add SCP support

SCP is an experimental feature, we have our own SCP implementation
since we can't rely on scp system command to proper handle permissions,
quota and user's home dir restrictions. The SCP protocol is quite simple
but there is no official docs about it, so we need more testing and
feedbacks before enabling it by default.
We may not handle some borderline cases or have sneaky bugs.

This commit contains some breaking changes to the REST API.
SFTPGo API should be stable now and I hope no more breaking changes
before the first stable release.

sftpd/sftpd.go

@@ -19,18 +19,21 @@ import (
 )
 
 const (
-	logSender              = "sftpd"
-	sftpUploadLogSender    = "SFTPUpload"
-	sftpdDownloadLogSender = "SFTPDownload"
-	sftpdRenameLogSender   = "SFTPRename"
-	sftpdRmdirLogSender    = "SFTPRmdir"
-	sftpdMkdirLogSender    = "SFTPMkdir"
-	sftpdSymlinkLogSender  = "SFTPSymlink"
-	sftpdRemoveLogSender   = "SFTPRemove"
-	operationDownload      = "download"
-	operationUpload        = "upload"
-	operationDelete        = "delete"
-	operationRename        = "rename"
+	logSender         = "sftpd"
+	logSenderSCP      = "scp"
+	uploadLogSender   = "Upload"
+	downloadLogSender = "Download"
+	renameLogSender   = "Rename"
+	rmdirLogSender    = "Rmdir"
+	mkdirLogSender    = "Mkdir"
+	symlinkLogSender  = "Symlink"
+	removeLogSender   = "Remove"
+	operationDownload = "download"
+	operationUpload   = "upload"
+	operationDelete   = "delete"
+	operationRename   = "rename"
+	protocolSFTP      = "SFTP"
+	protocolSCP       = "SCP"
 )
 
 var (
@@ -86,6 +89,8 @@ type ConnectionStatus struct {
 	ConnectionTime int64 `json:"connection_time"`
 	// Last activity as unix timestamp in milliseconds
 	LastActivity int64 `json:"last_activity"`
+	// Protocol for this connection: SFTP or SCP
+	Protocol string `json:"protocol"`
 	// active uploads/downloads
 	Transfers []connectionTransfer `json:"active_transfers"`
 }
@@ -190,6 +195,7 @@ func GetConnectionsStats() []ConnectionStatus {
 			RemoteAddress:  c.RemoteAddr.String(),
 			ConnectionTime: utils.GetTimeAsMsSinceEpoch(c.StartTime),
 			LastActivity:   utils.GetTimeAsMsSinceEpoch(c.lastActivity),
+			Protocol:       c.protocol,
 			Transfers:      []connectionTransfer{},
 		}
 		for _, t := range activeTransfers {
@@ -250,9 +256,7 @@ func CheckIdleConnections() {
 		if idleTime > idleTimeout {
 			logger.Debug(logSender, "close idle connection id: %v idle time: %v", c.ID, idleTime)
 			err := c.sshConn.Close()
-			if err != nil {
-				logger.Warn(logSender, "error closing idle connection: %v", err)
-			}
+			logger.Debug(logSender, "idle connection closed id: %v, err: %v", c.ID, err)
 		}
 	}
 	logger.Debug(logSender, "check idle connections ended")