1 files changed, 56 insertions, 0 deletions

diff --git a/src/ext/Util/ca/utilca.cpp b/src/ext/Util/ca/utilca.cpp
index 37664a1c..d41f00c2 100644
--- a/src/ext/Util/ca/utilca.cpp
+++ b/src/ext/Util/ca/utilca.cpp
@@ -1,3 +1,59 @@
 // Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
 
 #include "precomp.h"
+
+HRESULT GetDomainFromServerName(
+    __deref_out_z LPWSTR* ppwzDomainName,
+    __in_z LPCWSTR wzServerName,
+    __in DWORD dwFlags
+    )
+{
+    HRESULT hr = S_OK;
+    DWORD er = ERROR_SUCCESS;
+    PDOMAIN_CONTROLLER_INFOW pDomainControllerInfo = NULL;
+    LPCWSTR wz = wzServerName ? wzServerName : L""; // initialize the domain to the provided server name (or empty string).
+
+    // If the server name was not empty, try to get the domain name out of it.
+    if (*wz)
+    {
+        er = ::DsGetDcNameW(NULL, wz, NULL, NULL, dwFlags, &pDomainControllerInfo);
+        if (RPC_S_SERVER_UNAVAILABLE == er)
+        {
+            // MSDN says, if we get the above error code, try again with the "DS_FORCE_REDISCOVERY" flag.
+            er = ::DsGetDcNameW(NULL, wz, NULL, NULL, dwFlags | DS_FORCE_REDISCOVERY, &pDomainControllerInfo);
+        }
+        ExitOnWin32Error(er, hr, "Could not get domain name from server name: %ls", wz);
+
+        if (pDomainControllerInfo->DomainControllerName)
+        {
+            // Skip the \\ prefix if present.
+            if ('\\' == *pDomainControllerInfo->DomainControllerName && '\\' == *(pDomainControllerInfo->DomainControllerName + 1))
+            {
+                wz = pDomainControllerInfo->DomainControllerName + 2;
+            }
+            else
+            {
+                wz = pDomainControllerInfo->DomainControllerName;
+            }
+        }
+    }
+
+LExit:
+    // Note: we overwrite the error code here as failure to contact domain controller above is not a fatal error.
+    if (wz && *wz)
+    {
+        hr = StrAllocString(ppwzDomainName, wz, 0);
+    }
+    else // return NULL the server name ended up empty.
+    {
+        ReleaseNullStr(*ppwzDomainName);
+        hr = S_OK;
+    }
+
+    if (pDomainControllerInfo)
+    {
+        ::NetApiBufferFree((LPVOID)pDomainControllerInfo);
+    }
+
+    return hr;
+}