Update json2haproxy.py

feat: Implement OWASP CRS to HAProxy WAF conversion with enhanced features

This commit introduces significant improvements to the script for converting OWASP Core Rule Set (CRS) rules into HAProxy Web Application Firewall (WAF) configurations.

Key changes include:

- **Expanded Operator Mapping:** Added more comprehensive mappings between ModSecurity operators and HAProxy equivalents, improving the translation of OWASP rules.

- **Location-Based ACLs:** Implemented support for inspecting different request parameters (User-Agent, Request-URI, Host, etc.) based on the `location` field in the JSON rules, increasing the WAF's coverage.

- **Rule Prioritization:** Introduced rule prioritization based on severity (high, medium, low), allowing for different actions (deny, log, tarpit) to be triggered based on the assessed risk.

- **Improved Regex Handling:** Enhanced regex validation to identify and skip overly complex or invalid patterns, preventing performance issues and potential errors.

- **Clearer ACL Logic:** Restructured the generated `waf.acl` file for better organization, separating ACL definitions from deny logic and grouping rules by request parameter location.

- **Detailed Logging:** Improved logging to provide more specific information about skipped rules, invalid patterns, and other issues, aiding in debugging and configuration.

- **Integer Comparison:** Added capability to use http-request to perform integer comparison instead of strings in the rules.

These enhancements result in a more effective, maintainable, and configurable HAProxy WAF implementation based on the OWASP CRS.

Please note that thorough testing and tuning are still crucial to ensure the WAF is working correctly and not causing false positives.

This commit addresses the following issues:

- Addresses overly aggressive rules causing false positives.
- Implements missing support for ModSecurity operators.
- Enables inspection of request parameters beyond the User-Agent header.
- Provides a more organized and maintainable HAProxy WAF configuration.

json2haproxy.py

@@ -3,7 +3,7 @@ import json
 import re
 import logging
 from pathlib import Path
-from typing import List, Dict, Optional
+from typing import List, Dict, Optional, Tuple
 from functools import lru_cache
 
 # Configure logging
@@ -17,30 +17,34 @@ logging.basicConfig(
 OUTPUT_DIR = Path(os.getenv("OUTPUT_DIR", "waf_patterns/haproxy/"))  # Output directory
 INPUT_FILE = Path(os.getenv("INPUT_FILE", "owasp_rules.json"))  # Input JSON file
 
-UNSUPPORTED_PATTERNS = ["@pmFromFile", "!@eq", "!@within", "@lt", "@ge", "@gt", "@eq"]
+UNSUPPORTED_PATTERNS = ["@pmFromFile", "@detectSQLi", "@validateByteRange"] # Add more unsupported patterns
+
+# Operator mapping (ModSecurity to HAProxy) - Added more mappings
+OPERATOR_MAP = {
+    "@streq": "str -m str",
+    "@ipMatch": "src_ip",
+    "@endsWith": "str -m end",
+    "@contains": "str -m sub",
+    "!@eq": "str -m !str",  # Handle negation
+    "!@within": "str -m !reg",  # Approximate !@within (requires regex)
+    "@lt": "int <",
+    "@ge": "int >=",
+    "@gt": "int >",
+    "@eq": "int =="
+}
+
 
 def load_owasp_rules(file_path: Path) -> List[Dict]:
     """
     Load OWASP rules from a JSON file.
-    
-    Args:
-        file_path (Path): Path to the JSON file containing OWASP rules.
-    
-    Returns:
-        List[Dict]: List of OWASP rules.
-    
-    Raises:
-        FileNotFoundError: If the input file is not found.
-        json.JSONDecodeError: If the JSON file is invalid.
-        Exception: For any other errors during file loading.
     """
     try:
         with open(file_path, "r") as f:
             return json.load(f)
-    except FileNotFoundError:
+    except FileNotFoundError as e:
         logging.error(f"[!] Input file not found: {file_path}")
         raise
-    except json.JSONDecodeError:
+    except json.JSONDecodeError as e:
         logging.error(f"[!] Invalid JSON in file: {file_path}")
         raise
     except Exception as e:
@@ -50,46 +54,58 @@ def load_owasp_rules(file_path: Path) -> List[Dict]:
 @lru_cache(maxsize=None)
 def validate_regex(pattern: str) -> bool:
     """
-    Validate regex pattern for HAProxy.
+    Validate regex pattern for HAProxy.  Added complexity check
-    
-    Args:
-        pattern (str): Regex pattern to validate.
-    
-    Returns:
-        bool: True if the regex is valid, False otherwise.
     """
     try:
+        # Simple complexity check (can be improved)
+        if pattern.count(".*") > 5:
+            logging.warning(f"[!] Regex too complex: {pattern}")
+            return False
+
         re.compile(pattern)
         return True
     except re.error as e:
         logging.warning(f"[!] Invalid regex: {pattern} - {e}")
         return False
 
-def sanitize_pattern(pattern: str) -> Optional[str]:
+def sanitize_pattern(pattern: str) -> Tuple[Optional[str], str, Optional[str]]:
     """
-    Sanitize unsupported patterns and directives for HAProxy ACLs.
+    Sanitize and convert ModSecurity patterns to HAProxy.
-    
+    Returns: sanitized pattern, ACL type, and transformed pattern (if needed)
-    Args:
-        pattern (str): The pattern to sanitize.
-    
-    Returns:
-        Optional[str]: The sanitized pattern, or None if the pattern is unsupported.
     """
-    # Skip unsupported patterns
+    acl_type = "hdr_reg"  # Default to regex matching
-    if any(directive in pattern for directive in UNSUPPORTED_PATTERNS):
+    transformed_pattern = None # optional transformation
-        logging.warning(f"[!] Skipping unsupported pattern: {pattern}")
+    original_pattern = pattern # store original for logging
-        return None
 
-    # Remove @rx (regex indicator) for HAProxy compatibility
+    for modsecurity_op, haproxy_op in OPERATOR_MAP.items():
+        if pattern.startswith(modsecurity_op):
+             # if it is an integer comparison we will want a different ACL
+             if haproxy_op.startswith("int"):
+                 acl_type = "int"
+                 pattern = pattern.replace(modsecurity_op, haproxy_op).strip()
+                 return pattern, acl_type, transformed_pattern
+
+             acl_type = "hdr_sub"  # String matching
+             pattern = pattern.replace(modsecurity_op, haproxy_op).strip()
+             return pattern, acl_type, transformed_pattern
+
+    # Skip unsupported patterns with more detailed logging
+    for directive in UNSUPPORTED_PATTERNS:
+        if directive in pattern:
+            logging.warning(f"[!] Skipping unsupported pattern (contains {directive}): {pattern}")
+            return None, acl_type, transformed_pattern # Indicate skip
+
+    if "@rx" in pattern: # only remove @rx for REGEX cases to reduce bugs
+        acl_type = "hdr_reg"
         pattern = pattern.replace("@rx ", "").strip()
 
         # Remove case-insensitive flag (?i) as HAProxy uses -i for that
         pattern = re.sub(r"\(\?i\)", "", pattern)
 
-    # Convert &dollar; to \$
+        # Convert $ to \$
-    pattern = pattern.replace("&dollar;", r"\$")
+        pattern = pattern.replace("$", r"\$")
 
-    # Convert &lbrace; or &lcub; to {
+        # Convert { or { to {
         pattern = re.sub(r"&l(?:brace|cub);?", r"{", pattern)
         pattern = re.sub(r"&r(?:brace|cub);?", r"}", pattern)
 
@@ -99,49 +115,125 @@ def sanitize_pattern(pattern: str) -> Optional[str]:
 
         # Replace non-capturing groups (?:...) with capturing groups (...)
         pattern = re.sub(r"\(\?:", "(", pattern)
+    else:
+        acl_type = "hdr_sub" # assume it is a normal comparison
+
+    return pattern, acl_type, transformed_pattern # indicate success
 
-    return pattern
 
 def generate_haproxy_conf(rules: List[Dict]) -> None:
     """
-    Generate HAProxy ACL rules from OWASP rules.
+    Generate HAProxy ACL rules from OWASP rules with prioritization and parameter selection.
-    
-    Args:
-        rules (List[Dict]): List of OWASP rules.
-    
-    Raises:
-        Exception: If there is an error generating the HAProxy configuration.
     """
     try:
-        # Ensure the output directory exists
         OUTPUT_DIR.mkdir(parents=True, exist_ok=True)
         logging.info(f"[+] Created or verified directory: {OUTPUT_DIR}")
 
-        # Define the output file path
         config_file = OUTPUT_DIR / "waf.acl"
-        unique_rules = set()
+        acl_rules = {}  # Dict to store ACL rule definitions based on 'location'
+        all_acl_names = [] # Store a full list of acl names for final deny
+        # Initialize lists for different deny actions
+        deny_high = []
+        log_medium = []
+        tarpit_low = []
+        all_deny_actions = {
+            "deny_high" : deny_high,
+            "log_medium" : log_medium,
+            "tarpit_low" : tarpit_low
+        }
 
-        # Write HAProxy ACL rules to the file
+        unique_rules = set() # Prevent duplication rules
-        with open(config_file, "w") as f:
+
-            f.write("# HAProxy WAF ACL rules\n\n")
+
+        # Process each rule
         for rule in rules:
             try:
+                rule_id = rule.get("id", "no_id")  # Get ID, default "no_id"
                 category = rule["category"].lower()
+                location = rule.get("location", "User-Agent")  # Get location, default User-Agent
                 pattern = rule["pattern"]
+                severity = rule.get("severity", "medium").lower()  # severity for different actions
+
+                sanitized_pattern, acl_type, transformed_pattern = sanitize_pattern(pattern)
 
-                    sanitized_pattern = sanitize_pattern(pattern)
                 if sanitized_pattern and validate_regex(sanitized_pattern):
-                        if (category, sanitized_pattern) not in unique_rules:
+                    acl_name = f"block_{category}_{rule_id}"  # Unique ACL name including ID
-                            f.write(f"acl block_{category} hdr_sub(User-Agent) -i {sanitized_pattern}\n")
+
-                            f.write(f"http-request deny if block_{category}\n\n")
+                    if acl_name not in all_acl_names:
-                            unique_rules.add((category, sanitized_pattern))
+                        all_acl_names.append(acl_name)  # Add to the list of ACLs
+
+                        # Build the ACL rule string based on the 'location'
+                        acl_rule_string = None # Set the initial state
+                        if acl_type == 'int': # if it is int then we want 'http-request' instead 'acl'
+                            acl_rule_string = f"http-request  if {{ {location} {sanitized_pattern} }}"
+                        elif location == "Request-URI":
+                            acl_rule_string = f"acl {acl_name} path_reg -i {sanitized_pattern}"
+                        elif location == "Query-String":
+                            acl_rule_string = f"acl {acl_name} query_reg -i {sanitized_pattern}"
+                        elif location == "Host":
+                            acl_rule_string = f"acl {acl_name} hdr_reg(Host) -i {sanitized_pattern}"
+                        elif location == "Content-Type":
+                            acl_rule_string = f"acl {acl_name} hdr_reg(Content-Type) -i {sanitized_pattern}"
+                        elif location == "Referer":
+                            acl_rule_string = f"acl {acl_name} hdr_reg(Referer) -i {sanitized_pattern}"
+                        else: # Default case: User-Agent
+                            if acl_type == 'hdr_reg':
+                                acl_rule_string = f"acl {acl_name} hdr_reg(User-Agent) -i {sanitized_pattern}"
+                            else: # hdr_sub
+                                acl_rule_string = f"acl {acl_name} hdr_sub(User-Agent) -i {sanitized_pattern}"
+
+                        if acl_rule_string:  # Check that a rule string has a value.
+                            # Get the corresponding action based on severity
+                            if severity == "high":
+                                deny_high.append(acl_name)
+                            elif severity == "medium":
+                                log_medium.append(acl_name)
+                            elif severity == "low":
+                                tarpit_low.append(acl_name)
+
+                            if location not in acl_rules:
+                                acl_rules[location] = []  # Initialize if it is not already existent
+
+                            acl_rules[location].append(acl_rule_string) # Append rule
                 else:
                     logging.warning(f"[!] Skipping invalid rule: {pattern}")
+
             except KeyError as e:
                 logging.warning(f"[!] Skipping invalid rule (missing key: {e}): {rule}")
                 continue
 
+        # Write HAProxy ACL rules to the file
+        with open(config_file, "w") as f:
+            f.write("# HAProxy WAF ACL rules\n\n")
+
+            # Write all ACL definitions by location
+            for location, rules in acl_rules.items():
+                f.write(f"# Rules for {location}\n")
+                for acl_rule in rules:
+                    f.write(f"{acl_rule}\n")
+                f.write("\n")
+
+            f.write("\n")
+            # Add all the actions based on rules
+            for action, rules in all_deny_actions.items():
+                action_string = 'deny' if action == "deny_high" else 'tarpit' if action == "tarpit_low" else 'log'
+                # if it is NOT a deny action then we will want http-request instead acl
+                if action == "deny_high":
+                    f.write(f"# High Severity Rules (Deny)\n")
+                    if rules:
+                        f.write(f"http-request {action_string} if {' or '.join(rules)}\n")
+                elif action == "log_medium":
+                    f.write(f"# Medium Severity Rules (Log)\n")
+                    if rules:
+                        f.write(f"http-request {action_string} if {' or '.join(rules)}\n")
+                else:
+                    f.write(f"# Low Severity Rules (Tarpit)\n")
+                    if rules:
+                        f.write(f"http-request {action_string} if {' or '.join(rules)}\n")
+                f.write("\n")
+
         logging.info(f"[+] HAProxy WAF rules generated at {config_file}")
+
     except Exception as e:
         logging.error(f"[!] Error generating HAProxy configuration: {e}")
         raise