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Taming the "Wild West" That Is TCP/IP

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Are you sure you're properly securing your IP applications?

 

If your IBM i is running TCP/IP, you have a problem. While the availability of IP applications is a blessing in that it gives your company an easy way to access your systems based on a set of defined standards, it also gives hackers an easy way to get into your systems and data using defined standards. Utilizing secure IP connectivity for your Telnet, FTP, and HTTP connectivity can help to curb the problem, but what about all of those other IP applications?

 

Often, the worst part of the issue can be getting a handle on exactly what applications you have running over TCP/IP. While you can display currently active IP connections using the NETSTAT command, that command gives only a snapshot of what's currently happening. The ideal would be a way to capture that activity on a timed basis to monitor TCP/IP traffic. By stringing together a few IBM APIs, we can do exactly that. In this article, we'll explore a utility to monitor IP traffic as well as learn exactly how to control traffic on restricted ports.

Monitoring TCP/IP Traffic

The command to dump IP network status data is DMPIPSTS. The source for this command can be found here. The parameters for this command are shown below:

  

Dump IP Net Stat Data (DMPIPSTS) Parameters

Keyword

Description

Choices

Notes

OUTFMT

Output format

*OUTFILE, *STMF, *PRINT

Optional

OUTFILE

Output File

Qualified object name

Optional

 

Qualifier 1: Output File

Name

 

 

Qualifier 2: Library

Name, *LIBL, *CURLIB

 

OUTMBR

Output member

Character value, *FIRST

Optional

ADDRPL

Add or Replace Records

*ADD, *REPLACE

Optional

STMF

Output Stream File

Character value

Optional

STMFTYPE

Stream File Type

*TXT, *CSV

 

 

The first parameter on this command identifies the destination for the data using one of the following three special values:

 

  • *OUTFILE—This value identifies that the output should be sent to the physical file identified on the OUTFILE parameter and the member identified on the OUTMBR parameter. The "Add or Replace Records" parameter is also used to identify whether or not to clear the destination file prior to adding new records.
  • *STMF—This value specifies that the output should be sent to the stream file identified on the Output Stream File parameter (STMF). The Stream File Type parameter (STMFTYPE) identifies the format of the output stream file as one of the following values: *CSV (the output is sent to a comma-delimited text format) or *TXT (the output is sent as a flat text file format).
  • *PRINT—This value defines that the output should be sent to a spooled file. When this option is used, multiple spooled files are created as a result of the number of columns of output.

Data Generated

The data generated by this command contains local and remote connection data along with associated job data for each IP network connection available at the time the command is executed. Below is a list of the columns generated by this command: 

 

File Layout for the Output of the DMPIPSTS Command

Field Name

Description

Data Type

Length

Dec Plc

IPCRMTADR

Remote System IP Address

CHAR

15

 

IPCRMTPORT

Remote System Port #

DECIMAL

10

0

IPCRMTNAME

Remote System Host Name

CHAR

256

 

IPCRMTSVNM

Remote Service Name

CHAR

32

 

IPCRMTSVDS

Remote Service Desc

CHAR

50

 

IPCLOCADR

Local System IP Address

CHAR

15

 

IPCLOCPORT

Local System Port #

DECIMAL

10

0

IPCLOCNAME

Local System Host Name

CHAR

256

 

IPCLOCSVNM

Local Service Name

CHAR

32

 

IPCLOCSVDS

Local Service Description

CHAR

50

 

IPCCNNSTT

Connection Status

CHAR

15

 

IPCCNOPNTP

Connection Open Type

CHAR

15

 

IPCNETCNTP

Connection Type

CHAR

10

 

IPCBYTIN

Bytes In

DECIMAL

20

0

IPCBYTOUT

Bytes Out

DECIMAL

20

0

IPCIDLTIME

Idle Time (hhhhhmmss)

DECIMAL

9

0

IPCJOBNAM

Connection Job Name

CHAR

10

 

IPCJOBUSR

Connection Job User

CHAR

10

 

IPCJOBNBR

Connection Job Number

CHAR

6

 

IPCCURRUSR

Current User Profile

CHAR

10

 

IPCRUNUSER

Run User

CHAR

10

 

IPCRUNTMS

Run Timestamp

TIMESTMP

10

 

 

The same output is generated whether you select *PRINT, *OUTFILE, or *STMF output. The main difference between the three options is that the *OUTFILE option allows you to indicate that you want to add the output to an existing physical file. This option gives you the ability to capture data over a period of time at given intervals. The command below shows how you would do this;

 

DMPIPSTS    OUTFMT(*OUTFILE) OUTFILE(MYLIB/IPSTATUS)

            OUTMBR(*FIRST) ADDRPL(*ADD)

 

This command will add current IP status data to the file IPSTATUS in library MYLIB.

 

When generating output to *STMF, you have the option of generating the output as a fixed-format text file or as a comma-delimited *CSV file. Figure 1 below shows a sample of the data as displayed in Microsoft Excel.

 

082712FaustDMPIPSTSFIG1

Figure 1: This is a sample of output generated to a comma delimited file.

 

To generate a file like the one shown above, the command below would be executed:

 

DMPIPSTS    OUTFMT(*STMF) STMF('/home/reports/ipstatus.csv')

            STMFTYPE(*CSV)

Knowledge Is Power

The key to securing your TCP/IP connectivity is knowing what IP traffic you're using. Because the output includes a timestamp indicating when the output was generated, you have the ability to also identify how long connectivity to a given port was connected and the IP address of the client that connected to that port. The output also identifies the user who started the job that is servicing the IP request locally. This can be a big help in ensuring that unnecessary (or even rogue) applications aren't leaving IP ports open on your system. Securing traffic for standard applications like Telnet, HTTP, or FTP is only half the battle. Identifying all of the "other" traffic is as important as, or maybe even more important than, implementing SSL on all of those standard applications. Now you have the utility to help you do that.

Mike Faust

Mike Faust is a senior consultant/analyst for Retail Technologies Corporation in Orlando, Florida. Mike is also the author of the books Active Server Pages Primer, The iSeries and AS/400 Programmer's Guide to Cool Things, JavaScript for the Business Developer, and SQL Built-in Functions and Stored Procedures. You can contact Mike at This email address is being protected from spambots. You need JavaScript enabled to view it..


MC Press books written by Mike Faust available now on the MC Press Bookstore.

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