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Monkey Projects OCI Signature Generator

Generates signatures for an HTTP request for OCI.


Why not use the provided Oracle SDK for Java? Because I want a library that is small and has as few dependencies as possible, so I can use it in GraalVM projects. More specifically, to use them in native images for OCI functions.


I have written the code according to the specs provided by Oracle. These were however incomplete, so I also had to reverse engineer their Java code somewhat. But eventually that did the trick.

How to use it?

Clojars Project

Include the library in your project:

{:deps {com.monkeyprojects/oci-sign {:mvn/version ..latest..}}}

Then require the namespace, and invoke the sign-headers and sign functions. The sign-headers takes a regular Ring request, and extracts the headers that should be included in the signature. Which headers depends on the kind of request. It always includes the date, host and a generated value that combines the method and the path. For PUT and POST, it also includes a body hash, but there are exceptions (see below). You can also influence this by passing an additional boolean exclude-body?, to forcibly exclude the body from the signature, even if it is a POST or PUT.

The sign-headers returns a map that can then be passed to sign, which will generate the actual signature using the configuration. The configuration holds a private key, but also values that are used to build a keyId header value. These headers should then be included in your request to the OCI endpoint.

(require '[monkey.oci.sign :as sign])

;; Configuration should be according to spec
(def config {:tenancy-ocid "..."
             :user-ocid "..."
	     :key-fingerprint "..."
	     :private-key some-pk})
(def req {:url "https://some-oci-url"
          :method :get})
;; Generate the signature headers
(def headers (sign/sign config (sign/sign-headers req)))

;; Send the request, e.g. using http-kit
(require '[org.httpkit.client :as http])
(http/get (:url req) {:headers headers})
;; Process the result...

The configuration should contain the :tenancy-ocid, :user-ocid, :key-fingerprint and the :private-key. The private key must be an RSAPrivateKey object. You can get it by reading it from a file and then parse it using the buddy library.

The request must at least contain the :url and :method (as a keyword). You can also add the date but it's best to let the signer generate and format it.


If you're using Martian, you can include an interceptor that is provided by this library to sign requests. It takes the same configuration map as the basic signing functions, with an extra option (exclude-body?, more on that below):

(require '[monkey.oci.sign.martian :as mm])

;; Create Martian context that includes the signer interceptor
(def ctx (martian/bootstrap
	  {:interceptors (concat martian/default-interceptors
	                         [(mm/signer conf)
;; Now send a request
(martian/response-for ctx :my-request {:key "value"})
;; The request will include authorization headers for OCI.

Excluding The Body

Normally, for PUT, POST and PATCH requests, the body will also be included in the signature calculation. However, some requests require special treatment. To allow for this, the signer accepts an additional configuration property, exclude-body? which is a function that takes the request context as argument and returns true if the body should be explicitly excluded, even though it's a request with a body and one of the aforementioned HTTP methods.


Copyright (c) 2023 by Monkey Projects BV. Licensed under MIT

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