Release Network Tools 0.1.0

src/network/dns.ts

@@ -0,0 +1,86 @@
+import { parseIpv4, parseIpv6 } from "@add-ideas/toolbox-helpers";
+
+export type DnsRecordType =
+  "A" | "AAAA" | "CAA" | "CNAME" | "MX" | "SRV" | "TXT";
+
+export interface DnsRecordInput {
+  owner: string;
+  ttl: number;
+  type: DnsRecordType;
+  value: string;
+  priority?: number;
+  weight?: number;
+  port?: number;
+  flag?: number;
+  tag?: "issue" | "issuewild" | "iodef";
+}
+
+const LABEL =
+  /^(?:[A-Za-z0-9_](?:[A-Za-z0-9_-]{0,61}[A-Za-z0-9_])?)(?:\.(?:[A-Za-z0-9_](?:[A-Za-z0-9_-]{0,61}[A-Za-z0-9_])?))*\.?$/u;
+function integer(
+  value: number | undefined,
+  name: string,
+  maximum = 65_535,
+): number {
+  if (!Number.isInteger(value) || value! < 0 || value! > maximum)
+    throw new Error(`${name} must be an integer from 0 to ${maximum}.`);
+  return value!;
+}
+
+function domain(value: string, name: string): string {
+  const candidate = value.trim();
+  if (candidate === "@") return candidate;
+  if (!candidate || candidate.length > 253 || !LABEL.test(candidate))
+    throw new Error(`${name} must be a valid ASCII DNS name.`);
+  return candidate;
+}
+
+function quoteTxt(value: string): string {
+  const bytes = new TextEncoder().encode(value);
+  if (bytes.length > 255)
+    throw new Error("A TXT character-string is limited to 255 UTF-8 bytes.");
+  return `"${value.replaceAll("\\", "\\\\").replaceAll('"', '\\"')}"`;
+}
+
+export function buildDnsRecord(input: DnsRecordInput): string {
+  const owner = domain(input.owner, "Owner");
+  const ttl = integer(input.ttl, "TTL", 2_147_483_647);
+  const value = input.value.trim();
+  if (!value) throw new Error("Record value is required.");
+
+  let data: string;
+  switch (input.type) {
+    case "A":
+      try {
+        data = parseIpv4(value).canonical;
+      } catch {
+        throw new Error("A records require a dotted-decimal IPv4 address.");
+      }
+      break;
+    case "AAAA":
+      try {
+        data = parseIpv6(value).canonical;
+      } catch {
+        throw new Error("AAAA records require an IPv6 address.");
+      }
+      break;
+    case "CNAME":
+      data = domain(value, "Target");
+      break;
+    case "MX":
+      data = `${integer(input.priority, "Priority")} ${domain(value, "Mail exchanger")}`;
+      break;
+    case "SRV":
+      data = `${integer(input.priority, "Priority")} ${integer(input.weight, "Weight")} ${integer(input.port, "Port")} ${domain(value, "Target")}`;
+      break;
+    case "CAA": {
+      const tag = input.tag ?? "issue";
+      data = `${integer(input.flag ?? 0, "Flag", 255)} ${tag} ${quoteTxt(value)}`;
+      break;
+    }
+    case "TXT":
+      data = quoteTxt(value);
+      break;
+  }
+  return `${owner} ${ttl} IN ${input.type} ${data}`;
+}