    }
+#endif
+    return 0;
+}
+
+
 /* returns 0 on success */
 static int parse_alphabet(PyObject* alphabetObject, char* alphabet, int* useAlphabet)
 {
@@ -49,7 +68,7 @@ static int parse_alphabet(PyObject* alphabetObject, char* alphabet, int* useAlph
         Py_INCREF(alphabetObject);
     }
 
-    if (PyObject_GetBuffer(alphabetObject, &buffer, PyBUF_SIMPLE) < 0) {
+    if (get_buffer(alphabetObject, &buffer) != 0) {
         Py_DECREF(alphabetObject);
         return -1;
     }
@@ -314,7 +333,7 @@ static PyObject* pybase64_encode_impl(PyObject* self, PyObject* args, PyObject *
         return NULL;
     }
 
-    if (PyObject_GetBuffer(in_object, &buffer, PyBUF_SIMPLE) < 0) {
+    if (get_buffer(in_object, &buffer) != 0) {
         return NULL;
     }
 
@@ -434,7 +453,7 @@ static PyObject* pybase64_decode_impl(PyObject* self, PyObject* args, PyObject *
         Py_INCREF(in_object);
     }
     if (source == NULL) {
-        if (PyObject_GetBuffer(in_object, &buffer, PyBUF_SIMPLE) < 0) {
+        if (get_buffer(in_object, &buffer) != 0) {
             Py_DECREF(in_object);
             return NULL;
         }
@@ -467,7 +486,7 @@ static PyObject* pybase64_decode_impl(PyObject* self, PyObject* args, PyObject *
             Py_DECREF(in_object);
         }
         in_object = translate_object;
-        if (PyObject_GetBuffer(in_object, &buffer, PyBUF_SIMPLE) < 0) {
+        if (get_buffer(in_object, &buffer) != 0) {
             Py_DECREF(in_object);
             return NULL;
         }
@@ -605,10 +624,17 @@ static PyObject* pybase64_encodebytes(PyObject* self, PyObject* in_object)
     size_t out_len;
     PyObject* out_object;
 
-    if (PyObject_GetBuffer(in_object, &buffer, PyBUF_SIMPLE) < 0) {
+    if (get_buffer(in_object, &buffer) != 0) {
         return NULL;
     }
-
+    if (((buffer.format[0] != 'c') && (buffer.format[0] != 'b') && (buffer.format[0] != 'B')) || buffer.format[1] != '\0' ) {
+        PyBuffer_Release(&buffer);
+        return PyErr_Format(PyExc_TypeError, "expected single byte elements, not '%s' from %R", buffer.format, Py_TYPE(in_object));
+    }
+    if (buffer.ndim != 1) {
+        PyBuffer_Release(&buffer);
+        return PyErr_Format(PyExc_TypeError, "expected 1-D data, not %d-D data from %R", buffer.ndim, Py_TYPE(in_object));
+    }
     if (buffer.len > (3 * (PY_SSIZE_T_MAX / 4))) {
         PyBuffer_Release(&buffer);
         return PyErr_NoMemory();