plumbing/transport: git, error on empty SSH_AUTH_SOCK

2 files changed, 26 insertions, 3 deletions

diff --git a/plumbing/transport/ssh/auth_method.go b/plumbing/transport/ssh/auth_method.go
index 9c3d6f3..f53e510 100644
--- a/plumbing/transport/ssh/auth_method.go
+++ b/plumbing/transport/ssh/auth_method.go
@@ -1,6 +1,7 @@
 package ssh
 
 import (
+	"errors"
 	"fmt"
 	"net"
 	"os"
@@ -9,6 +10,8 @@ import (
 	"golang.org/x/crypto/ssh/agent"
 )
 
+var ErrEmptySSHAgentAddr = errors.New("SSH_AUTH_SOCK env variable is required")
+
 // 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.
@@ -138,16 +141,21 @@ func (a *PublicKeysCallback) clientConfig() *ssh.ClientConfig {
 
 const DefaultSSHUsername = "git"
 
-// Opens a pipe with the ssh agent and uses the pipe
+// NewSSHAgentAuth 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"))
+	sshAgentAddr := os.Getenv("SSH_AUTH_SOCK")
+	if sshAgentAddr == "" {
+		return nil, ErrEmptySSHAgentAddr
+	}
+
+	pipe, err := net.Dial("unix", sshAgentAddr)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("error connecting to SSH agent: %q", err)
 	}
 
 	return &PublicKeysCallback{
diff --git a/plumbing/transport/ssh/auth_method_test.go b/plumbing/transport/ssh/auth_method_test.go
index f9e7dec..412e721 100644
--- a/plumbing/transport/ssh/auth_method_test.go
+++ b/plumbing/transport/ssh/auth_method_test.go
@@ -2,6 +2,7 @@ package ssh
 
 import (
 	"fmt"
+	"os"
 
 	. "gopkg.in/check.v1"
 )
@@ -89,3 +90,17 @@ func (s *SuiteCommon) TestPublicKeysCallbackString(c *C) {
 	}
 	c.Assert(a.String(), Equals, fmt.Sprintf("user: test, name: %s", PublicKeysCallbackName))
 }
+func (s *SuiteCommon) TestNewSSHAgentAuth(c *C) {
+	addr := os.Getenv("SSH_AUTH_SOCK")
+	err := os.Unsetenv("SSH_AUTH_SOCK")
+	c.Assert(err, IsNil)
+
+	defer func() {
+		err := os.Setenv("SSH_AUTH_SOCK", addr)
+		c.Assert(err, IsNil)
+	}()
+
+	k, err := NewSSHAgentAuth("foo")
+	c.Assert(k, IsNil)
+	c.Assert(err, Equals, ErrEmptySSHAgentAddr)
+}