# ADR-020: Audit Trail para Compliance

**Status**: Accepted | Implemented
**Date**: 2024-11-01
**Deciders**: Security & Compliance Team
**Technical Story**: Logging all significant workflow events for compliance and incident investigation

---

## Decision

Implementar **comprehensive audit trail** con logging de todos los workflow events, queryable por workflow/actor/tipo.

---

## Rationale

1. **Compliance**: Regulaciones requieren audit trail (HIPAA, SOC2, etc.)
2. **Incident Investigation**: Reconstruir qué pasó cuando
3. **Event Sourcing Ready**: Audit trail puede ser base para event sourcing architecture
4. **User Accountability**: Track quién hizo qué cuándo

---

## Alternatives Considered

### ❌ Logs Only (No Structured Audit)
- **Pros**: Simple
- **Cons**: Hard to query, no compliance value

### ❌ Application-Embedded Logging
- **Pros**: Close to business logic
- **Cons**: Fragmented, easy to miss events

### ✅ Centralized Audit Trail (CHOSEN)
- Queryable, compliant, comprehensive

---

## Trade-offs

**Pros**:
- ✅ Queryable by workflow, actor, event type
- ✅ Compliance-ready
- ✅ Incident investigation support
- ✅ Event sourcing ready

**Cons**:
- ⚠️ Storage overhead (every event logged)
- ⚠️ Query performance depends on indexing
- ⚠️ Retention policy tradeoff

---

## Implementation

**Audit Event Model**:
```rust
// crates/vapora-backend/src/audit.rs

pub struct AuditEvent {
    pub id: String,
    pub timestamp: DateTime<Utc>,
    pub actor: String,                // User ID or service name
    pub action: AuditAction,          // Create, Update, Delete, Execute
    pub resource_type: String,        // Project, Task, Agent, Workflow
    pub resource_id: String,
    pub details: serde_json::Value,   // Action-specific details
    pub outcome: AuditOutcome,        // Success, Failure, PartialSuccess
    pub error: Option<String>,        // Error message if failed
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum AuditAction {
    Create,
    Update,
    Delete,
    Execute,
    Assign,
    Complete,
    Override,
    QuerySecret,
    ViewAudit,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum AuditOutcome {
    Success,
    Failure,
    PartialSuccess,
}
```

**Logging Events**:
```rust
pub async fn log_event(
    db: &Surreal<Ws>,
    actor: &str,
    action: AuditAction,
    resource_type: &str,
    resource_id: &str,
    details: serde_json::Value,
    outcome: AuditOutcome,
) -> Result<String> {
    let event = AuditEvent {
        id: uuid::Uuid::new_v4().to_string(),
        timestamp: Utc::now(),
        actor: actor.to_string(),
        action,
        resource_type: resource_type.to_string(),
        resource_id: resource_id.to_string(),
        details,
        outcome,
        error: None,
    };

    let id = db
        .create("audit_events")
        .content(&event)
        .await?
        .id
        .unwrap();

    Ok(id)
}

pub async fn log_event_with_error(
    db: &Surreal<Ws>,
    actor: &str,
    action: AuditAction,
    resource_type: &str,
    resource_id: &str,
    error: String,
) -> Result<String> {
    let event = AuditEvent {
        id: uuid::Uuid::new_v4().to_string(),
        timestamp: Utc::now(),
        actor: actor.to_string(),
        action,
        resource_type: resource_type.to_string(),
        resource_id: resource_id.to_string(),
        details: json!({}),
        outcome: AuditOutcome::Failure,
        error: Some(error),
    };

    let id = db
        .create("audit_events")
        .content(&event)
        .await?
        .id
        .unwrap();

    Ok(id)
}
```

**Audit Integration in Handlers**:
```rust
// In task creation handler
pub async fn create_task(
    State(app_state): State<AppState>,
    Path(project_id): Path<String>,
    Json(req): Json<CreateTaskRequest>,
) -> Result<Json<Task>, ApiError> {
    let user = get_current_user()?;

    // Create task
    let task = app_state
        .task_service
        .create_task(&user.tenant_id, &project_id, &req)
        .await?;

    // Log audit event
    app_state.audit_log(
        &user.id,
        AuditAction::Create,
        "task",
        &task.id,
        json!({
            "project_id": &project_id,
            "title": &task.title,
            "priority": &task.priority,
        }),
        AuditOutcome::Success,
    ).await.ok();  // Don't fail if audit logging fails

    Ok(Json(task))
}
```

**Querying Audit Trail**:
```rust
pub async fn query_audit_trail(
    db: &Surreal<Ws>,
    filters: AuditQuery,
) -> Result<Vec<AuditEvent>> {
    let mut query = String::from(
        "SELECT * FROM audit_events WHERE 1=1"
    );

    if let Some(workflow_id) = filters.workflow_id {
        query.push_str(&format!(" AND resource_id = '{}'", workflow_id));
    }
    if let Some(actor) = filters.actor {
        query.push_str(&format!(" AND actor = '{}'", actor));
    }
    if let Some(action) = filters.action {
        query.push_str(&format!(" AND action = '{:?}'", action));
    }
    if let Some(since) = filters.since {
        query.push_str(&format!(" AND timestamp > '{}'", since));
    }

    query.push_str(" ORDER BY timestamp DESC LIMIT 1000");

    let events = db.query(&query).await?
        .take::<Vec<AuditEvent>>(0)?
        .unwrap_or_default();

    Ok(events)
}
```

**Compliance Report**:
```rust
pub async fn generate_compliance_report(
    db: &Surreal<Ws>,
    start_date: Date,
    end_date: Date,
) -> Result<ComplianceReport> {
    // Query all events in date range
    let events = db.query(
        "SELECT COUNT() as event_count, actor, action \
         FROM audit_events \
         WHERE timestamp >= $1 AND timestamp < $2 \
         GROUP BY actor, action"
    )
    .bind((start_date, end_date))
    .await?;

    // Generate report with statistics
    Ok(ComplianceReport {
        period: (start_date, end_date),
        total_events: events.len(),
        unique_actors: /* count unique */,
        actions_by_type: /* aggregate */,
        failures: /* filter failures */,
    })
}
```

**Key Files**:
- `/crates/vapora-backend/src/audit.rs` (audit implementation)
- `/crates/vapora-backend/src/api/` (audit logging in handlers)
- `/crates/vapora-backend/src/services/` (audit logging in services)

---

## Verification

```bash
# Test audit event creation
cargo test -p vapora-backend test_audit_event_logging

# Test audit trail querying
cargo test -p vapora-backend test_query_audit_trail

# Test filtering by actor/action/resource
cargo test -p vapora-backend test_audit_filtering

# Test error logging
cargo test -p vapora-backend test_audit_error_logging

# Integration: full workflow with audit
cargo test -p vapora-backend test_audit_full_workflow

# Compliance report generation
cargo test -p vapora-backend test_compliance_report_generation
```

**Expected Output**:
- All significant events logged
- Queryable by workflow/actor/action
- Timestamps accurate
- Errors captured with messages
- Compliance reports generated correctly

---

## Consequences

### Data Management
- Audit events retained per compliance policy
- Separate archive for long-term retention
- Immutable logs (append-only)

### Performance
- Audit logging should not block main operation
- Async logging to avoid latency impact
- Indexes on (resource_id, timestamp) for queries

### Privacy
- Sensitive data (passwords, keys) not logged
- PII handled per data protection regulations
- Access to audit trail restricted

### Compliance
- Supports HIPAA, SOC2, GDPR requirements
- Incident investigation support
- Regulatory audit trail available

---

## References

- `/crates/vapora-backend/src/audit.rs` (implementation)
- ADR-011 (SecretumVault - secrets management)
- ADR-025 (Multi-Tenancy - tenant isolation)

---

**Related ADRs**: ADR-011 (Secrets), ADR-025 (Multi-Tenancy), ADR-009 (Istio)