feat(mail/delivery): add error-count based blocking to rate limiter; improve test SMTP server port selection; add tsbuild scripts and devDependency; remove stale backup file

ts/mail/delivery/classes.ratelimiter.ts

@@ -29,15 +29,21 @@ export interface IRateLimitConfig {
 interface TokenBucket {
   /** Current number of tokens */
   tokens: number;
-  
+
   /** Last time tokens were refilled */
   lastRefill: number;
-  
+
   /** Total allowed requests */
   allowed: number;
-  
+
   /** Total denied requests */
   denied: number;
+
+  /** Error count for blocking decisions */
+  errors: number;
+
+  /** Timestamp of first error in current window */
+  firstErrorTime: number;
 }
 
 /**
@@ -74,7 +80,9 @@ export class RateLimiter {
       tokens: this.config.initialTokens,
       lastRefill: Date.now(),
       allowed: 0,
-      denied: 0
+      denied: 0,
+      errors: 0,
+      firstErrorTime: 0
     };
     
     // Log initialization
@@ -196,7 +204,9 @@ export class RateLimiter {
         tokens: this.config.initialTokens,
         lastRefill: Date.now(),
         allowed: 0,
-        denied: 0
+        denied: 0,
+        errors: 0,
+        firstErrorTime: 0
       });
     }
     
@@ -266,16 +276,50 @@ export class RateLimiter {
   public cleanup(maxAge: number = 24 * 60 * 60 * 1000): void {
     const now = Date.now();
     let removed = 0;
-    
+
     for (const [key, bucket] of this.buckets.entries()) {
       if (now - bucket.lastRefill > maxAge) {
         this.buckets.delete(key);
         removed++;
       }
     }
-    
+
     if (removed > 0) {
       logger.log('debug', `Cleaned up ${removed} stale rate limit buckets`);
     }
   }
+
+  /**
+   * Record an error for a key (e.g., IP address) and determine if blocking is needed
+   * RFC 5321 Section 4.5.4.1 suggests limiting errors to prevent abuse
+   *
+   * @param key Key to record error for (typically an IP address)
+   * @param errorWindow Time window for error tracking in ms (default: 5 minutes)
+   * @param errorThreshold Maximum errors before blocking (default: 10)
+   * @returns true if the key should be blocked due to excessive errors
+   */
+  public recordError(key: string, errorWindow: number = 5 * 60 * 1000, errorThreshold: number = 10): boolean {
+    const bucket = this.getBucket(key);
+    const now = Date.now();
+
+    // Reset error count if the time window has expired
+    if (bucket.firstErrorTime === 0 || now - bucket.firstErrorTime > errorWindow) {
+      bucket.errors = 0;
+      bucket.firstErrorTime = now;
+    }
+
+    // Increment error count
+    bucket.errors++;
+
+    // Log error tracking
+    logger.log('debug', `Error recorded for ${key}: ${bucket.errors}/${errorThreshold} in window`);
+
+    // Check if threshold exceeded
+    if (bucket.errors >= errorThreshold) {
+      logger.log('warn', `Error threshold exceeded for ${key}: ${bucket.errors} errors`);
+      return true; // Should block
+    }
+
+    return false; // Continue allowing
+  }
 }