UWP pipe client and C++ Fulltrustprocess pipe server - Access to the path is denied

Question

Hello UWP experts,

I get "Access to the path is denied" when connecting a UWP namedpipeclient to C++ Fulltrust process namedpipe server in packaged (WAPP) and non packaged mode. Its a simple piece of code to see how the namedpipe works betweek UWP and C++ fulltrustprocess.

The UWP app starts the fulltrustprocess with the FullTrustProcessLauncher and the fulltrustprocess is launched properly. In the fulltrustprocess we have the below C++ code to create the namedpipeserver and pipe is created successfully and it waits for the client to connect. That can be verified through the

pipelist64 tool.

HANDLE hPipe;
 std::wstring pipeName = L"\\\\.\\pipe\\TitleChangePipe";
 SECURITY_ATTRIBUTES sa;
 SECURITY_DESCRIPTOR sd;
 // Initialize a security descriptor that allows all access
 InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION);
 SetSecurityDescriptorDacl(&sd, TRUE, nullptr, FALSE);
 sa.nLength = sizeof(SECURITY_ATTRIBUTES);
 sa.lpSecurityDescriptor = &sd;
 sa.bInheritHandle = FALSE;
 hPipe = CreateNamedPipeW(
     pipeName.c_str(),                  // Pipe name
     PIPE_ACCESS_DUPLEX,                 // Read/Write access
     PIPE_TYPE_MESSAGE |                 // Message-type pipe
                  
     PIPE_WAIT,                          // Blocking mode
     1,           // Maximum instances
     1024,                                // Output buffer size
     1024,                                // Input buffer size
     200000,                                  // Default timeout
     &sa);                              // Default security attributes
 if (hPipe == INVALID_HANDLE_VALUE) {
    
     return false;
 }

Once the server starts it waits for client to connect

bool NamedPipeServer::WaitForClient() {

BOOL connected = ConnectNamedPipe(hPipe, NULL) ? TRUE : (GetLastError() == ERROR_PIPE_CONNECTED);

if (!connected) {

CloseHandle(hPipe_);

hPipe = INVALID_HANDLE_VALUE;

return false;

}

From the UWP client once the fulltrust process is launched , it tries to connect to the server , but pipeclient.connectAsync throws the exception "Access to the path is denied"

NamedPipeClientStream pipeClient;

pipeClient = new NamedPipeClientStream(".", "TitleChangePipe", PipeDirection.InOut);

await Task.Delay(2000);

await pipeClient.ConnectAsync(60000);

if (pipeClient.IsConnected)

{

}

Capabilities in package.manifest

<rescap:Capability Name="runFullTrust" />

<Capability Name="internetClient" />

Any idea why it throws the access denied in packaged and non packaged mode?

Answer 1

Hello @DotNET Fan ,

Welcome to Microsoft Q&A!

According to the official document,

Pipes are only supported within an app-container; ie, from one UWP process to another UWP process that's part of the same app.

Thank you.

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