🔒 Domain & SSL: Verifying domain, DNS, and certificate configuration...

Validates DNS records, SSL certificates, redirects, HSTS, and domain health across all managed properties.

Activation

When this skill activates, output:

🔒 Domain & SSL: Running domain health checks...

Then execute the protocol below.

Anti-patterns

Protocol

Step 1: Verify DNS Records

Check that DNS records are correctly configured for the target domain:

# A records (points domain to IP)
dig +short A example.com

# CNAME records (points subdomain to another domain)
dig +short CNAME www.example.com

# TXT records (verification, SPF, DKIM)
dig +short TXT example.com

# MX records (email routing, check for conflicts)
dig +short MX example.com

# NS records (authoritative nameservers)
dig +short NS example.com

Expected patterns by hosting provider:

Check for conflicts:

• ❌ A record AND CNAME on the same subdomain, CNAME takes precedence, A is ignored
• ❌ Multiple A records pointing to different providers: causes random routing
• ❌ Missing TXT record for domain verification: some providers require this

Flag if: DNS records don't match the expected hosting provider configuration.

Step 2: Check SSL Certificate Status

# Check SSL certificate details
echo | openssl s_client -connect example.com:443 -servername example.com 2>/dev/null | openssl x509 -noout -dates -subject -issuer

# Check certificate chain
echo | openssl s_client -connect example.com:443 -servername example.com 2>/dev/null | openssl x509 -noout -text | grep -E "Issuer:|Not Before:|Not After:|Subject:"

# Quick expiration check
echo | openssl s_client -connect example.com:443 -servername example.com 2>/dev/null | openssl x509 -noout -enddate

Verify:

• ✅ Certificate is valid (not expired)
• ✅ Certificate covers the correct domain(s): check Subject Alternative Names
• ✅ Certificate chain is complete (no missing intermediates)
• ✅ Auto-renewal is configured (Let's Encrypt certs expire every 90 days)
• ✅ Certificate issuer matches expected provider (Let's Encrypt, Cloudflare, AWS ACM)

Renewal timeline:

Step 3: Verify www vs non-www Redirect

Pick one canonical form and redirect the other:

# Test non-www → www (or vice versa)
curl -sI http://example.com | grep -i "location"
curl -sI http://www.example.com | grep -i "location"
curl -sI https://example.com | grep -i "location"
curl -sI https://www.example.com | grep -i "location"

Expected redirect chain (non-www canonical):

http://www.example.com  → 301 → https://example.com
http://example.com      → 301 → https://example.com
https://www.example.com → 301 → https://example.com
https://example.com     → 200 (canonical)

Verify:

• ✅ Only ONE canonical URL returns 200, all others 301 redirect to it
• ✅ Redirects use 301 (permanent), not 302 (temporary), 301 is cacheable and SEO-friendly
• ✅ Redirect chain is at most 1 hop (http://www → https://apex, not http://www → https://www → https://apex)
• ❌ Both www and non-www return 200: duplicate content, split SEO

Step 4: Check HSTS Headers

HTTP Strict Transport Security prevents SSL stripping attacks:

# Check for HSTS header
curl -sI https://example.com | grep -i "strict-transport-security"

Expected:

Strict-Transport-Security: max-age=31536000; includeSubDomains; preload

Warning: preload is hard to undo. Only add it if you're committed to HTTPS permanently. Removing it requires submitting to the HSTS preload removal list and waiting for browser updates.

Flag if: No HSTS header present, or max-age is too short (< 6 months / 15768000).

Step 5: Verify DNS Propagation

After making DNS changes, verify propagation across global nameservers:

# Check propagation from multiple DNS resolvers
for dns in 8.8.8.8 1.1.1.1 208.67.222.222 9.9.9.9; do
  echo "=== $dns ==="
  dig +short A example.com @$dns
done

Also check: dnschecker.org for worldwide propagation view.

Propagation timeline:

Flag if: Different DNS resolvers return different values after 2+ hours, likely a TTL issue or misconfigured record.

Step 6: Check for Mixed Content

Mixed content (HTTP resources loaded on HTTPS pages) triggers browser security warnings:

# Scan built output for http:// references
grep -rn "http://" dist/ build/ out/ public/ 2>/dev/null | grep -v "http://localhost\|http://127\|http://schemas\|http://www.w3.org\|http://xmlns" | head -20

# Check HTML for mixed content
grep -rn 'src="http://\|href="http://\|url("http://' dist/ build/ out/ public/ 2>/dev/null | head -20

# Check for hardcoded HTTP API endpoints
grep -rn "http://" --include="*.ts" --include="*.tsx" --include="*.js" --include="*.jsx" . | grep -v node_modules | grep -v "localhost\|127\.0\.0\|schemas\|w3\.org\|xmlns" | head -20

Common mixed content sources:

• ❌ Hardcoded http:// image URLs, change to https:// or protocol-relative //
• ❌ Third-party scripts loaded over HTTP, update to HTTPS CDN URL
• ❌ API endpoints using http://: update to https://
• ❌ CSS url() references with http://: update to https://
• ✅ http://localhost in development code, acceptable, won't appear in production build

Flag if: Any http:// references found in production build output (excluding localhost and XML namespaces).

Step 7: Domain Monitoring Checklist

Proactive monitoring prevents surprise outages:

# Check WHOIS for expiration (if whois is available)
whois example.com | grep -i "expir"

# Quick SSL expiry check
echo | openssl s_client -connect example.com:443 -servername example.com 2>/dev/null | openssl x509 -noout -enddate

Domain inventory: track for each property:

Domain:       example.com
Registrar:    [Namecheap / GoDaddy / Cloudflare / Google Domains]
Auto-renew:   [Yes / No]
Expires:      [YYYY-MM-DD]
DNS provider: [Cloudflare / Registrar / Route53]
SSL issuer:   [Let's Encrypt / Cloudflare / ACM]
Hosting:      [Railway / Netlify / Vercel]
Canonical:    [https://example.com]

Step 8: Multi-Domain and Wildcard Setup

For projects with multiple domains or subdomains:

Wildcard SSL:

# Check if wildcard cert is installed
echo | openssl s_client -connect example.com:443 -servername example.com 2>/dev/null | openssl x509 -noout -text | grep "DNS:"

Wildcard certs (*.example.com) cover all subdomains at one level:

• ✅ Covers: app.example.com, api.example.com, www.example.com
• ❌ Does NOT cover: example.com (apex): need separate SAN entry
• ❌ Does NOT cover: staging.api.example.com (two levels deep)

Subdomain routing patterns:

Multi-domain for same project: When multiple domains point to the same app (e.g., deedstack.com and www.deedstack.com):

1. Set one as canonical (return 200)
2. All others 301 redirect to canonical
3. Each domain needs its own SSL certificate (or use a multi-SAN cert)
4. Update Content-Security-Policy and CORS origins to include all domains

Output domain health report:

🔒 Domain & SSL: Health Report

Domain: example.com
DNS:         ✅ A record → 76.76.21.21 (Vercel)
SSL:         ✅ Let's Encrypt, expires 2026-05-15 (75 days)
HSTS:        ✅ max-age=31536000; includeSubDomains
Redirect:    ✅ www → apex (301)
HTTPS force: ✅ http → https (301)
Mixed content: ✅ none detected
Registrar:   Cloudflare (auto-renew ON, expires 2027-01-20)

Subdomains:
  app.example.com  → ✅ Netlify (SSL valid)
  api.example.com  → ✅ Railway (SSL valid)

No issues found. Next check recommended: 2026-04-01

Level History

• Lv.1: Base: DNS verification, SSL certificate checks, www/non-www redirects, HSTS validation, DNS propagation testing, mixed content scanning, domain monitoring checklist, multi-domain/wildcard setup. Based on managing adminstack.pro, epsteinscan.org, deedstack.com, and related properties. (Origin: MemStack Pro v3.2, Mar 2026)