SPF Check

A high-performance web service that checks if a target domain is included (directly or indirectly) in another domain's SPF (Sender Policy Framework) record chain.

Features

• 🚀 Fast asynchronous DNS lookups
• 🔄 Recursive checking of SPF include chains
• 📋 Returns complete SPF record and include chain information
• 💓 Health check endpoint

API

Check SPF Record

Checks if a target domain is included in another domain's SPF record chain.

GET /api/v1/check-spf?domain={domain}&target={target}

Parameters

• domain: The domain to check the SPF record for (e.g., example.com)
• target: The domain to look for in the SPF include chain (e.g., _spf.example.com)

Success Response

{
    "found": true,
    "checked_domains": 3,
    "domain": "example.com",
    "target": "spf.protection.outlook.com",
    "elapsed_ms": 42,
    "has_spf_record": true,
    "spf_record": "v=spf1 include:spf.protection.outlook.com -all",
    "included_domains": ["spf.protection.outlook.com"]
}

• found: Boolean indicating if the target was found in the SPF chain
• checked_domains: Number of domains checked in the process
• domain: The original domain that was checked
• target: The domain that was searched for
• elapsed_ms: Time taken for the check in milliseconds
• has_spf_record: Boolean indicating if the domain has an SPF record
• spf_record: The complete SPF record of the main domain (if exists, otherwise null)
• included_domains: List of domains included in the main SPF record (if exists, otherwise null)

Error Response

{
    "error": "DNS_LOOKUP_FAILED"
}

Common error codes:

• DNS_LOOKUP_FAILED: Unable to perform DNS lookup or TXT record does not exist
• SPF_PARSE_FAILED: Invalid SPF record format

Health Check

GET /health

Returns 200 OK if the service is running.

Example Usage

Check if outlook.com's SPF is included in example.com's SPF chain:

curl "http://localhost:8080/api/v1/check-spf?domain=example.com&target=spf.protection.outlook.com"

Installation

1. Ensure you have Rust installed
2. Clone the repository
3. Build and run:

cargo build --release
./target/release/spf-check

The service will listen on 0.0.0.0:8080 by default.

Performance

• Asynchronous processing allows handling multiple requests simultaneously
• Each request maintains its own state, preventing cross-request interference
• Efficient DNS caching through the trust-dns-resolver

Dependencies

• axum: Web framework
• tokio: Async runtime
• trust-dns-resolver: DNS resolution
• decon-spf: SPF record parsing
• serde: Serialization/Deserialization
• chrono: Timestamp formatting