sftpd: add support for some SSH commands

md5sum, sha1sum are used by rclone.
cd, pwd improve the support for RemoteFiles mobile app.

These commands are all implemented inside SFTPGo so they work even
if the matching system commands are not available, for example on Windows

sftpd/internal_test.go

@@ -8,6 +8,7 @@ import (
 	"net"
 	"os"
 	"runtime"
+	"strings"
 	"testing"
 	"time"
 
@@ -240,6 +241,107 @@ func TestSFTPGetUsedQuota(t *testing.T) {
 	}
 }
 
+func TestSupportedSSHCommands(t *testing.T) {
+	cmds := GetSupportedSSHCommands()
+	if len(cmds) != len(supportedSSHCommands) {
+		t.Errorf("supported ssh commands does not match")
+	}
+	for _, c := range cmds {
+		if !utils.IsStringInSlice(c, supportedSSHCommands) {
+			t.Errorf("invalid ssh command: %v", c)
+		}
+	}
+}
+
+func TestSSHCommandPath(t *testing.T) {
+	buf := make([]byte, 65535)
+	stdErrBuf := make([]byte, 65535)
+	mockSSHChannel := MockChannel{
+		Buffer:       bytes.NewBuffer(buf),
+		StdErrBuffer: bytes.NewBuffer(stdErrBuf),
+		ReadError:    nil,
+	}
+	connection := Connection{
+		channel: &mockSSHChannel,
+	}
+	sshCommand := sshCommand{
+		command:    "test",
+		connection: connection,
+		args:       []string{},
+	}
+	path := sshCommand.getDestPath()
+	if path != "" {
+		t.Errorf("path must be empty")
+	}
+	sshCommand.args = []string{"-t", "/tmp/../path"}
+	path = sshCommand.getDestPath()
+	if path != "/path" {
+		t.Errorf("unexpected path: %v", path)
+	}
+	sshCommand.args = []string{"-t", "/tmp/"}
+	path = sshCommand.getDestPath()
+	if path != "/tmp/" {
+		t.Errorf("unexpected path: %v", path)
+	}
+	sshCommand.args = []string{"-t", "tmp/"}
+	path = sshCommand.getDestPath()
+	if path != "/tmp/" {
+		t.Errorf("unexpected path: %v", path)
+	}
+}
+
+func TestSSHCommandErrors(t *testing.T) {
+	buf := make([]byte, 65535)
+	stdErrBuf := make([]byte, 65535)
+	readErr := fmt.Errorf("test read error")
+	mockSSHChannel := MockChannel{
+		Buffer:       bytes.NewBuffer(buf),
+		StdErrBuffer: bytes.NewBuffer(stdErrBuf),
+		ReadError:    readErr,
+	}
+	server, client := net.Pipe()
+	defer server.Close()
+	defer client.Close()
+	connection := Connection{
+		channel: &mockSSHChannel,
+		netConn: client,
+	}
+	cmd := sshCommand{
+		command:    "md5sum",
+		connection: connection,
+		args:       []string{},
+	}
+	err := cmd.handle()
+	if err == nil {
+		t.Errorf("ssh command must fail, we are sending a fake error")
+	}
+	cmd = sshCommand{
+		command:    "md5sum",
+		connection: connection,
+		args:       []string{"/../../test_file.dat"},
+	}
+	err = cmd.handle()
+	if err == nil {
+		t.Errorf("ssh command must fail, we are requesting an invalid path")
+	}
+}
+
+func TestGetConnectionInfo(t *testing.T) {
+	c := ConnectionStatus{
+		Username:      "test_user",
+		ConnectionID:  "123",
+		ClientVersion: "client",
+		RemoteAddress: "127.0.0.1:1234",
+		Protocol:      protocolSSH,
+		SSHCommand:    "sha1sum /test_file.dat",
+	}
+	info := c.GetConnectionInfo()
+	if !strings.Contains(info, "sha1sum /test_file.dat") {
+		t.Errorf("ssh command not found in connection info")
+	}
+
+}
+
 func TestSCPFileMode(t *testing.T) {
 	mode := getFileModeAsString(0, true)
 	if mode != "0755" {
@@ -316,8 +418,11 @@ func TestSCPParseUploadMessage(t *testing.T) {
 		channel: &mockSSHChannel,
 	}
 	scpCommand := scpCommand{
-		connection: connection,
-		args:       []string{"-t", "/tmp"},
+		sshCommand: sshCommand{
+			command:    "scp",
+			connection: connection,
+			args:       []string{"-t", "/tmp"},
+		},
 	}
 	_, _, err := scpCommand.parseUploadMessage("invalid")
 	if err == nil {
@@ -352,8 +457,11 @@ func TestSCPProtocolMessages(t *testing.T) {
 		channel: &mockSSHChannel,
 	}
 	scpCommand := scpCommand{
-		connection: connection,
-		args:       []string{"-t", "/tmp"},
+		sshCommand: sshCommand{
+			command:    "scp",
+			connection: connection,
+			args:       []string{"-t", "/tmp"},
+		},
 	}
 	_, err := scpCommand.readProtocolMessage()
 	if err == nil || err != readErr {
@@ -414,8 +522,11 @@ func TestSCPTestDownloadProtocolMessages(t *testing.T) {
 		channel: &mockSSHChannel,
 	}
 	scpCommand := scpCommand{
-		connection: connection,
-		args:       []string{"-f", "-p", "/tmp"},
+		sshCommand: sshCommand{
+			command:    "scp",
+			connection: connection,
+			args:       []string{"-f", "-p", "/tmp"},
+		},
 	}
 	path := "testDir"
 	os.Mkdir(path, 0777)
@@ -483,8 +594,11 @@ func TestSCPCommandHandleErrors(t *testing.T) {
 		netConn: client,
 	}
 	scpCommand := scpCommand{
-		connection: connection,
-		args:       []string{"-f", "/tmp"},
+		sshCommand: sshCommand{
+			command:    "scp",
+			connection: connection,
+			args:       []string{"-f", "/tmp"},
+		},
 	}
 	err := scpCommand.handle()
 	if err == nil || err != readErr {
@@ -516,8 +630,11 @@ func TestSCPRecursiveDownloadErrors(t *testing.T) {
 		netConn: client,
 	}
 	scpCommand := scpCommand{
-		connection: connection,
-		args:       []string{"-r", "-f", "/tmp"},
+		sshCommand: sshCommand{
+			command:    "scp",
+			connection: connection,
+			args:       []string{"-r", "-f", "/tmp"},
+		},
 	}
 	path := "testDir"
 	os.Mkdir(path, 0777)
@@ -556,8 +673,11 @@ func TestSCPRecursiveUploadErrors(t *testing.T) {
 		channel: &mockSSHChannel,
 	}
 	scpCommand := scpCommand{
-		connection: connection,
-		args:       []string{"-r", "-t", "/tmp"},
+		sshCommand: sshCommand{
+			command:    "scp",
+			connection: connection,
+			args:       []string{"-r", "-t", "/tmp"},
+		},
 	}
 	err := scpCommand.handleRecursiveUpload()
 	if err == nil {
@@ -594,8 +714,11 @@ func TestSCPCreateDirs(t *testing.T) {
 		channel: &mockSSHChannel,
 	}
 	scpCommand := scpCommand{
-		connection: connection,
-		args:       []string{"-r", "-t", "/tmp"},
+		sshCommand: sshCommand{
+			command:    "scp",
+			connection: connection,
+			args:       []string{"-r", "-t", "/tmp"},
+		},
 	}
 	err := scpCommand.handleCreateDir("invalid_dir")
 	if err == nil {
@@ -625,8 +748,11 @@ func TestSCPDownloadFileData(t *testing.T) {
 		channel: &mockSSHChannelReadErr,
 	}
 	scpCommand := scpCommand{
-		connection: connection,
-		args:       []string{"-r", "-f", "/tmp"},
+		sshCommand: sshCommand{
+			command:    "scp",
+			connection: connection,
+			args:       []string{"-r", "-f", "/tmp"},
+		},
 	}
 	ioutil.WriteFile(testfile, []byte("test"), 0666)
 	stat, _ := os.Stat(testfile)
@@ -672,8 +798,11 @@ func TestSCPUploadFiledata(t *testing.T) {
 		channel:  &mockSSHChannel,
 	}
 	scpCommand := scpCommand{
-		connection: connection,
-		args:       []string{"-r", "-t", "/tmp"},
+		sshCommand: sshCommand{
+			command:    "scp",
+			connection: connection,
+			args:       []string{"-r", "-t", "/tmp"},
+		},
 	}
 	file, _ := os.Create(testfile)
 	transfer := Transfer{