Issue #23853: Methods of SSL socket don't reset the socket timeout anymore each

time bytes are received or sent. The socket timeout is now the maximum total
duration of the method.

This change fixes a denial of service if the application is regulary
interrupted by a signal and the signal handler does not raise an exception.

Doc/library/ssl.rst

@@ -830,6 +830,11 @@ SSL Sockets
    .. versionchanged:: 3.5
       The :meth:`sendfile` method was added.
 
+   .. versionchanged:: 3.5
+      The :meth:`shutdown` does not reset the socket timeout each time bytes
+      are received or sent. The socket timeout is now to maximum total duration
+      of the shutdown.
+
 
 SSL sockets also have the following additional methods and attributes:
 
@@ -845,6 +850,11 @@ SSL sockets also have the following additional methods and attributes:
    As at any time a re-negotiation is possible, a call to :meth:`read` can also
    cause write operations.
 
+   .. versionchanged:: 3.5
+      The socket timeout is no more reset each time bytes are received or sent.
+      The socket timeout is now to maximum total duration to read up to *len*
+      bytes.
+
 .. method:: SSLSocket.write(buf)
 
    Write *buf* to the SSL socket and return the number of bytes written. The
@@ -856,6 +866,10 @@ SSL sockets also have the following additional methods and attributes:
    As at any time a re-negotiation is possible, a call to :meth:`write` can
    also cause read operations.
 
+   .. versionchanged:: 3.5
+      The socket timeout is no more reset each time bytes are received or sent.
+      The socket timeout is now to maximum total duration to write *buf*.
+
 .. note::
 
    The :meth:`~SSLSocket.read` and :meth:`~SSLSocket.write` methods are the
@@ -877,6 +891,10 @@ SSL sockets also have the following additional methods and attributes:
       :attr:`~SSLContext.check_hostname` attribute of the socket's
       :attr:`~SSLSocket.context` is true.
 
+   .. versionchanged:: 3.5
+      The socket timeout is no more reset each time bytes are received or sent.
+      The socket timeout is now to maximum total duration of the handshake.
+
 .. method:: SSLSocket.getpeercert(binary_form=False)
 
    If there is no certificate for the peer on the other end of the connection,

Modules/_ssl.c

@@ -223,7 +223,7 @@ static PyTypeObject PySSLMemoryBIO_Type;
 
 static PyObject *PySSL_SSLwrite(PySSLSocket *self, PyObject *args);
 static PyObject *PySSL_SSLread(PySSLSocket *self, PyObject *args);
-static int PySSL_select(PySocketSockObject *s, int writing);
+static int PySSL_select(PySocketSockObject *s, int writing, _PyTime_t timeout);
 static PyObject *PySSL_peercert(PySSLSocket *self, PyObject *args);
 static PyObject *PySSL_cipher(PySSLSocket *self);
 
@@ -248,6 +248,10 @@ typedef enum {
 #define GET_SOCKET(obj) ((obj)->Socket ? \
     (PySocketSockObject *) PyWeakref_GetObject((obj)->Socket) : NULL)
 
+/* If sock is NULL, use a timeout of 0 second */
+#define GET_SOCKET_TIMEOUT(sock) \
+    ((sock != NULL) ? (sock)->sock_timeout : 0)
+
 /*
  * SSL errors.
  */
@@ -565,6 +569,8 @@ static PyObject *PySSL_SSLdo_handshake(PySSLSocket *self)
     int err;
     int sockstate, nonblocking;
     PySocketSockObject *sock = GET_SOCKET(self);
+    _PyTime_t timeout, deadline = 0;
+    int has_timeout;
 
     if (sock) {
         if (((PyObject*)sock) == Py_None) {
@@ -580,6 +586,11 @@ static PyObject *PySSL_SSLdo_handshake(PySSLSocket *self)
         BIO_set_nbio(SSL_get_wbio(self->ssl), nonblocking);
     }
 
+    timeout = GET_SOCKET_TIMEOUT(sock);
+    has_timeout = (timeout > 0);
+    if (has_timeout)
+        deadline = _PyTime_GetMonotonicClock() + timeout;
+
     /* Actually negotiate SSL connection */
     /* XXX If SSL_do_handshake() returns 0, it's also a failure. */
     do {
@@ -591,10 +602,13 @@ static PyObject *PySSL_SSLdo_handshake(PySSLSocket *self)
         if (PyErr_CheckSignals())
             goto error;
 
+        if (has_timeout)
+            timeout = deadline - _PyTime_GetMonotonicClock();
+
         if (err == SSL_ERROR_WANT_READ) {
-            sockstate = PySSL_select(sock, 0);
+            sockstate = PySSL_select(sock, 0, timeout);
         } else if (err == SSL_ERROR_WANT_WRITE) {
-            sockstate = PySSL_select(sock, 1);
+            sockstate = PySSL_select(sock, 1, timeout);
         } else {
             sockstate = SOCKET_OPERATION_OK;
         }
@@ -1611,7 +1625,7 @@ static void PySSL_dealloc(PySSLSocket *self)
  */
 
 static int
-PySSL_select(PySocketSockObject *s, int writing)
+PySSL_select(PySocketSockObject *s, int writing, _PyTime_t timeout)
 {
     int rc;
 #ifdef HAVE_POLL
@@ -1624,10 +1638,14 @@ PySSL_select(PySocketSockObject *s, int writing)
 #endif
 
     /* Nothing to do unless we're in timeout mode (not non-blocking) */
-    if ((s == NULL) || (s->sock_timeout == 0))
+    if ((s == NULL) || (timeout == 0))
         return SOCKET_IS_NONBLOCKING;
-    else if (s->sock_timeout < 0)
+    else if (timeout < 0) {
+        if (s->sock_timeout > 0)
+            return SOCKET_HAS_TIMED_OUT;
+        else
             return SOCKET_IS_BLOCKING;
+    }
 
     /* Guard against closed socket */
     if (s->sock_fd < 0)
@@ -1639,8 +1657,8 @@ PySSL_select(PySocketSockObject *s, int writing)
     pollfd.fd = s->sock_fd;
     pollfd.events = writing ? POLLOUT : POLLIN;
 
-    /* s->sock_timeout is in seconds, timeout in ms */
-    ms = (int)_PyTime_AsMilliseconds(s->sock_timeout, _PyTime_ROUND_CEILING);
+    /* timeout is in seconds, poll() uses milliseconds */
+    ms = (int)_PyTime_AsMilliseconds(timeout, _PyTime_ROUND_CEILING);
     assert(ms <= INT_MAX);
 
     PySSL_BEGIN_ALLOW_THREADS
@@ -1651,7 +1669,7 @@ PySSL_select(PySocketSockObject *s, int writing)
     if (!_PyIsSelectable_fd(s->sock_fd))
         return SOCKET_TOO_LARGE_FOR_SELECT;
 
-    _PyTime_AsTimeval_noraise(s->sock_timeout, &tv, _PyTime_ROUND_CEILING);
+    _PyTime_AsTimeval_noraise(timeout, &tv, _PyTime_ROUND_CEILING);
 
     FD_ZERO(&fds);
     FD_SET(s->sock_fd, &fds);
@@ -1679,6 +1697,8 @@ static PyObject *PySSL_SSLwrite(PySSLSocket *self, PyObject *args)
     int err;
     int nonblocking;
     PySocketSockObject *sock = GET_SOCKET(self);
+    _PyTime_t timeout, deadline = 0;
+    int has_timeout;
 
     if (sock != NULL) {
         if (((PyObject*)sock) == Py_None) {
@@ -1707,7 +1727,12 @@ static PyObject *PySSL_SSLwrite(PySSLSocket *self, PyObject *args)
         BIO_set_nbio(SSL_get_wbio(self->ssl), nonblocking);
     }
 
-    sockstate = PySSL_select(sock, 1);
+    timeout = GET_SOCKET_TIMEOUT(sock);
+    has_timeout = (timeout > 0);
+    if (has_timeout)
+        deadline = _PyTime_GetMonotonicClock() + timeout;
+
+    sockstate = PySSL_select(sock, 1, timeout);
     if (sockstate == SOCKET_HAS_TIMED_OUT) {
         PyErr_SetString(PySocketModule.timeout_error,
                         "The write operation timed out");
@@ -1731,10 +1756,13 @@ static PyObject *PySSL_SSLwrite(PySSLSocket *self, PyObject *args)
         if (PyErr_CheckSignals())
             goto error;
 
+        if (has_timeout)
+            timeout = deadline - _PyTime_GetMonotonicClock();
+
         if (err == SSL_ERROR_WANT_READ) {
-            sockstate = PySSL_select(sock, 0);
+            sockstate = PySSL_select(sock, 0, timeout);
         } else if (err == SSL_ERROR_WANT_WRITE) {
-            sockstate = PySSL_select(sock, 1);
+            sockstate = PySSL_select(sock, 1, timeout);
         } else {
             sockstate = SOCKET_OPERATION_OK;
         }
@@ -1801,6 +1829,8 @@ static PyObject *PySSL_SSLread(PySSLSocket *self, PyObject *args)
     int err;
     int nonblocking;
     PySocketSockObject *sock = GET_SOCKET(self);
+    _PyTime_t timeout, deadline = 0;
+    int has_timeout;
 
     if (sock != NULL) {
         if (((PyObject*)sock) == Py_None) {
@@ -1842,6 +1872,11 @@ static PyObject *PySSL_SSLread(PySSLSocket *self, PyObject *args)
         BIO_set_nbio(SSL_get_wbio(self->ssl), nonblocking);
     }
 
+    timeout = GET_SOCKET_TIMEOUT(sock);
+    has_timeout = (timeout > 0);
+    if (has_timeout)
+        deadline = _PyTime_GetMonotonicClock() + timeout;
+
     do {
         PySSL_BEGIN_ALLOW_THREADS
         count = SSL_read(self->ssl, mem, len);
@@ -1851,10 +1886,13 @@ static PyObject *PySSL_SSLread(PySSLSocket *self, PyObject *args)
         if (PyErr_CheckSignals())
             goto error;
 
+        if (has_timeout)
+            timeout = deadline - _PyTime_GetMonotonicClock();
+
         if (err == SSL_ERROR_WANT_READ) {
-            sockstate = PySSL_select(sock, 0);
+            sockstate = PySSL_select(sock, 0, timeout);
         } else if (err == SSL_ERROR_WANT_WRITE) {
-            sockstate = PySSL_select(sock, 1);
+            sockstate = PySSL_select(sock, 1, timeout);
         } else if (err == SSL_ERROR_ZERO_RETURN &&
                    SSL_get_shutdown(self->ssl) == SSL_RECEIVED_SHUTDOWN)
         {
@@ -1908,6 +1946,8 @@ static PyObject *PySSL_SSLshutdown(PySSLSocket *self)
     int err, ssl_err, sockstate, nonblocking;
     int zeros = 0;
     PySocketSockObject *sock = GET_SOCKET(self);
+    _PyTime_t timeout, deadline = 0;
+    int has_timeout;
 
     if (sock != NULL) {
         /* Guard against closed socket */
@@ -1924,6 +1964,11 @@ static PyObject *PySSL_SSLshutdown(PySSLSocket *self)
         BIO_set_nbio(SSL_get_wbio(self->ssl), nonblocking);
     }
 
+    timeout = GET_SOCKET_TIMEOUT(sock);
+    has_timeout = (timeout > 0);
+    if (has_timeout)
+        deadline = _PyTime_GetMonotonicClock() + timeout;
+
     while (1) {
         PySSL_BEGIN_ALLOW_THREADS
         /* Disable read-ahead so that unwrap can work correctly.
@@ -1953,12 +1998,15 @@ static PyObject *PySSL_SSLshutdown(PySSLSocket *self)
             continue;
         }
 
+        if (has_timeout)
+            timeout = deadline - _PyTime_GetMonotonicClock();
+
         /* Possibly retry shutdown until timeout or failure */
         ssl_err = SSL_get_error(self->ssl, err);
         if (ssl_err == SSL_ERROR_WANT_READ)
-            sockstate = PySSL_select(sock, 0);
+            sockstate = PySSL_select(sock, 0, timeout);
         else if (ssl_err == SSL_ERROR_WANT_WRITE)
-            sockstate = PySSL_select(sock, 1);
+            sockstate = PySSL_select(sock, 1, timeout);
         else
             break;