feat: initial enforcement of template policy

backend/src/services/certificate-template/certificate-template-fns.ts

@@ -0,0 +1,28 @@
+import ms from "ms";
+
+import { BadRequestError } from "@app/lib/errors";
+
+export const validateCertificateDetailsAgainstTemplate = (
+  cert: {
+    commonName: string;
+    notBeforeDate: Date;
+    notAfterDate: Date;
+  },
+  template: {
+    commonName: string;
+    ttl: string;
+  }
+) => {
+  const commonNameRegex = new RegExp(template.commonName);
+  if (!commonNameRegex.test(cert.commonName)) {
+    throw new BadRequestError({
+      message: "Invalid common name based on template policy"
+    });
+  }
+
+  if (cert.notAfterDate.getTime() - cert.notBeforeDate.getTime() > ms(template.ttl)) {
+    throw new BadRequestError({
+      message: "Invalid validity date based on template policy"
+    });
+  }
+};