P0f module

The P0f module performs passive OS fingerprinting by querying a local p0f daemon. This allows Rspamd to identify the operating system of the connecting client based on TCP/IP stack characteristics.

Prerequisites

You need to have p0f v3 installed and running. The p0f daemon should be configured to listen on a Unix socket that Rspamd can connect to.

Example p0f startup:

p0f -i eth0 -s /var/run/p0f.sock

Configuration

To enable the module, create /etc/rspamd/local.d/p0f.conf:

# Enable the module
enabled = true;

# Path to the unix socket that p0f listens on
socket = "/var/run/p0f.sock";

# Connection timeout
timeout = 5s;

# If defined, insert symbol with lookup results
symbol = "P0F";

# Patterns to match against results returned by p0f
# Symbol will be yielded on OS string, link type or distance matches
patterns = {
  WINDOWS = "^Windows.*";
  LINUX = "^Linux.*";
  # DSL = "^link=DSL$";
  # DISTANCE10 = "^distance=10$";
}

# Cache lifetime in seconds (default - 2 hours)
expire = 7200;

# Cache key prefix for Redis
prefix = "p0f";

Configuration options

Option	Default	Description
enabled	false	Enable the p0f module
socket	required	Path to the p0f Unix socket
timeout	5s	Connection timeout
symbol	P0F	Symbol to insert with OS fingerprint results
symbol_fail	P0F_FAIL	Symbol inserted when the p0f scan fails
patterns	{}	Map of symbol names to regex patterns for matching p0f results
message	${SCANNER}: fingerprint matched: "${VIRUS}"	Log/result message template on a match
expire	7200	Cache lifetime in seconds
prefix	p0f	Redis cache key prefix

Pattern matching

The patterns option allows you to define custom symbols that fire when the p0f result matches a specific pattern. Patterns can match against:

• Operating system name (e.g., Windows, Linux)
• Link type, prefixed with link= (e.g., ^link=DSL$, ^link=Ethernet$)
• Network distance, prefixed with distance= (e.g., ^distance=10$)

Symbols

The module registers the following symbols:

• P0F_CHECK - callback symbol (internal)
• P0F - virtual symbol containing OS fingerprint (if symbol is set)
• P0F_FAIL - virtual symbol set when the p0f scan fails (configurable via symbol_fail)
• Custom pattern symbols as defined in patterns configuration

Redis caching

If Redis is configured globally or for this module, p0f results are cached to avoid repeated lookups for the same IP address.