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.

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

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:

  1. Replace e with 3, rule will be se3
  2. Replace l with 1 and l with !, rules will be sl1 and sl!
  3. 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 rulebased 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.

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:

correct horse battery staple

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):

Output device NULL SPAD

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:

Selection of printer NULL

Result in SM37:

Run with NULL or LP01

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 tcode code_scanner:

Search start screen

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:

Result search 1

A hard coded SID.

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

Result search 2

A hard coded plant.

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

Result search 3

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