bpo-34759: Fix error handling in ssl 'unwrap()' (GH-9468)

njsmith · miss-islington · commit c0da582b227f · 2018-09-21T21:44:12.000-07:00
OpenSSL follows the convention that whenever you call a function, it returns an error indicator value; and if this value is negative, then you need to go look at the actual error code to see what happened. Commit c6fd1c1 introduced a small mistake in _ssl__SSLSocket_shutdown_impl: instead of checking whether the error indicator was negative, it started checking whether the actual error code was negative, and it turns out that the error codes are never negative. So the effect was that 'unwrap()' lost the ability to raise SSL errors. https://bugs.python.org/issue34759
diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py
@@ -1715,6 +1715,47 @@ def test_private_init(self):
         with self.assertRaisesRegex(TypeError, "public constructor"):
             ssl.SSLObject(bio, bio)
 
+    def test_unwrap(self):
+        client_ctx, server_ctx, hostname = testing_context()
+        c_in = ssl.MemoryBIO()
+        c_out = ssl.MemoryBIO()
+        s_in = ssl.MemoryBIO()
+        s_out = ssl.MemoryBIO()
+        client = client_ctx.wrap_bio(c_in, c_out, server_hostname=hostname)
+        server = server_ctx.wrap_bio(s_in, s_out, server_side=True)
+
+        # Loop on the handshake for a bit to get it settled
+        for _ in range(5):
+            try:
+                client.do_handshake()
+            except ssl.SSLWantReadError:
+                pass
+            if c_out.pending:
+                s_in.write(c_out.read())
+            try:
+                server.do_handshake()
+            except ssl.SSLWantReadError:
+                pass
+            if s_out.pending:
+                c_in.write(s_out.read())
+        # Now the handshakes should be complete (don't raise WantReadError)
+        client.do_handshake()
+        server.do_handshake()
+
+        # Now if we unwrap one side unilaterally, it should send close-notify
+        # and raise WantReadError:
+        with self.assertRaises(ssl.SSLWantReadError):
+            client.unwrap()
+
+        # But server.unwrap() does not raise, because it reads the client's
+        # close-notify:
+        s_in.write(c_out.read())
+        server.unwrap()
+
+        # And now that the client gets the server's close-notify, it doesn't
+        # raise either.
+        c_in.write(s_out.read())
+        client.unwrap()
 
 class SimpleBackgroundTests(unittest.TestCase):
     """Tests that connect to a simple server running in the background"""
diff --git a/Modules/_ssl.c b/Modules/_ssl.c
@@ -2583,9 +2583,9 @@ _ssl__SSLSocket_shutdown_impl(PySSLSocket *self)
             break;
     }
 
-    if (err.ssl < 0) {
+    if (ret < 0) {
         Py_XDECREF(sock);
-        return PySSL_SetError(self, err.ssl, __FILE__, __LINE__);
+        return PySSL_SetError(self, ret, __FILE__, __LINE__);
     }
     if (sock)
         /* It's already INCREF'ed */

Original file line number	Diff line number	Diff line change
`@@ -2583,9 +2583,9 @@ _ssl__SSLSocket_shutdown_impl(PySSLSocket *self)`
`2583`	`2583`	`break;`
`2584`	`2584`	`}`
`2585`	`2585`
`2586`		`- if (err.ssl < 0) {`
	`2586`	`+ if (ret < 0) {`
`2587`	`2587`	`Py_XDECREF(sock);`
`2588`		`- return PySSL_SetError(self, err.ssl, __FILE__, __LINE__);`
	`2588`	`+ return PySSL_SetError(self, ret, __FILE__, __LINE__);`
`2589`	`2589`	`}`
`2590`	`2590`	`if (sock)`
`2591`	`2591`	`/* It's already INCREF'ed */`