CertificateThumbprintFilter

Extracts a Java certificate from a trusted header or from a TLS connection, computes the SHA-256 thumbprint of that certificate, and makes the thumbprint available for the ConfirmationKeyVerifierAccessTokenResolver. Use this filter to enable verification of certificate-bound access_tokens.

CertificateThumbprintFilter computes and makes available the SHA-256 thumbprint of a client certificate as follows:

  • Evaluates a runtime expression and yields a java.security.cert.Certificate

  • Hashes the certificate using SHA-256

  • Base64url-encodes the result

  • Stores the result in the contexts chain

The runtime expression can access or build a client certificate from any information present at runtime, such as a PEM in a header, or a pre-built certificate.

Use CertificateThumbprintFilter with ConfirmationKeyVerifierAccessTokenResolver when the IG instance is behind the TLS termination point, for example, when IG is running behind a load balancer or other ingress point.

Usage

{
  "name": string,
  "type": "CertificateThumbprintFilter",
  "config": {
    "certificate": runtime expression<certificate>,
    "failureHandler": Handler reference,
  }
}

Properties

"certificate": runtime expression<certificate>, required

An EL expression which, when evaluated, yields an instance of a java.security.cert.Certificate.

Use the following "Functions" in the expression to define hash, decoding, and certificate format:

  • digestSha256, to calculate the SHA-256 hash of the certificate.

  • decodeBase64url, to decode an incoming base64url-encoded string.

  • pemCertificate, to convert a PEM representation string into a certificate.

See "Examples".

"failureHandler": handler reference, optional

Handler to treat the request on failure.

Provide an inline handler configuration object, or the name of a handler object declared in the heap. See also Handlers.

Default: HTTP 403 Forbidden, the request stops being executed.

Examples

The following example use the certificate associated with the incoming HTTP connection: 

{
  "name": "CertificateThumbprintFilter-1",
  "type": "CertificateThumbprintFilter",
  "config": {
    "certificate": "${contexts.client.certificates[0]}"
  }
}

The following example is adapted for a deployment with NGINX as the TLS termination, where NGINX fronts IG. NGINX provides the client certificate associated with its own incoming connection in the x-ssl-client-cert header. The certificate is encoded as PEM, and then url-encoded: 

{
  "name": "CertificateThumbprintFilter-2",
  "type": "CertificateThumbprintFilter",
  "config": {
    "certificate": "${pemCertificate(urlDecode(request.headers['x-ssl-client-cert'][0]))}"
  }
}
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