authz: add audit logging APIs (#6158)

authz/audit_logger.go

@@ -0,0 +1,126 @@
+/*
+ *
+ * Copyright 2023 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package authz
+
+import (
+	"encoding/json"
+	"sync"
+)
+
+// loggerBuilderRegistry holds a map of audit logger builders and a mutex
+// to facilitate thread-safe reading/writing operations.
+type loggerBuilderRegistry struct {
+	mu       sync.Mutex
+	builders map[string]AuditLoggerBuilder
+}
+
+var (
+	registry = loggerBuilderRegistry{
+		builders: make(map[string]AuditLoggerBuilder),
+	}
+)
+
+// RegisterAuditLoggerBuilder registers the builder in a global map
+// using b.Name() as the key.
+//
+// This should only be called during initialization time (i.e. in an init()
+// function). If multiple builders are registered with the same name,
+// the one registered last will take effect.
+func RegisterAuditLoggerBuilder(b AuditLoggerBuilder) {
+	registry.mu.Lock()
+	defer registry.mu.Unlock()
+	registry.builders[b.Name()] = b
+}
+
+// GetAuditLoggerBuilder returns a builder with the given name.
+// It returns nil if the builder is not found in the registry.
+func GetAuditLoggerBuilder(name string) AuditLoggerBuilder {
+	registry.mu.Lock()
+	defer registry.mu.Unlock()
+	return registry.builders[name]
+}
+
+// AuditEvent contains information passed to the audit logger as part of an
+// audit logging event.
+type AuditEvent struct {
+	// FullMethodName is the full method name of the audited RPC, in the format
+	// of "/pkg.Service/Method". For example, "/helloworld.Greeter/SayHello".
+	FullMethodName string
+	// Principal is the identity of the caller. Currently it will only be
+	// available in certificate-based TLS authentication.
+	Principal string
+	// PolicyName is the authorization policy name or the xDS RBAC filter name.
+	PolicyName string
+	// MatchedRule is the matched rule or policy name in the xDS RBAC filter.
+	// It will be empty if there is no match.
+	MatchedRule string
+	// Authorized indicates whether the audited RPC is authorized or not.
+	Authorized bool
+}
+
+// AuditLoggerConfig represents an opaque data structure holding an audit
+// logger configuration. Concrete types representing configuration of specific
+// audit loggers must embed this interface to implement it.
+type AuditLoggerConfig interface {
+	auditLoggerConfig()
+}
+
+// AuditLogger is the interface to be implemented by audit loggers.
+//
+// An audit logger is a logger instance that can be configured via the
+// authorization policy API or xDS HTTP RBAC filters. When the authorization
+// decision meets the condition for audit, all the configured audit loggers'
+// Log() method will be invoked to log that event.
+//
+// TODO(lwge): Change the link to the merged gRFC once it's ready.
+// Please refer to https://github.com/grpc/proposal/pull/346 for more details
+// about audit logging.
+type AuditLogger interface {
+	// Log performs audit logging for the provided audit event.
+	//
+	// This method is invoked in the RPC path and therefore implementations
+	// must not block.
+	Log(*AuditEvent)
+}
+
+// AuditLoggerBuilder is the interface to be implemented by audit logger
+// builders that are used at runtime to configure and instantiate audit loggers.
+//
+// Users who want to implement their own audit logging logic should
+// implement this interface, along with the AuditLogger interface, and register
+// it by calling RegisterAuditLoggerBuilder() at init time.
+//
+// TODO(lwge): Change the link to the merged gRFC once it's ready.
+// Please refer to https://github.com/grpc/proposal/pull/346 for more details
+// about audit logging.
+type AuditLoggerBuilder interface {
+	// ParseAuditLoggerConfig parses the given JSON bytes into a structured
+	// logger config this builder can use to build an audit logger.
+	ParseAuditLoggerConfig(config json.RawMessage) (AuditLoggerConfig, error)
+	// Build builds an audit logger with the given logger config.
+	// This will only be called with valid configs returned from
+	// ParseAuditLoggerConfig() and any runtime issues such as failing to
+	// create a file should be handled by the logger implementation instead of
+	// failing the logger instantiation. So implementers need to make sure it
+	// can return a logger without error at this stage.
+	Build(AuditLoggerConfig) AuditLogger
+	// Name returns the name of logger built by this builder.
+	// This is used to register and pick the builder.
+	Name() string
+}