Add ssh_config parsing

.gitignore

@@ -1,4 +1,4 @@
-/ipng-router-backup
+ipng-router-backup
 /*.yaml
 
 # Debian packaging artifacts

src/go.mod

@@ -10,6 +10,7 @@ require (
 
 require (
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/kevinburke/ssh_config v1.2.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	golang.org/x/sys v0.16.0 // indirect
 )

src/go.sum

@@ -1,6 +1,8 @@
 github.com/cpuguy83/go-md2man/v2 v2.0.3/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
+github.com/kevinburke/ssh_config v1.2.0 h1:x584FjTGwHzMwvHx18PXxbBVzfnxogHaAReU4gf13a4=
+github.com/kevinburke/ssh_config v1.2.0/go.mod h1:CT57kijsi8u/K/BOFA39wgDQJ9CxiF4nAY/ojJ6r6mM=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
 github.com/spf13/cobra v1.8.0 h1:7aJaZx1B85qltLMc546zn58BxxfZdR/W22ej9CFoEf0=
 github.com/spf13/cobra v1.8.0/go.mod h1:WXLWApfZ71AjXPya3WOlMsY9yMs7YeiHhFVlvLyhcho=

src/main.go

@@ -10,9 +10,11 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"strconv"
 	"strings"
 	"time"
 
+	"github.com/kevinburke/ssh_config"
 	"github.com/spf13/cobra"
 	"golang.org/x/crypto/ssh"
 	"golang.org/x/crypto/ssh/agent"
@@ -60,12 +62,70 @@ func NewRouterBackup(hostname, username, password, keyFile string, port int) *Ro
 
 // Connect establishes SSH connection to the router
 func (rb *RouterBackup) Connect() error {
+	// Get SSH config values for this host
+	hostname := ssh_config.Get(rb.hostname, "Hostname")
+	if hostname == "" {
+		hostname = rb.hostname
+	}
+
+	portStr := ssh_config.Get(rb.hostname, "Port")
+	port := rb.port
+	if portStr != "" {
+		if p, err := strconv.Atoi(portStr); err == nil {
+			port = p
+		}
+	}
+
+	username := ssh_config.Get(rb.hostname, "User")
+	if rb.username != "" {
+		username = rb.username
+	}
+
+	keyFile := ssh_config.Get(rb.hostname, "IdentityFile")
+	if rb.keyFile != "" {
+		keyFile = rb.keyFile
+	}
+
 	config := &ssh.ClientConfig{
-		User:            rb.username,
+		User:            username,
 		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
 		Timeout:         30 * time.Second,
 	}
 
+	// Apply SSH config crypto settings with compatibility filtering
+	if kexAlgorithms := ssh_config.Get(rb.hostname, "KexAlgorithms"); kexAlgorithms != "" && !strings.HasPrefix(kexAlgorithms, "+") {
+		// Only apply if it's an explicit list, not a +append
+		algorithms := strings.Split(kexAlgorithms, ",")
+		var finalAlgorithms []string
+		for _, alg := range algorithms {
+			finalAlgorithms = append(finalAlgorithms, strings.TrimSpace(alg))
+		}
+		config.KeyExchanges = finalAlgorithms
+	}
+
+	// Note: Cipher overrides disabled - Go SSH library defaults work
+	// if ciphers := ssh_config.Get(rb.hostname, "Ciphers"); ciphers != "" {
+	//	 config.Ciphers = ...
+	// }
+
+	if macs := ssh_config.Get(rb.hostname, "MACs"); macs != "" {
+		macList := strings.Split(macs, ",")
+		for i, mac := range macList {
+			macList[i] = strings.TrimSpace(mac)
+		}
+		config.MACs = macList
+	}
+
+	if hostKeyAlgorithms := ssh_config.Get(rb.hostname, "HostKeyAlgorithms"); hostKeyAlgorithms != "" && !strings.HasPrefix(hostKeyAlgorithms, "+") {
+		// Only apply if it's an explicit list, not a +append
+		algorithms := strings.Split(hostKeyAlgorithms, ",")
+		var finalAlgorithms []string
+		for _, alg := range algorithms {
+			finalAlgorithms = append(finalAlgorithms, strings.TrimSpace(alg))
+		}
+		config.HostKeyAlgorithms = finalAlgorithms
+	}
+
 	// Try SSH agent first if available
 	if sshAuthSock := os.Getenv("SSH_AUTH_SOCK"); sshAuthSock != "" {
 		if conn, err := net.Dial("unix", sshAuthSock); err == nil {
@@ -75,8 +135,16 @@ func (rb *RouterBackup) Connect() error {
 	}
 
 	// If SSH agent didn't work, try key file
-	if len(config.Auth) == 0 && rb.keyFile != "" {
+	if len(config.Auth) == 0 && keyFile != "" {
-		key, err := ioutil.ReadFile(rb.keyFile)
+		// Expand ~ in keyFile path
+		if strings.HasPrefix(keyFile, "~/") {
+			homeDir, err := os.UserHomeDir()
+			if err == nil {
+				keyFile = filepath.Join(homeDir, keyFile[2:])
+			}
+		}
+
+		key, err := ioutil.ReadFile(keyFile)
 		if err != nil {
 			return fmt.Errorf("unable to read private key: %v", err)
 		}
@@ -98,14 +166,14 @@ func (rb *RouterBackup) Connect() error {
 		return fmt.Errorf("no authentication method available")
 	}
 
-	address := fmt.Sprintf("%s:%d", rb.hostname, rb.port)
+	address := fmt.Sprintf("%s:%d", hostname, port)
-	client, err := ssh.Dial("tcp", address, config)
+	client, err := ssh.Dial("tcp4", address, config)
 	if err != nil {
-		return fmt.Errorf("failed to connect to %s: %v", rb.hostname, err)
+		return fmt.Errorf("failed to connect to %s: %v", hostname, err)
 	}
 
 	rb.client = client
-	fmt.Printf("Successfully connected to %s\n", rb.hostname)
+	fmt.Printf("Successfully connected to %s\n", hostname)
 	return nil
 }