[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 9d5727326af53ddd91016d98e16ae7cf829caa95)

5 files changed, 85 insertions, 31 deletions

diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 240b7c4..8339f84 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -2540,12 +2540,14 @@ if threading is not None:
             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 @@ class TestSendfile(unittest.TestCase):
             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 @@ class TestSendfile(unittest.TestCase):
     @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 @@ class TestSendfile(unittest.TestCase):
         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'),
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index eb3ef84..a204377 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -19,6 +19,9 @@ import warnings
 _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 @@ class PosixTester(unittest.TestCase):
         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 @@ class PosixTester(unittest.TestCase):
         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):
diff --git a/Misc/NEWS.d/next/Library/2018-06-26-19-03-56.bpo-33871.XhlrGU.rst b/Misc/NEWS.d/next/Library/2018-06-26-19-03-56.bpo-33871.XhlrGU.rst
new file mode 100644
index 0000000..26210fa
--- /dev/null
+++ b/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).
diff --git a/Misc/NEWS.d/next/Security/2018-06-26-19-35-33.bpo-33871.S4HR9n.rst b/Misc/NEWS.d/next/Security/2018-06-26-19-35-33.bpo-33871.S4HR9n.rst
new file mode 100644
index 0000000..547342c
--- /dev/null
+++ b/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.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 9c05acb..af6b9dc 100644
--- a/Modules/posixmodule.c
+++ b/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
             }
         }
     }