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package handlers
import (
"context"
"encoding/base64"
"strings"
"sync/atomic"
"github.com/mimecast/dtail/internal"
"github.com/mimecast/dtail/internal/config"
"github.com/mimecast/dtail/internal/io/dlog"
"github.com/mimecast/dtail/internal/io/line"
"github.com/mimecast/dtail/internal/lcontext"
"github.com/mimecast/dtail/internal/omode"
"github.com/mimecast/dtail/internal/protocol"
sshserver "github.com/mimecast/dtail/internal/ssh/server"
user "github.com/mimecast/dtail/internal/user/server"
gossh "golang.org/x/crypto/ssh"
)
// ServerHandler implements the Reader and Writer interfaces to handle
// the Bi-directional communication between SSH client and server.
// This handler implements the handler of the SSH server.
type ServerHandler struct {
baseHandler
catLimiter chan struct{}
tailLimiter chan struct{}
serverCfg *config.ServerConfig
authKeyStore *sshserver.AuthKeyStore
regex string
commands map[string]commandHandler
sessionState sessionCommandState
// Track pending files waiting for limiter slots
pendingFiles int32
}
type commandHandler func(context.Context, lcontext.LContext, int, []string, func())
var _ Handler = (*ServerHandler)(nil)
// NewServerHandler returns the server handler.
func NewServerHandler(user *user.User, catLimiter,
tailLimiter chan struct{}, serverCfg *config.ServerConfig,
authKeyStore *sshserver.AuthKeyStore) *ServerHandler {
dlog.Server.Debug(user, "Creating new server handler")
if serverCfg == nil {
dlog.Server.FatalPanic("Missing server config in NewServerHandler")
}
h := ServerHandler{
baseHandler: baseHandler{
done: internal.NewDone(),
lines: make(chan *line.Line, 100),
serverMessages: make(chan string, 10),
maprMessages: make(chan string, 10),
ackCloseReceived: make(chan struct{}),
user: user,
codec: newProtocolCodec(user),
},
catLimiter: catLimiter,
tailLimiter: tailLimiter,
serverCfg: serverCfg,
authKeyStore: authKeyStore,
regex: ".",
}
if h.authKeyStore == nil {
h.authKeyStore = sshserver.AuthKeys()
}
h.handleCommandCb = h.handleUserCommand
h.commands = h.newCommandRegistry()
h.turbo.configure(h.turboManagerConfig())
fqdn, err := config.Hostname()
if err != nil {
dlog.Server.FatalPanic(err)
}
s := strings.Split(fqdn, ".")
h.hostname = s[0]
h.send(h.serverMessages, protocol.HiddenCapabilitiesPrefix+protocol.CapabilityQueryUpdateV1)
return &h
}
func (h *ServerHandler) handleUserCommand(ctx context.Context, ltx lcontext.LContext,
argc int, args []string, commandName string) {
dlog.Server.Debug(h.user, "Handling user command", argc, args)
shutdownOnCompletion := shouldShutdownOnCommandCompletion(commandName)
h.incrementActiveCommands()
commandFinished := func() {
activeCommands := h.decrementActiveCommands()
pendingFiles := atomic.LoadInt32(&h.pendingFiles)
dlog.Server.Debug(h.user, "Command finished", "activeCommands", activeCommands, "pendingFiles", pendingFiles)
// Only shutdown if no active commands AND no pending files.
// AUTHKEY is a session-side effect command and should not terminate the shell
// because user commands may still follow in the same session.
if shutdownOnCompletion && activeCommands == 0 && pendingFiles == 0 && !h.sessionState.keepAlive() {
h.shutdown()
}
}
handler, found := h.commands[commandName]
if !found {
h.sendln(h.serverMessages, dlog.Server.Error(h.user,
"Received unknown user command", commandName, argc, args))
commandFinished()
return
}
handler(ctx, ltx, argc, args, commandFinished)
}
func shouldShutdownOnCommandCompletion(commandName string) bool {
switch {
case strings.EqualFold(commandName, "AUTHKEY"):
return false
case strings.EqualFold(commandName, "SESSION"):
return false
default:
return true
}
}
func (h *ServerHandler) newCommandRegistry() map[string]commandHandler {
return map[string]commandHandler{
"grep": h.makeReadCommandHandler(omode.GrepClient, 1),
"cat": h.makeReadCommandHandler(omode.CatClient, 1),
"tail": h.makeReadCommandHandler(omode.TailClient, 10),
"map": h.handleMapCommand,
".ack": h.handleAckUserCommand,
"AUTHKEY": h.handleAuthKeyCommand,
"SESSION": h.handleSessionCommand,
"authkey": h.handleAuthKeyCommand,
"session": h.handleSessionCommand,
}
}
func (h *ServerHandler) makeReadCommandHandler(mode omode.Mode, tailBackoff int) commandHandler {
return func(ctx context.Context, ltx lcontext.LContext, argc int, args []string, commandFinished func()) {
command := newReadCommand(h, mode)
go func() {
command.Start(ctx, ltx, argc, args, tailBackoff)
commandFinished()
}()
}
}
func (h *ServerHandler) handleMapCommand(ctx context.Context, _ lcontext.LContext, argc int, args []string, commandFinished func()) {
command, aggregate, turboAggregate, err := newMapCommand(h, argc, args)
if err != nil {
h.sendln(h.serverMessages, err.Error())
dlog.Server.Error(h.user, err)
commandFinished()
return
}
h.aggregate = aggregate
h.turboAggregate = turboAggregate
go func() {
command.Start(ctx, h.maprMessages)
commandFinished()
}()
}
func (h *ServerHandler) handleAckUserCommand(_ context.Context, _ lcontext.LContext, argc int, args []string, commandFinished func()) {
h.handleAckCommand(argc, args)
commandFinished()
}
func (h *ServerHandler) handleAuthKeyCommand(_ context.Context, _ lcontext.LContext,
argc int, args []string, commandFinished func()) {
defer commandFinished()
if !h.serverCfg.AuthKeyEnabled {
h.sendln(h.serverMessages, "AUTHKEY ERR feature disabled")
return
}
if argc < 2 || strings.TrimSpace(args[1]) == "" {
h.sendln(h.serverMessages, "AUTHKEY ERR missing public key")
return
}
decodedPubKey, err := base64.StdEncoding.DecodeString(args[1])
if err != nil {
h.sendln(h.serverMessages, "AUTHKEY ERR invalid base64")
return
}
pubKey, err := gossh.ParsePublicKey(decodedPubKey)
if err != nil {
h.sendln(h.serverMessages, "AUTHKEY ERR invalid public key")
return
}
if h.authKeyStore == nil {
h.sendln(h.serverMessages, "AUTHKEY ERR internal key store unavailable")
return
}
h.authKeyStore.Add(h.user.Name, pubKey)
h.sendln(h.serverMessages, "AUTHKEY OK")
}
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