feat: add requestProcess helper for extracting data from requests

Author: dhensby

Diff for: index.d.ts

@@ -203,6 +203,16 @@ declare namespace OAuth2Server {
         authorizationCodeLifetime?: number;
     }
 
+    interface TokenRequest {
+        grant_type: string;
+        client_assertion?: string;
+        client_assertion_type?: string;
+        client_id?: string;
+        client_secret?: string;
+        code_verifier?: string;
+        scope?: string;
+    }
+
     interface TokenOptions {
         /**
          * Lifetime of generated access tokens in seconds (default = 1 hour)
@@ -233,6 +243,11 @@ declare namespace OAuth2Server {
          * Additional supported grant types.
          */
         extendedGrantTypes?: Record<string, typeof AbstractGrantType>;
+
+        /**
+         * Request processor
+         */
+        requestProcessor?: ((request: Request) => TokenRequest)
     }
 
     interface AssertionCredential {

Diff for: lib/handlers/token-handler.js

@@ -61,6 +61,7 @@ class TokenHandler {
     this.allowExtendedTokenAttributes = options.allowExtendedTokenAttributes;
     this.requireClientAuthentication = options.requireClientAuthentication || {};
     this.alwaysIssueNewRefreshToken = options.alwaysIssueNewRefreshToken !== false;
+    this.requestProcessor = options.requestProcessor;
   }
 
   /**
@@ -85,8 +86,13 @@ class TokenHandler {
     }
 
     try {
-      const client = await this.getClient(request, response);
-      const data = await this.handleGrantType(request, client);
+      const body = this.requestProcessor?.(request) ?? request.body;
+      const req = new Request({
+        ...request,
+        body,
+      });
+      const client = await this.getClient(req, response);
+      const data = await this.handleGrantType(req, client);
       const model = new TokenModel(data, { allowExtendedTokenAttributes: this.allowExtendedTokenAttributes });
       const tokenType = this.getTokenType(model);
 
@@ -247,7 +253,7 @@ class TokenHandler {
       accessTokenLifetime: accessTokenLifetime,
       model: this.model,
       refreshTokenLifetime: refreshTokenLifetime,
-      alwaysIssueNewRefreshToken: this.alwaysIssueNewRefreshToken
+      alwaysIssueNewRefreshToken: this.alwaysIssueNewRefreshToken,
     };
 
     return new Type(options).handle(request, client);