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JSON Web Token (JWT) Profile (RFC7523)

Ory Hydra is capable of performing the JSON Web Token (JWT) Profile for OAuth 2.0 Client Authentication and Authorization Grants. This guide defines how a JWT Bearer Token can be used to request an access token when a client wishes to utilize an existing trust relationship, expressed through the semantics of the JWT, without a direct user-approval step at the authorization server (Hydra).

Ory Hydra supports both methods expressed in RFC 7523:

  • Using JWTs as Authorization Grants: Allows exchanging a JSON Web Token for an Access Token.
  • Using JWTs for Client Authentication: Allows OAuth 2.0 Client Authentication using public/private keys via JSON Web Tokens.

Exchanging JWTs for Access Tokens

To use the Authorization Grant urn:ietf:params:oauth:grant-type:jwt-bearer, the client performs an OAuth 2.0 Access Token Request as defined in Section 4.1 of the OAuth Assertion Framework RFC7521 with the following specific parameter values and encodings:

  • The value of the grant_type is urn:ietf:params:oauth:grant-type:jwt-bearer.
  • The value of the assertion parameter MUST contain a single JWT.

The scope parameter may be used, as defined in the OAuth Assertion Framework RFC7521, to indicate the requested scope:

POST /oauth2/token HTTP/1.1
Host: public.hydra.com
Content-Type: application/x-www-form-urlencoded

grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer
&assertion=eyJhbGciOiJFUzI1NiIsImtpZCI6IjE2In0.
eyJpc3Mi[...omitted for brevity...].
J9l-ZhwP[...omitted for brevity...]

Clients using this grant must be authenticated.

Establishing a Trust Relationship

Before using this grant type, you must establish a trust relationship in Ory Hydra. This involves registering the issuer, subject, and the public key at Ory Hydra's Admin Endpoint:

POST https://<admin.ory-hydra>/trust/grants/jwt-bearer/issuers
Content-Type: application/json

{
// The issuer you want to trust.
"issuer": "https://my-issuer.com",

// The "sub" field of the access token to be created.
"subject": "alice@example.org",

// The allowed scope of the generated access token.
"scope": ["read"],

// The public key with which the JWT Bearer's signature can be verified.
"jwk": {
"kty":"RSA",
"e":"AQAB",
"kid":"d8e91f55-67e0-4e56-a066-6a5f0c2efdf7",
"n":"nzyis1ZjfNB0bBgKFMSvvkTtwlvBsaJq7S5wA-kzeVOVpVWwkWdVha4s38XM_pa_yr47av7-z3VTmvDRyAHcaT92whREFpLv9cj5lTeJSibyr_Mrm_YtjCZVWgaOYIhwrXwKLqPr_11inWsAkfIytvHWTxZYEcXLgAXFuUuaS3uF9gEiNQwzGTU1v0FqkqTBr4B8nW3HCN47XUu0t8Y0e-lf4s4OxQawWD79J9_5d3Ry0vbV3Am1FtGJiJvOwRsIfVChDpYStTcHTCMqtvWbV6L11BWkpzGXSW4Hv43qa-GSYOD2QU68Mb59oSk2OB-BtOLpJofmbGEGgvmwyCI9Mw"
}

// When this trust relationship expires.
"expires_at": "2021-04-23T18:25:43.511Z",
}

The above example would allow the following JWT Bearer

eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwczovL215LWlzc3Vlci5jb20iLCJzdWIiOiJhbGljZUBleGFtcGxlLm9yZyIsImF1ZCI6Imh0dHBzOi8vcHVibGljLmh5ZHJhLmNvbS9vYXV0aDIvdG9rZW4iLCJuYmYiOjEzMDA4MTU3ODAsImV4cCI6MTMwMDgxOTM4MH0.baBiLrVRRU1AKYvAn0X4eIeLvFfpe2wsoD3VTMtaYdbEW2-w-SFeGeEzl5B6sh612bfKkoeihhFVx2md7DP-Rl5asicJzeIhcPETzZbVSPxR1lFdOBwcIPG5N70aSJs2zSn3jnRIhpZf85YZOI8RbQ93Kxla741_4xruHbsNRFqIuWVhxk95BCCnoXzEd8vBTxd_GMn9VijUY_piLPMo-OifRF9pSjYo38aJmRW1tJzeFCMruc9X1W-2c-L_t3rV7zYBH3LlpDZfwyy3T5Pmqf6QKeq1N-MjLnIJcZGT89jqxLmqVFRvAiEyA6iMQXVxmENOnwylGPwuR8DewhWMqg

which has the claims

{
iss: 'https://my-issuer.com',
sub: 'alice@example.org',
aud: 'https://public.hydra.com/oauth2/token',
nbf: 1300815780,
exp: 1300819380
}

to be exchanged for an OAuth2 Access Token (the scope parameter is optional!)

POST /oauth2/token HTTP/1.1
Host: public.hydra.com
Content-Type: application/x-www-form-urlencoded

grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer
&scope=read
&assertion=eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwczovL215LWlzc3Vlci5jb20iLCJzdWIiOiJhbGljZUBleGFtcGxlLm9yZyIsImF1ZCI6Imh0dHBzOi8vcHVibGljLmh5ZHJhLmNvbS9vYXV0aDIvdG9rZW4iLCJuYmYiOjEzMDA4MTU3ODAsImV4cCI6MTMwMDgxOTM4MH0.baBiLrVRRU1AKYvAn0X4eIeLvFfpe2wsoD3VTMtaYdbEW2-w-SFeGeEzl5B6sh612bfKkoeihhFVx2md7DP-Rl5asicJzeIhcPETzZbVSPxR1lFdOBwcIPG5N70aSJs2zSn3jnRIhpZf85YZOI8RbQ93Kxla741_4xruHbsNRFqIuWVhxk95BCCnoXzEd8vBTxd_GMn9VijUY_piLPMo-OifRF9pSjYo38aJmRW1tJzeFCMruc9X1W-2c-L_t3rV7zYBH3LlpDZfwyy3T5Pmqf6QKeq1N-MjLnIJcZGT89jqxLmqVFRvAiEyA6iMQXVxmENOnwylGPwuR8DewhWMqg

with resulting access token claims:

{
"iss": "https://public.hydra.com/",
"sub": "alice@example.org",
"scp": ["read"],
// ...
}

You can also delete, get, and list trust relationships. Please check the HTTP REST API documentation for more details.

OAuth2 JWT Bearer Grant Type Validation

When performing the urn:ietf:params:oauth:grant-type:jwt-bearer Authorization Grant, the JWT Bearer in the assertion parameter is validated as follows:

  1. The JWT MUST contain an iss (issuer) claim that contains a unique identifier for the entity that issued the JWT. The value must match the issuer value of the trust relationship.
  2. The JWT MUST contain a sub (subject) claim identifying the principal that is the subject of the JWT (e.g. user ID). The value must match the subject value of the trust relationship.
  3. The JWT MUST contain an aud (audience) claim containing a value that identifies the authorization server (Hydra) as an intended audience. So this value must be Hydra Token URL.
  4. The JWT MUST contain an exp (expiration time) claim that limits the time window during which the JWT can be used. Can be controlled by oauth2.grant.jwt.max_ttl setting.
  5. The JWT MAY contain an nbf (not before) claim that identifies the time before which the token MUST NOT be accepted for processing by Hydra.
  6. The JWT MAY contain an iat (issued at) claim that identifies the time at which the JWT was issued. Controlled by oauth2.grant.jwt.iat_optional (default false) If iat is not passed, then current time (when assertion is received by Hydra) will be considered as issued date.
  7. The JWT MAY contain a jti (JWT ID) claim that provides a unique identifier for the token. Controlled by oauth2.grant.jwt.jti_optional (default false) setting. Note: If jti is configured to be required, then Hydra will reject all assertions with the same jti, if jti was already used by some assertion, and this assertion is not expired yet (see exp claim).
  8. The JWT MUST be digitally signed.

If a scope was included in the OAuth2 Access Token Request

POST /oauth2/token HTTP/1.1
Host: public.hydra.com
Content-Type: application/x-www-form-urlencoded

grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer
&scope=read
&assertion=...

Hydra will check them against scopes defined in the corresponding trust relationship.

Using JWTs for Client Authentication

Ory Hydra supports OAuth 2.0 Client Authentication with RSA and ECDSA private/public keypairs with currently supported signing algorithms:

  • RS256 (default), RS384, RS512
  • PS256, PS384, PS512
  • ES256, ES384, ES512
  • EdDSA

This authentication method replaces the classic HTTP Basic Authorization and HTTP POST Authorization schemes. Instead of sending the client_id and client_secret, you authenticate the client with a signed JSON Web Token.

To enable this feature for a specific OAuth 2.0 Client, you must set token_endpoint_auth_method to private_key_jwt and register the public key of the RSA/ECDSA signing key either using the jwks_uri or jwks fields of the client.

When authenticating the client at the token endpoint, you generate and sign (with the RSA/ECDSA private key) a JSON Web Token with the following claims:

  • iss: REQUIRED. Issuer. This MUST contain the client_id of the OAuth Client.
  • sub: REQUIRED. Subject. This MUST contain the client_id of the OAuth Client.
  • aud: REQUIRED. Audience. The aud (audience) Claim. Value that identifies the Authorization Server (Ory Hydra) as an intended audience. The Authorization Server MUST verify that it is an intended audience for the token. The Audience SHOULD be the URL of the Authorization Server's Token Endpoint.
  • jti: REQUIRED. JWT ID. 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; any such negotiation is beyond the scope of this specification.
  • exp: REQUIRED. Expiration time on or after which the ID Token MUST NOT be accepted for processing.
  • iat: OPTIONAL. Time at which the JWT was issued.

When making a request to the /oauth2/token endpoint, you include client_assertion_type=urn:ietf:params:oauth:client-assertion-type:jwt-bearer and client_assertion=<signed-jwt> in the request body:

POST /oauth2/token HTTP/1.1
Host: my-hydra.com
Content-Type: application/x-www-form-urlencoded

grant_type=authorization_code&
code=i1WsRn1uB1&
client_id=s6BhdRkqt3&
client_assertion_type=
urn%3Aietf%3Aparams%3Aoauth%3Aclient-assertion-type%3Ajwt-bearer&
client_assertion=PHNhbWxwOl ... ZT

Here's what a client with a jwks containing one RSA public key looks like:

{
"client_id": "rsa-client-jwks",
"jwks": {
"keys": [
{
"kty": "RSA",
"n": "jL7h5wc-yeMUsHGJHc0xe9SbTdaLKXMHvcIHQck20Ji7SvrHPdTDQTvZtTDS_wJYbeShcCrliHvbJRSZhtEe0mPJpyWg3O_HkKy6_SyHepLK-_BR7HfcXYB6pVJCG3BW-lVMY7gl5sULFA74kNZH50h8hdmyWC9JgOHn0n3YLdaxSWlhctuwNPSwqwzY4qtN7_CZub81SXWpKiwj4UpyB10b8rM8qn35FS1hfsaFCVi0gQpd4vFDgFyqqpmiwq8oMr8RZ2mf0NMKCP3RXnMhy9Yq8O7lgG2t6g1g9noWbzZDUZNc54tv4WGFJ_rJZRz0jE_GR6v5sdqsDTdjFquPlQ",
"e": "AQAB",
"use": "sig",
"kid": "rsa-jwk"
}
]
},
"token_endpoint_auth_method": "private_key_jwt",
"token_endpoint_auth_signing_alg": "RS256"
}

And here is how it looks like for a jwks including an ECDSA public key:

{
"client_id": "ecdsa-client-jwks",
"jwks": {
"keys": [
{
"kty": "EC",
"use": "sig",
"crv": "P-256",
"kid": "ecdsa-jwk",
"x": "nQjdhpecjZRlworpYk_TJAQBe4QbS8IwHY1DWkfR0w0",
"y": "UQfLzHxhc4i3EETUeaAS1vDVFJ-Y01hIESiXqqS86Vc"
}
]
},
"token_endpoint_auth_method": "private_key_jwt",
"token_endpoint_auth_signing_alg": "ES256"
}

And here is how it looks like for a jwks including an EdDSA public key:

{
"client_id": "eddsa-client-jwks",
"jwks": {
"keys": [
{
"kty": "OKP",
"use": "sig",
"crv": "Ed25519",
"kid": "eddsa-jwk",
"x": "cg1qGqQGSF6xvzoDZVaDfxu0c2fPhUEuVHYUr1WYVXs"
}
]
},
"token_endpoint_auth_method": "private_key_jwt",
"token_endpoint_auth_signing_alg": "EdDSA"
}

And with jwks_uri:

{
"client_id": "client-jwks-uri",
"jwks_uri": "http://path-to-my-public/keys.json",
"token_endpoint_auth_method": "private_key_jwt",
"token_endpoint_auth_signing_alg": "RS256"
}

The jwks_uri must return a JSON object containing the public keys associated with the OAuth 2.0 Client:

{
"keys": [
{
"kty": "RSA",
"n": "jL7h5wc-yeMUsHGJHc0xe9SbTdaLKXMHvcIHQck20Ji7SvrHPdTDQTvZtTDS_wJYbeShcCrliHvbJRSZhtEe0mPJpyWg3O_HkKy6_SyHepLK-_BR7HfcXYB6pVJCG3BW-lVMY7gl5sULFA74kNZH50h8hdmyWC9JgOHn0n3YLdaxSWlhctuwNPSwqwzY4qtN7_CZub81SXWpKiwj4UpyB10b8rM8qn35FS1hfsaFCVi0gQpd4vFDgFyqqpmiwq8oMr8RZ2mf0NMKCP3RXnMhy9Yq8O7lgG2t6g1g9noWbzZDUZNc54tv4WGFJ_rJZRz0jE_GR6v5sdqsDTdjFquPlQ",
"e": "AQAB",
"use": "sig",
"kid": "rsa-jwk"
}
]
}