Admin endpoints for bans and clients on the single listener (closes #27)

SWWAF_ADMIN_TOKEN, or its _FILE form, opens GET and POST
/_smallwebwaf/bans, DELETE /_smallwebwaf/bans/<client> and GET
/_smallwebwaf/clients/<ip>. Unset, they answer 404; a missing or wrong
token gets 401, in observe mode too. They go through every check, as
the metrics do. POST takes a netblock, not IPv4-mapped and without a
zone, or a client's address, a duration or permanent, and a reason, and
makes an admin ban even while another lasts. DELETE lifts every active
ban covering the address, kept and marked lifted. Bans come back as
bans.json entries; a client as clients.json holds it, with its bans.

Judgement call: answers leave out bans.json's version field.
Judgement call: DELETE takes an address, not a netblock.
Rule suppressed: gosec G304 on a test reading bans.json.

Model: opus-5-5

internal/config/config_test.go

@@ -50,6 +50,7 @@ const (
 	stateDir                = "SWWAF_STATE_DIR"
 	stateWriteDelay         = "SWWAF_STATE_WRITE_DELAY"
 	stateCounterInterval    = "SWWAF_STATE_COUNTER_INTERVAL"
+	adminToken              = "SWWAF_ADMIN_TOKEN"   //nolint:gosec // the setting's name
 	metricsToken            = "SWWAF_METRICS_TOKEN" //nolint:gosec // the setting's name
 	metricsTopN             = "SWWAF_METRICS_TOP_N"
 	instanceName            = "SWWAF_INSTANCE_NAME"
@@ -81,8 +82,12 @@ rlG9y/jrJb6ORy3kTLWo2EA0BA67vuI=
 -----END CERTIFICATE-----
 `
 
-// token is a token of 32 characters, the shortest allowed.
-const token = "0123456789abcdef0123456789abcdef"
+// token is a token of 32 characters, the shortest allowed, and
+// otherToken another.
+const (
+	token      = "0123456789abcdef0123456789abcdef"
+	otherToken = "fedcba9876543210fedcba9876543210"
+)
 
 // instance is an SWWAF_INSTANCE_NAME that is a valid app name too, and
 // remoteURL an SWWAF_LOG_REMOTE_URL, for the tests that send the lines.
@@ -693,32 +698,40 @@ func TestShortTokenStopsTheStartWithoutShowingIt(t *testing.T) {
 	t.Parallel()
 
 	// Characters are counted, not bytes: each é takes two.
-	for _, value := range []string{"", token[1:], strings.Repeat("é", 31)} {
-		t.Run(value, func(t *testing.T) {
-			t.Parallel()
+	for _, name := range []string{adminToken, metricsToken} {
+		for _, value := range []string{"", token[1:], strings.Repeat("é", 31)} {
+			t.Run(name+"="+value, func(t *testing.T) {
+				t.Parallel()
 
-			_, err := config.FromEnvironment(environment{metricsToken: value}.lookupEnv)
+				_, err := config.FromEnvironment(environment{name: value}.lookupEnv)
 
-			want := metricsToken + ": is shorter than 32 characters"
-			if err == nil || err.Error() != want {
-				t.Errorf("error %v, want %s", err, want)
-			}
-		})
+				want := name + ": is shorter than 32 characters"
+				if err == nil || err.Error() != want {
+					t.Errorf("error %v, want %s", err, want)
+				}
+			})
+		}
 	}
 }
 
-func TestTokenIsLoggedMasked(t *testing.T) {
+func TestTokensAreReadAndLoggedMasked(t *testing.T) {
 	t.Parallel()
 
-	cfg := fromEnvironment(t, environment{metricsToken: token})
+	cfg := fromEnvironment(t, environment{adminToken: otherToken, metricsToken: token})
+	if cfg.AdminToken != otherToken || cfg.MetricsToken != token {
+		t.Errorf("admin token %q and metrics token %q, want %q and %q",
+			cfg.AdminToken, cfg.MetricsToken, otherToken, token)
+	}
 
 	var out bytes.Buffer
 
 	slog.New(slog.NewJSONHandler(&out, nil)).Info("starting", "settings", cfg)
 
-	if strings.Contains(out.String(), token) ||
-		!strings.Contains(out.String(), `"`+metricsToken+`":"********"`) {
-		t.Errorf("the token is not logged masked: %s", out.String())
+	logged := out.String()
+	if strings.Contains(logged, token) || strings.Contains(logged, otherToken) ||
+		!strings.Contains(logged, `"`+adminToken+`":"********"`) ||
+		!strings.Contains(logged, `"`+metricsToken+`":"********"`) {
+		t.Errorf("the tokens are not logged masked: %s", logged)
 	}
 }
 
@@ -901,6 +914,7 @@ func TestLogsEachSettingWithItsValue(t *testing.T) {
 		stateDir:                "/var/lib/smallwebwaf",
 		stateWriteDelay:         "10s",
 		stateCounterInterval:    "15m",
+		adminToken:              "",
 		metricsToken:            "",
 		metricsTopN:             "50",
 		instanceName:            hostname,