native sso: id_token validation?

[Joseph Heenan]

https://openid.net/specs/openid-connect-native-sso-1_0.html#rfc.section.4.3 does not seem to include any requirement to validate the id_token, e.g. the signature?

I think that means if I have the device_secret & id_token for one session, and an id_token for another session I want to attack, I can:

1. edit the second id_token to include ds_hash for the first session
2. exchange the device_secret and modified id_token for an access token for the second session

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[Nat Sakimura]

+1 for checking the signature.

[gffletch]

Adding the following step in that section…

“Verify the id_token for integrity protection by validating the signature of the id_token JWT.”

Recommendations for text suggestions gladly accepted

[gffletch]

Note that this is a normative change from the spec perspective though hopefully implementations where doing this already

[Joseph Heenan]

I was certainly hoping they were already doing it :-)

I have a nagging feeling there should be slightly more validation, but I’m not sure exactly what. Probably it feels like there should be something that stops a valid client using a device_secret and id_token not intended for it, but I’m not sure how to achieve that.

[gffletch]

Great point. I will update the security considerations section.

[Michael Jones]

Fixed by https://bitbucket.org/openid/connect/pull-requests/306