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connection_golang.go
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connection_golang.go
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package ssh
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"io"
"net"
"net/url"
"os"
"os/user"
"path"
"path/filepath"
"regexp"
"strings"
"time"
"github.com/containers/common/pkg/config"
"github.com/containers/storage/pkg/homedir"
"github.com/pkg/sftp"
"github.com/sirupsen/logrus"
"golang.org/x/crypto/ssh"
"golang.org/x/crypto/ssh/agent"
"golang.org/x/crypto/ssh/knownhosts"
)
func golangConnectionCreate(options ConnectionCreateOptions) error {
var match bool
var err error
if match, err = regexp.Match("^[A-Za-z][A-Za-z0-9+.-]*://", []byte(options.Path)); err != nil {
return fmt.Errorf("invalid destination: %w", err)
}
if !match {
options.Path = "ssh://" + options.Path
}
if len(options.Socket) > 0 {
options.Path += options.Socket
}
dst, uri, err := Validate(options.User, options.Path, options.Port, options.Identity)
if err != nil {
return err
}
if uri.Path == "" || uri.Path == "/" {
if uri.Path, err = getUDS(uri, options.Identity); err != nil {
return err
}
dst.URI += uri.Path
}
cfg, err := config.ReadCustomConfig()
if err != nil {
return err
}
if cfg.Engine.ServiceDestinations == nil {
cfg.Engine.ServiceDestinations = map[string]config.Destination{
options.Name: *dst,
}
cfg.Engine.ActiveService = options.Name
} else {
cfg.Engine.ServiceDestinations[options.Name] = *dst
}
return cfg.Write()
}
func golangConnectionDial(options ConnectionDialOptions) (*ConnectionDialReport, error) {
_, uri, err := Validate(options.User, options.Host, options.Port, options.Identity)
if err != nil {
return nil, err
}
cfg, err := ValidateAndConfigure(uri, options.Identity, options.InsecureIsMachineConnection)
if err != nil {
return nil, err
}
dial, err := ssh.Dial("tcp", uri.Host, cfg) // dial the client
if err != nil {
return nil, fmt.Errorf("failed to connect: %w", err)
}
return &ConnectionDialReport{dial}, nil
}
func golangConnectionExec(options ConnectionExecOptions) (*ConnectionExecReport, error) {
if !strings.HasPrefix(options.Host, "ssh://") {
options.Host = "ssh://" + options.Host
}
_, uri, err := Validate(options.User, options.Host, options.Port, options.Identity)
if err != nil {
return nil, err
}
cfg, err := ValidateAndConfigure(uri, options.Identity, false)
if err != nil {
return nil, err
}
dialAdd, err := ssh.Dial("tcp", uri.Host, cfg) // dial the client
if err != nil {
return nil, fmt.Errorf("failed to connect: %w", err)
}
out, err := ExecRemoteCommand(dialAdd, strings.Join(options.Args, " "))
if err != nil {
return nil, err
}
return &ConnectionExecReport{Response: string(out)}, nil
}
func golangConnectionScp(options ConnectionScpOptions) (*ConnectionScpReport, error) {
host, remoteFile, localFile, swap, err := ParseScpArgs(options)
if err != nil {
return nil, err
}
// removed for parsing
if !strings.HasPrefix(host, "ssh://") {
host = "ssh://" + host
}
_, uri, err := Validate(options.User, host, options.Port, options.Identity)
if err != nil {
return nil, err
}
cfg, err := ValidateAndConfigure(uri, options.Identity, false)
if err != nil {
return nil, err
}
dial, err := ssh.Dial("tcp", uri.Host, cfg) // dial the client
if err != nil {
return nil, fmt.Errorf("failed to connect: %w", err)
}
sc, err := sftp.NewClient(dial)
if err != nil {
return nil, err
}
f, err := os.OpenFile(localFile, (os.O_RDWR | os.O_CREATE), 0o644)
if err != nil {
return nil, err
}
parent := filepath.Dir(remoteFile)
path := string(filepath.Separator)
dirs := strings.Split(parent, path)
for _, dir := range dirs {
path = filepath.Join(path, dir)
// ignore errors due to most of the dirs already existing
_ = sc.Mkdir(path)
}
remote, err := sc.OpenFile(remoteFile, (os.O_RDWR | os.O_CREATE))
if err != nil {
return nil, err
}
defer remote.Close()
if !swap {
_, err = io.Copy(remote, f)
if err != nil {
return nil, err
}
} else {
_, err = io.Copy(f, remote)
if err != nil {
return nil, err
}
}
return &ConnectionScpReport{Response: remote.Name()}, nil
}
// ExecRemoteCommand takes a ssh client connection and a command to run and executes the
// command on the specified client. The function returns the Stdout from the client or the Stderr
func ExecRemoteCommand(dial *ssh.Client, run string) ([]byte, error) {
sess, err := dial.NewSession() // new ssh client session
if err != nil {
return nil, err
}
defer sess.Close()
var buffer bytes.Buffer
var bufferErr bytes.Buffer
sess.Stdout = &buffer // output from client funneled into buffer
sess.Stderr = &bufferErr // err form client funneled into buffer
if err := sess.Run(run); err != nil { // run the command on the ssh client
return nil, fmt.Errorf("%v: %w", bufferErr.String(), err)
}
return buffer.Bytes(), nil
}
func GetUserInfo(uri *url.URL) (*url.Userinfo, error) {
var (
usr *user.User
err error
)
if u, found := os.LookupEnv("_CONTAINERS_ROOTLESS_UID"); found {
usr, err = user.LookupId(u)
if err != nil {
return nil, fmt.Errorf("failed to lookup rootless user: %w", err)
}
} else {
usr, err = user.Current()
if err != nil {
return nil, fmt.Errorf("failed to obtain current user: %w", err)
}
}
pw, set := uri.User.Password()
if set {
return url.UserPassword(usr.Username, pw), nil
}
return url.User(usr.Username), nil
}
// ValidateAndConfigure will take a ssh url and an identity key (rsa and the like) and ensure the information given is valid
// iden iden can be blank to mean no identity key
// once the function validates the information it creates and returns an ssh.ClientConfig.
func ValidateAndConfigure(uri *url.URL, iden string, insecureIsMachineConnection bool) (*ssh.ClientConfig, error) {
var signers []ssh.Signer
passwd, passwdSet := uri.User.Password()
if iden != "" { // iden might be blank if coming from image scp or if no validation is needed
value := iden
s, err := PublicKey(value, []byte(passwd))
if err != nil {
return nil, fmt.Errorf("failed to read identity %q: %w", value, err)
}
signers = append(signers, s)
logrus.Debugf("SSH Ident Key %q %s %s", value, ssh.FingerprintSHA256(s.PublicKey()), s.PublicKey().Type())
} else if sock, found := os.LookupEnv("SSH_AUTH_SOCK"); found { // validate ssh information, specifically the unix file socket used by the ssh agent.
logrus.Debugf("Found SSH_AUTH_SOCK %q, ssh-agent signer enabled", sock)
c, err := net.Dial("unix", sock)
if err != nil {
return nil, err
}
agentSigners, err := agent.NewClient(c).Signers()
if err != nil {
return nil, err
}
signers = append(signers, agentSigners...)
if logrus.IsLevelEnabled(logrus.DebugLevel) {
for _, s := range agentSigners {
logrus.Debugf("SSH Agent Key %s %s", ssh.FingerprintSHA256(s.PublicKey()), s.PublicKey().Type())
}
}
}
var authMethods []ssh.AuthMethod // now we validate and check for the authorization methods, most notaibly public key authorization
if len(signers) > 0 {
dedup := make(map[string]ssh.Signer)
for _, s := range signers {
fp := ssh.FingerprintSHA256(s.PublicKey())
if _, found := dedup[fp]; found {
logrus.Debugf("Dedup SSH Key %s %s", ssh.FingerprintSHA256(s.PublicKey()), s.PublicKey().Type())
}
dedup[fp] = s
}
var uniq []ssh.Signer
for _, s := range dedup {
uniq = append(uniq, s)
}
authMethods = append(authMethods, ssh.PublicKeysCallback(func() ([]ssh.Signer, error) {
return uniq, nil
}))
}
if passwdSet { // if password authentication is given and valid, add to the list
authMethods = append(authMethods, ssh.Password(passwd))
}
if len(authMethods) == 0 {
authMethods = append(authMethods, ssh.PasswordCallback(func() (string, error) {
pass, err := ReadPassword(fmt.Sprintf("%s's login password:", uri.User.Username()))
return string(pass), err
}))
}
tick, err := time.ParseDuration("40s")
if err != nil {
return nil, err
}
var callback ssh.HostKeyCallback
if insecureIsMachineConnection {
callback = ssh.InsecureIgnoreHostKey()
} else {
callback = ssh.HostKeyCallback(func(host string, remote net.Addr, pubKey ssh.PublicKey) error {
keyFilePath := filepath.Join(homedir.Get(), ".ssh", "known_hosts")
known, err := knownhosts.New(keyFilePath)
if err != nil {
if !errors.Is(err, os.ErrNotExist) {
return err
}
keyDir := path.Dir(keyFilePath)
if _, err := os.Stat(keyDir); errors.Is(err, os.ErrNotExist) {
if err := os.Mkdir(keyDir, 0o700); err != nil {
return err
}
}
k, err := os.OpenFile(keyFilePath, os.O_RDWR|os.O_CREATE, 0o600)
if err != nil {
return err
}
k.Close()
known, err = knownhosts.New(keyFilePath)
if err != nil {
return err
}
}
// we need to check if there is an error from reading known hosts for this public key and if there is an error, what is it, and why is it happening?
// if it is a key mismatch we want to error since we know the host using another key
// however, if it is a general error not because of a known key, we want to add our key to the known_hosts file
hErr := known(host, remote, pubKey)
var keyErr *knownhosts.KeyError
// if keyErr.Want is not empty, we are receiving a different key meaning the host is known but we are using the wrong key
as := errors.As(hErr, &keyErr)
switch {
case as && len(keyErr.Want) > 0:
logrus.Warnf("ssh host key mismatch for host %s, got key %s of type %s", host, ssh.FingerprintSHA256(pubKey), pubKey.Type())
return keyErr
// if keyErr.Want is empty that just means we do not know this host yet, add it.
case as && len(keyErr.Want) == 0:
// write to known_hosts
err := addKnownHostsEntry(host, pubKey)
if err != nil {
if os.IsNotExist(err) {
logrus.Warn("podman will soon require a known_hosts file to function properly.")
return nil
}
return err
}
case hErr != nil:
return hErr
}
return nil
})
}
cfg := &ssh.ClientConfig{
User: uri.User.Username(),
Auth: authMethods,
HostKeyCallback: callback,
Timeout: tick,
}
return cfg, nil
}
func getUDS(uri *url.URL, iden string) (string, error) {
cfg, err := ValidateAndConfigure(uri, iden, false)
if err != nil {
return "", fmt.Errorf("failed to validate: %w", err)
}
dial, err := ssh.Dial("tcp", uri.Host, cfg)
if err != nil {
return "", fmt.Errorf("failed to connect: %w", err)
}
defer dial.Close()
session, err := dial.NewSession()
if err != nil {
return "", fmt.Errorf("failed to create new ssh session on %q: %w", uri.Host, err)
}
defer session.Close()
// Override podman binary for testing etc
podman := "podman"
if v, found := os.LookupEnv("PODMAN_BINARY"); found {
podman = v
}
infoJSON, err := ExecRemoteCommand(dial, podman+" info --format=json")
if err != nil {
return "", err
}
var info Info
if err := json.Unmarshal(infoJSON, &info); err != nil {
return "", fmt.Errorf("failed to parse 'podman info' results: %w", err)
}
if info.Host.RemoteSocket == nil || len(info.Host.RemoteSocket.Path) == 0 {
return "", fmt.Errorf("remote podman %q failed to report its UDS socket", uri.Host)
}
return info.Host.RemoteSocket.Path, nil
}
// addKnownHostsEntry adds (host, pubKey) to user’s known_hosts.
func addKnownHostsEntry(host string, pubKey ssh.PublicKey) error {
hd := homedir.Get()
known := filepath.Join(hd, ".ssh", "known_hosts")
f, err := os.OpenFile(known, os.O_APPEND|os.O_WRONLY, 0o600)
if err != nil {
return err
}
defer f.Close()
l := knownhosts.Line([]string{host}, pubKey)
if _, err = f.WriteString("\n" + l + "\n"); err != nil {
return err
}
logrus.Infof("key %s added to %s", ssh.FingerprintSHA256(pubKey), known)
return nil
}