bpo-35415: validate fileno argument to socket.socket (GH-10917)

https://bugs.python.org/issue35415

Lib/test/test_socket.py

@@ -1700,7 +1700,6 @@ class GeneralModuleTests(unittest.TestCase):
             s.setblocking(False)
             self.assertEqual(s.type, socket.SOCK_STREAM)
 
-    @unittest.skipIf(os.name == 'nt', 'Will not work on Windows')
     def test_unknown_socket_family_repr(self):
         # Test that when created with a family that's not one of the known
         # AF_*/SOCK_* constants, socket.family just returns the number.
@@ -1708,10 +1707,8 @@ class GeneralModuleTests(unittest.TestCase):
         # To do this we fool socket.socket into believing it already has an
         # open fd because on this path it doesn't actually verify the family and
         # type and populates the socket object.
-        #
+        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-        # On Windows this trick won't work, so the test is skipped.
+        fd = sock.detach()
-        fd, path = tempfile.mkstemp()
-        self.addCleanup(os.unlink, path)
         unknown_family = max(socket.AddressFamily.__members__.values()) + 1
 
         unknown_type = max(
@@ -1785,6 +1782,48 @@ class GeneralModuleTests(unittest.TestCase):
             s.bind(os.path.join(tmpdir, 'socket'))
             self._test_socket_fileno(s, socket.AF_UNIX, socket.SOCK_STREAM)
 
+    def test_socket_fileno_rejects_float(self):
+        with self.assertRaisesRegex(TypeError, "integer argument expected"):
+            socket.socket(socket.AF_INET, socket.SOCK_STREAM, fileno=42.5)
+
+    def test_socket_fileno_rejects_other_types(self):
+        with self.assertRaisesRegex(TypeError, "integer is required"):
+            socket.socket(socket.AF_INET, socket.SOCK_STREAM, fileno="foo")
+
+    def test_socket_fileno_rejects_invalid_socket(self):
+        with self.assertRaisesRegex(ValueError, "negative file descriptor"):
+            socket.socket(socket.AF_INET, socket.SOCK_STREAM, fileno=-1)
+
+    @unittest.skipIf(os.name == "nt", "Windows disallows -1 only")
+    def test_socket_fileno_rejects_negative(self):
+        with self.assertRaisesRegex(ValueError, "negative file descriptor"):
+            socket.socket(socket.AF_INET, socket.SOCK_STREAM, fileno=-42)
+
+    def test_socket_fileno_requires_valid_fd(self):
+        WSAENOTSOCK = 10038
+        with self.assertRaises(OSError) as cm:
+            socket.socket(fileno=support.make_bad_fd())
+        self.assertIn(cm.exception.errno, (errno.EBADF, WSAENOTSOCK))
+
+        with self.assertRaises(OSError) as cm:
+            socket.socket(
+                socket.AF_INET,
+                socket.SOCK_STREAM,
+                fileno=support.make_bad_fd())
+        self.assertIn(cm.exception.errno, (errno.EBADF, WSAENOTSOCK))
+
+    def test_socket_fileno_requires_socket_fd(self):
+        with tempfile.NamedTemporaryFile() as afile:
+            with self.assertRaises(OSError):
+                socket.socket(fileno=afile.fileno())
+
+            with self.assertRaises(OSError) as cm:
+                socket.socket(
+                    socket.AF_INET,
+                    socket.SOCK_STREAM,
+                    fileno=afile.fileno())
+            self.assertEqual(cm.exception.errno, errno.ENOTSOCK)
+
 
 @unittest.skipUnless(HAVE_SOCKET_CAN, 'SocketCan required for this test.')
 class BasicCANTest(unittest.TestCase):

Misc/NEWS.d/next/Library/2018-12-06-14-44-21.bpo-35415.-HoK3d.rst

@@ -0,0 +1 @@
+Validate fileno= argument to socket.socket().

Modules/socketmodule.c

@@ -5018,28 +5018,45 @@ sock_initobj(PyObject *self, PyObject *args, PyObject *kwds)
         else
 #endif
         {
-            fd = PyLong_AsSocket_t(fdobj);
+
-            if (fd == (SOCKET_T)(-1) && PyErr_Occurred())
+            if (PyFloat_Check(fdobj)) {
-                return -1;
+                PyErr_SetString(PyExc_TypeError,
-            if (fd == INVALID_SOCKET) {
+                                "integer argument expected, got float");
-                PyErr_SetString(PyExc_ValueError,
-                                "can't use invalid socket value");
                 return -1;
             }
 
-            if (family == -1) {
+            fd = PyLong_AsSocket_t(fdobj);
+            if (fd == (SOCKET_T)(-1) && PyErr_Occurred())
+                return -1;
+#ifdef MS_WINDOWS
+            if (fd == INVALID_SOCKET) {
+#else
+            if (fd < 0) {
+#endif
+                PyErr_SetString(PyExc_ValueError, "negative file descriptor");
+                return -1;
+            }
+
+            /* validate that passed file descriptor is valid and a socket. */
             sock_addr_t addrbuf;
             socklen_t addrlen = sizeof(sock_addr_t);
 
             memset(&addrbuf, 0, addrlen);
             if (getsockname(fd, SAS2SA(&addrbuf), &addrlen) == 0) {
+                if (family == -1) {
                     family = SAS2SA(&addrbuf)->sa_family;
+                }
             } else {
 #ifdef MS_WINDOWS
-                    PyErr_SetFromWindowsErrWithFilename(0, "family");
+                /* getsockname() on an unbound socket is an error on Windows.
+                   Invalid descriptor and not a socket is same error code.
+                   Error out if family must be resolved, or bad descriptor. */
+                if (family == -1 || CHECK_ERRNO(ENOTSOCK)) {
 #else
-                    PyErr_SetFromErrnoWithFilename(PyExc_OSError, "family");
+                /* getsockname() is not supported for SOL_ALG on Linux. */
+                if (family == -1 || CHECK_ERRNO(EBADF) || CHECK_ERRNO(ENOTSOCK)) {
 #endif
+                    set_error();
                     return -1;
                 }
             }
@@ -5052,11 +5069,7 @@ sock_initobj(PyObject *self, PyObject *args, PyObject *kwds)
                 {
                     type = tmp;
                 } else {
-#ifdef MS_WINDOWS
+                    set_error();
-                    PyErr_SetFromWindowsErrWithFilename(0, "type");
-#else
-                    PyErr_SetFromErrnoWithFilename(PyExc_OSError, "type");
-#endif
                     return -1;
                 }
             }
@@ -5072,11 +5085,7 @@ sock_initobj(PyObject *self, PyObject *args, PyObject *kwds)
                 {
                     proto = tmp;
                 } else {
-#ifdef MS_WINDOWS
+                    set_error();
-                    PyErr_SetFromWindowsErrWithFilename(0, "protocol");
-#else
-                    PyErr_SetFromErrnoWithFilename(PyExc_OSError, "protocol");
-#endif
                     return -1;
                 }
             }