fix(workspace files API): GET ReadFile via SSH-EIC for SaaS workspaces (fixes 'No config.yaml found' on Config tab)

workspace-server/internal/handlers/template_files_eic.go

@@ -204,3 +204,116 @@ func writeFileViaEIC(ctx context.Context, instanceID, runtime, relPath string, c
 func shellQuote(s string) string {
 	return "'" + strings.ReplaceAll(s, "'", `'\''`) + "'"
 }
+
+// readFileViaEIC reads a single file from the workspace EC2 at the
+// absolute path that resolveWorkspaceFilePath computes. Mirrors
+// writeFileViaEIC end-to-end (ephemeral keypair, EIC tunnel, ssh) so
+// canvas's Config tab can GET back what it just PUT. Pre-fix the GET
+// path (templates.go ReadFile) only handled local Docker containers
+// + a host-side template fallback; SaaS workspaces (EC2-per-workspace)
+// always 404'd because neither handles their on-EC2 layout.
+//
+// Returns ("", os.ErrNotExist) when the remote path doesn't exist so
+// the handler can map it to HTTP 404 cleanly. Other errors propagate.
+func readFileViaEIC(ctx context.Context, instanceID, runtime, relPath string) ([]byte, error) {
+	if instanceID == "" {
+		return nil, fmt.Errorf("workspace has no instance_id — not a SaaS EC2 workspace")
+	}
+	absPath, err := resolveWorkspaceFilePath(runtime, relPath)
+	if err != nil {
+		return nil, fmt.Errorf("invalid path: %w", err)
+	}
+
+	osUser := os.Getenv("WORKSPACE_EC2_OS_USER")
+	if osUser == "" {
+		osUser = "ubuntu"
+	}
+	region := os.Getenv("AWS_REGION")
+	if region == "" {
+		region = "us-east-2"
+	}
+
+	ctx, cancel := context.WithTimeout(ctx, eicFileWriteTimeout)
+	defer cancel()
+
+	keyDir, err := os.MkdirTemp("", "molecule-fileread-*")
+	if err != nil {
+		return nil, fmt.Errorf("keydir mkdir: %w", err)
+	}
+	defer func() { _ = os.RemoveAll(keyDir) }()
+	keyPath := keyDir + "/id"
+	if out, kerr := exec.CommandContext(ctx, "ssh-keygen",
+		"-t", "ed25519", "-f", keyPath, "-N", "", "-q",
+		"-C", "molecule-fileread",
+	).CombinedOutput(); kerr != nil {
+		return nil, fmt.Errorf("ssh-keygen: %w (%s)", kerr, strings.TrimSpace(string(out)))
+	}
+	pubKey, err := os.ReadFile(keyPath + ".pub")
+	if err != nil {
+		return nil, fmt.Errorf("read pubkey: %w", err)
+	}
+
+	if err := sendSSHPublicKey(ctx, region, instanceID, osUser, strings.TrimSpace(string(pubKey))); err != nil {
+		return nil, fmt.Errorf("send-ssh-public-key: %w", err)
+	}
+
+	localPort, err := pickFreePort()
+	if err != nil {
+		return nil, fmt.Errorf("pick free port: %w", err)
+	}
+	tunnel := openTunnelCmd(eicSSHOptions{
+		InstanceID:     instanceID,
+		OSUser:         osUser,
+		Region:         region,
+		LocalPort:      localPort,
+		PrivateKeyPath: keyPath,
+	})
+	tunnel.Env = os.Environ()
+	if err := tunnel.Start(); err != nil {
+		return nil, fmt.Errorf("open-tunnel start: %w", err)
+	}
+	defer func() {
+		if tunnel.Process != nil {
+			_ = tunnel.Process.Kill()
+		}
+		_ = tunnel.Wait()
+	}()
+	if err := waitForPort(ctx, "127.0.0.1", localPort, 10*time.Second); err != nil {
+		return nil, fmt.Errorf("tunnel never listened: %w", err)
+	}
+
+	// `sudo -n cat`: /configs is root-owned by cloud-init (same reason
+	// writeFileViaEIC needs sudo to install). The path is built from a
+	// validated map + Clean(), so no user-controlled string reaches the
+	// shell here. `2>/dev/null` swallows `cat: ...: No such file` so
+	// the missing-file case returns empty stdout + non-zero exit, which
+	// we translate to os.ErrNotExist below.
+	sshCmd := exec.CommandContext(ctx, "ssh",
+		"-i", keyPath,
+		"-o", "StrictHostKeyChecking=no",
+		"-o", "UserKnownHostsFile=/dev/null",
+		"-o", "ServerAliveInterval=15",
+		"-p", fmt.Sprintf("%d", localPort),
+		fmt.Sprintf("%s@127.0.0.1", osUser),
+		fmt.Sprintf("sudo -n cat %s 2>/dev/null", shellQuote(absPath)),
+	)
+	sshCmd.Env = os.Environ()
+	var stdout, stderr bytes.Buffer
+	sshCmd.Stdout = &stdout
+	sshCmd.Stderr = &stderr
+	runErr := sshCmd.Run()
+	out := stdout.Bytes()
+	if runErr != nil {
+		// `cat` returns 1 on missing file; with 2>/dev/null we have no
+		// stderr distinguisher. Treat empty-stdout + non-zero exit as
+		// not-found rather than a tunnel/auth error (those usually
+		// produce stderr from ssh itself, not from the remote command).
+		if len(out) == 0 && stderr.Len() == 0 {
+			return nil, os.ErrNotExist
+		}
+		return nil, fmt.Errorf("ssh cat: %w (%s)", runErr, strings.TrimSpace(stderr.String()))
+	}
+	log.Printf("readFileViaEIC: ws instance=%s runtime=%s read %d bytes ← %s",
+		instanceID, runtime, len(out), absPath)
+	return out, nil
+}

workspace-server/internal/handlers/templates.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"errors"
 	"fmt"
 	"log"
 	"net/http"
@@ -349,16 +350,52 @@ func (h *TemplatesHandler) ReadFile(c *gin.Context) {
 		return
 	}
 
-	var wsName string
-	if err := db.DB.QueryRowContext(ctx, `SELECT name FROM workspaces WHERE id = $1`, workspaceID).Scan(&wsName); err != nil {
+	var wsName, instanceID, runtime string
+	if err := db.DB.QueryRowContext(ctx,
+		`SELECT name, COALESCE(instance_id, ''), COALESCE(runtime, '') FROM workspaces WHERE id = $1`,
+		workspaceID,
+	).Scan(&wsName, &instanceID, &runtime); err != nil {
 		c.JSON(http.StatusNotFound, gin.H{"error": "workspace not found"})
 		return
 	}
 
-	// Try container first. `cat` wants a single path argument — passing
-	// rootPath and filePath as two args would make `cat` try to read the
-	// rootPath directory (error) and then resolve filePath relative to
-	// the container's cwd, which isn't guaranteed to equal rootPath.
+	// SaaS workspace (EC2-per-workspace) — no Docker on this tenant. Read
+	// via SSH through the EIC endpoint, mirroring WriteFile's dispatch
+	// in this same file. Pre-fix this branch was missing and SaaS
+	// workspaces always fell through to the local-Docker container check
+	// (finds nothing on a SaaS tenant) + template-dir fallback (returns
+	// the seed template, not the persisted state). Net effect: the
+	// canvas Config tab always 404'd for SaaS workspaces — visible to
+	// users after #2781 added the "no config.yaml" error UX.
+	//
+	// The ?root= query param is intentionally ignored on the SaaS path —
+	// it's a local-Docker concept (arbitrary container roots). The
+	// runtime → base-path map (workspaceFilePathPrefix in
+	// template_files_eic.go) is the SaaS source of truth.
+	if instanceID != "" {
+		content, err := readFileViaEIC(ctx, instanceID, runtime, filePath)
+		if err == nil {
+			c.JSON(http.StatusOK, gin.H{
+				"path":    filePath,
+				"content": string(content),
+				"size":    len(content),
+			})
+			return
+		}
+		if errors.Is(err, os.ErrNotExist) {
+			c.JSON(http.StatusNotFound, gin.H{"error": "file not found on workspace"})
+			return
+		}
+		log.Printf("ReadFile EIC for %s path=%s: %v", workspaceID, filePath, err)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": fmt.Sprintf("failed to read file: %v", err)})
+		return
+	}
+
+	// Local Docker path: try the workspace container first. `cat` wants a
+	// single path argument — passing rootPath and filePath as two args
+	// would make `cat` try to read the rootPath directory (error) and
+	// then resolve filePath relative to the container's cwd, which
+	// isn't guaranteed to equal rootPath.
 	if containerName := h.findContainer(ctx, workspaceID); containerName != "" {
 		fullPath := strings.TrimRight(rootPath, "/") + "/" + filePath
 		content, err := h.execInContainer(ctx, containerName, []string{"cat", fullPath})

workspace-server/internal/handlers/templates_test.go

@@ -894,7 +894,7 @@ func TestReadFile_WorkspaceNotFound(t *testing.T) {
 
 	handler := NewTemplatesHandler(t.TempDir(), nil)
 
-	mock.ExpectQuery("SELECT name FROM workspaces WHERE id =").
+	mock.ExpectQuery(`SELECT name, COALESCE\(instance_id, ''\), COALESCE\(runtime, ''\) FROM workspaces WHERE id =`).
 		WithArgs("ws-nf").
 		WillReturnError(sql.ErrNoRows)
 
@@ -928,9 +928,14 @@ func TestReadFile_FallbackToHost_Success(t *testing.T) {
 
 	handler := NewTemplatesHandler(tmpDir, nil)
 
-	mock.ExpectQuery("SELECT name FROM workspaces WHERE id =").
+	// instance_id="" → SaaS branch skipped → falls through to local
+	// Docker / template-dir host fallback (the only path the test
+	// exercises). When instance_id is set, ReadFile would dispatch
+	// through readFileViaEIC, which is covered by integration tests.
+	mock.ExpectQuery(`SELECT name, COALESCE\(instance_id, ''\), COALESCE\(runtime, ''\) FROM workspaces WHERE id =`).
 		WithArgs("ws-read").
-		WillReturnRows(sqlmock.NewRows([]string{"name"}).AddRow("Reader Agent"))
+		WillReturnRows(sqlmock.NewRows([]string{"name", "instance_id", "runtime"}).
+			AddRow("Reader Agent", "", ""))
 
 	w := httptest.NewRecorder()
 	c, _ := gin.CreateTestContext(w)
@@ -964,9 +969,10 @@ func TestReadFile_FallbackToHost_NotFound(t *testing.T) {
 	tmpDir := t.TempDir()
 	handler := NewTemplatesHandler(tmpDir, nil)
 
-	mock.ExpectQuery("SELECT name FROM workspaces WHERE id =").
+	mock.ExpectQuery(`SELECT name, COALESCE\(instance_id, ''\), COALESCE\(runtime, ''\) FROM workspaces WHERE id =`).
 		WithArgs("ws-nofile").
-		WillReturnRows(sqlmock.NewRows([]string{"name"}).AddRow("No File Agent"))
+		WillReturnRows(sqlmock.NewRows([]string{"name", "instance_id", "runtime"}).
+			AddRow("No File Agent", "", ""))
 
 	w := httptest.NewRecorder()
 	c, _ := gin.CreateTestContext(w)