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The JWT Filter Type (v3alpha1)

The JWT Filter performs JWT validation on a bearer token present in the HTTP header. If the bearer token JWT doesn't validate, or has insufficient scope, an RFC 6750-complaint error response with a www-authenticate header is returned. The list of acceptable signing keys is loaded from a JWK Set that is loaded over HTTP, as specified in the Filter configuration. Only RSA and none algorithms are supported. For more information about how requests are matched to Filter resources and the order in which Filters are executed, please refer to the FilterPolicy Resource documentation.


This doc is an overview of all the fields on the JWT Filter Custom Resource with descriptions of the purpose, type, and default values of those fields. This page is specific to the getambassador.io/v3alpha1 version of the JWT Filter resource. For the newer gateway.getambassador.io/v1alpha1 resource, please see the v1alpha1 JWT Filter api reference.

JWT Filter API Reference

To create a JWT Filter, the spec.type must be set to jwt, and the jwt field must contain the configuration for your JWT Filter.

JWTFilter

FieldTypeDescription
jwksURIstringA URI that returns the JWK Set per RFC 7517. This is required unless validAlgorithms=["none"], in that case verifying the signature of the token is disabled. This is considered unsafe and is discouraged when receiving tokens from untrusted sources.
validAlgorithms[]ValidAlgorithms(Enum)The set of signing algorithms that can be considered when verifying tokens attached to requests. If the token is signed with an algorithm that is not in this list then it will be rejected. If not provided then all supported algorithms are allowed. The list should match the set configured in the iDP, as well as the full set of possible valid tokens maybe received. For example, if you may have previously supported RS256 & RS512 but you have decided to only receive tokens signed using RS512 now. This will cause existing tokens to be rejected.
audiencestringIdentifies the recipient that the JWT is intended for and will be used to validate the provided token is intended for the configured audience. If not provided then aud claim on incoming token is not validated and will be considered valid. If aud is unset on the token by default it will be considered valid even if it doesn't match the audience value. To enforce that a token has the aud claim, then set requireAudience: true.
requireAudienceboolModifies the validation behavior for when the audience claim (aud) is unset on the incoming token. false (default) => if aud claim is unset then claim is considered valid. true => if aud claim is unset then claim/token are invalid
issuerstringIdentifies the expected AuthorizationServer that isssued the token. If not provided then the issuer claim will not be validated. If issuer is unset on the token by default it will be considered valid even if it doesn't match the expected issuer value. To enforce that a token has the issuer claim, then set requireIssuer: true.
requireIssuerboolModifies the validation behavior for when the issuer claim (iss) is unset on the incoming token. false (default) => if aud claim is unset on incoming token then claim is considered valid true => if exp claim is unset then claim is invalid
requireExpiresAtboolModifies the validation behavior for when the expiresAt claim (exp) is unset on the incoming token. false (default) => if exp claim is unset on incoming token then claim is valid true => if exp claim is unset then claim/token are invalid
leewayForExpiresAtDurationAllows token expired by this much to still be considered valid. It is recommend that this is small, so that it only accounts for clock skew and network/application latency.
requireNotBeforeboolModifies the validation behavior for when the not before time claim (nbf) is unset on the incoming token. false (default) => if nbf claim is unset on incoming token then claim is valid true => if nbf claim is unset then claim/token are invalid
leewayForNotBeforeDurationAllows tokens that shouldn't be used until this much in the future to be considered valid. It is recommend that this is small, so that it only accounts for clock skew and network/application latency.
requireIssuedAtboolModifies the validation behavior for when the issuedAt claim (iat) is unset on the incoming token. false (default) => if iat claim is unset on incoming token then claim is valid true => if iat claim is unset then claim/token are invalid
leewayForIssuedAtDurationAllows tokens issued by this much into the future to be considered valid. It is recommend that this is small, so that it only accounts for clock skew and network/application latency.
injectRequestHeaders[]AddHeaderTemplateList of headers that will be injected into the upstream request if allowed through. The headers can pull information from the Token and downstream request headers as values. For example, attaching user email claim to a header from the token.
maxStaleDurationSets the duration that JWKs keys and OIDC discovery responses will be cached, ignoring any caching headers when configured
insecureTLSboolDisables TLS verification for cases when jwksURI begins with https://.
renegotiateTLSEnum (never,onceAsClient,freelyAsClient)Sets whether the JWTFilter will renegotiateTLS with the jwksURI server and if so what supported method of renegotiation will be used.
errorResponseCustomErrorResponseAllows setting a custom Response to the downstream client when an invalid JWT is received.

Duration

Appears On: JWTFilter Duration is a field that accepts a string that will be parsed as a sequence of decimal numbers (metav1.Duration), each with optional fraction and a unit suffix, such as "300ms", "1.5h" or "2h45m". Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h". See Go time.ParseDuration.

ValidAlgorithms

Appears On: JWTFilter The set of signing algorithms that can be considered when verifying tokens attached to requests. If the token is signed with an algorithm that is not in this list then it will be rejected. If not provided then all supported algorithms are allowed. The list should match the set configured in the iDP, as well as the full set of possible valid tokens maybe received. For example, if you may have previously supported RS256 & RS512 but you have decided to only receive tokens signed using RS512 now. This will cause existing tokens to be rejected.

Valid Algorithms is an enum with quite a few entries, the possible values are:

  • "none"
  • ECDSA Algorithms: "ES256", "ES384", "ES512"
  • HMAC-SHA Algorithms: "HS256", "HS384", "HS512"
  • RSA-PSS Algorithms: "PS256", "PS384", "PS512"
  • RSA Algorithms: "RS256", "RS384", "RS512"

AddHeaderTemplate

Appears On: JWTFilter List of headers that will be injected into the upstream request if allowed through. The headers can pull information from the Token and downstream request headers as values. For example, attaching user email claim to a header from the token.

FieldTypeDescription
namestringThe name of the header to inject value into
valuestring (GoLang Template)A Golang template that can dynamically extract request information as the value of the injected header.

value is the value of the header to set and is evaluated as a special GoLang Template. This allows the header value to be set based on the JWT value. The value is specified as a Go text/template string, with the following data made available to it:

  • .token.Raw → The raw JWT (string)
  • .token.Header → The JWT header, as parsed JSON (map[string]interface{})
  • .token.Claims → The JWT claims, as parsed JSON (map[string]interface{})
  • .token.Signature → The token signature (string)
  • .httpRequestHeader → http.Header a copy of the header of the incoming HTTP request. Any changes to .httpRequestHeader (such as by using using .httpRequestHeader.Set) have no effect. It is recommended to use .httpRequestHeader.Get instead of treating it as a map, in order to handle capitalization correctly.

Also available to the template are the standard functions available to Go text/templates, as well as:

  • a hasKey function that takes the a string-indexed map as arg1, and returns whether it contains the key arg2. (This is the same as the Sprig function of the same name.)
  • a doNotSet function that causes the result of the template to be discarded, and the header field to not be adjusted. This is useful for only conditionally setting a header field; rather than setting it to an empty string or "<no value>". Note that this does not unset an existing header field of the same name and could be a potential security vulnerability depending on how this is used if an untrusted client spoofs these headers.

CustomErrorResponse

Appears On: JWTFilter Allows setting a custom Response to the downstream client when an invalid JWT is received.

FieldTypeDescription
realmstringIndicates the scope of protection or the application that is checking the token. By default, this is set to the fully qualified name of the JWT Filter as "{name}.{namespace}" to identify which filter rejected the error. This can be overriden to provide more relevant information to end-users.
bodyTemplatestring (GoLang Template)Golang text/template string that will be evaluated and used to build the format returned.
headers[]AddHeaderTemplateAllows providing additional http response headers for the error response. The current maximum is 16 headers, which aligns with the Gateway-API and modified headers on HTTPRoutes.

bodyTemplate specifies body of the error response returned to the downstream client; specified as a Go text/template string, with the following data made available to it:

  • .status_code → The HTTP status code to be returned (int)
  • .httpStatus → An alias for .status_code (int, hidden from {{ . | json "" }})
  • .message → The error message (string)
  • .error → The raw Go error object that generated .message (error, hidden from {{ . | json "" }})
  • .error.ValidationError → The JWT validation error, will be nil if the error is not purely JWT validation (jwt.ValidationError insufficient scope, malformed or missing Authorization header)
  • .request_id → The Envoy request ID, for correlation (string, hidden from {{ . | json "" }} unless .status_code is in the 5xx range)
  • .requestId → An alias for .request_id (string, hidden from {{ . | json "" }})

Also availabe to the template are the standard functions available to Go text/templates, as well as:

  • A json function that formats arg2 as JSON, using the arg1 string as the starting indentation. For example, the template {{ json "indent>" "value" }} would yield the string indent>"value".
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