feat: health check configuration and worker engine (Phase 3+4)

- Added health_check_poller.rs: periodic service/HTTP health checks
- Added pre-patch health gate in job_executor.rs
- Added waiting_health_check job status (migration 008)
- Added health_check_status to HostSummary and hosts API
- Added health check types and API functions to frontend
- Added health check UI section to HostDetailPage
- Added health check status indicators to HostsPage and PatchDeploymentPage
- Added serde default for health_check_poll_interval_secs
- Fixed missing AgentClient import in health_check_poller.rs
- Fixed missing ws_relay import in main.rs
- Fixed missing closing paren in retry_pending_jobs SQL
- Added ReadWritePaths for /etc/patch-manager/keys in systemd services

crates/pm-core/src/audit.rs

@@ -47,6 +47,9 @@ pub enum AuditAction {
     PatchJobCompleted,
     PatchJobFailed,
     MaintenanceWindowReminder,
+    HealthCheckCreated,
+    HealthCheckUpdated,
+    HealthCheckDeleted,
 }
 
 impl AuditAction {
@@ -80,6 +83,9 @@ impl AuditAction {
             Self::PatchJobCompleted => "patch_job_completed",
             Self::PatchJobFailed => "patch_job_failed",
             Self::MaintenanceWindowReminder => "maintenance_window_reminder",
+            Self::HealthCheckCreated => "health_check_created",
+            Self::HealthCheckUpdated => "health_check_updated",
+            Self::HealthCheckDeleted => "health_check_deleted",
         }
     }
 }

crates/pm-core/src/config.rs

@@ -39,6 +39,9 @@ pub struct WorkerConfig {
     pub health_poll_interval_secs: u64,
     /// Patch data poll interval in seconds (default: 1800 = 30 min)
     pub patch_poll_interval_secs: u64,
+    /// Health check poll interval in seconds (default: 300 = 5 min)
+    #[serde(default = "default_health_check_poll_interval")]
+    pub health_check_poll_interval_secs: u64,
     /// Maximum concurrent agent calls
     pub max_concurrent_agent_calls: usize,
     /// Worker heartbeat interval in seconds
@@ -98,6 +101,8 @@ impl AppConfig {
     }
 }
 
+fn default_health_check_poll_interval() -> u64 { 300 }
+
 impl Default for AppConfig {
     fn default() -> Self {
         Self {
@@ -115,6 +120,7 @@ impl Default for AppConfig {
             worker: WorkerConfig {
                 health_poll_interval_secs: 300,
                 patch_poll_interval_secs: 1800,
+                health_check_poll_interval_secs: 300,
                 max_concurrent_agent_calls: 64,
                 heartbeat_interval_secs: 30,
                 ws_relay_poll_interval_secs: 10,

crates/pm-core/src/crypto.rs

@@ -0,0 +1,80 @@
+//! AES-256-GCM encryption for sensitive health check credentials.
+//!
+//! Uses a per-install key stored at `/etc/patch-manager/keys/health-check.key`.
+
+use aes_gcm::{
+    aead::{Aead, KeyInit, OsRng},
+    Aes256Gcm, Nonce,
+};
+use rand::RngCore;
+use std::fs;
+use std::path::Path;
+
+pub const KEY_PATH: &str = "/etc/patch-manager/keys/health-check.key";
+
+/// Load or create the per-install encryption key.
+/// If the key file doesn't exist, generates a new 256-bit key and saves it.
+pub fn load_or_create_key(path: &Path) -> Result<[u8; 32], CryptoError> {
+    if path.exists() {
+        let key_bytes = fs::read(path).map_err(CryptoError::Io)?;
+        if key_bytes.len() != 32 {
+            return Err(CryptoError::InvalidKeyLength(key_bytes.len()));
+        }
+        let mut key = [0u8; 32];
+        key.copy_from_slice(&key_bytes);
+        Ok(key)
+    } else {
+        let mut key = [0u8; 32];
+        OsRng.fill_bytes(&mut key);
+        if let Some(parent) = path.parent() {
+            fs::create_dir_all(parent).map_err(CryptoError::Io)?;
+        }
+        fs::write(path, &key).map_err(CryptoError::Io)?;
+        // Set permissions to 0600 (owner read/write only)
+        #[cfg(unix)]
+        {
+            use std::os::unix::fs::PermissionsExt;
+            fs::set_permissions(path, fs::Permissions::from_mode(0o600))
+                .map_err(CryptoError::Io)?;
+        }
+        Ok(key)
+    }
+}
+
+/// Encrypt plaintext with AES-256-GCM. Returns (ciphertext, nonce).
+pub fn encrypt(plaintext: &str, key: &[u8; 32]) -> Result<(Vec<u8>, Vec<u8>), CryptoError> {
+    let cipher = Aes256Gcm::new_from_slice(key).map_err(|e| CryptoError::KeyInit(e.to_string()))?;
+    let mut nonce_bytes = [0u8; 12];
+    OsRng.fill_bytes(&mut nonce_bytes);
+    let nonce = Nonce::from_slice(&nonce_bytes);
+    let ciphertext = cipher
+        .encrypt(nonce, plaintext.as_bytes())
+        .map_err(|_| CryptoError::EncryptionFailed)?;
+    Ok((ciphertext, nonce_bytes.to_vec()))
+}
+
+/// Decrypt AES-256-GCM ciphertext with the given nonce.
+pub fn decrypt(ciphertext: &[u8], nonce: &[u8], key: &[u8; 32]) -> Result<String, CryptoError> {
+    let cipher = Aes256Gcm::new_from_slice(key).map_err(|e| CryptoError::KeyInit(e.to_string()))?;
+    let nonce = Nonce::from_slice(nonce);
+    let plaintext = cipher
+        .decrypt(nonce, ciphertext)
+        .map_err(|_| CryptoError::DecryptionFailed)?;
+    String::from_utf8(plaintext).map_err(CryptoError::Utf8)
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum CryptoError {
+    #[error("IO error: {0}")]
+    Io(#[from] std::io::Error),
+    #[error("Invalid key length: expected 32 bytes, got {0}")]
+    InvalidKeyLength(usize),
+    #[error("Key init error: {0}")]
+    KeyInit(String),
+    #[error("Encryption failed")]
+    EncryptionFailed,
+    #[error("Decryption failed")]
+    DecryptionFailed,
+    #[error("UTF-8 error: {0}")]
+    Utf8(#[from] std::string::FromUtf8Error),
+}

crates/pm-core/src/lib.rs

@@ -1,5 +1,6 @@
 pub mod audit;
 pub mod config;
+pub mod crypto;
 pub mod db;
 pub mod error;
 pub mod logging;
@@ -8,11 +9,14 @@ pub mod request_id;
 
 // Re-export commonly used types
 pub use config::AppConfig;
+pub use crypto::{CryptoError, KEY_PATH, decrypt, encrypt, load_or_create_key};
 pub use error::{AppError, ErrorResponse};
 pub use models::{
-    AuthProvider, CreateGroupRequest, CreateHostRequest, CreateUserRequest, DiscoveryCidrRequest,
-    DiscoveryResult, Group, Host, HostHealthStatus, HostSummary, RegisterDiscoveredRequest,
-    UpdateGroupRequest, UpdateUserRequest, User, UserRole as DbUserRole,
+    AuthProvider, CreateGroupRequest, CreateHealthCheckRequest, CreateHostRequest,
+    CreateUserRequest, DiscoveryCidrRequest, DiscoveryResult, Group, HealthCheck,
+    HealthCheckResult, HealthCheckWithResult, Host, HostHealthStatus, HostSummary,
+    RegisterDiscoveredRequest, UpdateGroupRequest, UpdateHealthCheckRequest, UpdateUserRequest,
+    User, UserRole as DbUserRole,
 };
 
 // Re-export audit integrity types

crates/pm-core/src/models.rs

@@ -113,9 +113,79 @@ pub struct HostSummary {
     pub health_status: HostHealthStatus,
     pub agent_version: Option<String>,
     pub patches_missing: i32,
+    pub health_check_status: Option<String>,
     pub registered_at: DateTime<Utc>,
 }
 
+// ============================================================
+// Health Checks
+// ============================================================
+
+#[derive(Debug, Clone, Serialize, Deserialize, FromRow)]
+pub struct HealthCheck {
+    pub id: Uuid,
+    pub host_id: Uuid,
+    pub name: String,
+    pub check_type: String, // "service" or "http"
+    pub enabled: bool,
+    // Service check fields
+    pub service_name: Option<String>,
+    // HTTP check fields
+    pub url: Option<String>,
+    pub expected_body: Option<String>,
+    pub ignore_cert_errors: bool,
+    pub basic_auth_user: Option<String>,
+    // basic_auth_pass_encrypted and nonce NOT exposed in API responses
+    pub created_at: DateTime<Utc>,
+    pub updated_at: DateTime<Utc>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct HealthCheckWithResult {
+    #[serde(flatten)]
+    pub check: HealthCheck,
+    pub last_result: Option<HealthCheckResult>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, FromRow)]
+pub struct HealthCheckResult {
+    pub id: Uuid,
+    pub check_id: Uuid,
+    pub healthy: bool,
+    pub detail: Option<String>,
+    pub latency_ms: Option<i32>,
+    pub checked_at: DateTime<Utc>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct CreateHealthCheckRequest {
+    pub name: String,
+    pub check_type: String, // "service" or "http"
+    pub service_name: Option<String>,
+    pub url: Option<String>,
+    pub expected_body: Option<String>,
+    #[serde(default = "default_true")]
+    pub ignore_cert_errors: bool,
+    pub basic_auth_user: Option<String>,
+    pub basic_auth_pass: Option<String>, // plaintext in request, encrypted before storage
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct UpdateHealthCheckRequest {
+    pub name: Option<String>,
+    pub enabled: Option<bool>,
+    pub service_name: Option<String>,
+    pub url: Option<String>,
+    pub expected_body: Option<String>,
+    pub ignore_cert_errors: Option<bool>,
+    pub basic_auth_user: Option<String>,
+    pub basic_auth_pass: Option<String>, // if provided, re-encrypt
+}
+
+fn default_true() -> bool {
+    true
+}
+
 // ============================================================
 // Group
 // ============================================================