OpenSSL/ssl/connection.c

/*
 * connection.c
 *
 * Copyright (C) AB Strakt
 * Copyright (C) Jean-Paul Calderone
 * See LICENSE for details.
 *
 * SSL Connection objects and methods.
 * See the file RATIONALE for a short explanation of why this module was written.
 *
 * Reviewed 2001-07-23
 */
#include <Python.h>

#ifndef MS_WINDOWS
#  include <sys/socket.h>
#  include <netinet/in.h>
#  if !(defined(__BEOS__) || defined(__CYGWIN__))
#    include <netinet/tcp.h>
#  endif
#else
#  include <winsock.h>
#  include <wincrypt.h>
#endif

#define SSL_MODULE
#include <openssl/bio.h>
#include <openssl/err.h>
#include "ssl.h"

/**
 * If we are on UNIX, fine, just use PyErr_SetFromErrno. If we are on Windows,
 * apply some black winsock voodoo. This is basically just copied from Python's
 * socketmodule.c
 *
 * Arguments: None
 * Returns:   None
 */
static void
syscall_from_errno(void)
{
#ifdef MS_WINDOWS
    int errnum = WSAGetLastError();
    if (errnum)
    {
        static struct { int num; const char *msg; } *msgp, msgs[] = {
            { WSAEINTR, "Interrupted system call" },
            { WSAEBADF, "Bad file descriptor" },
            { WSAEACCES, "Permission denied" },
            { WSAEFAULT, "Bad address" },
            { WSAEINVAL, "Invalid argument" },
            { WSAEMFILE, "Too many open files" },
            { WSAEWOULDBLOCK, "The socket operation could not complete "
                    "without blocking" },
            { WSAEINPROGRESS, "Operation now in progress" },
            { WSAEALREADY, "Operation already in progress" },
            { WSAENOTSOCK, "Socket operation on non-socket" },
            { WSAEDESTADDRREQ, "Destination address required" },
            { WSAEMSGSIZE, "Message too long" },
            { WSAEPROTOTYPE, "Protocol wrong type for socket" },
            { WSAENOPROTOOPT, "Protocol not available" },
            { WSAEPROTONOSUPPORT, "Protocol not supported" },
            { WSAESOCKTNOSUPPORT, "Socket type not supported" },
            { WSAEOPNOTSUPP, "Operation not supported" },
            { WSAEPFNOSUPPORT, "Protocol family not supported" },
            { WSAEAFNOSUPPORT, "Address family not supported" },
            { WSAEADDRINUSE, "Address already in use" },
            { WSAEADDRNOTAVAIL, "Can't assign requested address" },
            { WSAENETDOWN, "Network is down" },
            { WSAENETUNREACH, "Network is unreachable" },
            { WSAENETRESET, "Network dropped connection on reset" },
            { WSAECONNABORTED, "Software caused connection abort" },
            { WSAECONNRESET, "Connection reset by peer" },
            { WSAENOBUFS, "No buffer space available" },
            { WSAEISCONN, "Socket is already connected" },
            { WSAENOTCONN, "Socket is not connected" },
            { WSAESHUTDOWN, "Can't send after socket shutdown" },
            { WSAETOOMANYREFS, "Too many references: can't splice" },
            { WSAETIMEDOUT, "Operation timed out" },
            { WSAECONNREFUSED, "Connection refused" },
            { WSAELOOP, "Too many levels of symbolic links" },
            { WSAENAMETOOLONG, "File name too long" },
            { WSAEHOSTDOWN, "Host is down" },
            { WSAEHOSTUNREACH, "No route to host" },
            { WSAENOTEMPTY, "Directory not empty" },
            { WSAEPROCLIM, "Too many processes" },
            { WSAEUSERS, "Too many users" },
            { WSAEDQUOT, "Disc quota exceeded" },
            { WSAESTALE, "Stale NFS file handle" },
            { WSAEREMOTE, "Too many levels of remote in path" },
            { WSASYSNOTREADY, "Network subsystem is unvailable" },
            { WSAVERNOTSUPPORTED, "WinSock version is not supported" },
            { WSANOTINITIALISED, "Successful WSAStartup() not yet performed" },
            { WSAEDISCON, "Graceful shutdown in progress" },
            /* Resolver errors */
            { WSAHOST_NOT_FOUND, "No such host is known" },
            { WSATRY_AGAIN, "Host not found, or server failed" },
            { WSANO_RECOVERY, "Unexpected server error encountered" },
            { WSANO_DATA, "Valid name without requested data" },
            { WSANO_ADDRESS, "No address, look for MX record" },
            { 0, NULL }
        };
        PyObject *v;
        const char *msg = "winsock error";

        for (msgp = msgs; msgp->msg; msgp++)
        {
            if (errnum == msgp->num)
            {
                msg = msgp->msg;
                break;
            }
        }

        v = Py_BuildValue("(is)", errnum, msg);
        if (v != NULL)
        {
            PyErr_SetObject(ssl_SysCallError, v);
            Py_DECREF(v);
        }
        return;
    }
#else
    PyErr_SetFromErrno(ssl_SysCallError);
#endif
}

/*
 * Handle errors raised by BIO functions.
 *
 * Arguments: bio - The BIO object
 *            ret - The return value of the BIO_ function.
 * Returns: None, the calling function should return NULL;
 */
static void
handle_bio_errors(BIO* bio, int ret)
{
    if (BIO_should_retry(bio)) {
        if (BIO_should_read(bio)) {
            PyErr_SetNone(ssl_WantReadError);
        } else if (BIO_should_write(bio)) {
            PyErr_SetNone(ssl_WantWriteError);
        } else if (BIO_should_io_special(bio)) {
            /*
             * It's somewhat unclear what this means.  From the OpenSSL source,
             * it seems like it should not be triggered by the memory BIO, so
             * for the time being, this case shouldn't come up.  The SSL BIO
             * (which I think should be named the socket BIO) may trigger this
             * case if its socket is not yet connected or it is busy doing
             * something related to x509.
             */
            PyErr_SetString(PyExc_ValueError, "BIO_should_io_special");
        } else {
            /*
             * I hope this is dead code.  The BIO documentation suggests that
             * one of the above three checks should always be true.
             */
            PyErr_SetString(PyExc_ValueError, "unknown bio failure");
        }
    } else {
        /*
         * If we aren't to retry, it's really an error, so fall back to the
         * normal error reporting code.  However, the BIO interface does not
         * specify a uniform error reporting mechanism.  We can only hope that
         * the code which triggered the error also kindly pushed something onto
         * the error stack.
         */
        exception_from_error_queue(ssl_Error);
    }
}

/*
 * Handle errors raised by SSL I/O functions. NOTE: Not SSL_shutdown ;)
 *
 * Arguments: ssl - The SSL object
 *            err - The return code from SSL_get_error
 *            ret - The return code from the SSL I/O function
 * Returns:   None, the calling function should return NULL
 */
static void
handle_ssl_errors(SSL *ssl, int err, int ret)
{
    switch (err)
    {
	/*
         * Strange as it may seem, ZeroReturn is not an error per se. It means
         * that the SSL Connection has been closed correctly (note, not the
         * transport layer!), i.e. closure alerts have been exchanged. This is
         * an exception since
         *  + There's an SSL "error" code for it
         *  + You have to deal with it in any case, close the transport layer
         *    etc
         */
        case SSL_ERROR_ZERO_RETURN:
            PyErr_SetNone(ssl_ZeroReturnError);
            break;

        /*
         * The WantXYZ exceptions don't mean that there's an error, just that
         * nothing could be read/written just now, maybe because the transport
         * layer would block on the operation, or that there's not enough data
         * available to fill an entire SSL record.
         */
        case SSL_ERROR_WANT_READ:
            PyErr_SetNone(ssl_WantReadError);
            break;

        case SSL_ERROR_WANT_WRITE:
            PyErr_SetNone(ssl_WantWriteError);
            break;

        case SSL_ERROR_WANT_X509_LOOKUP:
            PyErr_SetNone(ssl_WantX509LookupError);
            break;

        case SSL_ERROR_SYSCALL:
            if (ERR_peek_error() == 0)
            {
                if (ret < 0)
                {
                    syscall_from_errno();
                }
                else
                {
                    PyObject *v;

                    v = Py_BuildValue("(is)", -1, "Unexpected EOF");
                    if (v != NULL)
                    {
                        PyErr_SetObject(ssl_SysCallError, v);
                        Py_DECREF(v);
                    }
                }
                break;
            }

	/* NOTE: Fall-through here, we don't want to duplicate code, right? */

        case SSL_ERROR_SSL:
            ;
        default:
	    exception_from_error_queue(ssl_Error);
            break;
    }
}

/*
 * Here be member methods of the Connection "class"
 */

static char ssl_Connection_get_context_doc[] = "\n\
Get session context\n\
\n\
:return: A Context object\n\
";
static PyObject *
ssl_Connection_get_context(ssl_ConnectionObj *self, PyObject *args) {
    if (!PyArg_ParseTuple(args, ":get_context")) {
        return NULL;
    }

    Py_INCREF(self->context);
    return (PyObject *)self->context;
}

static char ssl_Connection_set_context_doc[] = "\n\
Switch this connection to a new session context\n\
\n\
:param context: A :py:class:`Context` instance giving the new session context to use.\n\
\n\
";
static PyObject *
ssl_Connection_set_context(ssl_ConnectionObj *self, PyObject *args) {
    ssl_ContextObj *ctx;
    ssl_ContextObj *old;

    if (!PyArg_ParseTuple(args, "O!:set_context", &ssl_Context_Type, &ctx)) {
        return NULL;
    }

    /* This Connection will hold on to this context now.  Make sure it stays
     * alive.
     */
    Py_INCREF(ctx);

    /* XXX The unit tests don't actually verify that this call is made.
     * They're satisfied if self->context gets updated.
     */
    SSL_set_SSL_CTX(self->ssl, ctx->ctx);

    /* Swap the old out and the new in.
     */
    old = self->context;
    self->context = ctx;

    /* XXX The unit tests don't verify that this reference is dropped.
     */
    Py_DECREF(old);

    Py_INCREF(Py_None);
    return Py_None;
}

static char ssl_Connection_get_servername_doc[] = "\n\
Retrieve the servername extension value if provided in the client hello\n\
message, or None if there wasn't one.\n\
\n\
:return: A byte string giving the server name or :py:data:`None`.\n\
\n\
";
static PyObject *
ssl_Connection_get_servername(ssl_ConnectionObj *self, PyObject *args) {
    int type = TLSEXT_NAMETYPE_host_name;
    const char *name;

    if (!PyArg_ParseTuple(args, ":get_servername")) {
        return NULL;
    }

    name = SSL_get_servername(self->ssl, type);

    if (name == NULL) {
        Py_INCREF(Py_None);
        return Py_None;
    } else {
        return PyBytes_FromString(name);
    }
}


static char ssl_Connection_set_tlsext_host_name_doc[] = "\n\
Set the value of the servername extension to send in the client hello.\n\
\n\
:param name: A byte string giving the name.\n\
\n\
";
static PyObject *
ssl_Connection_set_tlsext_host_name(ssl_ConnectionObj *self, PyObject *args) {
    char *buf;

    if (!PyArg_ParseTuple(args, BYTESTRING_FMT ":set_tlsext_host_name", &buf)) {
        return NULL;
    }

    /* XXX I guess this can fail sometimes? */
    SSL_set_tlsext_host_name(self->ssl, buf);

    Py_INCREF(Py_None);
    return Py_None;
}



static char ssl_Connection_pending_doc[] = "\n\
Get the number of bytes that can be safely read from the connection\n\
\n\
:return: The number of bytes available in the receive buffer.\n\
";
static PyObject *
ssl_Connection_pending(ssl_ConnectionObj *self, PyObject *args) {
    int ret;

    if (!PyArg_ParseTuple(args, ":pending")) {
        return NULL;
    }

    ret = SSL_pending(self->ssl);
    return PyLong_FromLong((long)ret);
}

static char ssl_Connection_bio_write_doc[] = "\n\
When using non-socket connections this function sends\n\
\"dirty\" data that would have traveled in on the network.\n\
\n\
:param buf: The string to put into the memory BIO.\n\
:return: The number of bytes written\n\
";
static PyObject *
ssl_Connection_bio_write(ssl_ConnectionObj *self, PyObject *args)
{
    char *buf;
    int len, ret;

    if (self->into_ssl == NULL) 
    {
            PyErr_SetString(PyExc_TypeError, "Connection sock was not None");
            return NULL;
    }

    if (!PyArg_ParseTuple(args, "s#|i:bio_write", &buf, &len))
        return NULL;

    ret = BIO_write(self->into_ssl, buf, len);

    if (PyErr_Occurred())
    {
        flush_error_queue();
        return NULL;
    }

    if (ret <= 0) {
        /*
         * There was a problem with the BIO_write of some sort.
         */
        handle_bio_errors(self->into_ssl, ret);
        return NULL;
    }

    return PyLong_FromLong((long)ret);
}

static char ssl_Connection_send_doc[] = "\n\
Send data on the connection. NOTE: If you get one of the WantRead,\n\
WantWrite or WantX509Lookup exceptions on this, you have to call the\n\
method again with the SAME buffer.\n\
\n\
:param buf: The string to send\n\
:param flags: (optional) Included for compatibility with the socket\n\
              API, the value is ignored\n\
:return: The number of bytes written\n\
";
static PyObject *
ssl_Connection_send(ssl_ConnectionObj *self, PyObject *args) {
    int len, ret, err, flags;
    char *buf;

#if PY_VERSION_HEX >= 0x02060000
    Py_buffer pbuf;

    if (!PyArg_ParseTuple(args, "s*|i:send", &pbuf, &flags))
        return NULL;

    buf = pbuf.buf;
    len = pbuf.len;
#else

    if (!PyArg_ParseTuple(args, "s#|i:send", &buf, &len, &flags))
        return NULL;
#endif

    MY_BEGIN_ALLOW_THREADS(self->tstate)
    ret = SSL_write(self->ssl, buf, len);
    MY_END_ALLOW_THREADS(self->tstate)

#if PY_VERSION_HEX >= 0x02060000
    PyBuffer_Release(&pbuf);
#endif

    if (PyErr_Occurred())
    {
        flush_error_queue();
        return NULL;
    }

    err = SSL_get_error(self->ssl, ret);
    if (err == SSL_ERROR_NONE)
    {
        return PyLong_FromLong((long)ret);
    }
    else
    {
        handle_ssl_errors(self->ssl, err, ret);
        return NULL;
    }
}

static char ssl_Connection_sendall_doc[] = "\n\
Send \"all\" data on the connection. This calls send() repeatedly until\n\
all data is sent. If an error occurs, it's impossible to tell how much data\n\
has been sent.\n\
\n\
:param buf: The string to send\n\
:param flags: (optional) Included for compatibility with the socket\n\
              API, the value is ignored\n\
:return: The number of bytes written\n\
";
static PyObject *
ssl_Connection_sendall(ssl_ConnectionObj *self, PyObject *args)
{
    char *buf;
    int len, ret, err, flags;
    PyObject *pyret = Py_None;

#if PY_VERSION_HEX >= 0x02060000
    Py_buffer pbuf;

    if (!PyArg_ParseTuple(args, "s*|i:sendall", &pbuf, &flags))
        return NULL;

    buf = pbuf.buf;
    len = pbuf.len;
#else
    if (!PyArg_ParseTuple(args, "s#|i:sendall", &buf, &len, &flags))
        return NULL;
#endif

    do {
        MY_BEGIN_ALLOW_THREADS(self->tstate)
        ret = SSL_write(self->ssl, buf, len);
        MY_END_ALLOW_THREADS(self->tstate)
        if (PyErr_Occurred())
        {
            flush_error_queue();
            pyret = NULL;
            break;
        }
        err = SSL_get_error(self->ssl, ret);
        if (err == SSL_ERROR_NONE)
        {
            buf += ret;
            len -= ret;
        }
        else if (err == SSL_ERROR_SSL || err == SSL_ERROR_SYSCALL ||
                 err == SSL_ERROR_ZERO_RETURN)
        {
            handle_ssl_errors(self->ssl, err, ret);
            pyret = NULL;
            break;
        }
    } while (len > 0);

#if PY_VERSION_HEX >= 0x02060000
    PyBuffer_Release(&pbuf);
#endif

    Py_XINCREF(pyret);
    return pyret;
}

static char ssl_Connection_recv_doc[] = "\n\
Receive data on the connection. NOTE: If you get one of the WantRead,\n\
WantWrite or WantX509Lookup exceptions on this, you have to call the\n\
method again with the SAME buffer.\n\
\n\
:param bufsiz: The maximum number of bytes to read\n\
:param flags: (optional) Included for compatibility with the socket\n\
              API, the value is ignored\n\
:return: The string read from the Connection\n\
";
static PyObject *
ssl_Connection_recv(ssl_ConnectionObj *self, PyObject *args)
{
    int bufsiz, ret, err, flags;
    PyObject *buf;

    if (!PyArg_ParseTuple(args, "i|i:recv", &bufsiz, &flags))
        return NULL;

    buf = PyBytes_FromStringAndSize(NULL, bufsiz);
    if (buf == NULL)
        return NULL;

    MY_BEGIN_ALLOW_THREADS(self->tstate)
    ret = SSL_read(self->ssl, PyBytes_AsString(buf), bufsiz);
    MY_END_ALLOW_THREADS(self->tstate)

    if (PyErr_Occurred())
    {
        Py_DECREF(buf);
        flush_error_queue();
        return NULL;
    }

    err = SSL_get_error(self->ssl, ret);
    if (err == SSL_ERROR_NONE)
    {
        if (ret != bufsiz && _PyBytes_Resize(&buf, ret) < 0)
            return NULL;
        return buf;
    }
    else
    {
        handle_ssl_errors(self->ssl, err, ret);
        Py_DECREF(buf);
        return NULL;
    }
}

static char ssl_Connection_bio_read_doc[] = "\n\
When using non-socket connections this function reads\n\
the \"dirty\" data that would have traveled away on the network.\n\
\n\
:param bufsiz: The maximum number of bytes to read\n\
:return: The string read.\n\
";
static PyObject *
ssl_Connection_bio_read(ssl_ConnectionObj *self, PyObject *args)
{
    int bufsiz, ret;
    PyObject *buf;

    if (self->from_ssl == NULL) 
    {
            PyErr_SetString(PyExc_TypeError, "Connection sock was not None");
            return NULL;
    }

    if (!PyArg_ParseTuple(args, "i:bio_read", &bufsiz))
        return NULL;

    buf = PyBytes_FromStringAndSize(NULL, bufsiz);
    if (buf == NULL)
        return NULL;

    ret = BIO_read(self->from_ssl, PyBytes_AsString(buf), bufsiz);

    if (PyErr_Occurred())
    {
        Py_DECREF(buf);
        flush_error_queue();
        return NULL;
    }

    if (ret <= 0) {
        /*
         * There was a problem with the BIO_read of some sort.
         */
        handle_bio_errors(self->from_ssl, ret);
        Py_DECREF(buf);
        return NULL;
    }

    /*
     * Shrink the string to match the number of bytes we actually read.
     */
    if (ret != bufsiz && _PyBytes_Resize(&buf, ret) < 0)
    {
        Py_DECREF(buf);
        return NULL;
    }
    return buf;
}

static char ssl_Connection_renegotiate_doc[] = "\n\
Renegotiate the session\n\
\n\
:return: True if the renegotiation can be started, false otherwise\n\
";
static PyObject *
ssl_Connection_renegotiate(ssl_ConnectionObj *self, PyObject *args) {
    int ret;

    if (!PyArg_ParseTuple(args, ":renegotiate")) {
        return NULL;
    }

    MY_BEGIN_ALLOW_THREADS(self->tstate);
    ret = SSL_renegotiate(self->ssl);
    MY_END_ALLOW_THREADS(self->tstate);

    if (PyErr_Occurred()) {
        flush_error_queue();
        return NULL;
    }

    return PyLong_FromLong((long)ret);
}

static char ssl_Connection_do_handshake_doc[] = "\n\
Perform an SSL handshake (usually called after renegotiate() or one of\n\
set_*_state()). This can raise the same exceptions as send and recv.\n\
\n\
:return: None.\n\
";
static PyObject *
ssl_Connection_do_handshake(ssl_ConnectionObj *self, PyObject *args)
{
    int ret, err;

    if (!PyArg_ParseTuple(args, ":do_handshake"))
        return NULL;

    MY_BEGIN_ALLOW_THREADS(self->tstate);
    ret = SSL_do_handshake(self->ssl);
    MY_END_ALLOW_THREADS(self->tstate);

    if (PyErr_Occurred())
    {
        flush_error_queue();
        return NULL;
    }

    err = SSL_get_error(self->ssl, ret);
    if (err == SSL_ERROR_NONE)
    {
        Py_INCREF(Py_None);
        return Py_None;
    }
    else
    {
        handle_ssl_errors(self->ssl, err, ret);
        return NULL;
    }
}

#if defined(OPENSSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER >= 0x00907000L
static char ssl_Connection_renegotiate_pending_doc[] = "\n\
Check if there's a renegotiation in progress, it will return false once\n\
a renegotiation is finished.\n\
\n\
:return: Whether there's a renegotiation in progress\n\
";
static PyObject *
ssl_Connection_renegotiate_pending(ssl_ConnectionObj *self, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":renegotiate_pending"))
        return NULL;

    return PyLong_FromLong((long)SSL_renegotiate_pending(self->ssl));
}
#endif

static char ssl_Connection_total_renegotiations_doc[] = "\n\
Find out the total number of renegotiations.\n\
\n\
:return: The number of renegotiations.\n\
";
static PyObject *
ssl_Connection_total_renegotiations(ssl_ConnectionObj *self, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":total_renegotiations"))
        return NULL;

    return PyLong_FromLong(SSL_total_renegotiations(self->ssl));
}

static char ssl_Connection_set_accept_state_doc[] = "\n\
Set the connection to work in server mode. The handshake will be handled\n\
automatically by read/write.\n\
\n\
:return: None\n\
";
static PyObject *
ssl_Connection_set_accept_state(ssl_ConnectionObj *self, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":set_accept_state"))
        return NULL;

    SSL_set_accept_state(self->ssl);

    Py_INCREF(Py_None);
    return Py_None;
}

static char ssl_Connection_set_connect_state_doc[] = "\n\
Set the connection to work in client mode. The handshake will be handled\n\
automatically by read/write.\n\
\n\
:return: None\n\
";
static PyObject *
ssl_Connection_set_connect_state(ssl_ConnectionObj *self, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":set_connect_state"))
        return NULL;

    SSL_set_connect_state(self->ssl);

    Py_INCREF(Py_None);
    return Py_None;
}

static char ssl_Connection_connect_doc[] = "\n\
Connect to remote host and set up client-side SSL\n\
\n\
:param addr: A remote address\n\
:return: What the socket's connect method returns\n\
";
static PyObject *
ssl_Connection_connect(ssl_ConnectionObj *self, PyObject *args)
{
    PyObject *meth, *ret;

    if ((meth = PyObject_GetAttrString(self->socket, "connect")) == NULL)
        return NULL;

    SSL_set_connect_state(self->ssl);

    ret = PyEval_CallObject(meth, args);
    Py_DECREF(meth);
    if (ret == NULL)
        return NULL;

    return ret;
}

static char ssl_Connection_connect_ex_doc[] = "\n\
Connect to remote host and set up client-side SSL. Note that if the socket's\n\
connect_ex method doesn't return 0, SSL won't be initialized.\n\
\n\
:param addr: A remove address\n\
:return: What the socket's connect_ex method returns\n\
";
static PyObject *
ssl_Connection_connect_ex(ssl_ConnectionObj *self, PyObject *args)
{
    PyObject *meth, *ret;

    if ((meth = PyObject_GetAttrString(self->socket, "connect_ex")) == NULL)
        return NULL;

    SSL_set_connect_state(self->ssl);

    ret = PyEval_CallObject(meth, args);
    Py_DECREF(meth);
    return ret;
}

static char ssl_Connection_accept_doc[] = "\n\
Accept incoming connection and set up SSL on it\n\
\n\
:return: A (conn,addr) pair where conn is a Connection and addr is an\n\
         address\n\
";
static PyObject *
ssl_Connection_accept(ssl_ConnectionObj *self, PyObject *args)
{
    PyObject *tuple, *socket, *address, *meth;
    ssl_ConnectionObj *conn;

    if ((meth = PyObject_GetAttrString(self->socket, "accept")) == NULL)
        return NULL;
    tuple = PyEval_CallObject(meth, args);
    Py_DECREF(meth);
    if (tuple == NULL)
        return NULL;

    socket  = PyTuple_GetItem(tuple, 0);
    Py_INCREF(socket);
    address = PyTuple_GetItem(tuple, 1);
    Py_INCREF(address);
    Py_DECREF(tuple);

    conn = ssl_Connection_New(self->context, socket);
    Py_DECREF(socket);
    if (conn == NULL)
    {
        Py_DECREF(address);
        return NULL;
    }

    SSL_set_accept_state(conn->ssl);

    tuple = Py_BuildValue("(OO)", conn, address);

    Py_DECREF(conn);
    Py_DECREF(address);

    return tuple;
}

static char ssl_Connection_bio_shutdown_doc[] = "\n\
When using non-socket connections this function signals end of\n\
data on the input for this connection.\n\
\n\
:return: None\n\
";

static PyObject *
ssl_Connection_bio_shutdown(ssl_ConnectionObj *self, PyObject *args)
{
    if (self->from_ssl == NULL) 
    {
            PyErr_SetString(PyExc_TypeError, "Connection sock was not None");
            return NULL;
    }

    BIO_set_mem_eof_return(self->into_ssl, 0);
    Py_INCREF(Py_None);
    return Py_None;
}



static char ssl_Connection_shutdown_doc[] = "\n\
Send closure alert\n\
\n\
:return: True if the shutdown completed successfully (i.e. both sides\n\
         have sent closure alerts), false otherwise (i.e. you have to\n\
         wait for a ZeroReturnError on a recv() method call\n\
";
static PyObject *
ssl_Connection_shutdown(ssl_ConnectionObj *self, PyObject *args)
{
    int ret;

    if (!PyArg_ParseTuple(args, ":shutdown"))
        return NULL;

    MY_BEGIN_ALLOW_THREADS(self->tstate)
    ret = SSL_shutdown(self->ssl);
    MY_END_ALLOW_THREADS(self->tstate)

    if (PyErr_Occurred())
    {
        flush_error_queue();
        return NULL;
    }

    if (ret < 0)
    {
        exception_from_error_queue(ssl_Error);
        return NULL;
    }
    else if (ret > 0)
    {
        Py_INCREF(Py_True);
        return Py_True;
    }
    else
    {
        Py_INCREF(Py_False);
        return Py_False;
    }
}

static char ssl_Connection_get_cipher_list_doc[] = "\n\
Get the session cipher list\n\
\n\
:return: A list of cipher strings\n\
";
static PyObject *
ssl_Connection_get_cipher_list(ssl_ConnectionObj *self, PyObject *args)
{
    int idx = 0;
    const char *ret;
    PyObject *lst, *item;

    if (!PyArg_ParseTuple(args, ":get_cipher_list"))
        return NULL;

    lst = PyList_New(0);
    while ((ret = SSL_get_cipher_list(self->ssl, idx)) != NULL)
    {
        item = PyText_FromString(ret);
        PyList_Append(lst, item);
        Py_DECREF(item);
        idx++;
    }
    return lst;
}

static char ssl_Connection_get_client_ca_list_doc[] = "\n\
Get CAs whose certificates are suggested for client authentication.\n\
\n\
:return: If this is a server connection, a list of X509Names representing\n\
    the acceptable CAs as set by :py:meth:`OpenSSL.SSL.Context.set_client_ca_list` or\n\
    :py:meth:`OpenSSL.SSL.Context.add_client_ca`.  If this is a client connection,\n\
    the list of such X509Names sent by the server, or an empty list if that\n\
    has not yet happened.\n\
";

static PyObject *
ssl_Connection_get_client_ca_list(ssl_ConnectionObj *self, PyObject *args) {
    STACK_OF(X509_NAME) *CANames;
    PyObject *CAList;
    int i, n;

    if (!PyArg_ParseTuple(args, ":get_client_ca_list")) {
        return NULL;
    }
    CANames = SSL_get_client_CA_list(self->ssl);
    if (CANames == NULL) {
        return PyList_New(0);
    }
    n = sk_X509_NAME_num(CANames);
    CAList = PyList_New(n);
    if (CAList == NULL) {
        return NULL;
    }
    for (i = 0; i < n; i++) {
        X509_NAME *CAName;
        PyObject *CA;

        CAName = X509_NAME_dup(sk_X509_NAME_value(CANames, i));
        if (CAName == NULL) {
            Py_DECREF(CAList);
            exception_from_error_queue(ssl_Error);
            return NULL;
        }
        CA = (PyObject *)new_x509name(CAName, 1);
        if (CA == NULL) {
            X509_NAME_free(CAName);
            Py_DECREF(CAList);
            return NULL;
        }
        if (PyList_SetItem(CAList, i, CA)) {
            Py_DECREF(CA);
            Py_DECREF(CAList);
            return NULL;
        }
    }
    return CAList;
}

static char ssl_Connection_makefile_doc[] = "\n\
The makefile() method is not implemented, since there is no dup semantics\n\
for SSL connections\n\
\n\
:raise NotImplementedError\n\
";
static PyObject *
ssl_Connection_makefile(ssl_ConnectionObj *self, PyObject *args)
{
    PyErr_SetString(PyExc_NotImplementedError, "Cannot make file object of SSL.Connection");
    return NULL;
}

static char ssl_Connection_get_app_data_doc[] = "\n\
Get application data\n\
\n\
:return: The application data\n\
";
static PyObject *
ssl_Connection_get_app_data(ssl_ConnectionObj *self, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":get_app_data"))
        return NULL;

    Py_INCREF(self->app_data);
    return self->app_data;
}

static char ssl_Connection_set_app_data_doc[] = "\n\
Set application data\n\
\n\
:param data - The application data\n\
:return: None\n\
";
static PyObject *
ssl_Connection_set_app_data(ssl_ConnectionObj *self, PyObject *args)
{
    PyObject *data;

    if (!PyArg_ParseTuple(args, "O:set_app_data", &data))
        return NULL;

    Py_DECREF(self->app_data);
    Py_INCREF(data);
    self->app_data = data;

    Py_INCREF(Py_None);
    return Py_None;
}

static char ssl_Connection_get_shutdown_doc[] = "\n\
Get shutdown state\n\
\n\
:return: The shutdown state, a bitvector of SENT_SHUTDOWN, RECEIVED_SHUTDOWN.\n\
";
static PyObject *
ssl_Connection_get_shutdown(ssl_ConnectionObj *self, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":get_shutdown"))
        return NULL;

    return PyLong_FromLong((long)SSL_get_shutdown(self->ssl));
}

static char ssl_Connection_set_shutdown_doc[] = "\n\
Set shutdown state\n\
\n\
:param state - bitvector of SENT_SHUTDOWN, RECEIVED_SHUTDOWN.\n\
:return: None\n\
";
static PyObject *
ssl_Connection_set_shutdown(ssl_ConnectionObj *self, PyObject *args)
{
    int shutdown;

    if (!PyArg_ParseTuple(args, "i:set_shutdown", &shutdown))
        return NULL;

    SSL_set_shutdown(self->ssl, shutdown);
    Py_INCREF(Py_None);
    return Py_None;
}

static char ssl_Connection_state_string_doc[] = "\n\
Get a verbose state description\n\
\n\
:return: A string representing the state\n\
";
static PyObject *
ssl_Connection_state_string(ssl_ConnectionObj *self, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":state_string"))
        return NULL;

    return PyText_FromString(SSL_state_string_long(self->ssl));
}

static char ssl_Connection_client_random_doc[] = "\n\
Get a copy of the client hello nonce.\n\
\n\
:return: A string representing the state\n\
";
static PyObject *
ssl_Connection_client_random(ssl_ConnectionObj *self, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":client_random"))
        return NULL;

    if (self->ssl->session == NULL) {
        Py_INCREF(Py_None);
        return Py_None;
    }
    return PyBytes_FromStringAndSize( (const char *) self->ssl->s3->client_random, SSL3_RANDOM_SIZE);
}

static char ssl_Connection_server_random_doc[] = "\n\
Get a copy of the server hello nonce.\n\
\n\
:return: A string representing the state\n\
";
static PyObject *
ssl_Connection_server_random(ssl_ConnectionObj *self, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":server_random"))
        return NULL;

    if (self->ssl->session == NULL) {
        Py_INCREF(Py_None);
        return Py_None;
    }
    return PyBytes_FromStringAndSize( (const char *) self->ssl->s3->server_random, SSL3_RANDOM_SIZE);
}

static char ssl_Connection_master_key_doc[] = "\n\
Get a copy of the master key.\n\
\n\
:return: A string representing the state\n\
";
static PyObject *
ssl_Connection_master_key(ssl_ConnectionObj *self, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":master_key"))
        return NULL;

    if (self->ssl->session == NULL) {
        Py_INCREF(Py_None);
        return Py_None;
    }
    return PyBytes_FromStringAndSize( (const char *) self->ssl->session->master_key, self->ssl->session->master_key_length);
}

static char ssl_Connection_sock_shutdown_doc[] = "\n\
See shutdown(2)\n\
\n\
:return: What the socket's shutdown() method returns\n\
";
static PyObject *
ssl_Connection_sock_shutdown(ssl_ConnectionObj *self, PyObject *args)
{
    PyObject *meth, *ret;

    if ((meth = PyObject_GetAttrString(self->socket, "shutdown")) == NULL)
        return NULL;
    ret = PyEval_CallObject(meth, args);
    Py_DECREF(meth);
    return ret;
}

static char ssl_Connection_get_peer_certificate_doc[] = "\n\
Retrieve the other side's certificate (if any)\n\
\n\
:return: The peer's certificate\n\
";
static PyObject *
ssl_Connection_get_peer_certificate(ssl_ConnectionObj *self, PyObject *args)
{
    X509 *cert;

    if (!PyArg_ParseTuple(args, ":get_peer_certificate"))
        return NULL;

    cert = SSL_get_peer_certificate(self->ssl);
    if (cert != NULL)
    {
        return (PyObject *)new_x509(cert, 1);
    }
    else
    {
        Py_INCREF(Py_None);
        return Py_None;
    }
}

static char ssl_Connection_get_peer_cert_chain_doc[] = "\n\
Retrieve the other side's certificate (if any)\n\
\n\
:return: A list of X509 instances giving the peer's certificate chain,\n\
         or None if it does not have one.\n\
";
static PyObject *
ssl_Connection_get_peer_cert_chain(ssl_ConnectionObj *self, PyObject *args) {
    STACK_OF(X509) *sk;
    PyObject *chain;
    crypto_X509Obj *cert;
    Py_ssize_t i;

    if (!PyArg_ParseTuple(args, ":get_peer_cert_chain")) {
        return NULL;
    }

    sk = SSL_get_peer_cert_chain(self->ssl);
    if (sk != NULL) {
        chain = PyList_New(sk_X509_num(sk));
        for (i = 0; i < sk_X509_num(sk); i++) {
            cert = new_x509(sk_X509_value(sk, i), 1);
            if (!cert) {
                /* XXX Untested */
                Py_DECREF(chain);
                return NULL;
            }
            CRYPTO_add(&cert->x509->references, 1, CRYPTO_LOCK_X509);
            PyList_SET_ITEM(chain, i, (PyObject *)cert);
        }
        return chain;
    } else {
        Py_INCREF(Py_None);
        return Py_None;
    }

}

static char ssl_Connection_want_read_doc[] = "\n\
Checks if more data has to be read from the transport layer to complete an\n\
operation.\n\
\n\
:return: True iff more data has to be read\n\
";
static PyObject *
ssl_Connection_want_read(ssl_ConnectionObj *self, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":want_read"))
        return NULL;

    return PyLong_FromLong((long)SSL_want_read(self->ssl));
}

static char ssl_Connection_want_write_doc[] = "\n\
Checks if there is data to write to the transport layer to complete an\n\
operation.\n\
\n\
:return: True iff there is data to write\n\
";
static PyObject *
ssl_Connection_want_write(ssl_ConnectionObj *self, PyObject *args)
{
    if (!PyArg_ParseTuple(args, ":want_write"))
        return NULL;

    return PyLong_FromLong((long)SSL_want_write(self->ssl));
}

static char ssl_Connection_get_session_doc[] = "\n\
Returns the Session currently used.\n\
\n\
@return: An instance of :py:class:`OpenSSL.SSL.Session` or :py:obj:`None` if\n\
    no session exists.\n\
";
static PyObject *
ssl_Connection_get_session(ssl_ConnectionObj *self, PyObject *args) {
    ssl_SessionObj *session;
    SSL_SESSION *native_session;

    if (!PyArg_ParseTuple(args, ":get_session")) {
        return NULL;
    }

    native_session = SSL_get1_session(self->ssl);

    if (native_session == NULL) {
        Py_INCREF(Py_None);
        return Py_None;
    }

    session = ssl_Session_from_SSL_SESSION(native_session);
    if (!session) {
        Py_INCREF(Py_None);
        return Py_None;
    }

    return (PyObject*)session;
}

static char ssl_Connection_set_session_doc[] = "\n\
Set the session to be used when the TLS/SSL connection is established.\n\
\n\
:param session: A Session instance representing the session to use.\n\
:returns: None\n\
";
static PyObject *
ssl_Connection_set_session(ssl_ConnectionObj *self, PyObject *args) {
    ssl_SessionObj *session;

    if (!PyArg_ParseTuple(args, "O!:set_session", &ssl_Session_Type, &session)) {
        return NULL;
    }

    if (SSL_set_session(self->ssl, session->session) == 0) {
        /* The only case which leads to this seems to be a mismatch, between
         * this connection and the session, of the SSL method.
         */
        exception_from_error_queue(ssl_Error);
        return NULL;
    }

    Py_INCREF(Py_None);
    return Py_None;
}

/*
 * Member methods in the Connection object
 * ADD_METHOD(name) expands to a correct PyMethodDef declaration
 *   {  'name', (PyCFunction)ssl_Connection_name, METH_VARARGS }
 * for convenience
 * ADD_ALIAS(name,real) creates an "alias" of the ssl_Connection_real
 * function with the name 'name'
 */
#define ADD_METHOD(name)        \
    { #name, (PyCFunction)ssl_Connection_##name, METH_VARARGS, ssl_Connection_##name##_doc }
#define ADD_ALIAS(name,real)    \
    { #name, (PyCFunction)ssl_Connection_##real, METH_VARARGS, ssl_Connection_##real##_doc }
static PyMethodDef ssl_Connection_methods[] =
{
    ADD_METHOD(get_context),
    ADD_METHOD(set_context),
    ADD_METHOD(get_servername),
    ADD_METHOD(set_tlsext_host_name),
    ADD_METHOD(pending),
    ADD_METHOD(send),
    ADD_ALIAS (write, send),
    ADD_METHOD(sendall),
    ADD_METHOD(recv),
    ADD_ALIAS (read, recv),
    ADD_METHOD(bio_read),
    ADD_METHOD(bio_write),
    ADD_METHOD(renegotiate),
    ADD_METHOD(do_handshake),
#if defined(OPENSSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER >= 0x00907000L
    ADD_METHOD(renegotiate_pending),
#endif
    ADD_METHOD(total_renegotiations),
    ADD_METHOD(connect),
    ADD_METHOD(connect_ex),
    ADD_METHOD(accept),
    ADD_METHOD(bio_shutdown),
    ADD_METHOD(shutdown),
    ADD_METHOD(get_cipher_list),
    ADD_METHOD(get_client_ca_list),
    ADD_METHOD(makefile),
    ADD_METHOD(get_app_data),
    ADD_METHOD(set_app_data),
    ADD_METHOD(get_shutdown),
    ADD_METHOD(set_shutdown),
    ADD_METHOD(state_string),
    ADD_METHOD(server_random),
    ADD_METHOD(client_random),
    ADD_METHOD(master_key),
    ADD_METHOD(sock_shutdown),
    ADD_METHOD(get_peer_certificate),
    ADD_METHOD(get_peer_cert_chain),
    ADD_METHOD(want_read),
    ADD_METHOD(want_write),
    ADD_METHOD(set_accept_state),
    ADD_METHOD(set_connect_state),
    ADD_METHOD(get_session),
    ADD_METHOD(set_session),
    { NULL, NULL }
};
#undef ADD_ALIAS
#undef ADD_METHOD

static char ssl_Connection_doc[] = "\n\
Connection(context, socket) -> Connection instance\n\
\n\
Create a new Connection object, using the given OpenSSL.SSL.Context instance\n\
and socket.\n\
\n\
:param context: An SSL Context to use for this connection\n\
:param socket: The socket to use for transport layer\n\
";

/*
 * Initializer used by ssl_Connection_new and ssl_Connection_New.  *Not*
 * tp_init.  This takes an already allocated ssl_ConnectionObj, a context, and
 * a optionally a socket, and glues them all together.
 */
static ssl_ConnectionObj*
ssl_Connection_init(ssl_ConnectionObj *self, ssl_ContextObj *ctx, PyObject *sock) {
    int fd;

    Py_INCREF(ctx);
    self->context = ctx;

    Py_INCREF(sock);
    self->socket = sock;

    self->ssl = NULL;
    self->from_ssl = NULL;
    self->into_ssl = NULL;

    Py_INCREF(Py_None);
    self->app_data = Py_None;

    self->tstate = NULL;

    self->ssl = SSL_new(self->context->ctx);
    SSL_set_app_data(self->ssl, self);

    if (self->socket == Py_None)
    {
        /* If it's not a socket or file, treat it like a memory buffer, 
         * so crazy people can do things like EAP-TLS. */
        self->into_ssl = BIO_new(BIO_s_mem());
        self->from_ssl = BIO_new(BIO_s_mem());
        if (self->into_ssl == NULL || self->from_ssl == NULL)
            goto error;
        SSL_set_bio(self->ssl, self->into_ssl, self->from_ssl);
    } 
    else 
    {
        fd = PyObject_AsFileDescriptor(self->socket);
        if (fd < 0)
        {
            Py_DECREF(self);
            return NULL;
        } 
        else 
        {
            SSL_set_fd(self->ssl, (SOCKET_T)fd);
        }
    }
    return self;

error:
    BIO_free(self->into_ssl);  /* NULL safe */
    BIO_free(self->from_ssl);  /* NULL safe */
    Py_DECREF(self);
    return NULL;
}

/*
 * Constructor for Connection objects
 *
 * Arguments: ctx  - An SSL Context to use for this connection
 *            sock - The socket to use for transport layer
 * Returns:   The newly created Connection object
 */
ssl_ConnectionObj *
ssl_Connection_New(ssl_ContextObj *ctx, PyObject *sock) {
    ssl_ConnectionObj *self;

    self = PyObject_GC_New(ssl_ConnectionObj, &ssl_Connection_Type);
    if (self == NULL) {
        return NULL;
    }
    self = ssl_Connection_init(self, ctx, sock);
    if (self == NULL) {
        return NULL;
    }
    PyObject_GC_Track((PyObject *)self);
    return self;
}

static PyObject*
ssl_Connection_new(PyTypeObject *subtype, PyObject *args, PyObject *kwargs) {
    ssl_ConnectionObj *self;
    ssl_ContextObj *ctx;
    PyObject *sock;
    static char *kwlist[] = {"context", "socket", NULL};

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O!O:Connection", kwlist,
                                     &ssl_Context_Type, &ctx, &sock)) {
        return NULL;
    }

    self = (ssl_ConnectionObj *)subtype->tp_alloc(subtype, 1);
    if (self == NULL) {
        return NULL;
    }

    return (PyObject *)ssl_Connection_init(self, ctx, sock);
}

/*
 * Find attribute
 *
 * Arguments: self - The Connection object
 *            name - The attribute name
 * Returns:   A Python object for the attribute, or NULL if something went
 *            wrong
 */
static PyObject *
ssl_Connection_getattro(ssl_ConnectionObj *self, PyObject *nameobj) {
    PyObject *meth;

    meth = PyObject_GenericGetAttr((PyObject*)self, nameobj);
    if (PyErr_Occurred() && PyErr_ExceptionMatches(PyExc_AttributeError)) {
        PyErr_Clear();
        /* Try looking it up in the "socket" instead. */
        meth = PyObject_GenericGetAttr(self->socket, nameobj);
    }

    return meth;
}

/*
 * Call the visitproc on all contained objects.
 *
 * Arguments: self - The Connection object
 *            visit - Function to call
 *            arg - Extra argument to visit
 * Returns:   0 if all goes well, otherwise the return code from the first
 *            call that gave non-zero result.
 */
static int
ssl_Connection_traverse(ssl_ConnectionObj *self, visitproc visit, void *arg)
{
    int ret = 0;

    if (ret == 0 && self->context != NULL)
        ret = visit((PyObject *)self->context, arg);
    if (ret == 0 && self->socket != NULL)
        ret = visit(self->socket, arg);
    if (ret == 0 && self->app_data != NULL)
        ret = visit(self->app_data, arg);
    return ret;
}

/*
 * Decref all contained objects and zero the pointers.
 *
 * Arguments: self - The Connection object
 * Returns:   Always 0.
 */
static int
ssl_Connection_clear(ssl_ConnectionObj *self)
{
    Py_XDECREF(self->context);
    self->context = NULL;
    Py_XDECREF(self->socket);
    self->socket = NULL;
    Py_XDECREF(self->app_data);
    self->app_data = NULL;
    self->into_ssl = NULL; /* was cleaned up by SSL_free() */
    self->from_ssl = NULL; /* was cleaned up by SSL_free() */
    return 0;
}

/*
 * Deallocate the memory used by the Connection object
 *
 * Arguments: self - The Connection object
 * Returns:   None
 */
static void
ssl_Connection_dealloc(ssl_ConnectionObj *self)
{
    PyObject_GC_UnTrack(self);
    if (self->ssl != NULL)
        SSL_free(self->ssl);
    ssl_Connection_clear(self);
    PyObject_GC_Del(self);
}

PyTypeObject ssl_Connection_Type = {
    PyOpenSSL_HEAD_INIT(&PyType_Type, 0)
    "OpenSSL.SSL.Connection",
    sizeof(ssl_ConnectionObj),
    0,
    (destructor)ssl_Connection_dealloc,
    NULL, /* print */
    NULL, /* tp_getattr */
    NULL, /* setattr */
    NULL, /* compare */
    NULL, /* repr */
    NULL, /* as_number */
    NULL, /* as_sequence */
    NULL, /* as_mapping */
    NULL, /* hash */
    NULL, /* call */
    NULL, /* str */
    (getattrofunc)ssl_Connection_getattro, /* getattro */
    NULL, /* setattro */
    NULL, /* as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
    ssl_Connection_doc, /* doc */
    (traverseproc)ssl_Connection_traverse,
    (inquiry)ssl_Connection_clear,
    NULL, /* tp_richcompare */
    0, /* tp_weaklistoffset */
    NULL, /* tp_iter */
    NULL, /* tp_iternext */
    ssl_Connection_methods, /* tp_methods */
    NULL, /* tp_members */
    NULL, /* tp_getset */
    NULL, /* tp_base */
    NULL, /* tp_dict */
    NULL, /* tp_descr_get */
    NULL, /* tp_descr_set */
    0, /* tp_dictoffset */
    NULL, /* tp_init */
    NULL, /* tp_alloc */
    ssl_Connection_new, /* tp_new */
};


/*
 * Initiailze the Connection part of the SSL sub module
 *
 * Arguments: dict - The OpenSSL.SSL module
 * Returns:   1 for success, 0 otherwise
 */
int
init_ssl_connection(PyObject *module) {

    if (PyType_Ready(&ssl_Connection_Type) < 0) {
        return 0;
    }

    /* PyModule_AddObject steals a reference.
     */
    Py_INCREF((PyObject *)&ssl_Connection_Type);
    if (PyModule_AddObject(module, "Connection", (PyObject *)&ssl_Connection_Type) != 0) {
        return 0;
    }

    /* PyModule_AddObject steals a reference.
     */
    Py_INCREF((PyObject *)&ssl_Connection_Type);
    if (PyModule_AddObject(module, "ConnectionType", (PyObject *)&ssl_Connection_Type) != 0) {
        return 0;
    }

    return 1;
}