ussd/internal/ssh/ssh.go

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2024-09-22 15:41:01 +02:00
package ssh
import (
"context"
"encoding/hex"
"errors"
"fmt"
"net"
"os"
"sync"
"golang.org/x/crypto/ssh"
"git.defalsify.org/vise.git/db"
"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 db.Db
auth map[string]string
}
func NewAuther(ctx context.Context, keyStore db.Db) *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) {
a.keyStore.SetLanguage(nil)
a.keyStore.SetPrefix(storage.DATATYPE_CUSTOM)
k := append([]byte{0x01}, pubKey.Marshal()...)
v, err := a.keyStore.Get(a.Ctx, k)
if err != nil {
return nil, err
}
ka := hex.EncodeToString(conn.SessionID())
va := string(v)
a.auth[ka] = va
fmt.Fprintf(os.Stderr, "connect: %s -> %s\n", ka, v)
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
}
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 db.Db) {
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)
}
cfg.AddHostKey(private)
lst, err := net.Listen("tcp", fmt.Sprintf("%s:%d", s.Host, s.Port))
if err != nil {
panic(err)
}
for running {
conn, err := lst.Accept()
if err != nil {
panic(err)
}
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)
}
}