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Rename the program to sww and its deciding daemon to discriminator (closes #218) 
The program is now sww, built from cmd/sww, with two modes: sww rproxy and
sww discriminator. servewaf becomes discriminator everywhere it names that
daemon: the package (internal/discriminator), its types, functions, files, the
discriminator_line log field, and its docs and tests.

smallwebwaf is left only where sneak's directive allows it: the documents'
product name, the git.eeqj.de/sneak/smallwebwaf URLs, and the Go module path
sneak.berlin/go/smallwebwaf. Everywhere else a name containing it takes the sww
form: the package (internal/sww), metric names (sww_*), the X-Sww-* headers,
the /_sww/ admin endpoints, the OS user, and the state and rules directories.
The SWWAF_ environment variables take the SWW_ form.

No logic changes. make check passes.

Model: deepseek-v4-pro
2026-11-07 05:27:58 +00:00

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# smallwebwaf
`smallwebwaf` is an MIT-licensed web application firewall, written in Go by
[@sneak](https://sneak.berlin), for self-hosted web apps. It refuses the
requests of scrapers, scanners and other abusers before they reach an app.
## What it does
A web application firewall reads each request on its way to a web app and
refuses the ones that look like abuse. `smallwebwaf` is one program, `sww`,
shipped in one image, with two commands that do this together:
- `sww rproxy` is a small reverse proxy in front of one app. traefik routes to
it. It asks `discriminator` about each request, passes the allowed ones to the
app, and passes the app's answers back. It keeps nothing and never touches
disk.
- `sww discriminator` decides. It runs the checks and keeps the bans, the
counters and each client's history. One `discriminator` serves many sites: a
client banned through one site is refused on all of them, and its requests on
all of them count toward one set of limits.
The site keeps answering while `discriminator` is down, slow or restarting:
without an answer in time, `rproxy` passes the request to the app.
It protects against:
- Scrapers that fetch every page of a site, all day. Each client gets a limit on
requests and on bytes per minute, per hour and per day. The defaults leave
room for a person reading a site for hours. They catch a scraper that keeps up
one request every 2 seconds. A client over a limit is refused and banned: for
a while at first, for three times as long at each repeat, and permanently when
it keeps at it.
- Scanners that probe for secrets, such as `/.env` or `/.git/config`. The
default rule file bans such a client at its first probe, and its next request
during the ban makes the ban permanent. Your own rules, or a list of trap
paths, ban probes for other apps, such as a WordPress login, the same way.
- Attacks carried in a request's URL or headers, such as SQL injection and path
traversal. The OWASP Core Rule Set, a published set of rules that recognise
common web attacks, runs on every request through Coraza, a Go engine. A
request the rules take for an attack is refused.
- Abuse from networks and countries you do not want. You can:
- refuse whole netblocks and countries;
- give the clients of chosen networks and countries a fraction of every
limit, so that they are banned sooner;
- refuse or limit clients on a blocklist, a DNS blocklist, or with a high
AbuseIPDB score;
- ban clients named by your own CrowdSec engine.
- Slow and oversized requests. Every request and every answer has a time limit
and a size limit.
For the operator, it:
- logs each request as JSON lines, saying what it did and why;
- sends alerts to a webhook, Slack or ntfy;
- serves Prometheus metrics;
- keeps its bans, counters and history in JSON files you can read and edit, so
that a restart loses nothing and a ban can be lifted with an editor.
Not built, and not planned:
- TLS and routing by host name. Both stay with traefik, the reverse proxy in
front of `rproxy`.
- Browser challenges such as captchas.
- A web console, or a configuration file.
- Defence against floods large enough to fill the host's network link.
## Getting started
### The image
No image is published. Build it from a clone. `make docker` runs the tests and
the linter, then builds the image, tagged `smallwebwaf`.
```sh
git clone https://git.eeqj.de/sneak/smallwebwaf.git
cd smallwebwaf
make docker
```
Push the image to a registry your hosts pull from, and name it there by digest.
The image runs `rproxy` by default. To run `discriminator` from the same image,
set the container's `SWW_COMMAND` to `discriminator`. The image's health check
follows the command: in `rproxy`'s container it passes once `rproxy` answers and
the app accepts connections, whether or not `discriminator` answers; in
`discriminator`'s container, once `discriminator` answers.
### The usual setup: three containers
The usual setup is three containers on one private network:
- the app;
- `rproxy`, in front of the app, which traefik routes to: `SWRP_WAF_BACKEND`
names `discriminator` and `SWRP_UPSTREAM_URL` names the app;
- `discriminator`, with `SWW_COMMAND=discriminator` and a volume at
`/var/lib/sww` for its state files.
Point traefik's labels at port 8080 of `rproxy`
(`traefik.http.services.<name>.loadbalancer.server.port=8080`). Publish no port
of the app or of `discriminator`. Anything on that network can reach the app
around `rproxy`, and can ask `discriminator` questions, so the network holds
only what you trust. Each further app adds its own container and its own
`rproxy`, whose `SWRP_WAF_BACKEND` names the same `discriminator`. The "Smallest
setup" example below shows this shape.
### `rproxy` in the app's container
An app's image can instead be built on the `smallwebwaf` image, so that `rproxy`
runs beside the app in one container. `discriminator` still runs in a container
of its own. The app's `Dockerfile` starts `FROM` the `smallwebwaf` image, named
by digest, and adds:
- the app's binary;
- the packages the app needs, from the nixpkgs in the image;
- a user for the app;
- a `run` script that starts the app listening on `127.0.0.1:8081`, the default
of `SWRP_UPSTREAM_URL`.
```dockerfile
# The smallwebwaf image, pinned by digest.
FROM <registry>/smallwebwaf@sha256:<digest>
# Packages the app needs, if any, from the nixpkgs in the image.
RUN nix-env -iA nixpkgs.git
# The app's binary, and a user of its own to run it.
COPY app /usr/local/bin/app
RUN useradd --system --no-create-home --shell /usr/sbin/nologin app
# The app's runit service.
COPY --chmod=755 app.run /etc/service/app/run
```
`app.run` sits beside the `Dockerfile`. `--listen` and `--trusted-proxies` stand
for the app's own options:
```bash
#!/usr/bin/env bash
set -euo pipefail
main() {
sleep 1
exec chpst -u app:app /usr/local/bin/app \
--listen 127.0.0.1:8081 \
--trusted-proxies 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16,127.0.0.1/32,::1/128
}
main "$@"
```
Leave `ENTRYPOINT` and `USER` out of the app's `Dockerfile`. The image's own
entrypoint starts `rproxy` and the app side by side, each as its own user. Run
the app's image with `SWRP_WAF_BACKEND` set. `deploy/example-app` is such an
app, and the "`rproxy` beside the app" example below runs one.
The app sees the headers traefik sent, with traefik's address added to
`X-Forwarded-For`, from a TCP peer that is `rproxy`. So the app must trust
`rproxy`'s address for forwarded headers. In a container of its own, `rproxy` is
on the private network, which the usual default of a trusted-proxy setting
covers. Beside the app, its address is `127.0.0.1` or `::1`, which the private
ranges leave out, so the app's own setting must name them too, as `app.run`
does.
### Checking that it works
- `docker inspect --format '{{.State.Health.Status}}' <container>` says
`healthy` for each container of `smallwebwaf`.
- A log line with `"msg":"starting"` gives the version, the address and every
setting in effect, with secrets masked.
- A request to the site through traefik gets the app's answer.
`https://<site>/_sww/healthz` answers `ok`. `discriminator`'s log lines about
the request have `"action":"forward"`.
- To see a refusal without banning yourself, run `discriminator` with
`SWW_MODE=observe` and ask for `/.env`. The request reaches the app.
`discriminator`'s log lines have `"would_action":"banned"` and
`"rule_ids":["env-file"]`. A ban you get in `enforce` mode is lifted as
"Clients and bans" below describes.
- With `SWW_METRICS_TOKEN` set, this answers with the metrics, from a host on
`discriminator`'s network:
`curl -H "Authorization: Bearer $TOKEN" http://discriminator:8080/_sww/metrics`.
- `make example-app` builds the image and an app on it, runs them, and checks
the whole exchange (see "Entrypoints").
## Configuration
Every setting is an environment variable, read once at start; changing one means
restarting the container. `rproxy` reads only the `SWRP_` settings, and
`discriminator` only the `SWW_` ones. Every setting but `SWRP_WAF_BACKEND` has a
default, chosen for a service on the open internet. A setting that needs an
account, a key, a token or an alert destination stays off until you give one.
- Any `SWW_` setting can be given as a file instead, for secrets and long lists:
`SWW_ADMIN_TOKEN_FILE` names the file that holds `SWW_ADMIN_TOKEN`. The file's
contents are the value, less one newline at the end. Setting both forms stops
the start. `SWW_LOG_REMOTE_TLS_CA_FILE` and
`SWW_CORE_RULE_SET_EXCLUSIONS_FILE` already name a file, so they have no
`_FILE` form. `SWW_COMMAND` cannot be given as a file. No `SWRP_` setting has
one, since `rproxy` never touches disk.
- A duration is Go's syntax, with `d` for days: `90s`, `15m`, `24h`, `7d`.
- A size is a number of bytes with an optional `K`, `M` or `G`, in powers of
1024: `512K`, `100M`, `5G`.
- A count is a whole number of requests, such as `1000`.
- A time in milliseconds is a whole number above zero, such as `2000`.
- A list is comma separated. A list set to an empty value is an empty list, and
replaces the default.
- A netblock is an address and a prefix length, such as `10.0.0.0/8`; a bare
address stands for itself alone. A country is a two-letter code in either
case, such as `de`. An AS number is `AS` and the number, such as `AS64496`. A
percentage is a whole number from 0 to 100. A path prefix starts with `/`.
- `off` switches a limit, a threshold or a timeout off where the table says a
setting takes it.
- An invalid setting stops the process at start with one log line naming the
variable and what is wrong with the value. The settings in effect are logged
on one line at start, with tokens, keys and webhook paths shown as `********`.
Every setting the code reads, with its default:
| Variable | Default | What it does |
| ---------------------------------------- | ------------------------------------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `SWW_COMMAND` | `rproxy` | Which command the image runs, and its health check checks: `rproxy` or `discriminator`. |
| `SWRP_WAF_BACKEND` | required | `discriminator`'s URL, such as `http://discriminator:8080`. |
| `SWRP_UPSTREAM_URL` | `http://127.0.0.1:8081` | The app's URL: a scheme, a host and an optional port, nothing more. |
| `SWRP_LISTEN_ADDR` | `:8080` | Where `rproxy` listens; leave the host part empty. |
| `SWRP_TRUSTED_PROXIES` | `10.0.0.0/8,172.16.0.0/12,192.168.0.0/16` | The netblocks whose `X-Forwarded-For` `rproxy` believes; set but empty, it believes none. |
| `SWRP_TIMEOUT_MS` | `2000` | How long `rproxy` waits for `discriminator`'s answer to a question and to a report, in milliseconds. |
| `SWRP_DEFAULT_DISPOSITION` | `allow` | What `rproxy` does with a request when `discriminator` cannot be reached or does not answer in time: `allow` passes it to the app, `deny` answers `503`. |
| `SWRP_MAX_REQUEST_SIZE` | `100M` | The largest request body, a size or `off`; a larger one is answered `413`. |
| `SWRP_MAX_RESPONSE_SIZE` | `1G` | The largest response body, a size or `off`; a larger one is answered `502`, or cut off once it has started. |
| `SWRP_MAX_REQUEST_TIME_MS` | `60000` | How long the visitor may take to send its request line and headers, and then the whole request to reach the app, in milliseconds or `off`. |
| `SWRP_MAX_RESPONSE_TIME_MS` | `1800000` | How long the answer may take, from the end of the request to its last byte reaching the visitor, in milliseconds or `off`. |
| `SWW_LISTEN_ADDR` | `:8080` | Where `discriminator` listens; leave the host part empty. |
| `SWW_INSTANCE_NAME` | the container's host name | The name in every line `discriminator` logs, and in every alert and metric, such as `fsn1/discriminator`. |
| `SWW_MODE` | `enforce` | `observe` refuses nothing and makes no ban; each log line says what `enforce` would have done. |
| `SWW_IPV6_GROUP_PREFIX` | `64` | The prefix length of the IPv6 netblock that counts as one client, from 32 to 128. |
| `SWW_MAX_TRACKED_CLIENTS` | `20000` | The most clients kept, in memory and in `clients.json`; the least recently seen is dropped first. |
| `SWW_MAX_BANS` | `5000` | The most bans `discriminator` keeps of its own; bans an admin made do not count. |
| `SWW_ALLOW_NETS` | empty | Netblocks whose clients skip every check, such as your monitoring. |
| `SWW_RATE_LIMIT_EXEMPT_NETS` | empty | Netblocks whose clients the request and byte limits neither count nor refuse. |
| `SWW_DENY_NETS` | empty | Netblocks whose clients are refused. |
| `SWW_RATE_LIMIT_PER_MINUTE` | `120` | The most requests a client may make in a minute, a count or `off`; one more bans it. |
| `SWW_RATE_LIMIT_PER_HOUR` | `1500` | The most requests a client may make in an hour, a count or `off`; one more bans it. |
| `SWW_RATE_LIMIT_PER_DAY` | `6000` | The most requests a client may make in a day, a count or `off`; one more bans it. |
| `SWW_RATE_LIMIT_EXEMPT_PATHS` | empty | Path prefixes whose requests the request and byte limits neither count nor refuse, such as `/assets/`. |
| `SWW_BYTES_LIMIT_PER_MINUTE` | `off` | The most bytes a client's requests may carry in a minute, a size or `off`; the request that takes a client past any byte limit bans it. |
| `SWW_BYTES_LIMIT_PER_HOUR` | `50G` | The most bytes a client's requests may carry in an hour, a size or `off`. |
| `SWW_BYTES_LIMIT_PER_DAY` | `100G` | The most bytes a client's requests may carry in a day, a size or `off`. |
| `SWW_BYTES_COUNT` | `both` | Which body bytes the byte limits count: `response`, `request` or `both`. |
| `SWW_ERROR_BURST_THRESHOLD` | `30` | The most refusals by a rule file, a trap path or the Core Rule Set a client may get in a minute, a count or `off`; one more bans it. |
| `SWW_BAN_RESPONSE` | `403` | How a refused client is answered: `403`, `429` or `close`, which drops the connection. |
| `SWW_LIMIT_BAN_DURATION` | `1h` | The ban for a first broken limit. |
| `SWW_LIMIT_BAN_REPEAT_WINDOW` | `24h` | A limit broken again within this time after the last such ban ended gets a ban three times as long. |
| `SWW_MAX_BAN_DURATION` | `7d` | A ban for a broken limit that would be longer than this is permanent instead. |
| `SWW_ATTACK_BAN_DURATION` | `7d` | The ban for a first clear sign of attack: a `ban` rule or a trap path. |
| `SWW_BAN_SCOPE_V4_PREFIX` | `32` | The prefix length of the netblock a ban on an IPv4 client covers, from 0 to 32. |
| `SWW_LOOKUP_SOURCE` | `geojs` | Where each client's AS number and country come from: `geojs`, a web service, `file`, or `off`. |
| `SWW_LOOKUP_DB_PATH` | empty | The IPinfo Lite database file, in its `.mmdb` form, read while the source is `file`. |
| `SWW_LOOKUP_TIMEOUT` | `800ms` | How long a request waits for its client's first GeoJS answer when a setting needs it, and how long a request to GeoJS may take. |
| `SWW_ADD_LOOKUP_HEADERS` | `false` | `true` passes the app the client's AS number and country in `X-Client-ASN` and `X-Client-Country`. |
| `SWW_DENIED_COUNTRIES` | empty | Countries whose clients are refused, such as `cn,ru`. |
| `SWW_EXCLUSIVELY_ALLOWED_COUNTRIES` | empty | When set, the only countries whose clients get through; a client the lookup cannot place is refused too. |
| `SWW_ASN_LIMIT_PERCENT` | empty | AS numbers whose clients get a percentage of every request and byte limit, such as `AS14061:50,AS16276:25`. |
| `SWW_COUNTRY_LIMIT_PERCENT` | empty | The same by country, such as `cn:25`. |
| `SWW_ASN_BYTES_PERCENT` | empty | A percentage of the byte limits alone for the AS numbers listed, in place of their `SWW_ASN_LIMIT_PERCENT`. |
| `SWW_COUNTRY_BYTES_PERCENT` | empty | A percentage of the byte limits alone for the countries listed, in place of their `SWW_COUNTRY_LIMIT_PERCENT`. |
| `SWW_UNKNOWN_LIMIT_PERCENT` | `100` | The percentage of every limit a client without a country gets. |
| `SWW_ASN_LIMIT_PERCENT_URL` | unset | The URL of a text file of `AS<number>:<percent>` lines, fetched like a blocklist; where it and `SWW_ASN_LIMIT_PERCENT` both give a percentage, the lower applies. |
| `SWW_RULES_DIR` | `/etc/sww/rules.d` | The directory of the rule files, read at start and again when a file there changes. |
| `SWW_RULES_ENABLED` | `true` | `false` reads no rule file. |
| `SWW_TRAP_PATHS` | empty | Paths only scanners ask for, such as `/wp-login.php,/xmlrpc.php`; a request for one bans the client. |
| `SWW_WAF_MODE` | `block` | What the Core Rule Set does with a match: `block` refuses it with `403`, `detect` only logs and alerts it, `off` runs no rule. |
| `SWW_WAF_PARANOIA_LEVEL` | `1` | The Core Rule Set's paranoia level, from 1 to 4; each level up finds more attacks and takes more ordinary requests for attacks. |
| `SWW_WAF_ANOMALY_THRESHOLD` | `5` | The Core Rule Set score at which a request is a match, a whole number or `off`; one critical rule scores 5. |
| `SWW_WAF_DISABLED_RULES` | `920340,920420,920440,920640,930130,930140` | Core Rule Set rule ids switched off; a list you give replaces the default, so repeat these six to keep them off. |
| `SWW_WAF_EXEMPT_PATHS` | empty | Path prefixes the Core Rule Set does not inspect. |
| `SWW_WAF_BODY_LIMIT` | `off` | How much of a request body the Core Rule Set reads, a size up to `64K`; `off` reads none. |
| `SWW_CORE_RULE_SET_EXCLUSIONS_FILE` | unset | A file of Core Rule Set exclusions, as Coraza directives, that switch rules off for some fields or paths only. |
| `SWW_BLOCKLIST_URLS` | empty | Blocklists to fetch, text files of addresses and netblocks one to a line, such as `https://www.spamhaus.org/drop/drop.txt`. |
| `SWW_BLOCKLIST_REFRESH` | `24h` | How long after a list was last tried it is fetched again, `1h` or more. |
| `SWW_BLOCKLIST_ACTION` | `deny` | What a client on a blocklist gets: `deny`, `limit:<percent>` of every limit, or `log`. |
| `SWW_DNSBL_ZONES` | empty | DNS blocklists asked about each new client in the background, such as `dnsbl.dronebl.org`. |
| `SWW_DNSBL_RESOLVER` | unset | The resolver the zones are asked through, an IP address with an optional port; unset, the host's resolver is used. |
| `SWW_ABUSEIPDB_KEY` | unset | The key of your AbuseIPDB account; set, a client that has committed an offence is checked in the background. |
| `SWW_ABUSEIPDB_MIN_SCORE` | `75` | The least AbuseIPDB abuse confidence score, from 0 to 100, that is a hit. |
| `SWW_ABUSEIPDB_DAILY_BUDGET` | `900` | The most AbuseIPDB checks made in a day. |
| `SWW_CROWDSEC_LAPI_URL` | unset | The local API of a CrowdSec engine you run, such as `http://172.17.0.1:8080`; its decision list is fetched every minute, and a listed client is banned. |
| `SWW_CROWDSEC_LAPI_KEY` | unset | The key the engine gave for `smallwebwaf`, as `cscli bouncers add smallwebwaf` prints it; set with the URL, never alone. |
| `SWW_REPUTATION_ACTION` | `limit:25` | What a client listed by a DNS blocklist, or scored a hit by AbuseIPDB, gets: `deny`, `limit:<percent>` or `log`. |
| `SWW_REPUTATION_CACHE_TTL` | `24h` | How long a DNS blocklist verdict or an AbuseIPDB score is used. |
| `SWW_REPUTATION_TIMEOUT` | `2s` | How long a DNS blocklist query or an AbuseIPDB check may take. |
| `SWW_STATE_DIR` | `/var/lib/sww` | The directory of the state files, an absolute path. |
| `SWW_STATE_WRITE_DELAY` | `10s` | How long `bans.json` waits to be written after a ban is made, lifted or made permanent. |
| `SWW_STATE_COUNTER_INTERVAL` | `15m` | How often every state file is written. |
| `SWW_LOG_LEVEL` | `info` | The least severe of `discriminator`'s own messages that are written: `debug`, `info`, `warn` or `error`; request lines are always written. |
| `SWW_LOG_REQUEST_HEADERS` | `accept,accept-language,accept-encoding,content-type,origin,range` | The request headers whose values the request log records; `Authorization` and `Cookie` are never recorded. |
| `SWW_LOG_REMOTE_URL` | unset | A syslog server that also gets every line `discriminator` writes: `syslog+udp://`, `syslog+tcp://` or `syslog+tls://` with a host and a port. |
| `SWW_LOG_REMOTE_TLS_CA_FILE` | unset | A file of PEM certificates a `syslog+tls` server's certificate must chain to, instead of the host's own. |
| `SWW_LOG_REMOTE_BUFFER` | `10000` | The most lines held while they wait to be sent; past it, the oldest is dropped. |
| `SWW_LOG_REMOTE_FACILITY` | `local0` | The syslog facility of each record sent. |
| `SWW_LOG_REMOTE_APP_NAME` | `SWW_INSTANCE_NAME` | The app name in each syslog record, 1 to 48 printable ASCII characters without a space. |
| `SWW_ADMIN_TOKEN` | unset | The bearer token for the ban and client endpoints, at least 32 characters; unset, they answer `404`. |
| `SWW_METRICS_TOKEN` | unset | The bearer token for `/_sww/metrics`, at least 32 characters; unset, the metrics are off. |
| `SWW_METRICS_TOP_N` | `50` | How many AS numbers and how many countries get metric series of their own; the rest are summed as `other`. |
| `SWW_ALERT_WEBHOOK_URL` | unset | A webhook each alert is posted to as a JSON object. |
| `SWW_ALERT_WEBHOOK_HEADERS` | empty | Headers sent with each post, a list of `Name:value`, such as `Authorization:Bearer <token>`. |
| `SWW_ALERT_SLACK_WEBHOOK_URL` | unset | A Slack incoming webhook each alert is posted to as a message. |
| `SWW_ALERT_NTFY_URL` | unset | An ntfy topic each alert is published to, as its full URL, such as `https://ntfy.sh/my-alerts`. |
| `SWW_ALERT_NTFY_TOKEN` | unset | An ntfy access token sent with each alert. |
| `SWW_ALERT_EVENTS` | `ban,permanent_ban,waf_block,anomaly,reputation_hit,source_failure,file_error` | The events alerts are sent for; the hourly `summary` is sent whatever it says. |
| `SWW_ALERT_COOLDOWN` | `15m` | How long after an alert its repeats are held back and counted, a duration or `off`. |
| `SWW_ALERT_MAX_PER_HOUR` | `60` | The most alerts sent in an hour, a number or `off`; the rest are counted in the hour's `summary`. |
| `SWW_ANOMALY_CLIENT_REQUESTS_PER_MINUTE` | `off` | Alert when one client makes more requests than this in a minute, a count. |
| `SWW_ANOMALY_CLIENT_REQUESTS_PER_HOUR` | `off` | Alert when one client makes more requests than this in an hour, a count. |
| `SWW_ANOMALY_CLIENT_BYTES_PER_MINUTE` | `off` | Alert when one client's requests carry more bytes than this in a minute, a size. |
| `SWW_ANOMALY_CLIENT_BYTES_PER_HOUR` | `off` | Alert when one client's requests carry more bytes than this in an hour, a size. |
| `SWW_ANOMALY_NET_REQUESTS_PER_MINUTE` | `off` | Alert when the netblock around a client makes more requests than this in a minute, a count. |
| `SWW_ANOMALY_NET_REQUESTS_PER_HOUR` | `off` | Alert when the netblock around a client makes more requests than this in an hour, a count. |
| `SWW_ANOMALY_NET_BYTES_PER_MINUTE` | `off` | Alert when the netblock around a client carries more bytes than this in a minute, a size. |
| `SWW_ANOMALY_NET_BYTES_PER_HOUR` | `off` | Alert when the netblock around a client carries more bytes than this in an hour, a size. |
| `SWW_ANOMALY_NET_V4_PREFIX` | `24` | The prefix length of the netblock around an IPv4 client that the `SWW_ANOMALY_NET_` thresholds count, from 0 to 32. |
| `SWW_ANOMALY_NET_V6_PREFIX` | `48` | The prefix length of the netblock around an IPv6 client that the `SWW_ANOMALY_NET_` thresholds count, from 0 to 128. |
| `SWW_ANOMALY_ASN_REQUESTS_PER_MINUTE` | `off` | Alert when one AS number makes more requests than this in a minute, a count. |
| `SWW_ANOMALY_ASN_REQUESTS_PER_HOUR` | `off` | Alert when one AS number makes more requests than this in an hour, a count. |
| `SWW_ANOMALY_ASN_BYTES_PER_MINUTE` | `off` | Alert when one AS number carries more bytes than this in a minute, a size. |
| `SWW_ANOMALY_ASN_BYTES_PER_HOUR` | `off` | Alert when one AS number carries more bytes than this in an hour, a size. |
| `SWW_ANOMALY_TOTAL_REQUESTS_PER_MINUTE` | `off` | Alert when the whole service gets more requests than this in a minute, a count. |
| `SWW_ANOMALY_TOTAL_REQUESTS_PER_HOUR` | `off` | Alert when the whole service gets more requests than this in an hour, a count. |
| `SWW_ANOMALY_TOTAL_BYTES_PER_MINUTE` | `off` | Alert when the whole service carries more bytes than this in a minute, a size. |
| `SWW_ANOMALY_TOTAL_BYTES_PER_HOUR` | `off` | Alert when the whole service carries more bytes than this in an hour, a size. |
| `SWW_WATCH_NETS` | empty | Named netblocks the `SWW_WATCH_` thresholds count each as a whole, such as `office=203.0.113.0/24,scraper-x=198.51.100.0/22`. |
| `SWW_WATCH_REQUESTS_PER_MINUTE` | `off` | Alert when a watched netblock makes more requests than this in a minute, a count. |
| `SWW_WATCH_REQUESTS_PER_HOUR` | `off` | Alert when a watched netblock makes more requests than this in an hour, a count. |
| `SWW_WATCH_BYTES_PER_MINUTE` | `off` | Alert when a watched netblock carries more bytes than this in a minute, a size. |
| `SWW_WATCH_BYTES_PER_HOUR` | `off` | Alert when a watched netblock carries more bytes than this in an hour, a size. |
[`docs/settings.md`](docs/settings.md) gives the values each setting takes in
full, and the limits that are fixed rather than settings.
## docker-compose examples
Each example is a complete `compose.yaml`. `smallwebwaf` is the tag
`make docker` gives the image; on another host, use the name you pushed it
under, by digest. Docker Compose puts the services on a private network of its
own, where each reaches the others by service name. Each example publishes
`rproxy`'s port on the host, for trying it out.
### Smallest setup
One app, `rproxy` in front of it, and `discriminator` with a volume for its
state files, every setting at its default.
```yaml
services:
app:
# Your app, which listens on port 8081.
image: registry.example/app@sha256:0000000000000000000000000000000000000000000000000000000000000000
rproxy:
image: smallwebwaf
environment:
SWRP_WAF_BACKEND: http://discriminator:8080
SWRP_UPSTREAM_URL: http://app:8081
ports:
- "8080:8080"
discriminator:
image: smallwebwaf
environment:
SWW_COMMAND: discriminator
volumes:
- discriminator-state:/var/lib/sww
volumes:
discriminator-state:
```
### Custom per-address limits
For a site with no API:
- tighter limits for everyone;
- no limits for the office and the automation host;
- no checks for monitoring;
- a refused netblock;
- a smaller share of the limits for two hosting networks and one country;
- trap paths;
- `429` for a refused client.
```yaml
services:
app:
image: registry.example/app@sha256:0000000000000000000000000000000000000000000000000000000000000000
rproxy:
image: smallwebwaf
environment:
SWRP_WAF_BACKEND: http://discriminator:8080
SWRP_UPSTREAM_URL: http://app:8081
ports:
- "8080:8080"
discriminator:
image: smallwebwaf
environment:
SWW_COMMAND: discriminator
# Monitoring skips every check.
SWW_ALLOW_NETS: 192.0.2.10
# The office and the automation host are never rate limited.
SWW_RATE_LIMIT_EXEMPT_NETS: 203.0.113.0/24,198.51.100.7
# A netblock that sends nothing wanted.
SWW_DENY_NETS: 198.51.100.128/25
# Tighter limits for everyone else: a small static site.
SWW_RATE_LIMIT_PER_MINUTE: "60"
SWW_RATE_LIMIT_PER_HOUR: "600"
SWW_RATE_LIMIT_PER_DAY: "3000"
# Hosting networks and one country get a share of those limits.
SWW_ASN_LIMIT_PERCENT: AS14061:50,AS16276:25
SWW_COUNTRY_LIMIT_PERCENT: cn:25
# Paths only scanners ask for; one request bans the client.
SWW_TRAP_PATHS: /wp-login.php,/xmlrpc.php
# Answer a refused client with 429 rather than 403.
SWW_BAN_RESPONSE: "429"
SWW_LIMIT_BAN_DURATION: 30m
volumes:
- discriminator-state:/var/lib/sww
volumes:
discriminator-state:
```
### `rproxy` beside the app
The app is built on the `smallwebwaf` image, with `rproxy` inside its container.
`app/` holds the `Dockerfile` and `app.run` from "`rproxy` in the app's
container". `rproxy` answers `503` to every request while `discriminator` is
down, and `discriminator`:
- observes before it enforces;
- looks addresses up in a local database rather than GeoJS;
- sends alerts to ntfy;
- reads its ntfy token from a file.
```yaml
services:
app:
# A Dockerfile built FROM the smallwebwaf image, with rproxy inside.
build: ./app
environment:
SWRP_WAF_BACKEND: http://discriminator:8080
# Answer 503 rather than pass a request on while discriminator is down.
SWRP_DEFAULT_DISPOSITION: deny
ports:
- "8080:8080"
discriminator:
image: smallwebwaf
environment:
SWW_COMMAND: discriminator
SWW_INSTANCE_NAME: fsn1/discriminator
# Refuse nothing yet; log what enforce mode would have done.
SWW_MODE: observe
# Look addresses up in a local IPinfo Lite database, never GeoJS.
SWW_LOOKUP_SOURCE: file
SWW_LOOKUP_DB_PATH: /var/lib/ipinfo/ipinfo_lite.mmdb
# Alerts to an ntfy topic, with its token read from a file.
SWW_ALERT_NTFY_URL: https://ntfy.example/smallwebwaf
SWW_ALERT_NTFY_TOKEN_FILE: /etc/sww/tokens/ntfy
SWW_ALERT_EVENTS: ban,permanent_ban,waf_block,source_failure,file_error
volumes:
- discriminator-state:/var/lib/sww
- /srv/ipinfo:/var/lib/ipinfo:ro
- /srv/sww/tokens:/etc/sww/tokens:ro
volumes:
discriminator-state:
```
The database is mounted by its directory, not by file, so that a replaced
database is seen. A token file belongs to uid 65532, the `sww` user, with mode
`0400`. This one holds an access token the ntfy server issued, which
`ntfy token add <user>` prints there:
```sh
mkdir -p /srv/sww/tokens
# <token> is the access token that ntfy printed.
echo '<token>' > /srv/sww/tokens/ntfy
chown 65532:65532 /srv/sww/tokens/ntfy
chmod 0400 /srv/sww/tokens/ntfy
```
## Design
How it works inside. [`SPEC.md`](SPEC.md) gives every rule in full, and why.
### What happens to a request
A request goes through these steps, in this order. Once `discriminator` refuses
a request, the steps after that are skipped, apart from the report, and nothing
of the request reaches the app.
`rproxy` takes the first two:
1. The health check, `GET /_sww/healthz`, is answered at once.
2. The visitor's address is worked out from `X-Forwarded-For`, believed only
from `SWRP_TRUSTED_PROXIES`. `rproxy` sends `discriminator` the request as
the visitor sent it, with the first 64 KiB of its body.
`discriminator` takes the checks:
3. The static lists, `SWW_ALLOW_NETS` and `SWW_DENY_NETS`.
4. The bans.
5. The lookup of the client's AS number and country.
6. The country lists.
7. The reputation sources.
8. The client's limit percentage, from its AS number, its country or a
reputation hit.
9. The rate limits.
10. The trap paths.
11. The rule files.
12. The header limits, and then the Core Rule Set.
13. A path under `/_sww/` is answered `404`, so that the app never sees that
prefix.
`rproxy` takes the rest, with `discriminator` counting at the end:
14. The request is passed to the app, streaming.
15. After the answer, `rproxy` sends `discriminator` a report with the status
and the bytes each way. For an allowed request, `discriminator` counts the
bytes toward the byte limits and adds the request to the client's history.
A refused visitor is answered with `SWW_BAN_RESPONSE`. A `block` rule or a Core
Rule Set match answers `403` and bans nobody, since the Core Rule Set has false
positives; such refusals count toward `SWW_ERROR_BURST_THRESHOLD` instead. A
request over the header limits of step 12 is answered `431`, and bans nobody
either. `rproxy` itself answers `405` to a method it does not pass on, and the
status for a size or time limit, such as `413` for a body too large.
### Clients and bans
- A client is one IPv4 address or one IPv6 netblock of `SWW_IPV6_GROUP_PREFIX`,
since one abuser usually controls a whole /64.
- Each limit is counted over a sliding window with a few integers per client.
The table of clients and the table of bans each have a bound
(`SWW_MAX_TRACKED_CLIENTS`, `SWW_MAX_BANS`), so memory is bounded too.
- A ban refuses every request from its netblock until it ends. Requests refused
under a ban count toward no limit. A permanent ban ends only when an admin
lifts it.
- Every ban carries notes: the client's AS number and country, the limit it
broke or the rule it matched, the request that caused it, and its earlier
bans. An admin adds, keeps or lifts a ban by editing `bans.json` or through
the ban endpoints (see [`docs/admin-endpoints.md`](docs/admin-endpoints.md)).
### Attack detection
- The Core Rule Set reads the method, the URL with its query string, and the
headers of every request, and no body unless `SWW_WAF_BODY_LIMIT` is set. In
front of a code forge, bodies carry what people write and publish, which the
rules take for attacks.
- `smallwebwaf` changes the Core Rule Set in eight ways so that it lets ordinary
requests to a code forge through, such as git over HTTP and sign-in through
Git Credential Manager. On gitea's own paths, its searches, file names and
branch names get through too. No setting undoes the changes; "Attack
detection" in [`SPEC.md`](SPEC.md) lists them.
- `SWW_CORE_RULE_SET_EXCLUSIONS_FILE` switches single rules off for an app's own
fields or paths.
- Rule files are plain text, one rule to a line, edited by hand and read again
while `discriminator` runs. The image ships one file of probes no real visitor
sends (see [`docs/rules.md`](docs/rules.md)).
### State files
`discriminator` keeps everything in memory, and the five JSON files in
`SWW_STATE_DIR` hold a copy: `bans.json`, `clients.json`, `lookups.json`,
`reputation.json` and `alerts.json`. Each is written whole, to a temporary file
renamed over the real one, so a crash leaves a complete file. `discriminator`
notices a file edited on disk and takes the edit in; an edit that does not parse
is set aside as `<name>.bad`, and never stops the running process (see
[`docs/state-files.md`](docs/state-files.md)).
### The image and its processes
- The image is built on Ubuntu 26.04 LTS, pinned by digest. Its Ubuntu packages
come from Ubuntu's archive, and nixpkgs is fixed at one release. An app's
`Dockerfile` installs a package with `nix-env -iA nixpkgs.<name>` and gets the
same package each time it is built (see [`docs/image.md`](docs/image.md)).
- runit, a service supervisor, runs `sww` as the `sww` user (uid and gid 65532)
and starts it again when it exits. The `run` script of `discriminator` gives
the state directory to the `sww` user at each start, so a volume needs no
change of owner.
- `rproxy` and `discriminator` use no token between them. `discriminator`'s own
endpoints, under `/_sww/`, are for your admin tools and your metrics
collector, at its own address on the private network; nothing routes the
internet there.
- `docker stop` gives requests in progress five seconds to finish. With `rproxy`
in the app's container, the app must keep answering for five seconds after
`SIGTERM` for that to help them.
- Only faults found at start stop a process: an invalid setting, a rule file or
state file that does not parse, a lookup database that cannot be read, or an
address it cannot listen on. Once running, a failing lookup service,
reputation source or alert destination never takes `discriminator` down.
### Packages
- `cmd/sww`: the binary, which only calls `internal/sww`.
- `internal/sww`: the process, as the command it is given, and the health check.
- `internal/config`: reads the settings, the one place they are read.
- `internal/rproxy`: the reverse proxy in front of one app.
- `internal/discriminator`: `discriminator`'s server, which runs the checks and
answers its own endpoints.
- `internal/ratelimit`, `internal/bans`, `internal/rules`, `internal/waf`,
`internal/lookup`, `internal/reputation`, `internal/anomaly` and
`internal/alerts`: one check or source each.
- `internal/state`, `internal/requestlog`, `internal/remotelog` and
`internal/metrics`: the state files, the log lines, the syslog sender and the
metrics.
## Rationale
Small self-hosted sites receive a great deal of traffic nobody asked for:
- scrapers that ignore `robots.txt` and crawl every commit of every repository
on a public git server;
- scanners walking through lists of WordPress and `.env` paths;
- credential-guessing bots.
Most of it comes from a small number of hosting networks and countries. A
single-person operation has no abuse desk and no CDN contract. It needs
something small that can be put in front of its services and left alone.
The existing tools each solve part of this. Rule-based firewalls catch attack
payloads but do not limit request rates. Rate limiters count requests but cannot
tell a residential visitor from a rented server farm. The products that do most
of it want a database and a web console. None of them can say "clients from
these networks are banned after half as many requests as anyone else".
[`EVALUATION.md`](EVALUATION.md) goes through the candidates one by one.
## Entrypoints
This repository adheres to the
[Scripts to Rule Them All](https://github.com/github/scripts-to-rule-them-all)
standard. The scripts in `script/` are the entrypoints for working on it, and
the `Makefile` targets are thin shims that call them. The scripts are POSIX sh.
The tests and the linter run in Docker, as phases of the `Dockerfile`, and never
on the host.
- `script/bootstrap`: installs on the host what the other scripts need, with
`make bootstrap`:
- `make`, `git` and `curl`;
- Go, for `gofmt`;
- node, yarn and prettier.
- `script/setup`: readies a fresh clone: `script/bootstrap`, then
`script/install-precommit`. `make setup`.
- `script/projectname`: prints `smallwebwaf`, which the other scripts tag their
images with.
- `script/test`: checks that `go.mod` and `go.sum` are tidy, then runs the
tests, as the `test` phase of the `Dockerfile`. `make test`.
- `script/tidy`: writes `go.mod` and `go.sum` as `go mod tidy` writes them, in
the `tidy` stage of the `Dockerfile`. `make tidy`.
- `script/lint`: runs golangci-lint, as the `lint` phase of the `Dockerfile`.
`make lint`.
- `script/fmt`: formats the Go code with `gofmt` and the Markdown with prettier.
`make fmt`.
- `script/fmt-check`: checks the formatting and changes nothing.
`make fmt-check`.
- `script/check`: runs `script/test`, `script/lint` and `script/fmt-check`.
`make check`.
- `script/docker`: builds the image, whose build runs the tests and the linter
first. `make docker`.
- `script/cibuild`: what CI runs: `script/bootstrap`, `script/check`, then the
image build.
- `script/precommit`: run by the git pre-commit hook; runs `script/check`.
- `script/install-precommit`: installs that hook. `make hooks`.
- `script/build`: builds `bin/sww` with the Go on your host. `make build`.
- `script/run`: builds `bin/sww` and runs `discriminator` and `rproxy` on the
host, with the settings in your environment. `make run`. Unless your settings
say otherwise:
- `rproxy` listens on port 8080, in front of an app at
`http://127.0.0.1:8081`;
- `discriminator` listens on port 8090;
- its state files go in `bin/state`;
- its rule files are those of `share/rules.d`.
- `script/example-app`: builds the image and the example app
(`deploy/example-app`) on it, runs the app with `rproxy` in its container and
`discriminator` in another, and checks them. Then it removes the containers,
the network, the volumes and the images. Needs network access.
`make example-app`. It checks:
- the health checks;
- a request passed to the app;
- a ban for a broken limit, and a ban for a probe made permanent;
- that only `discriminator`'s container changes the state directory's owner;
- with `discriminator` stopped, the app still answering through `rproxy`;
- with `discriminator` started again, bans applying again;
- orderly stops with `sv stop` and `docker stop`;
- bans surviving a new container on the same volume;
- a setting given as a file.
## TODO
- Planned, as "Planned, not built" in [`SPEC.md`](SPEC.md) describes: sending
the log over RELP.
## Documents
- [`SPEC.md`](SPEC.md): how `smallwebwaf` behaves, and why.
- [`EVALUATION.md`](EVALUATION.md): what already exists, what each tool covers
and misses, and why none was adopted.
- [`REPO_POLICIES.md`](REPO_POLICIES.md): the policies this repository follows.
- [`docs/settings.md`](docs/settings.md): every setting and the values it takes.
- [`docs/rules.md`](docs/rules.md): the rule file format and the default file.
- [`docs/admin-endpoints.md`](docs/admin-endpoints.md): the endpoints under
`/_sww/`, with examples.
- [`docs/request-log.md`](docs/request-log.md): the request log's fields.
- [`docs/alerts.md`](docs/alerts.md): the alert events and what each destination
gets.
- [`docs/metrics.md`](docs/metrics.md): the metrics.
- [`docs/state-files.md`](docs/state-files.md): the state files and what each
holds.
- [`docs/image.md`](docs/image.md): what the image holds and how it is pinned.
## License
MIT. See [`LICENSE`](LICENSE).
## Author
[@sneak](https://sneak.berlin)
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