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sftpd: add support for some SSH commands

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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
This commit is contained in:
Nicola Murino
2019-11-18 23:30:37 +01:00
parent ca6cb34d98
commit 9c4dbbc3f8
14 changed files with 564 additions and 131 deletions
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79
sftpd/server.go
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@@ -14,7 +14,6 @@ import (
"os"
"path/filepath"
"strconv"
"strings"
"sync"
"time"
@@ -61,13 +60,8 @@ type Configuration struct {
// Keys are a list of host keys
Keys []Key `json:"keys" mapstructure:"keys"`
// IsSCPEnabled determines if experimental SCP support is enabled.
// We have our own SCP implementation since we can't rely on scp system
// command to properly 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.
// Please do accurate tests yourself before enabling SCP and let us known
// if something does not work as expected for your use cases
// This setting is deprecated and will be removed in future versions,
// please add "scp" to the EnabledSSHCommands list to enable it.
IsSCPEnabled bool `json:"enable_scp" mapstructure:"enable_scp"`
// KexAlgorithms specifies the available KEX (Key Exchange) algorithms in
// preference order.
@@ -83,6 +77,27 @@ type Configuration struct {
// SetstatMode 0 means "normal mode": requests for changing permissions and owner/group are executed.
// 1 means "ignore mode": requests for changing permissions and owner/group are silently ignored.
SetstatMode int `json:"setstat_mode" mapstructure:"setstat_mode"`
// List of enabled SSH commands.
// We support the following SSH commands:
// - "scp". 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.
// Please do accurate tests yourself before enabling SCP and let us known
// if something does not work as expected for your use cases.
// SCP between two remote hosts is supported using the `-3` scp option.
// - "md5sum", "sha1sum", "sha256sum", "sha384sum", "sha512sum". Useful to check message
// digests for uploaded files. These commands are implemented inside SFTPGo so they
// work even if the matching system commands are not available, for example on Windows.
// - "cd", "pwd". Some mobile SFTP clients does not support the SFTP SSH_FXP_REALPATH and so
// they use "cd" and "pwd" SSH commands to get the initial directory.
// Currently `cd` do nothing and `pwd` always returns the "/" path.
//
// The following SSH commands are enabled by default: "md5sum", "sha1sum", "cd", "pwd".
// "*" enables all supported SSH commands.
EnabledSSHCommands []string `json:"enabled_ssh_commands" mapstructure:"enabled_ssh_commands"`
}
// Key contains information about host keys
@@ -159,6 +174,7 @@ func (c Configuration) Initialize(configDir string) error {
c.configureSecurityOptions(serverConfig)
c.configureLoginBanner(serverConfig, configDir)
c.configureSFTPExtensions()
c.checkSSHCommands()
listener, err := net.Listen("tcp", fmt.Sprintf("%s:%d", c.BindAddress, c.BindPort))
if err != nil {
@@ -298,24 +314,7 @@ func (c Configuration) AcceptInboundConnection(conn net.Conn, config *ssh.Server
go c.handleSftpConnection(channel, connection)
}
case "exec":
if c.IsSCPEnabled {
var msg execMsg
if err := ssh.Unmarshal(req.Payload, &msg); err == nil {
name, scpArgs, err := parseCommandPayload(msg.Command)
connection.Log(logger.LevelDebug, logSender, "new exec command: %#v args: %v user: %v, error: %v",
name, scpArgs, connection.User.Username, err)
if err == nil && name == "scp" && len(scpArgs) >= 2 {
ok = true
connection.protocol = protocolSCP
connection.channel = channel
scpCommand := scpCommand{
connection: connection,
args: scpArgs,
}
go scpCommand.handle()
}
}
}
ok = processSSHCommand(req.Payload, &connection, channel, c.EnabledSSHCommands)
}
req.Reply(ok, nil)
}
@@ -389,6 +388,26 @@ func loginUser(user dataprovider.User, loginType string) (*ssh.Permissions, erro
return p, nil
}
func (c *Configuration) checkSSHCommands() {
if utils.IsStringInSlice("*", c.EnabledSSHCommands) {
c.EnabledSSHCommands = GetSupportedSSHCommands()
return
}
sshCommands := []string{}
if c.IsSCPEnabled {
sshCommands = append(sshCommands, "scp")
}
for _, command := range c.EnabledSSHCommands {
if utils.IsStringInSlice(command, supportedSSHCommands) {
sshCommands = append(sshCommands, command)
} else {
logger.Warn(logSender, "", "unsupported ssh command: %#v ignored", command)
logger.WarnToConsole("unsupported ssh command: %#v ignored", command)
}
}
c.EnabledSSHCommands = sshCommands
}
// If no host keys are defined we try to use or generate the default one.
func (c *Configuration) checkHostKeys(configDir string) error {
var err error
@@ -460,11 +479,3 @@ func (c Configuration) generatePrivateKey(file string) error {
return nil
}
func parseCommandPayload(command string) (string, []string, error) {
parts := strings.Split(command, " ")
if len(parts) < 2 {
return parts[0], []string{}, nil
}
return parts[0], parts[1:], nil
}