7 files changed, 1539 insertions, 0 deletions

diff --git a/modules/crypto/ssh/agent/client.go b/modules/crypto/ssh/agent/client.go
new file mode 100755
index 00000000..1b50d756
--- /dev/null
+++ b/modules/crypto/ssh/agent/client.go
@@ -0,0 +1,615 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+  Package agent implements a client to an ssh-agent daemon.
+
+References:
+  [PROTOCOL.agent]:    http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL.agent?rev=HEAD
+*/
+package agent // import "golang.org/x/crypto/ssh/agent"
+
+import (
+	"bytes"
+	"crypto/dsa"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rsa"
+	"encoding/base64"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"math/big"
+	"sync"
+
+	"github.com/gogits/gogs/modules/crypto/ssh"
+)
+
+// Agent represents the capabilities of an ssh-agent.
+type Agent interface {
+	// List returns the identities known to the agent.
+	List() ([]*Key, error)
+
+	// Sign has the agent sign the data using a protocol 2 key as defined
+	// in [PROTOCOL.agent] section 2.6.2.
+	Sign(key ssh.PublicKey, data []byte) (*ssh.Signature, error)
+
+	// Add adds a private key to the agent.
+	Add(key AddedKey) error
+
+	// Remove removes all identities with the given public key.
+	Remove(key ssh.PublicKey) error
+
+	// RemoveAll removes all identities.
+	RemoveAll() error
+
+	// Lock locks the agent. Sign and Remove will fail, and List will empty an empty list.
+	Lock(passphrase []byte) error
+
+	// Unlock undoes the effect of Lock
+	Unlock(passphrase []byte) error
+
+	// Signers returns signers for all the known keys.
+	Signers() ([]ssh.Signer, error)
+}
+
+// AddedKey describes an SSH key to be added to an Agent.
+type AddedKey struct {
+	// PrivateKey must be a *rsa.PrivateKey, *dsa.PrivateKey or
+	// *ecdsa.PrivateKey, which will be inserted into the agent.
+	PrivateKey interface{}
+	// Certificate, if not nil, is communicated to the agent and will be
+	// stored with the key.
+	Certificate *ssh.Certificate
+	// Comment is an optional, free-form string.
+	Comment string
+	// LifetimeSecs, if not zero, is the number of seconds that the
+	// agent will store the key for.
+	LifetimeSecs uint32
+	// ConfirmBeforeUse, if true, requests that the agent confirm with the
+	// user before each use of this key.
+	ConfirmBeforeUse bool
+}
+
+// See [PROTOCOL.agent], section 3.
+const (
+	agentRequestV1Identities = 1
+
+	// 3.2 Requests from client to agent for protocol 2 key operations
+	agentAddIdentity         = 17
+	agentRemoveIdentity      = 18
+	agentRemoveAllIdentities = 19
+	agentAddIdConstrained    = 25
+
+	// 3.3 Key-type independent requests from client to agent
+	agentAddSmartcardKey            = 20
+	agentRemoveSmartcardKey         = 21
+	agentLock                       = 22
+	agentUnlock                     = 23
+	agentAddSmartcardKeyConstrained = 26
+
+	// 3.7 Key constraint identifiers
+	agentConstrainLifetime = 1
+	agentConstrainConfirm  = 2
+)
+
+// maxAgentResponseBytes is the maximum agent reply size that is accepted. This
+// is a sanity check, not a limit in the spec.
+const maxAgentResponseBytes = 16 << 20
+
+// Agent messages:
+// These structures mirror the wire format of the corresponding ssh agent
+// messages found in [PROTOCOL.agent].
+
+// 3.4 Generic replies from agent to client
+const agentFailure = 5
+
+type failureAgentMsg struct{}
+
+const agentSuccess = 6
+
+type successAgentMsg struct{}
+
+// See [PROTOCOL.agent], section 2.5.2.
+const agentRequestIdentities = 11
+
+type requestIdentitiesAgentMsg struct{}
+
+// See [PROTOCOL.agent], section 2.5.2.
+const agentIdentitiesAnswer = 12
+
+type identitiesAnswerAgentMsg struct {
+	NumKeys uint32 `sshtype:"12"`
+	Keys    []byte `ssh:"rest"`
+}
+
+// See [PROTOCOL.agent], section 2.6.2.
+const agentSignRequest = 13
+
+type signRequestAgentMsg struct {
+	KeyBlob []byte `sshtype:"13"`
+	Data    []byte
+	Flags   uint32
+}
+
+// See [PROTOCOL.agent], section 2.6.2.
+
+// 3.6 Replies from agent to client for protocol 2 key operations
+const agentSignResponse = 14
+
+type signResponseAgentMsg struct {
+	SigBlob []byte `sshtype:"14"`
+}
+
+type publicKey struct {
+	Format string
+	Rest   []byte `ssh:"rest"`
+}
+
+// Key represents a protocol 2 public key as defined in
+// [PROTOCOL.agent], section 2.5.2.
+type Key struct {
+	Format  string
+	Blob    []byte
+	Comment string
+}
+
+func clientErr(err error) error {
+	return fmt.Errorf("agent: client error: %v", err)
+}
+
+// String returns the storage form of an agent key with the format, base64
+// encoded serialized key, and the comment if it is not empty.
+func (k *Key) String() string {
+	s := string(k.Format) + " " + base64.StdEncoding.EncodeToString(k.Blob)
+
+	if k.Comment != "" {
+		s += " " + k.Comment
+	}
+
+	return s
+}
+
+// Type returns the public key type.
+func (k *Key) Type() string {
+	return k.Format
+}
+
+// Marshal returns key blob to satisfy the ssh.PublicKey interface.
+func (k *Key) Marshal() []byte {
+	return k.Blob
+}
+
+// Verify satisfies the ssh.PublicKey interface, but is not
+// implemented for agent keys.
+func (k *Key) Verify(data []byte, sig *ssh.Signature) error {
+	return errors.New("agent: agent key does not know how to verify")
+}
+
+type wireKey struct {
+	Format string
+	Rest   []byte `ssh:"rest"`
+}
+
+func parseKey(in []byte) (out *Key, rest []byte, err error) {
+	var record struct {
+		Blob    []byte
+		Comment string
+		Rest    []byte `ssh:"rest"`
+	}
+
+	if err := ssh.Unmarshal(in, &record); err != nil {
+		return nil, nil, err
+	}
+
+	var wk wireKey
+	if err := ssh.Unmarshal(record.Blob, &wk); err != nil {
+		return nil, nil, err
+	}
+
+	return &Key{
+		Format:  wk.Format,
+		Blob:    record.Blob,
+		Comment: record.Comment,
+	}, record.Rest, nil
+}
+
+// client is a client for an ssh-agent process.
+type client struct {
+	// conn is typically a *net.UnixConn
+	conn io.ReadWriter
+	// mu is used to prevent concurrent access to the agent
+	mu sync.Mutex
+}
+
+// NewClient returns an Agent that talks to an ssh-agent process over
+// the given connection.
+func NewClient(rw io.ReadWriter) Agent {
+	return &client{conn: rw}
+}
+
+// call sends an RPC to the agent. On success, the reply is
+// unmarshaled into reply and replyType is set to the first byte of
+// the reply, which contains the type of the message.
+func (c *client) call(req []byte) (reply interface{}, err error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	msg := make([]byte, 4+len(req))
+	binary.BigEndian.PutUint32(msg, uint32(len(req)))
+	copy(msg[4:], req)
+	if _, err = c.conn.Write(msg); err != nil {
+		return nil, clientErr(err)
+	}
+
+	var respSizeBuf [4]byte
+	if _, err = io.ReadFull(c.conn, respSizeBuf[:]); err != nil {
+		return nil, clientErr(err)
+	}
+	respSize := binary.BigEndian.Uint32(respSizeBuf[:])
+	if respSize > maxAgentResponseBytes {
+		return nil, clientErr(err)
+	}
+
+	buf := make([]byte, respSize)
+	if _, err = io.ReadFull(c.conn, buf); err != nil {
+		return nil, clientErr(err)
+	}
+	reply, err = unmarshal(buf)
+	if err != nil {
+		return nil, clientErr(err)
+	}
+	return reply, err
+}
+
+func (c *client) simpleCall(req []byte) error {
+	resp, err := c.call(req)
+	if err != nil {
+		return err
+	}
+	if _, ok := resp.(*successAgentMsg); ok {
+		return nil
+	}
+	return errors.New("agent: failure")
+}
+
+func (c *client) RemoveAll() error {
+	return c.simpleCall([]byte{agentRemoveAllIdentities})
+}
+
+func (c *client) Remove(key ssh.PublicKey) error {
+	req := ssh.Marshal(&agentRemoveIdentityMsg{
+		KeyBlob: key.Marshal(),
+	})
+	return c.simpleCall(req)
+}
+
+func (c *client) Lock(passphrase []byte) error {
+	req := ssh.Marshal(&agentLockMsg{
+		Passphrase: passphrase,
+	})
+	return c.simpleCall(req)
+}
+
+func (c *client) Unlock(passphrase []byte) error {
+	req := ssh.Marshal(&agentUnlockMsg{
+		Passphrase: passphrase,
+	})
+	return c.simpleCall(req)
+}
+
+// List returns the identities known to the agent.
+func (c *client) List() ([]*Key, error) {
+	// see [PROTOCOL.agent] section 2.5.2.
+	req := []byte{agentRequestIdentities}
+
+	msg, err := c.call(req)
+	if err != nil {
+		return nil, err
+	}
+
+	switch msg := msg.(type) {
+	case *identitiesAnswerAgentMsg:
+		if msg.NumKeys > maxAgentResponseBytes/8 {
+			return nil, errors.New("agent: too many keys in agent reply")
+		}
+		keys := make([]*Key, msg.NumKeys)
+		data := msg.Keys
+		for i := uint32(0); i < msg.NumKeys; i++ {
+			var key *Key
+			var err error
+			if key, data, err = parseKey(data); err != nil {
+				return nil, err
+			}
+			keys[i] = key
+		}
+		return keys, nil
+	case *failureAgentMsg:
+		return nil, errors.New("agent: failed to list keys")
+	}
+	panic("unreachable")
+}
+
+// Sign has the agent sign the data using a protocol 2 key as defined
+// in [PROTOCOL.agent] section 2.6.2.
+func (c *client) Sign(key ssh.PublicKey, data []byte) (*ssh.Signature, error) {
+	req := ssh.Marshal(signRequestAgentMsg{
+		KeyBlob: key.Marshal(),
+		Data:    data,
+	})
+
+	msg, err := c.call(req)
+	if err != nil {
+		return nil, err
+	}
+
+	switch msg := msg.(type) {
+	case *signResponseAgentMsg:
+		var sig ssh.Signature
+		if err := ssh.Unmarshal(msg.SigBlob, &sig); err != nil {
+			return nil, err
+		}
+
+		return &sig, nil
+	case *failureAgentMsg:
+		return nil, errors.New("agent: failed to sign challenge")
+	}
+	panic("unreachable")
+}
+
+// unmarshal parses an agent message in packet, returning the parsed
+// form and the message type of packet.
+func unmarshal(packet []byte) (interface{}, error) {
+	if len(packet) < 1 {
+		return nil, errors.New("agent: empty packet")
+	}
+	var msg interface{}
+	switch packet[0] {
+	case agentFailure:
+		return new(failureAgentMsg), nil
+	case agentSuccess:
+		return new(successAgentMsg), nil
+	case agentIdentitiesAnswer:
+		msg = new(identitiesAnswerAgentMsg)
+	case agentSignResponse:
+		msg = new(signResponseAgentMsg)
+	default:
+		return nil, fmt.Errorf("agent: unknown type tag %d", packet[0])
+	}
+	if err := ssh.Unmarshal(packet, msg); err != nil {
+		return nil, err
+	}
+	return msg, nil
+}
+
+type rsaKeyMsg struct {
+	Type        string `sshtype:"17"`
+	N           *big.Int
+	E           *big.Int
+	D           *big.Int
+	Iqmp        *big.Int // IQMP = Inverse Q Mod P
+	P           *big.Int
+	Q           *big.Int
+	Comments    string
+	Constraints []byte `ssh:"rest"`
+}
+
+type dsaKeyMsg struct {
+	Type        string `sshtype:"17"`
+	P           *big.Int
+	Q           *big.Int
+	G           *big.Int
+	Y           *big.Int
+	X           *big.Int
+	Comments    string
+	Constraints []byte `ssh:"rest"`
+}
+
+type ecdsaKeyMsg struct {
+	Type        string `sshtype:"17"`
+	Curve       string
+	KeyBytes    []byte
+	D           *big.Int
+	Comments    string
+	Constraints []byte `ssh:"rest"`
+}
+
+// Insert adds a private key to the agent.
+func (c *client) insertKey(s interface{}, comment string, constraints []byte) error {
+	var req []byte
+	switch k := s.(type) {
+	case *rsa.PrivateKey:
+		if len(k.Primes) != 2 {
+			return fmt.Errorf("agent: unsupported RSA key with %d primes", len(k.Primes))
+		}
+		k.Precompute()
+		req = ssh.Marshal(rsaKeyMsg{
+			Type:        ssh.KeyAlgoRSA,
+			N:           k.N,
+			E:           big.NewInt(int64(k.E)),
+			D:           k.D,
+			Iqmp:        k.Precomputed.Qinv,
+			P:           k.Primes[0],
+			Q:           k.Primes[1],
+			Comments:    comment,
+			Constraints: constraints,
+		})
+	case *dsa.PrivateKey:
+		req = ssh.Marshal(dsaKeyMsg{
+			Type:        ssh.KeyAlgoDSA,
+			P:           k.P,
+			Q:           k.Q,
+			G:           k.G,
+			Y:           k.Y,
+			X:           k.X,
+			Comments:    comment,
+			Constraints: constraints,
+		})
+	case *ecdsa.PrivateKey:
+		nistID := fmt.Sprintf("nistp%d", k.Params().BitSize)
+		req = ssh.Marshal(ecdsaKeyMsg{
+			Type:        "ecdsa-sha2-" + nistID,
+			Curve:       nistID,
+			KeyBytes:    elliptic.Marshal(k.Curve, k.X, k.Y),
+			D:           k.D,
+			Comments:    comment,
+			Constraints: constraints,
+		})
+	default:
+		return fmt.Errorf("agent: unsupported key type %T", s)
+	}
+
+	// if constraints are present then the message type needs to be changed.
+	if len(constraints) != 0 {
+		req[0] = agentAddIdConstrained
+	}
+
+	resp, err := c.call(req)
+	if err != nil {
+		return err
+	}
+	if _, ok := resp.(*successAgentMsg); ok {
+		return nil
+	}
+	return errors.New("agent: failure")
+}
+
+type rsaCertMsg struct {
+	Type        string `sshtype:"17"`
+	CertBytes   []byte
+	D           *big.Int
+	Iqmp        *big.Int // IQMP = Inverse Q Mod P
+	P           *big.Int
+	Q           *big.Int
+	Comments    string
+	Constraints []byte `ssh:"rest"`
+}
+
+type dsaCertMsg struct {
+	Type        string `sshtype:"17"`
+	CertBytes   []byte
+	X           *big.Int
+	Comments    string
+	Constraints []byte `ssh:"rest"`
+}
+
+type ecdsaCertMsg struct {
+	Type        string `sshtype:"17"`
+	CertBytes   []byte
+	D           *big.Int
+	Comments    string
+	Constraints []byte `ssh:"rest"`
+}
+
+// Insert adds a private key to the agent. If a certificate is given,
+// that certificate is added instead as public key.
+func (c *client) Add(key AddedKey) error {
+	var constraints []byte
+
+	if secs := key.LifetimeSecs; secs != 0 {
+		constraints = append(constraints, agentConstrainLifetime)
+
+		var secsBytes [4]byte
+		binary.BigEndian.PutUint32(secsBytes[:], secs)
+		constraints = append(constraints, secsBytes[:]...)
+	}
+
+	if key.ConfirmBeforeUse {
+		constraints = append(constraints, agentConstrainConfirm)
+	}
+
+	if cert := key.Certificate; cert == nil {
+		return c.insertKey(key.PrivateKey, key.Comment, constraints)
+	} else {
+		return c.insertCert(key.PrivateKey, cert, key.Comment, constraints)
+	}
+}
+
+func (c *client) insertCert(s interface{}, cert *ssh.Certificate, comment string, constraints []byte) error {
+	var req []byte
+	switch k := s.(type) {
+	case *rsa.PrivateKey:
+		if len(k.Primes) != 2 {
+			return fmt.Errorf("agent: unsupported RSA key with %d primes", len(k.Primes))
+		}
+		k.Precompute()
+		req = ssh.Marshal(rsaCertMsg{
+			Type:        cert.Type(),
+			CertBytes:   cert.Marshal(),
+			D:           k.D,
+			Iqmp:        k.Precomputed.Qinv,
+			P:           k.Primes[0],
+			Q:           k.Primes[1],
+			Comments:    comment,
+			Constraints: constraints,
+		})
+	case *dsa.PrivateKey:
+		req = ssh.Marshal(dsaCertMsg{
+			Type:      cert.Type(),
+			CertBytes: cert.Marshal(),
+			X:         k.X,
+			Comments:  comment,
+		})
+	case *ecdsa.PrivateKey:
+		req = ssh.Marshal(ecdsaCertMsg{
+			Type:      cert.Type(),
+			CertBytes: cert.Marshal(),
+			D:         k.D,
+			Comments:  comment,
+		})
+	default:
+		return fmt.Errorf("agent: unsupported key type %T", s)
+	}
+
+	// if constraints are present then the message type needs to be changed.
+	if len(constraints) != 0 {
+		req[0] = agentAddIdConstrained
+	}
+
+	signer, err := ssh.NewSignerFromKey(s)
+	if err != nil {
+		return err
+	}
+	if bytes.Compare(cert.Key.Marshal(), signer.PublicKey().Marshal()) != 0 {
+		return errors.New("agent: signer and cert have different public key")
+	}
+
+	resp, err := c.call(req)
+	if err != nil {
+		return err
+	}
+	if _, ok := resp.(*successAgentMsg); ok {
+		return nil
+	}
+	return errors.New("agent: failure")
+}
+
+// Signers provides a callback for client authentication.
+func (c *client) Signers() ([]ssh.Signer, error) {
+	keys, err := c.List()
+	if err != nil {
+		return nil, err
+	}
+
+	var result []ssh.Signer
+	for _, k := range keys {
+		result = append(result, &agentKeyringSigner{c, k})
+	}
+	return result, nil
+}
+
+type agentKeyringSigner struct {
+	agent *client
+	pub   ssh.PublicKey
+}
+
+func (s *agentKeyringSigner) PublicKey() ssh.PublicKey {
+	return s.pub
+}
+
+func (s *agentKeyringSigner) Sign(rand io.Reader, data []byte) (*ssh.Signature, error) {
+	// The agent has its own entropy source, so the rand argument is ignored.
+	return s.agent.Sign(s.pub, data)
+}
diff --git a/modules/crypto/ssh/agent/client_test.go b/modules/crypto/ssh/agent/client_test.go
new file mode 100755
index 00000000..82b63515
--- /dev/null
+++ b/modules/crypto/ssh/agent/client_test.go
@@ -0,0 +1,287 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package agent
+
+import (
+	"bytes"
+	"crypto/rand"
+	"errors"
+	"net"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strconv"
+	"testing"
+
+	"github.com/gogits/gogs/modules/crypto/ssh"
+)
+
+// startAgent executes ssh-agent, and returns a Agent interface to it.
+func startAgent(t *testing.T) (client Agent, socket string, cleanup func()) {
+	if testing.Short() {
+		// ssh-agent is not always available, and the key
+		// types supported vary by platform.
+		t.Skip("skipping test due to -short")
+	}
+
+	bin, err := exec.LookPath("ssh-agent")
+	if err != nil {
+		t.Skip("could not find ssh-agent")
+	}
+
+	cmd := exec.Command(bin, "-s")
+	out, err := cmd.Output()
+	if err != nil {
+		t.Fatalf("cmd.Output: %v", err)
+	}
+
+	/* Output looks like:
+
+		   SSH_AUTH_SOCK=/tmp/ssh-P65gpcqArqvH/agent.15541; export SSH_AUTH_SOCK;
+	           SSH_AGENT_PID=15542; export SSH_AGENT_PID;
+	           echo Agent pid 15542;
+	*/
+	fields := bytes.Split(out, []byte(";"))
+	line := bytes.SplitN(fields[0], []byte("="), 2)
+	line[0] = bytes.TrimLeft(line[0], "\n")
+	if string(line[0]) != "SSH_AUTH_SOCK" {
+		t.Fatalf("could not find key SSH_AUTH_SOCK in %q", fields[0])
+	}
+	socket = string(line[1])
+
+	line = bytes.SplitN(fields[2], []byte("="), 2)
+	line[0] = bytes.TrimLeft(line[0], "\n")
+	if string(line[0]) != "SSH_AGENT_PID" {
+		t.Fatalf("could not find key SSH_AGENT_PID in %q", fields[2])
+	}
+	pidStr := line[1]
+	pid, err := strconv.Atoi(string(pidStr))
+	if err != nil {
+		t.Fatalf("Atoi(%q): %v", pidStr, err)
+	}
+
+	conn, err := net.Dial("unix", string(socket))
+	if err != nil {
+		t.Fatalf("net.Dial: %v", err)
+	}
+
+	ac := NewClient(conn)
+	return ac, socket, func() {
+		proc, _ := os.FindProcess(pid)
+		if proc != nil {
+			proc.Kill()
+		}
+		conn.Close()
+		os.RemoveAll(filepath.Dir(socket))
+	}
+}
+
+func testAgent(t *testing.T, key interface{}, cert *ssh.Certificate, lifetimeSecs uint32) {
+	agent, _, cleanup := startAgent(t)
+	defer cleanup()
+
+	testAgentInterface(t, agent, key, cert, lifetimeSecs)
+}
+
+func testAgentInterface(t *testing.T, agent Agent, key interface{}, cert *ssh.Certificate, lifetimeSecs uint32) {
+	signer, err := ssh.NewSignerFromKey(key)
+	if err != nil {
+		t.Fatalf("NewSignerFromKey(%T): %v", key, err)
+	}
+	// The agent should start up empty.
+	if keys, err := agent.List(); err != nil {
+		t.Fatalf("RequestIdentities: %v", err)
+	} else if len(keys) > 0 {
+		t.Fatalf("got %d keys, want 0: %v", len(keys), keys)
+	}
+
+	// Attempt to insert the key, with certificate if specified.
+	var pubKey ssh.PublicKey
+	if cert != nil {
+		err = agent.Add(AddedKey{
+			PrivateKey:   key,
+			Certificate:  cert,
+			Comment:      "comment",
+			LifetimeSecs: lifetimeSecs,
+		})
+		pubKey = cert
+	} else {
+		err = agent.Add(AddedKey{PrivateKey: key, Comment: "comment", LifetimeSecs: lifetimeSecs})
+		pubKey = signer.PublicKey()
+	}
+	if err != nil {
+		t.Fatalf("insert(%T): %v", key, err)
+	}
+
+	// Did the key get inserted successfully?
+	if keys, err := agent.List(); err != nil {
+		t.Fatalf("List: %v", err)
+	} else if len(keys) != 1 {
+		t.Fatalf("got %v, want 1 key", keys)
+	} else if keys[0].Comment != "comment" {
+		t.Fatalf("key comment: got %v, want %v", keys[0].Comment, "comment")
+	} else if !bytes.Equal(keys[0].Blob, pubKey.Marshal()) {
+		t.Fatalf("key mismatch")
+	}
+
+	// Can the agent make a valid signature?
+	data := []byte("hello")
+	sig, err := agent.Sign(pubKey, data)
+	if err != nil {
+		t.Fatalf("Sign(%s): %v", pubKey.Type(), err)
+	}
+
+	if err := pubKey.Verify(data, sig); err != nil {
+		t.Fatalf("Verify(%s): %v", pubKey.Type(), err)
+	}
+}
+
+func TestAgent(t *testing.T) {
+	for _, keyType := range []string{"rsa", "dsa", "ecdsa"} {
+		testAgent(t, testPrivateKeys[keyType], nil, 0)
+	}
+}
+
+func TestCert(t *testing.T) {
+	cert := &ssh.Certificate{
+		Key:         testPublicKeys["rsa"],
+		ValidBefore: ssh.CertTimeInfinity,
+		CertType:    ssh.UserCert,
+	}
+	cert.SignCert(rand.Reader, testSigners["ecdsa"])
+
+	testAgent(t, testPrivateKeys["rsa"], cert, 0)
+}
+
+func TestConstraints(t *testing.T) {
+	testAgent(t, testPrivateKeys["rsa"], nil, 3600 /* lifetime in seconds */)
+}
+
+// netPipe is analogous to net.Pipe, but it uses a real net.Conn, and
+// therefore is buffered (net.Pipe deadlocks if both sides start with
+// a write.)
+func netPipe() (net.Conn, net.Conn, error) {
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		return nil, nil, err
+	}
+	defer listener.Close()
+	c1, err := net.Dial("tcp", listener.Addr().String())
+	if err != nil {
+		return nil, nil, err
+	}
+
+	c2, err := listener.Accept()
+	if err != nil {
+		c1.Close()
+		return nil, nil, err
+	}
+
+	return c1, c2, nil
+}
+
+func TestAuth(t *testing.T) {
+	a, b, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+
+	defer a.Close()
+	defer b.Close()
+
+	agent, _, cleanup := startAgent(t)
+	defer cleanup()
+
+	if err := agent.Add(AddedKey{PrivateKey: testPrivateKeys["rsa"], Comment: "comment"}); err != nil {
+		t.Errorf("Add: %v", err)
+	}
+
+	serverConf := ssh.ServerConfig{}
+	serverConf.AddHostKey(testSigners["rsa"])
+	serverConf.PublicKeyCallback = func(c ssh.ConnMetadata, key ssh.PublicKey) (*ssh.Permissions, error) {
+		if bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+			return nil, nil
+		}
+
+		return nil, errors.New("pubkey rejected")
+	}
+
+	go func() {
+		conn, _, _, err := ssh.NewServerConn(a, &serverConf)
+		if err != nil {
+			t.Fatalf("Server: %v", err)
+		}
+		conn.Close()
+	}()
+
+	conf := ssh.ClientConfig{}
+	conf.Auth = append(conf.Auth, ssh.PublicKeysCallback(agent.Signers))
+	conn, _, _, err := ssh.NewClientConn(b, "", &conf)
+	if err != nil {
+		t.Fatalf("NewClientConn: %v", err)
+	}
+	conn.Close()
+}
+
+func TestLockClient(t *testing.T) {
+	agent, _, cleanup := startAgent(t)
+	defer cleanup()
+	testLockAgent(agent, t)
+}
+
+func testLockAgent(agent Agent, t *testing.T) {
+	if err := agent.Add(AddedKey{PrivateKey: testPrivateKeys["rsa"], Comment: "comment 1"}); err != nil {
+		t.Errorf("Add: %v", err)
+	}
+	if err := agent.Add(AddedKey{PrivateKey: testPrivateKeys["dsa"], Comment: "comment dsa"}); err != nil {
+		t.Errorf("Add: %v", err)
+	}
+	if keys, err := agent.List(); err != nil {
+		t.Errorf("List: %v", err)
+	} else if len(keys) != 2 {
+		t.Errorf("Want 2 keys, got %v", keys)
+	}
+
+	passphrase := []byte("secret")
+	if err := agent.Lock(passphrase); err != nil {
+		t.Errorf("Lock: %v", err)
+	}
+
+	if keys, err := agent.List(); err != nil {
+		t.Errorf("List: %v", err)
+	} else if len(keys) != 0 {
+		t.Errorf("Want 0 keys, got %v", keys)
+	}
+
+	signer, _ := ssh.NewSignerFromKey(testPrivateKeys["rsa"])
+	if _, err := agent.Sign(signer.PublicKey(), []byte("hello")); err == nil {
+		t.Fatalf("Sign did not fail")
+	}
+
+	if err := agent.Remove(signer.PublicKey()); err == nil {
+		t.Fatalf("Remove did not fail")
+	}
+
+	if err := agent.RemoveAll(); err == nil {
+		t.Fatalf("RemoveAll did not fail")
+	}
+
+	if err := agent.Unlock(nil); err == nil {
+		t.Errorf("Unlock with wrong passphrase succeeded")
+	}
+	if err := agent.Unlock(passphrase); err != nil {
+		t.Errorf("Unlock: %v", err)
+	}
+
+	if err := agent.Remove(signer.PublicKey()); err != nil {
+		t.Fatalf("Remove: %v", err)
+	}
+
+	if keys, err := agent.List(); err != nil {
+		t.Errorf("List: %v", err)
+	} else if len(keys) != 1 {
+		t.Errorf("Want 1 keys, got %v", keys)
+	}
+}
diff --git a/modules/crypto/ssh/agent/forward.go b/modules/crypto/ssh/agent/forward.go
new file mode 100755
index 00000000..8b54acb0
--- /dev/null
+++ b/modules/crypto/ssh/agent/forward.go
@@ -0,0 +1,103 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package agent
+
+import (
+	"errors"
+	"io"
+	"net"
+	"sync"
+
+	"github.com/gogits/gogs/modules/crypto/ssh"
+)
+
+// RequestAgentForwarding sets up agent forwarding for the session.
+// ForwardToAgent or ForwardToRemote should be called to route
+// the authentication requests.
+func RequestAgentForwarding(session *ssh.Session) error {
+	ok, err := session.SendRequest("auth-agent-req@openssh.com", true, nil)
+	if err != nil {
+		return err
+	}
+	if !ok {
+		return errors.New("forwarding request denied")
+	}
+	return nil
+}
+
+// ForwardToAgent routes authentication requests to the given keyring.
+func ForwardToAgent(client *ssh.Client, keyring Agent) error {
+	channels := client.HandleChannelOpen(channelType)
+	if channels == nil {
+		return errors.New("agent: already have handler for " + channelType)
+	}
+
+	go func() {
+		for ch := range channels {
+			channel, reqs, err := ch.Accept()
+			if err != nil {
+				continue
+			}
+			go ssh.DiscardRequests(reqs)
+			go func() {
+				ServeAgent(keyring, channel)
+				channel.Close()
+			}()
+		}
+	}()
+	return nil
+}
+
+const channelType = "auth-agent@openssh.com"
+
+// ForwardToRemote routes authentication requests to the ssh-agent
+// process serving on the given unix socket.
+func ForwardToRemote(client *ssh.Client, addr string) error {
+	channels := client.HandleChannelOpen(channelType)
+	if channels == nil {
+		return errors.New("agent: already have handler for " + channelType)
+	}
+	conn, err := net.Dial("unix", addr)
+	if err != nil {
+		return err
+	}
+	conn.Close()
+
+	go func() {
+		for ch := range channels {
+			channel, reqs, err := ch.Accept()
+			if err != nil {
+				continue
+			}
+			go ssh.DiscardRequests(reqs)
+			go forwardUnixSocket(channel, addr)
+		}
+	}()
+	return nil
+}
+
+func forwardUnixSocket(channel ssh.Channel, addr string) {
+	conn, err := net.Dial("unix", addr)
+	if err != nil {
+		return
+	}
+
+	var wg sync.WaitGroup
+	wg.Add(2)
+	go func() {
+		io.Copy(conn, channel)
+		conn.(*net.UnixConn).CloseWrite()
+		wg.Done()
+	}()
+	go func() {
+		io.Copy(channel, conn)
+		channel.CloseWrite()
+		wg.Done()
+	}()
+
+	wg.Wait()
+	conn.Close()
+	channel.Close()
+}
diff --git a/modules/crypto/ssh/agent/keyring.go b/modules/crypto/ssh/agent/keyring.go
new file mode 100755
index 00000000..e27c2c94
--- /dev/null
+++ b/modules/crypto/ssh/agent/keyring.go
@@ -0,0 +1,184 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package agent
+
+import (
+	"bytes"
+	"crypto/rand"
+	"crypto/subtle"
+	"errors"
+	"fmt"
+	"sync"
+
+	"github.com/gogits/gogs/modules/crypto/ssh"
+)
+
+type privKey struct {
+	signer  ssh.Signer
+	comment string
+}
+
+type keyring struct {
+	mu   sync.Mutex
+	keys []privKey
+
+	locked     bool
+	passphrase []byte
+}
+
+var errLocked = errors.New("agent: locked")
+
+// NewKeyring returns an Agent that holds keys in memory.  It is safe
+// for concurrent use by multiple goroutines.
+func NewKeyring() Agent {
+	return &keyring{}
+}
+
+// RemoveAll removes all identities.
+func (r *keyring) RemoveAll() error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if r.locked {
+		return errLocked
+	}
+
+	r.keys = nil
+	return nil
+}
+
+// Remove removes all identities with the given public key.
+func (r *keyring) Remove(key ssh.PublicKey) error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if r.locked {
+		return errLocked
+	}
+
+	want := key.Marshal()
+	found := false
+	for i := 0; i < len(r.keys); {
+		if bytes.Equal(r.keys[i].signer.PublicKey().Marshal(), want) {
+			found = true
+			r.keys[i] = r.keys[len(r.keys)-1]
+			r.keys = r.keys[len(r.keys)-1:]
+			continue
+		} else {
+			i++
+		}
+	}
+
+	if !found {
+		return errors.New("agent: key not found")
+	}
+	return nil
+}
+
+// Lock locks the agent. Sign and Remove will fail, and List will empty an empty list.
+func (r *keyring) Lock(passphrase []byte) error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if r.locked {
+		return errLocked
+	}
+
+	r.locked = true
+	r.passphrase = passphrase
+	return nil
+}
+
+// Unlock undoes the effect of Lock
+func (r *keyring) Unlock(passphrase []byte) error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if !r.locked {
+		return errors.New("agent: not locked")
+	}
+	if len(passphrase) != len(r.passphrase) || 1 != subtle.ConstantTimeCompare(passphrase, r.passphrase) {
+		return fmt.Errorf("agent: incorrect passphrase")
+	}
+
+	r.locked = false
+	r.passphrase = nil
+	return nil
+}
+
+// List returns the identities known to the agent.
+func (r *keyring) List() ([]*Key, error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if r.locked {
+		// section 2.7: locked agents return empty.
+		return nil, nil
+	}
+
+	var ids []*Key
+	for _, k := range r.keys {
+		pub := k.signer.PublicKey()
+		ids = append(ids, &Key{
+			Format:  pub.Type(),
+			Blob:    pub.Marshal(),
+			Comment: k.comment})
+	}
+	return ids, nil
+}
+
+// Insert adds a private key to the keyring. If a certificate
+// is given, that certificate is added as public key. Note that
+// any constraints given are ignored.
+func (r *keyring) Add(key AddedKey) error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if r.locked {
+		return errLocked
+	}
+	signer, err := ssh.NewSignerFromKey(key.PrivateKey)
+
+	if err != nil {
+		return err
+	}
+
+	if cert := key.Certificate; cert != nil {
+		signer, err = ssh.NewCertSigner(cert, signer)
+		if err != nil {
+			return err
+		}
+	}
+
+	r.keys = append(r.keys, privKey{signer, key.Comment})
+
+	return nil
+}
+
+// Sign returns a signature for the data.
+func (r *keyring) Sign(key ssh.PublicKey, data []byte) (*ssh.Signature, error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if r.locked {
+		return nil, errLocked
+	}
+
+	wanted := key.Marshal()
+	for _, k := range r.keys {
+		if bytes.Equal(k.signer.PublicKey().Marshal(), wanted) {
+			return k.signer.Sign(rand.Reader, data)
+		}
+	}
+	return nil, errors.New("not found")
+}
+
+// Signers returns signers for all the known keys.
+func (r *keyring) Signers() ([]ssh.Signer, error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if r.locked {
+		return nil, errLocked
+	}
+
+	s := make([]ssh.Signer, 0, len(r.keys))
+	for _, k := range r.keys {
+		s = append(s, k.signer)
+	}
+	return s, nil
+}
diff --git a/modules/crypto/ssh/agent/server.go b/modules/crypto/ssh/agent/server.go
new file mode 100755
index 00000000..71ec3bc0
--- /dev/null
+++ b/modules/crypto/ssh/agent/server.go
@@ -0,0 +1,209 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package agent
+
+import (
+	"crypto/rsa"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"log"
+	"math/big"
+
+	"github.com/gogits/gogs/modules/crypto/ssh"
+)
+
+// Server wraps an Agent and uses it to implement the agent side of
+// the SSH-agent, wire protocol.
+type server struct {
+	agent Agent
+}
+
+func (s *server) processRequestBytes(reqData []byte) []byte {
+	rep, err := s.processRequest(reqData)
+	if err != nil {
+		if err != errLocked {
+			// TODO(hanwen): provide better logging interface?
+			log.Printf("agent %d: %v", reqData[0], err)
+		}
+		return []byte{agentFailure}
+	}
+
+	if err == nil && rep == nil {
+		return []byte{agentSuccess}
+	}
+
+	return ssh.Marshal(rep)
+}
+
+func marshalKey(k *Key) []byte {
+	var record struct {
+		Blob    []byte
+		Comment string
+	}
+	record.Blob = k.Marshal()
+	record.Comment = k.Comment
+
+	return ssh.Marshal(&record)
+}
+
+type agentV1IdentityMsg struct {
+	Numkeys uint32 `sshtype:"2"`
+}
+
+type agentRemoveIdentityMsg struct {
+	KeyBlob []byte `sshtype:"18"`
+}
+
+type agentLockMsg struct {
+	Passphrase []byte `sshtype:"22"`
+}
+
+type agentUnlockMsg struct {
+	Passphrase []byte `sshtype:"23"`
+}
+
+func (s *server) processRequest(data []byte) (interface{}, error) {
+	switch data[0] {
+	case agentRequestV1Identities:
+		return &agentV1IdentityMsg{0}, nil
+	case agentRemoveIdentity:
+		var req agentRemoveIdentityMsg
+		if err := ssh.Unmarshal(data, &req); err != nil {
+			return nil, err
+		}
+
+		var wk wireKey
+		if err := ssh.Unmarshal(req.KeyBlob, &wk); err != nil {
+			return nil, err
+		}
+
+		return nil, s.agent.Remove(&Key{Format: wk.Format, Blob: req.KeyBlob})
+
+	case agentRemoveAllIdentities:
+		return nil, s.agent.RemoveAll()
+
+	case agentLock:
+		var req agentLockMsg
+		if err := ssh.Unmarshal(data, &req); err != nil {
+			return nil, err
+		}
+
+		return nil, s.agent.Lock(req.Passphrase)
+
+	case agentUnlock:
+		var req agentLockMsg
+		if err := ssh.Unmarshal(data, &req); err != nil {
+			return nil, err
+		}
+		return nil, s.agent.Unlock(req.Passphrase)
+
+	case agentSignRequest:
+		var req signRequestAgentMsg
+		if err := ssh.Unmarshal(data, &req); err != nil {
+			return nil, err
+		}
+
+		var wk wireKey
+		if err := ssh.Unmarshal(req.KeyBlob, &wk); err != nil {
+			return nil, err
+		}
+
+		k := &Key{
+			Format: wk.Format,
+			Blob:   req.KeyBlob,
+		}
+
+		sig, err := s.agent.Sign(k, req.Data) //  TODO(hanwen): flags.
+		if err != nil {
+			return nil, err
+		}
+		return &signResponseAgentMsg{SigBlob: ssh.Marshal(sig)}, nil
+	case agentRequestIdentities:
+		keys, err := s.agent.List()
+		if err != nil {
+			return nil, err
+		}
+
+		rep := identitiesAnswerAgentMsg{
+			NumKeys: uint32(len(keys)),
+		}
+		for _, k := range keys {
+			rep.Keys = append(rep.Keys, marshalKey(k)...)
+		}
+		return rep, nil
+	case agentAddIdentity:
+		return nil, s.insertIdentity(data)
+	}
+
+	return nil, fmt.Errorf("unknown opcode %d", data[0])
+}
+
+func (s *server) insertIdentity(req []byte) error {
+	var record struct {
+		Type string `sshtype:"17"`
+		Rest []byte `ssh:"rest"`
+	}
+	if err := ssh.Unmarshal(req, &record); err != nil {
+		return err
+	}
+
+	switch record.Type {
+	case ssh.KeyAlgoRSA:
+		var k rsaKeyMsg
+		if err := ssh.Unmarshal(req, &k); err != nil {
+			return err
+		}
+
+		priv := rsa.PrivateKey{
+			PublicKey: rsa.PublicKey{
+				E: int(k.E.Int64()),
+				N: k.N,
+			},
+			D:      k.D,
+			Primes: []*big.Int{k.P, k.Q},
+		}
+		priv.Precompute()
+
+		return s.agent.Add(AddedKey{PrivateKey: &priv, Comment: k.Comments})
+	}
+	return fmt.Errorf("not implemented: %s", record.Type)
+}
+
+// ServeAgent serves the agent protocol on the given connection. It
+// returns when an I/O error occurs.
+func ServeAgent(agent Agent, c io.ReadWriter) error {
+	s := &server{agent}
+
+	var length [4]byte
+	for {
+		if _, err := io.ReadFull(c, length[:]); err != nil {
+			return err
+		}
+		l := binary.BigEndian.Uint32(length[:])
+		if l > maxAgentResponseBytes {
+			// We also cap requests.
+			return fmt.Errorf("agent: request too large: %d", l)
+		}
+
+		req := make([]byte, l)
+		if _, err := io.ReadFull(c, req); err != nil {
+			return err
+		}
+
+		repData := s.processRequestBytes(req)
+		if len(repData) > maxAgentResponseBytes {
+			return fmt.Errorf("agent: reply too large: %d bytes", len(repData))
+		}
+
+		binary.BigEndian.PutUint32(length[:], uint32(len(repData)))
+		if _, err := c.Write(length[:]); err != nil {
+			return err
+		}
+		if _, err := c.Write(repData); err != nil {
+			return err
+		}
+	}
+}
diff --git a/modules/crypto/ssh/agent/server_test.go b/modules/crypto/ssh/agent/server_test.go
new file mode 100755
index 00000000..7f257bcf
--- /dev/null
+++ b/modules/crypto/ssh/agent/server_test.go
@@ -0,0 +1,77 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package agent
+
+import (
+	"testing"
+
+	"github.com/gogits/gogs/modules/crypto/ssh"
+)
+
+func TestServer(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+	client := NewClient(c1)
+
+	go ServeAgent(NewKeyring(), c2)
+
+	testAgentInterface(t, client, testPrivateKeys["rsa"], nil, 0)
+}
+
+func TestLockServer(t *testing.T) {
+	testLockAgent(NewKeyring(), t)
+}
+
+func TestSetupForwardAgent(t *testing.T) {
+	a, b, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+
+	defer a.Close()
+	defer b.Close()
+
+	_, socket, cleanup := startAgent(t)
+	defer cleanup()
+
+	serverConf := ssh.ServerConfig{
+		NoClientAuth: true,
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+	incoming := make(chan *ssh.ServerConn, 1)
+	go func() {
+		conn, _, _, err := ssh.NewServerConn(a, &serverConf)
+		if err != nil {
+			t.Fatalf("Server: %v", err)
+		}
+		incoming <- conn
+	}()
+
+	conf := ssh.ClientConfig{}
+	conn, chans, reqs, err := ssh.NewClientConn(b, "", &conf)
+	if err != nil {
+		t.Fatalf("NewClientConn: %v", err)
+	}
+	client := ssh.NewClient(conn, chans, reqs)
+
+	if err := ForwardToRemote(client, socket); err != nil {
+		t.Fatalf("SetupForwardAgent: %v", err)
+	}
+
+	server := <-incoming
+	ch, reqs, err := server.OpenChannel(channelType, nil)
+	if err != nil {
+		t.Fatalf("OpenChannel(%q): %v", channelType, err)
+	}
+	go ssh.DiscardRequests(reqs)
+
+	agentClient := NewClient(ch)
+	testAgentInterface(t, agentClient, testPrivateKeys["rsa"], nil, 0)
+	conn.Close()
+}
diff --git a/modules/crypto/ssh/agent/testdata_test.go b/modules/crypto/ssh/agent/testdata_test.go
new file mode 100755
index 00000000..18dcde29
--- /dev/null
+++ b/modules/crypto/ssh/agent/testdata_test.go
@@ -0,0 +1,64 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// IMPLEMENTOR NOTE: To avoid a package loop, this file is in three places:
+// ssh/, ssh/agent, and ssh/test/. It should be kept in sync across all three
+// instances.
+
+package agent
+
+import (
+	"crypto/rand"
+	"fmt"
+
+	"github.com/gogits/gogs/modules/crypto/ssh"
+	"github.com/gogits/gogs/modules/crypto/ssh/testdata"
+)
+
+var (
+	testPrivateKeys map[string]interface{}
+	testSigners     map[string]ssh.Signer
+	testPublicKeys  map[string]ssh.PublicKey
+)
+
+func init() {
+	var err error
+
+	n := len(testdata.PEMBytes)
+	testPrivateKeys = make(map[string]interface{}, n)
+	testSigners = make(map[string]ssh.Signer, n)
+	testPublicKeys = make(map[string]ssh.PublicKey, n)
+	for t, k := range testdata.PEMBytes {
+		testPrivateKeys[t], err = ssh.ParseRawPrivateKey(k)
+		if err != nil {
+			panic(fmt.Sprintf("Unable to parse test key %s: %v", t, err))
+		}
+		testSigners[t], err = ssh.NewSignerFromKey(testPrivateKeys[t])
+		if err != nil {
+			panic(fmt.Sprintf("Unable to create signer for test key %s: %v", t, err))
+		}
+		testPublicKeys[t] = testSigners[t].PublicKey()
+	}
+
+	// Create a cert and sign it for use in tests.
+	testCert := &ssh.Certificate{
+		Nonce:           []byte{},                       // To pass reflect.DeepEqual after marshal & parse, this must be non-nil
+		ValidPrincipals: []string{"gopher1", "gopher2"}, // increases test coverage
+		ValidAfter:      0,                              // unix epoch
+		ValidBefore:     ssh.CertTimeInfinity,           // The end of currently representable time.
+		Reserved:        []byte{},                       // To pass reflect.DeepEqual after marshal & parse, this must be non-nil
+		Key:             testPublicKeys["ecdsa"],
+		SignatureKey:    testPublicKeys["rsa"],
+		Permissions: ssh.Permissions{
+			CriticalOptions: map[string]string{},
+			Extensions:      map[string]string{},
+		},
+	}
+	testCert.SignCert(rand.Reader, testSigners["rsa"])
+	testPrivateKeys["cert"] = testPrivateKeys["ecdsa"]
+	testSigners["cert"], err = ssh.NewCertSigner(testCert, testSigners["ecdsa"])
+	if err != nil {
+		panic(fmt.Sprintf("Unable to create certificate signer: %v", err))
+	}
+}