progress

.gitignore

@@ -1,3 +1,10 @@
+# Application files
+tokens
+hosts
+
+# vim
+*.swp
+
 # Byte-compiled / optimized / DLL files
 __pycache__/
 *.py[cod]

README.md

@@ -0,0 +1,59 @@
+# Motivations
+
+ * Delegate DNS management while maintaining the smallest footprint ever.
+ * Do whatever is necessary to keep customized code to a minimum.
+I wanted to use off-the-shelf components where possible.
+ * Provide a convenient interface for managing DNS records.
+ * Do as little as possible as `root`.
+
+# Usage
+Visit the Swagger or Redoc documentation at `/docs/` or `/redoc`, respectively.
+It's a simple path-based HTTP API.
+
+## Token File
+The token file is a brain-dead access control mechanism. It is a file that
+contains a single "API Key" per line. You are free to mint and distribute
+API Keys that users can include in the `X-MASKER-TOKEN` header with their
+requests.
+
+## Hosts File
+The hosts file is created and managed by `dnsmasker`. It follows the
+standard hosts file convention: `IP address <tab> Name`
+
+
+# Setup
+
+## Python Application
+
+```sh
+$ python -m venv .venv
+$ source .venv/bin/acticate
+$ pip install -r requirements.txt
+
+# run the application
+$ flask run server.py --host 0.0.0.0 --port 8000
+```
+
+## Sudoers configuration
+
+```
+# allow 'user' to hup dnsmasq
+user ALL=(root) pkill -HUP dnsmasq
+```
+
+## dnsmasq.conf
+Modify the dnsmasq configuration file to use a custom
+hosts file and prevent any forwarding loops.
+
+```
+# Use a custom hosts file
+no-hosts
+addn-hosts=/home/user/pydnsmasker/hosts
+
+# Prevent unnecessary forwarding
+domain-needed
+bogus-priv
+no-resolv
+local=/domain/
+local=/domain2/
+```

server.py

@@ -1,9 +1,130 @@
-from fastapi import FastAPI
+import os
+import re
+import subprocess
+from typing import List
+
+from fastapi import Depends, FastAPI, Header, HTTPException
+from fastapi.responses import JSONResponse
+from fastapi.security import APIKeyHeader
+
+TOKEN_FILE = os.getenv("DNSMASKER_TOKEN_FILE", "tokens")
+HOSTS_FILE = os.getenv("DNSMASKER_HOSTS_FILE", "hosts")
+RELOAD_COMMAND = os.getenv("DNSMASKER_RELOAD_CMD", "sudo pkill -HUP dnsmasq")
+API_TOKEN_HEADER = os.getenv("DNSMASKER_API_TOKEN_HEADER", "x-api-token")
 
 app = FastAPI()
 
-@app.get("/")
-@app.get("/status")
-async def status():
-    """Status endpoint"""
-    return {"message": "Hello World!"}
+header_scheme = APIKeyHeader(name=API_TOKEN_HEADER)
+
+
+def update_hosts_file(registry):
+    """Writes the hosts file."""
+    hosts_file = ["# managed by dnsmasker"]
+    ip_registry = {}
+    for service, ips in registry.items():
+        for ip in ips:
+            if ip in ip_registry:
+                ip_registry[ip].append(service)
+            else:
+                ip_registry[ip] = [service]
+
+    for ip, services in ip_registry.items():
+        line = f"{ip}\t {' '.join(services)}"
+        hosts_file.append(line)
+
+    with open(HOSTS_FILE, "w") as fd:
+        fd.write("\n".join(hosts_file))
+
+
+def check_token(token: str = Depends(header_scheme)):
+    """Check if provided token is valid."""
+    try:
+        with open(TOKEN_FILE, "r") as fd:
+            tokens = fd.read().split("\n")
+        if token not in tokens:
+            raise HTTPException(status_code=403, detail="Unauthorized")
+    except KeyError:
+        raise HTTPException(status_code=403, detail="Unauthorized")
+
+
+@app.post("/reload", dependencies=[Depends(check_token)])
+def reload_config():
+    """Tell dnsmasq to reload the config and refresh its cache."""
+    command = RELOAD_COMMAND.split()
+    proc = subprocess.run(command)
+    if proc.returncode != 0:
+        raise HTTPException(
+            status_code=500, detail=f"Unable to reload dnsmasq with: {command}"
+        )
+    else:
+        return "success"
+
+
+@app.post("/service/{name}/{ip}", dependencies=[Depends(check_token)])
+async def register_service(name: str, ip: str):
+    """Add a service to the catalog"""
+    registry = await read_services()
+    if name in registry:
+        registry[name].append(ip)
+    else:
+        registry[name] = [ip]
+
+    update_hosts_file(registry)
+    return registry
+
+
+@app.delete("/service/{name}/{ip}", dependencies=[Depends(check_token)])
+async def register_service(name: str, ip: str):
+    """Remove a service to the catalog"""
+    registry = await read_services()
+    if name in registry:
+        current = registry[name]
+        updated = [addr for addr in current if addr != ip]
+        registry[name] = updated
+        update_hosts_file(registry)
+    return registry
+
+@app.get("/service/{name}")
+async def read_service(name: str):
+    """Reads the hosts file, produces a service catalog entry."""
+    catalog = {}
+
+    with open(HOSTS_FILE, "r") as fd:
+        hosts_file = fd.read().split("\n")
+        entries = [
+            entry for entry in hosts_file if not entry.startswith("#") and entry != "\n"
+        ]
+        for entry in entries:
+            match = re.match(r"\s*(\d+\.\d+\.\d+\.\d+)\s+(.+)", entry)
+            if match:
+                ip_address = match.group(1)
+                hostnames = match.group(2).split()
+                for hostname in hostnames:
+                    if hostname not in catalog:
+                        catalog[hostname] = [ip_address]
+                    else:
+                        catalog[hostname].append(ip_address)
+    return catalog[name]
+
+
+@app.get("/services")
+async def read_services():
+    """Reads the hosts file, produces a service catalog."""
+    catalog = {}
+
+    with open(HOSTS_FILE, "r") as fd:
+        hosts_file = fd.read().split("\n")
+        entries = [
+            entry for entry in hosts_file if not entry.startswith("#") and entry != "\n"
+        ]
+        for entry in entries:
+            match = re.match(r"\s*(\d+\.\d+\.\d+\.\d+)\s+(.+)", entry)
+            if match:
+                ip_address = match.group(1)
+                hostnames = match.group(2).split()
+                for hostname in hostnames:
+                    if hostname not in catalog:
+                        catalog[hostname] = [ip_address]
+                    else:
+                        catalog[hostname].append(ip_address)
+    return catalog