OCSP response signed by self-signed trusted responder validation

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OCSP response signed by self-signed trusted responder validation

OpenSSL - User mailing list

Have a question with implementing an OCSP requestor that can handle validating an OCSP response that is not signed by the CA who issued the certificate that we are requesting the OCSP status for but rather, the OCSP response is signed by a self-signed trusted responder that includes the OCSP Signing EKU and the self-signed certificate is configured as trusted on the requesting system.

 

Question is how to get past the check in OCSP_basic_verify() that calls ocsp_check_issuer() with the responder chain and fails in ocsp_match_issuerid() since the issuer ID doesn’t match the self-signed responder certificate ID causing the verify to fail with ‘OCSP routines:OCSP_basic_verify:root ca not trusted in ocsp_vfy.c line 176.’

 

Could someone please shed light on how this is expected to work for this scenario?  Is it expected that the self-signed certificate needs to be added to have explicit trust so that it is allowed via the call to X509_check_trust() or is there something else I’m missing here?

 

Thanks,

Animesh


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Re: OCSP response signed by self-signed trusted responder validation

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The responder isn’t supposed to be self-signed.  It’s supposed to be signed by the CA issuing the certs.  That way you know that the CA “trusts” the responder.

 

Now, having said that, what you want to do is reasonable – think of it as “out of band” trust.  You will probably have to modify the source to support it, however.

 


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Re: OCSP response signed by self-signed trusted responder validation

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Thanks for the quick response Rich!

 

Just a quick follow on.

 

Per RFC6960 for OCSP, there are 3 options:

   All definitive response messages SHALL be digitally signed.  The key
   used to sign the response MUST belong to one of the following:
 
   - the CA who issued the certificate in question
 
   - a Trusted Responder whose public key is trusted by the requestor
 
   - a CA Designated Responder (Authorized Responder, defined in
     Section 4.2.2.2) who holds a specially marked certificate issued
     directly by the CA, indicating that the responder may issue OCSP
     responses for that CA

 

I’m seeing the self-signed and/or even a separate PKI root or hierarchy that is designated to sign responses as the 2nd option above which is essentially an ‘out of band’ trust that is configured on the requestor ahead of time.  Are you saying option 2 from the RFC is not supported within OpenSSL and would require changes?  Or am I misinterpreting option 2 above.

 

Lastly, I assuming my understanding is correct, I was thinking X509_check_trust() allows for communicating this ‘out of band’ trust to OpenSSL for validation of OCSP responses, is this not what this trust setting is for?

 

Thanks,

Animesh

 

From: "Salz, Rich" <[hidden email]>
Date: Tuesday, December 4, 2018 at 12:39 PM
To: "[hidden email]" <[hidden email]>, "[hidden email]" <[hidden email]>
Subject: Re: [openssl-users] OCSP response signed by self-signed trusted responder validation

 

The responder isn’t supposed to be self-signed.  It’s supposed to be signed by the CA issuing the certs.  That way you know that the CA “trusts” the responder.

 

Now, having said that, what you want to do is reasonable – think of it as “out of band” trust.  You will probably have to modify the source to support it, however.

 


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Re: OCSP response signed by self-signed trusted responder validation

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Perhaps you can build a trust store to handle your needs.  I am not sure.

 


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Re: OCSP response signed by self-signed trusted responder validation

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Thanks again Rich.  If anyone else has any ideas please share.

 

From: "Salz, Rich" <[hidden email]>
Date: Tuesday, December 4, 2018 at 12:56 PM
To: "[hidden email]" <[hidden email]>, "[hidden email]" <[hidden email]>
Subject: Re: [openssl-users] OCSP response signed by self-signed trusted responder validation

 

Perhaps you can build a trust store to handle your needs.  I am not sure.

 


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