GenerateJWT policy

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What

Generates a signed JWT, with a configurable set of claims. The JWT can then be returned to clients, transmitted to backend targets, or used in other ways. See JWS and JWT policies overview for a detailed introduction.

Video

Watch a short video to learn how to generate a signed JWT.

Samples

• Generate a JWT signed with the HS256 algorithm
• Generate a JWT signed with the RS256 algorithm

Generate a JWT signed with the HS256 algorithm

This example policy generates a new JWT and signs it using the HS256 algorithm. HS256 relies on a shared secret for both signing and verifying the signature.

When this policy action is triggered, Edge encodes the JWT header and payload, then digitally signs the JWT. See the video above for a complete example, including how to make a request to the policy.

The policy configuration here will create a JWT with a set of standard claims as defined by the JWT specification, including an expiry of 1 hour, as well as an additional claim. You can include as many additional claims as you wish. See the Element reference for details on the requirements and options for each element in this sample policy.

<GenerateJWT name="JWT-Generate-HS256">
    <DisplayName>JWT Generate HS256</DisplayName>
    <Algorithm>HS256</Algorithm>
    <IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables>
    <SecretKey>
        <Value ref="private.secretkey"/>
        <Id>1918290</Id>
    </SecretKey>
    <ExpiresIn>1h</ExpiresIn>
    <Subject>monty-pythons-flying-circus</Subject>
    <Issuer>urn://apigee-edge-JWT-policy-test</Issuer>
    <Audience>fans</Audience>
    <Id/>
    <AdditionalClaims>
        <Claim name="show">And now for something completely different.</Claim>
    </AdditionalClaims>
    <OutputVariable>jwt-variable</OutputVariable>
</GenerateJWT>

The resulting JWT will have this header …

{
  "typ" : "JWT", 
  "alg" : "HS256",
  "kid" : "1918290"
}

… and will have a payload with contents something like this:

{ 
  "sub" : "monty-pythons-flying-circus",
  "iss" : "urn://apigee-edge-JWT-policy-test",
  "aud" : "show",
  "iat" : 1506553019,
  "exp" : 1506556619,
  "jti" : "BD1FF263-3D25-4593-A685-5EC1326E1F37",
  "show": "And now for something completely different."
}

The value of the iat, exp, and jti claims will vary.

Generate a JWT signed with the RS256 algorithm

This example policy generates a new JWT and signs it using the RS256 algorithm. Generating an RS256 signature relies on an RSA private key, which must be provided in PEM-encoded form. See the video above for a complete example, including how to make a request to the policy.

When this policy action is triggered, Edge encodes and digitally signs the JWT, including the claims. To learn about the parts of a JWT and how they are encrypted and signed, refer to RFC7519.

<GenerateJWT name="JWT-Generate-RS256">
    <Algorithm>RS256</Algorithm>
    <IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables>
    <PrivateKey>
        <Value ref="private.privatekey"/>
        <Password ref="private.privatekey-password"/>
        <Id ref="private.privatekey-id"/>
    </PrivateKey>
    <Subject>apigee-seattle-hatrack-montage</Subject>
    <Issuer>urn://apigee-edge-JWT-policy-test</Issuer>
    <Audience>urn://c60511c0-12a2-473c-80fd-42528eb65a6a</Audience>
    <ExpiresIn>60m</ExpiresIn>
    <Id/>
    <AdditionalClaims>
        <Claim name="show">And now for something completely different.</Claim>
    </AdditionalClaims>
    <OutputVariable>jwt-variable</OutputVariable>
</GenerateJWT>

Setting the key elements

The elements that you use to specify the key used to generate the JWT depend on the chosen algorithm, as shown in the following table:

<SecretKey>
  <Value ref="private.secretkey"/>
  <Id>1918290</Id>
</SecretKey>

<PrivateKey>
  <Value ref="private.privatekey"/>
  <Password ref="private.privatekey-password"/>
  <Id ref="private.privatekey-id"/>
</PrivateKey>

Element reference for Generate JWT

The policy reference describes the elements and attributes of the Generate JWT policy.

Note: Configuration will differ somewhat depending on the encryption algorithm you use. Refer to the Samples for examples that demonstrate configurations for specific use cases.

Attributes that apply to the top-level element

<GenerateJWT name="JWT" continueOnError="false" enabled="true" async="false">

The following attributes are common to all policy parent elements.

<DisplayName>

<DisplayName>Policy Display Name</DisplayName>

Use in addition to the name attribute to label the policy in the management UI proxy editor with a different, natural-language name.

<Algorithm>

<Algorithm>algorithm-here</Algorithm>

Specifies the encryption algorithm to sign the token.

<Audience>

<Audience>audience-here</Audience>

or:

<Audience ref='variable_containing_audience'/>

The policy generates a JWT containing an aud claim set to the specified value. This claim identifies the recipients that the JWT is intended for. This is one of the registered claims mentioned in RFC7519.

<AdditionalClaims/Claim>

<AdditionalClaims>
    <Claim name='claim1'>explicit-value-of-claim-here</Claim>
    <Claim name='claim2' ref='variable-name-here'/>
    <Claim name='claim3' ref='variable-name-here' type='boolean'/>
</AdditionalClaims>

or:

<AdditionalClaims ref='claim_payload'/>

Lets you specify additional claim name/value pair(s) in the payload of the JWT. You can specify the claim explicitly as string, a number, a boolean, a map, or an array. A map is simply a set of name/value pairs.

The <Claim> element takes these attributes:

• name - (Required) The name of the claim.
• ref - (Optional) The name of a flow variable. If present, the policy will use the value of this variable as the claim. If both a ref attribute and an explicit claim value are specified, the explicit value is the default, and is used if the referenced flow variable is unresolved.
• type - (Optional) One of: string (default), number, boolean, or map
• array - (Optional) Set to true to indicate if the value is an array of types. Default: false.

When you include the <Claim> element, the claim names are set statically when you configure the policy. Alternatively, you can pass a JSON object to specify the claim names. Because the JSON object is passed as a variable, the claim names in the generated JWT are determined at runtime.

For example:

<AdditionalClaims ref='json_claims'/>

Where the variable json_claims contains a JSON object in the form:

{
  "sub" : "person@example.com",
  "iss" : "urn://secure-issuer@example.com",
  "non-registered-claim" : {
    "This-is-a-thing" : 817,
    "https://example.com/foobar" : { "p": 42, "q": false }
  }
}

The generated JWT includes all of the claims in the JSON object.

<AdditionalHeaders/Claim>

<AdditionalHeaders>
    <Claim name='claim1'>explicit-value-of-claim-here</Claim>
    <Claim name='claim2' ref='variable-name-here'/>
    <Claim name='claim3' ref='variable-name-here' type='boolean'/>
    <Claim name='claim4' ref='variable-name' type='string' array='true'/>
 </AdditionalHeaders>

Puts the additional claim name/value pair(s) in the header for the JWT.

The <Claim> element takes these attributes:

• name - (Required) The name of the claim.
• ref - (Optional) The name of a flow variable. If present, the policy will use the value of this variable as the claim. If both a ref attribute and an explicit claim value are specified, the explicit value is the default, and is used if the referenced flow variable is unresolved.
• type - (Optional) One of: string (default), number, boolean, or map
• array - (Optional) Set to true to indicate if the value is an array of types. Default: false.

<CriticalHeaders>

<CriticalHeaders>a,b,c</CriticalHeaders>

or:

<CriticalHeaders ref=’variable_containing_headers’/>

Adds the critical header, crit, to the JWT header. The crit header is an array of header names that must be known and recognized by the JWT receiver. For example:

{
  “typ: “...”,
  “alg” : “...”,
  “crit” : [ “a”, “b”, “c” ],
}

At runtime, the VerifyJWT policy examines the crit header. For each item listed in the crit header, it checks that the <KnownHeaders> element of the VerifyJWT policy also lists that header. Any header that the VerifyJWT policy finds in crit that is not also listed in <KnownHeaders> causes the VerifyJWT policy to fail.

<CustomClaims>

Note: Currently, a CustomClaims element is inserted when you add a new GenerateJWT policy through the UI. This element is not functional and is ignored. The correct element to use instead is <AdditionalClaims>. The UI will be updated to insert the correct elements at a later time.

<ExpiresIn>

<ExpiresIn>time-value-here</ExpiresIn>

Specifies the lifespan of the JWT in milliseconds, seconds, minutes, hours, or days.

<Id>

<Id>explicit-jti-value-here</Id>
 -or-
<Id ref='variable-name-here'/>
 -or-
<Id/>

Generates a JWT with the specific jti claim. When the text value and ref attribute are both empty, the policy will generate a jti containing a random UUID. The JWT ID (jti) claim is a unique identifier for the JWT. For more information on jti, refer to RFC7519.

<IgnoreUnresolvedVariables>

<IgnoreUnresolvedVariables>true|false</IgnoreUnresolvedVariables>

Set to false if you want the policy to throw an error when any referenced variable specified in the policy is unresolvable. Set to true to treat any unresolvable variable as an empty string (null).

<Issuer>

<Issuer ref='variable-name-here'/>
<Issuer>issuer-string-here</Issuer>

The policy generates a JWT containing a claim with name iss, with a value set to the specified value. A claim that identifies the issuer of the JWT. This is one of the registered set of claims mentioned in RFC7519.

<NotBefore>

<!-- Specify an absolute time. -->
<NotBefore>2017-08-14T11:00:21-07:00</NotBefore>
 -or-
<!-- Specify a time relative to when the token is generated. -->
<NotBefore>6h</NotBefore>

Specifies the time when the token becomes valid. The token is invalid until the specified time. You can specify either an absolute time value, or a time relative to when the token is generated.

Valid time values for the NotBefore element for absolute time values

For relative time values, specify an integer and a time period, for example:

• 10s
• 60m
• 12h

<OutputVariable>

<OutputVariable>jwt-variable</OutputVariable>

Specifies where to place the JWT generated by this policy. By default it is placed into the flow variable jwt.POLICYNAME.generated_jwt.

<PrivateKey/Id>

<PrivateKey>
  <Id ref="flow-variable-name-here"/>
</PrivateKey>

or

<PrivateKey>
  <Id>your-id-value-here</Id>
</PrivateKey>

Specifies the key ID (kid) to include in the JWT header. Use only when the algorithm is one of RS256/RS384/RS512, PS256/PS384/PS512, or ES256/ES384/ES512.

<PrivateKey/Password>

<PrivateKey>
  <Password ref="private.privatekey-password"/>
</PrivateKey>

Specify the password the policy should use to decrypt the private key, if necessary. Use the ref attribute to pass the key in a flow variable. Use only when the algorithm is one of RS256/RS384/RS512, PS256/PS384/PS512, or ES256/ES384/ES512.

<PrivateKey/Value>

<PrivateKey>
  <Value ref="private.variable-name-here"/>
</PrivateKey>

Specifies a PEM-encoded private key used to sign the JWT. Use the ref attribute to pass the key in a flow variable. Use only when the algorithm is one of RS256/RS384/RS512, PS256/PS384/PS512, or ES256/ES384/ES512.

<SecretKey/Id>

<SecretKey>
  <Id ref="flow-variable-name-here"/>
</SecretKey>

or

<SecretKey>
  <Id>your-id-value-here</Id>
</SecretKey>

Specifies the key ID (kid) to include in the JWT header of a JWT signed with an HMAC algorithm. Use only when the algorithm is one of HS256/HS384/HS512.

<SecretKey/Value>

<SecretKey>
  <Value ref="private.your-variable-name"/>
</SecretKey>

Provides the secret key used to verify or sign tokens with an HMAC algorithm. Use only when the algorithm is one of HS256/HS384/HS512. Use the ref attribute to pass the key in a flow variable.

Edge enforces a minimum key strength for the HS256/HS384/HS512 algorithms. The minimum key length for HS256 is 32 bytes, for HS384 it is 48 bytes, and for HS512 it is 64 bytes. Using a lower-strength key causes a runtime error.

<Subject>

<Subject>subject-string-here</Subject>

<Subject ref="flow_variable" />

For example:

<Subject ref="apigee.developer.email"/>

The policy generates a JWT containing a sub claim, set to the specified value.This claim identifies or makes a statement about the subject of the JWT. This is one of the standard set of claims mentioned in RFC7519.

Flow variables

The Generate JWT policy does not set flow variables.

Error reference

This section describes the fault codes and error messages that are returned and fault variables that are set by Edge when this policy triggers an error. This information is important to know if you are developing fault rules to handle faults. To learn more, see What you need to know about policy errors and Handling faults.

Runtime errors

These errors can occur when the policy executes.

Deployment errors

These errors can occur when you deploy a proxy containing this policy.

Fault variables

These variables are set when a runtime error occurs. For more information, see What you need to know about policy errors.

Example error response

For error handling, the best practice is to trap the errorcode part of the error response. Do not rely on the text in the faultstring, because it could change.

Example fault rule

    <FaultRules>
        <FaultRule name="JWT Policy Errors">
            <Step>
                <Name>JavaScript-1</Name>
                <Condition>(fault.name Matches "TokenExpired")</Condition>
            </Step>
            <Condition>JWT.failed=true</Condition>
        </FaultRule>
    </FaultRules>