Agent skill
linux-at-spi2
Expert in AT-SPI2 (Assistive Technology Service Provider Interface) for Linux desktop automation. Specializes in accessible automation of GTK/Qt applications via D-Bus accessibility interface. HIGH-RISK skill requiring security controls for system-wide access.
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npx add-skill https://github.com/martinholovsky/claude-skills-generator/tree/main/skills/linux-at-spi2
SKILL.md
1. Overview
Risk Level: HIGH - System-wide accessibility access, D-Bus IPC, input injection
You are an expert in Linux AT-SPI2 automation with deep expertise in:
- AT-SPI2 Protocol: Accessibility object tree, interfaces, events
- D-Bus Integration: Session bus communication, interface proxies
- pyatspi2: Python bindings for AT-SPI2
- Security Controls: Process validation, permission management
Core Expertise Areas
- Accessible Objects: AtspiAccessible, roles, states, interfaces
- D-Bus Protocol: Object paths, interfaces, method calls
- Event Monitoring: AT-SPI2 event system, callbacks
- Security: Application isolation, audit logging
2. Core Principles
- TDD First - Write tests before implementation for all AT-SPI2 interactions
- Performance Aware - Optimize tree traversals, cache nodes, filter events
- Security First - Validate targets, block sensitive apps, audit all operations
- Reliability - Enforce timeouts, handle D-Bus errors gracefully
3. Core Responsibilities
3.1 Safe Automation Principles
When performing AT-SPI2 automation:
- Validate target applications before interaction
- Block sensitive applications (password managers, terminals)
- Implement rate limiting for actions
- Log all operations for audit trails
- Enforce timeouts on D-Bus calls
3.2 Security-First Approach
Every automation operation MUST:
- Verify target application identity
- Check against blocked application list
- Validate action permissions
- Log operation with correlation ID
- Enforce timeout limits
4. Technical Foundation
4.1 AT-SPI2 Architecture
Application -> ATK/QAccessible -> AT-SPI2 Registry -> D-Bus -> Client
Key Components:
- AT-SPI2 Registry: Central daemon managing accessibility objects
- ATK Bridge: GTK accessibility implementation
- QAccessible: Qt accessibility implementation
- pyatspi2: Python client library
4.2 Essential Libraries
| Library | Purpose | Security Notes |
|---|---|---|
pyatspi2 |
Python AT-SPI2 bindings | Validate accessible objects |
gi.repository.Atspi |
GObject Introspection bindings | Check object validity |
dbus-python |
D-Bus access | Use session bus only |
5. Implementation Patterns
Pattern 1: Secure AT-SPI2 Access
import gi
gi.require_version('Atspi', '2.0')
from gi.repository import Atspi
import logging
class SecureATSPI:
"""Secure wrapper for AT-SPI2 operations."""
BLOCKED_APPS = {
'keepassxc', 'keepass2', 'bitwarden', # Password managers
'gnome-terminal', 'konsole', 'xterm', # Terminals
'gnome-keyring', 'seahorse', # Key management
'polkit-gnome-authentication-agent-1', # Auth dialogs
}
BLOCKED_ROLES = {
Atspi.Role.PASSWORD_TEXT, # Password fields
}
def __init__(self, permission_tier: str = 'read-only'):
self.permission_tier = permission_tier
self.logger = logging.getLogger('atspi.security')
self.timeout = 5000 # ms for D-Bus calls
# Initialize AT-SPI2
Atspi.init()
def get_desktop(self) -> 'Atspi.Accessible':
"""Get desktop root with timeout."""
return Atspi.get_desktop(0)
def get_application(self, name: str) -> 'Atspi.Accessible':
"""Get application accessible with validation."""
name_lower = name.lower()
# Security check
if name_lower in self.BLOCKED_APPS:
self.logger.warning('blocked_app', app=name)
raise SecurityError(f"Access to {name} is blocked")
desktop = self.get_desktop()
for i in range(desktop.get_child_count()):
app = desktop.get_child_at_index(i)
if app.get_name().lower() == name_lower:
self._audit_log('app_access', name)
return app
return None
def get_object_value(self, obj: 'Atspi.Accessible') -> str:
"""Get object value with security filtering."""
# Check for password fields
if obj.get_role() in self.BLOCKED_ROLES:
self.logger.warning('blocked_role', role=obj.get_role())
raise SecurityError("Access to password fields blocked")
# Check for sensitive names
name = obj.get_name().lower()
if any(word in name for word in ['password', 'secret', 'token']):
return '[REDACTED]'
try:
text = obj.get_text()
if text:
return text.get_text(0, text.get_character_count())
except Exception:
pass
return ''
def perform_action(self, obj: 'Atspi.Accessible', action_name: str):
"""Perform action with permission check."""
if self.permission_tier == 'read-only':
raise PermissionError("Actions require 'standard' tier")
action = obj.get_action()
if not action:
raise ValueError("Object has no actions")
# Find and perform action
for i in range(action.get_n_actions()):
if action.get_action_name(i) == action_name:
self._audit_log('action', f"{obj.get_name()}.{action_name}")
return action.do_action(i)
raise ValueError(f"Action {action_name} not found")
def _audit_log(self, event: str, detail: str):
"""Log operation for audit."""
self.logger.info(
f'atspi.{event}',
extra={
'detail': detail,
'permission_tier': self.permission_tier
}
)
Pattern 2: Element Discovery with Timeout
import time
class ElementFinder:
def __init__(self, atspi: SecureATSPI, timeout: int = 30):
self.atspi = atspi
self.timeout = timeout
def find_by_role(self, root, role, timeout=None):
timeout = timeout or self.timeout
start = time.time()
results = []
def search(obj, depth=0):
if time.time() - start > timeout:
raise TimeoutError("Search timed out")
if depth > 20: return
if obj.get_role() == role:
results.append(obj)
for i in range(obj.get_child_count()):
if child := obj.get_child_at_index(i):
search(child, depth + 1)
search(root)
return results
Pattern 3: Event Monitoring
class ATSPIEventMonitor:
"""Monitor AT-SPI2 events safely."""
ALLOWED_EVENTS = ['object:state-changed:focused', 'window:activate']
def register_handler(self, event_type: str, handler: Callable):
if event_type not in self.ALLOWED_EVENTS:
raise SecurityError(f"Event type {event_type} not allowed")
Atspi.EventListener.register_full(handler, event_type, None)
Pattern 4: Safe Text Input
def set_text_safely(obj: 'Atspi.Accessible', text: str, permission_tier: str):
if permission_tier == 'read-only':
raise PermissionError("Text input requires 'standard' tier")
if obj.get_role() == Atspi.Role.PASSWORD_TEXT:
raise SecurityError("Cannot input to password fields")
editable = obj.get_editable_text()
text_iface = obj.get_text()
editable.delete_text(0, text_iface.get_character_count())
editable.insert_text(0, text, len(text))
6. Implementation Workflow (TDD)
Step 1: Write Failing Test First
# tests/test_atspi_automation.py
import pytest
from unittest.mock import Mock, patch
class TestSecureATSPI:
def test_blocked_app_raises_security_error(self):
from automation.atspi_client import SecureATSPI, SecurityError
atspi = SecureATSPI(permission_tier='standard')
with pytest.raises(SecurityError, match="blocked"):
atspi.get_application('keepassxc')
def test_password_field_access_blocked(self):
from automation.atspi_client import SecureATSPI, SecurityError
atspi = SecureATSPI()
mock_obj = Mock()
mock_obj.get_role.return_value = 24 # PASSWORD_TEXT
with pytest.raises(SecurityError):
atspi.get_object_value(mock_obj)
def test_read_only_tier_blocks_actions(self):
from automation.atspi_client import SecureATSPI
atspi = SecureATSPI(permission_tier='read-only')
with pytest.raises(PermissionError):
atspi.perform_action(Mock(), 'click')
Step 2: Implement Minimum to Pass
Implement the security checks and validations to pass tests.
Step 3: Refactor Following Patterns
Apply caching, async patterns, and connection pooling.
Step 4: Run Full Verification
# Run all tests with coverage
pytest tests/ -v --cov=automation --cov-report=term-missing
# Run security-specific tests
pytest tests/ -k "security or blocked" -v
# Verify no password field access
pytest tests/ -k "password" -v
7. Performance Patterns
Pattern 1: Event Filtering (Reduce D-Bus Traffic)
# BAD: Register for all events
Atspi.EventListener.register_full(handler, 'object:', None)
# GOOD: Filter to specific events needed
ALLOWED_EVENTS = ['object:state-changed:focused', 'window:activate']
for event in ALLOWED_EVENTS:
Atspi.EventListener.register_full(handler, event, None)
Pattern 2: Node Caching (Avoid Repeated Lookups)
# BAD: Re-traverse tree for each query
def find_button():
desktop = Atspi.get_desktop(0)
for i in range(desktop.get_child_count()):
app = desktop.get_child_at_index(i)
# Full tree traversal every time
# GOOD: Cache frequently accessed nodes
class CachedATSPI:
def __init__(self):
self._app_cache = {}
self._cache_ttl = 5.0 # seconds
def get_application(self, name: str):
now = time.time()
if name in self._app_cache:
cached, timestamp = self._app_cache[name]
if now - timestamp < self._cache_ttl:
return cached
app = self._find_app(name)
self._app_cache[name] = (app, now)
return app
Pattern 3: Async Queries (Non-Blocking Operations)
# BAD: Blocking synchronous calls in main thread
buttons = [c for c in children if c.get_role() == PUSH_BUTTON]
# GOOD: Use executor for heavy tree traversals
async def get_all_buttons_async(app):
loop = asyncio.get_event_loop()
return await loop.run_in_executor(None, lambda: find_buttons(app))
Pattern 4: Connection Pooling (Singleton)
# BAD: Atspi.init() called per operation
# GOOD: Singleton manager
class ATSPIManager:
_instance = None
def __new__(cls):
if not cls._instance:
cls._instance = super().__new__(cls)
Atspi.init()
return cls._instance
Pattern 5: Scope Limiting (Reduce Search Space)
# BAD: Search entire desktop tree
result = search_recursive(Atspi.get_desktop(0), name)
# GOOD: Limit to specific app
app = get_application(app_name)
result = search_recursive(app, name)
# BETTER: Add role filtering
result = search_with_role(app, name, role=Atspi.Role.PUSH_BUTTON)
8. Security Standards
8.1 Critical Vulnerabilities
| Vulnerability | Severity | Mitigation |
|---|---|---|
| AT-SPI2 Registry Bypass (CWE-284) | HIGH | Validate through registry |
| D-Bus Session Hijacking (CVE-2022-42012) | HIGH | Validate D-Bus peer credentials |
| Password Field Access (CWE-200) | CRITICAL | Block PASSWORD_TEXT role |
| Input Injection (CWE-74) | HIGH | Application blocklists |
| Event Flooding (CWE-400) | MEDIUM | Rate limiting, event filtering |
8.2 Permission Tier Model
PERMISSION_TIERS = {
'read-only': {
'allowed_operations': ['get_name', 'get_role', 'get_state', 'find'],
'blocked_roles': [Atspi.Role.PASSWORD_TEXT],
'timeout': 5000,
},
'standard': {
'allowed_operations': ['*', 'do_action', 'set_text'],
'blocked_roles': [Atspi.Role.PASSWORD_TEXT],
'timeout': 10000,
},
'elevated': {
'allowed_operations': ['*'],
'blocked_apps': ['polkit', 'gnome-keyring'],
'timeout': 30000,
}
}
9. Common Mistakes
Never: Access Password Fields
# BAD: No role check
value = obj.get_text().get_text(0, -1)
# GOOD: Check role first
if obj.get_role() != Atspi.Role.PASSWORD_TEXT:
value = obj.get_text().get_text(0, -1)
Never: Skip Application Validation
# BAD: Direct access
app = desktop.get_child_at_index(0)
interact(app)
# GOOD: Validate first
if is_allowed_app(app.get_name()):
interact(app)
10. Pre-Implementation Checklist
Phase 1: Before Writing Code
- Reviewed AT-SPI2 security patterns in this skill
- Identified target applications and verified not in blocklist
- Determined required permission tier (read-only/standard/elevated)
- Wrote failing tests for security validations
- Planned caching strategy for node lookups
Phase 2: During Implementation
- Implemented application blocklist checks
- Added PASSWORD_TEXT role blocking
- Enforced timeouts on all D-Bus calls
- Applied node caching for performance
- Used event filtering (not wildcard subscriptions)
- Implemented scope limiting for searches
Phase 3: Before Committing
- All pytest tests pass with coverage > 80%
- Audit logging verified for all operations
- Rate limiting tested under load
- No security warnings in test output
- Performance verified (< 100ms for element lookups)
11. Summary
Your goal is to create AT-SPI2 automation that is:
- Secure: Application validation, role blocking, audit logging
- Reliable: Timeout enforcement, error handling
- Accessible: Respects assistive technology boundaries
Security Reminders:
- Always block access to PASSWORD_TEXT roles
- Validate applications before automation
- Enforce timeouts on all D-Bus calls
- Log all operations for audit
- Use appropriate permission tiers
References
- See
references/security-examples.md - See
references/threat-model.md - See
references/advanced-patterns.md
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