Add secure dashboard-managed SSH public-key access

Replace server-generated key escrow with public-key-only enable/disable
tasks. Validate ED25519 keys, atomically reconcile one marked
authorized_keys entry, preserve operator keys, and never handle
private keys. Return real task errors and add lifecycle tests.

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## [1.4.0] - 23-09-2026
+
+* Added dashboard-managed SSH public-key access.
+* Validates ED25519 public keys and reports their SHA256 fingerprints.
+* Atomically installs or removes only the marked Edgebox key while preserving all other authorized keys.
+* Never generates, reads, stores, logs, or returns SSH private keys.
+
 ## [1.3.2] - 08-12-2024
 
 * Fix to Browser Dev feature:
@@ -20,4 +27,3 @@
 ### Missing Past Releases
 
 Release notes for past versions are not available in this file. Please refer to the [GitHub releases](https://hithub.com/edgebox-iot/edgeboxctl/releases) for more information. Feel free to contribute to this file by adding missing release notes.
-

internal/tasks/ssh_access.go

@@ -0,0 +1,217 @@
+package tasks
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"github.com/edgebox-iot/edgeboxctl/internal/utils"
+)
+
+const (
+	sshDirectory      = "/root/.ssh"
+	managedSSHComment = "edgebox-dashboard-managed"
+)
+
+type sshAccessResult struct {
+	Status      string `json:"status"`
+	PublicKey   string `json:"public_key,omitempty"`
+	Fingerprint string `json:"fingerprint,omitempty"`
+}
+
+func taskEnableSSHAccess(args taskEnableSSHAccessArgs) (string, error) {
+	if err := verifyRootSSHAccess(); err != nil {
+		return "", err
+	}
+
+	publicKey, fingerprint, err := parseSSHEd25519PublicKey(args.PublicKey)
+	if err != nil {
+		return "", err
+	}
+
+	if err := reconcileManagedSSHKey(sshDirectory, publicKey); err != nil {
+		return "", err
+	}
+
+	utils.WriteOption("SSH_ACCESS_ENABLED", "true")
+	utils.WriteOption("SSH_PUBLIC_KEY", publicKey)
+	utils.WriteOption("SSH_KEY_FINGERPRINT", fingerprint)
+
+	result, err := json.Marshal(sshAccessResult{
+		Status:      "enabled",
+		PublicKey:   publicKey,
+		Fingerprint: fingerprint,
+	})
+	if err != nil {
+		return "", err
+	}
+
+	return string(result), nil
+}
+
+func taskDisableSSHAccess() (string, error) {
+	if err := reconcileManagedSSHKey(sshDirectory, ""); err != nil {
+		return "", err
+	}
+
+	utils.WriteOption("SSH_ACCESS_ENABLED", "false")
+	utils.DeleteOption("SSH_PUBLIC_KEY")
+	utils.DeleteOption("SSH_KEY_FINGERPRINT")
+
+	result, err := json.Marshal(sshAccessResult{Status: "disabled"})
+	if err != nil {
+		return "", err
+	}
+
+	return string(result), nil
+}
+
+func parseSSHEd25519PublicKey(input string) (string, string, error) {
+	trimmed := strings.TrimSpace(input)
+	if trimmed == "" || strings.ContainsAny(trimmed, "\r\n") {
+		return "", "", fmt.Errorf("provide exactly one SSH public key")
+	}
+
+	fields := strings.Fields(trimmed)
+	if len(fields) < 2 || len(fields) > 3 || fields[0] != "ssh-ed25519" {
+		return "", "", fmt.Errorf("only one ssh-ed25519 public key is supported")
+	}
+
+	keyBlob, err := base64.StdEncoding.DecodeString(fields[1])
+	if err != nil || !validEd25519KeyBlob(keyBlob) {
+		return "", "", fmt.Errorf("invalid ssh-ed25519 public key")
+	}
+
+	digest := sha256.Sum256(keyBlob)
+	publicKey := "ssh-ed25519 " + base64.StdEncoding.EncodeToString(keyBlob) + " " + managedSSHComment
+	fingerprint := "SHA256:" + base64.RawStdEncoding.EncodeToString(digest[:])
+
+	return publicKey, fingerprint, nil
+}
+
+func validEd25519KeyBlob(blob []byte) bool {
+	if len(blob) < 4 {
+		return false
+	}
+
+	typeLength := int(binary.BigEndian.Uint32(blob[:4]))
+	if typeLength != len("ssh-ed25519") || len(blob) < 4+typeLength+4 {
+		return false
+	}
+	if string(blob[4:4+typeLength]) != "ssh-ed25519" {
+		return false
+	}
+
+	keyLengthOffset := 4 + typeLength
+	keyLength := int(binary.BigEndian.Uint32(blob[keyLengthOffset : keyLengthOffset+4]))
+	return keyLength == 32 && len(blob) == keyLengthOffset+4+keyLength
+}
+
+func reconcileManagedSSHKey(directory string, publicKey string) error {
+	if info, err := os.Lstat(directory); err == nil {
+		if info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
+			return fmt.Errorf("SSH directory is not a regular directory")
+		}
+	} else if !os.IsNotExist(err) {
+		return fmt.Errorf("inspect SSH directory: %w", err)
+	} else if err := os.MkdirAll(directory, 0700); err != nil {
+		return fmt.Errorf("create SSH directory: %w", err)
+	}
+
+	if err := os.Chmod(directory, 0700); err != nil {
+		return fmt.Errorf("secure SSH directory: %w", err)
+	}
+
+	authorizedKeysPath := filepath.Join(directory, "authorized_keys")
+	if info, err := os.Lstat(authorizedKeysPath); err == nil && info.Mode()&os.ModeSymlink != 0 {
+		return fmt.Errorf("authorized_keys must not be a symbolic link")
+	} else if err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("inspect authorized_keys: %w", err)
+	}
+
+	existing, err := os.ReadFile(authorizedKeysPath)
+	if err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("read authorized_keys: %w", err)
+	}
+
+	lines := strings.Split(string(existing), "\n")
+	kept := make([]string, 0, len(lines)+1)
+	for _, line := range lines {
+		if strings.TrimSpace(line) == "" || isManagedSSHKey(line) {
+			continue
+		}
+		kept = append(kept, line)
+	}
+	if publicKey != "" {
+		kept = append(kept, publicKey)
+	}
+
+	contents := ""
+	if len(kept) > 0 {
+		contents = strings.Join(kept, "\n") + "\n"
+	}
+
+	temporary, err := os.CreateTemp(directory, ".authorized_keys-*")
+	if err != nil {
+		return fmt.Errorf("create authorized_keys temporary file: %w", err)
+	}
+	temporaryPath := temporary.Name()
+	defer os.Remove(temporaryPath)
+
+	if err := temporary.Chmod(0600); err != nil {
+		temporary.Close()
+		return fmt.Errorf("secure authorized_keys temporary file: %w", err)
+	}
+	if _, err := temporary.WriteString(contents); err != nil {
+		temporary.Close()
+		return fmt.Errorf("write authorized_keys: %w", err)
+	}
+	if err := temporary.Sync(); err != nil {
+		temporary.Close()
+		return fmt.Errorf("sync authorized_keys: %w", err)
+	}
+	if err := temporary.Close(); err != nil {
+		return fmt.Errorf("close authorized_keys: %w", err)
+	}
+	if err := os.Rename(temporaryPath, authorizedKeysPath); err != nil {
+		return fmt.Errorf("replace authorized_keys: %w", err)
+	}
+
+	return nil
+}
+
+func isManagedSSHKey(line string) bool {
+	fields := strings.Fields(line)
+	return len(fields) == 3 && fields[2] == managedSSHComment
+}
+
+func verifyRootSSHAccess() error {
+	sshdPath, err := exec.LookPath("sshd")
+	if err != nil {
+		sshdPath = "/usr/sbin/sshd"
+		if _, statErr := os.Stat(sshdPath); statErr != nil {
+			return fmt.Errorf("OpenSSH server is not installed")
+		}
+	}
+
+	output, err := exec.Command(sshdPath, "-T").Output()
+	if err != nil {
+		return fmt.Errorf("could not verify the effective SSH server configuration")
+	}
+
+	settings := string(output)
+	if !strings.Contains(settings, "pubkeyauthentication yes") {
+		return fmt.Errorf("SSH public-key authentication is disabled")
+	}
+	if strings.Contains(settings, "permitrootlogin no") {
+		return fmt.Errorf("SSH root login is disabled")
+	}
+
+	return nil
+}

internal/tasks/ssh_access_test.go

@@ -0,0 +1,111 @@
+package tasks
+
+import (
+	"encoding/base64"
+	"encoding/binary"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func testPublicKey(t *testing.T) string {
+	t.Helper()
+	blob := make([]byte, 4+len("ssh-ed25519")+4+32)
+	binary.BigEndian.PutUint32(blob[:4], uint32(len("ssh-ed25519")))
+	copy(blob[4:], "ssh-ed25519")
+	offset := 4 + len("ssh-ed25519")
+	binary.BigEndian.PutUint32(blob[offset:offset+4], 32)
+	for index := 0; index < 32; index++ {
+		blob[offset+4+index] = byte(index + 1)
+	}
+	return "ssh-ed25519 " + base64.StdEncoding.EncodeToString(blob) + " workstation"
+}
+
+func TestParseSSHEd25519PublicKey(t *testing.T) {
+	publicKey, fingerprint, err := parseSSHEd25519PublicKey(testPublicKey(t))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasSuffix(publicKey, " "+managedSSHComment) {
+		t.Fatalf("public key does not have managed marker: %q", publicKey)
+	}
+	if !strings.HasPrefix(fingerprint, "SHA256:") {
+		t.Fatalf("unexpected fingerprint: %q", fingerprint)
+	}
+}
+
+func TestParseSSHEd25519PublicKeyRejectsUnsafeInput(t *testing.T) {
+	inputs := []string{
+		"",
+		"-----BEGIN OPENSSH PRIVATE KEY-----",
+		testPublicKey(t) + "\n" + testPublicKey(t),
+		"command=whoami " + testPublicKey(t),
+		"ssh-rsa AAAA invalid",
+	}
+	for _, input := range inputs {
+		if _, _, err := parseSSHEd25519PublicKey(input); err == nil {
+			t.Fatalf("expected input to be rejected: %q", input)
+		}
+	}
+}
+
+func TestReconcileManagedSSHKeyPreservesUnrelatedKeys(t *testing.T) {
+	directory := t.TempDir()
+	authorizedKeysPath := filepath.Join(directory, "authorized_keys")
+	original := "# operator key\nssh-ed25519 AAAAoperator operator\n"
+	if err := os.WriteFile(authorizedKeysPath, []byte(original), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	publicKey, _, err := parseSSHEd25519PublicKey(testPublicKey(t))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := reconcileManagedSSHKey(directory, publicKey); err != nil {
+		t.Fatal(err)
+	}
+	if err := reconcileManagedSSHKey(directory, publicKey); err != nil {
+		t.Fatal(err)
+	}
+
+	contents, err := os.ReadFile(authorizedKeysPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Count(string(contents), managedSSHComment) != 1 {
+		t.Fatalf("managed key is not idempotent: %s", contents)
+	}
+	if !strings.Contains(string(contents), original) {
+		t.Fatalf("unrelated content was changed: %s", contents)
+	}
+	if info, err := os.Stat(authorizedKeysPath); err != nil || info.Mode().Perm() != 0600 {
+		t.Fatalf("authorized_keys mode is not 0600: %v, %v", info, err)
+	}
+
+	if err := reconcileManagedSSHKey(directory, ""); err != nil {
+		t.Fatal(err)
+	}
+	contents, err = os.ReadFile(authorizedKeysPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(contents) != original {
+		t.Fatalf("disable changed unrelated content: %q", contents)
+	}
+}
+
+func TestReconcileManagedSSHKeyRejectsSymlink(t *testing.T) {
+	directory := t.TempDir()
+	target := filepath.Join(directory, "target")
+	if err := os.WriteFile(target, []byte("preserve me"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Symlink(target, filepath.Join(directory, "authorized_keys")); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := reconcileManagedSSHKey(directory, ""); err == nil {
+		t.Fatal("expected symlink to be rejected")
+	}
+}

internal/tasks/tasks.go

@@ -1,16 +1,16 @@
 package tasks
 
 import (
+	"bufio"
 	"database/sql"
 	"encoding/json"
 	"fmt"
 	"log"
-	"strconv"
-	"time"
-	"os/exec"
-	"strings"
 	"os"
-	"bufio"
+	"os/exec"
+	"strconv"
+	"strings"
+	"time"
 
 	"github.com/edgebox-iot/edgeboxctl/internal/diagnostics"
 	"github.com/edgebox-iot/edgeboxctl/internal/edgeapps"
@@ -114,6 +114,9 @@ type taskSetBrowserDevPasswordArgs struct {
 	Password string `json:"password"`
 }
 
+type taskEnableSSHAccessArgs struct {
+	PublicKey string `json:"public_key"`
+}
 
 const STATUS_CREATED int = 0
 const STATUS_EXECUTING int = 1
@@ -484,6 +487,27 @@ func ExecuteTask(task Task) Task {
 			taskResult := taskDeactivateBrowserDev()
 			task.Result = sql.NullString{String: taskResult, Valid: true}
 
+		case "enable_ssh_access":
+			log.Println("Installing dashboard-managed SSH public key...")
+			var args taskEnableSSHAccessArgs
+			if err := json.Unmarshal([]byte(task.Args.String), &args); err != nil {
+				task.Result = sql.NullString{String: "invalid SSH access task arguments", Valid: false}
+			} else if taskResult, err := taskEnableSSHAccess(args); err != nil {
+				log.Printf("Error enabling SSH access: %s", err)
+				task.Result = sql.NullString{String: err.Error(), Valid: false}
+			} else {
+				task.Result = sql.NullString{String: taskResult, Valid: true}
+			}
+
+		case "disable_ssh_access":
+			log.Println("Removing dashboard-managed SSH public key...")
+			if taskResult, err := taskDisableSSHAccess(); err != nil {
+				log.Printf("Error disabling SSH access: %s", err)
+				task.Result = sql.NullString{String: err.Error(), Valid: false}
+			} else {
+				task.Result = sql.NullString{String: taskResult, Valid: true}
+			}
+
 		}
 
 	}
@@ -507,7 +531,11 @@ func ExecuteTask(task Task) Task {
 
 	} else {
 		fmt.Println("Error executing task with result: " + task.Result.String)
-		_, err = statement.Exec(STATUS_ERROR, "Error", formatedDatetime, strconv.Itoa(task.ID)) // Execute SQL Statement with Error info
+		errorResult := task.Result.String
+		if errorResult == "" {
+			errorResult = "Error"
+		}
+		_, err = statement.Exec(STATUS_ERROR, errorResult, formatedDatetime, strconv.Itoa(task.ID)) // Execute SQL Statement with Error info
 		if err != nil {
 			log.Fatal(err.Error())
 		}
@@ -756,7 +784,6 @@ func taskBackup() string {
 	fmt.Println(key_secret_name)
 	os.Setenv(key_secret_name, backup_repository_secret_access_key)
 
-
 	utils.WriteOption("BACKUP_IS_WORKING", "1")
 
 	// ...	This backs up the restic repository
@@ -819,7 +846,6 @@ func taskRestoreBackup() string {
 	fmt.Println(key_secret_name)
 	os.Setenv(key_secret_name, backup_repository_secret_access_key)
 
-
 	utils.WriteOption("BACKUP_IS_WORKING", "1")
 
 	fmt.Println("Stopping All EdgeApps")
@@ -1302,7 +1328,6 @@ func taskSetEdgeAppOptions(args taskSetEdgeAppOptionsArgs) string {
 	// Id is the edgeapp id
 	appID := args.ID
 
-
 	// Open the file to write the options,
 	// it is an env file in /home/system/components/apps/<app_id>/edgeapp.env
 
@@ -1353,7 +1378,6 @@ func taskSetEdgeAppBasicAuth(args taskSetEdgeAppBasicAuthArgs) string {
 	// Id is the edgeapp id
 	appID := args.ID
 
-
 	// Open the file to write the options,
 	// it is an env file in /home/system/components/apps/<app_id>/auth.env