Implement SSL (#6)

Introduce backwards compatible SSL.

- [script.py] Add optional argument for ssl-private_key, ssl-public_key and ssl-ca
- [web.py] Add optional ssl_context
- [conftest.py] Pytest utilities to test ssl
- [script_test.py/web_test.py] Add ssl testing

README.rst

@@ -14,7 +14,7 @@ Usage
 -----
 
 The library provides a ``PrometheusExporterScript`` class that serves as an
-entry point to create services that export Prometheus metrics via an HTTP
+entry point to create services that export Prometheus metrics via an HTTP(s)
 endpoint.
 
 Creating a new exporter is just a matter of subclassing
@@ -79,6 +79,9 @@ Exporter command-line
       -L {CRITICAL,ERROR,WARNING,INFO,DEBUG}, --log-level {CRITICAL,ERROR,WARNING,INFO,DEBUG}
                             minimum level for log messages (default: WARNING)
       --process-stats       include process stats in metrics (default: False)
+      --ssl-private-key     full path to the ssl private key
+      --ssl-public-key      full path to the ssl public key
+      --ssl-ca              full path to the ssl certificate authority (CA)
 
 
 Further options can be added by implementing ``configure_argument_parser()``,
@@ -87,6 +90,10 @@ which receives the ``argparse.ArgumentParser`` instance used by the script.
 The ``script`` variable from the example above can be referenced in
 ``pyproject.toml`` to generate the script, like
 
+In order to serve metrics on the HTTPs endpoint both ``ssl-private-key`` and
+``ssl-public-key`` need to be define. The ssl certificate authority
+(i.e. ``ssl-ca``) is optional.
+
 .. code:: toml
 
     [project.scripts]

prometheus_aioexporter/script.py

@@ -3,6 +3,7 @@
 import argparse
 from collections.abc import Iterable
 import logging
+import ssl
 import sys
 from typing import IO
 
@@ -134,6 +135,21 @@ def get_parser(self) -> argparse.ArgumentParser:
             action="store_true",
             help="include process stats in metrics",
         )
+        parser.add_argument(
+            "--ssl-private-key",
+            type=argparse.FileType("r"),
+            help="full path to the ssl private key",
+        )
+        parser.add_argument(
+            "--ssl-public-key",
+            type=argparse.FileType("r"),
+            help="full path to the ssl public key",
+        )
+        parser.add_argument(
+            "--ssl-ca",
+            type=argparse.FileType("r"),
+            help="full path to the ssl certificate authority (CA)",
+        )
         self.configure_argument_parser(parser)
         return parser
 
@@ -164,6 +180,25 @@ def _configure_registry(self, include_process_stats: bool = False) -> None:
                 ProcessCollector(registry=None)
             )
 
+    def _get_ssl_context(
+        self, args: argparse.Namespace
+    ) -> ssl.SSLContext | None:
+        if args.ssl_private_key is None or args.ssl_public_key is None:
+            return None
+        cafile = None
+        if args.ssl_ca:
+            cafile = args.ssl_ca.name
+            args.ssl_ca.close()
+        ssl_context = ssl.create_default_context(
+            purpose=ssl.Purpose.CLIENT_AUTH, cafile=cafile
+        )
+        ssl_context.load_cert_chain(
+            args.ssl_public_key.name, args.ssl_private_key.name
+        )
+        args.ssl_public_key.close()
+        args.ssl_private_key.close()
+        return ssl_context
+
     def _get_exporter(self, args: argparse.Namespace) -> PrometheusExporter:
         """Return a :class:`PrometheusExporter` configured with args."""
         exporter = PrometheusExporter(
@@ -173,6 +208,7 @@ def _get_exporter(self, args: argparse.Namespace) -> PrometheusExporter:
             args.port,
             self.registry,
             metrics_path=args.metrics_path,
+            ssl_context=self._get_ssl_context(args),
         )
         exporter.app.on_startup.append(self.on_application_startup)
         exporter.app.on_shutdown.append(self.on_application_shutdown)

prometheus_aioexporter/web.py

@@ -5,6 +5,7 @@
     Callable,
     Iterable,
 )
+from ssl import SSLContext
 from textwrap import dedent
 
 from aiohttp.web import (
@@ -28,12 +29,13 @@ class PrometheusExporter:
     """Export Prometheus metrics via a web application."""
 
     name: str
-    descrption: str
+    description: str
     hosts: list[str]
     port: int
     register: MetricsRegistry
     app: Application
     metrics_path: str
+    ssl_context: SSLContext | None = None
 
     _update_handler: UpdateHandler | None = None
 
@@ -45,6 +47,7 @@ def __init__(
         port: int,
         registry: MetricsRegistry,
         metrics_path: str = "/metrics",
+        ssl_context: SSLContext | None = None,
     ) -> None:
         self.name = name
         self.description = description
@@ -53,6 +56,7 @@ def __init__(
         self.registry = registry
         self.metrics_path = metrics_path
         self.app = self._make_application()
+        self.ssl_context = ssl_context
 
     def set_metric_update_handler(self, handler: UpdateHandler) -> None:
         """Set a handler to update metrics.
@@ -74,6 +78,7 @@ def run(self) -> None:
             port=self.port,
             print=lambda *args, **kargs: None,
             access_log_format='%a "%r" %s %b "%{Referrer}i" "%{User-Agent}i"',
+            ssl_context=self.ssl_context,
         )
 
     def _make_application(self) -> Application:
@@ -90,7 +95,12 @@ async def _log_startup_message(self, app: Application) -> None:
         for host in self.hosts:
             if ":" in host:
                 host = f"[{host}]"
-            self.app.logger.info(f"Listening on http://{host}:{self.port}")
+            protocol = "http"
+            if self.ssl_context:
+                protocol = "https"
+            self.app.logger.info(
+                f"Listening on {protocol}://{host}:{self.port}"
+            )
 
     async def _handle_home(self, request: Request) -> Response:
         """Home page request handler."""

pyproject.toml

@@ -48,6 +48,7 @@ testing = [
   "pytest-aiohttp",
   "pytest-asyncio",
   "pytest-mock",
+  "trustme",
 ]
 [project.urls]
 changelog = "https://github.com/albertodonato/prometheus-aioexporter/blob/main/CHANGES.rst"

tests/conftest.py

@@ -0,0 +1,48 @@
+import ssl
+
+import pytest
+import trustme
+
+
+@pytest.fixture
+def ca():
+    yield trustme.CA()
+
+
+@pytest.fixture
+def tls_ca_path(ca):
+    with ca.cert_pem.tempfile() as ca_cert_pem:
+        yield ca_cert_pem
+
+
+@pytest.fixture
+def tls_certificate(ca):
+    yield ca.issue_cert("localhost", "127.0.0.1", "::1")
+
+
+@pytest.fixture
+def tls_public_key_path(tls_certificate):
+    """Provide a certificate chain PEM file path via fixture."""
+    with tls_certificate.private_key_and_cert_chain_pem.tempfile() as cert_pem:
+        yield cert_pem
+
+
+@pytest.fixture
+def tls_private_key_path(tls_certificate):
+    """Provide a certificate private key PEM file path via fixture."""
+    with tls_certificate.private_key_pem.tempfile() as cert_key_pem:
+        yield cert_key_pem
+
+
+@pytest.fixture
+def ssl_context(tls_certificate):
+    ssl_ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
+    tls_certificate.configure_cert(ssl_ctx)
+    yield ssl_ctx
+
+
+@pytest.fixture
+def ssl_context_server(tls_public_key_path, ca):
+    ssl_ctx = ssl.create_default_context(purpose=ssl.Purpose.SERVER_AUTH)
+    ca.configure_trust(ssl_ctx)
+    yield ssl_ctx