feat: Adds supports to generate a CA certificate

lib/charms/certificate_transfer_interface/v0/certificate_transfer.py

@@ -36,7 +36,7 @@ def _on_certificates_relation_joined(self, event: RelationJoinedEvent):
         certificate = "my certificate"
         ca = "my CA certificate"
         chain = ["certificate 1", "certificate 2"]
-        self.certificate_transfer.set_certificate(certificate=certificate, ca=ca, chain=chain)
+        self.certificate_transfer.set_certificate(certificate=certificate, ca=ca, chain=chain, relation_id=event.relation.id)
 
 
 if __name__ == "__main__":
@@ -54,6 +54,7 @@ def _on_certificates_relation_joined(self, event: RelationJoinedEvent):
 
 from lib.charms.certificate_transfer_interface.v0.certificate_transfer import (
     CertificateAvailableEvent,
+    CertificateRemovedEvent,
     CertificateTransferRequires,
 )
 
@@ -65,11 +66,18 @@ def __init__(self, *args):
         self.framework.observe(
             self.certificate_transfer.on.certificate_available, self._on_certificate_available
         )
+        self.framework.observe(
+            self.certificate_transfer.on.certificate_removed, self._on_certificate_removed
+        )
 
     def _on_certificate_available(self, event: CertificateAvailableEvent):
         print(event.certificate)
         print(event.ca)
         print(event.chain)
+        print(event.relation_id)
+
+    def _on_certificate_removed(self, event: CertificateRemovedEvent):
+        print(event.relation_id)
 
 
 if __name__ == "__main__":
@@ -87,10 +95,10 @@ def _on_certificate_available(self, event: CertificateAvailableEvent):
 
 import json
 import logging
-from typing import List, Optional
+from typing import List
 
-from jsonschema import exceptions, validate  # type: ignore[import]
-from ops.charm import CharmBase, CharmEvents, RelationChangedEvent
+from jsonschema import exceptions, validate  # type: ignore[import-untyped]
+from ops.charm import CharmBase, CharmEvents, RelationBrokenEvent, RelationChangedEvent
 from ops.framework import EventBase, EventSource, Handle, Object
 
 # The unique Charmhub library identifier, never change it
@@ -101,7 +109,7 @@ def _on_certificate_available(self, event: CertificateAvailableEvent):
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 1
+LIBPATCH = 5
 
 PYDEPS = ["jsonschema"]
 
@@ -161,25 +169,45 @@ def __init__(
         certificate: str,
         ca: str,
         chain: List[str],
+        relation_id: int,
     ):
         super().__init__(handle)
         self.certificate = certificate
         self.ca = ca
         self.chain = chain
+        self.relation_id = relation_id
 
     def snapshot(self) -> dict:
         """Return snapshot."""
         return {
             "certificate": self.certificate,
             "ca": self.ca,
             "chain": self.chain,
+            "relation_id": self.relation_id,
         }
 
     def restore(self, snapshot: dict):
         """Restores snapshot."""
         self.certificate = snapshot["certificate"]
         self.ca = snapshot["ca"]
         self.chain = snapshot["chain"]
+        self.relation_id = snapshot["relation_id"]
+
+
+class CertificateRemovedEvent(EventBase):
+    """Charm Event triggered when a TLS certificate is removed."""
+
+    def __init__(self, handle: Handle, relation_id: int):
+        super().__init__(handle)
+        self.relation_id = relation_id
+
+    def snapshot(self) -> dict:
+        """Return snapshot."""
+        return {"relation_id": self.relation_id}
+
+    def restore(self, snapshot: dict):
+        """Restores snapshot."""
+        self.relation_id = snapshot["relation_id"]
 
 
 def _load_relation_data(raw_relation_data: dict) -> dict:
@@ -204,6 +232,7 @@ class CertificateTransferRequirerCharmEvents(CharmEvents):
     """List of events that the Certificate Transfer requirer charm can leverage."""
 
     certificate_available = EventSource(CertificateAvailableEvent)
+    certificate_removed = EventSource(CertificateRemovedEvent)
 
 
 class CertificateTransferProvides(Object):
@@ -219,7 +248,7 @@ def set_certificate(
         certificate: str,
         ca: str,
         chain: List[str],
-        relation_id: Optional[int] = None,
+        relation_id: int,
     ) -> None:
         """Add certificates to relation data.
 
@@ -245,7 +274,7 @@ def set_certificate(
         relation.data[self.model.unit]["ca"] = ca
         relation.data[self.model.unit]["chain"] = json.dumps(chain)
 
-    def remove_certificate(self, relation_id: Optional[int] = None) -> None:
+    def remove_certificate(self, relation_id: int) -> None:
         """Remove a given certificate from relation data.
 
         Args:
@@ -303,6 +332,9 @@ def __init__(
         self.framework.observe(
             charm.on[relationship_name].relation_changed, self._on_relation_changed
         )
+        self.framework.observe(
+            charm.on[relationship_name].relation_broken, self._on_relation_broken
+        )
 
     @staticmethod
     def _relation_data_is_valid(relation_data: dict) -> bool:
@@ -343,4 +375,16 @@ def _on_relation_changed(self, event: RelationChangedEvent) -> None:
             certificate=remote_unit_relation_data.get("certificate"),
             ca=remote_unit_relation_data.get("ca"),
             chain=remote_unit_relation_data.get("chain"),
+            relation_id=event.relation.id,
         )
+
+    def _on_relation_broken(self, event: RelationBrokenEvent) -> None:
+        """Handler triggered on relation broken event.
+
+        Args:
+            event: Juju event
+
+        Returns:
+            None
+        """
+        self.on.certificate_removed.emit(relation_id=event.relation.id)

lib/charms/tls_certificates_interface/v2/tls_certificates.py

@@ -287,7 +287,7 @@ def _on_all_certificates_invalidated(self, event: AllCertificatesInvalidatedEven
 from cryptography.hazmat.primitives.asymmetric import rsa
 from cryptography.hazmat.primitives.serialization import pkcs12
 from cryptography.x509.extensions import Extension, ExtensionNotFound
-from jsonschema import exceptions, validate  # type: ignore[import]
+from jsonschema import exceptions, validate  # type: ignore[import-untyped]
 from ops.charm import (
     CharmBase,
     CharmEvents,
@@ -308,7 +308,7 @@ def _on_all_certificates_invalidated(self, event: AllCertificatesInvalidatedEven
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 16
+LIBPATCH = 19
 
 PYDEPS = ["cryptography", "jsonschema"]
 
@@ -335,7 +335,10 @@ def _on_all_certificates_invalidated(self, event: AllCertificatesInvalidatedEven
             "type": "array",
             "items": {
                 "type": "object",
-                "properties": {"certificate_signing_request": {"type": "string"}},
+                "properties": {
+                    "certificate_signing_request": {"type": "string"},
+                    "ca": {"type": "boolean"},
+                },
                 "required": ["certificate_signing_request"],
             },
         }
@@ -536,22 +539,31 @@ def restore(self, snapshot: dict):
 class CertificateCreationRequestEvent(EventBase):
     """Charm Event triggered when a TLS certificate is required."""
 
-    def __init__(self, handle: Handle, certificate_signing_request: str, relation_id: int):
+    def __init__(
+        self,
+        handle: Handle,
+        certificate_signing_request: str,
+        relation_id: int,
+        is_ca: bool = False,
+    ):
         super().__init__(handle)
         self.certificate_signing_request = certificate_signing_request
         self.relation_id = relation_id
+        self.is_ca = is_ca
 
     def snapshot(self) -> dict:
         """Returns snapshot."""
         return {
             "certificate_signing_request": self.certificate_signing_request,
             "relation_id": self.relation_id,
+            "is_ca": self.is_ca,
         }
 
     def restore(self, snapshot: dict):
         """Restores snapshot."""
         self.certificate_signing_request = snapshot["certificate_signing_request"]
         self.relation_id = snapshot["relation_id"]
+        self.is_ca = snapshot["is_ca"]
 
 
 class CertificateRevocationRequestEvent(EventBase):
@@ -685,6 +697,7 @@ def generate_certificate(
     ca_key_password: Optional[bytes] = None,
     validity: int = 365,
     alt_names: Optional[List[str]] = None,
+    is_ca: bool = False,
 ) -> bytes:
     """Generates a TLS certificate based on a CSR.
 
@@ -695,6 +708,7 @@ def generate_certificate(
         ca_key_password: CA private key password
         validity (int): Certificate validity (in days)
         alt_names (list): List of alt names to put on cert - prefer putting SANs in CSR
+        is_ca (bool): Whether the certificate is a CA certificate
 
     Returns:
         bytes: Certificate
@@ -726,7 +740,6 @@ def generate_certificate(
         .add_extension(
             x509.SubjectKeyIdentifier.from_public_key(csr_object.public_key()), critical=False
         )
-        .add_extension(x509.BasicConstraints(ca=False, path_length=None), critical=False)
     )
 
     extensions_list = csr_object.extensions
@@ -758,6 +771,29 @@ def generate_certificate(
             critical=extension.critical,
         )
 
+    if is_ca:
+        certificate_builder = certificate_builder.add_extension(
+            x509.BasicConstraints(ca=True, path_length=None), critical=True
+        )
+        certificate_builder = certificate_builder.add_extension(
+            x509.KeyUsage(
+                digital_signature=False,
+                content_commitment=False,
+                key_encipherment=False,
+                data_encipherment=False,
+                key_agreement=False,
+                key_cert_sign=True,
+                crl_sign=True,
+                encipher_only=False,
+                decipher_only=False,
+            ),
+            critical=True,
+        )
+    else:
+        certificate_builder = certificate_builder.add_extension(
+            x509.BasicConstraints(ca=False, path_length=None), critical=False
+        )
+
     certificate_builder._version = x509.Version.v3
     cert = certificate_builder.sign(private_key, hashes.SHA256())  # type: ignore[arg-type]
     return cert.public_bytes(serialization.Encoding.PEM)
@@ -1171,15 +1207,19 @@ def _on_relation_changed(self, event: RelationChangedEvent) -> None:
             certificate_creation_request["certificate_signing_request"]
             for certificate_creation_request in provider_certificates
         ]
-        requirer_unit_csrs = [
-            certificate_creation_request["certificate_signing_request"]
+        requirer_unit_certificate_requests = [
+            {
+                "csr": certificate_creation_request["certificate_signing_request"],
+                "is_ca": certificate_creation_request.get("ca", False),
+            }
             for certificate_creation_request in requirer_csrs
         ]
-        for certificate_signing_request in requirer_unit_csrs:
-            if certificate_signing_request not in provider_csrs:
+        for certificate_request in requirer_unit_certificate_requests:
+            if certificate_request["csr"] not in provider_csrs:
                 self.on.certificate_creation_request.emit(
-                    certificate_signing_request=certificate_signing_request,
+                    certificate_signing_request=certificate_request["csr"],
                     relation_id=event.relation.id,
+                    is_ca=certificate_request["is_ca"],
                 )
         self._revoke_certificates_for_which_no_csr_exists(relation_id=event.relation.id)
 
@@ -1337,8 +1377,17 @@ def __init__(
             self.framework.observe(charm.on.update_status, self._on_update_status)
 
     @property
-    def _requirer_csrs(self) -> List[Dict[str, str]]:
-        """Returns list of requirer's CSRs from relation data."""
+    def _requirer_csrs(self) -> List[Dict[str, Union[bool, str]]]:
+        """Returns list of requirer's CSRs from relation data.
+
+        Example:
+            [
+                {
+                    "certificate_signing_request": "-----BEGIN CERTIFICATE REQUEST-----...",
+                    "ca": false
+                }
+            ]
+        """
         relation = self.model.get_relation(self.relationship_name)
         if not relation:
             raise RuntimeError(f"Relation {self.relationship_name} does not exist")
@@ -1361,11 +1410,12 @@ def _provider_certificates(self) -> List[Dict[str, str]]:
             return []
         return provider_relation_data.get("certificates", [])
 
-    def _add_requirer_csr(self, csr: str) -> None:
+    def _add_requirer_csr(self, csr: str, is_ca: bool) -> None:
         """Adds CSR to relation data.
 
         Args:
             csr (str): Certificate Signing Request
+            is_ca (bool): Whether the certificate is a CA certificate
 
         Returns:
             None
@@ -1376,7 +1426,10 @@ def _add_requirer_csr(self, csr: str) -> None:
                 f"Relation {self.relationship_name} does not exist - "
                 f"The certificate request can't be completed"
             )
-        new_csr_dict = {"certificate_signing_request": csr}
+        new_csr_dict: Dict[str, Union[bool, str]] = {
+            "certificate_signing_request": csr,
+            "ca": is_ca,
+        }
         if new_csr_dict in self._requirer_csrs:
             logger.info("CSR already in relation data - Doing nothing")
             return
@@ -1400,18 +1453,22 @@ def _remove_requirer_csr(self, csr: str) -> None:
                 f"The certificate request can't be completed"
             )
         requirer_csrs = copy.deepcopy(self._requirer_csrs)
-        csr_dict = {"certificate_signing_request": csr}
-        if csr_dict not in requirer_csrs:
-            logger.info("CSR not in relation data - Doing nothing")
+        if not requirer_csrs:
+            logger.info("No CSRs in relation data - Doing nothing")
             return
-        requirer_csrs.remove(csr_dict)
+        for requirer_csr in requirer_csrs:
+            if requirer_csr["certificate_signing_request"] == csr:
+                requirer_csrs.remove(requirer_csr)
         relation.data[self.model.unit]["certificate_signing_requests"] = json.dumps(requirer_csrs)
 
-    def request_certificate_creation(self, certificate_signing_request: bytes) -> None:
+    def request_certificate_creation(
+        self, certificate_signing_request: bytes, is_ca: bool = False
+    ) -> None:
         """Request TLS certificate to provider charm.
 
         Args:
             certificate_signing_request (bytes): Certificate Signing Request
+            is_ca (bool): Whether the certificate is a CA certificate
 
         Returns:
             None
@@ -1422,7 +1479,7 @@ def request_certificate_creation(self, certificate_signing_request: bytes) -> No
                 f"Relation {self.relationship_name} does not exist - "
                 f"The certificate request can't be completed"
             )
-        self._add_requirer_csr(certificate_signing_request.decode().strip())
+        self._add_requirer_csr(certificate_signing_request.decode().strip(), is_ca=is_ca)
         logger.info("Certificate request sent to provider")
 
     def request_certificate_revocation(self, certificate_signing_request: bytes) -> None:
@@ -1701,7 +1758,10 @@ def csr_matches_certificate(csr: str, cert: str) -> bool:
             format=serialization.PublicFormat.SubjectPublicKeyInfo,
         ):
             return False
-        if csr_object.subject != cert_object.subject:
+        if (
+            csr_object.public_key().public_numbers().n  # type: ignore[union-attr]
+            != cert_object.public_key().public_numbers().n  # type: ignore[union-attr]
+        ):
             return False
     except ValueError:
         logger.warning("Could not load certificate or CSR.")