path: root/cmd/puppeth/ssh.go

// Copyright 2017 The go-ethereum Authors
// This file is part of go-ethereum.
//
// go-ethereum 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.
//
// go-ethereum 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 go-ethereum. If not, see <http://www.gnu.org/licenses/>.

package main

import (
    "bufio"
    "bytes"
    "errors"
    "fmt"
    "io/ioutil"
    "net"
    "os"
    "os/user"
    "path/filepath"
    "strings"

    "github.com/dexon-foundation/dexon/log"
    "golang.org/x/crypto/ssh"
    "golang.org/x/crypto/ssh/terminal"
)

// sshClient is a small wrapper around Go's SSH client with a few utility methods
// implemented on top.
type sshClient struct {
    server  string // Server name or IP without port number
    address string // IP address of the remote server
    pubkey  []byte // RSA public key to authenticate the server
    client  *ssh.Client
    logger  log.Logger
}

// dial establishes an SSH connection to a remote node using the current user and
// the user's configured private RSA key. If that fails, password authentication
// is fallen back to. server can be a string like user:identity@server:port.
func dial(server string, pubkey []byte) (*sshClient, error) {
    // Figure out username, identity, hostname and port
    hostname := ""
    hostport := server
    username := ""
    identity := "id_rsa" // default

    if strings.Contains(server, "@") {
        prefix := server[:strings.Index(server, "@")]
        if strings.Contains(prefix, ":") {
            username = prefix[:strings.Index(prefix, ":")]
            identity = prefix[strings.Index(prefix, ":")+1:]
        } else {
            username = prefix
        }
        hostport = server[strings.Index(server, "@")+1:]
    }
    if strings.Contains(hostport, ":") {
        hostname = hostport[:strings.Index(hostport, ":")]
    } else {
        hostname = hostport
        hostport += ":22"
    }
    logger := log.New("server", server)
    logger.Debug("Attempting to establish SSH connection")

    user, err := user.Current()
    if err != nil {
        return nil, err
    }
    if username == "" {
        username = user.Username
    }
    // Configure the supported authentication methods (private key and password)
    var auths []ssh.AuthMethod

    path := filepath.Join(user.HomeDir, ".ssh", identity)
    if buf, err := ioutil.ReadFile(path); err != nil {
        log.Warn("No SSH key, falling back to passwords", "path", path, "err", err)
    } else {
        key, err := ssh.ParsePrivateKey(buf)
        if err != nil {
            fmt.Printf("What's the decryption password for %s? (won't be echoed)\n>", path)
            blob, err := terminal.ReadPassword(int(os.Stdin.Fd()))
            fmt.Println()
            if err != nil {
                log.Warn("Couldn't read password", "err", err)
            }
            key, err := ssh.ParsePrivateKeyWithPassphrase(buf, blob)
            if err != nil {
                log.Warn("Failed to decrypt SSH key, falling back to passwords", "path", path, "err", err)
            } else {
                auths = append(auths, ssh.PublicKeys(key))
            }
        } else {
            auths = append(auths, ssh.PublicKeys(key))
        }
    }
    auths = append(auths, ssh.PasswordCallback(func() (string, error) {
        fmt.Printf("What's the login password for %s at %s? (won't be echoed)\n> ", username, server)
        blob, err := terminal.ReadPassword(int(os.Stdin.Fd()))

        fmt.Println()
        return string(blob), err
    }))
    // Resolve the IP address of the remote server
    addr, err := net.LookupHost(hostname)
    if err != nil {
        return nil, err
    }
    if len(addr) == 0 {
        return nil, errors.New("no IPs associated with domain")
    }
    // Try to dial in to the remote server
    logger.Trace("Dialing remote SSH server", "user", username)
    keycheck := func(hostname string, remote net.Addr, key ssh.PublicKey) error {
        // If no public key is known for SSH, ask the user to confirm
        if pubkey == nil {
            fmt.Println()
            fmt.Printf("The authenticity of host '%s (%s)' can't be established.\n", hostname, remote)
            fmt.Printf("SSH key fingerprint is %s [MD5]\n", ssh.FingerprintLegacyMD5(key))
            fmt.Printf("Are you sure you want to continue connecting (yes/no)? ")

            text, err := bufio.NewReader(os.Stdin).ReadString('\n')
            switch {
            case err != nil:
                return err
            case strings.TrimSpace(text) == "yes":
                pubkey = key.Marshal()
                return nil
            default:
                return fmt.Errorf("unknown auth choice: %v", text)
            }
        }
        // If a public key exists for this SSH server, check that it matches
        if bytes.Equal(pubkey, key.Marshal()) {
            return nil
        }
        // We have a mismatch, forbid connecting
        return errors.New("ssh key mismatch, readd the machine to update")
    }
    client, err := ssh.Dial("tcp", hostport, &ssh.ClientConfig{User: username, Auth: auths, HostKeyCallback: keycheck})
    if err != nil {
        return nil, err
    }
    // Connection established, return our utility wrapper
    c := &sshClient{
        server:  hostname,
        address: addr[0],
        pubkey:  pubkey,
        client:  client,
        logger:  logger,
    }
    if err := c.init(); err != nil {
        client.Close()
        return nil, err
    }
    return c, nil
}

// init runs some initialization commands on the remote server to ensure it's
// capable of acting as puppeth target.
func (client *sshClient) init() error {
    client.logger.Debug("Verifying if docker is available")
    if out, err := client.Run("docker version"); err != nil {
        if len(out) == 0 {
            return err
        }
        return fmt.Errorf("docker configured incorrectly: %s", out)
    }
    client.logger.Debug("Verifying if docker-compose is available")
    if out, err := client.Run("docker-compose version"); err != nil {
        if len(out) == 0 {
            return err
        }
        return fmt.Errorf("docker-compose configured incorrectly: %s", out)
    }
    return nil
}

// Close terminates the connection to an SSH server.
func (client *sshClient) Close() error {
    return client.client.Close()
}

// Run executes a command on the remote server and returns the combined output
// along with any error status.
func (client *sshClient) Run(cmd string) ([]byte, error) {
    // Establish a single command session
    session, err := client.client.NewSession()
    if err != nil {
        return nil, err
    }
    defer session.Close()

    // Execute the command and return any output
    client.logger.Trace("Running command on remote server", "cmd", cmd)
    return session.CombinedOutput(cmd)
}

// Stream executes a command on the remote server and streams all outputs into
// the local stdout and stderr streams.
func (client *sshClient) Stream(cmd string) error {
    // Establish a single command session
    session, err := client.client.NewSession()
    if err != nil {
        return err
    }
    defer session.Close()

    session.Stdout = os.Stdout
    session.Stderr = os.Stderr

    // Execute the command and return any output
    client.logger.Trace("Streaming command on remote server", "cmd", cmd)
    return session.Run(cmd)
}

// Upload copies the set of files to a remote server via SCP, creating any non-
// existing folders in the mean time.
func (client *sshClient) Upload(files map[string][]byte) ([]byte, error) {
    // Establish a single command session
    session, err := client.client.NewSession()
    if err != nil {
        return nil, err
    }
    defer session.Close()

    // Create a goroutine that streams the SCP content
    go func() {
        out, _ := session.StdinPipe()
        defer out.Close()

        for file, content := range files {
            client.logger.Trace("Uploading file to server", "file", file, "bytes", len(content))

            fmt.Fprintln(out, "D0755", 0, filepath.Dir(file))             // Ensure the folder exists
            fmt.Fprintln(out, "C0644", len(content), filepath.Base(file)) // Create the actual file
            out.Write(content)                                            // Stream the data content
            fmt.Fprint(out, "\x00")                                       // Transfer end with \x00
            fmt.Fprintln(out, "E")                                        // Leave directory (simpler)
        }
    }()
    return session.CombinedOutput("/usr/bin/scp -v -tr ./")
}