VerifyJWT policy

What

Verifies the signature on a JWT received from clients or other systems. This policy also extracts the claims into context variables so that subsequent policies or conditions can examine those values to make authorization or routing decisions.

When this policy executes, Edge verifies the signature of a JWT, and verifies that the JWT is valid according to the expiry and not-before times if they are present. The policy can optionally also verify the values of specific claims on the JWT, such as the subject, the issuer, the audience, or the value of additional claims.

If the JWT is verified and valid, then all of the claims contained within the JWT are extracted into context variables for use by subsequent policies or conditions, and the request is allowed to proceed. If the JWT signature cannot be verified or if the JWT is invalid because of one of the timestamps, all processing stops and an error is returned in the response.

To learn about the parts of a JWT and how they are encrypted and signed, refer to RFC7519.

Video

Watch a short video to learn how to verify the signature on a JWT.

Samples

Verify a JWT signed with the HS256 algorithm

This example policy verifies a JWT that was signed with the HS256 encryption algorithm, HMAC using a SHA-256 checksum.

The policy configuration includes the information Edge needs to decode and evaluate the JWT, such as where to find the JWT (in a flow variable specified in the Source element), the required signing algorithm, where to find the secret key (stored in an Edge flow variable, which could have been retrieved from the Edge KVM, for example), and a set of required claims and their values.

<VerifyJWT name="JWT-Verify-HS256">
    <DisplayName>JWT Verify HS256</DisplayName>
    <Algorithm>HS256</Algorithm>
    <Source>request.formparam.jwt</Source>
    <IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables>
    <SecretKey>
        <Value ref="private.secretkey"/>
    </SecretKey>
    <Subject>monty-pythons-flying-circus</Subject>
    <Issuer>urn://apigee-edge-JWT-policy-test</Issuer>
    <Audience>fans</Audience>
    <AdditionalClaims>
        <Claim name="show">And now for something completely different.</Claim>
    </AdditionalClaims>
</VerifyJWT>

Verify a JWT signed with the RS256 algorithm

This example policy verifies a JWT that was signed with the RS256 algorithm. For signing, a private key must be provided, and to verify, you need to provide the corresponding public key.

See the Element reference for details on the requirements and options for each element in this sample policy.

<VerifyJWT name="JWT-Verify-RS256">
    <Algorithm>RS256</Algorithm>
    <Source>json.jwt</Source>
    <IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables>
    <PublicKey>
        <Value ref="public.publickey"/>
    </PublicKey>
    <Subject>apigee-seattle-hatrack-montage</Subject>
    <Issuer>urn://apigee-edge-JWT-policy-test</Issuer>
    <Audience>urn://c60511c0-12a2-473c-80fd-42528eb65a6a</Audience>
    <AdditionalClaims>
        <Claim name="show">And now for something completely different.</Claim>    
    </AdditionalClaims>
</VerifyJWT>

For the above configuration, a JWT with this header …

{
  "typ" : "JWT", 
  "alg" : "RS256"
}

And this payload …

{ 
  "sub" : "apigee-seattle-hatrack-montage",
  "iss" : "urn://apigee-edge-JWT-policy-test",
  "aud" : "urn://c60511c0-12a2-473c-80fd-42528eb65a6a",
  "show": "And now for something completely different."
}

… will be deemed as valid, if the signature can be verified with the provided public key.

A JWT with the same header but with this payload …

{ 
  "sub" : "monty-pythons-flying-circus",
  "iss" : "urn://apigee-edge-JWT-policy-test",
  "aud" : "urn://c60511c0-12a2-473c-80fd-42528eb65a6a",
  "show": "And now for something completely different."
}

… will be determined to be invalid, even if the signature can be verified, because the "sub" claim included in the JWT does not match the required value of the "Subject" element as specified in the policy configuration.

Element reference

The policy reference describes the elements and attributes of the Verify 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

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

The following attributes are common to all policy parent elements.

Attribute Description Default Presence
name The internal name of the policy. Characters you can use in the name are restricted to: A-Z0-9._\-$ %. However, the Edge management UI enforces additional restrictions, such as automatically removing characters that are not alphanumeric.

Optionally, use the <displayname></displayname> element to label the policy in the management UI proxy editor with a different, natural-language name.

N/A Required
continueOnError Set to false to return an error when a policy fails. This is expected behavior for most policies.

Set to true to have flow execution continue even after a policy fails.

false Optional
enabled Set to true to enforce the policy.

Set to false to "turn off" the policy. The policy will not be enforced even if it remains attached to a flow.

true Optional
async This attribute is deprecated. false Deprecated

<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.

Default If you omit this element, the value of the policy's name attribute is used.
Presence Optional
Type String

<Algorithm>

<Algorithm>HS256|RS256</Algorithm>

Specifies the encryption algorithm to sign the token. RS256 employs a public/secret key pair, while HS256 employs a shared secret. See also About signature encryption algorithms.

Default N/A
Presence Required
Type String
Valid values HS256, HS384, HS512, RS256, RS384, RS512

<Audience>

<Audience>audience-here</Audience>

The policy verifies that the audience claim in the JWT matches the value specified in the configuration. If there is no match, the policy throws an error. This claim identifies the recipients that the JWT is intended for. This is one of the registered claims mentioned in RFC7519.

Default N/A
Presence Optional
Type String
Valid values Anything that identifies the audience.

<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>

Validates that the JWT payload contains the specified additional claim(s) and that the asserted claim values match.

An additional claim uses a name that is not one of the standard, registered JWT claim names. The value of a additional claim can be a string, a number, a boolean, a map, or an array. A map is simply a set of name/value pairs. The value for a claim of any of these types can be specified explicitly in the policy configuration, or indirectly via a reference to a flow variable.

Default N/A
Presence Optional
Type String, number, boolean, or map
Array Set to true to indicate if the value is an array of types. Default: false
Valid values Any value that you want to use for an additional claim.

The <Claim> element takes these attribues:

  • 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.

<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>

Validates that the JWT header contains the specified additional claim name/value pair(s) and that the asserted claim values match.

An additionl claim uses a name that is not one of the standard, registered JWT claim names. The value of an additional claim can be a string, a number, a boolean, a map, or an array. A map is simply a set of name/value pairs. The value for a claim of any of these types can be specified explicitly in the policy configuration, or indirectly via a reference to a flow variable.

Default N/A
Presence Optional
Type

String (default), number, boolean, or map.

The type defaults to String if no type is specified.

Array Set to true to indicate if the value is an array of types. Default: false
Valid values Any value that you want to use for an additional claim.

The <Claim> element takes these attribues:

  • 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.

<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.

<Id>

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

Verifies that the JWT has 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.

Default N/A
Presence Optional
Type String, or reference.
Valid values Either a string or the name of a flow variable containing the ID.

<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).

Default False
Presence Optional
Type Boolean
Valid values true or false

<Issuer>

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

The policy verifies that the issuer in the JWT matches the string specified in the configuration element. A claim that identifies the issuer of the JWT. This is one of the registered set of claims mentioned in RFC7519.

Default N/A
Presence Optional
Type String, or reference
Valid values Any

<PublicKey/JWKS>

<PublicKey>
   <JWKS ref="public.jwks"/>
</PublicKey>

or

<PublicKey>
   <JWKS>jwks-value-here</JWKS>
</PublicKey>

Specifies a value in JWKS format (RFC 7517) containing a set of public keys. If the inbound JWT bears a key ID which present in the set of JWKS, then the policy will use the correct public key to verify the JWT signature. For details about this feature, see Using a JSON Web Key Set (JWKS) to verify a JWT.

Default N/A
Presence To verify a JWT using an RSA algorithm, you must either either use the JWKS or Value element.
Type String
Valid values A flow variable or string.

<PublicKey/Value>

<PublicKey>
   <Value ref="public.publickey"/>
</PublicKey>
-or-
<PublicKey>
    <Value>
    -----BEGIN PUBLIC KEY-----
    MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAw2kPrRzcufvUNHvTH/WW
    Q0UrCw5c0+Y707KX3PpXkZGbtTT4nvU1jC0d1lHV8MfUyRXmpmnNxJHAC2F73IyN
    C5TBtXMORc+us7A2cTtC4gZV256bT4h3sIEMsDl0Joz9K9MPzVPFxa1i0RgNt06n
    Xn/Bs2UbbLlKP5Q1HPxewUDEh0gVMqz9wdIGwH1pPxKvd3NltYGfPsUQovlof3l2
    ALvO7i5Yrm96kknfFEWf1EjmCCKvz2vjVbBb6mp1ZpYfc9MOTZVpQcXSbzb/BWUo
    ZmkDb/DRW5onclGzxQITBFP3S6JXd4LNESJcTp705ec1cQ9Wp2Kl+nKrKyv1E5Xx
    DQIDAQAB
    -----END PUBLIC KEY-----
    </Value>
</PublicKey>

Specifies the public key used to verify the signature on the JWT. Use the ref attribute to pass the key in a flow variable, or specify the PEM-encoded key directly. Use this only with the VerifyJWT policy, when the algorithm is an RSA variant.

Default N/A
Presence To verify a JWT signed with an RSA algorithm, you must either either use the JWKS or Value elements.
Type String
Valid values A flow variable or string.

<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.

Default N/A
Presence Required for HMAC algorithms.
Type String
Valid values A flow variable referring to a string.

Note: If a flow variable, it must have the prefix "private". For example, private.mysecret

<Source>

<Source>jwt-variable</Source>

If present, specifies the flow variable in which the policy expects to find the JWT to verify.

Default request.header.authorization (See the note above for important information about the default).
Presence Optional
Type String
Valid values An Edge flow variable name.

<Subject>

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

The policy verifies that the subject in the JWT matches the string specified in the policy configuration. 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.

Default N/A
Presence Optional
Type String
Valid values Any value uniquely identifying a subject.

<TimeAllowance>

<TimeAllowance>120s</TimeAllowance>

The "grace period" for times. For example, if the time allowance is configured to be 60s, then an expired JWT would be treated as still valid, for 60s after the asserted expiry. The not-before-time will be evaluated similarly. Defaults to 0 seconds (no grace period).

Default 0 seconds (no grace period)
Presence Optional
Type String
Valid values An value or a reference to a flow variable containing the value. Time spans can be specified as follows:
  • s = seconds
  • m = minutes
  • h = hours
  • d = days

Flow variables

Upon success, the Verify JWT and Decode JWT policies set context variables according to this pattern:

jwt.{policy_name}.{variable_name}

For example, if the policy name is jwt-parse-token , then the policy will store the subject specified in the JWT to this context variable: jwt.jwt-parse-token.subject

Variable name Description
header.algorithm The signing algorithm used on the JWT. For example, RS256, HS384, and so on.
claim.subject The JWT subject claim.
claim.issuer The JWT issuer claim.
claim.audience The JWT audience claim. This value may be a string, or an array of strings.
claim.expiry The expiration date/time, expressed in seconds since epoch.
expiry_formatted The expiration date/time, formatted as a human-readable string. Example: 2017-09-28T21:30:45.000+0000
seconds_remaining The number of seconds before the token will expire. If the token is expired, this number will be negative.
time_remaining_formatted The time remaining before the token will expire, formatted as a human-readable string. Example: 00:59:59.926
is_expired true or false
claim.issuedat The Date the token was issued, expressed in seconds since epoch.
claim.notbefore If the JWT includes a nbf claim, this variable will contain the value. This is expressed in seconds since epoch.
valid In the case of VerifyJWT, this variable will be true when the signature is verified, and the current time is before the token expiry, and after the token notBefore value, if they are present. Otherwise false.

In the case of DecodeJWT, this variable is not set.

claim.name The value of the named claim (standard or additional). One of these will be set for every claim in the token.
header.name The value of the named header (standard or additional). One of these will be set for every additional header in the token.
header.kid The Key ID, if added when the JWT was generated. See also "Using a JSON Web Key Set (JWKS)" at JWT policies overview to verify a JWT.
header.type Will be set to JWT.
payload-claim-names An array of claims supported by the JWT.
payload-json
Contains the payload in JSON format.
header-json Contains the header in JSON format.

Error reference

TThis 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.

Fault code HTTP status Occurs when
policies.jwt.AlgorithmInTokenNotPresentInConfiguration Occurs when the verification policy has multiple algorithms
policies.jwt.JwtAudienceMismatch 401 The audience claim failed on token verification.
policies.jwt.AlgorithmMismatch 401 The algorithm specified in the Generate policy did not match the one expected in the Verify policy. The algorithms specified must match.
policies.jwt.JwtClaimNotPresent 401 The JWT did not contain a claim on token verification.
policies.jwt.ClaimTypeMismatch 401
policies.jwt.FailedToDecode 401 The policy was unable to decode the JWT. The JWT is possibly corrupted.
policies.jwt.InvalidJwt 401 This error occurs when the JWT signature verification fails.
policies.jwt.InvalidClaim 401
policies.jwt.JwtIssuerMismatch 401 The issuer claim failed on token verification.
policies.jwt.JwtSubjectMismatch 401 The subject claim failed on token verification.
policies.jwt.KeyIdMissing
policies.jwt.KeyParsingFailed
policies.jwt.NoAlgorithmFoundInToken Occurs when the verification policy has multiple algorithms.
policies.jwt.NoMatchingPublicKey From JWKS.
policies.jwt.TokenExpired 401 The policy attempts to verify an expired token.

Deployment errors

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

Error name Occurs when
InvalidJwtAlgorithm The only valid values are: RS256, RS384, RS512, HS256, HS384, and HS512.
InvalidNameForAdditionalClaim

InvalidTypeForAdditionalClaim

InvalidTypeForAdditionalHeader

MissingNameForAdditionalClaim

InvalidNameForAdditionalHeader

MissingNameForAdditionalHeader

InvalidAlgorithm

InvalidConfigurationForVerify

InvalidValueOfArrayAttribute

InvalidConfigurationForActionAndAlgorithmFamily

InvalidEmptyElement

InvalidValueForElement

InvalidFamiliesForAlgorithm

MissingConfigurationElement

InvalidKeyConfiguration

MissingElementForKeyConfiguration

EmptyElementForKeyConfiguration

InvalidPublicKeyValue

InvalidVariableNameForSecret

InvalidSecretInConfig

FailedToResolveVariable

InvalidTimeFormat

InvalidPublicKeyId

Other possible deployment errors.

Fault variables

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

Variables Where Example
fault.name="fault_name" fault_name is the name of the fault, as listed in the Runtime errors table above. The fault name is the last part of the fault code. fault.name Matches "TokenExpired"
jwt.policy_name.failed policy_name is the user-specified name of the policy that threw the fault. jwt.JWT-Policy.failed = true

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.JWT-1.failed=true</Condition>
    </FaultRule>
</FaultRules>