podman/pkg/terminal/util.go

package terminal

import (
	"bufio"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"sync"

	"github.com/containers/storage/pkg/homedir"
	"github.com/sirupsen/logrus"
	"golang.org/x/crypto/ssh"
	"golang.org/x/crypto/ssh/knownhosts"
	"golang.org/x/crypto/ssh/terminal"
)

var (
	passPhrase   []byte
	phraseSync   sync.Once
	password     []byte
	passwordSync sync.Once
)

// ReadPassword prompts for a secret and returns value input by user from stdin
// Unlike terminal.ReadPassword(), $(echo $SECRET | podman...) is supported.
// Additionally, all input after `<secret>/n` is queued to podman command.
func ReadPassword(prompt string) (pw []byte, err error) {
	fd := int(os.Stdin.Fd())
	if terminal.IsTerminal(fd) {
		fmt.Fprint(os.Stderr, prompt)
		pw, err = terminal.ReadPassword(fd)
		fmt.Fprintln(os.Stderr)
		return
	}

	var b [1]byte
	for {
		n, err := os.Stdin.Read(b[:])
		// terminal.ReadPassword discards any '\r', so we do the same
		if n > 0 && b[0] != '\r' {
			if b[0] == '\n' {
				return pw, nil
			}
			pw = append(pw, b[0])
			// limit size, so that a wrong input won't fill up the memory
			if len(pw) > 1024 {
				err = errors.New("password too long, 1024 byte limit")
			}
		}
		if err != nil {
			// terminal.ReadPassword accepts EOF-terminated passwords
			// if non-empty, so we do the same
			if err == io.EOF && len(pw) > 0 {
				err = nil
			}
			return pw, err
		}
	}
}

func PublicKey(path string, passphrase []byte) (ssh.Signer, error) {
	key, err := ioutil.ReadFile(path)
	if err != nil {
		return nil, err
	}

	signer, err := ssh.ParsePrivateKey(key)
	if err != nil {
		if _, ok := err.(*ssh.PassphraseMissingError); !ok {
			return nil, err
		}
		if len(passphrase) == 0 {
			passphrase = ReadPassphrase()
		}
		return ssh.ParsePrivateKeyWithPassphrase(key, passphrase)
	}
	return signer, nil
}

func ReadPassphrase() []byte {
	phraseSync.Do(func() {
		secret, err := ReadPassword("Key Passphrase: ")
		if err != nil {
			secret = []byte{}
		}
		passPhrase = secret
	})
	return passPhrase
}

func ReadLogin() []byte {
	passwordSync.Do(func() {
		secret, err := ReadPassword("Login password: ")
		if err != nil {
			secret = []byte{}
		}
		password = secret
	})
	return password
}

func HostKey(host string) ssh.PublicKey {
	// parse OpenSSH known_hosts file
	// ssh or use ssh-keyscan to get initial key
	knownHosts := filepath.Join(homedir.Get(), ".ssh", "known_hosts")
	fd, err := os.Open(knownHosts)
	if err != nil {
		logrus.Error(err)
		return nil
	}

	// support -H parameter for ssh-keyscan
	hashhost := knownhosts.HashHostname(host)

	scanner := bufio.NewScanner(fd)
	for scanner.Scan() {
		_, hosts, key, _, _, err := ssh.ParseKnownHosts(scanner.Bytes())
		if err != nil {
			logrus.Errorf("Failed to parse known_hosts: %s", scanner.Text())
			continue
		}

		for _, h := range hosts {
			if h == host || h == hashhost {
				return key
			}
		}
	}

	return nil
}