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

gitea's fixes (its parameters, its cookies and gitea.conf) now apply
only to a hostname SWW_APPS lists gitea for, or to every hostname while
it is unset. Each app's fixes are one .conf file, whose first rule skips
the rest unless Inspect sets tx.app_<name>, and one entry in apps.

Model: opus-5-5

SPEC.md

@@ -681,12 +681,8 @@ through. An app's fixes hold for the hostnames `SWW_APPS` lists the app for:
   Set empty, `SWW_APPS` lists no hostname.
 - Unset, every app's fixes hold for every hostname. An app's fixes then weaken
   the check of any other app that serves the same paths or fields.
-- Any of these mistakes stops the start:
-    - an unknown app;
-    - a hostname that is not a DNS name, such as `*.example.com`;
-    - a hostname listed twice;
-    - an app listed twice for one hostname;
-    - an entry without a colon.
+- The start stops on an unknown app, a hostname listed twice, an app listed
+  twice for one hostname, or an entry without a colon.
 
 `gitea` is the only app supported. Each app's fixes are in one file, such as
 `internal/waf/gitea.conf`, and one entry of `apps` in `internal/waf/waf.go`.

docs/settings.md

@@ -210,12 +210,8 @@ between the two (see "The image's command" below).
     - A hostname not listed gets no app's fixes, so every rule checks it in
       full. Set empty, it lists no hostname.
     - Unset, every app's fixes apply to every hostname.
-    - Any of these mistakes stops the start:
-        - an unknown app;
-        - a hostname that is not a DNS name, such as `*.example.com`;
-        - a hostname listed twice;
-        - an app listed twice for one hostname;
-        - an entry without a colon.
+    - An unknown app, a hostname listed twice, an app listed twice for one
+      hostname, or an entry without a colon stops the start.
 - `SWW_ERROR_BURST_THRESHOLD` (default `30`): the most refusals of one client in
   a minute (see "Attack detection" in `SPEC.md`). A count or `off`.
 

internal/config/config.go

@@ -406,7 +406,6 @@ var (
 		"is not a path starting with / and without a ?, such as /wp-login.php")
 	errNotAppsEntry = errors.New(
 		"is not a hostname, : and a list of apps, such as git.example.com:gitea")
-	errNotHostname      = errors.New("is not a DNS name such as git.example.com")
 	errNotApp           = errors.New("is not an app sww has fixes for; the apps are")
 	errNotWAFMode       = errors.New("is not off, detect or block")
 	errNotParanoiaLevel = errors.New("is not a paranoia level, from 1 to 4")
@@ -1676,10 +1675,9 @@ func parseTrapPaths(value string) ([]string, error) {
 // parseApps reads the apps each hostname serves: entries separated by
 // semicolons, each a hostname, a colon, and a comma-separated list of the
 // names waf.AppNames returns, such as
-// git.example.com:gitea;cloud.example.com:nextcloud,wordpress. Each
-// hostname is a DNS name, without a wildcard. It returns them by hostname
-// in lowercase, since a hostname is matched without regard to case. An
-// empty value lists no hostname.
+// git.example.com:gitea;cloud.example.com:nextcloud,wordpress. It returns
+// them by hostname in lowercase, since a hostname is matched without
+// regard to case. An empty value lists no hostname.
 func parseApps(value string) (map[string][]string, error) {
 	apps := map[string][]string{}
 
@@ -1698,10 +1696,6 @@ func parseApps(value string) (map[string][]string, error) {
 			return nil, fmt.Errorf("%q %w", entry, errNotAppsEntry)
 		}
 
-		if !isZone(hostname) {
-			return nil, fmt.Errorf("%q %w", hostname, errNotHostname)
-		}
-
 		if _, listed := apps[hostname]; listed {
 			return nil, fmt.Errorf("%q %w", hostname, errListedTwice)
 		}
@@ -2158,8 +2152,7 @@ func MaskZoneKey(zone string) string {
 	return masked + "." + rest
 }
 
-// isZone reports whether each label of zone is as parseZones takes it. It
-// also checks the hostnames of SWW_APPS, which are DNS names too.
+// isZone reports whether each label of zone is as parseZones takes it.
 func isZone(zone string) bool {
 	for label := range strings.SplitSeq(zone, ".") {
 		badChar := strings.ContainsFunc(label, func(char rune) bool {

internal/config/config_test.go

@@ -603,20 +603,14 @@ func TestApps(t *testing.T) {
 func TestInvalidAppsStopsTheStart(t *testing.T) {
 	t.Parallel()
 
-	const (
-		notEntry = " is not a hostname, : and a list of apps, " +
-			"such as git.example.com:gitea"
-		notHostname = " is not a DNS name such as git.example.com"
-	)
+	const notEntry = " is not a hostname, : and a list of apps, " +
+		"such as git.example.com:gitea"
 
 	for _, tc := range []struct{ value, want string }{
 		{"git.example.com:gitea;blog.example.com", `"blog.example.com"` + notEntry},
 		{"git.example.com:gitea;", `""` + notEntry},
 		{":gitea", `":gitea"` + notEntry},
 		{"git.example.com:", `"git.example.com:"` + notEntry},
-		{"*.example.com:gitea", `"*.example.com"` + notHostname},
-		{"git.example.com/:gitea", `"git.example.com/"` + notHostname},
-		{"git example.com:gitea", `"git example.com"` + notHostname},
 		{
 			"git.example.com:gitea,nextcloud",
 			`"nextcloud" is not an app sww has fixes for; the apps are gitea`,

internal/discriminator/coreruleset_test.go

@@ -10,7 +10,6 @@ import (
 	"testing"
 
 	"sneak.berlin/go/smallwebwaf/internal/alerts"
-	"sneak.berlin/go/smallwebwaf/internal/discriminator"
 	"sneak.berlin/go/smallwebwaf/internal/ratelimit"
 	"sneak.berlin/go/smallwebwaf/internal/requestlog"
 )
@@ -22,7 +21,6 @@ const (
 	wafDisabledRules    = "SWW_WAF_DISABLED_RULES"
 	wafExemptPaths      = "SWW_WAF_EXEMPT_PATHS"
 	wafBodyLimit        = "SWW_WAF_BODY_LIMIT"
-	apps                = "SWW_APPS"
 	block               = "block"
 	detect              = "detect"
 )
@@ -239,27 +237,6 @@ func TestDisabledRulesSwitchOffWhatGiteaWouldBeRefused(t *testing.T) {
 	}
 }
 
-func TestGiteasFixesApplyOnlyToAHostnameThatServesGitea(t *testing.T) {
-	t.Parallel()
-
-	// Only gitea's fixes let a file name through in path, a parameter
-	// gitea sends file names in.
-	const fileName = "/?path=.gitignore"
-
-	s := startDiscriminator(t, "", map[string]string{
-		wafMode: block, apps: siteA + ":gitea",
-	})
-
-	wantDisposition(t, do(t, s.question(siteA, client, fileName)),
-		http.StatusOK, discriminator.DispositionAllow)
-	wantDisposition(t, do(t, s.question(siteB, client, fileName)),
-		http.StatusForbidden, discriminator.DispositionDeny)
-
-	lines := s.out.requestLines(t, 2)
-	wantLine(t, lines[0], http.StatusOK, requestlog.ActionForward)
-	wantLine(t, lines[1], http.StatusForbidden, requestlog.ActionWAFBlocked)
-}
-
 func TestAttackInAFormBodyIsRefusedOnlyWhileBodiesAreRead(t *testing.T) {
 	t.Parallel()