validate: check record value formats, run the same check before every deploy

.github/scripts/deploy.js

@@ -1,5 +1,6 @@
 const fs = require("fs");
 const path = require("path");
+const { validateContent } = require("./validate-pr.js");
 
 const API_URL = process.env.SKRIME_API_URL;
 const API_KEY = process.env.SKRIME_API_KEY;
@@ -43,15 +44,21 @@ function collectRecords(domain) {
       const label = file.replace(/\.json$/, "");
       const name = label === "@" ? sub : `${label}.${sub}`;
 
-      const data = JSON.parse(fs.readFileSync(path.join(subDir, file), "utf8"));
+      const where = `${domain}: ${sub}/${file}`;
+      let data;
+      try {
+        data = JSON.parse(fs.readFileSync(path.join(subDir, file), "utf8"));
+      } catch (e) {
+        throw new Error(`${where} is not valid JSON: ${e.message}`);
+      }
+      const problems = validateContent(data, label === "@");
+      if (problems.length) throw new Error(`${where}: ${problems.join("; ")}`);
+
       const recs = data.records || {};
       for (const [type, value] of Object.entries(recs)) {
         const values = Array.isArray(value) ? value : [value];
         for (const v of values) {
-          if (typeof v !== "string" && typeof v !== "number") {
-            throw new Error(`${domain}: ${sub}/${file} ${type} value must be a string, got ${JSON.stringify(v)}`);
-          }
-          records.push({ name, type, data: String(v) });
+          records.push({ name, type, data: v });
         }
       }
     }

.github/scripts/validate-pr.js

@@ -21,6 +21,8 @@
 //      folder, the PR author must be the owner recorded in that folder's
 //      `@.json` on the base branch. If not, the PR is closed automatically.
 
+const net = require("net");
+
 const MARKER = "<!-- subdomain-bot -->";
 
 const ALLOWED_RECORD_TYPES = ["A", "AAAA", "CNAME", "ALIAS", "MX", "SRV", "TXT", "CAA"];
@@ -250,10 +252,7 @@ function validateContent(data, isApex) {
     }
   }
   for (const [t, value] of Object.entries(data.records)) {
-    const values = Array.isArray(value) ? value : [value];
-    if (values.length === 0 || values.some((v) => typeof v !== "string" || v.trim() === "")) {
-      errors.push(`\`${t}\` must be a string or a list of strings (for a record on another name like \`_verify\`, add a separate \`_verify.json\` file)`);
-    }
+    if (ALLOWED_RECORD_TYPES.includes(t)) errors.push(...validateValues(t, value));
   }
   if (types.includes("CNAME") && types.length > 1) {
     errors.push("a `CNAME` record cannot be combined with other record types");
@@ -264,6 +263,58 @@ function validateContent(data, isApex) {
   return errors;
 }
 
+const HOST = /^(?=.{1,253}\.?$)([a-z0-9_]([a-z0-9_-]{0,61}[a-z0-9])?\.)+[a-z]{2,63}\.?$/i;
+
+// Checks the value(s) of one record type. Returns a list of error strings.
+function validateValues(type, value) {
+  const values = Array.isArray(value) ? value : [value];
+  if (values.length === 0) return [`\`${type}\` must not be an empty list`];
+
+  const errors = [];
+  for (const v of values) {
+    if (typeof v !== "string" || v.trim() === "") {
+      errors.push(`\`${type}\` values must be non-empty strings, got \`${JSON.stringify(v)}\` (for a record on another name like \`_verify\`, add a separate \`_verify.json\` file)`);
+      continue;
+    }
+    const bad = (hint) => errors.push(`\`${type}\` value \`${v}\` is invalid: ${hint}`);
+    switch (type) {
+      case "A":
+        if (!net.isIPv4(v)) bad("expected an IPv4 address like `185.199.108.153`");
+        break;
+      case "AAAA":
+        if (!net.isIPv6(v)) bad("expected an IPv6 address like `2606:50c0:8000::153`");
+        break;
+      case "CNAME":
+      case "ALIAS":
+        if (!HOST.test(v)) bad("expected a hostname like `target.example.net`");
+        break;
+      case "MX": {
+        const m = v.match(/^(\d{1,5}) (\S+)$/);
+        if (!m || Number(m[1]) > 65535 || !HOST.test(m[2])) bad("expected `<priority> <host>`, e.g. `10 mail.example.net`");
+        break;
+      }
+      case "SRV": {
+        const m = v.match(/^(\d{1,5}) (\d{1,5}) (\d{1,5}) (\S+)$/);
+        if (!m || m.slice(1, 4).some((n) => Number(n) > 65535) || !(m[4] === "." || HOST.test(m[4]))) {
+          bad("expected `<priority> <weight> <port> <target>`, e.g. `10 5 25565 mc.example.net`");
+        }
+        break;
+      }
+      case "CAA":
+        if (!/^\d{1,3} (issue|issuewild|iodef) \S+$/.test(v)) bad("expected `<flags> <tag> <value>`, e.g. `0 issue letsencrypt.org`");
+        break;
+      case "TXT":
+        if (/^".*"$/.test(v)) bad("leave out the surrounding quotes, they are added automatically");
+        else if (v.length > 2048) bad("longer than 2048 characters");
+        break;
+    }
+  }
+  if ((type === "CNAME" || type === "ALIAS") && values.length > 1) {
+    errors.push(`\`${type}\` must be a single hostname, not a list`);
+  }
+  return errors;
+}
+
 async function listDomains(github, owner, repo, ref) {
   try {
     const res = await github.rest.repos.getContent({ owner, repo, path: "domains", ref });
@@ -313,3 +364,6 @@ async function setLabels(github, owner, repo, issue_number, labels) {
   } catch (e) { /* ignore */ }
   await github.rest.issues.addLabels({ owner, repo, issue_number, labels }).catch(() => {});
 }
+
+// Reused by deploy.js so a broken file can never reach the DNS API.
+module.exports.validateContent = validateContent;

README.md

@@ -110,6 +110,8 @@ Netlify, a server IP, …) at it and you're online.
 | `@.json` must contain an `owner.github` | Anchors who owns the folder |
 | At least one record under `records` | A subdomain has to point somewhere |
 | `CNAME` cannot be combined with other record types | DNS spec |
+| Every value is a plain string in the right format (`A` = IPv4, `AAAA` = IPv6, `CNAME` = one hostname, `MX` = `10 mail.example.net`, `TXT` without quotes) | Broken values would make the whole zone fail to deploy |
+| A record on another name (e.g. `_railway-verify`) goes in its own file `<subdomain>/_railway-verify.json` | One file = one DNS name |
 | Names like `www`, `api`, `mail`, `ns1` … are reserved | Infrastructure protection |
 
 ---