fix: expand home paths for mtls auth (#72)

Amp-Thread-ID: https://ampcode.com/threads/T-019e76ce-9495-77e0-9e92-c0b6365d47f7

Co-authored-by: Amp <amp@ampcode.com>

Author: alDuncanson

src/a2a_handler/auth.py

@@ -250,6 +250,10 @@ def create_mtls_auth(
     ca_cert_path: str | None = None,
 ) -> AuthCredentials:
     """Create mTLS (mutual TLS) client certificate authentication."""
+    cert_path = str(Path(cert_path).expanduser())
+    key_path = str(Path(key_path).expanduser())
+    ca_cert_path = str(Path(ca_cert_path).expanduser()) if ca_cert_path else None
+
     if not Path(cert_path).is_file():
         raise FileNotFoundError(f"Client certificate not found: {cert_path}")
     if not Path(key_path).is_file():

tests/auth/test_auth.py

@@ -1,6 +1,7 @@
 """Tests for authentication module."""
 
 import tempfile
+from pathlib import Path
 from unittest.mock import AsyncMock
 
 import pytest
@@ -166,6 +167,29 @@ def test_create_mtls_auth_with_ca_cert(self) -> None:
             creds = create_mtls_auth(cert_file.name, key_file.name, ca_file.name)
             assert creds.ca_cert_path == ca_file.name
 
+    def test_create_mtls_auth_expands_home_directory_paths(
+        self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        home = tmp_path / "home"
+        home.mkdir()
+        cert_path = home / "client.pem"
+        key_path = home / "client.key"
+        ca_cert_path = home / "ca.pem"
+        cert_path.write_text("cert")
+        key_path.write_text("key")
+        ca_cert_path.write_text("ca")
+
+        import os
+
+        os.chmod(key_path, 0o600)
+        monkeypatch.setenv("HOME", str(home))
+
+        creds = create_mtls_auth("~/client.pem", "~/client.key", "~/ca.pem")
+
+        assert creds.cert_path == str(cert_path)
+        assert creds.key_path == str(key_path)
+        assert creds.ca_cert_path == str(ca_cert_path)
+
     def test_create_mtls_auth_rejects_insecure_key_permissions(self) -> None:
         with tempfile.NamedTemporaryFile(suffix=".pem", delete=False) as cert_file:
             cert_path = cert_file.name