Pin S3 and SMB connector peers

src/govoplan_files/backend/manifest.py

@@ -359,6 +359,23 @@ manifest = ModuleManifest(
             audience=("file_user", "file_manager", "administrator"),
             related_modules=("search",),
             order=41,
+            conditions=(
+                DocumentationCondition(
+                    required_modules=("files",),
+                    any_scopes=("files:file:read", "files:file:admin"),
+                ),
+            ),
+            links=(
+                DocumentationLink(label="Files", href="/files", kind="runtime"),
+                DocumentationLink(label="Search", href="/search", kind="runtime"),
+                DocumentationLink(label="Files handbook", href="govoplan-files/docs/FILES_HANDBOOK.md", kind="repository"),
+            ),
+            metadata={
+                "kind": "reference",
+                "route": "/files",
+                "screen": "Files search contribution",
+                "help_contexts": ["files.list"],
+            },
         ),
         DocumentationTopic(
             id="files.workflow.organize-managed-files",
@@ -618,10 +635,10 @@ manifest = ModuleManifest(
         DocumentationTopic(
             id="files.reference.integrity-recovery-and-fail-closed-transports",
             title="Operate Files integrity, recovery, and connector transport safety",
-            summary="Back up database evidence, blob ciphertext, and Encryption custody as one recovery unit, and keep unsupported SDK transports fail-closed.",
+            summary="Back up database evidence, blob ciphertext, and Encryption custody as one recovery unit, and pin every SDK-managed connector peer.",
             body=(
                 "Local durable storage is the operational baseline. Recover Files from a coordinated database/blob snapshot with the matching Encryption tables and original deployment master key, then run the bounded resumable integrity scan from Administration and verify representative protected and unprotected access paths. Each scan batch and finding action requires the revision shown to the operator, so a stale screen cannot recheck or delete after concurrent reconciliation. Protected scans verify stored ciphertext before decryption and then verify plaintext semantic evidence. Managed blob creation/repair and applied orphan cleanup commit lease-fenced Core recovery intent before object effects; success, compensation, and forward completion require independent database and object checks, while mismatch is quarantined and unresolved work remains visible in Ops. Missing or mismatched blobs are quarantined; orphan objects are reported before dry-run-first, explicitly authorized cleanup. "
-                "Arbitrary external S3 managed storage/connectors and SMB connectors fail closed until botocore redirects/endpoint discovery and SMB initial connections/DFS referrals support connection-time DNS/IP pinning. Installer-owned Garage storage is supported only at the exact deployment service endpoint with its explicit trust marker. Destructive module retirement drops database tables but does not remove backend blob objects."
+                "S3 connector pools pin every retry, redirect, discovered endpoint, and provider alias while retaining the configured TLS authority; outbound proxies and ambient credential discovery are disabled. SMB initial connections, reconnects, aliases, and DFS referrals use a Files-owned pinned transport and cache. Both apply the deployment private-network policy immediately before each socket opens and fail closed if an SDK no longer exposes the verified transport seam. Installer-owned Garage storage is supported only at the exact deployment service endpoint with its explicit trust marker. Destructive module retirement drops database tables but does not remove backend blob objects."
             ),
             layer="configured",
             documentation_types=("admin",),
@@ -669,7 +686,7 @@ manifest = ModuleManifest(
                 "screen": "System file connections and deployment operations",
                 "section": "Storage integrity, backup/recovery, and fail-closed transports",
                 "recovery_unit": ["Files database rows", "Encryption envelope and wrapped-key rows", "managed blob namespace", "MASTER_KEY_B64", "deployment-owned connector configuration"],
-                "verification": "After restore, complete a checksum-enabled integrity scan, resolve every missing/corrupt finding, approve or retain every reported orphan, inspect Files recovery operations in Ops, verify authorized and denied access, and test one permitted pinned HTTP connector.",
+                "verification": "After restore, complete a checksum-enabled integrity scan, resolve every missing/corrupt finding, approve or retain every reported orphan, inspect Files recovery operations in Ops, verify authorized and denied access, and test configured pinned HTTP, S3, and SMB connectors against their recorded target topology.",
                 "related_topic_ids": [
                     "files.governed-connectors-and-provenance",
                     "files.reference.snapshot-provenance-and-capabilities",
@@ -774,7 +791,7 @@ manifest = ModuleManifest(
                     "Confirm version alignment, apply migrations on clean and upgrade databases, and run the repository plus meta-repository security and static-analysis gates.",
                     "Exercise allowed and denied personal, group, and share access with representative accounts.",
                     "Exercise bounded archive preview and confirmation, every required conflict strategy, organization, download, and soft deletion.",
-                    "Where connectors are configured, verify policy explanation and one pinned HTTP provider; verify installer-owned Garage when selected, and verify arbitrary external S3 and SMB access still fails closed.",
+                    "Where connectors are configured, verify policy explanation and one pinned HTTP provider; verify installer-owned Garage when selected, then exercise configured S3 retries/aliases and SMB reconnect/referral targets under the deployment private-network policy, confirming an incompatible SDK transport seam fails closed.",
                     "Restore a coordinated database/blob/key backup and compare representative downloaded bytes with their recorded SHA-256 checksums.",
                     "Record the tested versions, results, known limitations, evidence locations, residual risks, owner, and approval decision.",
                 ],

src/govoplan_files/backend/storage/connector_browse.py

@@ -15,8 +15,8 @@ from defusedxml import ElementTree as SafeElementTree
 
 from govoplan_core.security.outbound_http import (
     OutboundHttpError,
-    validate_unpinned_sdk_host,
-    validate_unpinned_sdk_http_url,
+    validate_outbound_host,
+    validate_outbound_http_url,
 )
 
 from govoplan_files.backend.storage.http_client import ConnectorHttpError, request_connector_bytes
@@ -27,6 +27,12 @@ from govoplan_files.backend.storage.connector_deployment import (
     validate_connector_tls_metadata,
 )
 from govoplan_files.backend.storage.connector_profiles import ConnectorProfile
+from govoplan_files.backend.storage.sdk_peer_pinning import (
+    SdkPeerPinningError,
+    create_pinned_s3_client,
+    install_pinned_smb_transport,
+    pinned_smb_connection_cache,
+)
 
 
 class ConnectorBrowseError(RuntimeError):
@@ -246,6 +252,28 @@ def _browse_smb(profile: ConnectorProfile, *, path: str) -> list[ConnectorBrowse
 
 def _browse_s3(profile: ConnectorProfile, *, path: str, library_id: str | None, continuation_token: str | None) -> list[ConnectorBrowseItem]:
     client = _s3_client(profile)
+    try:
+        return _browse_s3_with_client(
+            client,
+            profile=profile,
+            path=path,
+            library_id=library_id,
+            continuation_token=continuation_token,
+        )
+    finally:
+        close = getattr(client, "close", None)
+        if callable(close):
+            close()
+
+
+def _browse_s3_with_client(
+    client: Any,
+    *,
+    profile: ConnectorProfile,
+    path: str,
+    library_id: str | None,
+    continuation_token: str | None,
+) -> list[ConnectorBrowseItem]:
     bucket = _s3_bucket(profile, library_id)
     if not bucket:
         try:
@@ -313,23 +341,22 @@ def _s3_client(profile: ConnectorProfile) -> Any:
         raise ConnectorBrowseError("Secret-ref S3 credentials need a runtime secret resolver before live browsing")
     if profile.endpoint_url:
         try:
-            endpoint_url = validate_unpinned_sdk_http_url(
+            endpoint_url = validate_outbound_http_url(
                 profile.endpoint_url,
                 label="S3 connector endpoint",
             )
         except OutboundHttpError as exc:
             raise ConnectorBrowseError(str(exc)) from exc
     else:
-        raise ConnectorBrowseError(
-            "S3 connector endpoint discovery uses an SDK transport that cannot guarantee connection-time DNS/IP "
-            "pinning; live S3 access is disabled until that transport supports pinning"
-        )
+        endpoint_url = None
     try:
-        boto3 = import_module("boto3")
         config_module = import_module("botocore.config")
+        unsigned = import_module("botocore").UNSIGNED
     except ImportError as exc:
         raise ConnectorBrowseUnsupported("S3 connector browsing requires the optional boto3 dependency") from exc
-    kwargs: dict[str, object] = {"endpoint_url": endpoint_url}
+    kwargs: dict[str, object] = {}
+    if endpoint_url:
+        kwargs["endpoint_url"] = endpoint_url
     region = _metadata_string(profile, "region") or _metadata_string(profile, "aws_region")
     if region:
         kwargs["region_name"] = region
@@ -346,10 +373,21 @@ def _s3_client(profile: ConnectorProfile) -> Any:
     if verify is not None:
         kwargs["verify"] = verify
     addressing_style = _s3_addressing_style(profile)
+    config_values: dict[str, object] = {
+        "proxies": {},
+        "retries": {"mode": "standard", "max_attempts": 4},
+    }
     if addressing_style:
-        kwargs["config"] = config_module.Config(s3={"addressing_style": addressing_style})
+        config_values["s3"] = {"addressing_style": addressing_style}
+    if bool(access_key) != bool(secret_key):
+        raise ConnectorBrowseError("S3 connectors require both an access key and a secret key")
+    if not access_key:
+        config_values["signature_version"] = unsigned
+    kwargs["config"] = config_module.Config(**config_values)
     try:
-        return boto3.client("s3", **kwargs)
+        return create_pinned_s3_client(**kwargs)
+    except SdkPeerPinningError as exc:
+        raise ConnectorBrowseError(str(exc)) from exc
     except Exception as exc:  # pragma: no cover - concrete exception types are dependency-version specific
         raise ConnectorBrowseError(f"S3 connector could not be initialized: {exc}") from exc
 
@@ -783,7 +821,7 @@ def _smb_location(profile: ConnectorProfile) -> _SmbLocation:
         raise ConnectorBrowseError("SMB connector endpoint_url must include a server")
     port = parsed.port or _int(profile.metadata.get("port")) or 445
     try:
-        validate_unpinned_sdk_host(server, port=port, label="SMB connector endpoint")
+        validate_outbound_host(server, port=port, label="SMB connector endpoint")
     except OutboundHttpError as exc:
         raise ConnectorBrowseError(str(exc)) from exc
     path_parts = [part for part in unquote(parsed.path or "").strip("/").split("/") if part]
@@ -810,6 +848,7 @@ def _smb_unc_path(location: _SmbLocation, path: str) -> str:
 def _smb_client_kwargs(profile: ConnectorProfile, location: _SmbLocation) -> dict[str, object]:
     kwargs: dict[str, object] = {
         "port": location.port,
+        "connection_cache": pinned_smb_connection_cache(),
         "require_signing": _metadata_bool(profile, "require_signing", default=True),
         "auth_protocol": _metadata_string(profile, "auth_protocol") or "ntlm",
     }
@@ -845,9 +884,11 @@ def _profile_token(profile: ConnectorProfile) -> str | None:
 
 def _smbclient_module() -> Any:
     try:
-        return import_module("smbclient")
+        return install_pinned_smb_transport(import_module("smbclient"))
     except ImportError as exc:
         raise ConnectorBrowseUnsupported("SMB connector browsing requires the optional smbprotocol dependency") from exc
+    except SdkPeerPinningError as exc:
+        raise ConnectorBrowseUnsupported(str(exc)) from exc
 
 
 def _smb_entry_stat(entry: object) -> object | None:

src/govoplan_files/backend/storage/connector_imports.py

@@ -314,15 +314,20 @@ def _read_s3_file(profile: ConnectorProfile, *, library_id: str, path: str, max_
     if not key:
         raise ConnectorImportError("S3 import requires an object key")
     client = _s3_import_client(profile)
-    detail = _s3_object_detail(client, bucket=bucket, key=key, max_bytes=max_bytes)
-    version_id = _clean(detail.get("VersionId"))
-    response, data = _download_s3_object(
-        client,
-        bucket=bucket,
-        key=key,
-        version_id=version_id,
-        max_bytes=max_bytes,
-    )
+    try:
+        detail = _s3_object_detail(client, bucket=bucket, key=key, max_bytes=max_bytes)
+        version_id = _clean(detail.get("VersionId"))
+        response, data = _download_s3_object(
+            client,
+            bucket=bucket,
+            key=key,
+            version_id=version_id,
+            max_bytes=max_bytes,
+        )
+    finally:
+        close = getattr(client, "close", None)
+        if callable(close):
+            close()
     content_type = _clean(response.get("ContentType") if isinstance(response, dict) else None) or _clean(detail.get("ContentType")) or mimetypes.guess_type(key)[0]
     etag = _clean(response.get("ETag") if isinstance(response, dict) else None) or _clean(detail.get("ETag"))
     filename = filename_from_path(key)

src/govoplan_files/backend/storage/connector_providers.py

@@ -110,7 +110,7 @@ def connector_provider_descriptors() -> tuple[ConnectorProviderDescriptor, ...]:
             conflict_strategy="Managed import/sync uses existing files conflict_strategy handling after download.",
             preview_strategy="Previews are generated from the frozen managed file after import or sync, not directly from the share.",
             audit_events=("files.connector.imported", "files.connector.synced", "files.connector.accessed"),
-            notes="Browse/import logic is implemented, but live smbprotocol access fails closed until the SDK supports connection-time DNS/IP pinning for initial connections and DFS referrals.",
+            notes="Initial sessions, reconnects, aliases, and DFS referral targets use the Files-owned pinned smbprotocol transport and the deployment-wide private-network policy.",
         ),
         ConnectorProviderDescriptor(
             provider="s3",
@@ -125,7 +125,7 @@ def connector_provider_descriptors() -> tuple[ConnectorProviderDescriptor, ...]:
             conflict_strategy="Managed import/sync uses existing files conflict_strategy handling after object download.",
             preview_strategy="Previews are generated from the frozen managed file after import or sync, not directly from the bucket.",
             audit_events=("files.connector.imported", "files.connector.synced", "files.connector.accessed"),
-            notes="Browse/import logic is implemented, but live boto3 access fails closed until its HTTP transport supports connection-time DNS/IP pinning and redirect revalidation.",
+            notes="Every botocore connection pool uses the Files-owned pinned transport, including retries, redirects, endpoint discovery, and virtual-host aliases; outbound proxies and ambient credential discovery are disabled.",
         ),
         ConnectorProviderDescriptor(
             provider="sharepoint",

src/govoplan_files/backend/storage/connector_visibility.py

@@ -136,11 +136,6 @@ def connector_profile_usable_for_import(profile: ConnectorProfile) -> bool:
         and descriptor.import_supported
     ):
         return False
-    # These SDK paths intentionally fail closed until every connection peer and
-    # SDK-managed redirect/referral can be pinned and revalidated.
-    if profile.provider in {"s3", "smb"}:
-        return False
-
     # Prove that the initial root browse performed by the current Files UI is
     # policy-allowed. A later selected remote path/item is checked again.
     return connector_policy_decision(

src/govoplan_files/backend/storage/sdk_peer_pinning.py

@@ -0,0 +1,331 @@
+from __future__ import annotations
+
+import inspect
+import socket
+import threading
+from functools import lru_cache
+from importlib import import_module
+from typing import Any
+
+from govoplan_core.security.outbound_http import (
+    OutboundHttpError,
+    create_outbound_connection,
+)
+
+
+class SdkPeerPinningError(RuntimeError):
+    """Raised when an optional SDK cannot be bound to the pinned transport."""
+
+
+_BOTOCORE_CLIENT_CREATION_LOCK = threading.Lock()
+
+
+def create_pinned_s3_client(**kwargs: Any) -> Any:
+    """Construct an S3 client whose first and every later socket is pinned.
+
+    Botocore does not expose the HTTP-session class through boto3's public
+    client API. Its endpoint creator does expose that seam, so this function
+    replaces the creator only for the bounded client-construction operation.
+    The lock avoids an unsafe interleaving with another GovOPlaN client
+    construction. Any unrelated botocore client created during the short
+    replacement window also receives the stricter transport.
+    """
+
+    try:
+        boto3 = import_module("boto3")
+        botocore_args = import_module("botocore.args")
+    except ImportError as exc:
+        raise SdkPeerPinningError(
+            "S3 connector browsing requires the optional boto3 dependency"
+        ) from exc
+
+    pinned_session_cls = _botocore_transport_types()[0]
+    original_creator = getattr(botocore_args, "EndpointCreator", None)
+    if original_creator is None or not hasattr(original_creator, "create_endpoint"):
+        raise SdkPeerPinningError(
+            "The installed botocore release does not expose the endpoint transport seam required for peer pinning"
+        )
+
+    class PinnedEndpointCreator(original_creator):  # type: ignore[misc, valid-type]
+        def create_endpoint(self, *args: Any, **endpoint_kwargs: Any) -> Any:
+            endpoint_kwargs["http_session_cls"] = pinned_session_cls
+            return super().create_endpoint(*args, **endpoint_kwargs)
+
+    with _BOTOCORE_CLIENT_CREATION_LOCK:
+        current_creator = getattr(botocore_args, "EndpointCreator", None)
+        if current_creator is not original_creator:
+            raise SdkPeerPinningError(
+                "Botocore endpoint construction changed concurrently; refusing to create an unproven S3 client"
+            )
+        botocore_args.EndpointCreator = PinnedEndpointCreator
+        try:
+            session_type = getattr(getattr(boto3, "session", None), "Session", None)
+            if session_type is None:
+                raise SdkPeerPinningError(
+                    "The installed boto3 release does not expose its isolated session constructor"
+                )
+            client = session_type().client("s3", **kwargs)
+        finally:
+            if getattr(botocore_args, "EndpointCreator", None) is PinnedEndpointCreator:
+                botocore_args.EndpointCreator = original_creator
+
+    http_session = getattr(getattr(client, "_endpoint", None), "http_session", None)
+    if http_session is None or not isinstance(http_session, pinned_session_cls):
+        close = getattr(client, "close", None)
+        if callable(close):
+            close()
+        raise SdkPeerPinningError(
+            "Botocore did not install the required pinned HTTP transport; the S3 client was discarded"
+        )
+    return client
+
+
+@lru_cache(maxsize=1)
+def _botocore_transport_types() -> tuple[type[Any], type[Any], type[Any]]:
+    try:
+        awsrequest = import_module("botocore.awsrequest")
+        httpsession = import_module("botocore.httpsession")
+        urllib3_exceptions = import_module("urllib3.exceptions")
+    except ImportError as exc:
+        raise SdkPeerPinningError(
+            "S3 connector browsing requires a compatible botocore HTTP transport"
+        ) from exc
+
+    required = (
+        "AWSHTTPConnection",
+        "AWSHTTPSConnection",
+        "AWSHTTPConnectionPool",
+        "AWSHTTPSConnectionPool",
+    )
+    if any(not hasattr(awsrequest, name) for name in required) or not hasattr(
+        httpsession, "URLLib3Session"
+    ):
+        raise SdkPeerPinningError(
+            "The installed botocore release is missing the connection classes required for peer pinning"
+        )
+
+    def pinned_new_connection(connection: Any) -> socket.socket:
+        hostname = str(getattr(connection, "_dns_host", "") or "").strip()
+        port = int(getattr(connection, "port", 0) or 0)
+        if not hostname or not port:
+            raise urllib3_exceptions.NewConnectionError(
+                connection, "Pinned S3 connection is missing its target authority"
+            )
+        try:
+            return create_outbound_connection(
+                hostname,
+                port,
+                timeout=getattr(connection, "timeout", None),
+                source_address=getattr(connection, "source_address", None),
+                socket_options=getattr(connection, "socket_options", None),
+                label="S3 connector peer",
+            )
+        except socket.timeout as exc:
+            raise urllib3_exceptions.ConnectTimeoutError(
+                connection,
+                f"Connection to {hostname} timed out while selecting an approved peer",
+            ) from exc
+        except (OSError, OutboundHttpError, ValueError) as exc:
+            raise urllib3_exceptions.NewConnectionError(
+                connection,
+                f"S3 connector peer was rejected: {exc}",
+            ) from exc
+
+    class PinnedAWSHTTPConnection(awsrequest.AWSHTTPConnection):
+        _new_conn = pinned_new_connection
+
+    class PinnedAWSHTTPSConnection(awsrequest.AWSHTTPSConnection):
+        _new_conn = pinned_new_connection
+
+    class PinnedAWSHTTPConnectionPool(awsrequest.AWSHTTPConnectionPool):
+        ConnectionCls = PinnedAWSHTTPConnection
+
+    class PinnedAWSHTTPSConnectionPool(awsrequest.AWSHTTPSConnectionPool):
+        ConnectionCls = PinnedAWSHTTPSConnection
+
+    class PinnedURLLib3Session(httpsession.URLLib3Session):
+        def __init__(self, *args: Any, **kwargs: Any) -> None:
+            # A proxy would select the final target outside this process. Until
+            # proxy peer delegation is modeled, connector traffic is direct.
+            kwargs["proxies"] = {}
+            super().__init__(*args, **kwargs)
+            self._pool_classes_by_scheme = {
+                "http": PinnedAWSHTTPConnectionPool,
+                "https": PinnedAWSHTTPSConnectionPool,
+            }
+            manager = getattr(self, "_manager", None)
+            if manager is None or not hasattr(manager, "pool_classes_by_scheme"):
+                raise SdkPeerPinningError(
+                    "The installed botocore pool manager cannot enforce pinned connection classes"
+                )
+            manager.pool_classes_by_scheme = self._pool_classes_by_scheme
+
+    return PinnedURLLib3Session, PinnedAWSHTTPConnection, PinnedAWSHTTPSConnection
+
+
+@lru_cache(maxsize=1)
+def pinned_smb_connection_cache() -> dict[str, Any]:
+    """Return the Files-owned cache; unproven process-global sessions are never reused."""
+
+    return {}
+
+
+def install_pinned_smb_transport(smbclient: Any) -> Any:
+    """Install a process-wide fail-closed smbclient session factory.
+
+    smbclient routes initial connections, reconnects, and DFS targets through
+    ``smbclient._pool.register_session``. Replacing that single factory with a
+    behavior-compatible implementation ensures every target uses a socket
+    selected by Core's deployment-wide outbound policy.
+    """
+
+    try:
+        pool = import_module("smbclient._pool")
+        connection_module = import_module("smbprotocol.connection")
+        session_module = import_module("smbprotocol.session")
+        transport_module = import_module("smbprotocol.transport")
+    except ImportError as exc:
+        raise SdkPeerPinningError(
+            "SMB connector browsing requires the optional smbprotocol dependency"
+        ) from exc
+
+    current = getattr(pool, "register_session", None)
+    if getattr(current, "__govoplan_peer_pinned__", False):
+        expected_tcp = getattr(current, "__govoplan_pinned_tcp__", None)
+        if expected_tcp is None or getattr(connection_module, "Tcp", None) is not expected_tcp:
+            raise SdkPeerPinningError(
+                "The installed SMB transport changed after peer pinning; refusing to reuse the session factory"
+            )
+        return smbclient
+    required_parameters = {
+        "server",
+        "username",
+        "password",
+        "port",
+        "encrypt",
+        "connection_timeout",
+        "connection_cache",
+        "auth_protocol",
+        "require_signing",
+    }
+    if current is None or not required_parameters.issubset(
+        inspect.signature(current).parameters
+    ):
+        raise SdkPeerPinningError(
+            "The installed smbprotocol release does not expose the session seam required for peer pinning"
+        )
+
+    class PinnedTcp(transport_module.Tcp):
+        def connect(self) -> None:
+            with self._sock_lock:
+                if self.connected:
+                    return
+                try:
+                    self._sock = create_outbound_connection(
+                        self.server,
+                        int(self.port),
+                        timeout=self.timeout,
+                        label="SMB connector peer",
+                    )
+                except (OSError, OutboundHttpError, ValueError) as exc:
+                    raise ValueError(
+                        f"SMB connector peer '{self.server}:{self.port}' was rejected: {exc}"
+                    ) from exc
+                self._sock.settimeout(None)
+                self.connected = True
+
+    # Connection.connect() instantiates the module-level Tcp symbol on every
+    # reconnect. Replacing it process-wide is deliberate: an SMB connection
+    # created by another code path must become stricter, never bypass Files'
+    # peer boundary.
+    if not hasattr(connection_module, "Tcp"):
+        raise SdkPeerPinningError(
+            "The installed smbprotocol release cannot install the pinned TCP transport"
+        )
+    connection_module.Tcp = PinnedTcp
+
+    def pinned_register_session(
+        server: str,
+        username: str | None = None,
+        password: str | None = None,
+        port: int = 445,
+        encrypt: bool | None = None,
+        connection_timeout: float = 60,
+        connection_cache: dict[str, Any] | None = None,
+        auth_protocol: str = "negotiate",
+        require_signing: bool = True,
+    ) -> Any:
+        cache = pinned_smb_connection_cache() if connection_cache is None else connection_cache
+        connection_key = f"{server.lower()}:{port}"
+        connection = cache.get(connection_key)
+        transport = getattr(connection, "transport", None)
+        if connection is not None and not isinstance(transport, PinnedTcp):
+            disconnect = getattr(connection, "disconnect", None)
+            if callable(disconnect):
+                try:
+                    disconnect(close=True)
+                except Exception:
+                    pass
+            cache.pop(connection_key, None)
+            connection = None
+        if connection is None or not getattr(connection.transport, "connected", False):
+            connection = connection_module.Connection(
+                pool.ClientConfig().client_guid,
+                server,
+                port,
+                require_signing=require_signing,
+            )
+            connection.transport = PinnedTcp(server, port)
+            connection.connect(timeout=connection_timeout)
+            if not isinstance(connection.transport, PinnedTcp):
+                disconnect = getattr(connection, "disconnect", None)
+                if callable(disconnect):
+                    try:
+                        disconnect(close=True)
+                    except Exception:
+                        pass
+                raise SdkPeerPinningError(
+                    "smbprotocol replaced the required pinned TCP transport during connection setup"
+                )
+            cache[connection_key] = connection
+
+        session = next(
+            (
+                item
+                for item in connection.session_table.values()
+                if username is None or item.username == username
+            ),
+            None,
+        )
+        if session is None:
+            session = session_module.Session(
+                connection,
+                username=username,
+                password=password,
+                require_encryption=(encrypt is True),
+                auth_protocol=auth_protocol,
+            )
+            session.connect()
+        elif encrypt is not None:
+            if session.encrypt_data and not encrypt:
+                raise ValueError(
+                    "Cannot disable encryption on an already negotiated session."
+                )
+            if not session.encrypt_data and encrypt:
+                session.encrypt = True
+        return session
+
+    pinned_register_session.__govoplan_peer_pinned__ = True  # type: ignore[attr-defined]
+    pinned_register_session.__govoplan_pinned_tcp__ = PinnedTcp  # type: ignore[attr-defined]
+    pool.register_session = pinned_register_session
+    if hasattr(smbclient, "register_session"):
+        smbclient.register_session = pinned_register_session
+    return smbclient
+
+
+__all__ = [
+    "SdkPeerPinningError",
+    "create_pinned_s3_client",
+    "install_pinned_smb_transport",
+    "pinned_smb_connection_cache",
+]