feat: save to remote can be authed by Kerberos

app.go

@@ -337,10 +337,20 @@ func (a *App) runSaveRemotePipeline(pngBytes []byte) error {
 	}
 	slog.Info("save-remote dispatch",
 		"host", cfg.SSH.Host, "user", cfg.SSH.User, "port", cfg.SSH.Port,
-		"png_size", len(pngBytes))
+		"auth_method", cfg.SSH.AuthMethod, "png_size", len(pngBytes))
+
+	// Select the uploader by auth method: Kerberos delegates to the system
+	// ssh/scp binaries (reusing the kinit credential cache), while builtin
+	// uses the in-process Go SSH client.
+	var uploader application.SSHUploader
+	if cfg.SSH.IsKerberos() {
+		uploader = sshpkg.NewKerberosUploader(cfg.SSH)
+	} else {
+		uploader = sshpkg.NewUploader(cfg.SSH)
+	}
 
 	svc := &application.CaptureAndSSHService{
-		Uploader:  sshpkg.NewUploader(cfg.SSH),
+		Uploader:  uploader,
 		Clipboard: a.clip,
 		Notifier:  &runtimeNotifier{ctx: a.ctx},
 		Cfg:       cfg.SSH,
@@ -446,7 +456,17 @@ func (a *App) TestConnection(cfg domain.S3Config) error {
 func (a *App) TestSSHConnection(cfg domain.SSHConfig) error {
 	slog.Info("RPC TestSSHConnection",
 		"host", cfg.Host, "user", cfg.User, "port", cfg.Port,
+		"auth_method", cfg.AuthMethod,
 		"strict_host_key", cfg.StrictHostKey, "has_password", cfg.Password != "")
+	// Kerberos auth delegates to the system ssh binary (see KerberosUploader)
+	// so its probe path differs from the in-process client.
+	if cfg.IsKerberos() {
+		if err := sshpkg.TestKerberosConnection(a.ctx, cfg); err != nil {
+			slog.Error("RPC TestSSHConnection (kerberos) failed", "err", err)
+			return err
+		}
+		return nil
+	}
 	if err := sshpkg.TestConnection(a.ctx, cfg); err != nil {
 		slog.Error("RPC TestSSHConnection failed", "err", err)
 		return err

frontend/src/views/SettingsView.vue

@@ -43,6 +43,7 @@ interface SSHConfig {
   host: string
   port: number
   user: string
+  authMethod: string
   password: string
   pathPrefix: string
   strictHostKey: boolean
@@ -77,6 +78,7 @@ function defaultConfig(): AppConfig {
       host: '',
       port: 22,
       user: '',
+      authMethod: 'builtin',
       password: '',
       pathPrefix: 'snapgo/',
       strictHostKey: false,
@@ -280,14 +282,26 @@ onMounted(load)
             placeholder="22"
           />
         </label>
+        <div class="field-row auth-row">
+          <label class="field">
+            <span>Auth method</span>
+            <select v-model="config.ssh.authMethod">
+              <option value="builtin">Password / Key</option>
+              <option value="kerberos">Kerberos</option>
+            </select>
+          </label>
           <label class="field">
             <span>User *</span>
             <input v-model="config.ssh.user" placeholder="ubuntu" />
           </label>
-        <label class="field">
+          <label
+            v-if="config.ssh.authMethod !== 'kerberos'"
+            class="field"
+          >
             <span>Password (optional)</span>
             <input v-model="config.ssh.password" type="password" />
           </label>
+        </div>
         <label class="field full">
           <span>Remote path (under home)</span>
           <div class="prefixed-input">
@@ -324,7 +338,16 @@ onMounted(load)
           </span>
         </label>
       </div>
-      <p v-if="!config.ssh.password" class="hint warn">
+      <p v-if="config.ssh.authMethod === 'kerberos'" class="hint">
+        Kerberos mode delegates to the system <code>ssh</code>/<code>scp</code>.
+        Run <code>kinit {{ config.ssh.user || 'user' }}@BYTEDANCE.COM</code> in a terminal first; tickets
+        expire (typically every 10–24h), so re-run <code>kinit</code> if uploads
+        start failing. Verify with <code>klist</code>.
+      </p>
+      <p
+        v-else-if="!config.ssh.password"
+        class="hint warn"
+      >
         Password is empty — please make sure password-less SSH is configured on
         this machine (e.g. via <code>ssh-copy-id</code> or your <code>ssh-agent</code>).
       </p>
@@ -414,17 +437,30 @@ kbd {
 .field.full {
   grid-column: 1 / -1;
 }
+/* field-row groups several fields onto a single full-width row. auth-row
+   splits Auth method / User / Password roughly 1:2:2. */
+.field-row {
+  grid-column: 1 / -1;
+  display: grid;
+  gap: 12px 16px;
+}
+.auth-row {
+  grid-template-columns: 1fr 2fr 2fr;
+}
 .field span {
   color: #374151;
   font-weight: 500;
 }
 .field input[type='text'],
 .field input[type='number'],
-.field input:not([type='checkbox']) {
+.field input:not([type='checkbox']),
+.field select {
   border: 1px solid #d1d5db;
   border-radius: 6px;
   padding: 7px 10px;
   font-size: 13px;
+  line-height: 1.4;
+  height: 36px;
   background: #fff;
   color: inherit;
   outline: none;
@@ -432,7 +468,8 @@ kbd {
   width: 100%;
   box-sizing: border-box;
 }
-.field input:focus {
+.field input:focus,
+.field select:focus {
   border-color: #3b82f6;
   box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.18);
 }
@@ -560,6 +597,11 @@ kbd {
     border-color: #374151;
     color: #e5e7eb;
   }
+  .field select {
+    background: #111827;
+    border-color: #374151;
+    color: #e5e7eb;
+  }
   .field input:disabled {
     background: #1f2937;
     color: #6b7280;

frontend/wailsjs/go/models.ts

@@ -57,6 +57,7 @@ export namespace domain {
 	    host: string;
 	    port: number;
 	    user: string;
+	    authMethod: string;
 	    password: string;
 	    pathPrefix: string;
 	    strictHostKey: boolean;
@@ -72,6 +73,7 @@ export namespace domain {
 	        this.host = source["host"];
 	        this.port = source["port"];
 	        this.user = source["user"];
+	        this.authMethod = source["authMethod"];
 	        this.password = source["password"];
 	        this.pathPrefix = source["pathPrefix"];
 	        this.strictHostKey = source["strictHostKey"];

internal/domain/config.go

@@ -33,9 +33,18 @@ type S3Config struct {
 // Field design notes:
 //   - Host / Port form the destination endpoint. Port defaults to 22 when 0.
 //   - User is the SSH login name.
+//   - AuthMethod selects how the connection authenticates:
+//       "" / "builtin" → password / ssh-agent / ~/.ssh/id_* via the
+//                         in-process golang.org/x/crypto/ssh client.
+//       "kerberos"     → delegate to the system /usr/bin/ssh binary so the
+//                         existing Kerberos (GSSAPI) credential cache from
+//                         `kinit` is reused. Native GSSAPI is required here
+//                         because macOS stores tickets in an API: ccache
+//                         that pure-Go SSH libraries cannot read.
 //   - Password is optional; when empty the implementation falls back to the
 //     local SSH agent or ~/.ssh/id_* keys (i.e. the user is responsible for
 //     having password-less access already configured on this machine).
+//     It is ignored entirely when AuthMethod is "kerberos".
 //   - PathPrefix is interpreted *relative to the remote user's $HOME*. The
 //     UI presents it as "~/<PathPrefix>" so the user cannot escape the home
 //     directory by writing absolute paths. Leading "/" or "~" markers are
@@ -51,6 +60,7 @@ type SSHConfig struct {
 	Host               string `json:"host"`
 	Port               int    `json:"port"`
 	User               string `json:"user"`
+	AuthMethod         string `json:"authMethod"`
 	Password           string `json:"password"`
 	PathPrefix         string `json:"pathPrefix"`
 	StrictHostKey      bool   `json:"strictHostKey"`
@@ -58,6 +68,21 @@ type SSHConfig struct {
 	ConnectTimeoutSecs int    `json:"connectTimeoutSecs"`
 }
 
+// SSH authentication method identifiers stored in SSHConfig.AuthMethod.
+const (
+	// SSHAuthBuiltin uses the in-process Go SSH client (password / agent /
+	// key files). This is the zero-value default.
+	SSHAuthBuiltin = "builtin"
+	// SSHAuthKerberos delegates to the system ssh binary so an existing
+	// Kerberos credential cache (populated by `kinit`) is reused via GSSAPI.
+	SSHAuthKerberos = "kerberos"
+)
+
+// IsKerberos reports whether this config requests Kerberos/GSSAPI auth.
+func (c SSHConfig) IsKerberos() bool {
+	return c.AuthMethod == SSHAuthKerberos
+}
+
 // AppConfig is the top-level on-disk configuration document.
 //
 // We keep S3 / SSH nested so that adding more providers later (e.g. AliyunOSS,

internal/infrastructure/ssh/kerberos_uploader.go

@@ -0,0 +1,230 @@
+// kerberos_uploader.go — an SSHUploader implementation that delegates to
+// the system /usr/bin/ssh + /usr/bin/scp binaries so an existing Kerberos
+// (GSSAPI) credential cache populated by `kinit` is reused transparently.
+//
+// 设计理由 (为什么不用 golang.org/x/crypto/ssh 做 Kerberos):
+//   - macOS 的 Kerberos 票据默认存放在 API: 类型的 credential cache 中,
+//     由系统 GSSD (Heimdal) 守护进程托管. Go 生态的 gokrb5 只能读取
+//     FILE: 类型 ccache 与 keytab, 无法访问 API: ccache, 因此在 macOS 上
+//     用纯 Go 实现 GSSAPI 认证基本不可行.
+//   - 系统自带的 /usr/bin/ssh 原生集成 Heimdal GSSAPI, 用户 `kinit` 之后
+//     的票据可被直接复用. 把上传委托给系统 ssh/scp 是最稳妥的方案, 也与
+//     用户"命令行能免密登录即可"的预期完全一致.
+//   - 仅在 AuthMethod == kerberos 时启用此实现; builtin 路径不受影响.
+package ssh
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+	"path"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/mmmy/snapgo/internal/domain"
+)
+
+// systemSSHPath / systemSCPPath are the absolute paths to the macOS system
+// binaries. We use absolute paths rather than relying on $PATH so a hijacked
+// PATH cannot redirect us to an arbitrary binary, and because GUI apps on
+// macOS often launch with a minimal PATH that omits /usr/bin entirely.
+const (
+	systemSSHPath = "/usr/bin/ssh"
+	systemSCPPath = "/usr/bin/scp"
+)
+
+// KerberosUploader satisfies application.SSHUploader by shelling out to the
+// system scp binary with GSSAPI authentication enabled.
+type KerberosUploader struct {
+	cfg domain.SSHConfig
+}
+
+// NewKerberosUploader returns an uploader that delegates to system scp.
+func NewKerberosUploader(cfg domain.SSHConfig) *KerberosUploader {
+	return &KerberosUploader{cfg: cfg}
+}
+
+// Upload writes data to remoteRelPath (relative to the remote $HOME) by
+// staging it in a local temp file and invoking system scp once.
+//
+// We stage to a temp file because scp transfers files, not stdin; piping a
+// stream would require the more fragile `scp -t` sink protocol that we only
+// use for the in-process client. A temp file is simpler and robust.
+func (u *KerberosUploader) Upload(ctx context.Context, remoteRelPath string, data []byte, mode os.FileMode) error {
+	start := time.Now()
+	cleaned := normaliseRemotePath(remoteRelPath)
+	if cleaned == "" {
+		return fmt.Errorf("ssh(kerberos): remote path is empty")
+	}
+	sshLog().Info("kerberos uploader start",
+		"host", u.cfg.Host, "user", u.cfg.User, "port", u.cfg.Port,
+		"remote_path", cleaned, "size", len(data))
+
+	// 1. Ensure the remote directory tree exists. scp itself will not create
+	//    intermediate directories, so we run a remote `mkdir -p` first.
+	dir, _ := path.Split(cleaned)
+	dir = strings.Trim(dir, "/")
+	if dir != "" {
+		if err := u.runRemoteMkdir(ctx, dir); err != nil {
+			sshLog().Error("kerberos uploader mkdir failed",
+				"dir", dir, "elapsed", time.Since(start), "err", err)
+			return err
+		}
+	}
+
+	// 2. Stage the payload to a local temp file for scp to read.
+	tmp, err := os.CreateTemp("", "snapgo-scp-*.png")
+	if err != nil {
+		return fmt.Errorf("ssh(kerberos): create temp: %w", err)
+	}
+	tmpPath := tmp.Name()
+	defer os.Remove(tmpPath)
+	if _, err := tmp.Write(data); err != nil {
+		_ = tmp.Close()
+		return fmt.Errorf("ssh(kerberos): write temp: %w", err)
+	}
+	if err := tmp.Close(); err != nil {
+		return fmt.Errorf("ssh(kerberos): close temp: %w", err)
+	}
+	if err := os.Chmod(tmpPath, mode.Perm()); err != nil {
+		sshLog().Debug("kerberos uploader chmod temp failed", "err", err)
+	}
+
+	// 3. scp the temp file to "user@host:cleaned" (cleaned is relative to
+	//    $HOME, which scp interprets correctly for a remote login shell).
+	remoteTarget := fmt.Sprintf("%s@%s:%s", u.cfg.User, u.cfg.Host, cleaned)
+	args := append(u.commonSCPArgs(), tmpPath, remoteTarget)
+	if err := u.runCommand(ctx, systemSCPPath, args); err != nil {
+		sshLog().Error("kerberos uploader scp failed",
+			"remote_path", cleaned, "elapsed", time.Since(start), "err", err)
+		return err
+	}
+	sshLog().Info("kerberos uploader done",
+		"remote_path", cleaned, "size", len(data), "total_elapsed", time.Since(start))
+	return nil
+}
+
+// runRemoteMkdir runs `mkdir -p ~/<dir>` on the remote host via system ssh.
+func (u *KerberosUploader) runRemoteMkdir(ctx context.Context, dir string) error {
+	remote := fmt.Sprintf("%s@%s", u.cfg.User, u.cfg.Host)
+	// Quote the directory so spaces / metacharacters cannot break the shell
+	// command. dir is already normalised (no leading ~ or /).
+	cmd := "mkdir -p " + shellQuote("./"+dir)
+	args := append(u.commonSSHArgs(), remote, cmd)
+	return u.runCommand(ctx, systemSSHPath, args)
+}
+
+// commonSSHArgs builds the shared option set that enables GSSAPI auth and
+// disables interactive prompts (we want a hard failure, never a hang waiting
+// for a password the GUI cannot answer).
+func (u *KerberosUploader) commonSSHArgs() []string {
+	port := u.cfg.Port
+	if port <= 0 {
+		port = 22
+	}
+	timeout := u.cfg.ConnectTimeoutSecs
+	if timeout <= 0 {
+		timeout = 10
+	}
+	args := []string{
+		"-p", strconv.Itoa(port),
+		"-o", "GSSAPIAuthentication=yes",
+		"-o", "GSSAPIDelegateCredentials=no",
+		"-o", "PreferredAuthentications=gssapi-with-mic,gssapi-keyex",
+		"-o", "PubkeyAuthentication=no",
+		"-o", "PasswordAuthentication=no",
+		"-o", "KbdInteractiveAuthentication=no",
+		"-o", "BatchMode=yes",
+		"-o", "ConnectTimeout=" + strconv.Itoa(timeout),
+	}
+	args = append(args, u.hostKeyArgs()...)
+	return args
+}
+
+// commonSCPArgs mirrors commonSSHArgs but uses scp's uppercase -P port flag.
+func (u *KerberosUploader) commonSCPArgs() []string {
+	port := u.cfg.Port
+	if port <= 0 {
+		port = 22
+	}
+	timeout := u.cfg.ConnectTimeoutSecs
+	if timeout <= 0 {
+		timeout = 10
+	}
+	args := []string{
+		"-P", strconv.Itoa(port),
+		"-o", "GSSAPIAuthentication=yes",
+		"-o", "GSSAPIDelegateCredentials=no",
+		"-o", "PreferredAuthentications=gssapi-with-mic,gssapi-keyex",
+		"-o", "PubkeyAuthentication=no",
+		"-o", "PasswordAuthentication=no",
+		"-o", "KbdInteractiveAuthentication=no",
+		"-o", "BatchMode=yes",
+		"-o", "ConnectTimeout=" + strconv.Itoa(timeout),
+	}
+	args = append(args, u.hostKeyArgs()...)
+	return args
+}
+
+// hostKeyArgs maps StrictHostKey onto OpenSSH's StrictHostKeyChecking option,
+// keeping behaviour consistent with the in-process client.
+func (u *KerberosUploader) hostKeyArgs() []string {
+	if u.cfg.StrictHostKey {
+		if u.cfg.KnownHostsPath != "" {
+			return []string{
+				"-o", "StrictHostKeyChecking=yes",
+				"-o", "UserKnownHostsFile=" + u.cfg.KnownHostsPath,
+			}
+		}
+		return []string{"-o", "StrictHostKeyChecking=yes"}
+	}
+	// Non-strict: accept new keys automatically but still record them. This
+	// mirrors the in-process InsecureIgnoreHostKey trade-off the UI warns of.
+	return []string{"-o", "StrictHostKeyChecking=accept-new"}
+}
+
+// runCommand executes the given binary, capturing combined stderr so a
+// failure surfaces the remote/OpenSSH diagnostic instead of a bare exit code.
+func (u *KerberosUploader) runCommand(ctx context.Context, bin string, args []string) error {
+	cmd := exec.CommandContext(ctx, bin, args...)
+	var stderr bytes.Buffer
+	cmd.Stderr = &stderr
+	sshLog().Debug("kerberos exec", "bin", bin, "args", strings.Join(args, " "))
+	if err := cmd.Run(); err != nil {
+		msg := strings.TrimSpace(stderr.String())
+		if msg == "" {
+			msg = err.Error()
+		}
+		return fmt.Errorf("%s failed: %s", path.Base(bin), msg)
+	}
+	return nil
+}
+
+// TestKerberosConnection probes the remote host with system ssh, surfacing a
+// clear hint when no valid ticket is present.
+func TestKerberosConnection(ctx context.Context, cfg domain.SSHConfig) error {
+	sshLog().Info("kerberos test connection start",
+		"host", cfg.Host, "user", cfg.User, "port", cfg.Port)
+	u := &KerberosUploader{cfg: cfg}
+	remote := fmt.Sprintf("%s@%s", cfg.User, cfg.Host)
+	args := append(u.commonSSHArgs(), remote, "true")
+	if err := u.runCommand(ctx, systemSSHPath, args); err != nil {
+		// Detect the most common cause: no/expired Kerberos ticket.
+		if !hasKerberosTicket(ctx) {
+			return fmt.Errorf("no valid Kerberos ticket found — run `kinit %s@BYTEDANCE.COM` first (%w)", cfg.User, err)
+		}
+		return err
+	}
+	sshLog().Info("kerberos test connection ok")
+	return nil
+}
+
+// hasKerberosTicket reports whether `klist -s` indicates a valid ticket.
+// `klist -s` exits 0 when a valid TGT exists, non-zero otherwise.
+func hasKerberosTicket(ctx context.Context) bool {
+	cmd := exec.CommandContext(ctx, "/usr/bin/klist", "-s")
+	return cmd.Run() == nil
+}