Friday, May 10, 2013

OAuth Security implementation in OSB/SOA (REST/SOAP) service


I had recently reviewed / implemented custom made OAuth for OSB. The below article takes you through the journey of becoming secure by using Oauth and the different parameters used and steps to generate valid payload which will pass OAuth security.
Why Oauth ?
Good tutorial @ The OAuth 1.0 Guide
I have tried to map it with the different parameters I have used for creating the signature.
Excerpts from that article
OAuth uses digital signatures instead of sending the full credentials with each request. Digital signatures help the recipient to verify that the content of the request hasn’t changed in transit. To do that, the sender uses a mathematical algorithm to calculate the signature of the request and includes it with the request.
                  In turn, the recipient performs the same workflow to calculate the signature of the request and compares it to the signature value provided. If the two match, the recipient can be confident that the request has not been modified in transit. The confidence level depends on the properties of the signature algorithm used. This mechanism requires both sides to use the same signature algorithm and apply it in the same manner.
         A common way to sign digital content is using a hash algorithm. In general, hashing is the process of taking data (of any size) and condensing it to a much smaller value (digest) in a fully reproducible (one-way) manner. This means that using the same hash algorithm on the same data will always produce the same smaller value. Unlike compression which aims to preserve much of the original uncompressed data, hashing usually does not allow going from the smaller value back to the original.
Shared secret (geo-key-id)
By itself, hashing does not verify the identity of the sender, only data integrity. In order to allow the recipient to verify that the request came from the claimed sender, the hash algorithm is combined with a shared secret. If both sides agree on some shared secret known only to them, they can add it to the content being hashed
Timestamp & nonce (geo-expires-by​ & geo-nonce)
         As long as the shared secrets remains protected, anyone listening in on the network will not be able to forge new requests as that will require using the shared secret. They will however, be able to make the same sign request over and over again. If the intercepted request provides access to sensitive protected data, it can be a significant security risk.
To prevent compromised requests from being used again (replayed), OAuth uses a nonce and timestamp. The term nonce means ‘number used once’ and is a unique and usually random string that is meant to uniquely identify each signed request. Since the nonce value is included in the signature, it cannot be changed by an attacker without knowing the shared secret.
Signature(geo-signature - HMAC-SHAxxx)
OAuth defines multiple signature methods to sign and verify requests: We can use HMAC-SHA 1 ,256 ,512, HMAC signature algorithm combined with the SHA hash method. Since these methods are too complex, so it’s better not to write their own implementations, but instead use trusted open source solutions available for most languages.

UserId /Target sys/Source sys/Module/Service(geo-username​ , geo-target-system-name, geo-source-system-name)
The user Id / Target system/Source system is used to create the signature.
These are not mandatory values , but just added to give more information at the receiver side to do more processing with the payload. This information can be encapsulated under a shared key, but kept it separate so that we need to maintain less number of shared keys.

Based on requirement you can have more service level information to be passed from the Consumer, like different levels of maintaining the shared secret.It can be at a Department/Group level, then modules in each group/dept /then at each service level.

How to get started ?

Pre-Requisites to consume the services validated by Oauth.
1.       geo-key-id​ :- Contact the end system and decide upon on a shared key Id and a hashed shared key value
2.       This hashed shared key value will be part of all the requests and should be confidential between end system and consuming system.
3.       geo-username :-The consuming system should get end system user ids created and need to pass this value along with the request. This is mainly for user token generation at the Atomic service level. The user token will be only be generated in case the user has a valid account /permissions in end system.
4.       geo-target-system-name :- Some more additional information on the type of grouped services like Finance /HRMS/OTM etc application that the requester is trying to access.
5.       geo-source-system-name :- Callers domain name , some more additional information to track the requester.
6.       geo-signature:-The algorithm that needs to be used for hashing and creating signature is HMAC-SHAxxx. There are open source utilities available which can be downloaded to sign the payload using HMAC-SHAxxx algorithm. 
7.       geo-nonce:-Nonce value should be unique and needs to use a unique id generator to populate Nonce value.
8.       geo-expires-by :- The timestamp utility to compute the expiration time of the request.


How to consume the services validated by Oauth.

1.       Identify values for main parameters
·         geo-username
·         geo-target-system-name
·         geo-source-system-name
·         geo-key-id
·         geo-nonce
·         geo-expires-by
·         geo-signature   

geo-key-id
      
The shared key id will be mapped to a shared secret hashed value. Will need to fetch that hashed value and use it for signature creation.


geo-expires-by
                 This will be a timestamp in milli seconds created by using current timestamp in milli seconds
Code snippet ::
  expiresBy =200
  expiresByTime = System.currentTimeMillis() + (expiresBy * 1000);

geo-nonce
   Use  a UID generator so that each nonce value is unique.

geo-signature-algorithm (FYI)
   Use HMAC-SHAxxx​ algorithm utilities to generate the signature encrypted in SHAxxx.

How to create signatureParts
         Signature parts are used to create signature along with the shared Key

1.        For GET - QueryString
  Sample businessParameters  = transactionId=10&sequenceId=123&status=COMPLETED

Steps:                         
a.          Concatenate all the business parameters, geo-username, geo-key-id, geo-source-system-name, geo-target-system-name, geo-expires-by, geo-nonce

Code snippet:

signatureParts =  ?businessParameters+"&")+
                                 "geo-username="+userName+
                                 "&geo-key-id="+sharedKey+
                                 "&geo-source-system-name="+source+
                                 "&geo-target-system-name="+target+
                                 "&geo-expires-by="+expiresByLStr
                                 +"&geo-nonce="+nonce;

b.       Use a HmacSignature Utility to create signature passing in the hashing algorithm HashingAlgorithm.HMACSHA512, shared key and signature parts.

 Code snippet:    
            signature = HmacSignatureUtil.getSignature(new HmacSignatureRequest(HashingAlgorithm.512,
                                                    (String)secretKeys.get(sharedKey),
                                                    signatureParts)
                                                     );

c.        Once you create the signature, always append the geo-signature as the last key /value to the request.
d.       Once the URL is created encode the URL using UTF-8 encoding.
Code snippet      
encodedURL = serverUrl + "?" + URLEncoder.encode(signatureParts + "&geo-signature=" + signature, "UTF-8");
Output:
transactionId%3D10%26sequenceId%3D123%26deliveryStatus%3DCOMPLETED%26geo-username%3Dgeo%26geo-key-id%3DGeoSystem%26geo-source-system-name%3DINT%26geo-target-system-name%3DHRMS%26geo-expires-by%3D1366739410429%26geo-nonce%3Dbb123%26geo-signature%3D8S%2BIbF8DuIChek4ArARBYTIsEY5GIG%2BrbD5CCisw8oY%3D

e.        Final step is to prepend the service URL to the encoded URL
Output:

https://geo.com:9111/GEOBus/v1/update?transactionId%3D10%26sequenceId%123%26status%3DCOMPLETED%26geo-username%3Dgeo%26geo-key-id%3DSystemX%26geo-source-system-name%3DINT%26geo-target-system-name%3DHRMS%26geo-expires-by%3D1366739410429%26geo-nonce%3Dbb123%26geo-signature%3D8S%2BIbF8DuIChek4ArARBYTIsEY5GIG%2BrbD5CCisw8oY%3D
             

2.        POST – HttpHeader

Steps:                         

a.          Concatenate all the business parameters, geo-username, geo-key-id, geo-expires-by, geo-source-system-name, geo-target-system-name, geo-nonce.
         Code snippet:

    httpHeader = "geo-username="+userName+
                            ",geo-key-id="+sharedKey+
        ",geo-source-system-name="+source+
                            ",geo-target-system-name="+target+
                            ",geo-expires-by="+expiresByLStr+
                            ",geo-nonce="+nonce;

signatureParts = httpHeader + businessParameters;

b.       Use a HmacSignature Utility to create signature passing in the hashing algorithm HashingAlgorithm.HMACSHAxxx, shared key and signature parts.
Code snippet:    
            signature = HmacSignatureUtil.getSignature(new HmacSignatureRequest(HashingAlgorithm.HMACSHA512,
                                                    (String)secretKeys.get(sharedKey),
                                                    signatureParts)
                                                     );
c.        The request header should start with “GEO-Auth:“ ,append the signature parts and then  append the geo-signature as the last key /value as the last parameter.

Code snippet:    
                                                                       
Request Header = "GEO-Auth: "+httpHeader+",geo-signature="+signature;
Output:

GEO-Auth: geo-username=geo,geo-key-id=GEOSystem, geo-source-system-name=INT,
geo-target-system-name=HRMS,geo-expires-by=1366736660196,geo-nonce=aa303,geo-signature=nlw2QyHfEmTgti8ZIZRX3rx8utJn3wY2xJsmOiB7Ds8=

That’s it; you can use the same mechanism in consumer system and end system so that both are in sync.

Implementation in OSB
For rest services, you will need to call the service using java callouts in the OSB to recreate the signature and validate it and for SOAP –OSB/SOA you can do it in Custom OWSM authentication using OWSM policy.

You are all set to be secure J .


References:-
http://hueniverse.com/2008/10/beginners-guide-to-oauth-part-iii-security-architecture/

4 comments:

Marian B. said...

Hello George,

Thanks for a nice article. You wrote you have to do a callout for REST services to consume an OAuth token. I would have a question: is it not possible to implement and use a custom OWSM assertion handling SAML requests in the newest OSB 11g - 11.1.1.7 - PS6?

Thanks!

Marian

George Thomas said...

Yeah it's true.. Owsm supports rest services from PS6

Anonymous said...

Hi George,

Thanks for the post, it is very helpful in understanding nuances of OAuth. However, I am still not sure how to start the implementation in OSB.
If possible, could you send me the code implementing OAuth security in OSB?
Also, is it possible to secure SOA composites as well using OAuth?


Thanks,
Surya.
surya(dot)gvds(at)gmail(dot)com .

George Thomas said...

We had implemented the oauth as a OWSM custom policy, so you can secure both osb and soa applications.

the implementation details will be in java, i will check if i have code with me. It can be your own custom implementation based on oauth spec.In osb you can have a java callout to jar which does the oauth implementation.