Allow keep alives

Add sqlite pragmas to db config

docs/sliver-docs/pages/docs/md/Configuration Files.md

@@ -15,6 +15,12 @@ The Sliver server has a configuration file located in the `configs` sub-director
     "level": 4,
     "grpc_unary_payloads": false,
     "grpc_stream_payloads": false
+  },
+  "grpc": {
+    "keepalive": {
+      "min_time_seconds": 30,
+      "permit_without_stream": true
+    }
   }
 }
 ```
@@ -29,6 +35,10 @@ The Sliver server has a configuration file located in the `configs` sub-director
   - `level` - The `logrus` logging level (1 - 5), by default this is set to `4`, which is the `INFO` level; increasing this value increases the verbosity of the logs e.g. `DEBUG` is `5` and `SILENT` is `1`
   - `grpc_unary_payloads` - Log gRPC unary payloads
   - `grpc_stream_payloads` - Log gRPC streaming payloads
+- `grpc` - An object containing options for the server gRPC stack
+  - `keepalive` - gRPC keepalive enforcement configuration
+    - `min_time_seconds` - Minimum amount of time (in seconds) between client pings before the server sends a GOAWAY with `too_many_pings`
+    - `permit_without_stream` - Allow client pings when there are no active streams
 
 ## Database Configuration
 

docs/sliver-docs/pages/docs/md/Daemon Mode.md

@@ -19,6 +19,12 @@ $ cat ~/.sliver/configs/server.json
         "level": 5,
         "grpc_unary_payloads": false,
         "grpc_stream_payloads": false
+    },
+    "grpc": {
+        "keepalive": {
+            "min_time_seconds": 30,
+            "permit_without_stream": true
+        }
     }
 }
 ```

server/configs/server.go

@@ -30,7 +30,8 @@ import (
 )
 
 const (
-	serverConfigFileName = "server.json"
+	serverConfigFileName               = "server.json"
+	defaultGRPCKeepaliveMinTimeSeconds = int64(30)
 )
 
 var (
@@ -53,6 +54,17 @@ type LogConfig struct {
 	TLSKeyLogger       bool `json:"tls_key_logger"`
 }
 
+// GRPCKeepaliveConfig - gRPC keepalive enforcement settings
+type GRPCKeepaliveConfig struct {
+	MinTimeSeconds      int64 `json:"min_time_seconds"`
+	PermitWithoutStream *bool `json:"permit_without_stream"`
+}
+
+// GRPCConfig - gRPC server settings
+type GRPCConfig struct {
+	Keepalive *GRPCKeepaliveConfig `json:"keepalive"`
+}
+
 // DaemonConfig - Configure daemon mode
 type DaemonConfig struct {
 	Host      string `json:"host"`
@@ -135,6 +147,7 @@ type ServerConfig struct {
 	DaemonMode   bool               `json:"daemon_mode"`
 	DaemonConfig *DaemonConfig      `json:"daemon"`
 	Logs         *LogConfig         `json:"logs"`
+	GRPC         *GRPCConfig        `json:"grpc"`
 	Watchtower   *WatchTowerConfig  `json:"watch_tower"`
 	GoProxy      string             `json:"go_proxy"`
 	HTTPDefaults *HttpDefaultConfig `json:"http_default"`
@@ -199,6 +212,20 @@ func GetServerConfig() *ServerConfig {
 		config.DonutBypass = 1
 	}
 
+	if config.GRPC == nil {
+		config.GRPC = &GRPCConfig{}
+	}
+	if config.GRPC.Keepalive == nil {
+		config.GRPC.Keepalive = &GRPCKeepaliveConfig{}
+	}
+	if config.GRPC.Keepalive.MinTimeSeconds <= 0 {
+		config.GRPC.Keepalive.MinTimeSeconds = defaultGRPCKeepaliveMinTimeSeconds
+	}
+	if config.GRPC.Keepalive.PermitWithoutStream == nil {
+		defaultPermit := true
+		config.GRPC.Keepalive.PermitWithoutStream = &defaultPermit
+	}
+
 	err := config.Save() // This updates the config with any missing fields
 	if err != nil {
 		serverConfigLog.Errorf("Failed to save default config %s", err)
@@ -207,6 +234,7 @@ func GetServerConfig() *ServerConfig {
 }
 
 func getDefaultServerConfig() *ServerConfig {
+	defaultPermitWithoutStream := true
 	return &ServerConfig{
 		DaemonMode: false,
 		DaemonConfig: &DaemonConfig{
@@ -218,6 +246,12 @@ func getDefaultServerConfig() *ServerConfig {
 			GRPCUnaryPayloads:  false,
 			GRPCStreamPayloads: false,
 		},
+		GRPC: &GRPCConfig{
+			Keepalive: &GRPCKeepaliveConfig{
+				MinTimeSeconds:      defaultGRPCKeepaliveMinTimeSeconds,
+				PermitWithoutStream: &defaultPermitWithoutStream,
+			},
+		},
 		HTTPDefaults: &HttpDefaultConfig{
 			Headers: []models.HttpC2Header{
 				models.HttpC2Header{

server/transport/keepalive.go

@@ -0,0 +1,50 @@
+package transport
+
+/*
+	Sliver Implant Framework
+	Copyright (C) 2019  Bishop Fox
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+import (
+	"time"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/keepalive"
+)
+
+func grpcKeepaliveOptions() []grpc.ServerOption {
+	if serverConfig == nil || serverConfig.GRPC == nil || serverConfig.GRPC.Keepalive == nil {
+		return nil
+	}
+
+	minTimeSeconds := serverConfig.GRPC.Keepalive.MinTimeSeconds
+	if minTimeSeconds <= 0 {
+		return nil
+	}
+
+	permitWithoutStream := true
+	if serverConfig.GRPC.Keepalive.PermitWithoutStream != nil {
+		permitWithoutStream = *serverConfig.GRPC.Keepalive.PermitWithoutStream
+	}
+
+	policy := keepalive.EnforcementPolicy{
+		MinTime:             time.Duration(minTimeSeconds) * time.Second,
+		PermitWithoutStream: permitWithoutStream,
+	}
+	return []grpc.ServerOption{
+		grpc.KeepaliveEnforcementPolicy(policy),
+	}
+}

server/transport/local.go

@@ -43,6 +43,7 @@ func LocalListener() (*grpc.Server, *bufconn.Listener, error) {
 		grpc.MaxRecvMsgSize(ServerMaxMessageSize),
 		grpc.MaxSendMsgSize(ServerMaxMessageSize),
 	}
+	options = append(options, grpcKeepaliveOptions()...)
 	options = append(options, initMiddleware(false)...)
 	grpcServer := grpc.NewServer(options...)
 	rpcpb.RegisterSliverRPCServer(grpcServer, rpc.NewServer())

server/transport/mtls.go

@@ -64,6 +64,7 @@ func StartMtlsClientListener(host string, port uint16) (*grpc.Server, net.Listen
 		grpc.MaxRecvMsgSize(ServerMaxMessageSize),
 		grpc.MaxSendMsgSize(ServerMaxMessageSize),
 	}
+	options = append(options, grpcKeepaliveOptions()...)
 	options = append(options, initMiddleware(true)...)
 	grpcServer := grpc.NewServer(options...)
 	rpcpb.RegisterSliverRPCServer(grpcServer, rpc.NewServer())

server/transport/tailscale.go

@@ -81,6 +81,7 @@ func StartTsNetClientListener(hostname string, port uint16) (*grpc.Server, net.L
 		grpc.MaxRecvMsgSize(ServerMaxMessageSize),
 		grpc.MaxSendMsgSize(ServerMaxMessageSize),
 	}
+	options = append(options, grpcKeepaliveOptions()...)
 	options = append(options, initMiddleware(true)...)
 	grpcServer := grpc.NewServer(options...)
 	rpcpb.RegisterSliverRPCServer(grpcServer, rpc.NewServer())