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[2003:eb:8f1e:2aeb:4ce4:2ed7:e308:c687]) by smtp.gmail.com with ESMTPSA id u6sm1220651ejf.98.2020.08.20.03.52.20 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Aug 2020 03:52:20 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.1\)) From: Torsten Lodderstedt In-Reply-To: Date: Thu, 20 Aug 2020 12:52:19 +0200 Cc: oauth Content-Transfer-Encoding: quoted-printable Message-Id: <46A7D36F-C999-4CA5-AA7F-F955316C4855@lodderstedt.net> References: To: Emond Papegaaij X-Mailer: Apple Mail (2.3608.120.23.2.1) Archived-At: Subject: Re: [OAUTH-WG] Client authentication on token revocation X-BeenThere: oauth@ietf.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: OAUTH WG List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 20 Aug 2020 10:52:25 -0000 Hi Emond,=20 I tend to agree with your assessment. Revoking bearer tokens without = client authentication seems to be better than leaving the attacker the = option to use them to invoke resources.=20 However, if the attacker cannot use the access tokens (e.g. because they = are sender constrained), the attacker could revoke tokens issued to a = confidential client as a kind of DoS attack.=20 best regards, Torsten.=20 > On 20. Aug 2020, at 11:02, Emond Papegaaij = wrote: >=20 > Hi all, >=20 > We are currently implementing the token revocation endpoint (RFC 7009) > on our authorization server and do not understand why it requires > client authentication. When a party (a valid client or not) gets hold > of a valid access token in whatever way, the least damaging it could > do with it, is to revoke it. The current spec allows an attacker to > misuse this token for access to the resource server, but forbids it to > revoke it. This seems strange to me. >=20 > Section 5 of RFC 7009 does not help in this either. It starts to > explain that this authentication is needed to prevent malicious > clients from guessing tokens, but ends with the fact that if this were > possible, much worse damage could be done by using the guessed token > on the resource server. We plan to skip the authentication all > together and simply revoke any valid token presented. How would you > recommend we deal with this? >=20 > Best regards, > Emond Papegaaij > Topicus KeyHub >=20 > _______________________________________________ > OAuth mailing list > OAuth@ietf.org > https://www.ietf.org/mailman/listinfo/oauth