wsgi: better error for chunk read failures

When a client is sending a chunked request body and disconnects
between chunks, wsgi.Input.read() raises a ValueError. That's fine if
you can remember to wrap every single call to read/readline in a
try/except, but it's bad for a higher-level error handler because so
many things raise ValueError.

This adds in a new error class wsgi.ChunkReadError and raises that
instead. It inherits from ValueError so anyone catching ValueError
should continue to work.

eventlet/wsgi.py

@@ -50,6 +50,10 @@ BAD_SOCK = set((errno.EBADF, 10053))
 BROKEN_SOCK = set((errno.EPIPE, errno.ECONNRESET))
 
 
+class ChunkReadError(ValueError):
+    pass
+
+
 # special flag return value for apps
 class _AlreadyHandled(object):
 
@@ -176,7 +180,10 @@ class Input(object):
                     if use_readline and data[-1] == "\n":
                         break
                 else:
+                    try:
                         self.chunk_length = int(rfile.readline().split(b";", 1)[0], 16)
+                    except ValueError as err:
+                        raise ChunkReadError(err)
                     self.position = 0
                     if self.chunk_length == 0:
                         rfile.readline()

tests/wsgi_test.py

@@ -1319,6 +1319,70 @@ class TestHttpd(_TestBase):
         self.assertEqual(read_content.wait(), b'ok')
         assert blew_up[0]
 
+    def test_aborted_chunked_post_between_chunks(self):
+        read_content = event.Event()
+        blew_up = [False]
+
+        def chunk_reader(env, start_response):
+            try:
+                content = env['wsgi.input'].read(1024)
+            except wsgi.ChunkReadError:
+                blew_up[0] = True
+                content = b'ok'
+            except Exception as err:
+                blew_up[0] = True
+                content = b'wrong exception: ' + str(err).encode()
+            read_content.send(content)
+            start_response('200 OK', [('Content-Type', 'text/plain')])
+            return [content]
+        self.site.application = chunk_reader
+        expected_body = 'A' * 0xdb
+        data = "\r\n".join(['PUT /somefile HTTP/1.0',
+                            'Transfer-Encoding: chunked',
+                            '',
+                            'db',
+                            expected_body])
+        # start PUT-ing some chunked data but close prematurely
+        sock = eventlet.connect(('127.0.0.1', self.port))
+        sock.sendall(data.encode())
+        sock.close()
+        # the test passes if we successfully get here, and read all the data
+        # in spite of the early close
+        self.assertEqual(read_content.wait(), b'ok')
+        assert blew_up[0]
+
+    def test_aborted_chunked_post_bad_chunks(self):
+        read_content = event.Event()
+        blew_up = [False]
+
+        def chunk_reader(env, start_response):
+            try:
+                content = env['wsgi.input'].read(1024)
+            except wsgi.ChunkReadError:
+                blew_up[0] = True
+                content = b'ok'
+            except Exception as err:
+                blew_up[0] = True
+                content = b'wrong exception: ' + str(err).encode()
+            read_content.send(content)
+            start_response('200 OK', [('Content-Type', 'text/plain')])
+            return [content]
+        self.site.application = chunk_reader
+        expected_body = 'look here is some data for you'
+        data = "\r\n".join(['PUT /somefile HTTP/1.0',
+                            'Transfer-Encoding: chunked',
+                            '',
+                            'cats',
+                            expected_body])
+        # start PUT-ing some garbage
+        sock = eventlet.connect(('127.0.0.1', self.port))
+        sock.sendall(data.encode())
+        sock.close()
+        # the test passes if we successfully get here, and read all the data
+        # in spite of the early close
+        self.assertEqual(read_content.wait(), b'ok')
+        assert blew_up[0]
+
     def test_exceptions_close_connection(self):
         def wsgi_app(environ, start_response):
             raise RuntimeError("intentional error")