transport: create Client interface (#132)

* plumbing: move plumbing/client package to plumbing/transport.

* transport: create Client interface.

* A Client can instantiate any client transport service.
* InstallProtocol installs a Client for a given protocol,
  instead of just a UploadPackService.
* A Client can open a session for fetch-pack or send-pack
  for a specific Endpoint.
* Adapt ssh and http clients to the new client interface.

* updated doc

1 files changed, 157 insertions, 0 deletions

diff --git a/plumbing/transport/ssh/auth_method.go b/plumbing/transport/ssh/auth_method.go
new file mode 100644
index 0000000..9c3d6f3
--- /dev/null
+++ b/plumbing/transport/ssh/auth_method.go
@@ -0,0 +1,157 @@
+package ssh
+
+import (
+	"fmt"
+	"net"
+	"os"
+
+	"golang.org/x/crypto/ssh"
+	"golang.org/x/crypto/ssh/agent"
+)
+
+// AuthMethod is the interface all auth methods for the ssh client
+// must implement. The clientConfig method returns the ssh client
+// configuration needed to establish an ssh connection.
+type AuthMethod interface {
+	clientConfig() *ssh.ClientConfig
+}
+
+// The names of the AuthMethod implementations. To be returned by the
+// Name() method. Most git servers only allow PublicKeysName and
+// PublicKeysCallbackName.
+const (
+	KeyboardInteractiveName = "ssh-keyboard-interactive"
+	PasswordName            = "ssh-password"
+	PasswordCallbackName    = "ssh-password-callback"
+	PublicKeysName          = "ssh-public-keys"
+	PublicKeysCallbackName  = "ssh-public-key-callback"
+)
+
+// KeyboardInteractive implements AuthMethod by using a
+// prompt/response sequence controlled by the server.
+type KeyboardInteractive struct {
+	User      string
+	Challenge ssh.KeyboardInteractiveChallenge
+}
+
+func (a *KeyboardInteractive) Name() string {
+	return KeyboardInteractiveName
+}
+
+func (a *KeyboardInteractive) String() string {
+	return fmt.Sprintf("user: %s, name: %s", a.User, a.Name())
+}
+
+func (a *KeyboardInteractive) clientConfig() *ssh.ClientConfig {
+	return &ssh.ClientConfig{
+		User: a.User,
+		Auth: []ssh.AuthMethod{ssh.KeyboardInteractiveChallenge(a.Challenge)},
+	}
+}
+
+// Password implements AuthMethod by using the given password.
+type Password struct {
+	User string
+	Pass string
+}
+
+func (a *Password) Name() string {
+	return PasswordName
+}
+
+func (a *Password) String() string {
+	return fmt.Sprintf("user: %s, name: %s", a.User, a.Name())
+}
+
+func (a *Password) clientConfig() *ssh.ClientConfig {
+	return &ssh.ClientConfig{
+		User: a.User,
+		Auth: []ssh.AuthMethod{ssh.Password(a.Pass)},
+	}
+}
+
+// PasswordCallback implements AuthMethod by using a callback
+// to fetch the password.
+type PasswordCallback struct {
+	User     string
+	Callback func() (pass string, err error)
+}
+
+func (a *PasswordCallback) Name() string {
+	return PasswordCallbackName
+}
+
+func (a *PasswordCallback) String() string {
+	return fmt.Sprintf("user: %s, name: %s", a.User, a.Name())
+}
+
+func (a *PasswordCallback) clientConfig() *ssh.ClientConfig {
+	return &ssh.ClientConfig{
+		User: a.User,
+		Auth: []ssh.AuthMethod{ssh.PasswordCallback(a.Callback)},
+	}
+}
+
+// PublicKeys implements AuthMethod by using the given
+// key pairs.
+type PublicKeys struct {
+	User   string
+	Signer ssh.Signer
+}
+
+func (a *PublicKeys) Name() string {
+	return PublicKeysName
+}
+
+func (a *PublicKeys) String() string {
+	return fmt.Sprintf("user: %s, name: %s", a.User, a.Name())
+}
+
+func (a *PublicKeys) clientConfig() *ssh.ClientConfig {
+	return &ssh.ClientConfig{
+		User: a.User,
+		Auth: []ssh.AuthMethod{ssh.PublicKeys(a.Signer)},
+	}
+}
+
+// PublicKeysCallback implements AuthMethod by asking a
+// ssh.agent.Agent to act as a signer.
+type PublicKeysCallback struct {
+	User     string
+	Callback func() (signers []ssh.Signer, err error)
+}
+
+func (a *PublicKeysCallback) Name() string {
+	return PublicKeysCallbackName
+}
+
+func (a *PublicKeysCallback) String() string {
+	return fmt.Sprintf("user: %s, name: %s", a.User, a.Name())
+}
+
+func (a *PublicKeysCallback) clientConfig() *ssh.ClientConfig {
+	return &ssh.ClientConfig{
+		User: a.User,
+		Auth: []ssh.AuthMethod{ssh.PublicKeysCallback(a.Callback)},
+	}
+}
+
+const DefaultSSHUsername = "git"
+
+// Opens a pipe with the ssh agent and uses the pipe
+// as the implementer of the public key callback function.
+func NewSSHAgentAuth(user string) (*PublicKeysCallback, error) {
+	if user == "" {
+		user = DefaultSSHUsername
+	}
+
+	pipe, err := net.Dial("unix", os.Getenv("SSH_AUTH_SOCK"))
+	if err != nil {
+		return nil, err
+	}
+
+	return &PublicKeysCallback{
+		User:     user,
+		Callback: agent.NewClient(pipe).Signers,
+	}, nil
+}