Request validation exit point: client and server

The request validation exit points can be used to restrict operations which can be performed by FTP users.

Request validation exit points are provided by both the FTP client and server; to restrict both FTP client and FTP server access, exit programs must be added to both exit points.

Tip: Because both the FTP client and server exit points share the same exit point format, you can write a single program to handle both.

If you implement anonymous FTP, write your FTP server request validation exit program to restrict anonymous FTP users to retrieve subcommands only, and never allow anonymous users to run CL commands.

What your program should include

Exception handling
Debugging
Logging

Allowed and rejected commands

The FTP request validation exit program gives you control over whether to accept or reject an operation. Decisions made by exit programs are in addition to any validation that is performed by the FTP client or FTP server application. The FTP client or server application calls the exit program registered for that application each time it processes one of these requests:

Directory or library creation
Directory or library deletion
Setting current directory
Listing file names
File deletion
Sending a file
Receiving a file
Renaming a file
Running a CL command

You might want to set value -1 of parameter 8 (Allow operation) in the VRLQ0100 exit point format to always and unconditionally reject a command.

Is there an exit program timeout feature?

There is no time-out for FTP exit programs. If the exit program has an error or exception that it cannot handle, the FTP server will stop the session.

Example programs

Example programs are available to help you set up anonymous FTP on your system. These examples are for illustration purposes. They do not contain all the features to run on a production system. Use these examples as a starting point to build your own programs. By copying portions of the code from the examples, you can add them to programs that you write yourself. Run the example programs on a system other than your production system.

Example: FTP client or server request validation exit program in CL code
This is an example of a simple File Transfer Protocol (FTP) request validation exit program. It is written in control language (CL). This code is not complete, but provides a starting point to help you create your own program for the client or server exit point.
Example: FTP server request validation exit program in ILE RPG code
This example demonstrates a simple File Transfer Protocol (FTP) request validation exit program used between the client and the server. It is written in ILE RPG programming language. This code is not complete, but provides a starting point to help you create your own program.
VLRQ0100 exit point format
The exit point for FTP server application request validation is QIBM_QTMF_SERVER_REQ. The exit point for FTP client application request validation is QIBM_QTMF_CLIENT_REQ. The interface that controls the parameter format for these exit points is VLRQ0100. The VLRQ0100 exit point interface contains certain parameters.

Parent topic:

File Transfer Protocol exit programs

Related reference
Writing exit programs for anonymous File Transfer Protocol