From 2086ca4652999724e0f5e1281c8ae9a67ccbb6b5 Mon Sep 17 00:00:00 2001
From: Boshi Lian <farmer1992@gmail.com>
Date: Thu, 27 Dec 2018 01:08:38 +0000
Subject: [PATCH] add fallback user for working dir

---
 sshpiperd/upstream/workingdir/config.go         |  1 +
 sshpiperd/upstream/workingdir/workingdir.go     | 12 ++++++++++--
 .../upstream/workingdir/workingdir_test.go      | 17 +++++++++++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/sshpiperd/upstream/workingdir/config.go b/sshpiperd/upstream/workingdir/config.go
index 0aa9bc8e..a8a7fe98 100644
--- a/sshpiperd/upstream/workingdir/config.go
+++ b/sshpiperd/upstream/workingdir/config.go
@@ -5,5 +5,6 @@ var (
 		WorkingDir       string `long:"workingdir" default:"/var/sshpiper" description:"Path to workingdir" env:"SSHPIPERD_WORKINGDIR" ini-name:"workingdir"`
 		AllowBadUsername bool   `long:"workingdir-allowbadusername" description:"Disable username check while search the working dir" env:"SSHPIPERD_WORKINGDIR_ALLOWBADUSERNAME" ini-name:"workingdir-allowbadusername"`
 		NoCheckPerm      bool   `long:"workingdir-nocheckperm" description:"Disable 0400 checking when using files in the working dir" env:"SSHPIPERD_WORKINGDIR_NOCHECKPERM" ini-name:"workingdir-nocheckperm"`
+		FallbackUSername string `long:"workingdir-fallbackusername" description:"Fallback to a user when user does not exists in directory" env:"SSHPIPERD_WORKINGDIR_FALLBACKUSERNAME" ini-name:"workingdir-fallbackusername"`
 	}{}
 )
diff --git a/sshpiperd/upstream/workingdir/workingdir.go b/sshpiperd/upstream/workingdir/workingdir.go
index accf7c4d..f251d64f 100644
--- a/sshpiperd/upstream/workingdir/workingdir.go
+++ b/sshpiperd/upstream/workingdir/workingdir.go
@@ -130,7 +130,11 @@ func findUpstreamFromUserfile(conn ssh.ConnMetadata) (net.Conn, *ssh.AuthPipe, e
 	}
 
 	err := userUpstreamFile.checkPerm(user)
-	if err != nil {
+
+	if os.IsNotExist(err) && len(config.FallbackUSername) > 0 {
+		err = nil
+		user = config.FallbackUSername
+	} else if err != nil {
 		return nil, nil, err
 	}
 
@@ -184,7 +188,11 @@ func mapPublicKeyFromUserfile(conn ssh.ConnMetadata, key ssh.PublicKey) (signer
 	}()
 
 	err = userAuthorizedKeysFile.checkPerm(user)
-	if err != nil {
+
+	if os.IsNotExist(err) && len(config.FallbackUSername) > 0 {
+		err = nil
+		user = config.FallbackUSername
+	} else if err != nil {
 		return nil, err
 	}
 
diff --git a/sshpiperd/upstream/workingdir/workingdir_test.go b/sshpiperd/upstream/workingdir/workingdir_test.go
index e869f279..804d5087 100644
--- a/sshpiperd/upstream/workingdir/workingdir_test.go
+++ b/sshpiperd/upstream/workingdir/workingdir_test.go
@@ -243,10 +243,19 @@ func TestFindUpstreamFromUserfile(t *testing.T) {
 	}
 
 	t.Logf("testing user not found")
+	config.FallbackUSername = ""
 	_, _, err = findUpstreamFromUserfile(stubConnMetadata{"nosuchuser"})
 	if err == nil {
 		t.Fatalf("should return err when finding nosuchuser")
 	}
+
+	t.Logf("testing user not found fallback")
+	config.FallbackUSername = user
+	_, _, err = findUpstreamFromUserfile(stubConnMetadata{"nosuchuser"})
+
+	if err != nil {
+		t.Fatalf("should return fallbackuser")
+	}
 }
 
 func TestMapPublicKeyFromUserfile(t *testing.T) {
@@ -296,11 +305,19 @@ func TestMapPublicKeyFromUserfile(t *testing.T) {
 	}
 
 	t.Logf("testing user not found")
+	config.FallbackUSername = ""
 	_, err = mapPublicKeyFromUserfile(stubConnMetadata{"nosuchuser"}, publicKey)
 	if err == nil {
 		t.Fatalf("should return err when mapping from nosuchuser")
 	}
 
+	t.Logf("testing user not found fallback")
+	config.FallbackUSername = user
+	_, err = mapPublicKeyFromUserfile(stubConnMetadata{"nosuchuser"}, publicKey)
+	if err != nil {
+		t.Fatalf("should return fallbackuser")
+	}
+
 	t.Logf("testing mapping signer")
 	signer, err := mapPublicKeyFromUserfile(stubConnMetadata{user}, privateKey.PublicKey())
 	if err != nil {