Merge pull request 'SSH server entry point.' (#77) from lash/ssh-2 into master

Reviewed-on: urdt/ussd#77

.gitignore

@@ -4,3 +4,5 @@ go.work*
 **/*/*.bin
 **/*/.state/
 cmd/.state/
+id_*
+*.gdbm

cmd/ssh/README.md

@@ -0,0 +1,34 @@
+# URDT-USSD SSH server
+
+An SSH server entry point for the vise engine.
+
+
+## Adding public keys for access
+
+Map your (client) public key to a session identifier (e.g. phone number)
+
+```
+go run -v -tags logtrace ./cmd/ssh/sshkey/main.go -i <session_id> [--dbdir <dbpath>] <client_publickey_filepath>
+```
+
+
+## Create a private key for the server
+
+```
+ssh-keygen -N "" -f <server_privatekey_filepath>
+```
+
+
+## Run the server
+
+
+```
+go run -v -tags logtrace ./cmd/ssh/main.go -h <host> -p <port> [--dbdir <dbpath>] <server_privatekey_filepath>
+```
+
+
+## Connect to the server
+
+```
+ssh [-v] -T -p <port> -i <client_publickey_filepath> <host>
+```

cmd/ssh/main.go

@@ -0,0 +1,115 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"path"
+	"os"
+	"os/signal"
+	"sync"
+	"syscall"
+
+	"git.defalsify.org/vise.git/db"
+	"git.defalsify.org/vise.git/engine"
+	"git.defalsify.org/vise.git/logging"
+
+	"git.grassecon.net/urdt/ussd/internal/ssh"
+)
+
+var (
+	wg sync.WaitGroup
+	keyStore db.Db
+	logg      = logging.NewVanilla()
+	scriptDir = path.Join("services", "registration")
+)
+
+func main() {
+	var dbDir string
+	var resourceDir string
+	var size uint
+	var engineDebug bool
+	var stateDebug bool
+	var host string
+	var port uint
+	flag.StringVar(&dbDir, "dbdir", ".state", "database dir to read from")
+	flag.StringVar(&resourceDir, "resourcedir", path.Join("services", "registration"), "resource dir")
+	flag.BoolVar(&engineDebug, "engine-debug", false, "use engine debug output")
+	flag.BoolVar(&stateDebug, "state-debug", false, "use engine debug output")
+	flag.UintVar(&size, "s", 160, "max size of output")
+	flag.StringVar(&host, "h", "127.0.0.1", "http host")
+	flag.UintVar(&port, "p", 7122, "http port")
+	flag.Parse()
+
+	sshKeyFile := flag.Arg(0)
+	_, err := os.Stat(sshKeyFile)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "cannot open ssh server private key file: %v\n", err)
+		os.Exit(1)
+	}
+
+	ctx := context.Background()
+	logg.WarnCtxf(ctx, "!!!!! WARNING WARNING WARNING")
+	logg.WarnCtxf(ctx, "!!!!! =======================")
+	logg.WarnCtxf(ctx, "!!!!! This is not a production ready server!")
+	logg.WarnCtxf(ctx, "!!!!! Do not expose to internet and only use with tunnel!")
+	logg.WarnCtxf(ctx, "!!!!! (See ssh -L <...>)")
+
+	logg.Infof("start command", "dbdir", dbDir, "resourcedir", resourceDir, "outputsize", size, "keyfile", sshKeyFile, "host", host, "port", port)
+
+	pfp := path.Join(scriptDir, "pp.csv")
+
+	cfg := engine.Config{
+		Root:       "root",
+		OutputSize: uint32(size),
+		FlagCount:  uint32(16),
+	}
+	if stateDebug {
+		cfg.StateDebug = true
+	}
+	if engineDebug {
+		cfg.EngineDebug = true
+	}
+
+	authKeyStore, err := ssh.NewSshKeyStore(ctx, dbDir)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "keystore file open error: %v", err)
+		os.Exit(1)
+	}
+	defer func () {
+		logg.TraceCtxf(ctx, "shutdown auth key store reached")
+		err = authKeyStore.Close()
+		if err != nil {
+			logg.ErrorCtxf(ctx, "keystore close error", "err", err)
+		}
+	}()
+
+	cint := make(chan os.Signal)
+	cterm := make(chan os.Signal)
+	signal.Notify(cint, os.Interrupt, syscall.SIGINT)
+	signal.Notify(cterm, os.Interrupt, syscall.SIGTERM)
+
+	runner := &ssh.SshRunner{
+		Cfg: cfg,
+		Debug: engineDebug,
+		FlagFile: pfp,
+		DbDir: dbDir,
+		ResourceDir: resourceDir,
+		SrvKeyFile: sshKeyFile,
+		Host: host,
+		Port: port,
+	}
+	go func() {
+		select {
+		case _ = <-cint:
+		case _ = <-cterm:
+		}
+		logg.TraceCtxf(ctx, "shutdown runner reached")
+		err := runner.Stop()
+		if err != nil {
+			logg.ErrorCtxf(ctx, "runner stop error", "err", err)
+		}
+		
+	}()
+	runner.Run(ctx, authKeyStore)
+}

cmd/ssh/sshkey/main.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"os"
+
+	"git.grassecon.net/urdt/ussd/internal/ssh"
+)
+
+func main() {
+	var dbDir string
+	var sessionId string
+	flag.StringVar(&dbDir, "dbdir", ".state", "database dir to read from")
+	flag.StringVar(&sessionId, "i", "", "session id")
+	flag.Parse()
+
+	if sessionId == "" {
+		fmt.Fprintf(os.Stderr, "empty session id\n")
+		os.Exit(1)
+	}
+
+	ctx := context.Background()
+
+	sshKeyFile := flag.Arg(0)
+	if sshKeyFile == "" {
+		fmt.Fprintf(os.Stderr, "missing key file argument\n")
+		os.Exit(1)
+	}
+
+	store, err := ssh.NewSshKeyStore(ctx, dbDir)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%v\n", err)
+		os.Exit(1)
+	}
+	defer store.Close()
+
+	err = store.AddFromFile(ctx, sshKeyFile, sessionId)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%v\n", err)
+		os.Exit(1)
+	}
+}

internal/ssh/keystore.go

@@ -0,0 +1,64 @@
+package ssh
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path"
+
+	"golang.org/x/crypto/ssh"
+
+	"git.defalsify.org/vise.git/db"
+
+	"git.grassecon.net/urdt/ussd/internal/storage"
+)
+
+type SshKeyStore struct {
+	store db.Db
+}
+
+func NewSshKeyStore(ctx context.Context, dbDir string) (*SshKeyStore, error) {
+	keyStore := &SshKeyStore{}
+	keyStoreFile := path.Join(dbDir, "ssh_authorized_keys.gdbm")
+	keyStore.store = storage.NewThreadGdbmDb()
+	err := keyStore.store.Connect(ctx, keyStoreFile)
+	if err != nil {
+		return nil, err
+	}
+	return keyStore, nil
+}
+
+func(s *SshKeyStore) AddFromFile(ctx context.Context, fp string, sessionId string) error {
+	_, err := os.Stat(fp)
+	if err != nil {
+		return fmt.Errorf("cannot open ssh server public key file: %v\n", err)
+	}
+
+	publicBytes, err := os.ReadFile(fp)
+	if err != nil {
+		return fmt.Errorf("Failed to load public key: %v", err)
+	}
+	pubKey, _, _, _, err := ssh.ParseAuthorizedKey(publicBytes)
+	if err != nil {
+		return fmt.Errorf("Failed to parse public key: %v", err)
+	}
+	k := append([]byte{0x01}, pubKey.Marshal()...)
+	s.store.SetPrefix(storage.DATATYPE_CUSTOM)
+	logg.Infof("Added key", "sessionId", sessionId, "public key", string(publicBytes))
+	return s.store.Put(ctx, k, []byte(sessionId))
+}
+
+func(s *SshKeyStore) Get(ctx context.Context, pubKey ssh.PublicKey) (string, error) {
+	s.store.SetLanguage(nil)
+	s.store.SetPrefix(storage.DATATYPE_CUSTOM)
+	k := append([]byte{0x01}, pubKey.Marshal()...)
+	v, err := s.store.Get(ctx, k)
+	if err != nil {
+		return "", err
+	}
+	return string(v), nil
+}
+
+func(s *SshKeyStore) Close() error {
+	return s.store.Close()
+}

internal/ssh/ssh.go

@@ -0,0 +1,284 @@
+package ssh
+
+import (
+	"context"
+	"encoding/hex"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"net"
+	"os"
+	"sync"
+
+	"golang.org/x/crypto/ssh"
+
+	"git.defalsify.org/vise.git/engine"
+	"git.defalsify.org/vise.git/logging"
+	"git.defalsify.org/vise.git/resource"
+	"git.defalsify.org/vise.git/state"
+
+	"git.grassecon.net/urdt/ussd/internal/handlers"
+	"git.grassecon.net/urdt/ussd/internal/storage"
+)
+
+var (
+	logg = logging.NewVanilla().WithDomain("ssh")
+)
+
+type auther struct {
+	Ctx context.Context
+	keyStore *SshKeyStore
+	auth map[string]string
+}
+
+func NewAuther(ctx context.Context, keyStore *SshKeyStore) *auther {
+	return &auther{
+		Ctx: ctx,
+		keyStore: keyStore,
+		auth: make(map[string]string),
+	}
+}
+
+func(a *auther) Check(conn ssh.ConnMetadata, pubKey ssh.PublicKey) (*ssh.Permissions, error) {
+	va, err := a.keyStore.Get(a.Ctx, pubKey)
+	if err != nil {
+		return nil, err
+	}
+	ka := hex.EncodeToString(conn.SessionID())
+	a.auth[ka] = va 
+	fmt.Fprintf(os.Stderr, "connect: %s -> %s\n", ka, va)
+	return nil, nil
+}
+
+func(a *auther) FromConn(c *ssh.ServerConn) (string, error) {
+	if c == nil {
+		return "", errors.New("nil server conn")
+	}
+	if c.Conn == nil {
+		return "", errors.New("nil underlying conn")
+	}
+	return a.Get(c.Conn.SessionID())
+}
+
+
+func(a *auther) Get(k []byte) (string, error) {
+	ka := hex.EncodeToString(k)
+	v, ok := a.auth[ka]
+	if !ok {
+		return "", errors.New("not found")
+	}
+	return v, nil
+}
+
+func(s *SshRunner) serve(ctx context.Context, sessionId string, ch ssh.NewChannel, en engine.Engine) error {
+	if ch == nil {
+		return errors.New("nil channel")
+	}
+	if ch.ChannelType() != "session" {
+		ch.Reject(ssh.UnknownChannelType, "that is not the channel you are looking for")
+		return errors.New("not a session")
+	}
+	channel, requests, err := ch.Accept()
+	if err != nil {
+		panic(err)
+	}
+	defer channel.Close()
+	s.wg.Add(1)
+	go func(reqIn <-chan *ssh.Request) {
+		defer s.wg.Done()
+		for req := range reqIn {
+			req.Reply(req.Type == "shell", nil)	
+		}
+		_ = requests
+	}(requests)
+
+	cont, err := en.Exec(ctx, []byte{})
+	if err != nil {
+		return fmt.Errorf("initial engine exec err: %v", err)
+	}
+
+	var input [state.INPUT_LIMIT]byte
+	for cont {
+		c, err := en.Flush(ctx, channel)
+		if err != nil {
+			return fmt.Errorf("flush err: %v", err)
+		}
+		_, err = channel.Write([]byte{0x0a})
+		if err != nil {
+			return fmt.Errorf("newline err: %v", err)
+		}
+		c, err = channel.Read(input[:])
+		if err != nil {
+			return fmt.Errorf("read input fail: %v", err)
+		}
+		logg.TraceCtxf(ctx, "input read", "c", c, "input", input[:c-1])
+		cont, err = en.Exec(ctx, input[:c-1])
+		if err != nil {
+			return fmt.Errorf("engine exec err: %v", err)
+		}
+		logg.TraceCtxf(ctx, "exec cont", "cont", cont, "en", en)
+		_ = c
+	}
+	c, err := en.Flush(ctx, channel)
+	if err != nil {
+		return fmt.Errorf("last flush err: %v", err)
+	}
+	_ = c
+	return nil
+}
+
+type SshRunner struct {
+	Ctx context.Context
+	Cfg engine.Config
+	FlagFile string
+	DbDir string
+	ResourceDir string
+	Debug bool
+	SrvKeyFile string
+	Host string
+	Port uint
+	wg sync.WaitGroup
+	lst net.Listener
+}
+
+func(s *SshRunner) Stop() error {
+	return s.lst.Close()
+}
+
+func(s *SshRunner) GetEngine(sessionId string) (engine.Engine, func(), error) {
+	ctx := s.Ctx
+	menuStorageService := storage.NewMenuStorageService(s.DbDir, s.ResourceDir)
+
+	err := menuStorageService.EnsureDbDir()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	rs, err := menuStorageService.GetResource(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	pe, err := menuStorageService.GetPersister(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	userdatastore, err := menuStorageService.GetUserdataDb(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	dbResource, ok := rs.(*resource.DbResource)
+	if !ok {
+		return nil, nil, err
+	}
+
+	lhs, err := handlers.NewLocalHandlerService(s.FlagFile, true, dbResource, s.Cfg, rs)
+	lhs.SetDataStore(&userdatastore)
+	lhs.SetPersister(pe)
+	lhs.Cfg.SessionId = sessionId
+
+	if err != nil {
+		return nil, nil, err
+	}
+
+	hl, err := lhs.GetHandler()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	en := lhs.GetEngine()
+	en = en.WithFirst(hl.Init)
+	if s.Debug {
+		en = en.WithDebug(nil)
+	}
+	// TODO: this is getting very hacky!
+	closer := func() {
+		err := menuStorageService.Close()
+		if err != nil {
+			logg.ErrorCtxf(ctx, "menu storage service cleanup fail", "err", err)
+		}
+	}
+	return en, closer, nil
+}
+
+// adapted example from crypto/ssh package, NewServerConn doc
+func(s *SshRunner) Run(ctx context.Context, keyStore *SshKeyStore) {
+	running := true
+
+	// TODO: waitgroup should probably not be global
+	defer s.wg.Wait()
+
+	auth := NewAuther(ctx, keyStore)
+	cfg := ssh.ServerConfig{
+		PublicKeyCallback: auth.Check,
+	}
+
+	privateBytes, err := os.ReadFile(s.SrvKeyFile)
+	if err != nil {
+		logg.ErrorCtxf(ctx, "Failed to load private key", "err", err)
+	}
+	private, err := ssh.ParsePrivateKey(privateBytes)
+	if err != nil {
+		logg.ErrorCtxf(ctx, "Failed to parse private key", "err", err)
+	}
+	srvPub := private.PublicKey()
+	srvPubStr := base64.StdEncoding.EncodeToString(srvPub.Marshal())
+	logg.InfoCtxf(ctx, "have server key", "type", srvPub.Type(), "public", srvPubStr)
+	cfg.AddHostKey(private)
+
+	s.lst, err = net.Listen("tcp", fmt.Sprintf("%s:%d", s.Host, s.Port))
+	if err != nil {
+		panic(err)
+	}
+
+	for running {
+		conn, err := s.lst.Accept()
+		if err != nil {
+			logg.ErrorCtxf(ctx, "ssh accept error", "err", err)
+			running = false
+			continue
+		}
+
+		go func(conn net.Conn) {
+			defer conn.Close()
+			for true {
+				srvConn, nC, rC, err := ssh.NewServerConn(conn, &cfg)
+				if err != nil {
+					logg.InfoCtxf(ctx, "rejected client", "err", err)
+					return
+				}
+				logg.DebugCtxf(ctx, "ssh client connected", "conn", srvConn)
+
+				s.wg.Add(1)
+				go func() {
+					ssh.DiscardRequests(rC)
+					s.wg.Done()
+				}()
+				
+				sessionId, err := auth.FromConn(srvConn)
+				if err != nil {
+					logg.ErrorCtxf(ctx, "Cannot find authentication")
+					return
+				}
+				en, closer, err := s.GetEngine(sessionId)
+				if err != nil {
+					logg.ErrorCtxf(ctx, "engine won't start", "err", err)
+					return
+				}
+				defer func() {
+					err := en.Finish()
+					if err != nil {
+						logg.ErrorCtxf(ctx, "engine won't stop", "err", err)
+					}
+					closer()
+				}()
+				for ch := range nC {
+					err = s.serve(ctx, sessionId, ch, en)
+					logg.ErrorCtxf(ctx, "ssh server finish", "err", err)
+				}
+			}
+		}(conn)
+	}
+}