QoL feature - select best interface on current system

When generating a default config instead of using a canned value like "eth0", hypd will isntead look at what interfaces the system has and make a best guess based on progressively narrowing filters.

README.md

@@ -20,13 +20,15 @@ Compared to most port knocking daemons, hyp is extremely fast, lightweight and h
 
 Port knocking clients have minimal requirements and can run on x86, ARM, MIPS, PowerPC, IBM390, or RISC-V. Currently only supported OS's are Linux and Windows, with support for Android planned to be added in the future.
 
-The port knocking daemon has more strict requirements and is only available for Linux. It requires the kernel be built with CONFIG_DEBUG_INFO_BTF, which most major distributions have out of the box. 
+The port knocking daemon has more strict requirements and is only available for Linux. It requires the kernel be built with CONFIG_DEBUG_INFO_BTF, which most major distributions have out of the box.  Additionally, hypd has some network requirements.  hypd is only expected to work on ethernet networks with IPv4.
+
+Once you get the runtime requirements sorted, be sure to check out the hyp and hypd directories of the repository for README information for how to use hyp.    
 
 ### Build Requirements
 
 Pre-built binaries for configurations I've tested are available on the [releases page](https://deadbeef.codes/steven/hyp/releases). This will likely run in many CPU architectures I haven't tested yet though. 
 
-To build this yourself, you will need Linux with packages for: git, clang, linux-headers-<architecture> libbpf-dev and golang. Check out the [Dockerfile ](https://deadbeef.codes/steven/hyp/src/branch/main/Dockerfile) as a reference for how the build environment for official releases is configured. Once the environment is ready, you can clone the repo and build.
+To build this yourself, you will need Linux with packages for: git, clang, linux-headers-<architecture> libbpf-dev and golang. Check out the [Dockerfile](https://deadbeef.codes/steven/hyp/src/branch/main/Dockerfile) as a reference for how the build environment for official releases is configured. Once the environment is ready, you can clone the repo and build.
 
 ```sh
 # Clone repository

hyp/README.md

@@ -1,9 +1,34 @@
-# hyp-client
+# hyp | Hide Your Ports Client
 
-The client expects there to be a file named hyp.secret in the same directory.  This file is generated by the hypd server using ./hypd generate secret.  
+The hyp client is used on machines to perform an authentic knock sequence.  
+
+### Usage
+
+You can use -h to get help for hyp and all its commands.  When figuring out how to do something, -h is your friend.
 
 ```bash
-# Example Usage
-# ./hyp knock <server>
-./hyp knock 192.168.50.5
-```
+# Get general hyp help
+./hyp -h
+
+# Get help specific to the hyp knock command
+./hyp knock -h
+```
+
+In order to use the hyp client, it must have the secret.  Secrets are generated by hypd, the knock daemon.  See the hypd README.md file for more information about generating secrets.
+
+Once you have the secret, you can then perform an authentic knock sequence to a server.
+
+```bash
+# Assumes secret is in file named my-first-secret in same directory
+./hyp knock 8.69.4.20 --secret my-first-secret
+
+# If you omit --secret, hyp will look for a file named hyp.secret
+./hyp knock 8.69.4.20
+```
+
+This will perform a single one-shot knock sequence and then hyp will exit.  You can also run hyp in a persistent mode where it will perform an authentic knock sequence at a specified interval.
+
+```bash
+# Performs an authentic knock sequence every 45 minutes
+./hyp knock 8.69.4.20 --refreshtime=45
+```

hyp/cmd/knock.go

@@ -47,6 +47,11 @@ Example usage:
 			panic(fmt.Errorf("maxjitter must be value between 1 and 1500"))
 		}
 
+		refreshTime, err := cmd.Flags().GetInt("refreshtime")
+		if err != nil {
+			panic(fmt.Errorf("failed to parse command flag 'refreshtime': %w", err))
+		}
+
 		secretBytes, err := os.ReadFile(secretFilePath)
 		if err != nil {
 			log.Fatalf("failed to read file 'hyp.secret': %v", err)
@@ -57,18 +62,29 @@ Example usage:
 			log.Fatalf("failed to base32 decode secret '%s': %v", secretFilePath, err)
 		}
 
-		ports, err := otphyp.GeneratePorts(decodedSecret, time.Now())
-		if err != nil {
-			log.Fatalf("failed to generate ports from shared secret: %v", err)
-		}
+		for {
 
-		// Transmit
-		for _, port := range ports {
-			fmt.Printf("knock | %s:%d\n", args[0], port)
-			conn, _ := net.Dial("udp", fmt.Sprintf("%s:%d", args[0], port))
-			conn.Write([]byte{0})
-			conn.Close()
-			time.Sleep(time.Millisecond * time.Duration(maxJitter)) // TBD: Make this configurable with flag (maxJitter)
+			ports, err := otphyp.GeneratePorts(decodedSecret, time.Now())
+			if err != nil {
+				log.Fatalf("failed to generate ports from shared secret: %v", err)
+			}
+
+			// Transmit
+			for _, port := range ports {
+				fmt.Printf("knock | %s:%d\n", args[0], port)
+				conn, _ := net.Dial("udp", fmt.Sprintf("%s:%d", args[0], port))
+				conn.Write([]byte{0})
+				conn.Close()
+				time.Sleep(time.Millisecond * time.Duration(maxJitter)) // TBD: Make this configurable with flag (maxJitter)
+			}
+
+			if refreshTime < 1 {
+				break
+			}
+
+			sleepDuration := time.Minute * time.Duration(refreshTime)
+			fmt.Printf("waiting until: %s...\n", time.Now().Add(sleepDuration).Format("15:04:05"))
+			time.Sleep(sleepDuration)
 		}
 	},
 }
@@ -76,6 +92,7 @@ Example usage:
 func init() {
 	rootCmd.AddCommand(knockCmd)
 
-	knockCmd.PersistentFlags().String("secret", "hyp.secret", "Path to the file containing the hyp secret.")
-	knockCmd.PersistentFlags().Int("maxjitter", 200, "Specifies the time in milliseconds between knock sequence transmissions.")
+	knockCmd.PersistentFlags().String("secret", "hyp.secret", "Path to the file containing the hyp secret")
+	knockCmd.PersistentFlags().Int("maxjitter", 200, "Specifies the time in milliseconds between transmissions while performing the knock sequence")
+	knockCmd.PersistentFlags().Int("refreshtime", 0, "If specified, the hyp client will run persistently and send a full knock sequence at this interval in minutes")
 }

hypd/README.md

@@ -1,9 +1,19 @@
 # hypd | Hide Your Ports Daemon
 
-hypd is the pork knocking daemon which listens for incoming authentic knock sequences.  
+hypd is the pork knocking daemon which listens for incoming authentic knock sequences.  When it sees an authentic knock sequence, it then performs an action.
 
 ### Usage
 
+You can use -h to get help for hypd and all its commands.  When figuring out how to do something, -h is your friend.
+
+```bash
+# Get general hypd help
+./hypd -h
+
+# Get help specific to the hypd generate command
+./hypd generate -h
+```
+
 Running hypd requires generating secrets which are then shared with hyp clients.  hypd is used to generate these secrets, and it's recommended you create a directory just for hyp secrets.
 
 ```bash
@@ -23,11 +33,15 @@ Running hypd requires specifying a configuration file.  It's recommended you gen
 ./hypd generate defaultconfig > hypd.conf
 ```
 
-Make sure you take the time to review the hypd.conf file and edit it to your liking, this is the most important step.  
+Make sure you take the time to review the hypd.conf file and edit it to your liking, this is the most important step.  Make sure the network interface is correct, hypd will make an educated guess based on the interfaces your system has.
+
+If you have complex requirements, you can make the successAction/timeoutAction an external shell script.  If you want to disable the timeoutAction, you can set timeoutSeconds to 0.
 
 Once you have set your config file, you can finally run hypd.
 
 ```bash
 # As root or sudo, specify the configuration file
 sudo ./hypd server hypd.conf
-```
+```
+
+If you encounter any errors while trying to run, address those.  If not, then you're now listening for incoming authentic knock sequences.  Make sure you distribute the secret to the client.  

hypd/configuration/configuration.go

@@ -57,8 +57,16 @@ func LoadConfiguration(configFilePath string) (*HypdConfiguration, error) {
 }
 
 func DefaultConfig() *HypdConfiguration {
+	var ifaceString string
+	iface, err := getDefaultNIC()
+	if err == nil {
+		ifaceString = iface.Name
+	} else {
+		ifaceString = "enp0s3" // fallback to fixed value
+	}
+
 	return &HypdConfiguration{
-		NetworkInterface:      "enp0s3",
+		NetworkInterface:      ifaceString,
 		PreSharedKeyDirectory: "./secrets/",
 		SuccessAction:         "iptables -A INPUT -p tcp -s %s --dport 22 -j ACCEPT",
 		TimeoutSeconds:        1440,

hypd/configuration/defaultNIC.go

@@ -0,0 +1,81 @@
+package configuration
+
+import (
+	"fmt"
+	"net"
+)
+
+// QoL feature to try and detect the best NIC for hyp
+func getDefaultNIC() (*net.Interface, error) {
+	ifaces, err := net.Interfaces()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get network interfaces on this system: %v", err)
+	}
+	if len(ifaces) < 1 {
+		return nil, fmt.Errorf("this system has no network interfaces: %v", err)
+	}
+
+	// Just pick one to start
+	selectedIface := ifaces[0]
+	filteredIfaces := make([]net.Interface, 0)
+
+	// Check for ethernet addresses
+	for _, iface := range ifaces {
+		if len(iface.HardwareAddr) == 6 {
+			selectedIface = iface
+			filteredIfaces = append(filteredIfaces, iface)
+		}
+	}
+	ifaces = filteredIfaces
+	filteredIfaces = make([]net.Interface, 0)
+
+	// Check for interfaces that are up and not loopbacks
+	for _, iface := range ifaces {
+		if iface.Flags&net.FlagUp != 0 && iface.Flags&net.FlagRunning != 0 && iface.Flags&net.FlagLoopback == 0 {
+			selectedIface = iface
+			filteredIfaces = append(filteredIfaces, iface)
+		}
+	}
+	ifaces = filteredIfaces
+	filteredIfaces = make([]net.Interface, 0)
+
+	// Check for interfaces that have IPv4 addresses assigned
+	for _, iface := range ifaces {
+		addresses, err := iface.Addrs()
+		if err != nil {
+			continue
+		}
+		for _, address := range addresses {
+			ip, _, err := net.ParseCIDR(address.String())
+			if err != nil {
+				continue
+			}
+			if ip.To4() != nil {
+				selectedIface = iface
+				filteredIfaces = append(filteredIfaces, iface)
+			}
+		}
+	}
+	ifaces = filteredIfaces
+	filteredIfaces = nil
+
+	// Check for interfaces that have non RFC1918 addresses assigned
+	for _, iface := range ifaces {
+		addresses, err := iface.Addrs()
+		if err != nil {
+			continue
+		}
+		for _, address := range addresses {
+			ip, _, err := net.ParseCIDR(address.String())
+			if err != nil {
+				continue
+			}
+			if !ip.IsPrivate() {
+				selectedIface = iface
+
+			}
+		}
+	}
+
+	return &selectedIface, nil // TBD
+}