Log the rest of the request log's fields (closes #79)

Each request log line now has the fields "Request log" in SPEC.md lists
whose features are built: instance (SWWAF_INSTANCE_NAME), scheme,
request_id (a trusted proxy's X-Request-ID or a new one, sent on to the
app), forwarded_for, client_group, content_type, content_length, the
headers SWWAF_LOG_REQUEST_HEADERS names, has_authorization, has_cookie,
websocket, response_content_type, cache_control, location, counts and
the timings. Authorization, Cookie and Set-Cookie values are never
logged. An entry of SWWAF_LOG_REQUEST_HEADERS that is not a header name,
or is Host or Transfer-Encoding, stops the start.

Deviation: counts has request totals only.
Deviation: SWWAF_INSTANCE_NAME is on request lines only.

Model: opus-5-5

internal/config/config_test.go

@@ -6,6 +6,7 @@ import (
 	"log/slog"
 	"maps"
 	"net/netip"
+	"os"
 	"slices"
 	"strings"
 	"testing"
@@ -47,8 +48,14 @@ const (
 	stateCounterInterval    = "SWWAF_STATE_COUNTER_INTERVAL"
 	metricsToken            = "SWWAF_METRICS_TOKEN" //nolint:gosec // the setting's name
 	metricsTopN             = "SWWAF_METRICS_TOP_N"
+	instanceName            = "SWWAF_INSTANCE_NAME"
+	logRequestHeaders       = "SWWAF_LOG_REQUEST_HEADERS"
 )
 
+// defaultLogRequestHeaders is the default of SWWAF_LOG_REQUEST_HEADERS.
+const defaultLogRequestHeaders = "accept,accept-language,accept-encoding," +
+	"content-type,origin,range"
+
 // token is a token of 32 characters, the shortest allowed.
 const token = "0123456789abcdef0123456789abcdef"
 
@@ -120,6 +127,18 @@ func TestDefaults(t *testing.T) {
 	wantNetblocks(t, cfg.DenyNets)
 	wantCountries(t, deniedCountries, cfg.DeniedCountries)
 	wantCountries(t, allowedCountries, cfg.ExclusivelyAllowedCountries)
+
+	hostname, err := os.Hostname()
+	if err != nil || hostname == "" || cfg.InstanceName != hostname {
+		t.Errorf("%s is %q, want the host's name %q (%v)", instanceName,
+			cfg.InstanceName, hostname, err)
+	}
+
+	wantHeaders := strings.Split(defaultLogRequestHeaders, ",")
+	if !slices.Equal(cfg.LogRequestHeaders, wantHeaders) {
+		t.Errorf("%s gave %v, want %v", logRequestHeaders, cfg.LogRequestHeaders,
+			wantHeaders)
+	}
 }
 
 func TestValuesAsSet(t *testing.T) {
@@ -198,6 +217,21 @@ func TestValuesAsSet(t *testing.T) {
 	wantCountries(t, allowedCountries, cfg.ExclusivelyAllowedCountries, "DE")
 }
 
+func TestInstanceNameAndLoggedHeadersAsSet(t *testing.T) {
+	t.Parallel()
+
+	cfg := fromEnvironment(t, environment{
+		instanceName:      "fsn1app1/gitea",
+		logRequestHeaders: " Accept , X-Custom",
+	})
+
+	if cfg.InstanceName != "fsn1app1/gitea" ||
+		!slices.Equal(cfg.LogRequestHeaders, []string{"accept", "x-custom"}) {
+		t.Errorf("%s is %q and %s gives %v", instanceName, cfg.InstanceName,
+			logRequestHeaders, cfg.LogRequestHeaders)
+	}
+}
+
 func TestCodeOnBothCountryListsStopsTheStart(t *testing.T) {
 	t.Parallel()
 
@@ -299,9 +333,7 @@ func TestInvalidValueStopsTheStart(t *testing.T) {
 	t.Parallel()
 
 	for _, tc := range []struct{ name, value string }{
-		{listenAddr, "8080"},
-		{listenAddr, ":http"},
-		{listenAddr, ":65536"},
+		{listenAddr, "8080"}, {listenAddr, ":http"}, {listenAddr, ":65536"},
 		{upstreamURL, "127.0.0.1:8081"},
 		{upstreamURL, "ftp://127.0.0.1:8081"},
 		{upstreamURL, "http://"},
@@ -319,8 +351,7 @@ func TestInvalidValueStopsTheStart(t *testing.T) {
 		{allowNets, "192.0.2.0/24,monitoring"},
 		{rateLimitExemptNets, "2001:db8::/129"},
 		{denyNets, "198.51.100.0/24,"},
-		{clientRequestTimeout, "60"},
-		{clientRequestTimeout, ""},
+		{clientRequestTimeout, "60"}, {clientRequestTimeout, ""},
 		{clientIdleTimeout, "0s"},
 		{clientIdleTimeout, "2 minutes"},
 		{clientResponseTimeout, "1y"},
@@ -361,6 +392,10 @@ func TestInvalidValueStopsTheStart(t *testing.T) {
 		{stateWriteDelay, off}, {stateWriteDelay, "0s"},
 		{stateCounterInterval, off}, {stateCounterInterval, "15"},
 		{metricsTopN, off}, {metricsTopN, "0"}, {metricsTopN, "-1"},
+		{logRequestHeaders, "accept,,origin"}, {logRequestHeaders, "accept;origin"},
+		{logRequestHeaders, "accept language"}, {logRequestHeaders, "x-foo:"},
+		{logRequestHeaders, "host"}, {logRequestHeaders, "accept,Host"},
+		{logRequestHeaders, "transfer-encoding"}, {logRequestHeaders, "TRANSFER-ENCODING"},
 	} {
 		t.Run(tc.name+"="+tc.value, func(t *testing.T) {
 			t.Parallel()
@@ -377,6 +412,27 @@ func TestInvalidValueStopsTheStart(t *testing.T) {
 	}
 }
 
+func TestHostOrTransferEncodingStopsTheStart(t *testing.T) {
+	t.Parallel()
+
+	// Only Host's message points to the field host.
+	for value, want := range map[string]string{
+		"Host": `"Host" is taken out of every request by Go's HTTP server, ` +
+			"so it can never be logged; the request's host is the field host",
+		"transfer-encoding": `"transfer-encoding" is taken out of every ` +
+			"request by Go's HTTP server, so it can never be logged",
+	} {
+		t.Run(value, func(t *testing.T) {
+			t.Parallel()
+
+			_, err := config.FromEnvironment(environment{logRequestHeaders: value}.lookupEnv)
+			if err == nil || err.Error() != logRequestHeaders+": "+want {
+				t.Errorf("error %v, want %s: %s", err, logRequestHeaders, want)
+			}
+		})
+	}
+}
+
 func TestShortTokenStopsTheStartWithoutShowingIt(t *testing.T) {
 	t.Parallel()
 
@@ -428,6 +484,8 @@ func TestLogsEachSettingWithItsValue(t *testing.T) {
 		t.Fatalf("decode %s: %v", out.Bytes(), err)
 	}
 
+	hostname, _ := os.Hostname()
+
 	want := map[string]string{
 		listenAddr:              ":8080",
 		upstreamURL:             "http://127.0.0.1:8081",
@@ -460,6 +518,8 @@ func TestLogsEachSettingWithItsValue(t *testing.T) {
 		stateCounterInterval:    "15m",
 		metricsToken:            "",
 		metricsTopN:             "50",
+		instanceName:            hostname,
+		logRequestHeaders:       defaultLogRequestHeaders,
 	}
 	if !maps.Equal(line.Settings, want) {
 		t.Errorf("logged settings\n%v\nwant\n%v", line.Settings, want)