Add type hints

.github/workflows/ci.yml

@@ -39,7 +39,6 @@ jobs:
     strategy:
       matrix:
         python-version:
-          - "3.7"
           - "3.8"
           - "3.9"
           - "3.10"
@@ -56,7 +55,7 @@ jobs:
           allow-prereleases: true
           cache: pip
 
-      - name: Install & run tox
+      - name: Prepare tox
         run: |
           V=${{ matrix.python-version }}
 
@@ -67,7 +66,9 @@ jobs:
           fi
 
           python -Im pip install tox
-          python -Im tox run -f "$V"
+
+      - run: python -Im tox run -f "$V"
+      - run: python -Im tox run -e mypy
 
       - name: Upload coverage data
         uses: actions/upload-artifact@v3

CHANGELOG.md

@@ -14,7 +14,7 @@ If breaking changes are needed do be done, they are:
 
 ### Backwards-incompatible Changes
 
-- All Python versions up to and including 3.6 have been dropped.
+- All Python versions up to and including 3.7 have been dropped.
 - Support for `commonName` in certificates has been dropped.
   It has been deprecated since 2017 and isn't supported by any major browser.
 - The oldest supported pyOpenSSL version (when using the `pyopenssl` backend) is now 17.0.0.
@@ -33,6 +33,8 @@ If breaking changes are needed do be done, they are:
 - `service_identity.(cryptography|pyopenssl).extract_patterns()` are now public APIs (FKA `extract_ids()`).
   You can use them to extract the patterns from a certificate without verifying anything.
   [#55](https://github.com/pyca/service-identity/pull/55)
+- *service-identity* is now fully typed.
+  [#57](https://github.com/pyca/service-identity/pull/57)
 
 
 ## 21.1.0 (2021-05-09)

docs/pyopenssl_example.py

@@ -12,7 +12,7 @@
 hostname = sys.argv[1]
 
 ctx = SSL.Context(SSL.TLSv1_2_METHOD)
-ctx.set_verify(SSL.VERIFY_PEER, lambda conn, cert, errno, depth, ok: ok)
+ctx.set_verify(SSL.VERIFY_PEER, lambda conn, cert, errno, depth, ok: bool(ok))
 ctx.set_default_verify_paths()
 
 conn = SSL.Connection(ctx, socket.socket(socket.AF_INET, socket.SOCK_STREAM))
@@ -22,12 +22,9 @@
 try:
     conn.do_handshake()
 
-    print("Server certificate is valid for the following patterns:\n")
-    pprint.pprint(
-        service_identity.pyopenssl.extract_patterns(
-            conn.get_peer_certificate()
-        )
-    )
+    if cert := conn.get_peer_certificate():
+        print("Server certificate is valid for the following patterns:\n")
+        pprint.pprint(service_identity.pyopenssl.extract_patterns(cert))
 
     try:
         service_identity.pyopenssl.verify_hostname(conn, hostname)

pyproject.toml

@@ -6,14 +6,13 @@ build-backend = "hatchling.build"
 name = "service-identity"
 authors = [{ name = "Hynek Schlawack", email = "hs@ox.cx" }]
 license = "MIT"
-requires-python = ">=3.7"
+requires-python = ">=3.8"
 description = "Service identity verification for pyOpenSSL & cryptography."
 keywords = ["cryptography", "openssl", "pyopenssl"]
 classifiers = [
     "Development Status :: 5 - Production/Stable",
     "License :: OSI Approved :: MIT License",
     "Operating System :: OS Independent",
-    "Programming Language :: Python :: 3.7",
     "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
@@ -23,22 +22,23 @@ classifiers = [
     "Programming Language :: Python :: Implementation :: PyPy",
     "Topic :: Security :: Cryptography",
     "Topic :: Software Development :: Libraries :: Python Modules",
+    "Typing :: Typed",
 ]
 dependencies = [
     # Keep in-sync with tests/constraints/*.
     "attrs>=19.1.0",
     "pyasn1-modules",
     "pyasn1",
     "cryptography",
-    "importlib_metadata;python_version<'3.8'",
 ]
 dynamic = ["version", "readme"]
 
 [project.optional-dependencies]
 idna = ["idna"]
 tests = ["coverage[toml]>=5.0.2", "pytest"]
 docs = ["sphinx", "furo", "myst-parser", "sphinx-notfound-page"]
-dev = ["service-identity[tests,docs,idna]", "pyOpenSSL"]
+mypy = ["mypy", "types-pyOpenSSL", "idna"]
+dev = ["service-identity[tests,mypy,docs,idna]", "pyOpenSSL"]
 
 [project.urls]
 Documentation = "https://service-identity.readthedocs.io/"
@@ -105,6 +105,22 @@ source = ["src", ".tox/py*/**/site-packages"]
 [tool.coverage.report]
 show_missing = true
 skip_covered = true
+exclude_lines = [
+    # a more strict default pragma
+    "\\# pragma: no cover\\b",
+
+    # allow defensive code
+    "^\\s*raise AssertionError\\b",
+    "^\\s*raise NotImplementedError\\b",
+    "^\\s*return NotImplemented\\b",
+    "^\\s*raise$",
+
+    # typing-related code
+    "^if (False|TYPE_CHECKING):",
+    ": \\.\\.\\.(\\s*#.*)?$",
+    "^ +\\.\\.\\.$",
+    "-> ['\"]?NoReturn['\"]?:",
+]
 
 
 [tool.black]
@@ -152,3 +168,25 @@ ignore = [
 [tool.ruff.isort]
 lines-between-types = 1
 lines-after-imports = 2
+
+
+[tool.mypy]
+strict = true
+
+show_error_codes = true
+enable_error_code = ["ignore-without-code"]
+ignore_missing_imports = true
+
+warn_return_any = false
+
+[[tool.mypy.overrides]]
+module = "tests.*"
+ignore_errors = true
+
+[[tool.mypy.overrides]]
+module = "tests.typing.*"
+ignore_errors = false
+
+[[tool.mypy.overrides]]
+module = "cryptography.*"
+follow_imports = "skip"

src/service_identity/__init__.py

@@ -40,13 +40,9 @@ def __getattr__(name: str) -> str:
     if name not in dunder_to_metadata.keys():
         raise AttributeError(f"module {__name__} has no attribute {name}")
 
-    import sys
     import warnings
 
-    if sys.version_info < (3, 8):
-        from importlib_metadata import metadata
-    else:
-        from importlib.metadata import metadata
+    from importlib.metadata import metadata
 
     warnings.warn(
         f"Accessing service_identity.{name} is deprecated and will be "

src/service_identity/cryptography.py

@@ -59,7 +59,7 @@ def verify_certificate_hostname(
     """
     verify_service_identity(
         cert_patterns=extract_patterns(certificate),
-        obligatory_ids=[DNS_ID(hostname)],
+        obligatory_ids=[DNS_ID(hostname)],  # type: ignore[list-item]
         optional_ids=[],
     )
 
@@ -89,7 +89,7 @@ def verify_certificate_ip_address(
     """
     verify_service_identity(
         cert_patterns=extract_patterns(certificate),
-        obligatory_ids=[IPAddress_ID(ip_address)],
+        obligatory_ids=[IPAddress_ID(ip_address)],  # type: ignore[list-item]
         optional_ids=[],
     )
 
@@ -141,7 +141,7 @@ def extract_patterns(cert: Certificate) -> Sequence[CertificatePattern]:
                 srv, _ = decode(other.value)
                 if isinstance(srv, IA5String):
                     ids.append(SRVPattern.from_bytes(srv.asOctets()))
-                else:  # pragma: nocover
+                else:  # pragma: no cover
                     raise CertificateError("Unexpected certificate content.")
 
     return ids

src/service_identity/exceptions.py

@@ -5,6 +5,13 @@
 them from __init__.py.
 """
 
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Sequence
+
+
+if TYPE_CHECKING:
+    from .hazmat import ServiceID
 
 import attr
 
@@ -23,52 +30,45 @@ class SubjectAltNameWarning(DeprecationWarning):
     """
 
 
-@attr.s(auto_exc=True)
-class VerificationError(Exception):
-    """
-    Service identity verification failed.
-    """
-
-    errors = attr.ib()
-
-    def __str__(self):
-        return self.__repr__()
+@attr.s(slots=True)
+class Mismatch:
+    mismatched_id: ServiceID = attr.ib()
 
 
-@attr.s
-class DNSMismatch:
+class DNSMismatch(Mismatch):
     """
     No matching DNSPattern could be found.
     """
 
-    mismatched_id = attr.ib()
-
 
-@attr.s
-class SRVMismatch:
+class SRVMismatch(Mismatch):
     """
     No matching SRVPattern could be found.
     """
 
-    mismatched_id = attr.ib()
 
-
-@attr.s
-class URIMismatch:
+class URIMismatch(Mismatch):
     """
     No matching URIPattern could be found.
     """
 
-    mismatched_id = attr.ib()
-
 
-@attr.s
-class IPAddressMismatch:
+class IPAddressMismatch(Mismatch):
     """
     No matching IPAddressPattern could be found.
     """
 
-    mismatched_id = attr.ib()
+
+@attr.s(auto_exc=True)
+class VerificationError(Exception):
+    """
+    Service identity verification failed.
+    """
+
+    errors: Sequence[Mismatch] = attr.ib()
+
+    def __str__(self) -> str:
+        return self.__repr__()
 
 
 class CertificateError(Exception):