Named Pipe Security and Access Rights
Windows security enables you to control access to named pipes. For more information about security, see Access-Control Model.
You can specify a security descriptor for a named pipe when you call the CreateNamedPipe function. The security descriptor controls access to both client and server ends of the named pipe. If you specify NULL, the named pipe gets a default security descriptor. The ACLs in the default security descriptor for a named pipe grant full control to the LocalSystem account, administrators, and the creator owner. They also grant read access to members of the Everyone group and the anonymous account.
To retrieve a named pipe's security descriptor, call the GetSecurityInfo function. To change the security descriptor of a named pipe, call the SetSecurityInfo function.
When a thread calls CreateNamedPipe to open a handle to the server end of an existing named pipe, the system performs an access check before returning the handle. The access check compares the thread's access token and the requested access rights against the DACL in the named pipe's security descriptor. In addition to the requested access rights, the DACL must allow the calling thread FILE_CREATE_PIPE_INSTANCE access to the named pipe.
Similarly, when a client calls the CreateFile or CallNamedPipe function to connect to the client end of a named pipe, the system performs an access check before granting access to the client.
The handle returned by the CreateNamedPipe function always has SYNCHRONIZE access. It also has GENERIC_READ, GENERIC_WRITE, or both, depending on the open mode of the pipe. The following are the access rights for each open mode.
| Open mode | Access rights |
|---|---|
| PIPE_ACCESS_DUPLEX (0x00000003) | FILE_GENERIC_READ, FILE_GENERIC_WRITE, and SYNCHRONIZE |
| PIPE_ACCESS_INBOUND (0x00000001) | FILE_GENERIC_READ and SYNCHRONIZE |
| PIPE_ACCESS_OUTBOUND (0x00000002) | FILE_GENERIC_WRITE and SYNCHRONIZE |
FILE_GENERIC_READ access for a named pipe combines the rights to read data from the pipe, read pipe attributes, read extended attributes, and read the pipe's DACL.
FILE_GENERIC_WRITE access for a named pipe combines the rights to write data to the pipe, append data to it, write pipe attributes, write extended attributes, and read the pipe's DACL. Because FILE_APPEND_DATA and FILE_CREATE_PIPE_INSTANCE have the same definition, so FILE_GENERIC_WRITE enables permission to create the pipe. To avoid this problem, use the individual rights instead of using FILE_GENERIC_WRITE.
You can request the ACCESS_SYSTEM_SECURITY access right to a named pipe object if you want to read or write the object's SACL. For more information, see Access-Control Lists (ACLs) and SACL Access Right.
To prevent remote users or users on a different terminal services session from accessing a named pipe, use the logon SID on the DACL for the pipe. The logon SID is used in run-as logons as well; it is the SID used to protect the per-session object namespace. For more information, see Getting the Logon SID in C++.