1 files changed, 805 insertions, 0 deletions

diff --git a/src/burn/engine/externalengine.cpp b/src/burn/engine/externalengine.cpp
new file mode 100644
index 00000000..409353e4
--- /dev/null
+++ b/src/burn/engine/externalengine.cpp
@@ -0,0 +1,805 @@
+// 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"
+
+
+static HRESULT CopyStringToExternal(
+    __in_z LPWSTR wzValue,
+    __in_z_opt LPWSTR wzBuffer,
+    __inout SIZE_T* pcchBuffer
+    );
+
+// function definitions
+
+void ExternalEngineGetPackageCount(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __out DWORD* pcPackages
+    )
+{
+    *pcPackages = pEngineState->packages.cPackages;
+}
+
+HRESULT ExternalEngineGetVariableNumeric(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in_z LPCWSTR wzVariable,
+    __out LONGLONG* pllValue
+    )
+{
+    HRESULT hr = S_OK;
+
+    if (wzVariable && *wzVariable)
+    {
+        hr = VariableGetNumeric(&pEngineState->variables, wzVariable, pllValue);
+    }
+    else
+    {
+        *pllValue = 0;
+        hr = E_INVALIDARG;
+    }
+
+    return hr;
+}
+
+HRESULT ExternalEngineGetVariableString(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in_z LPCWSTR wzVariable,
+    __out_ecount_opt(*pcchValue) LPWSTR wzValue,
+    __inout SIZE_T* pcchValue
+    )
+{
+    HRESULT hr = S_OK;
+    LPWSTR sczValue = NULL;
+
+    if (wzVariable && *wzVariable)
+    {
+        hr = VariableGetString(&pEngineState->variables, wzVariable, &sczValue);
+        if (SUCCEEDED(hr))
+        {
+            hr = CopyStringToExternal(sczValue, wzValue, pcchValue);
+        }
+    }
+    else
+    {
+        hr = E_INVALIDARG;
+    }
+
+    StrSecureZeroFreeString(sczValue);
+
+    return hr;
+}
+
+HRESULT ExternalEngineGetVariableVersion(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in_z LPCWSTR wzVariable,
+    __out_ecount_opt(*pcchValue) LPWSTR wzValue,
+    __inout SIZE_T* pcchValue
+    )
+{
+    HRESULT hr = S_OK;
+    VERUTIL_VERSION* pVersion = NULL;
+
+    if (wzVariable && *wzVariable)
+    {
+        hr = VariableGetVersion(&pEngineState->variables, wzVariable, &pVersion);
+        if (SUCCEEDED(hr))
+        {
+            hr = CopyStringToExternal(pVersion->sczVersion, wzValue, pcchValue);
+        }
+    }
+    else
+    {
+        hr = E_INVALIDARG;
+    }
+
+    ReleaseVerutilVersion(pVersion);
+
+    return hr;
+}
+
+HRESULT ExternalEngineFormatString(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in_z LPCWSTR wzIn,
+    __out_ecount_opt(*pcchOut) LPWSTR wzOut,
+    __inout SIZE_T* pcchOut
+    )
+{
+    HRESULT hr = S_OK;
+    LPWSTR sczValue = NULL;
+
+    if (wzIn && *wzIn)
+    {
+        hr = VariableFormatString(&pEngineState->variables, wzIn, &sczValue, NULL);
+        if (SUCCEEDED(hr))
+        {
+            hr = CopyStringToExternal(sczValue, wzOut, pcchOut);
+        }
+    }
+    else
+    {
+        hr = E_INVALIDARG;
+    }
+
+    StrSecureZeroFreeString(sczValue);
+
+    return hr;
+}
+
+HRESULT ExternalEngineEscapeString(
+    __in_z LPCWSTR wzIn,
+    __out_ecount_opt(*pcchOut) LPWSTR wzOut,
+    __inout SIZE_T* pcchOut
+    )
+{
+    HRESULT hr = S_OK;
+    LPWSTR sczValue = NULL;
+
+    if (wzIn && *wzIn)
+    {
+        hr = VariableEscapeString(wzIn, &sczValue);
+        if (SUCCEEDED(hr))
+        {
+            hr = CopyStringToExternal(sczValue, wzOut, pcchOut);
+        }
+    }
+    else
+    {
+        hr = E_INVALIDARG;
+    }
+
+    StrSecureZeroFreeString(sczValue);
+
+    return hr;
+}
+
+HRESULT ExternalEngineEvaluateCondition(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in_z LPCWSTR wzCondition,
+    __out BOOL* pf
+    )
+{
+    HRESULT hr = S_OK;
+
+    if (wzCondition && *wzCondition)
+    {
+        hr = ConditionEvaluate(&pEngineState->variables, wzCondition, pf);
+    }
+    else
+    {
+        *pf = FALSE;
+        hr = E_INVALIDARG;
+    }
+
+    return hr;
+}
+
+HRESULT ExternalEngineLog(
+    __in REPORT_LEVEL rl,
+    __in_z LPCWSTR wzMessage
+    )
+{
+    HRESULT hr = S_OK;
+
+    hr = LogStringLine(rl, "%ls", wzMessage);
+
+    return hr;
+}
+
+HRESULT ExternalEngineSendEmbeddedError(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in const DWORD dwErrorCode,
+    __in_z LPCWSTR wzMessage,
+    __in const DWORD dwUIHint,
+    __out int* pnResult
+    )
+{
+    HRESULT hr = S_OK;
+    BYTE* pbData = NULL;
+    SIZE_T cbData = 0;
+    DWORD dwResult = *pnResult = 0;
+
+    if (BURN_MODE_EMBEDDED != pEngineState->mode)
+    {
+        hr = HRESULT_FROM_WIN32(ERROR_INVALID_STATE);
+        ExitOnRootFailure(hr, "BA requested to send embedded message when not in embedded mode.");
+    }
+
+    hr = BuffWriteNumber(&pbData, &cbData, dwErrorCode);
+    ExitOnFailure(hr, "Failed to write error code to message buffer.");
+
+    hr = BuffWriteString(&pbData, &cbData, wzMessage ? wzMessage : L"");
+    ExitOnFailure(hr, "Failed to write message string to message buffer.");
+
+    hr = BuffWriteNumber(&pbData, &cbData, dwUIHint);
+    ExitOnFailure(hr, "Failed to write UI hint to message buffer.");
+
+    hr = PipeSendMessage(pEngineState->embeddedConnection.hPipe, BURN_EMBEDDED_MESSAGE_TYPE_ERROR, pbData, cbData, NULL, NULL, &dwResult);
+    ExitOnFailure(hr, "Failed to send embedded message over pipe.");
+
+    *pnResult = static_cast<int>(dwResult);
+
+LExit:
+    ReleaseBuffer(pbData);
+
+    return hr;
+}
+
+HRESULT ExternalEngineSendEmbeddedProgress(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in const DWORD dwProgressPercentage,
+    __in const DWORD dwOverallProgressPercentage,
+    __out int* pnResult
+    )
+{
+    HRESULT hr = S_OK;
+    BYTE* pbData = NULL;
+    SIZE_T cbData = 0;
+    DWORD dwResult = *pnResult = 0;
+
+    if (BURN_MODE_EMBEDDED != pEngineState->mode)
+    {
+        hr = HRESULT_FROM_WIN32(ERROR_INVALID_STATE);
+        ExitOnRootFailure(hr, "BA requested to send embedded progress message when not in embedded mode.");
+    }
+
+    hr = BuffWriteNumber(&pbData, &cbData, dwProgressPercentage);
+    ExitOnFailure(hr, "Failed to write progress percentage to message buffer.");
+
+    hr = BuffWriteNumber(&pbData, &cbData, dwOverallProgressPercentage);
+    ExitOnFailure(hr, "Failed to write overall progress percentage to message buffer.");
+
+    hr = PipeSendMessage(pEngineState->embeddedConnection.hPipe, BURN_EMBEDDED_MESSAGE_TYPE_PROGRESS, pbData, cbData, NULL, NULL, &dwResult);
+    ExitOnFailure(hr, "Failed to send embedded progress message over pipe.");
+
+    *pnResult = static_cast<int>(dwResult);
+
+LExit:
+    ReleaseBuffer(pbData);
+
+    return hr;
+}
+
+HRESULT ExternalEngineSetUpdate(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in_z_opt LPCWSTR wzLocalSource,
+    __in_z_opt LPCWSTR wzDownloadSource,
+    __in const DWORD64 qwSize,
+    __in const BOOTSTRAPPER_UPDATE_HASH_TYPE hashType,
+    __in_opt const BYTE* rgbHash,
+    __in const DWORD cbHash
+    )
+{
+    HRESULT hr = S_OK;
+    LPWSTR sczFilePath = NULL;
+    LPWSTR sczCommandline = NULL;
+    UUID guid = { };
+    WCHAR wzGuid[39];
+    RPC_STATUS rs = RPC_S_OK;
+
+    ::EnterCriticalSection(&pEngineState->userExperience.csEngineActive);
+    hr = UserExperienceEnsureEngineInactive(&pEngineState->userExperience);
+    ExitOnFailure(hr, "Engine is active, cannot change engine state.");
+
+    if ((!wzLocalSource || !*wzLocalSource) && (!wzDownloadSource || !*wzDownloadSource))
+    {
+        UpdateUninitialize(&pEngineState->update);
+    }
+    else if (BOOTSTRAPPER_UPDATE_HASH_TYPE_NONE == hashType && (0 != cbHash || rgbHash))
+    {
+        hr = E_INVALIDARG;
+    }
+    else if (BOOTSTRAPPER_UPDATE_HASH_TYPE_SHA512 == hashType && (SHA512_HASH_LEN != cbHash || !rgbHash))
+    {
+        hr = E_INVALIDARG;
+    }
+    else
+    {
+        UpdateUninitialize(&pEngineState->update);
+
+        hr = CoreRecreateCommandLine(&sczCommandline, BOOTSTRAPPER_ACTION_INSTALL, pEngineState->command.display, pEngineState->command.restart, BOOTSTRAPPER_RELATION_NONE, FALSE, pEngineState->registration.sczActiveParent, pEngineState->registration.sczAncestors, NULL, pEngineState->command.wzCommandLine);
+        ExitOnFailure(hr, "Failed to recreate command-line for update bundle.");
+
+        // Bundles would fail to use the downloaded update bundle, as the running bundle would be one of the search paths.
+        // Here I am generating a random guid, but in the future it would be nice if the feed would provide the ID of the update.
+        rs = ::UuidCreate(&guid);
+        hr = HRESULT_FROM_RPC(rs);
+        ExitOnFailure(hr, "Failed to create bundle update guid.");
+
+        if (!::StringFromGUID2(guid, wzGuid, countof(wzGuid)))
+        {
+            hr = E_OUTOFMEMORY;
+            ExitOnRootFailure(hr, "Failed to convert bundle update guid into string.");
+        }
+
+        hr = StrAllocFormatted(&sczFilePath, L"%ls\\%ls", wzGuid, pEngineState->registration.sczExecutableName);
+        ExitOnFailure(hr, "Failed to build bundle update file path.");
+
+        if (!wzLocalSource || !*wzLocalSource)
+        {
+            wzLocalSource = sczFilePath;
+        }
+
+        hr = PseudoBundleInitialize(FILEMAKEVERSION(rmj, rmm, rup, rpr), &pEngineState->update.package, FALSE, pEngineState->registration.sczId, BOOTSTRAPPER_RELATION_UPDATE, BOOTSTRAPPER_PACKAGE_STATE_ABSENT, FALSE, sczFilePath, wzLocalSource, wzDownloadSource, qwSize, TRUE, sczCommandline, NULL, NULL, NULL, rgbHash, cbHash);
+        ExitOnFailure(hr, "Failed to set update bundle.");
+
+        pEngineState->update.fUpdateAvailable = TRUE;
+    }
+
+LExit:
+    ::LeaveCriticalSection(&pEngineState->userExperience.csEngineActive);
+
+    ReleaseStr(sczCommandline);
+    ReleaseStr(sczFilePath);
+
+    return hr;
+}
+
+HRESULT ExternalEngineSetLocalSource(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in_z_opt LPCWSTR wzPackageOrContainerId,
+    __in_z_opt LPCWSTR wzPayloadId,
+    __in_z LPCWSTR wzPath
+    )
+{
+    HRESULT hr = S_OK;
+    BURN_CONTAINER* pContainer = NULL;
+    BURN_PAYLOAD* pPayload = NULL;
+
+    ::EnterCriticalSection(&pEngineState->userExperience.csEngineActive);
+    hr = UserExperienceEnsureEngineInactive(&pEngineState->userExperience);
+    ExitOnFailure(hr, "Engine is active, cannot change engine state.");
+
+    if (!wzPath || !*wzPath)
+    {
+        hr = E_INVALIDARG;
+    }
+    else if (wzPayloadId && *wzPayloadId)
+    {
+        hr = PayloadFindById(&pEngineState->payloads, wzPayloadId, &pPayload);
+        ExitOnFailure(hr, "BA requested unknown payload with id: %ls", wzPayloadId);
+
+        hr = StrAllocString(&pPayload->sczSourcePath, wzPath, 0);
+        ExitOnFailure(hr, "Failed to set source path for payload.");
+    }
+    else if (wzPackageOrContainerId && *wzPackageOrContainerId)
+    {
+        hr = ContainerFindById(&pEngineState->containers, wzPackageOrContainerId, &pContainer);
+        ExitOnFailure(hr, "BA requested unknown container with id: %ls", wzPackageOrContainerId);
+
+        hr = StrAllocString(&pContainer->sczSourcePath, wzPath, 0);
+        ExitOnFailure(hr, "Failed to set source path for container.");
+    }
+    else
+    {
+        hr = E_INVALIDARG;
+    }
+
+LExit:
+    ::LeaveCriticalSection(&pEngineState->userExperience.csEngineActive);
+
+    return hr;
+}
+
+HRESULT ExternalEngineSetDownloadSource(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in_z_opt LPCWSTR wzPackageOrContainerId,
+    __in_z_opt LPCWSTR wzPayloadId,
+    __in_z_opt LPCWSTR wzUrl,
+    __in_z_opt LPCWSTR wzUser,
+    __in_z_opt LPCWSTR wzPassword
+    )
+{
+    HRESULT hr = S_OK;
+    BURN_CONTAINER* pContainer = NULL;
+    BURN_PAYLOAD* pPayload = NULL;
+    DOWNLOAD_SOURCE* pDownloadSource = NULL;
+
+    ::EnterCriticalSection(&pEngineState->userExperience.csEngineActive);
+    hr = UserExperienceEnsureEngineInactive(&pEngineState->userExperience);
+    ExitOnFailure(hr, "Engine is active, cannot change engine state.");
+
+    if (wzPayloadId && *wzPayloadId)
+    {
+        hr = PayloadFindById(&pEngineState->payloads, wzPayloadId, &pPayload);
+        ExitOnFailure(hr, "BA requested unknown payload with id: %ls", wzPayloadId);
+
+        pDownloadSource = &pPayload->downloadSource;
+    }
+    else if (wzPackageOrContainerId && *wzPackageOrContainerId)
+    {
+        hr = ContainerFindById(&pEngineState->containers, wzPackageOrContainerId, &pContainer);
+        ExitOnFailure(hr, "BA requested unknown container with id: %ls", wzPackageOrContainerId);
+
+        pDownloadSource = &pContainer->downloadSource;
+    }
+    else
+    {
+        hr = E_INVALIDARG;
+        ExitOnFailure(hr, "BA did not provide container or payload id.");
+    }
+
+    if (wzUrl && *wzUrl)
+    {
+        hr = StrAllocString(&pDownloadSource->sczUrl, wzUrl, 0);
+        ExitOnFailure(hr, "Failed to set download URL.");
+
+        if (wzUser && *wzUser)
+        {
+            hr = StrAllocString(&pDownloadSource->sczUser, wzUser, 0);
+            ExitOnFailure(hr, "Failed to set download user.");
+
+            if (wzPassword && *wzPassword)
+            {
+                hr = StrAllocString(&pDownloadSource->sczPassword, wzPassword, 0);
+                ExitOnFailure(hr, "Failed to set download password.");
+            }
+            else // no password.
+            {
+                ReleaseNullStr(pDownloadSource->sczPassword);
+            }
+        }
+        else // no user means no password either.
+        {
+            ReleaseNullStr(pDownloadSource->sczUser);
+            ReleaseNullStr(pDownloadSource->sczPassword);
+        }
+    }
+    else // no URL provided means clear out the whole download source.
+    {
+        ReleaseNullStr(pDownloadSource->sczUrl);
+        ReleaseNullStr(pDownloadSource->sczUser);
+        ReleaseNullStr(pDownloadSource->sczPassword);
+    }
+
+LExit:
+    ::LeaveCriticalSection(&pEngineState->userExperience.csEngineActive);
+
+    return hr;
+}
+
+HRESULT ExternalEngineSetVariableNumeric(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in_z LPCWSTR wzVariable,
+    __in const LONGLONG llValue
+    )
+{
+    HRESULT hr = S_OK;
+
+    if (wzVariable && *wzVariable)
+    {
+        hr = VariableSetNumeric(&pEngineState->variables, wzVariable, llValue, FALSE);
+        ExitOnFailure(hr, "Failed to set numeric variable.");
+    }
+    else
+    {
+        hr = E_INVALIDARG;
+        ExitOnFailure(hr, "SetVariableNumeric did not provide variable name.");
+    }
+
+LExit:
+    return hr;
+}
+
+HRESULT ExternalEngineSetVariableString(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in_z LPCWSTR wzVariable,
+    __in_z_opt LPCWSTR wzValue,
+    __in const BOOL fFormatted
+    )
+{
+    HRESULT hr = S_OK;
+
+    if (wzVariable && *wzVariable)
+    {
+        hr = VariableSetString(&pEngineState->variables, wzVariable, wzValue, FALSE, fFormatted);
+        ExitOnFailure(hr, "Failed to set string variable.");
+    }
+    else
+    {
+        hr = E_INVALIDARG;
+        ExitOnFailure(hr, "SetVariableString did not provide variable name.");
+    }
+
+LExit:
+    return hr;
+}
+
+HRESULT ExternalEngineSetVariableVersion(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in_z LPCWSTR wzVariable,
+    __in_z_opt LPCWSTR wzValue
+    )
+{
+    HRESULT hr = S_OK;
+    VERUTIL_VERSION* pVersion = NULL;
+
+    if (wzVariable && *wzVariable)
+    {
+        if (wzValue)
+        {
+            hr = VerParseVersion(wzValue, 0, FALSE, &pVersion);
+            ExitOnFailure(hr, "Failed to parse new version value.");
+        }
+
+        hr = VariableSetVersion(&pEngineState->variables, wzVariable, pVersion, FALSE);
+        ExitOnFailure(hr, "Failed to set version variable.");
+    }
+    else
+    {
+        hr = E_INVALIDARG;
+        ExitOnFailure(hr, "SetVariableVersion did not provide variable name.");
+    }
+
+LExit:
+    ReleaseVerutilVersion(pVersion);
+
+    return hr;
+}
+
+void ExternalEngineCloseSplashScreen(
+    __in BURN_ENGINE_STATE* pEngineState
+    )
+{
+    // If the splash screen is still around, close it.
+    if (::IsWindow(pEngineState->command.hwndSplashScreen))
+    {
+        ::PostMessageW(pEngineState->command.hwndSplashScreen, WM_CLOSE, 0, 0);
+    }
+}
+
+HRESULT ExternalEngineCompareVersions(
+    __in_z LPCWSTR wzVersion1,
+    __in_z LPCWSTR wzVersion2,
+    __out int* pnResult
+    )
+{
+    HRESULT hr = S_OK;
+
+    hr = VerCompareStringVersions(wzVersion1, wzVersion2, FALSE, pnResult);
+
+    return hr;
+}
+
+HRESULT ExternalEngineDetect(
+    __in const DWORD dwThreadId,
+    __in_opt const HWND hwndParent
+    )
+{
+    HRESULT hr = S_OK;
+
+    if (!::PostThreadMessageW(dwThreadId, WM_BURN_DETECT, 0, reinterpret_cast<LPARAM>(hwndParent)))
+    {
+        ExitWithLastError(hr, "Failed to post detect message.");
+    }
+
+LExit:
+    return hr;
+}
+
+HRESULT ExternalEnginePlan(
+    __in const DWORD dwThreadId,
+    __in const BOOTSTRAPPER_ACTION action
+    )
+{
+    HRESULT hr = S_OK;
+
+    if (BOOTSTRAPPER_ACTION_LAYOUT > action || BOOTSTRAPPER_ACTION_UPDATE_REPLACE_EMBEDDED < action)
+    {
+        ExitOnRootFailure(hr = E_INVALIDARG, "BA passed invalid action to Plan: %u.", action);
+    }
+
+    if (!::PostThreadMessageW(dwThreadId, WM_BURN_PLAN, 0, action))
+    {
+        ExitWithLastError(hr, "Failed to post plan message.");
+    }
+
+LExit:
+    return hr;
+}
+
+HRESULT ExternalEngineElevate(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in const DWORD dwThreadId,
+    __in_opt const HWND hwndParent
+    )
+{
+    HRESULT hr = S_OK;
+
+    if (INVALID_HANDLE_VALUE != pEngineState->companionConnection.hPipe)
+    {
+        hr = HRESULT_FROM_WIN32(ERROR_ALREADY_INITIALIZED);
+    }
+    else if (!::PostThreadMessageW(dwThreadId, WM_BURN_ELEVATE, 0, reinterpret_cast<LPARAM>(hwndParent)))
+    {
+        ExitWithLastError(hr, "Failed to post elevate message.");
+    }
+
+LExit:
+    return hr;
+}
+
+HRESULT ExternalEngineApply(
+    __in const DWORD dwThreadId,
+    __in_opt const HWND hwndParent
+    )
+{
+    HRESULT hr = S_OK;
+
+    ExitOnNull(hwndParent, hr, E_INVALIDARG, "BA passed NULL hwndParent to Apply.");
+    if (!::IsWindow(hwndParent))
+    {
+        ExitOnRootFailure(hr = E_INVALIDARG, "BA passed invalid hwndParent to Apply.");
+    }
+
+    if (!::PostThreadMessageW(dwThreadId, WM_BURN_APPLY, 0, reinterpret_cast<LPARAM>(hwndParent)))
+    {
+        ExitWithLastError(hr, "Failed to post apply message.");
+    }
+
+LExit:
+    return hr;
+}
+
+HRESULT ExternalEngineQuit(
+    __in const DWORD dwThreadId,
+    __in const DWORD dwExitCode
+    )
+{
+    HRESULT hr = S_OK;
+
+    if (!::PostThreadMessageW(dwThreadId, WM_BURN_QUIT, static_cast<WPARAM>(dwExitCode), 0))
+    {
+        ExitWithLastError(hr, "Failed to post shutdown message.");
+    }
+
+LExit:
+    return hr;
+}
+
+HRESULT ExternalEngineLaunchApprovedExe(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in const DWORD dwThreadId,
+    __in_opt const HWND hwndParent,
+    __in_z LPCWSTR wzApprovedExeForElevationId,
+    __in_z_opt LPCWSTR wzArguments,
+    __in const DWORD dwWaitForInputIdleTimeout
+    )
+{
+    HRESULT hr = S_OK;
+    BURN_APPROVED_EXE* pApprovedExe = NULL;
+    BOOL fLeaveCriticalSection = FALSE;
+    BURN_LAUNCH_APPROVED_EXE* pLaunchApprovedExe = NULL;
+
+    pLaunchApprovedExe = (BURN_LAUNCH_APPROVED_EXE*)MemAlloc(sizeof(BURN_LAUNCH_APPROVED_EXE), TRUE);
+    ExitOnNull(pLaunchApprovedExe, hr, E_OUTOFMEMORY, "Failed to alloc BURN_LAUNCH_APPROVED_EXE");
+
+    ::EnterCriticalSection(&pEngineState->userExperience.csEngineActive);
+    fLeaveCriticalSection = TRUE;
+    hr = UserExperienceEnsureEngineInactive(&pEngineState->userExperience);
+    ExitOnFailure(hr, "Engine is active, cannot change engine state.");
+
+    if (!wzApprovedExeForElevationId || !*wzApprovedExeForElevationId)
+    {
+        ExitFunction1(hr = E_INVALIDARG);
+    }
+
+    hr = ApprovedExesFindById(&pEngineState->approvedExes, wzApprovedExeForElevationId, &pApprovedExe);
+    ExitOnFailure(hr, "BA requested unknown approved exe with id: %ls", wzApprovedExeForElevationId);
+
+    hr = StrAllocString(&pLaunchApprovedExe->sczId, wzApprovedExeForElevationId, NULL);
+    ExitOnFailure(hr, "Failed to copy the id.");
+
+    if (wzArguments)
+    {
+        hr = StrAllocString(&pLaunchApprovedExe->sczArguments, wzArguments, NULL);
+        ExitOnFailure(hr, "Failed to copy the arguments.");
+    }
+
+    pLaunchApprovedExe->dwWaitForInputIdleTimeout = dwWaitForInputIdleTimeout;
+
+    pLaunchApprovedExe->hwndParent = hwndParent;
+
+    if (!::PostThreadMessageW(dwThreadId, WM_BURN_LAUNCH_APPROVED_EXE, 0, reinterpret_cast<LPARAM>(pLaunchApprovedExe)))
+    {
+        ExitWithLastError(hr, "Failed to post launch approved exe message.");
+    }
+
+LExit:
+    if (fLeaveCriticalSection)
+    {
+        ::LeaveCriticalSection(&pEngineState->userExperience.csEngineActive);
+    }
+
+    if (FAILED(hr))
+    {
+        ApprovedExesUninitializeLaunch(pLaunchApprovedExe);
+    }
+
+    return hr;
+}
+
+HRESULT ExternalEngineSetUpdateSource(
+    __in BURN_ENGINE_STATE* pEngineState,
+    __in_z LPCWSTR wzUrl
+    )
+{
+    HRESULT hr = S_OK;
+    BOOL fLeaveCriticalSection = FALSE;
+
+    ::EnterCriticalSection(&pEngineState->userExperience.csEngineActive);
+    fLeaveCriticalSection = TRUE;
+    hr = UserExperienceEnsureEngineInactive(&pEngineState->userExperience);
+    ExitOnFailure(hr, "Engine is active, cannot change engine state.");
+
+    if (wzUrl && *wzUrl)
+    {
+        hr = StrAllocString(&pEngineState->update.sczUpdateSource, wzUrl, 0);
+        ExitOnFailure(hr, "Failed to set feed download URL.");
+    }
+    else // no URL provided means clear out the whole download source.
+    {
+        ReleaseNullStr(pEngineState->update.sczUpdateSource);
+    }
+
+LExit:
+    if (fLeaveCriticalSection)
+    {
+        ::LeaveCriticalSection(&pEngineState->userExperience.csEngineActive);
+    }
+
+    return hr;
+}
+
+// TODO: callers need to provide the original size (at the time of first public release) of the struct instead of the current size.
+HRESULT WINAPI ExternalEngineValidateMessageParameter(
+    __in_opt const LPVOID pv,
+    __in SIZE_T cbSizeOffset,
+    __in DWORD dwMinimumSize
+    )
+{
+    HRESULT hr = S_OK;
+
+    if (!pv)
+    {
+        ExitFunction1(hr = E_INVALIDARG);
+    }
+
+    DWORD cbSize = *(DWORD*)((BYTE*)pv + cbSizeOffset);
+    if (dwMinimumSize < cbSize)
+    {
+        ExitFunction1(hr = E_INVALIDARG);
+    }
+
+LExit:
+    return hr;
+}
+
+static HRESULT CopyStringToExternal(
+    __in_z LPWSTR wzValue,
+    __in_z_opt LPWSTR wzBuffer,
+    __inout SIZE_T* pcchBuffer
+    )
+{
+    HRESULT hr = S_OK;
+    BOOL fTooSmall = !wzBuffer;
+
+    if (!fTooSmall)
+    {
+        hr = ::StringCchCopyExW(wzBuffer, *pcchBuffer, wzValue, NULL, NULL, STRSAFE_FILL_BEHIND_NULL);
+        if (STRSAFE_E_INSUFFICIENT_BUFFER == hr)
+        {
+            fTooSmall = TRUE;
+        }
+    }
+
+    if (fTooSmall)
+    {
+        hr = ::StringCchLengthW(wzValue, STRSAFE_MAX_LENGTH, reinterpret_cast<size_t*>(pcchBuffer));
+        if (SUCCEEDED(hr))
+        {
+            hr = E_MOREDATA;
+            *pcchBuffer += 1; // null terminator.
+        }
+    }
+
+    return hr;
+}