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fix: Add security and reliability improvements

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1. File locking for config operations
   - add_server_to_config() and remove_server_from_config() now use
     exclusive file locking (fcntl.LOCK_EX) to prevent race conditions
   - Prevents data loss from concurrent modifications

2. Bulk server limit
   - Add MAX_BULK_SERVERS = 10 constant
   - haproxy_add_servers() now rejects requests exceeding limit
   - Prevents potential DoS via large payloads

3. HAProxy command response validation
   - Add haproxy_cmd_checked() helper function
   - Validates responses for error indicators (No such, not found, etc.)
   - State-modifying commands now properly detect and report failures
   - Read-only commands continue using haproxy_cmd()

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
kaffa
2026-02-01 13:50:47 +00:00
parent 7985501d48
commit b8fb4e7f4a
1 changed files with 62 additions and 26 deletions
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88
mcp/server.py
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@@ -82,6 +82,7 @@ STARTUP_RETRY_COUNT = 10 # HAProxy ready check retries
STATE_MIN_COLUMNS = 19 # Minimum columns in HAProxy server state output
SOCKET_TIMEOUT = 5 # seconds for HAProxy socket connection
SOCKET_RECV_TIMEOUT = 30 # seconds for HAProxy socket recv loop
MAX_BULK_SERVERS = 10 # Max servers per bulk add call
class HaproxyError(Exception):
@@ -169,6 +170,29 @@ def haproxy_cmd(command: str) -> str:
raise HaproxyError(str(e)) from e
def haproxy_cmd_checked(command: str) -> str:
"""Send command to HAProxy and raise on error response.
Args:
command: HAProxy command to execute
Returns:
Command response
Raises:
HaproxyError: If HAProxy returns an error message
"""
result = haproxy_cmd(command)
# HAProxy returns empty string on success, error messages on failure
error_indicators = ["No such", "not found", "error", "failed", "invalid", "unknown"]
if result:
result_lower = result.lower()
for indicator in error_indicators:
if indicator.lower() in result_lower:
raise HaproxyError(f"HAProxy command failed: {result.strip()}")
return result
def reload_haproxy() -> Tuple[bool, str]:
"""Validate and reload HAProxy configuration.
@@ -485,7 +509,7 @@ def save_servers_config(config: Dict[str, Any]) -> None:
def add_server_to_config(domain: str, slot: int, ip: str, http_port: int) -> None:
"""Add server configuration to persistent storage.
"""Add server configuration to persistent storage with file locking.
Args:
domain: Domain name
@@ -493,29 +517,38 @@ def add_server_to_config(domain: str, slot: int, ip: str, http_port: int) -> Non
ip: Server IP address
http_port: HTTP port
"""
config = load_servers_config()
if domain not in config:
config[domain] = {}
config[domain][str(slot)] = {
"ip": ip,
"http_port": http_port
}
save_servers_config(config)
lock_path = f"{SERVERS_FILE}.lock"
with open(lock_path, 'w') as lock_file:
fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX)
try:
config = load_servers_config()
if domain not in config:
config[domain] = {}
config[domain][str(slot)] = {"ip": ip, "http_port": http_port}
save_servers_config(config)
finally:
fcntl.flock(lock_file.fileno(), fcntl.LOCK_UN)
def remove_server_from_config(domain: str, slot: int) -> None:
"""Remove server configuration from persistent storage.
"""Remove server configuration from persistent storage with file locking.
Args:
domain: Domain name
slot: Server slot to remove
"""
config = load_servers_config()
if domain in config and str(slot) in config[domain]:
del config[domain][str(slot)]
if not config[domain]:
del config[domain]
save_servers_config(config)
lock_path = f"{SERVERS_FILE}.lock"
with open(lock_path, 'w') as lock_file:
fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX)
try:
config = load_servers_config()
if domain in config and str(slot) in config[domain]:
del config[domain][str(slot)]
if not config[domain]:
del config[domain]
save_servers_config(config)
finally:
fcntl.flock(lock_file.fileno(), fcntl.LOCK_UN)
def remove_domain_from_config(domain: str) -> None:
@@ -891,8 +924,8 @@ def haproxy_add_server(domain: str, slot: int, ip: str, http_port: int = 80) ->
results = []
for suffix, port in get_server_suffixes(http_port):
server = f"{server_prefix}{suffix}_{slot}"
haproxy_cmd(f"set server {backend}/{server} addr {ip} port {port}")
haproxy_cmd(f"set server {backend}/{server} state ready")
haproxy_cmd_checked(f"set server {backend}/{server} addr {ip} port {port}")
haproxy_cmd_checked(f"set server {backend}/{server} state ready")
results.append(f"{server} → {ip}:{port}")
# Save to persistent config
@@ -942,6 +975,9 @@ def haproxy_add_servers(domain: str, servers: str) -> str:
if not server_list:
return "Error: servers array is empty"
if len(server_list) > MAX_BULK_SERVERS:
return f"Error: Cannot add more than {MAX_BULK_SERVERS} servers at once"
# Validate all servers first before adding any
validated_servers = []
validation_errors = []
@@ -1014,8 +1050,8 @@ def haproxy_add_servers(domain: str, servers: str) -> str:
try:
for suffix, port in get_server_suffixes(http_port):
server = f"{server_prefix}{suffix}_{slot}"
haproxy_cmd(f"set server {backend}/{server} addr {ip} port {port}")
haproxy_cmd(f"set server {backend}/{server} state ready")
haproxy_cmd_checked(f"set server {backend}/{server} addr {ip} port {port}")
haproxy_cmd_checked(f"set server {backend}/{server} state ready")
# Save to persistent config
add_server_to_config(domain, slot, ip, http_port)
@@ -1063,8 +1099,8 @@ def haproxy_remove_server(domain: str, slot: int) -> str:
# HTTP only - single server per slot
server = f"{server_prefix}_{slot}"
haproxy_cmd(f"set server {backend}/{server} state maint")
haproxy_cmd(f"set server {backend}/{server} addr 0.0.0.0 port 0")
haproxy_cmd_checked(f"set server {backend}/{server} state maint")
haproxy_cmd_checked(f"set server {backend}/{server} addr 0.0.0.0 port 0")
# Remove from persistent config
remove_server_from_config(domain, slot)
@@ -1323,8 +1359,8 @@ def haproxy_set_server_state(backend: str, server: str, state: str) -> str:
if state not in ["ready", "drain", "maint"]:
return "Error: state must be 'ready', 'drain', or 'maint'"
try:
result = haproxy_cmd(f"set server {backend}/{server} state {state}")
return result if result else f"Server {backend}/{server} set to {state}"
haproxy_cmd_checked(f"set server {backend}/{server} state {state}")
return f"Server {backend}/{server} set to {state}"
except HaproxyError as e:
return f"Error: {e}"
@@ -1392,8 +1428,8 @@ def haproxy_set_server_weight(backend: str, server: str, weight: int) -> str:
if not (0 <= weight <= 256):
return "Error: weight must be between 0 and 256"
try:
result = haproxy_cmd(f"set server {backend}/{server} weight {weight}")
return result if result else f"Server {backend}/{server} weight set to {weight}"
haproxy_cmd_checked(f"set server {backend}/{server} weight {weight}")
return f"Server {backend}/{server} weight set to {weight}"
except HaproxyError as e:
return f"Error: {e}"