containers/dane-verify/README.md

🔍 DANE Verify

a small script that verifies TLSA records against live certificates via SMTP STARTTLS.

🤔 How it works

The check.sh script does the heavy lifting:

1. Fetches TLSA records for a target host.
2. Checks for ad (Authentic Data) flag via DNSSEC.
3. Connects to the host via SMTP STARTTLS.
4. Compares the live cert (or public key) hash with what's in your DNS.

🛠 Usage

Docker

You can run it manually to check a domain:

docker run --rm \
  ghcr.io/eleith/containers-dane-verify \
  mail.example.com:25 -r 8.8.8.8

Arguments:

• hostname[:port]: The mail server to check. Port defaults to 25.
• -r resolver (Optional): The DNS resolver to use (e.g., 1.1.1.1).

📦 Tech Stack

• Base: Alpine Linux
• Tools: openssl, bind-tools (dig), awk, bash