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package sshd
import (
"context"
"encoding/base64"
"fmt"
"os"
"strconv"
"time"
"golang.org/x/crypto/ssh"
"gitlab.com/gitlab-org/gitlab-shell/internal/config"
"gitlab.com/gitlab-org/gitlab-shell/internal/gitlabnet/authorizedkeys"
"gitlab.com/gitlab-org/labkit/log"
)
type serverConfig struct {
cfg *config.Config
hostKeys []ssh.Signer
authorizedKeysClient *authorizedkeys.Client
}
func newServerConfig(cfg *config.Config) (*serverConfig, error) {
authorizedKeysClient, err := authorizedkeys.NewClient(cfg)
if err != nil {
return nil, fmt.Errorf("failed to initialize GitLab client: %w", err)
}
var hostKeys []ssh.Signer
for _, filename := range cfg.Server.HostKeyFiles {
keyRaw, err := os.ReadFile(filename)
if err != nil {
log.WithError(err).Warnf("Failed to read host key %v", filename)
continue
}
key, err := ssh.ParsePrivateKey(keyRaw)
if err != nil {
log.WithError(err).Warnf("Failed to parse host key %v", filename)
continue
}
hostKeys = append(hostKeys, key)
}
if len(hostKeys) == 0 {
return nil, fmt.Errorf("No host keys could be loaded, aborting")
}
return &serverConfig{cfg: cfg, authorizedKeysClient: authorizedKeysClient, hostKeys: hostKeys}, nil
}
func (s *serverConfig) getAuthKey(ctx context.Context, user string, key ssh.PublicKey) (*authorizedkeys.Response, error) {
if user != s.cfg.User {
return nil, fmt.Errorf("unknown user")
}
if key.Type() == ssh.KeyAlgoDSA {
return nil, fmt.Errorf("DSA is prohibited")
}
ctx, cancel := context.WithTimeout(ctx, 10*time.Second)
defer cancel()
res, err := s.authorizedKeysClient.GetByKey(ctx, base64.RawStdEncoding.EncodeToString(key.Marshal()))
if err != nil {
return nil, err
}
return res, nil
}
func (s *serverConfig) get(ctx context.Context) *ssh.ServerConfig {
sshCfg := &ssh.ServerConfig{
PublicKeyCallback: func(conn ssh.ConnMetadata, key ssh.PublicKey) (*ssh.Permissions, error) {
res, err := s.getAuthKey(ctx, conn.User(), key)
if err != nil {
return nil, err
}
return &ssh.Permissions{
// Record the public key used for authentication.
Extensions: map[string]string{
"key-id": strconv.FormatInt(res.Id, 10),
},
}, nil
},
}
for _, key := range s.hostKeys {
sshCfg.AddHostKey(key)
}
return sshCfg
}
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