Dual core processing

I'm reading one of the best books EVER right now (and I do mean EVER), called 'Pragmatic thinking and learning' by Andy Hunt. The reason I like it so much is because it links my interest in IT and in psychology/biology (I did one year of Psychology at the KUL but failed).

Andy talks about the brain as a dual core processor, where CPU1 is the L-mode (lineair or also called left mode, but this is less correct) of the brain and CPU2 is the R-mode (rich mode or right mode). There also is a contention at the message bus level that allows communication between the two, which implies that only 1 mode can dominate your brain at a certain moment in time. In this context he explains why in eXtreme Programming 'pairing' is so important. If you 'drive' you brain uses the L-mode to deal with the words, correct syntax. High level patterns and relations are made by the R-mode however. This is why sometimes your navigator says 'and if you refactor this bit here out, we can re-use it in that other place'. He also explains that this is the reason that when you're not pairing and you face a difficult problem it's important to step away from your desk, giving your R-mode a chance to kick in. I used to experience this in the past when I still smoked. Often the solution to a problem came during my sigarette break!

Fa-sci-na-ting stuff. To be continued no doubt...I'm off buying an Andy poster.

XML escaping

Did you ever want to define a constant in your code containing an XML string? For instance in a unit test to test if you can transform a piece of XML via XSLT into some desired format? You can do this the hard or the easy way: Either you take the chunk of XML, copy it in your IDE or some text editor and replace all double quotes with \" to escape them. Then you can start adding carriage returns in the String to have a somewhat readable piece of text. In case your XML contains all streets in Belgium, you will feel very, very useful doing this.

Or, you can have your IDE doing the work for you. In eclipse simply go to 'Window>Preference>Java>Editor>Typing' and check the “Escape text when pasting into a string literal“ option. As you can see it also adds the newlines and carriage returns:




I remember thinking 'Damn, I wish I knew about this before' when I first discovered this option. That might just be the criterium for any useful IDE feature I guess.

No worries, we got SSL

Last Tuesday evening a colleague and me attended an OWASP meeting of the Belgium chapter. The topics were:
-The Thinking Person's Guide to the Cloud. HOWTO: Keep your head in the clouds and your feet on the ground (by Gunnar Peterson, Arctec Group).
-Threat modeling (by John Steven, Cigital).

Especially the presentation of Gunnar Peterson was magnificent. He was funny, to the point and also explained the basic stuff, so you didn't have to be an expert to understand everything. He especially explained that a general mistake often made by non-security people, is to think that SSL secures your entire application. SSL is great, but there is a lot more to think about than just this one aspect.

There are a lot of methodologies to make your security vulnerabilities visible. This is called 'Threat modeling'. A simple and common used methodology is 'STRIDE', which stands for Spoofing, Tampering, Repudiation,Information Disclosure, Denial of Service and Elevation of privilege. These are the things you want to counter. The following table gives possible security solutions targeted at each specific problem.

Spoofing - Authentication
Tampering - Digital Signature
Repudiation - Audit Logging
Information Disclosure - Encryption
Denial of Service - Availability
Elevation of privilege - Authorization,Input validation

For each of the 6 items we have 3 categories where we could implement a security solution. You can implement it on the data level, method level and channel level. An example of the different levels:

• Data: XML
• Method: SOAP, URI
• Channel: HTTP

This means that you have 18 possibilities for implementing security. SSL however only is a solution for information disclosure, because you encryt the data on the channel level. Mostly that's not enough and you should for example encrypt parts of the xml message too.
SSL alone is not enough to secure your application!

No need to check that now, check it later...

Let's say you have an Oracle DB containing a table A with a foreign key to a table B and we want to add a foreign key constraint to ensure referential integrity. This might look something like this:

ADD CONSTRAINT "A_FK_B_CONSTRAINT_NAME" FOREIGN KEY ("COL_IN_A_REFFING_B") REFERENCES "TABLE_B" ("PK_ID")

Now if your A object has a oneToMany collection of B objects and you cascade delete these B objects whenever you remove A, you might run into a problem in the way the constraint is defined now. Hibernate deletes the A and B rows in 2 steps or statements, within the same transaction. If Hibernate first updates the PK_ID to NULL, COL_IN_A_REFFING_B will reference a non-existing row, which will cause an exception from the FK constraint checker.

This is why you need to add 'DEFERRABLE INITIALLY DEFERRED' to the constraint:

ADD CONSTRAINT "A_FK_B_CONSTRAINT_NAME" FOREIGN KEY ("COL_IN_A_REFFING_B") REFERENCES "TABLE_B" ("PK_ID") DEFERRABLE INITIALLY DEFERRED

This allows the constraint checking to be deferred or postponed till commit time. A constraint that is not deferrable (or DEFERRABLE INITIALLY IMMEDIATE) will be checked immediately after the execution of every statement. Currently only FK constraints accept this clause, other constraints are not deferrable. A good 'chicken or egg' post can be found here.

Show me your license!

In the follow up of open-sourcing our project, I spent some time today figuring out which license would be used best. This was completely new to me so I started comparing the different kind of licenses available. Apparently there are two major kind of licenses. On the one hand you have the 'GPL based' licenses, which enfore the code that use the open-source GPL code, to also be free and to also continue under the GPL 'flag'. They even have a clause stating that you cannot add additional restrictions on the 'redistribution of either the original work or a derivative work'. The goal is to not only garantuee the 'freedom' of the open-source software, but to also encourage software that uses open-source software to do the same.

On the other hand you have a bunch of 'proprietary compatible' licenses, like the MIT/X, the BSD and the Apache license which pretty much allow everything (use, modify, redistribute, ...) without enforcing extra constraints. Chances are high that we will go with an Apache license. Somewhere in between those major kinds, there also is a more pragmatic version of the GPL, called the 'Lesser GPL' which literally is a copy of the GPL exempting the fact that the propietary software should also use GPL.

I also read a lot about copyright, copyleft, dual licensing, trademark protection, and credit enforcement, but I'm not gonna bore you with that...

eID

At work a colleague and me just finished the 1.0 version of a new eID security module. It's based on the open source framework of Fedict that uses an Applet to allow you to sign in using your digital id. This framework was brought to life due to a lot of problems (stability, configuration, ...) with the current eID Fedict middleware solution.

For now it's still implemented as a stand-alone war, but it will be integrated in our larger, existing security module very soon. This larger module copes with authentication, authorization and identity management and is really mature for some time now. It came to life several years ago to replace a product from Sun called Access Manager. Onces the integration with eID is finished, the entire module will be open sourced. Exiting stuff!

PKCS#12

PKCS#12 is a PKCS (Public Key Cryptography Standards) developed by IBM and published by RSA Security. It is designed as the Personal Information Exchange Syntax Standard. This means that it serves as a standard to exchange sensitive key information between one kind of keystore and another kind. In Java you can instantiate a Keystore in the standard way Keystore.getInstance("JKS") or with a PKCS12 SPI implementation Keystore.getInstance("PKCS12"). Both implementations store private keys and certificates in a single file. OpenSSL however, stores them in separate files. Via the 'openssl pkcs12' command you can merge them into a PKCS#12 file, bridging the cap towards a Keystore. For instance:

openssl pkcs12 -export -inkey newSignedRequest.pem -certfile myCertFile.pem -name "TEST CERTIFICATE" -out myPkcs12Cert.p12

Certificates comming from a CA are almost always delivered in pkcs12 format.