_ssl.c

/* SSL socket module

   SSL support based on patches by Brian E Gallew and Laszlo Kovacs.
   Re-worked a bit by Bill Janssen to add server-side support and
   certificate decoding.  Chris Stawarz contributed some non-blocking
   patches.

   This module is imported by ssl.py. It should *not* be used
   directly.

   XXX should partial writes be enabled, SSL_MODE_ENABLE_PARTIAL_WRITE?

   XXX integrate several "shutdown modes" as suggested in
       http://bugs.python.org/issue8108#msg102867 ?
*/

#define PY_SSIZE_T_CLEAN

#include "Python.h"

#ifdef WITH_THREAD
#include "pythread.h"


#define PySSL_BEGIN_ALLOW_THREADS_S(save) \
    do { if (_ssl_locks_count>0) { (save) = PyEval_SaveThread(); } } while (0)
#define PySSL_END_ALLOW_THREADS_S(save) \
    do { if (_ssl_locks_count>0) { PyEval_RestoreThread(save); } } while (0)
#define PySSL_BEGIN_ALLOW_THREADS { \
            PyThreadState *_save = NULL;  \
            PySSL_BEGIN_ALLOW_THREADS_S(_save);
#define PySSL_BLOCK_THREADS     PySSL_END_ALLOW_THREADS_S(_save);
#define PySSL_UNBLOCK_THREADS   PySSL_BEGIN_ALLOW_THREADS_S(_save);
#define PySSL_END_ALLOW_THREADS PySSL_END_ALLOW_THREADS_S(_save); }

#else   /* no WITH_THREAD */

#define PySSL_BEGIN_ALLOW_THREADS_S(save)
#define PySSL_END_ALLOW_THREADS_S(save)
#define PySSL_BEGIN_ALLOW_THREADS
#define PySSL_BLOCK_THREADS
#define PySSL_UNBLOCK_THREADS
#define PySSL_END_ALLOW_THREADS

#endif

/* Include symbols from _socket module */
#include "socketmodule.h"

static PySocketModule_APIObject PySocketModule;

#if defined(HAVE_POLL_H)
#include <poll.h>
#elif defined(HAVE_SYS_POLL_H)
#include <sys/poll.h>
#endif

/* Don't warn about deprecated functions */
#ifdef __GNUC__
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
#endif
#ifdef __clang__
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
#endif

/* Include OpenSSL header files */
#include "openssl/rsa.h"
#include "openssl/crypto.h"
#include "openssl/x509.h"
#include "openssl/x509v3.h"
#include "openssl/pem.h"
#include "openssl/ssl.h"
#include "openssl/err.h"
#include "openssl/rand.h"
#include "openssl/bio.h"

/* SSL error object */
static PyObject *PySSLErrorObject;
static PyObject *PySSLZeroReturnErrorObject;
static PyObject *PySSLWantReadErrorObject;
static PyObject *PySSLWantWriteErrorObject;
static PyObject *PySSLSyscallErrorObject;
static PyObject *PySSLEOFErrorObject;

/* Error mappings */
static PyObject *err_codes_to_names;
static PyObject *err_names_to_codes;
static PyObject *lib_codes_to_names;

struct py_ssl_error_code {
    const char *mnemonic;
    int library, reason;
};
struct py_ssl_library_code {
    const char *library;
    int code;
};

/* Include generated data (error codes) */
#include "_ssl_data.h"

#if (OPENSSL_VERSION_NUMBER >= 0x10100000L) && !defined(LIBRESSL_VERSION_NUMBER)
#  define OPENSSL_VERSION_1_1 1
#endif

/* Openssl comes with TLSv1.1 and TLSv1.2 between 1.0.0h and 1.0.1
    http://www.openssl.org/news/changelog.html
 */
#if OPENSSL_VERSION_NUMBER >= 0x10001000L
# define HAVE_TLSv1_2 1
#else
# define HAVE_TLSv1_2 0
#endif

/* SNI support (client- and server-side) appeared in OpenSSL 1.0.0 and 0.9.8f
 * This includes the SSL_set_SSL_CTX() function.
 */
#ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
# define HAVE_SNI 1
#else
# define HAVE_SNI 0
#endif

#ifdef TLSEXT_TYPE_application_layer_protocol_negotiation
# define HAVE_ALPN
#endif

#ifndef INVALID_SOCKET /* MS defines this */
#define INVALID_SOCKET (-1)
#endif

#ifdef OPENSSL_VERSION_1_1
/* OpenSSL 1.1.0+ */
#ifndef OPENSSL_NO_SSL2
#define OPENSSL_NO_SSL2
#endif
#else /* OpenSSL < 1.1.0 */
#if defined(WITH_THREAD)
#define HAVE_OPENSSL_CRYPTO_LOCK
#endif

#define TLS_method SSLv23_method
#define TLS_client_method SSLv23_client_method
#define TLS_server_method SSLv23_server_method

static int X509_NAME_ENTRY_set(const X509_NAME_ENTRY *ne)
{
    return ne->set;
}

#ifndef OPENSSL_NO_COMP
/* LCOV_EXCL_START */
static int COMP_get_type(const COMP_METHOD *meth)
{
    return meth->type;
}
/* LCOV_EXCL_STOP */
#endif

static pem_password_cb *SSL_CTX_get_default_passwd_cb(SSL_CTX *ctx)
{
    return ctx->default_passwd_callback;
}

static void *SSL_CTX_get_default_passwd_cb_userdata(SSL_CTX *ctx)
{
    return ctx->default_passwd_callback_userdata;
}

static int X509_OBJECT_get_type(X509_OBJECT *x)
{
    return x->type;
}

static X509 *X509_OBJECT_get0_X509(X509_OBJECT *x)
{
    return x->data.x509;
}

static int BIO_up_ref(BIO *b)
{
    CRYPTO_add(&b->references, 1, CRYPTO_LOCK_BIO);
    return 1;
}

static STACK_OF(X509_OBJECT) *X509_STORE_get0_objects(X509_STORE *store) {
    return store->objs;
}

static X509_VERIFY_PARAM *X509_STORE_get0_param(X509_STORE *store)
{
    return store->param;
}

static int
SSL_SESSION_has_ticket(const SSL_SESSION *s)
{
    return (s->tlsext_ticklen > 0) ? 1 : 0;
}

static unsigned long
SSL_SESSION_get_ticket_lifetime_hint(const SSL_SESSION *s)
{
    return s->tlsext_tick_lifetime_hint;
}

#endif /* OpenSSL < 1.1.0 or LibreSSL */


enum py_ssl_error {
    /* these mirror ssl.h */
    PY_SSL_ERROR_NONE,
    PY_SSL_ERROR_SSL,
    PY_SSL_ERROR_WANT_READ,
    PY_SSL_ERROR_WANT_WRITE,
    PY_SSL_ERROR_WANT_X509_LOOKUP,
    PY_SSL_ERROR_SYSCALL,     /* look at error stack/return value/errno */
    PY_SSL_ERROR_ZERO_RETURN,
    PY_SSL_ERROR_WANT_CONNECT,
    /* start of non ssl.h errorcodes */
    PY_SSL_ERROR_EOF,         /* special case of SSL_ERROR_SYSCALL */
    PY_SSL_ERROR_NO_SOCKET,   /* socket has been GC'd */
    PY_SSL_ERROR_INVALID_ERROR_CODE
};

enum py_ssl_server_or_client {
    PY_SSL_CLIENT,
    PY_SSL_SERVER
};

enum py_ssl_cert_requirements {
    PY_SSL_CERT_NONE,
    PY_SSL_CERT_OPTIONAL,
    PY_SSL_CERT_REQUIRED
};

enum py_ssl_version {
    PY_SSL_VERSION_SSL2,
    PY_SSL_VERSION_SSL3=1,
    PY_SSL_VERSION_TLS, /* SSLv23 */
#if HAVE_TLSv1_2
    PY_SSL_VERSION_TLS1,
    PY_SSL_VERSION_TLS1_1,
    PY_SSL_VERSION_TLS1_2,
#else
    PY_SSL_VERSION_TLS1,
#endif
    PY_SSL_VERSION_TLS_CLIENT=0x10,
    PY_SSL_VERSION_TLS_SERVER,
};

#ifdef WITH_THREAD

/* serves as a flag to see whether we've initialized the SSL thread support. */
/* 0 means no, greater than 0 means yes */

static unsigned int _ssl_locks_count = 0;

#endif /* def WITH_THREAD */

/* SSL socket object */

#define X509_NAME_MAXLEN 256

/* SSL_CTX_clear_options() and SSL_clear_options() were first added in
 * OpenSSL 0.9.8m but do not appear in some 0.9.9-dev versions such the
 * 0.9.9 from "May 2008" that NetBSD 5.0 uses. */
#if OPENSSL_VERSION_NUMBER >= 0x009080dfL && OPENSSL_VERSION_NUMBER != 0x00909000L
# define HAVE_SSL_CTX_CLEAR_OPTIONS
#else
# undef HAVE_SSL_CTX_CLEAR_OPTIONS
#endif

/* In case of 'tls-unique' it will be 12 bytes for TLS, 36 bytes for
 * older SSL, but let's be safe */
#define PySSL_CB_MAXLEN 128


typedef struct {
    PyObject_HEAD
    SSL_CTX *ctx;
#ifdef OPENSSL_NPN_NEGOTIATED
    unsigned char *npn_protocols;
    int npn_protocols_len;
#endif
#ifdef HAVE_ALPN
    unsigned char *alpn_protocols;
    int alpn_protocols_len;
#endif
#ifndef OPENSSL_NO_TLSEXT
    PyObject *set_hostname;
#endif
    int check_hostname;
} PySSLContext;

typedef struct {
    PyObject_HEAD
    PyObject *Socket; /* weakref to socket on which we're layered */
    SSL *ssl;
    PySSLContext *ctx; /* weakref to SSL context */
    X509 *peer_cert;
    char shutdown_seen_zero;
    char handshake_done;
    enum py_ssl_server_or_client socket_type;
    PyObject *owner; /* Python level "owner" passed to servername callback */
    PyObject *server_hostname;
} PySSLSocket;

typedef struct {
    PyObject_HEAD
    BIO *bio;
    int eof_written;
} PySSLMemoryBIO;

typedef struct {
    PyObject_HEAD
    SSL_SESSION *session;
    PySSLContext *ctx;
} PySSLSession;

static PyTypeObject PySSLContext_Type;
static PyTypeObject PySSLSocket_Type;
static PyTypeObject PySSLMemoryBIO_Type;
static PyTypeObject PySSLSession_Type;

/*[clinic input]
module _ssl
class _ssl._SSLContext "PySSLContext *" "&PySSLContext_Type"
class _ssl._SSLSocket "PySSLSocket *" "&PySSLSocket_Type"
class _ssl.MemoryBIO "PySSLMemoryBIO *" "&PySSLMemoryBIO_Type"
class _ssl.SSLSession "PySSLSession *" "&PySSLSession_Type"
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=bdc67fafeeaa8109]*/

#include "clinic/_ssl.c.h"

static int PySSL_select(PySocketSockObject *s, int writing, _PyTime_t timeout);


#define PySSLContext_Check(v)   (Py_TYPE(v) == &PySSLContext_Type)
#define PySSLSocket_Check(v)    (Py_TYPE(v) == &PySSLSocket_Type)
#define PySSLMemoryBIO_Check(v)    (Py_TYPE(v) == &PySSLMemoryBIO_Type)
#define PySSLSession_Check(v)   (Py_TYPE(v) == &PySSLSession_Type)

typedef enum {
    SOCKET_IS_NONBLOCKING,
    SOCKET_IS_BLOCKING,
    SOCKET_HAS_TIMED_OUT,
    SOCKET_HAS_BEEN_CLOSED,
    SOCKET_TOO_LARGE_FOR_SELECT,
    SOCKET_OPERATION_OK
} timeout_state;

/* Wrap error strings with filename and line # */
#define ERRSTR1(x,y,z) (x ":" y ": " z)
#define ERRSTR(x) ERRSTR1("_ssl.c", Py_STRINGIFY(__LINE__), x)

/* Get the socket from a PySSLSocket, if it has one */
#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.
 */

PyDoc_STRVAR(SSLError_doc,
"An error occurred in the SSL implementation.");

PyDoc_STRVAR(SSLZeroReturnError_doc,
"SSL/TLS session closed cleanly.");

PyDoc_STRVAR(SSLWantReadError_doc,
"Non-blocking SSL socket needs to read more data\n"
"before the requested operation can be completed.");

PyDoc_STRVAR(SSLWantWriteError_doc,
"Non-blocking SSL socket needs to write more data\n"
"before the requested operation can be completed.");

PyDoc_STRVAR(SSLSyscallError_doc,
"System error when attempting SSL operation.");

PyDoc_STRVAR(SSLEOFError_doc,
"SSL/TLS connection terminated abruptly.");

static PyObject *
SSLError_str(PyOSErrorObject *self)
{
    if (self->strerror != NULL && PyUnicode_Check(self->strerror)) {
        Py_INCREF(self->strerror);
        return self->strerror;
    }
    else
        return PyObject_Str(self->args);
}

static PyType_Slot sslerror_type_slots[] = {
    {Py_tp_base, NULL},  /* Filled out in module init as it's not a constant */
    {Py_tp_doc, SSLError_doc},
    {Py_tp_str, SSLError_str},
    {0, 0},
};

static PyType_Spec sslerror_type_spec = {
    "ssl.SSLError",
    sizeof(PyOSErrorObject),
    0,
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
    sslerror_type_slots
};

static void
fill_and_set_sslerror(PyObject *type, int ssl_errno, const char *errstr,
                      int lineno, unsigned long errcode)
{
    PyObject *err_value = NULL, *reason_obj = NULL, *lib_obj = NULL;
    PyObject *init_value, *msg, *key;
    _Py_IDENTIFIER(reason);
    _Py_IDENTIFIER(library);

    if (errcode != 0) {
        int lib, reason;

        lib = ERR_GET_LIB(errcode);
        reason = ERR_GET_REASON(errcode);
        key = Py_BuildValue("ii", lib, reason);
        if (key == NULL)
            goto fail;
        reason_obj = PyDict_GetItem(err_codes_to_names, key);
        Py_DECREF(key);
        if (reason_obj == NULL) {
            /* XXX if reason < 100, it might reflect a library number (!!) */
            PyErr_Clear();
        }
        key = PyLong_FromLong(lib);
        if (key == NULL)
            goto fail;
        lib_obj = PyDict_GetItem(lib_codes_to_names, key);
        Py_DECREF(key);
        if (lib_obj == NULL) {
            PyErr_Clear();
        }
        if (errstr == NULL)
            errstr = ERR_reason_error_string(errcode);
    }
    if (errstr == NULL)
        errstr = "unknown error";

    if (reason_obj && lib_obj)
        msg = PyUnicode_FromFormat("[%S: %S] %s (_ssl.c:%d)",
                                   lib_obj, reason_obj, errstr, lineno);
    else if (lib_obj)
        msg = PyUnicode_FromFormat("[%S] %s (_ssl.c:%d)",
                                   lib_obj, errstr, lineno);
    else
        msg = PyUnicode_FromFormat("%s (_ssl.c:%d)", errstr, lineno);
    if (msg == NULL)
        goto fail;

    init_value = Py_BuildValue("iN", ssl_errno, msg);
    if (init_value == NULL)
        goto fail;

    err_value = PyObject_CallObject(type, init_value);
    Py_DECREF(init_value);
    if (err_value == NULL)
        goto fail;

    if (reason_obj == NULL)
        reason_obj = Py_None;
    if (_PyObject_SetAttrId(err_value, &PyId_reason, reason_obj))
        goto fail;
    if (lib_obj == NULL)
        lib_obj = Py_None;
    if (_PyObject_SetAttrId(err_value, &PyId_library, lib_obj))
        goto fail;
    PyErr_SetObject(type, err_value);
fail:
    Py_XDECREF(err_value);
}

static PyObject *
PySSL_SetError(PySSLSocket *obj, int ret, const char *filename, int lineno)
{
    PyObject *type = PySSLErrorObject;
    char *errstr = NULL;
    int err;
    enum py_ssl_error p = PY_SSL_ERROR_NONE;
    unsigned long e = 0;

    assert(ret <= 0);
    e = ERR_peek_last_error();

    if (obj->ssl != NULL) {
        err = SSL_get_error(obj->ssl, ret);

        switch (err) {
        case SSL_ERROR_ZERO_RETURN:
            errstr = "TLS/SSL connection has been closed (EOF)";
            type = PySSLZeroReturnErrorObject;
            p = PY_SSL_ERROR_ZERO_RETURN;
            break;
        case SSL_ERROR_WANT_READ:
            errstr = "The operation did not complete (read)";
            type = PySSLWantReadErrorObject;
            p = PY_SSL_ERROR_WANT_READ;
            break;
        case SSL_ERROR_WANT_WRITE:
            p = PY_SSL_ERROR_WANT_WRITE;
            type = PySSLWantWriteErrorObject;
            errstr = "The operation did not complete (write)";
            break;
        case SSL_ERROR_WANT_X509_LOOKUP:
            p = PY_SSL_ERROR_WANT_X509_LOOKUP;
            errstr = "The operation did not complete (X509 lookup)";
            break;
        case SSL_ERROR_WANT_CONNECT:
            p = PY_SSL_ERROR_WANT_CONNECT;
            errstr = "The operation did not complete (connect)";
            break;
        case SSL_ERROR_SYSCALL:
        {
            if (e == 0) {
                PySocketSockObject *s = GET_SOCKET(obj);
                if (ret == 0 || (((PyObject *)s) == Py_None)) {
                    p = PY_SSL_ERROR_EOF;
                    type = PySSLEOFErrorObject;
                    errstr = "EOF occurred in violation of protocol";
                } else if (s && ret == -1) {
                    /* underlying BIO reported an I/O error */
                    Py_INCREF(s);
                    ERR_clear_error();
                    s->errorhandler();
                    Py_DECREF(s);
                    return NULL;
                } else { /* possible? */
                    p = PY_SSL_ERROR_SYSCALL;
                    type = PySSLSyscallErrorObject;
                    errstr = "Some I/O error occurred";
                }
            } else {
                p = PY_SSL_ERROR_SYSCALL;
            }
            break;
        }
        case SSL_ERROR_SSL:
        {
            p = PY_SSL_ERROR_SSL;
            if (e == 0)
                /* possible? */
                errstr = "A failure in the SSL library occurred";
            break;
        }
        default:
            p = PY_SSL_ERROR_INVALID_ERROR_CODE;
            errstr = "Invalid error code";
        }
    }
    fill_and_set_sslerror(type, p, errstr, lineno, e);
    ERR_clear_error();
    return NULL;
}

static PyObject *
_setSSLError (const char *errstr, int errcode, const char *filename, int lineno) {

    if (errstr == NULL)
        errcode = ERR_peek_last_error();
    else
        errcode = 0;
    fill_and_set_sslerror(PySSLErrorObject, errcode, errstr, lineno, errcode);
    ERR_clear_error();
    return NULL;
}

/*
 * SSL objects
 */

static PySSLSocket *
newPySSLSocket(PySSLContext *sslctx, PySocketSockObject *sock,
               enum py_ssl_server_or_client socket_type,
               char *server_hostname,
               PySSLMemoryBIO *inbio, PySSLMemoryBIO *outbio)
{
    PySSLSocket *self;
    SSL_CTX *ctx = sslctx->ctx;
    long mode;

    self = PyObject_New(PySSLSocket, &PySSLSocket_Type);
    if (self == NULL)
        return NULL;

    self->peer_cert = NULL;
    self->ssl = NULL;
    self->Socket = NULL;
    self->ctx = sslctx;
    self->shutdown_seen_zero = 0;
    self->handshake_done = 0;
    self->owner = NULL;
    self->server_hostname = NULL;
    if (server_hostname != NULL) {
        PyObject *hostname = PyUnicode_Decode(server_hostname, strlen(server_hostname),
                                              "idna", "strict");
        if (hostname == NULL) {
            Py_DECREF(self);
            return NULL;
        }
        self->server_hostname = hostname;
    }

    Py_INCREF(sslctx);

    /* Make sure the SSL error state is initialized */
    (void) ERR_get_state();
    ERR_clear_error();

    PySSL_BEGIN_ALLOW_THREADS
    self->ssl = SSL_new(ctx);
    PySSL_END_ALLOW_THREADS
    SSL_set_app_data(self->ssl, self);
    if (sock) {
        SSL_set_fd(self->ssl, Py_SAFE_DOWNCAST(sock->sock_fd, SOCKET_T, int));
    } else {
        /* BIOs are reference counted and SSL_set_bio borrows our reference.
         * To prevent a double free in memory_bio_dealloc() we need to take an
         * extra reference here. */
        BIO_up_ref(inbio->bio);
        BIO_up_ref(outbio->bio);
        SSL_set_bio(self->ssl, inbio->bio, outbio->bio);
    }
    mode = SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER;
#ifdef SSL_MODE_AUTO_RETRY
    mode |= SSL_MODE_AUTO_RETRY;
#endif
    SSL_set_mode(self->ssl, mode);

#if HAVE_SNI
    if (server_hostname != NULL)
        SSL_set_tlsext_host_name(self->ssl, server_hostname);
#endif

    /* If the socket is in non-blocking mode or timeout mode, set the BIO
     * to non-blocking mode (blocking is the default)
     */
    if (sock && sock->sock_timeout >= 0) {
        BIO_set_nbio(SSL_get_rbio(self->ssl), 1);
        BIO_set_nbio(SSL_get_wbio(self->ssl), 1);
    }

    PySSL_BEGIN_ALLOW_THREADS
    if (socket_type == PY_SSL_CLIENT)
        SSL_set_connect_state(self->ssl);
    else
        SSL_set_accept_state(self->ssl);
    PySSL_END_ALLOW_THREADS

    self->socket_type = socket_type;
    if (sock != NULL) {
        self->Socket = PyWeakref_NewRef((PyObject *) sock, NULL);
        if (self->Socket == NULL) {
            Py_DECREF(self);
            return NULL;
        }
    }
    return self;
}

/* SSL object methods */

/*[clinic input]
_ssl._SSLSocket.do_handshake
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_do_handshake_impl(PySSLSocket *self)
/*[clinic end generated code: output=6c0898a8936548f6 input=d2d737de3df018c8]*/
{
    int ret;
    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) {
            _setSSLError("Underlying socket connection gone",
                         PY_SSL_ERROR_NO_SOCKET, __FILE__, __LINE__);
            return NULL;
        }
        Py_INCREF(sock);

        /* just in case the blocking state of the socket has been changed */
        nonblocking = (sock->sock_timeout >= 0);
        BIO_set_nbio(SSL_get_rbio(self->ssl), nonblocking);
        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 {
        PySSL_BEGIN_ALLOW_THREADS
        ret = SSL_do_handshake(self->ssl);
        err = SSL_get_error(self->ssl, ret);
        PySSL_END_ALLOW_THREADS

        if (PyErr_CheckSignals())
            goto error;

        if (has_timeout)
            timeout = deadline - _PyTime_GetMonotonicClock();

        if (err == SSL_ERROR_WANT_READ) {
            sockstate = PySSL_select(sock, 0, timeout);
        } else if (err == SSL_ERROR_WANT_WRITE) {
            sockstate = PySSL_select(sock, 1, timeout);
        } else {
            sockstate = SOCKET_OPERATION_OK;
        }

        if (sockstate == SOCKET_HAS_TIMED_OUT) {
            PyErr_SetString(PySocketModule.timeout_error,
                            ERRSTR("The handshake operation timed out"));
            goto error;
        } else if (sockstate == SOCKET_HAS_BEEN_CLOSED) {
            PyErr_SetString(PySSLErrorObject,
                            ERRSTR("Underlying socket has been closed."));
            goto error;
        } else if (sockstate == SOCKET_TOO_LARGE_FOR_SELECT) {
            PyErr_SetString(PySSLErrorObject,
                            ERRSTR("Underlying socket too large for select()."));
            goto error;
        } else if (sockstate == SOCKET_IS_NONBLOCKING) {
            break;
        }
    } while (err == SSL_ERROR_WANT_READ || err == SSL_ERROR_WANT_WRITE);
    Py_XDECREF(sock);
    if (ret < 1)
        return PySSL_SetError(self, ret, __FILE__, __LINE__);

    if (self->peer_cert)
        X509_free (self->peer_cert);
    PySSL_BEGIN_ALLOW_THREADS
    self->peer_cert = SSL_get_peer_certificate(self->ssl);
    PySSL_END_ALLOW_THREADS
    self->handshake_done = 1;

    Py_RETURN_NONE;

error:
    Py_XDECREF(sock);
    return NULL;
}

static PyObject *
_create_tuple_for_attribute (ASN1_OBJECT *name, ASN1_STRING *value) {

    char namebuf[X509_NAME_MAXLEN];
    int buflen;
    PyObject *name_obj;
    PyObject *value_obj;
    PyObject *attr;
    unsigned char *valuebuf = NULL;

    buflen = OBJ_obj2txt(namebuf, sizeof(namebuf), name, 0);
    if (buflen < 0) {
        _setSSLError(NULL, 0, __FILE__, __LINE__);
        goto fail;
    }
    name_obj = PyUnicode_FromStringAndSize(namebuf, buflen);
    if (name_obj == NULL)
        goto fail;

    buflen = ASN1_STRING_to_UTF8(&valuebuf, value);
    if (buflen < 0) {
        _setSSLError(NULL, 0, __FILE__, __LINE__);
        Py_DECREF(name_obj);
        goto fail;
    }
    value_obj = PyUnicode_DecodeUTF8((char *) valuebuf,
                                     buflen, "strict");
    OPENSSL_free(valuebuf);
    if (value_obj == NULL) {
        Py_DECREF(name_obj);
        goto fail;
    }
    attr = PyTuple_New(2);
    if (attr == NULL) {
        Py_DECREF(name_obj);
        Py_DECREF(value_obj);
        goto fail;
    }
    PyTuple_SET_ITEM(attr, 0, name_obj);
    PyTuple_SET_ITEM(attr, 1, value_obj);
    return attr;

  fail:
    return NULL;
}

static PyObject *
_create_tuple_for_X509_NAME (X509_NAME *xname)
{
    PyObject *dn = NULL;    /* tuple which represents the "distinguished name" */
    PyObject *rdn = NULL;   /* tuple to hold a "relative distinguished name" */
    PyObject *rdnt;
    PyObject *attr = NULL;   /* tuple to hold an attribute */
    int entry_count = X509_NAME_entry_count(xname);
    X509_NAME_ENTRY *entry;
    ASN1_OBJECT *name;
    ASN1_STRING *value;
    int index_counter;
    int rdn_level = -1;
    int retcode;

    dn = PyList_New(0);
    if (dn == NULL)
        return NULL;
    /* now create another tuple to hold the top-level RDN */
    rdn = PyList_New(0);
    if (rdn == NULL)
        goto fail0;

    for (index_counter = 0;
         index_counter < entry_count;
         index_counter++)
    {
        entry = X509_NAME_get_entry(xname, index_counter);

        /* check to see if we've gotten to a new RDN */
        if (rdn_level >= 0) {
            if (rdn_level != X509_NAME_ENTRY_set(entry)) {
                /* yes, new RDN */
                /* add old RDN to DN */
                rdnt = PyList_AsTuple(rdn);
                Py_DECREF(rdn);
                if (rdnt == NULL)
                    goto fail0;
                retcode = PyList_Append(dn, rdnt);
                Py_DECREF(rdnt);
                if (retcode < 0)
                    goto fail0;
                /* create new RDN */
                rdn = PyList_New(0);
                if (rdn == NULL)
                    goto fail0;
            }
        }
        rdn_level = X509_NAME_ENTRY_set(entry);

        /* now add this attribute to the current RDN */
        name = X509_NAME_ENTRY_get_object(entry);
        value = X509_NAME_ENTRY_get_data(entry);
        attr = _create_tuple_for_attribute(name, value);
        /*
        fprintf(stderr, "RDN level %d, attribute %s: %s\n",
            entry->set,
            PyBytes_AS_STRING(PyTuple_GET_ITEM(attr, 0)),
            PyBytes_AS_STRING(PyTuple_GET_ITEM(attr, 1)));
        */
        if (attr == NULL)
            goto fail1;
        retcode = PyList_Append(rdn, attr);
        Py_DECREF(attr);
        if (retcode < 0)
            goto fail1;
    }
    /* now, there's typically a dangling RDN */
    if (rdn != NULL) {
        if (PyList_GET_SIZE(rdn) > 0) {
            rdnt = PyList_AsTuple(rdn);
            Py_DECREF(rdn);
            if (rdnt == NULL)
                goto fail0;
            retcode = PyList_Append(dn, rdnt);
            Py_DECREF(rdnt);
            if (retcode < 0)
                goto fail0;
        }
        else {
            Py_DECREF(rdn);
        }
    }

    /* convert list to tuple */
    rdnt = PyList_AsTuple(dn);
    Py_DECREF(dn);
    if (rdnt == NULL)
        return NULL;
    return rdnt;

  fail1:
    Py_XDECREF(rdn);

  fail0:
    Py_XDECREF(dn);
    return NULL;
}

static PyObject *
_get_peer_alt_names (X509 *certificate) {

    /* this code follows the procedure outlined in
       OpenSSL's crypto/x509v3/v3_prn.c:X509v3_EXT_print()
       function to extract the STACK_OF(GENERAL_NAME),
       then iterates through the stack to add the
       names. */

    int i, j;
    PyObject *peer_alt_names = Py_None;
    PyObject *v = NULL, *t;
    X509_EXTENSION *ext = NULL;
    GENERAL_NAMES *names = NULL;
    GENERAL_NAME *name;
    const X509V3_EXT_METHOD *method;
    BIO *biobuf = NULL;
    char buf[2048];
    char *vptr;
    int len;
    const unsigned char *p;

    if (certificate == NULL)
        return peer_alt_names;

    /* get a memory buffer */
    biobuf = BIO_new(BIO_s_mem());

    i = -1;
    while ((i = X509_get_ext_by_NID(
                    certificate, NID_subject_alt_name, i)) >= 0) {

        if (peer_alt_names == Py_None) {
            peer_alt_names = PyList_New(0);
            if (peer_alt_names == NULL)
                goto fail;
        }

        /* now decode the altName */
        ext = X509_get_ext(certificate, i);
        if(!(method = X509V3_EXT_get(ext))) {
            PyErr_SetString
              (PySSLErrorObject,
               ERRSTR("No method for internalizing subjectAltName!"));
            goto fail;
        }

        p = X509_EXTENSION_get_data(ext)->data;
        if (method->it)
            names = (GENERAL_NAMES*)
              (ASN1_item_d2i(NULL,
                             &p,
                             X509_EXTENSION_get_data(ext)->length,
                             ASN1_ITEM_ptr(method->it)));
        else
            names = (GENERAL_NAMES*)
              (method->d2i(NULL,
                           &p,
                           X509_EXTENSION_get_data(ext)->length));

        for(j = 0; j < sk_GENERAL_NAME_num(names); j++) {
            /* get a rendering of each name in the set of names */
            int gntype;
            ASN1_STRING *as = NULL;

            name = sk_GENERAL_NAME_value(names, j);
            gntype = name->type;
            switch (gntype) {
            case GEN_DIRNAME:
                /* we special-case DirName as a tuple of
                   tuples of attributes */

                t = PyTuple_New(2);
                if (t == NULL) {
                    goto fail;
                }

                v = PyUnicode_FromString("DirName");
                if (v == NULL) {
                    Py_DECREF(t);
                    goto fail;
                }
                PyTuple_SET_ITEM(t, 0, v);

                v = _create_tuple_for_X509_NAME (name->d.dirn);
                if (v == NULL) {
                    Py_DECREF(t);
                    goto fail;
                }
                PyTuple_SET_ITEM(t, 1, v);
                break;