Add support for SSH via Bastion Host (Juniper#121)

go.mod

@@ -1,8 +1,9 @@
-module github.com/Juniper/go-netconf
+module github.com/vpatel95/go-netconf
 
 go 1.12
 
 require (
+	github.com/Juniper/go-netconf v0.3.0
 	github.com/google/go-cmp v0.5.1
 	golang.org/x/crypto v0.1.0
 )

go.sum

@@ -1,18 +1,23 @@
+github.com/Juniper/go-netconf v0.3.0 h1:STAqk495sGA0MqQ3Q8mUmk/CmTfWuIfbXRqpDYXgWNA=
+github.com/Juniper/go-netconf v0.3.0/go.mod h1:QhfUOux77kzKAdY1+DOpQswtzp7LeeooYTn2MT7iXkY=
 github.com/google/go-cmp v0.5.1 h1:JFrFEBb2xKufg6XkJsJr+WbKb4FQlURi5RUcBveYu9k=
 github.com/google/go-cmp v0.5.1/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20200728195943-123391ffb6de/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/crypto v0.1.0 h1:MDRAIl0xIo9Io2xV565hzXHw3zVseKrJKodhohM5CjU=
 golang.org/x/crypto v0.1.0/go.mod h1:RecgLatLF4+eUMCP1PoPZQb+cVrJcOPbHkTkbkB9sbw=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
 golang.org/x/net v0.1.0/go.mod h1:Cx3nUiGt4eDBEyega/BKRp+/AlGL8hYe7U9odMt2Cco=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

netconf/transport_ssh.go

@@ -9,6 +9,7 @@ package netconf
 import (
 	"crypto/x509"
 	"encoding/pem"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"net"
@@ -21,6 +22,8 @@ import (
 )
 
 const (
+	// bastionDefaultPort is the default port used when SSH via Bastion
+	bastionDefaultPort = 22
 	// sshDefaultPort is the default SSH port used when communicating with
 	// NETCONF
 	sshDefaultPort = 830
@@ -60,6 +63,52 @@ func (t *TransportSSH) Close() error {
 	return fmt.Errorf("No connection to close")
 }
 
+// DialWithBasstion connects and establishes SSH sessions over bastion host
+//
+// bastion can be an IP address (e.g) 172.16.2.1 which uses default port 22.
+// Bastion can also specify port with format <host>:<port> (e.g 172.16.2.1:5001)
+// target can be an IP address (e.g.) 172.16.1.1 which utlizes the default
+// NETCONF over SSH port of 830.  Target can also specify a port with the
+// following format <host>:<port (e.g 172.16.1.1:22)
+//
+// config takes a ssh.ClientConfig connection. See documentation for
+// go.crypto/ssh for documenation.  There is a helper function SSHConfigPassword
+// thar returns a ssh.ClientConfig for simple username/password authentication
+func (t *TransportSSH) DialWithBasstion(bastion, target string, bastionConf, config *ssh.ClientConfig) error {
+	var err error
+
+	if !strings.Contains(bastion, ":") {
+		bastion = fmt.Sprintf("%s:%d", bastion, bastionDefaultPort)
+	}
+
+	bastionClient, err := ssh.Dial("tcp", bastion, bastionConf)
+	if err != nil {
+		return err
+	}
+
+	if !strings.Contains(target, ":") {
+		target = fmt.Sprintf("%s:%d", target, sshDefaultPort)
+	}
+
+	targetConn, err := bastionClient.Dial("tcp", target)
+	if err != nil {
+		return err
+	}
+
+	ncc, chans, reqs, err := ssh.NewClientConn(targetConn, target, config)
+	if err != nil {
+		return err
+	}
+
+	t.sshClient = ssh.NewClient(ncc, chans, reqs)
+	if t.sshClient == nil {
+		return errors.New("Error getting SSH Client for " + target + " via Bastion " + bastion)
+	}
+
+	err = t.setupSession()
+	return err
+}
+
 // Dial connects and establishes SSH sessions
 //
 // target can be an IP address (e.g.) 172.16.1.1 which utlizes the default
@@ -117,6 +166,18 @@ func NewSSHSession(conn net.Conn, config *ssh.ClientConfig) (*Session, error) {
 	return NewSession(t), nil
 }
 
+// DialSSHWithBastion creates a new NETCONF session using a SSH Transport.
+// See TransportSSH.Dial for arguments.
+func DialSSHWithBastion(bastion, target string, bastionConf, config *ssh.ClientConfig) (*Session, error) {
+	var t TransportSSH
+	err := t.DialWithBasstion(bastion, target, bastionConf, config)
+	if err != nil {
+		t.Close()
+		return nil, err
+	}
+	return NewSession(&t), nil
+}
+
 // DialSSH creates a new NETCONF session using a SSH Transport.
 // See TransportSSH.Dial for arguments.
 func DialSSH(target string, config *ssh.ClientConfig) (*Session, error) {