Sweden-Number/dlls/winhttp/net.c

720 lines
22 KiB
C

/*
* Copyright 2008 Hans Leidekker for CodeWeavers
* Copyright 2013 Jacek Caban for CodeWeavers
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
*/
#include "config.h"
#define NONAMELESSUNION
#include "ws2tcpip.h"
#include <stdarg.h>
#include <stdio.h>
#include <assert.h>
#include "windef.h"
#include "winbase.h"
#include "winhttp.h"
#include "schannel.h"
#include "wine/debug.h"
#include "wine/library.h"
#include "winhttp_private.h"
WINE_DEFAULT_DEBUG_CHANNEL(winhttp);
static int sock_send(int fd, const void *msg, size_t len, int flags)
{
int ret;
do
{
if ((ret = send(fd, msg, len, flags)) == -1) WARN("send error %u\n", WSAGetLastError());
}
while(ret == -1 && WSAGetLastError() == WSAEINTR);
return ret;
}
static int sock_recv(int fd, void *msg, size_t len, int flags)
{
int ret;
do
{
if ((ret = recv(fd, msg, len, flags)) == -1) WARN("recv error %u\n", WSAGetLastError());
}
while(ret == -1 && WSAGetLastError() == WSAEINTR);
return ret;
}
static DWORD netconn_verify_cert( PCCERT_CONTEXT cert, WCHAR *server, DWORD security_flags, BOOL check_revocation )
{
HCERTSTORE store = cert->hCertStore;
BOOL ret;
CERT_CHAIN_PARA chainPara = { sizeof(chainPara), { 0 } };
PCCERT_CHAIN_CONTEXT chain;
char oid_server_auth[] = szOID_PKIX_KP_SERVER_AUTH;
char *server_auth[] = { oid_server_auth };
DWORD err = ERROR_SUCCESS;
TRACE("verifying %s\n", debugstr_w( server ));
chainPara.RequestedUsage.Usage.cUsageIdentifier = 1;
chainPara.RequestedUsage.Usage.rgpszUsageIdentifier = server_auth;
ret = CertGetCertificateChain( NULL, cert, NULL, store, &chainPara,
check_revocation ? CERT_CHAIN_REVOCATION_CHECK_CHAIN_EXCLUDE_ROOT : 0,
NULL, &chain );
if (ret)
{
if (chain->TrustStatus.dwErrorStatus)
{
static const DWORD supportedErrors =
CERT_TRUST_IS_NOT_TIME_VALID |
CERT_TRUST_IS_UNTRUSTED_ROOT |
CERT_TRUST_IS_NOT_VALID_FOR_USAGE;
if (chain->TrustStatus.dwErrorStatus & CERT_TRUST_IS_NOT_TIME_VALID)
{
if (!(security_flags & SECURITY_FLAG_IGNORE_CERT_DATE_INVALID))
err = ERROR_WINHTTP_SECURE_CERT_DATE_INVALID;
}
else if (chain->TrustStatus.dwErrorStatus &
CERT_TRUST_IS_UNTRUSTED_ROOT)
{
if (!(security_flags & SECURITY_FLAG_IGNORE_UNKNOWN_CA))
err = ERROR_WINHTTP_SECURE_INVALID_CA;
}
else if ((chain->TrustStatus.dwErrorStatus &
CERT_TRUST_IS_OFFLINE_REVOCATION) ||
(chain->TrustStatus.dwErrorStatus &
CERT_TRUST_REVOCATION_STATUS_UNKNOWN))
err = ERROR_WINHTTP_SECURE_CERT_REV_FAILED;
else if (chain->TrustStatus.dwErrorStatus & CERT_TRUST_IS_REVOKED)
err = ERROR_WINHTTP_SECURE_CERT_REVOKED;
else if (chain->TrustStatus.dwErrorStatus &
CERT_TRUST_IS_NOT_VALID_FOR_USAGE)
{
if (!(security_flags & SECURITY_FLAG_IGNORE_CERT_WRONG_USAGE))
err = ERROR_WINHTTP_SECURE_CERT_WRONG_USAGE;
}
else if (chain->TrustStatus.dwErrorStatus & ~supportedErrors)
err = ERROR_WINHTTP_SECURE_INVALID_CERT;
}
if (!err)
{
CERT_CHAIN_POLICY_PARA policyPara;
SSL_EXTRA_CERT_CHAIN_POLICY_PARA sslExtraPolicyPara;
CERT_CHAIN_POLICY_STATUS policyStatus;
CERT_CHAIN_CONTEXT chainCopy;
/* Clear chain->TrustStatus.dwErrorStatus so
* CertVerifyCertificateChainPolicy will verify additional checks
* rather than stopping with an existing, ignored error.
*/
memcpy(&chainCopy, chain, sizeof(chainCopy));
chainCopy.TrustStatus.dwErrorStatus = 0;
sslExtraPolicyPara.u.cbSize = sizeof(sslExtraPolicyPara);
sslExtraPolicyPara.dwAuthType = AUTHTYPE_SERVER;
sslExtraPolicyPara.pwszServerName = server;
sslExtraPolicyPara.fdwChecks = security_flags;
policyPara.cbSize = sizeof(policyPara);
policyPara.dwFlags = 0;
policyPara.pvExtraPolicyPara = &sslExtraPolicyPara;
ret = CertVerifyCertificateChainPolicy( CERT_CHAIN_POLICY_SSL,
&chainCopy, &policyPara,
&policyStatus );
/* Any error in the policy status indicates that the
* policy couldn't be verified.
*/
if (ret && policyStatus.dwError)
{
if (policyStatus.dwError == CERT_E_CN_NO_MATCH)
err = ERROR_WINHTTP_SECURE_CERT_CN_INVALID;
else
err = ERROR_WINHTTP_SECURE_INVALID_CERT;
}
}
CertFreeCertificateChain( chain );
}
else
err = ERROR_WINHTTP_SECURE_CHANNEL_ERROR;
TRACE("returning %08x\n", err);
return err;
}
static BOOL winsock_loaded;
void netconn_unload( void )
{
if (winsock_loaded) WSACleanup();
}
static BOOL WINAPI winsock_startup( INIT_ONCE *once, void *param, void **ctx )
{
int ret;
WSADATA data;
if (!(ret = WSAStartup( MAKEWORD(1,1), &data ))) winsock_loaded = TRUE;
else ERR( "WSAStartup failed: %d\n", ret );
return TRUE;
}
static void winsock_init(void)
{
static INIT_ONCE once = INIT_ONCE_STATIC_INIT;
InitOnceExecuteOnce( &once, winsock_startup, NULL, NULL );
}
static void set_blocking( netconn_t *conn, BOOL blocking )
{
ULONG state = !blocking;
ioctlsocket( conn->socket, FIONBIO, &state );
}
netconn_t *netconn_create( hostdata_t *host, const struct sockaddr_storage *sockaddr, int timeout )
{
netconn_t *conn;
unsigned int addr_len;
BOOL ret = FALSE;
winsock_init();
conn = heap_alloc_zero(sizeof(*conn));
if (!conn) return NULL;
conn->host = host;
conn->sockaddr = *sockaddr;
if ((conn->socket = socket( sockaddr->ss_family, SOCK_STREAM, 0 )) == -1)
{
WARN("unable to create socket (%u)\n", WSAGetLastError());
heap_free(conn);
return NULL;
}
switch (conn->sockaddr.ss_family)
{
case AF_INET:
addr_len = sizeof(struct sockaddr_in);
break;
case AF_INET6:
addr_len = sizeof(struct sockaddr_in6);
break;
default:
assert(0);
}
if (timeout > 0) set_blocking( conn, FALSE );
if (!connect( conn->socket, (const struct sockaddr *)&conn->sockaddr, addr_len )) ret = TRUE;
else
{
DWORD err = WSAGetLastError();
if (err == WSAEWOULDBLOCK || err == WSAEINPROGRESS)
{
FD_SET set;
TIMEVAL timeval = { 0, timeout * 1000 };
int res;
FD_ZERO( &set );
FD_SET( conn->socket, &set );
if ((res = select( conn->socket + 1, NULL, &set, NULL, &timeval )) > 0) ret = TRUE;
else if (!res) set_last_error( ERROR_WINHTTP_TIMEOUT );
}
}
if (timeout > 0) set_blocking( conn, TRUE );
if (!ret)
{
WARN("unable to connect to host (%u)\n", get_last_error());
closesocket( conn->socket );
heap_free( conn );
return NULL;
}
return conn;
}
void netconn_close( netconn_t *conn )
{
if (conn->secure)
{
heap_free( conn->peek_msg_mem );
heap_free(conn->ssl_buf);
heap_free(conn->extra_buf);
DeleteSecurityContext(&conn->ssl_ctx);
}
closesocket( conn->socket );
release_host( conn->host );
heap_free(conn);
}
BOOL netconn_secure_connect( netconn_t *conn, WCHAR *hostname, DWORD security_flags, CredHandle *cred_handle,
BOOL check_revocation)
{
SecBuffer out_buf = {0, SECBUFFER_TOKEN, NULL}, in_bufs[2] = {{0, SECBUFFER_TOKEN}, {0, SECBUFFER_EMPTY}};
SecBufferDesc out_desc = {SECBUFFER_VERSION, 1, &out_buf}, in_desc = {SECBUFFER_VERSION, 2, in_bufs};
BYTE *read_buf;
SIZE_T read_buf_size = 2048;
ULONG attrs = 0;
CtxtHandle ctx;
SSIZE_T size;
const CERT_CONTEXT *cert;
SECURITY_STATUS status;
DWORD res = ERROR_SUCCESS;
const DWORD isc_req_flags = ISC_REQ_ALLOCATE_MEMORY|ISC_REQ_USE_SESSION_KEY|ISC_REQ_CONFIDENTIALITY
|ISC_REQ_SEQUENCE_DETECT|ISC_REQ_REPLAY_DETECT|ISC_REQ_MANUAL_CRED_VALIDATION;
read_buf = heap_alloc(read_buf_size);
if(!read_buf)
return FALSE;
status = InitializeSecurityContextW(cred_handle, NULL, hostname, isc_req_flags, 0, 0, NULL, 0,
&ctx, &out_desc, &attrs, NULL);
assert(status != SEC_E_OK);
while(status == SEC_I_CONTINUE_NEEDED || status == SEC_E_INCOMPLETE_MESSAGE) {
if(out_buf.cbBuffer) {
assert(status == SEC_I_CONTINUE_NEEDED);
TRACE("sending %u bytes\n", out_buf.cbBuffer);
size = sock_send(conn->socket, out_buf.pvBuffer, out_buf.cbBuffer, 0);
if(size != out_buf.cbBuffer) {
ERR("send failed\n");
res = ERROR_WINHTTP_SECURE_CHANNEL_ERROR;
break;
}
FreeContextBuffer(out_buf.pvBuffer);
out_buf.pvBuffer = NULL;
out_buf.cbBuffer = 0;
}
if(status == SEC_I_CONTINUE_NEEDED) {
assert(in_bufs[1].cbBuffer < read_buf_size);
memmove(read_buf, (BYTE*)in_bufs[0].pvBuffer+in_bufs[0].cbBuffer-in_bufs[1].cbBuffer, in_bufs[1].cbBuffer);
in_bufs[0].cbBuffer = in_bufs[1].cbBuffer;
in_bufs[1].BufferType = SECBUFFER_EMPTY;
in_bufs[1].cbBuffer = 0;
in_bufs[1].pvBuffer = NULL;
}
assert(in_bufs[0].BufferType == SECBUFFER_TOKEN);
assert(in_bufs[1].BufferType == SECBUFFER_EMPTY);
if(in_bufs[0].cbBuffer + 1024 > read_buf_size) {
BYTE *new_read_buf;
new_read_buf = heap_realloc(read_buf, read_buf_size + 1024);
if(!new_read_buf) {
status = E_OUTOFMEMORY;
break;
}
in_bufs[0].pvBuffer = read_buf = new_read_buf;
read_buf_size += 1024;
}
size = sock_recv(conn->socket, read_buf+in_bufs[0].cbBuffer, read_buf_size-in_bufs[0].cbBuffer, 0);
if(size < 1) {
status = ERROR_WINHTTP_SECURE_CHANNEL_ERROR;
break;
}
TRACE("recv %lu bytes\n", size);
in_bufs[0].cbBuffer += size;
in_bufs[0].pvBuffer = read_buf;
status = InitializeSecurityContextW(cred_handle, &ctx, hostname, isc_req_flags, 0, 0, &in_desc,
0, NULL, &out_desc, &attrs, NULL);
TRACE("InitializeSecurityContext ret %08x\n", status);
if(status == SEC_E_OK) {
if(in_bufs[1].BufferType == SECBUFFER_EXTRA)
FIXME("SECBUFFER_EXTRA not supported\n");
status = QueryContextAttributesW(&ctx, SECPKG_ATTR_STREAM_SIZES, &conn->ssl_sizes);
if(status != SEC_E_OK) {
WARN("Could not get sizes\n");
break;
}
status = QueryContextAttributesW(&ctx, SECPKG_ATTR_REMOTE_CERT_CONTEXT, (void*)&cert);
if(status == SEC_E_OK) {
res = netconn_verify_cert(cert, hostname, security_flags, check_revocation);
CertFreeCertificateContext(cert);
if(res != ERROR_SUCCESS) {
WARN("cert verify failed: %u\n", res);
break;
}
}else {
WARN("Could not get cert\n");
break;
}
conn->ssl_buf = heap_alloc(conn->ssl_sizes.cbHeader + conn->ssl_sizes.cbMaximumMessage + conn->ssl_sizes.cbTrailer);
if(!conn->ssl_buf) {
res = GetLastError();
break;
}
}
}
heap_free(read_buf);
if(status != SEC_E_OK || res != ERROR_SUCCESS) {
WARN("Failed to initialize security context failed: %08x\n", status);
heap_free(conn->ssl_buf);
conn->ssl_buf = NULL;
DeleteSecurityContext(&ctx);
set_last_error(res ? res : ERROR_WINHTTP_SECURE_CHANNEL_ERROR);
return FALSE;
}
TRACE("established SSL connection\n");
conn->secure = TRUE;
conn->ssl_ctx = ctx;
return TRUE;
}
static BOOL send_ssl_chunk(netconn_t *conn, const void *msg, size_t size)
{
SecBuffer bufs[4] = {
{conn->ssl_sizes.cbHeader, SECBUFFER_STREAM_HEADER, conn->ssl_buf},
{size, SECBUFFER_DATA, conn->ssl_buf+conn->ssl_sizes.cbHeader},
{conn->ssl_sizes.cbTrailer, SECBUFFER_STREAM_TRAILER, conn->ssl_buf+conn->ssl_sizes.cbHeader+size},
{0, SECBUFFER_EMPTY, NULL}
};
SecBufferDesc buf_desc = {SECBUFFER_VERSION, ARRAY_SIZE(bufs), bufs};
SECURITY_STATUS res;
memcpy(bufs[1].pvBuffer, msg, size);
res = EncryptMessage(&conn->ssl_ctx, 0, &buf_desc, 0);
if(res != SEC_E_OK) {
WARN("EncryptMessage failed\n");
return FALSE;
}
if(sock_send(conn->socket, conn->ssl_buf, bufs[0].cbBuffer+bufs[1].cbBuffer+bufs[2].cbBuffer, 0) < 1) {
WARN("send failed\n");
return FALSE;
}
return TRUE;
}
BOOL netconn_send( netconn_t *conn, const void *msg, size_t len, int *sent )
{
if (conn->secure)
{
const BYTE *ptr = msg;
size_t chunk_size;
*sent = 0;
while(len) {
chunk_size = min(len, conn->ssl_sizes.cbMaximumMessage);
if(!send_ssl_chunk(conn, ptr, chunk_size))
return FALSE;
*sent += chunk_size;
ptr += chunk_size;
len -= chunk_size;
}
return TRUE;
}
return ((*sent = sock_send( conn->socket, msg, len, 0 )) != -1);
}
static BOOL read_ssl_chunk(netconn_t *conn, void *buf, SIZE_T buf_size, SIZE_T *ret_size, BOOL *eof)
{
const SIZE_T ssl_buf_size = conn->ssl_sizes.cbHeader+conn->ssl_sizes.cbMaximumMessage+conn->ssl_sizes.cbTrailer;
SecBuffer bufs[4];
SecBufferDesc buf_desc = {SECBUFFER_VERSION, ARRAY_SIZE(bufs), bufs};
SSIZE_T size, buf_len;
unsigned int i;
SECURITY_STATUS res;
assert(conn->extra_len < ssl_buf_size);
if(conn->extra_len) {
memcpy(conn->ssl_buf, conn->extra_buf, conn->extra_len);
buf_len = conn->extra_len;
conn->extra_len = 0;
heap_free(conn->extra_buf);
conn->extra_buf = NULL;
}else {
buf_len = sock_recv(conn->socket, conn->ssl_buf+conn->extra_len, ssl_buf_size-conn->extra_len, 0);
if(buf_len < 0)
return FALSE;
if(!buf_len) {
*eof = TRUE;
return TRUE;
}
}
*ret_size = 0;
*eof = FALSE;
do {
memset(bufs, 0, sizeof(bufs));
bufs[0].BufferType = SECBUFFER_DATA;
bufs[0].cbBuffer = buf_len;
bufs[0].pvBuffer = conn->ssl_buf;
res = DecryptMessage(&conn->ssl_ctx, &buf_desc, 0, NULL);
switch(res) {
case SEC_E_OK:
break;
case SEC_I_CONTEXT_EXPIRED:
TRACE("context expired\n");
*eof = TRUE;
return TRUE;
case SEC_E_INCOMPLETE_MESSAGE:
assert(buf_len < ssl_buf_size);
size = sock_recv(conn->socket, conn->ssl_buf+buf_len, ssl_buf_size-buf_len, 0);
if(size < 1)
return FALSE;
buf_len += size;
continue;
default:
WARN("failed: %08x\n", res);
return FALSE;
}
} while(res != SEC_E_OK);
for(i = 0; i < ARRAY_SIZE(bufs); i++) {
if(bufs[i].BufferType == SECBUFFER_DATA) {
size = min(buf_size, bufs[i].cbBuffer);
memcpy(buf, bufs[i].pvBuffer, size);
if(size < bufs[i].cbBuffer) {
assert(!conn->peek_len);
conn->peek_msg_mem = conn->peek_msg = heap_alloc(bufs[i].cbBuffer - size);
if(!conn->peek_msg)
return FALSE;
conn->peek_len = bufs[i].cbBuffer-size;
memcpy(conn->peek_msg, (char*)bufs[i].pvBuffer+size, conn->peek_len);
}
*ret_size = size;
}
}
for(i = 0; i < ARRAY_SIZE(bufs); i++) {
if(bufs[i].BufferType == SECBUFFER_EXTRA) {
conn->extra_buf = heap_alloc(bufs[i].cbBuffer);
if(!conn->extra_buf)
return FALSE;
conn->extra_len = bufs[i].cbBuffer;
memcpy(conn->extra_buf, bufs[i].pvBuffer, conn->extra_len);
}
}
return TRUE;
}
BOOL netconn_recv( netconn_t *conn, void *buf, size_t len, int flags, int *recvd )
{
*recvd = 0;
if (!len) return TRUE;
if (conn->secure)
{
SIZE_T size, cread;
BOOL res, eof;
if (conn->peek_msg)
{
*recvd = min( len, conn->peek_len );
memcpy( buf, conn->peek_msg, *recvd );
conn->peek_len -= *recvd;
conn->peek_msg += *recvd;
if (conn->peek_len == 0)
{
heap_free( conn->peek_msg_mem );
conn->peek_msg_mem = NULL;
conn->peek_msg = NULL;
}
/* check if we have enough data from the peek buffer */
if (!(flags & MSG_WAITALL) || *recvd == len) return TRUE;
}
size = *recvd;
do {
res = read_ssl_chunk(conn, (BYTE*)buf+size, len-size, &cread, &eof);
if(!res) {
WARN("read_ssl_chunk failed\n");
if(!size)
return FALSE;
break;
}
if(eof) {
TRACE("EOF\n");
break;
}
size += cread;
}while(!size || ((flags & MSG_WAITALL) && size < len));
TRACE("received %ld bytes\n", size);
*recvd = size;
return TRUE;
}
return ((*recvd = sock_recv( conn->socket, buf, len, flags )) != -1);
}
ULONG netconn_query_data_available( netconn_t *conn )
{
return conn->secure ? conn->peek_len : 0;
}
DWORD netconn_set_timeout( netconn_t *netconn, BOOL send, int value )
{
int opt = send ? SO_SNDTIMEO : SO_RCVTIMEO;
if (setsockopt( netconn->socket, SOL_SOCKET, opt, (void *)&value, sizeof(value) ) == -1)
{
DWORD err = WSAGetLastError();
WARN("setsockopt failed (%u)\n", err );
return err;
}
return ERROR_SUCCESS;
}
BOOL netconn_is_alive( netconn_t *netconn )
{
int len;
char b;
DWORD err;
set_blocking( netconn, FALSE );
len = sock_recv( netconn->socket, &b, 1, MSG_PEEK );
err = WSAGetLastError();
set_blocking( netconn, TRUE );
return len == 1 || (len == -1 && err == WSAEWOULDBLOCK);
}
static DWORD resolve_hostname( const WCHAR *name, INTERNET_PORT port, struct sockaddr_storage *sa )
{
ADDRINFOW *res, hints;
int ret;
memset( &hints, 0, sizeof(hints) );
/* Prefer IPv4 to IPv6 addresses, since some web servers do not listen on
* their IPv6 addresses even though they have IPv6 addresses in the DNS.
*/
hints.ai_family = AF_INET;
ret = GetAddrInfoW( name, NULL, &hints, &res );
if (ret != 0)
{
TRACE("failed to get IPv4 address of %s, retrying with IPv6\n", debugstr_w(name));
hints.ai_family = AF_INET6;
ret = GetAddrInfoW( name, NULL, &hints, &res );
if (ret != 0)
{
TRACE("failed to get address of %s\n", debugstr_w(name));
return ERROR_WINHTTP_NAME_NOT_RESOLVED;
}
}
memcpy( sa, res->ai_addr, res->ai_addrlen );
switch (res->ai_family)
{
case AF_INET:
((struct sockaddr_in *)sa)->sin_port = htons( port );
break;
case AF_INET6:
((struct sockaddr_in6 *)sa)->sin6_port = htons( port );
break;
}
FreeAddrInfoW( res );
return ERROR_SUCCESS;
}
struct resolve_args
{
const WCHAR *hostname;
INTERNET_PORT port;
struct sockaddr_storage *sa;
};
static DWORD CALLBACK resolve_proc( LPVOID arg )
{
struct resolve_args *ra = arg;
return resolve_hostname( ra->hostname, ra->port, ra->sa );
}
BOOL netconn_resolve( WCHAR *hostname, INTERNET_PORT port, struct sockaddr_storage *sa, int timeout )
{
DWORD ret;
if (timeout)
{
DWORD status;
HANDLE thread;
struct resolve_args ra;
ra.hostname = hostname;
ra.port = port;
ra.sa = sa;
thread = CreateThread( NULL, 0, resolve_proc, &ra, 0, NULL );
if (!thread) return FALSE;
status = WaitForSingleObject( thread, timeout );
if (status == WAIT_OBJECT_0) GetExitCodeThread( thread, &ret );
else ret = ERROR_WINHTTP_TIMEOUT;
CloseHandle( thread );
}
else ret = resolve_hostname( hostname, port, sa );
if (ret)
{
set_last_error( ret );
return FALSE;
}
return TRUE;
}
const void *netconn_get_certificate( netconn_t *conn )
{
const CERT_CONTEXT *ret;
SECURITY_STATUS res;
if (!conn->secure) return NULL;
res = QueryContextAttributesW(&conn->ssl_ctx, SECPKG_ATTR_REMOTE_CERT_CONTEXT, (void*)&ret);
return res == SEC_E_OK ? ret : NULL;
}
int netconn_get_cipher_strength( netconn_t *conn )
{
SecPkgContext_ConnectionInfo conn_info;
SECURITY_STATUS res;
if (!conn->secure) return 0;
res = QueryContextAttributesW(&conn->ssl_ctx, SECPKG_ATTR_CONNECTION_INFO, (void*)&conn_info);
if(res != SEC_E_OK)
WARN("QueryContextAttributesW failed: %08x\n", res);
return res == SEC_E_OK ? conn_info.dwCipherStrength : 0;
}