[3.6] bpo-33871: Fix os.sendfile(), os.writev(), os.readv(), etc. (GH-7931) (GH-8584)

* Fix integer overflow in os.readv(), os.writev() and in os.sendfile()
  with headers or trailers arguments (on BSD-based OSes and MacOS).

* Fix sending the part of the file in os.sendfile() on MacOS.
  Using the trailers argument could cause sending more bytes from
  the input file than was specified.

Thanks Ned Deily for testing on 32-bit MacOS.
(cherry picked from commit 9d57273)

Author: serhiy-storchaka

Lib/test/test_os.py

@@ -2540,12 +2540,14 @@ class Handler(asynchat.async_chat):
             def __init__(self, conn):
                 asynchat.async_chat.__init__(self, conn)
                 self.in_buffer = []
+                self.accumulate = True
                 self.closed = False
                 self.push(b"220 ready\r\n")
 
             def handle_read(self):
                 data = self.recv(4096)
-                self.in_buffer.append(data)
+                if self.accumulate:
+                    self.in_buffer.append(data)
 
             def get_data(self):
                 return b''.join(self.in_buffer)
@@ -2627,6 +2629,8 @@ class TestSendfile(unittest.TestCase):
                                not sys.platform.startswith("sunos")
     requires_headers_trailers = unittest.skipUnless(SUPPORT_HEADERS_TRAILERS,
             'requires headers and trailers support')
+    requires_32b = unittest.skipUnless(sys.maxsize < 2**32,
+            'test is only meaningful on 32-bit builds')
 
     @classmethod
     def setUpClass(cls):
@@ -2657,17 +2661,13 @@ def tearDown(self):
             self.server.stop()
         self.server = None
 
-    def sendfile_wrapper(self, sock, file, offset, nbytes, headers=[], trailers=[]):
+    def sendfile_wrapper(self, *args, **kwargs):
         """A higher level wrapper representing how an application is
         supposed to use sendfile().
         """
-        while 1:
+        while True:
             try:
-                if self.SUPPORT_HEADERS_TRAILERS:
-                    return os.sendfile(sock, file, offset, nbytes, headers,
-                                       trailers)
-                else:
-                    return os.sendfile(sock, file, offset, nbytes)
+                return os.sendfile(*args, **kwargs)
             except OSError as err:
                 if err.errno == errno.ECONNRESET:
                     # disconnected
@@ -2758,20 +2758,22 @@ def test_keywords(self):
     @requires_headers_trailers
     def test_headers(self):
         total_sent = 0
+        expected_data = b"x" * 512 + b"y" * 256 + self.DATA[:-1]
         sent = os.sendfile(self.sockno, self.fileno, 0, 4096,
-                            headers=[b"x" * 512])
+                            headers=[b"x" * 512, b"y" * 256])
+        self.assertLessEqual(sent, 512 + 256 + 4096)
         total_sent += sent
         offset = 4096
-        nbytes = 4096
-        while 1:
+        while total_sent < len(expected_data):
+            nbytes = min(len(expected_data) - total_sent, 4096)
             sent = self.sendfile_wrapper(self.sockno, self.fileno,
                                                     offset, nbytes)
             if sent == 0:
                 break
+            self.assertLessEqual(sent, nbytes)
             total_sent += sent
             offset += sent
 
-        expected_data = b"x" * 512 + self.DATA
         self.assertEqual(total_sent, len(expected_data))
         self.client.close()
         self.server.wait()
@@ -2787,12 +2789,30 @@ def test_trailers(self):
         create_file(TESTFN2, file_data)
 
         with open(TESTFN2, 'rb') as f:
-            os.sendfile(self.sockno, f.fileno(), 0, len(file_data),
-                        trailers=[b"1234"])
+            os.sendfile(self.sockno, f.fileno(), 0, 5,
+                        trailers=[b"123456", b"789"])
             self.client.close()
             self.server.wait()
             data = self.server.handler_instance.get_data()
-            self.assertEqual(data, b"abcdef1234")
+            self.assertEqual(data, b"abcde123456789")
+
+    @requires_headers_trailers
+    @requires_32b
+    def test_headers_overflow_32bits(self):
+        self.server.handler_instance.accumulate = False
+        with self.assertRaises(OSError) as cm:
+            os.sendfile(self.sockno, self.fileno, 0, 0,
+                        headers=[b"x" * 2**16] * 2**15)
+        self.assertEqual(cm.exception.errno, errno.EINVAL)
+
+    @requires_headers_trailers
+    @requires_32b
+    def test_trailers_overflow_32bits(self):
+        self.server.handler_instance.accumulate = False
+        with self.assertRaises(OSError) as cm:
+            os.sendfile(self.sockno, self.fileno, 0, 0,
+                        trailers=[b"x" * 2**16] * 2**15)
+        self.assertEqual(cm.exception.errno, errno.EINVAL)
 
     @requires_headers_trailers
     @unittest.skipUnless(hasattr(os, 'SF_NODISKIO'),

Lib/test/test_posix.py

@@ -19,6 +19,9 @@
 _DUMMY_SYMLINK = os.path.join(tempfile.gettempdir(),
                               support.TESTFN + '-dummy-symlink')
 
+requires_32b = unittest.skipUnless(sys.maxsize < 2**32,
+        'test is only meaningful on 32-bit builds')
+
 class PosixTester(unittest.TestCase):
 
     def setUp(self):
@@ -322,6 +325,17 @@ def test_writev(self):
         finally:
             os.close(fd)
 
+    @unittest.skipUnless(hasattr(posix, 'writev'), "test needs posix.writev()")
+    @requires_32b
+    def test_writev_overflow_32bits(self):
+        fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
+        try:
+            with self.assertRaises(OSError) as cm:
+                os.writev(fd, [b"x" * 2**16] * 2**15)
+            self.assertEqual(cm.exception.errno, errno.EINVAL)
+        finally:
+            os.close(fd)
+
     @unittest.skipUnless(hasattr(posix, 'readv'), "test needs posix.readv()")
     def test_readv(self):
         fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
@@ -344,6 +358,19 @@ def test_readv(self):
         finally:
             os.close(fd)
 
+    @unittest.skipUnless(hasattr(posix, 'readv'), "test needs posix.readv()")
+    @requires_32b
+    def test_readv_overflow_32bits(self):
+        fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
+        try:
+            buf = [bytearray(2**16)] * 2**15
+            with self.assertRaises(OSError) as cm:
+                os.readv(fd, buf)
+            self.assertEqual(cm.exception.errno, errno.EINVAL)
+            self.assertEqual(bytes(buf[0]), b'\0'* 2**16)
+        finally:
+            os.close(fd)
+
     @unittest.skipUnless(hasattr(posix, 'dup'),
                          'test needs posix.dup()')
     def test_dup(self):

Misc/NEWS.d/next/Library/2018-06-26-19-03-56.bpo-33871.XhlrGU.rst

@@ -0,0 +1,3 @@
+Fixed integer overflow in :func:`os.readv` and :func:`os.writev`
+and in :func:`os.sendfile` with *headers* or *trailers* arguments
+(on BSD-based OSes and macOS).

Misc/NEWS.d/next/Security/2018-06-26-19-35-33.bpo-33871.S4HR9n.rst

@@ -0,0 +1,3 @@
+Fixed sending the part of the file in :func:`os.sendfile` on macOS.  Using
+the *trailers* argument could cause sending more bytes from the input file
+than was specified.

Modules/posixmodule.c

@@ -7924,11 +7924,10 @@ os_read_impl(PyObject *module, int fd, Py_ssize_t length)
 
 #if (defined(HAVE_SENDFILE) && (defined(__FreeBSD__) || defined(__DragonFly__) \
     || defined(__APPLE__))) || defined(HAVE_READV) || defined(HAVE_WRITEV)
-static Py_ssize_t
+static int
 iov_setup(struct iovec **iov, Py_buffer **buf, PyObject *seq, Py_ssize_t cnt, int type)
 {
     Py_ssize_t i, j;
-    Py_ssize_t blen, total = 0;
 
     *iov = PyMem_New(struct iovec, cnt);
     if (*iov == NULL) {
@@ -7953,11 +7952,9 @@ iov_setup(struct iovec **iov, Py_buffer **buf, PyObject *seq, Py_ssize_t cnt, in
         }
         Py_DECREF(item);
         (*iov)[i].iov_base = (*buf)[i].buf;
-        blen = (*buf)[i].len;
-        (*iov)[i].iov_len = blen;
-        total += blen;
+        (*iov)[i].iov_len = (*buf)[i].len;
     }
-    return total;
+    return 0;
 
 fail:
     PyMem_Del(*iov);
@@ -8166,12 +8163,20 @@ posix_sendfile(PyObject *self, PyObject *args, PyObject *kwdict)
             }
             if (i > 0) {
                 sf.hdr_cnt = (int)i;
-                i = iov_setup(&(sf.headers), &hbuf,
-                              headers, sf.hdr_cnt, PyBUF_SIMPLE);
-                if (i < 0)
+                if (iov_setup(&(sf.headers), &hbuf,
+                              headers, sf.hdr_cnt, PyBUF_SIMPLE) < 0)
                     return NULL;
 #ifdef __APPLE__
-                sbytes += i;
+                for (i = 0; i < sf.hdr_cnt; i++) {
+                    Py_ssize_t blen = sf.headers[i].iov_len;
+# define OFF_T_MAX 0x7fffffffffffffff
+                    if (sbytes >= OFF_T_MAX - blen) {
+                        PyErr_SetString(PyExc_OverflowError,
+                            "sendfile() header is too large");
+                        return NULL;
+                    }
+                    sbytes += blen;
+                }
 #endif
             }
         }
@@ -8192,13 +8197,9 @@ posix_sendfile(PyObject *self, PyObject *args, PyObject *kwdict)
             }
             if (i > 0) {
                 sf.trl_cnt = (int)i;
-                i = iov_setup(&(sf.trailers), &tbuf,
-                              trailers, sf.trl_cnt, PyBUF_SIMPLE);
-                if (i < 0)
+                if (iov_setup(&(sf.trailers), &tbuf,
+                              trailers, sf.trl_cnt, PyBUF_SIMPLE) < 0)
                     return NULL;
-#ifdef __APPLE__
-                sbytes += i;
-#endif
             }
         }
     }