ntlm_sspi: add support for channel binding

Windows extended potection (aka ssl channel binding) is required
to login to ntlm IIS endpoint, otherwise the server returns 401
responses.

Fixes #3280
Closes #3321

3 files changed, 51 insertions, 8 deletions

diff --git a/lib/urldata.h b/lib/urldata.h
index 72c75cbd9..b71a843b4 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -328,6 +328,12 @@ struct kerberos5data {
 struct ntlmdata {
   curlntlm state;
 #ifdef USE_WINDOWS_SSPI
+/* The sslContext is used for the Schannel bindings. The
+ * api is available on the Windows 7 SDK and later.
+ */
+#ifdef SECPKG_ATTR_ENDPOINT_BINDINGS
+  CtxtHandle *sslContext;
+#endif
   CredHandle *credentials;
   CtxtHandle *context;
   SEC_WINNT_AUTH_IDENTITY identity;
diff --git a/lib/vauth/ntlm_sspi.c b/lib/vauth/ntlm_sspi.c
index b66cfe737..67112820e 100644
--- a/lib/vauth/ntlm_sspi.c
+++ b/lib/vauth/ntlm_sspi.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -249,7 +249,7 @@ CURLcode Curl_auth_create_ntlm_type3_message(struct Curl_easy *data,
                                              char **outptr, size_t *outlen)
 {
   CURLcode result = CURLE_OK;
-  SecBuffer type_2_buf;
+  SecBuffer type_2_bufs[2];
   SecBuffer type_3_buf;
   SecBufferDesc type_2_desc;
   SecBufferDesc type_3_desc;
@@ -261,12 +261,39 @@ CURLcode Curl_auth_create_ntlm_type3_message(struct Curl_easy *data,
   (void) userp;
 
   /* Setup the type-2 "input" security buffer */
-  type_2_desc.ulVersion = SECBUFFER_VERSION;
-  type_2_desc.cBuffers  = 1;
-  type_2_desc.pBuffers  = &type_2_buf;
-  type_2_buf.BufferType = SECBUFFER_TOKEN;
-  type_2_buf.pvBuffer   = ntlm->input_token;
-  type_2_buf.cbBuffer   = curlx_uztoul(ntlm->input_token_len);
+  type_2_desc.ulVersion     = SECBUFFER_VERSION;
+  type_2_desc.cBuffers      = 1;
+  type_2_desc.pBuffers      = &type_2_bufs[0];
+  type_2_bufs[0].BufferType = SECBUFFER_TOKEN;
+  type_2_bufs[0].pvBuffer   = ntlm->input_token;
+  type_2_bufs[0].cbBuffer   = curlx_uztoul(ntlm->input_token_len);
+
+#ifdef SECPKG_ATTR_ENDPOINT_BINDINGS
+  /* ssl context comes from schannel.
+  * When extended protection is used in IIS server,
+  * we have to pass a second SecBuffer to the SecBufferDesc
+  * otherwise IIS will not pass the authentication (401 response).
+  * Minimum supported version is Windows 7.
+  * https://docs.microsoft.com/en-us/security-updates
+  * /SecurityAdvisories/2009/973811
+  */
+  if(ntlm->sslContext) {
+    SEC_CHANNEL_BINDINGS channelBindings;
+    SecPkgContext_Bindings pkgBindings;
+    pkgBindings.Bindings = &channelBindings;
+    status = s_pSecFn->QueryContextAttributes(
+      ntlm->sslContext,
+      SECPKG_ATTR_ENDPOINT_BINDINGS,
+      &pkgBindings
+    );
+    if(status == SEC_E_OK) {
+      type_2_desc.cBuffers++;
+      type_2_bufs[1].BufferType = SECBUFFER_CHANNEL_BINDINGS;
+      type_2_bufs[1].cbBuffer = pkgBindings.BindingsLength;
+      type_2_bufs[1].pvBuffer = pkgBindings.Bindings;
+    }
+  }
+#endif
 
   /* Setup the type-3 "output" security buffer */
   type_3_desc.ulVersion = SECBUFFER_VERSION;
diff --git a/lib/vtls/schannel.c b/lib/vtls/schannel.c
index ab7f83f46..af22ecbb6 100644
--- a/lib/vtls/schannel.c
+++ b/lib/vtls/schannel.c
@@ -1414,6 +1414,16 @@ schannel_connect_common(struct connectdata *conn, int sockindex,
     connssl->state = ssl_connection_complete;
     conn->recv[sockindex] = schannel_recv;
     conn->send[sockindex] = schannel_send;
+
+#ifdef SECPKG_ATTR_ENDPOINT_BINDINGS
+    /* When SSPI is used in combination with Schannel
+     * we need the Schannel context to create the Schannel
+     * binding to pass the IIS extended protection checks.
+     * Available on Windows 7 or later.
+     */
+    conn->ntlm.sslContext = &BACKEND->ctxt->ctxt_handle;
+#endif
+
     *done = TRUE;
   }
   else