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Add support for managed SSH transport #minor (#814)
This change drops the (hard) dependency on libssh2 and instead uses Go's implementation of SSH when libgit2 is not built with it.
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,242 @@ | ||
package git | ||
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/* | ||
#include <git2.h> | ||
#include <git2/sys/credential.h> | ||
*/ | ||
import "C" | ||
import ( | ||
"crypto/md5" | ||
"crypto/sha1" | ||
"crypto/sha256" | ||
"errors" | ||
"fmt" | ||
"io" | ||
"io/ioutil" | ||
"net" | ||
"net/url" | ||
"runtime" | ||
"unsafe" | ||
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"golang.org/x/crypto/ssh" | ||
) | ||
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// RegisterManagedSSHTransport registers a Go-native implementation of an SSH | ||
// transport that doesn't rely on any system libraries (e.g. libssh2). | ||
// | ||
// If Shutdown or ReInit are called, make sure that the smart transports are | ||
// freed before it. | ||
func RegisterManagedSSHTransport(protocol string) (*RegisteredSmartTransport, error) { | ||
return NewRegisteredSmartTransport(protocol, false, sshSmartSubtransportFactory) | ||
} | ||
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func registerManagedSSH() error { | ||
globalRegisteredSmartTransports.Lock() | ||
defer globalRegisteredSmartTransports.Unlock() | ||
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for _, protocol := range []string{"ssh", "ssh+git", "git+ssh"} { | ||
if _, ok := globalRegisteredSmartTransports.transports[protocol]; ok { | ||
continue | ||
} | ||
managed, err := newRegisteredSmartTransport(protocol, false, sshSmartSubtransportFactory, true) | ||
if err != nil { | ||
return fmt.Errorf("failed to register transport for %q: %v", protocol, err) | ||
} | ||
globalRegisteredSmartTransports.transports[protocol] = managed | ||
} | ||
return nil | ||
} | ||
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func sshSmartSubtransportFactory(remote *Remote, transport *Transport) (SmartSubtransport, error) { | ||
return &sshSmartSubtransport{ | ||
transport: transport, | ||
}, nil | ||
} | ||
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type sshSmartSubtransport struct { | ||
transport *Transport | ||
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lastAction SmartServiceAction | ||
client *ssh.Client | ||
session *ssh.Session | ||
stdin io.WriteCloser | ||
stdout io.Reader | ||
currentStream *sshSmartSubtransportStream | ||
} | ||
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func (t *sshSmartSubtransport) Action(urlString string, action SmartServiceAction) (SmartSubtransportStream, error) { | ||
runtime.LockOSThread() | ||
defer runtime.UnlockOSThread() | ||
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u, err := url.Parse(urlString) | ||
if err != nil { | ||
return nil, err | ||
} | ||
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var cmd string | ||
switch action { | ||
case SmartServiceActionUploadpackLs, SmartServiceActionUploadpack: | ||
if t.currentStream != nil { | ||
if t.lastAction == SmartServiceActionUploadpackLs { | ||
return t.currentStream, nil | ||
} | ||
t.Close() | ||
} | ||
cmd = fmt.Sprintf("git-upload-pack %q", u.Path) | ||
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case SmartServiceActionReceivepackLs, SmartServiceActionReceivepack: | ||
if t.currentStream != nil { | ||
if t.lastAction == SmartServiceActionReceivepackLs { | ||
return t.currentStream, nil | ||
} | ||
t.Close() | ||
} | ||
cmd = fmt.Sprintf("git-receive-pack %q", u.Path) | ||
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default: | ||
return nil, fmt.Errorf("unexpected action: %v", action) | ||
} | ||
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cred, err := t.transport.SmartCredentials("", CredentialTypeSSHKey|CredentialTypeSSHMemory) | ||
if err != nil { | ||
return nil, err | ||
} | ||
defer cred.Free() | ||
|
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sshConfig, err := getSSHConfigFromCredential(cred) | ||
if err != nil { | ||
return nil, err | ||
} | ||
sshConfig.HostKeyCallback = func(hostname string, remote net.Addr, key ssh.PublicKey) error { | ||
marshaledKey := key.Marshal() | ||
cert := &Certificate{ | ||
Kind: CertificateHostkey, | ||
Hostkey: HostkeyCertificate{ | ||
Kind: HostkeySHA1 | HostkeyMD5 | HostkeySHA256 | HostkeyRaw, | ||
HashMD5: md5.Sum(marshaledKey), | ||
HashSHA1: sha1.Sum(marshaledKey), | ||
HashSHA256: sha256.Sum256(marshaledKey), | ||
Hostkey: marshaledKey, | ||
SSHPublicKey: key, | ||
}, | ||
} | ||
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return t.transport.SmartCertificateCheck(cert, true, hostname) | ||
} | ||
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var addr string | ||
if u.Port() != "" { | ||
addr = fmt.Sprintf("%s:%s", u.Hostname(), u.Port()) | ||
} else { | ||
addr = fmt.Sprintf("%s:22", u.Hostname()) | ||
} | ||
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t.client, err = ssh.Dial("tcp", addr, sshConfig) | ||
if err != nil { | ||
return nil, err | ||
} | ||
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t.session, err = t.client.NewSession() | ||
if err != nil { | ||
return nil, err | ||
} | ||
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t.stdin, err = t.session.StdinPipe() | ||
if err != nil { | ||
return nil, err | ||
} | ||
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t.stdout, err = t.session.StdoutPipe() | ||
if err != nil { | ||
return nil, err | ||
} | ||
|
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if err := t.session.Start(cmd); err != nil { | ||
return nil, err | ||
} | ||
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t.lastAction = action | ||
t.currentStream = &sshSmartSubtransportStream{ | ||
owner: t, | ||
} | ||
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return t.currentStream, nil | ||
} | ||
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func (t *sshSmartSubtransport) Close() error { | ||
t.currentStream = nil | ||
if t.client != nil { | ||
t.stdin.Close() | ||
t.session.Wait() | ||
t.session.Close() | ||
t.client = nil | ||
} | ||
return nil | ||
} | ||
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func (t *sshSmartSubtransport) Free() { | ||
} | ||
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type sshSmartSubtransportStream struct { | ||
owner *sshSmartSubtransport | ||
} | ||
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func (stream *sshSmartSubtransportStream) Read(buf []byte) (int, error) { | ||
return stream.owner.stdout.Read(buf) | ||
} | ||
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func (stream *sshSmartSubtransportStream) Write(buf []byte) (int, error) { | ||
return stream.owner.stdin.Write(buf) | ||
} | ||
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func (stream *sshSmartSubtransportStream) Free() { | ||
} | ||
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func getSSHConfigFromCredential(cred *Credential) (*ssh.ClientConfig, error) { | ||
switch cred.Type() { | ||
case CredentialTypeSSHCustom: | ||
credSSHCustom := (*C.git_credential_ssh_custom)(unsafe.Pointer(cred.ptr)) | ||
data, ok := pointerHandles.Get(credSSHCustom.payload).(*credentialSSHCustomData) | ||
if !ok { | ||
return nil, errors.New("unsupported custom SSH credentials") | ||
} | ||
return &ssh.ClientConfig{ | ||
User: C.GoString(credSSHCustom.username), | ||
Auth: []ssh.AuthMethod{ssh.PublicKeys(data.signer)}, | ||
}, nil | ||
} | ||
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username, _, privatekey, passphrase, err := cred.GetSSHKey() | ||
if err != nil { | ||
return nil, err | ||
} | ||
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var pemBytes []byte | ||
if cred.Type() == CredentialTypeSSHMemory { | ||
pemBytes = []byte(privatekey) | ||
} else { | ||
pemBytes, err = ioutil.ReadFile(privatekey) | ||
if err != nil { | ||
return nil, err | ||
} | ||
} | ||
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var key ssh.Signer | ||
if passphrase != "" { | ||
key, err = ssh.ParsePrivateKeyWithPassphrase(pemBytes, []byte(passphrase)) | ||
if err != nil { | ||
return nil, err | ||
} | ||
} else { | ||
key, err = ssh.ParsePrivateKey(pemBytes) | ||
if err != nil { | ||
return nil, err | ||
} | ||
} | ||
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return &ssh.ClientConfig{ | ||
User: username, | ||
Auth: []ssh.AuthMethod{ssh.PublicKeys(key)}, | ||
}, nil | ||
} |