Check Firewalled

Mini HTTP service that takes a JSON with server information and check if it's accessible from the application.

In our use-case, we want the tested server to not be accessible from this application.

An unaddressable server is considered a success.

Env

Key	Requirement	Explanation
SHARED_KEY	mandatory	Secret shared between main app and this one. (Needs to be sent in the header Authorization)
PORT	optional (default 80)	Port used for the application
CHECK_SMTP	optional (default true)	Should the application check for an SMTP server when the server is available.
SMTP_CN	optional (default hostname)	Common Name to use for client certificate when doing a STARTTLS
SMTP_FROM	optional (default local@hostname)	Email to use to do the MAIL FROM smtp command

Data

{
  "server": "example.com",
  "port": 25,
  "mx": false,
  "test_email": "test@example.com"
}

Key	Explanation
server	Server to check
port	Port to use to attempt the connection
mx	Instead of resolving the IP, resolve the MX of the server first then check IPs
test_email	Used as RCPT TO when doing SMTP checks

Result

Success

{
    "request": {
        "server": "example.com",
        "port": 25,
        "mx": false
    },
    "success": true,
    "details": [
        {
            "server": "example.com",
            "ip": "0.0.0.0",
            "result": true,
            "smtp_check_msg": ""
        },
        {
            "server": "example.com",
            "ip": "0.0.0.1",
            "result": true,
            "smtp_check_msg": "[TLS VersionTLS12] Stop at RCPT TO"
        },
    ]
}

Failure

All servers

{
    "request": {
        "server": "example.com",
        "port": 25,
        "mx": false
    },
    "success": false,
    "details": [
        {
            "server": "example.com",
            "ip": "0.0.0.0",
            "result": false,
            "smtp_check_msg": "[TLS VersionTLS12] Can start a SMTP Transaction"
        },
        {
            "server": "example.com",
            "ip": "0.0.0.1",
            "result": false,
            "smtp_check_msg": "[TLS VersionTLS12] Can start a SMTP Transaction"
        },
    ]
}

One servers

{
    "request": {
        "server": "example.com",
        "port": 25,
        "mx": false
    },
    "success": false,
    "details": [
        {
            "server": "example.com",
            "ip": "0.0.0.0",
            "result": false,
            "smtp_check_msg": "[TLS VersionTLS12] Can start a SMTP Transaction"
        },
        {
            "server": "example.com",
            "ip": "0.0.0.1",
            "result": true,
            "smtp_check_msg": ""
        },
    ]
}

Unknown host

{
  "request": {
    "server": "mailcatcher",
    "port": 25,
    "mx": false,
    "testEmail": "test@test.com"
  },
  "success": false,
  "details": [
    {}
  ],
  "errorMessage": "lookup mailcatcher on 127.0.0.1: no such host"
}

zerospam / check-firewall