/// <summary>
/// Attempts to connect to the specified process.
/// </summary>
private Stream TryConnectToProcess(int nodeProcessId, int timeout, Handshake handshake)
{
// Try and connect to the process.
string pipeName = NamedPipeUtil.GetPipeNameOrPath("MSBuild" + nodeProcessId);
NamedPipeClientStream nodeStream = new NamedPipeClientStream(".", pipeName, PipeDirection.InOut, PipeOptions.Asynchronous
#if FEATURE_PIPEOPTIONS_CURRENTUSERONLY
| PipeOptions.CurrentUserOnly
#endif
);
CommunicationsUtilities.Trace("Attempting connect to PID {0} with pipe {1} with timeout {2} ms", nodeProcessId, pipeName, timeout);
try
{
nodeStream.Connect(timeout);
#if !FEATURE_PIPEOPTIONS_CURRENTUSERONLY
if (NativeMethodsShared.IsWindows && !NativeMethodsShared.IsMono)
{
// Verify that the owner of the pipe is us. This prevents a security hole where a remote node has
// been faked up with ACLs that would let us attach to it. It could then issue fake build requests back to
// us, potentially causing us to execute builds that do harmful or unexpected things. The pipe owner can
// only be set to the user's own SID by a normal, unprivileged process. The conditions where a faked up
// remote node could set the owner to something else would also let it change owners on other objects, so
// this would be a security flaw upstream of us.
ValidateRemotePipeSecurityOnWindows(nodeStream);
}
#endif
int[] handshakeComponents = handshake.RetrieveHandshakeComponents();
for (int i = 0; i < handshakeComponents.Length; i++)
{
CommunicationsUtilities.Trace("Writing handshake part {0} ({1}) to pipe {2}", i, handshakeComponents[i], pipeName);
nodeStream.WriteIntForHandshake(handshakeComponents[i]);
}
// This indicates that we have finished all the parts of our handshake; hopefully the endpoint has as well.
nodeStream.WriteEndOfHandshakeSignal();
CommunicationsUtilities.Trace("Reading handshake from pipe {0}", pipeName);
#if NETCOREAPP2_1_OR_GREATER || MONO
nodeStream.ReadEndOfHandshakeSignal(true, timeout);
#else
nodeStream.ReadEndOfHandshakeSignal(true);
#endif
// We got a connection.
CommunicationsUtilities.Trace("Successfully connected to pipe {0}...!", pipeName);
return(nodeStream);
}
catch (Exception e) when(!ExceptionHandling.IsCriticalException(e))
{
// Can be:
// UnauthorizedAccessException -- Couldn't connect, might not be a node.
// IOException -- Couldn't connect, already in use.
// TimeoutException -- Couldn't connect, might not be a node.
// InvalidOperationException – Couldn’t connect, probably a different build
CommunicationsUtilities.Trace("Failed to connect to pipe {0}. {1}", pipeName, e.Message.TrimEnd());
// If we don't close any stream, we might hang up the child
nodeStream?.Dispose();
}
return(null);
}