gh-115627: Fix PySSL_SetError handling SSL_ERROR_SYSCALL (GH-115628)

Python 3.10 changed from using SSL_write() and SSL_read() to SSL_write_ex() and
SSL_read_ex(), but did not update handling of the return value.

Change error handling so that the return value is not examined.
OSError (not EOF) is now returned when retval is 0.

According to *recent* man pages of all functions for which we call
PySSL_SetError, (in OpenSSL 3.0 and 1.1.1), their return value should
be used to determine whether an error happened (i.e. if PySSL_SetError
should be called), but not what kind of error happened (so,
PySSL_SetError shouldn't need retval). To get the error,
we need to use SSL_get_error.

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Co-authored-by: Petr Viktorin <encukou@gmail.com>

Lib/test/test_ssl.py

@@ -2429,16 +2429,18 @@ class ThreadedEchoServer(threading.Thread):
                         self.write(msg.lower())
                 except OSError as e:
                     # handles SSLError and socket errors
+                    if isinstance(e, ConnectionError):
+                        # OpenSSL 1.1.1 sometimes raises
+                        # ConnectionResetError when connection is not
+                        # shut down gracefully.
+                        if self.server.chatty and support.verbose:
+                            print(f" Connection reset by peer: {self.addr}")
+
+                        self.close()
+                        self.running = False
+                        return
                     if self.server.chatty and support.verbose:
-                        if isinstance(e, ConnectionError):
-                            # OpenSSL 1.1.1 sometimes raises
-                            # ConnectionResetError when connection is not
-                            # shut down gracefully.
-                            print(
-                                f" Connection reset by peer: {self.addr}"
-                            )
-                        else:
-                            handle_error("Test server failure:\n")
+                        handle_error("Test server failure:\n")
                     try:
                         self.write(b"ERROR\n")
                     except OSError:
@@ -3166,8 +3168,8 @@ class ThreadedTests(unittest.TestCase):
                                         suppress_ragged_eofs=False) as s:
             s.connect((HOST, server.port))
             with self.assertRaisesRegex(
-                ssl.SSLError,
-                'alert unknown ca|EOF occurred|TLSV1_ALERT_UNKNOWN_CA'
+                OSError,
+                'alert unknown ca|EOF occurred|TLSV1_ALERT_UNKNOWN_CA|closed by the remote host|Connection reset by peer'
             ):
                 # TLS 1.3 perform client cert exchange after handshake
                 s.write(b'data')
@@ -4532,8 +4534,8 @@ class TestPostHandshakeAuth(unittest.TestCase):
                 # test sometimes fails with EOF error. Test passes as long as
                 # server aborts connection with an error.
                 with self.assertRaisesRegex(
-                    ssl.SSLError,
-                    '(certificate required|EOF occurred)'
+                    OSError,
+                    'certificate required|EOF occurred|closed by the remote host|Connection reset by peer'
                 ):
                     # receive CertificateRequest
                     data = s.recv(1024)

Misc/NEWS.d/next/Library/2024-02-18-09-50-31.gh-issue-115627.HGchj0.rst

@@ -0,0 +1,2 @@
+Fix the :mod:`ssl` module error handling of connection terminate by peer.
+It now throws an OSError with the appropriate error code instead of an EOFError.

Modules/_ssl.c

@@ -599,7 +599,7 @@ PySSL_ChainExceptions(PySSLSocket *sslsock) {
 }
 
 static PyObject *
-PySSL_SetError(PySSLSocket *sslsock, int ret, const char *filename, int lineno)
+PySSL_SetError(PySSLSocket *sslsock, const char *filename, int lineno)
 {
     PyObject *type;
     char *errstr = NULL;
@@ -612,7 +612,6 @@ PySSL_SetError(PySSLSocket *sslsock, int ret, const char *filename, int lineno)
     _sslmodulestate *state = get_state_sock(sslsock);
     type = state->PySSLErrorObject;
 
-    assert(ret <= 0);
     e = ERR_peek_last_error();
 
     if (sslsock->ssl != NULL) {
@@ -645,32 +644,21 @@ PySSL_SetError(PySSLSocket *sslsock, int ret, const char *filename, int lineno)
         case SSL_ERROR_SYSCALL:
         {
             if (e == 0) {
-                PySocketSockObject *s = GET_SOCKET(sslsock);
-                if (ret == 0 || (((PyObject *)s) == Py_None)) {
+                /* underlying BIO reported an I/O error */
+                ERR_clear_error();
+#ifdef MS_WINDOWS
+                if (err.ws) {
+                    return PyErr_SetFromWindowsErr(err.ws);
+                }
+#endif
+                if (err.c) {
+                    errno = err.c;
+                    return PyErr_SetFromErrno(PyExc_OSError);
+                }
+                else {
                     p = PY_SSL_ERROR_EOF;
                     type = state->PySSLEOFErrorObject;
                     errstr = "EOF occurred in violation of protocol";
-                } else if (s && ret == -1) {
-                    /* underlying BIO reported an I/O error */
-                    ERR_clear_error();
-#ifdef MS_WINDOWS
-                    if (err.ws) {
-                        return PyErr_SetFromWindowsErr(err.ws);
-                    }
-#endif
-                    if (err.c) {
-                        errno = err.c;
-                        return PyErr_SetFromErrno(PyExc_OSError);
-                    }
-                    else {
-                        p = PY_SSL_ERROR_EOF;
-                        type = state->PySSLEOFErrorObject;
-                        errstr = "EOF occurred in violation of protocol";
-                    }
-                } else { /* possible? */
-                    p = PY_SSL_ERROR_SYSCALL;
-                    type = state->PySSLSyscallErrorObject;
-                    errstr = "Some I/O error occurred";
                 }
             } else {
                 if (ERR_GET_LIB(e) == ERR_LIB_SSL &&
@@ -1030,7 +1018,7 @@ _ssl__SSLSocket_do_handshake_impl(PySSLSocket *self)
              err.ssl == SSL_ERROR_WANT_WRITE);
     Py_XDECREF(sock);
     if (ret < 1)
-        return PySSL_SetError(self, ret, __FILE__, __LINE__);
+        return PySSL_SetError(self, __FILE__, __LINE__);
     if (PySSL_ChainExceptions(self) < 0)
         return NULL;
     Py_RETURN_NONE;
@@ -2437,7 +2425,7 @@ _ssl__SSLSocket_write_impl(PySSLSocket *self, Py_buffer *b)
 
     Py_XDECREF(sock);
     if (retval == 0)
-        return PySSL_SetError(self, retval, __FILE__, __LINE__);
+        return PySSL_SetError(self, __FILE__, __LINE__);
     if (PySSL_ChainExceptions(self) < 0)
         return NULL;
     return PyLong_FromSize_t(count);
@@ -2467,7 +2455,7 @@ _ssl__SSLSocket_pending_impl(PySSLSocket *self)
     self->err = err;
 
     if (count < 0)
-        return PySSL_SetError(self, count, __FILE__, __LINE__);
+        return PySSL_SetError(self, __FILE__, __LINE__);
     else
         return PyLong_FromLong(count);
 }
@@ -2590,7 +2578,7 @@ _ssl__SSLSocket_read_impl(PySSLSocket *self, Py_ssize_t len,
              err.ssl == SSL_ERROR_WANT_WRITE);
 
     if (retval == 0) {
-        PySSL_SetError(self, retval, __FILE__, __LINE__);
+        PySSL_SetError(self, __FILE__, __LINE__);
         goto error;
     }
     if (self->exc != NULL)
@@ -2716,7 +2704,7 @@ _ssl__SSLSocket_shutdown_impl(PySSLSocket *self)
     }
     if (ret < 0) {
         Py_XDECREF(sock);
-        PySSL_SetError(self, ret, __FILE__, __LINE__);
+        PySSL_SetError(self, __FILE__, __LINE__);
         return NULL;
     }
     if (self->exc != NULL)