JWK conversion from/to PEM

src/core/operations/JWKToPem.mjs

@@ -0,0 +1,80 @@
+/**
+ * @author cplussharp
+ * @copyright Crown Copyright 2021
+ * @license Apache-2.0
+ */
+
+import r from "jsrsasign";
+import Operation from "../Operation.mjs";
+import OperationError from "../errors/OperationError.mjs";
+
+/**
+ * PEM to JWK operation
+ */
+class PEMToJWK extends Operation {
+
+    /**
+     * PEMToJWK constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "JWK to PEM";
+        this.module = "PublicKey";
+        this.description = "Converts Keys in JSON Web Key format to PEM format (PKCS#8).";
+        this.infoURL = "https://datatracker.ietf.org/doc/html/rfc7517";
+        this.inputType = "string";
+        this.outputType = "string";
+        this.args = [];
+        this.checks = [
+            {
+                "pattern": "\"kty\":\\s*\"(EC|RSA)\"",
+                "flags": "gm",
+                "args": []
+            }
+        ];
+    }
+
+    /**
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {string}
+     */
+    run(input, args) {
+        const inputJson = JSON.parse(input);
+
+        let keys = [];
+        if (Array.isArray(inputJson)) {
+            // list of keys => transform all keys
+            keys = inputJson;
+        } else if (Array.isArray(inputJson.keys)) {
+            // JSON Web Key Set => transform all keys
+            keys = inputJson.keys;
+        } else if (typeof inputJson === "object") {
+            // single key
+            keys.push(inputJson);
+        } else {
+            throw new OperationError("Input is not a JSON Web Key");
+        }
+
+        let output = "";
+        for (let i=0; i<keys.length; i++) {
+            const jwk = keys[i];
+            if (typeof jwk.kty !== "string") {
+                throw new OperationError("Invalid JWK format");
+            } else if ("|RSA|EC|".indexOf(jwk.kty) === -1) {
+                throw new OperationError(`Unsupported JWK key type '${inputJson.kty}'`);
+            }
+
+            const key = r.KEYUTIL.getKey(jwk);
+            const pem = key.isPrivate ? r.KEYUTIL.getPEM(key, "PKCS8PRV") : r.KEYUTIL.getPEM(key);
+
+            // PEM ends with '\n', so a new key always starts on a new line
+            output += pem;
+        }
+
+        return output;
+    }
+}
+
+export default PEMToJWK;