[Openid-specs-ab] Issue #1049: backchannel logout requests should include a reference to the OP (openid/connect)

Phil Hunt phil.hunt at oracle.com
Fri Sep 21 15:38:30 UTC 2018

Interesting. My assumption is iss, aud etc are req’d claims from JWT. 

However maybe a reminder is important?


> On Sep 21, 2018, at 4:52 AM, Hans Zandbelt via Openid-specs-ab <openid-specs-ab at lists.openid.net> wrote:
> New issue 1049: backchannel logout requests should include a reference to the OP
> https://urldefense.proofpoint.com/v2/url?u=https-3A__bitbucket.org_openid_connect_issues_1049_backchannel-2Dlogout-2Drequests-2Dshould-2Dinclude&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=na5FVzBTWmanqWNy4DpctyXPpuYqPkAI1aLcLN4KZNA&m=lm9I-tIhoNwvye6UOWEMPW8NY3NHLUhJ9SotrZMkfjo&s=3LFWnJR17VF0dS5xSTSpiGzBJQ6AFN3Pu3Oa8M3ONMQ&e=
> Hans Zandbelt:
> Whilst taking a stab at implementing backchannel logout according to:
> https://urldefense.proofpoint.com/v2/url?u=https-3A__openid.net_specs_openid-2Dconnect-2Dbackchannel-2D1-5F0.html&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=na5FVzBTWmanqWNy4DpctyXPpuYqPkAI1aLcLN4KZNA&m=lm9I-tIhoNwvye6UOWEMPW8NY3NHLUhJ9SotrZMkfjo&s=L6lYaopVVDpj0Pk2gtvli2CrojHXip4pHWm-fsGlHyQ&e=
> I found that for an RP that connects to multiple OPs it would be impossible to deduct the OP from the `logout_token` if it is encrypted with a symmetric key. Since following the OpenID Connect `id_token` guidelines (as suggested) it would have to decrypt with the `client_secret` which is (hopefully) a per-provider setting. Trying all OPs/`client_secret`'s consecutively would be very inefficient and probably not what anyone would want to do.
> I suggest to add an `iss` parameter to the backchannel logout request in addition to the `logout_token` parameter. 
> This will also make it easier for implementors to share the code path with `id_token` validation since they'd no longer have to "peek" into the `id_token` before calling the validation routine that may be issuer specific. The issuer would typically be known before validating the id_token since it is recorded in the (browser bound) state.
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