Document and file store

Hello Experts,

Lets say I have a dm_document. Of course the content file is stored on content server host. It is possible that I can log on to content server as install owner find the document on physical file store and edit it directly. So in this case can content server detect that the file had been changed?

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DCTM_Guru

The content server is NOT aware of any changes made to the file on the filestore.

I did something similar on past project. Basically, upon file import, we generate a hashkey against the file content and store as an attribute. We then wrote a server job that would recalculate the hashkey and compare it against the attribute value. The plan was to run this job once a year as part of overall system auditing period.

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dnvhariprasad

yes you can go to the filestore and modify the content. To get the path of the file use the below dql

execute get_file_url for '<object id>'

dnvhariprasad

However it is not the recommended way as documentum stores different attributes like content size etc., which will change if you modify the content directly in the physical path.

Imran_Yusubov

thank you very much for the reply, are there any other way like hashing or something that content server will use to determine if there any inconsistency. For example if we go into the document and replace just one letter with another in that case the content size will remain the same but the hash for the document will change.

dnvhariprasad

no. you can modify.

DCTM_Guru

The content server is NOT aware of any changes made to the file on the filestore.

dnvhariprasad

I believe if you have Trusted Content Services, you should not modify..

DCTM_Guru

Hi dnvhariprasad,

I believe the use case is NOT to let someone actually modify the document, but to verify that document has been preserved and not altered via OS level (outside the realm of Documentum).

dnvhariprasad

Hi Johnny Gee

Yes I agree..

Imran_Yusubov

Johnny thank you very much for the information.

The use case is that. We have developed our own digital signature. When ever I sign a document I create an xml rendition for it and copy the signature info etc. into it.You know we use Java xml signature.

Now I want to write a tbo that will check if the signatures are still valid after all other actions that had been performed on the document. In that way I can be sure that no one have changed the document through the docbase actions.If they are valid I have an attribute "signatures_are_valid" I will set it to 1. Based that attribute it is possible to show some icons to end user. So if any one of the signatures is invalid then I will display a red icon to the end user.

But there is one think that could be happen that a hacker or something can log on to the physical server and modify the documents. In that case if content server can't detect that something had changed, then my tbo will never work and the icon will always be the same, green.

But in that case as you say I have to develop my own hash function and work based on it.

DCTM_Guru

"In that way I can be sure that no one have changed the document through the docbase actions."

- If you are just trying to protect manipulation through Content Server, then should be able to detect this by auditing the dm_setfile event. My scenario was more to detect if network sysadmin (not DCTM install owner) manipulated file at the OS level.

lastnitescurry

Imran Yusubov wrote:But there is one think that could be happen that a hacker or something can log on to the physical server and modify the documents. In that case if content server can't detect that something had changed, then my tbo will never work and the icon will always be the same, green. But in that case as you say I have to develop my own  hash function and work based on it.

Buy a TCS licence (Trusted Content Services) and encrypt your file store. That way even if someone gets at the phyiscal file they can not read or edit it

DCTM_Guru

Brian,

Does TCS create a hashkey against the file and store that with sysobject. If it doesnt, then someone who has access to filestore can replace the file with another file? The replacement file could potentially be another file encrypted with TCS, so you really wouldnt know if the file has been tampered with or not.

Imran_Yusubov

Hello,

for now we cant buy TCS. But Johnny, actually I don't need calculating hash of the documents since the signatures themselves are calculated hashes. What I need to do is to create a custom job and validate first signature of the document. In that case if the document had been changed the signature will become invalid which will inform us that something had happened. The job should run often for active documents (active cases), and rarely for archived documents (cases). I guess this is the best option that I can do.