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SWWAF_WAF_BODY_LIMIT (default off, at most 1G) has the Core Rule Set read form data and multipart up to the limit, the rest streaming on, and JSON and XML (with +json, text/json and +xml) no larger than it. The part read is held for the app. A size or time limit met while reading ends the request. Content-Encoding is refused again on these kinds. A body Coraza cannot parse, or a multipart body failing its strict checks, adds 5, but not a multipart body reaching the limit. Coraza is built with no_fs_access, so writes no file. Rule 900300 moves to phase 2. Judgement call: Content-Encoding is refused on a JSON or XML body too large to read, as SPEC.md allows. Model: opus-5-5
125 lines
3.8 KiB
Go
125 lines
3.8 KiB
Go
package proxy
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import (
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"errors"
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"net/http"
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"os"
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"time"
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"sneak.berlin/go/smallwebwaf/internal/alerts"
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"sneak.berlin/go/smallwebwaf/internal/config"
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"sneak.berlin/go/smallwebwaf/internal/requestlog"
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"sneak.berlin/go/smallwebwaf/internal/waf"
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)
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// checkCoreRuleSet inspects the request with the Core Rule Set, unless
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// SWWAF_WAF_MODE is off or SWWAF_WAF_EXEMPT_PATHS exempts its path, as
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// pathExempt decides, and notes the rules it matched and its score in the
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// log line, and the rules in the metrics. A score at or over
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// SWWAF_WAF_ANOMALY_THRESHOLD is a match: it raises the waf_block alert,
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// and in block mode refuses the request, which is an offence its client's
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// history counts, and so returns ActionWAFBlocked. It returns "" for a
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// request it does not refuse, and for one whose body meets a size or time
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// limit while the Core Rule Set reads it, which it notes nothing of.
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func (rq *request) checkCoreRuleSet() string {
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cfg := rq.h.config
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if cfg.WAFMode == config.WAFModeOff || pathExempt(rq.in.URL, cfg.WAFExemptPaths) {
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return ""
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}
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start := time.Now()
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result := rq.inspect()
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if rq.refused.Load() != nil {
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return "" // the refusal for that limit, which check returns
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}
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rq.line.DurationWAF = new(requestlog.Milliseconds(time.Since(start)))
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rq.line.WAFRuleIDs = result.RuleIDs
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rq.line.WAFScore = &result.Score
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for _, id := range result.RuleIDs {
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rq.h.metrics.WAFMatched(cfg.WAFMode, id)
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}
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threshold := cfg.WAFAnomalyThreshold
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if threshold == 0 || result.Score < threshold {
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return ""
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}
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rq.alertWAFBlock(result)
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if cfg.WAFMode == config.WAFModeDetect {
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return ""
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}
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rq.wafBlocked = true
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return requestlog.ActionWAFBlocked
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}
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// inspect runs the Core Rule Set on the request, which reads the part of
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// its body it inspects within SWWAF_CLIENT_REQUEST_TIMEOUT, and keeps that
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// part for the app. A client that runs out of time is refused with 408
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// here, and a body over SWWAF_REQUEST_MAX_BYTES with 413 as it is read;
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// check returns the refusal. A body that breaks off for any other reason
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// is passed on as far as it came, and the request to the app fails there,
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// as it would have without the Core Rule Set.
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func (rq *request) inspect() waf.Result {
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if rq.body == nil {
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// Nothing is read of no body, so nothing can go wrong reading it.
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result, _, _ := rq.h.coreRuleSet.Inspect(rq.in, rq.client, http.NoBody)
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return result
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}
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_ = rq.rc.SetReadDeadline(rq.clientRequestDeadline())
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result, read, err := rq.h.coreRuleSet.Inspect(rq.in, rq.client, rq.body)
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// The timeouts that run while the request goes to the app take over.
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_ = rq.rc.SetReadDeadline(time.Time{})
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rq.body.readByCoreRuleSet = read
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if errors.Is(err, os.ErrDeadlineExceeded) {
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rq.refuse(refusal{
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status: http.StatusRequestTimeout,
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action: requestlog.ActionTimedOut,
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limit: "SWWAF_CLIENT_REQUEST_TIMEOUT",
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})
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}
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return result
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}
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// alertWAFBlock raises the waf_block alert for the request, which the Core
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// Rule Set scored at result, at or over SWWAF_WAF_ANOMALY_THRESHOLD. Its
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// detail gives the rule ids, the score, the method and the path with the
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// query, and, for a request that is not refused for it, the mode: detect,
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// or observe in observe mode.
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func (rq *request) alertWAFBlock(result waf.Result) {
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detail := map[string]any{
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"rule_ids": result.RuleIDs,
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"score": result.Score,
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"method": rq.in.Method,
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"path": rq.in.URL.RequestURI(),
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}
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switch {
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case rq.h.config.WAFMode == config.WAFModeDetect:
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detail["mode"] = config.WAFModeDetect
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case rq.h.config.Observe:
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detail["mode"] = "observe"
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}
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rq.h.alerts.Raise(alerts.Alert{
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Event: alerts.EventWAFBlock,
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Client: rq.client,
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Netblock: rq.h.clientGroup(rq.client),
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ASN: rq.line.ASN,
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ASName: rq.line.ASName,
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Country: rq.line.Country,
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Reason: "scored by the Core Rule Set at or over SWWAF_WAF_ANOMALY_THRESHOLD",
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Detail: detail,
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})
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}
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