SWW_APPS: an app's Core Rule Set fixes apply only to the hostnames that serve it (closes #220)

Each app's fixes are one .conf file and one entry in apps. They apply
only while Inspect has set the app's transaction variable, such as
tx.app_gitea. SWW_APPS names each hostname's apps. A hostname gets only
its apps' fixes; while SWW_APPS is unset, every hostname gets every
app's fixes.

A hostname in SWW_APPS that is not a DNS name, such as *.example.com,
stops the start. Unset, SWW_APPS is logged at start as null; set
empty, as "".

Model: opus-5-5

internal/coreruleset/mediawiki_test.go

@@ -4,11 +4,16 @@ import (
 	"net/http"
 	"slices"
 	"testing"
+
+	"sneak.berlin/go/smallwebwaf/internal/coreruleset"
 )
 
 // mediawikiThreshold is SWW_WAF_ANOMALY_THRESHOLD's default.
 const mediawikiThreshold = 5
 
+// mediawiki is MediaWiki's name in SWW_APPS.
+const mediawiki = "mediawiki"
+
 // mediawikiEdit is the address MediaWiki's edit form posts to.
 const mediawikiEdit = "/index.php?title=Example&action=submit"
 
@@ -45,7 +50,44 @@ const (
 func TestOrdinaryMediaWikiRequestsPass(t *testing.T) {
 	t.Parallel()
 
-	wantRecordedRequestsPass(t, "mediawiki-requests.txt")
+	wantRecordedRequestsPass(t, "mediawiki-requests.txt", mediawiki)
+}
+
+func TestMediaWikiFixesApplyOnlyToAHostnameThatServesMediaWiki(t *testing.T) {
+	t.Parallel()
+
+	crs := servingApps(t, map[string][]string{
+		giteaHost: {gitea}, otherHost: {mediawiki},
+	})
+
+	// A search, which only MediaWiki's fixes let through.
+	search := get("/index.php?title=Special:Search&search=python3")
+
+	wantResult(t, crs, withHost(search, otherHost), coreruleset.Result{})
+	wantResult(t, crs, withHost(search, giteaHost), matched(932260))
+}
+
+func TestMediaWikiWatchlistFixAppliesOnlyToAHostnameThatServesMediaWiki(t *testing.T) {
+	t.Parallel()
+
+	crs := shared(t, coreruleset.Params{
+		ParanoiaLevel: 1, DisabledRules: defaultDisabledRules, BodyLimit: bodyLimit,
+		Apps: map[string][]string{giteaHost: {gitea}, otherHost: {mediawiki}},
+	})
+
+	// A watchlist that only the phase 2 rule 900916 lets through.
+	r := request{http.MethodPost, mediawikiWatchlist.target, []string{formData}}
+	body := mediawikiWatchlist.field + "Lighthouse%20notes%0D%0APython3%20notes"
+
+	got, _ := inspectBody(t, crs, withHost(r, otherHost), body)
+	if got.Score >= mediawikiThreshold {
+		t.Errorf("POST %s %s on %s refused: %+v", r.target, body, otherHost, got)
+	}
+
+	got, _ = inspectBody(t, crs, withHost(r, giteaHost), body)
+	if got.Score < mediawikiThreshold {
+		t.Errorf("POST %s %s on %s let through: %+v", r.target, body, giteaHost, got)
+	}
 }
 
 // mediawikiQueryFields and mediawikiBodyFields together hold every field that