High-performance WAF built on the OpenResty stack
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README.md

Name

lua-resty-waf - High-performance WAF built on the OpenResty stack

Table of Contents

Status

Build Status Codewake CII Best Practices

lua-resty-waf is currently in active development. New bugs and questions opened in the issue tracker will be answered within a day or two, and performance impacting / security related issues will be patched with high priority. Larger feature sets and enhancements will be added when development resources are available (see the Roadmap section for an outline of planned features).

lua-resty-waf is compatible with the master branch of lua-resty-core. The bundled version of lua-resty-core available in recent releases of OpenResty (>= 1.9.7.4) is compatible with lua-resty-waf; versions bundled with older OpenResty bundles are not, so users wanting to leverage resty.core will either need to replace the local version with the one available from the GitHub project, or patch the module based off this commit.

Description

lua-resty-waf is a reverse proxy WAF built using the OpenResty stack. It uses the Nginx Lua API to analyze HTTP request information and process against a flexible rule structure. lua-resty-waf is distributed with a ruleset that mimics the ModSecurity CRS, as well as a few custom rules built during initial development and testing, and a small virtual patchset for emerging threats. Additionally, lua-resty-waf is distributed with tooling to automatically translate existing ModSecurity rules, allowing users to extend lua-resty-waf implementation without the need to learn a new rule syntax.

lua-resty-waf was initially developed by Robert Paprocki for his Master's thesis at Western Governor's University.

Requirements

lua-resty-waf requires several third-party resty lua modules, though these are all packaged with lua-resty-waf, and thus do not need to be installed separately. It is recommended to install lua-resty-waf on a system running the OpenResty software bundle; lua-resty-waf has not been tested on platforms built using separate Nginx source and Nginx Lua module packages.

For optimal regex compilation performance, it is recommended to build Nginx/OpenResty with a version of PCRE that supports JIT compilation. If your OS does not provide this, you can build JIT-capable PCRE directly into your Nginx/OpenResty build. To do this, reference the path to the PCRE source in the --with-pcre configure flag. For example:

# ./configure --with-pcre=/path/to/pcre/source --with-pcre-jit

You can download the PCRE source from the PCRE website. See also this blog post for a step-by-step walkthrough on building OpenResty with a JIT-enabled PCRE library.

Performance

lua-resty-waf was designed with efficiency and scalability in mind. It leverages Nginx's asynchronous processing model and an efficient design to process each transaction as quickly as possible. Load testing has show that deployments implementing all provided rulesets, which are designed to mimic the logic behind the ModSecurity CRS, process transactions in roughly 300-500 microseconds per request; this equals the performance advertised by Cloudflare's WAF. Tests were run on a reasonable hardware stack (E3-1230 CPU, 32 GB RAM, 2 x 840 EVO in RAID 0), maxing at roughly 15,000 requests per second. See this blog post for more information.

lua-resty-waf workload is almost exclusively CPU bound. Memory footprint in the Lua VM (excluding persistent storage backed by lua-shared-dict) is roughly 2MB.

Installation

A simple Makefile is provided:

# make && sudo make install

Alternatively, install via Luarocks:

# luarocks install lua-resty-waf

lua-resty-waf makes use of the OPM package manager, available in modern OpenResty distributions. The client OPM tools requires that the resty command line tool is available in your system's PATH environmental variable.

Note that by default lua-resty-waf runs in SIMULATE mode, to prevent immediately affecting an application; users who wish to enable rule actions must explicitly set the operational mode to ACTIVE.

Synopsis

http {
    init_by_lua_block {
        -- use resty.core for performance improvement, see the status note above
        require "resty.core"

        -- require the base module
        local lua_resty_waf = require "resty.waf"

        -- perform some preloading and optimization
        lua_resty_waf.init()
    }

    server {
        location / {
            access_by_lua_block {
                local lua_resty_waf = require "resty.waf"

                local waf = lua_resty_waf:new()

                -- define options that will be inherited across all scopes
                waf:set_option("debug", true)
                waf:set_option("mode", "ACTIVE")

                -- this may be desirable for low-traffic or testing sites
                -- by default, event logs are not written until the buffer is full
                -- for testing, flush the log buffer every 5 seconds
                --
                -- this is only necessary when configuring a remote TCP/UDP
                -- socket server for event logs. otherwise, this is ignored
                waf:set_option("event_log_periodic_flush", 5)

                -- run the firewall
                waf:exec()
            }

            header_filter_by_lua_block {
                local lua_resty_waf = require "resty.waf"

                -- note that options set in previous handlers (in the same scope)
                -- do not need to be set again
                local waf = lua_resty_waf:new()

                waf:exec()
            }

            body_filter_by_lua_block {
                local lua_resty_waf = require "resty.waf"

                local waf = lua_resty_waf:new()

                waf:exec()
            }

            log_by_lua_block {
                local lua_resty_waf = require "resty.waf"

                local waf = lua_resty_waf:new()

                waf:exec()
            }
        }
    }
}

Public Functions

lua-resty-waf.load_secrules()

Translate and initialize a ModSecurity SecRules file from disk. Note that this still requires the ruleset to be added via add_ruleset (the basename of the file must be given as the key).

Example:

http {
    init_by_lua_block {
        local lua_resty_waf = require "resty.waf"

        -- this translates and calculates a ruleset called 'ruleset_name'
        local ok, errs = pcall(function()
            lua_resty_waf.load_secrules("/path/to/secrules/ruleset_name")
        end)

        -- errs is an array-like table
        if errs then
            for i = 1, #errs do
                ngx.log(ngx.ERR, errs[i])
            end
        end
    }

    server {
        location / {
            access_by_lua_block {
                local lua_resty_waf = require "resty.waf"

                local waf = lua_resty_waf:new()

                -- in order to use the loaded ruleset, it must be added via
                -- the 'add_ruleset' option
                waf:set_option("add_ruleset", "ruleset_name")
            }
        }
    }
}

Additionally, load_secrules can take an optional second argument as a table of options to pass to various translation functions. The following options are recognized:

  • path: Define a filesystem path to search for data files for operators such as @pmFromFile. If no such key is defined, the current working directory (.) is used
  • force: Do not error and abort when failing to translate a rule variable
  • loose: Do not error and abort when failing to translate a rule action
  • quiet: Do not error or warn when failing to translate a rule action

This function can also take a third option as a table to catch translation errors, for later processing. If this option is not present or a not a table, translation errors will instead be logged to the error log.

lua-resty-waf.init()

Perform some pre-computation of rules and rulesets, based on what's been made available via the default distributed rulesets. It's recommended, but not required, to call this function (not doing so will result in a small performance penalty). This function should never be called outside this scope.

Example:

http {
    init_by_lua_block {
        local lua_resty_waf = require "resty.waf"

        lua_resty_waf.init()
    }
}

Public Methods

lua-resty-waf:new()

Instantiate a new instance of lua-resty-waf. You must call this in every request handler phase you wish to run lua-resty-waf, and use the return result to call further object methods.

Example:

location / {
    access_by_lua_block {
        local lua_resty_waf = require "resty.waf"

        local waf = lua_resty_waf:new()
    }
}

lua-resty-waf:set_option()

Configure an option on a per-scope basis.

Example:

location / {
    access_by_lua_block {
        local lua_resty_waf = require "resty.waf"

        local waf = lua_resty_waf:new()

        -- enable debug logging only for this scope
        waf:set_option("debug", true)
    }
}

lua-resty-waf:set_var()

Define a transaction variable (stored in the TX variable collection) before executing the WAF. This can be used to define variables used by complex rulesets such as the OWASP CRS.

Example:

location / {
    access_by_lua_block {
        local lua_resty_waf = require "resty.waf"

        local waf = lua_resty_waf:new()

        waf:set_var("FOO", "bar")
    }
}

Note that as with any other ModSecurity rule, the existence of a variable bears no functional change to WAF processing; it is the responsibility of the rule author to understand and use TX variables.

lua-resty-waf:sieve_rule()

Define a collection exclusion for a given rule.

Example:

location / {
    access_by_lua_block {
        local lua_resty_waf = require "resty.waf"

        local waf = lua_resty_waf:new()

        local sieves = {
            {
                type   = "ARGS",
                elts   = "foo",
                action = "ignore",
            }
        }

        waf:sieve_rule("12345", sieves)
    }
}

See the rule sieves wiki page for details and advanced usage examples.

lua-resty-waf:exec()

Run the rule engine. By default, the engine is executed according to the currently running phase. An optional table may be passed, allowing users to "mock" execution of a different phase.

Example:

location / {
    access_by_lua_block {
        local lua_resty_waf = require "resty.waf"

        local waf = lua_resty_waf:new()

        -- execute according to access phase collections and rules
        waf:exec()
    }

    content_by_lua_block {
        local lua_resty_waf = require "waf"

        local waf = lua_resty_waf:new()

        -- execute header_filter rules, passing in a table of additional collections
        -- this assumes the 'request_headers' and 'status' Lua variables were
        -- declared and initialized elsewhere
        local opts = {
            phase = 'header_filter',
            collections = {
                REQUEST_HEADERS = request_headers,
                STATUS = status,
            }
        }

        waf:exec(opts)
    }
}

lua-resty-waf:write_log_events()

Write any audit log entries that were generated from the transaction. This is only optional when exec is called in a log_by_lua handler.

Example:

location / {
    log_by_lua_block {
        local lua_resty_waf = require "resty.waf"

        local waf = lua_resty_waf:new()

        -- write out any event log entries to the
        -- configured target, if applicable
        waf:write_log_events()
    }
}

Options

add_ruleset

Default: none

Adds an additional ruleset to be used during processing. This allows users to implement custom rulesets without stomping over the included rules directory. Additional rulesets must reside within a folder called "rules" that lives within the lua_package_path.

Example:

http {
    -- the rule file 50000.json must live at
    -- /path/to/extra/rulesets/rules/50000.json
    lua_package_path '/path/to/extra/rulesets/?.lua;;';

    server {
        location / {
            access_by_lua_block {
                waf:set_option("add_ruleset", "50000_extra_rules")
            }
        }
    }
}

Multiple rulesets may be added by passing a table of values to set_option. Note that ruleset names are sorted before processing. Rulesets are processed in a low-to-high sorted order.

add_ruleset_string

Default: none

Adds an additional ruleset to be used during processing. This allows users to implement custom rulesets without stomping over the included rules directory. Rulesets are defined inline as a Lua string, in the form of a translated ruleset JSON structure.

Example:

location / {
    access_by_lua_block {
        waf:set_option("add_ruleset_string", "70000_extra_rules", [=[{"access":[{"action":"DENY","id":73,"operator":"REGEX","opts":{},"pattern":"foo","vars":[{"parse":{"values":1},"type":"REQUEST_ARGS"}]}],"body_filter":[],"header_filter":[]}]=])
    }
}

Note that ruleset names are sorted before processing, and must be given as strings. Rulesets are processed in a low-to-high sorted order.

allow_unknown_content_types

Default: false

Instructs lua-resty-waf to continue processing the request when a Content-Type header has been sent that is not in the allowed_content_types table. Such requests will not have their request body processed by lua-resty-waf (the REQUEST_BODY collection will be nil). In this manner, users do not need to explicitly whitelist all possible Content-Type headers they may encounter.

Example:

location / {
    access_by_lua_block {
        waf:set_option("allow_unknown_content_types", true)
    }
}

allowed_content_types

Default: none

Defines one or more Content-Type headers that will be allowed, in addition to the default Content-Types application/x-www-form-urlencoded and multipart/form-data. A request whose content type matches one of allowed_content_types will set the REQUEST_BODY collection to a single string containing (rather than a table); a request whose content type does not match one of these values, or application/x-www-form-urlencoded or multipart/form-data, will be rejected.

Example:

location / {
    access_by_lua_block {
        -- define a single allowed Content-Type value
        waf:set_option("allowed_content_types", "text/xml")

        -- defines multiple allowed Content-Type values
        waf:set_option("allowed_content_types", { "text/html", "text/json", "application/json" })
    }
}

Note that mutiple set_option calls with a parameter of allowed_content_types will simply override the existing options table, so if you want to define multiple allowed content types, you must define them as a Lua table as shown above.

debug

Default: false

Disables/enables debug logging. Debug log statements are printed to the error_log. Note that debug logging is very expensive and should not be used in production environments.

Example:

location / {
    access_by_lua_block {
        waf:set_option("debug", true)
    }
}

debug_log_level

Default: ngx.INFO

Sets the nginx log level constant used for debug logging.

Example:

location / {
    access_by_lua_block {
        waf:set_option("debug_log_level", ngx.DEBUG)
    }
}

deny_status

Default: ngx.HTTP_FORBIDDEN

Sets the status to use when denying requests.

Example:

location / {
    access_by_lua_block {
        waf:set_option("deny_status", ngx.HTTP_NOT_FOUND)
    }
}

disable_pcre_optimization

Default: false

Removes the oj flags from all ngx.re.match, ngx.re.find, and ngx.re.sub calls. This may be useful in some cases where older PCRE libraries are used, but will cause severe performance degradation, so its use is strongly discouraged; users are instead encouraged to build OpenResty with a modern, JIT-capable PCRE library.

Example:

location / {
    access_by_lua_block {
        waf:set_option("disable_pcre_optimization", true)
    }
}

Note: This behavior is deprecated and will be removed in future versions.

event_log_altered_only

Default: true

Determines whether to write log entries for rule matches in a transaction that was not altered by lua-resty-waf. "Altered" is defined as lua-resty-waf acting on a rule whose action is ACCEPT or DENY. When this option is unset, lua-resty-waf will log rule matches even if the transaction was not altered. By default, lua-resty-waf will only write log entries for matches if the transaction was altered.

Example:

location / {
    access_by_lua_block {
        waf:set_option("event_log_altered_only", false)
    }
}

Note that mode will not have an effect on determing whether a transaction is considered altered. That is, if a rule with a DENY action is matched, but lua-resty-waf is running in SIMULATE mode, the transaction will still be considered altered, and rule matches will be logged.

event_log_buffer_size

Default: 4096

Defines the threshold size, in bytes, of the buffer to be used to hold event logs. The buffer will be flushed when this threshold is met.

Example:

location / {
    access_by_lua_block {
        -- 8 KB event log message buffer
        waf:set_option("event_log_buffer_size", 8192)
    }
}

event_log_level

Default: ngx.INFO

Sets the nginx log level constant used for event logging.

Example:

location / {
    access_by_lua_block {
        waf:set_option("event_log_level", ngx.WARN)
    }
}

event_log_ngx_vars

Default: empty

Defines what extra variables from ngx.var are put to the log event. This is a generic way to extend the alert with extra context. The variable name will be the key of the entry under an ngx key in the log entry. If the variable is not present as an nginx variable, no item is added to the event.

Example:

location / {
    access_by_lua_block {
        waf:set_option("event_log_ngx_vars", "host")
        waf:set_option("event_log_ngx_vars", "request_id")
    }
}

The resulting event has these extra items:

{
"ngx": {
    "host": "example.com",
    "request_id": "373bcce584e3c18a"
}
}

event_log_periodic_flush

Default: none

Defines an interval, in seconds, at which the event log buffer will periodically flush. If no value is configured, the buffer will not flush periodically, and will only flush when the event_log_buffer_size threshold is reached. Configure this option for very low traffic sites that may not receive any event log data in a long period of time, to prevent stale data from sitting in the buffer.

Example:

location / {
    access_by_lua_block {
        -- flush the event log buffer every 30 seconds
        waf:set_option("event_log_periodic_flush", 30)
    }
}

event_log_request_arguments

Default: false

When set to true, the log entries contain the request arguments under the uri_args key.

Example:

location / {
    access_by_lua_block {
        waf:set_option("event_log_request_arguments", true)
    }
}

event_log_request_body

Default: false

When set to true, the log entries contain the request body under the request_body key.

Example:

location / {
    access_by_lua_block {
        waf:set_option("event_log_request_body", true)
    }
}

event_log_request_headers

Default: false

The headers of the HTTP request is copied to the log event, under the request_headers key.

Example:

location / {
    access_by_lua_block {
        waf:set_option("event_log_request_headers", true)
    }
}

The resulting event has these extra items:

{
"request_headers": {
    "accept": "*/*",
    "user-agent": "curl/7.22.0 (x86_64-pc-linux-gnu) libcurl/7.22.0 OpenSSL/1.0.1 zlib/1.2.3.4 libidn/1.23 librtmp/2.3"
}
}

event_log_ssl

Default: false

Enable SSL connections when logging via TCP/UDP.

Example:

location / {
    access_by_lua_block {
        waf:set_option("event_log_ssl", true)
    }
}

event_log_ssl_sni_host

Default: none

Set the SNI host for lua-resty-logger-socket connections.

Example:

location / {
    access_by_lua_block {
        waf:set_option("event_log_ssl_sni_host", "loghost.example.com")
    }
}

event_log_ssl_verify

Default: false

Enable certification verification for SSL connections when logging via TCP/UDP.

Example:

location / {
    access_by_lua_block {
        waf:set_option("event_log_ssl_verify", true)
    }
}

event_log_socket_proto

Default: udp

Defines which IP protocol to use (TCP or UDP) when shipping event logs via a remote socket. The same buffering and recurring flush logic will be used regardless of protocol.

Example:

location / {
    access_by_lua_block {
        -- send logs via TCP
        waf:set_option("event_log_socket_proto", "tcp")
    }
}

event_log_target

Default: error

Defines the destination for event logs. lua-resty-waf currently supports logging to the error log, a separate file on the local file system, or a remote TCP or UDP server. In the latter two cases, event logs are buffered and flushed when a defined threshold is reached (see below for further options regarding event logging options).

Example:

location / {
    access_by_lua_block {
        -- send event logs to the server's error_log location (default)
        waf:set_option("event_log_target", "error")

        -- send event logs to a local file on disk
        waf:set_option("event_log_target", "file")

        -- send event logs to a remote server
        waf:set_option("event_log_target", "socket")
    }
}

Note that, due to a limition in the logging library used, only a single target socket can be defined. This is to say, you may only configure one socket target with a specific host/port combination; if you configure a second host/port combination, data will not be properly logged.

event_log_target_host

Default: none

Defines the target server for event logs that target a remote server.

Example:

location / {
    access_by_lua_block {
        waf:set_option("event_log_target_host", "10.10.10.10")
    }
}

event_log_target_path

Default: none

Defines the target path for event logs that target a local file system location.

Example:

location / {
    access_by_lua_block {
        waf:set_option("event_log_target_path", "/var/log/lua-resty-waf/event.log")
    }
}

This path must be in a location writeable by the nginx user. Note that, by nature, on-disk logging can cause significant performance degredation in high-concurrency environments.

event_log_target_port

Default: none

Defines the target port for event logs that target a remote server.

Example:

location / {
    access_by_lua_block {
        waf:set_option("event_log_target_port", 9001)
    }
}

hook_action

Default: none

Override the functionality of actions taken when a rule is matched. See the example for more details

Example:

    location / {
        access_by_lua_block {
            local deny_override = function(waf, ctx)
                ngx.log(ngx.INFO, "Overriding DENY action")
                ngx.status = 404
            end

            -- override the DENY action with the function defined above
            waf:set_option("hook_action", "DENY", deny_override)
        }
    }

ignore_rule

Default: none

Instructs the module to ignore a specified rule ID. Note that ignoring a rule in a chain will result in the entire chain being ignored, and processing will continue to the next rule following the chain.

Example:

location / {
    access_by_lua_block {
        waf:set_option("ignore_rule", 40294)
        waf:set_option("ignore_rule", {40002, 41036})
    }
}

Multiple rules can be ignored by passing a table of rule IDs to set_option.

ignore_ruleset

Default: none

Instructs the module to ignore an entire ruleset. This can be useful when some rulesets (such as the SQLi or XSS CRS rulesets) are too prone to false positives, or aren't applicable to your application.

Example:

location / {
    access_by_lua_block {
        waf:set_option("ignore_ruleset", "41000_sqli")
    }
}

mode

Default: SIMULATE

Sets the operational mode of the module. Options are ACTIVE, INACTIVE, and SIMULATE. In ACTIVE mode, rule matches are logged and actions are run. In SIMULATE mode, lua-resty-waf loops through each enabled rule and logs rule matches, but does not complete the action specified in a given run. INACTIVE mode prevents the module from running.

By default, SIMULATE is selected if a mode is not explicitly set; this requires new users to actively implement blocking by setting the mode to ACTIVE.

Example:

location / {
    access_by_lua_block {
        waf:set_option("mode", "ACTIVE")
    }
}

nameservers

Default: none

Sets the DNS resolver(s) to be used for RBL lookups. Currently only UDP/53 traffic is supported. This option must be defined as a numeric address, not a hostname. If this option is not defined, all RBL lookup rules will return false.

Example:

location / {
    access_by_lua_block {
        waf:set_option("nameservers", "10.10.10.10")
    }
}

process_multipart_body

Default true

Enable processing of multipart/form-data request bodies (when present), using the lua-resty-upload module. In the future, lua-resty-waf may use this processing to perform stricter checking of upload bodies; for now this module performs only minimal sanity checks on the request body, and will not log an event if the request body is invalid. Disable this option if you do not need this checking, or if bugs in the upstream module are causing problems with HTTP uploads.

Example:

location / {
    access_by_lua_block {
        -- disable processing of multipart/form-data requests
        -- note that the request body will still be sent to the upstream
        waf:set_option("process_multipart_body", false)
    }
}

req_tid_header

Default: false

Set an HTTP header X-Lua-Resty-WAF-ID in the upstream request, with the value as the transaction ID. This ID will correlate with the transaction ID present in the debug logs (if set). This can be useful for request tracking or debug purposes.

Example:

location / {
    access_by_lua_block {
        waf:set_option("req_tid_header", true)
    }
}

res_body_max_size

Default: 1048576 (1 MB)

Defines the content length threshold beyond which response bodies will not be processed. This size of the response body is determined by the Content-Length response header. If this header does not exist in the response, the response body will never be processed.

Example:

location / {
    access_by_lua_block {
        -- increase the max response size to 2 MB
        waf:set_option("res_body_max_size", 1024 * 1024 * 2)
    }
}

Note that by nature, it is required to buffer the entire response body in order to properly use the response as a collection, so increasing this number significantly is not recommended without justification (and ample server resources).

res_body_mime_types

Default: "text/plain", "text/html"

Defines the MIME types with which lua-resty-waf will process the response body. This value is determined by the Content-Type header. If this header does not exist, or the response type is not in this list, the response body will not be processed. Setting this option will add the given MIME type to the existing defaults of text/plain and text/html.

Example:

location / {
    access_by_lua_block {
        -- mime types that will be processed are now text/plain, text/html, and text/json
        waf:set_option("res_body_mime_types", "text/json")
    }
}

Multiple MIME types can be added by passing a table of types to set_option.

res_tid_header

Default: false

Set an HTTP header X-Lua-Resty-WAF-ID in the downstream response, with the value as the transaction ID. This ID will correlate with the transaction ID present in the debug logs (if set). This can be useful for request tracking or debug purposes.

Example:

location / {
    access_by_lua_block {
        waf:set_option("res_tid_header", true)
    }
}

score_threshold

Default: 5

Sets the threshold for anomaly scoring. When the threshold is reached, lua-resty-waf will deny the request.

Example:

location / {
    access_by_lua_block {
        waf:set_option("score_threshold", 10)
    }
}

storage_backend

Default: dict

Define an engine to use for persistent variable storage. Current available options are dict (ngx_lua shared memory zone), memcached, amd redis.

Example:

location / {
    acccess_by_lua_block {
        waf:set_option("storage_backend", "memcached")
    }
}

storage_keepalive

Default: true

Enable or disable TCP keepalive for connections to remote persistent storage hosts.

Example:

location / {
    acccess_by_lua_block {
        waf:set_option("storage_keepalive", false)
    }
}

storage_keepalive_timeout

Default: 10000

Configure (in milliseconds) the timeout for the cosocket keepalive pool for remote persistent storage hosts.

Example:

location / {
    acccess_by_lua_block {
        waf:set_option("storage_keepalive_timeout", 30000)
    }
}

storage_keepalive_pool_size

Default: 100

Configure the pool size for the cosocket keepalive pool for remote persistent storage hosts.

Example:

location / {
    acccess_by_lua_block {
        waf:set_option("storage_keepalive_pool_size", 50)
    }
}

storage_memcached_host

Default: 127.0.0.1

Define a host to use when using memcached as a persistent variable storage engine.

Example:

location / {
    acccess_by_lua_block {
        waf:set_option("storage_memcached_host", "10.10.10.10")
    }
}

storage_memcached_port

Default: 11211

Define a port to use when using memcached as a persistent variable storage engine.

Example:

location / {
    acccess_by_lua_block {
        waf:set_option("storage_memcached_port", 11221)
    }
}

storage_redis_host

Default: 127.0.0.1

Define a host to use when using redis as a persistent variable storage engine.

Example:

location / {
    acccess_by_lua_block {
        waf:set_option("storage_redis_host", "10.10.10.10")
    }
}

storage_redis_port

Default: 6379

Define a port to use when using redis as a persistent variable storage engine.

Example:

location / {
    acccess_by_lua_block {
        waf:set_option("storage_redis_port", 6397)
    }
}

storage_zone

Default: none

Defines the lua_shared_dict that will be used to hold persistent storage data. This zone must be defined in the http{} block of the configuration.

Example:_

http {
    -- define a 64M shared memory zone to hold persistent storage data
    lua_shared_dict persistent_storage 64m;
}

location / {
    access_by_lua_block {
        waf:set_option("storage_zone", "persistent_storage")
    }
}

Multiple shared zones can be defined and used, though only one zone can be defined per configuration location. If a zone becomes full and the shared dictionary interface cannot add additional keys, the following will be entered into the error log:

Error adding key to persistent storage, increase the size of the lua_shared_dict

Phase Handling

lua-resty-waf is designed to run in multiple phases of the request lifecycle. Rules can be processed in the following phases:

  • access: Request information, such as URI, request headers, URI args, and request body are available in this phase.
  • header_filter: Response headers and HTTP status are available in this phase.
  • body_filter: Response body is available in this phase.
  • log: Event logs are automatically written at the completion of this phase.

These phases correspond to their appropriate Nginx lua handlers (access_by_lua, header_filter_by_lua, body_filter_by_lua, and log_by_lua, respectively). Note that running lua-resty-waf in a lua phase handler not in this list will lead to broken behavior. All data available in an earlier phase is available in a later phase. That is, data available in the access phase is also available in the header_filter and body_filter phases, but not vice versa.

Included Rulesets

lua-resty-waf is distributed with a number of rulesets that are designed to mimic the functionality of the ModSecurity CRS. For reference, these rulesets are listed here:

  • 11000_whitelist: Local policy whitelisting
  • 20000_http_violation: HTTP protocol violation
  • 21000_http_anomaly: HTTP protocol anomalies
  • 35000_user_agent: Malicious/suspect user agents
  • 40000_generic_attack: Generic attacks
  • 41000_sqli: SQLi
  • 42000_xss: XSS
  • 90000_custom: Custom rules/virtual patching
  • 99000_scoring: Anomaly score handling

Rule Definitions

lua-resty-waf parses rules definitions from JSON blobs stored on-disk. Rules are grouped based on purpose and severity, defined as a ruleset. The included rulesets were created to mimic some functionality of the ModSecurity CRS, particularly the base_rules definitions. Additionally, the included modsec2lua-resty-waf.pl script can be used to translate additional or custom rulesets to a lua-resty-waf-compatible JSON blob.

Note that there are several limitations in the translation script, with respect to unsupported actions, collections, and operators. Please see this wiki page for an up-to-date list of known incompatibilities.

Notes

Community

There is a Freenode IRC channel #lua-resty-waf. Travis CI sends notifications here; feel free to ask questions/leave comments in this channel as well.

Additionally, Q/A is available on CodeWake:

Codewake

Pull Requests

Please target all pull requests towards the development branch, or a feature branch if the PR is a significant change. Commits to master should only come in the form of documentation updates or other changes that have no impact of the module itself (and can be cleanly merged into development).

Roadmap

  • Expanded virtual patch ruleset: Increase coverage of emerging threats.
  • Expanded integration/acceptance testing: Increase coverage of common threats and usage scenarios.
  • Expanded ModSecurity syntax translations: Support more operators, variables, and actions.
  • Common application profiles: Tuned rulesets for common CMS/applications.
  • Support multiple socket/file logger targets: Likely requires forking the lua-resty-logger-socket project.

Limitations

lua-resty-waf is undergoing continual development and improvement, and as such, may be limited in its functionality and performance. Currently known limitations can be found within the GitHub issue tracker for this repo.

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/

Bugs

Please report bugs by creating a ticket with the GitHub issue tracker.

See Also