compare oauth2 secret tokens with constant-time MessageDigest.isEqual#3165
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reta
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coheigea
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The registration access-token checks in DynamicRegistrationService, the session authenticity token in RedirectionBasedGrantService, and the state token in MemoryClientCodeStateManager all authenticate a request-supplied secret with String.equals, which returns on the first differing byte.
Route them through a new OAuthUtils.compareTokens that wraps MessageDigest.isEqual, the same constant-time idiom already used by compareCertificateThumbprints and the JOSE verifiers.