fix client IP handling behind proxies

server/internal/shared/bootstrap/http.go

@@ -0,0 +1,23 @@
+package bootstrap
+
+import (
+	"fmt"
+
+	"github.com/gin-gonic/gin"
+
+	"github.com/geo-platform/tenant-api/internal/shared/config"
+)
+
+func NewEngine(server config.ServerConfig) (*gin.Engine, error) {
+	config.NormalizeServerConfig(&server)
+	if server.Mode == "release" {
+		gin.SetMode(gin.ReleaseMode)
+	}
+	engine := gin.New()
+	engine.ForwardedByClientIP = true
+	engine.RemoteIPHeaders = []string{"X-Forwarded-For", "X-Real-IP"}
+	if err := engine.SetTrustedProxies(server.TrustedProxies); err != nil {
+		return nil, fmt.Errorf("set trusted proxies: %w", err)
+	}
+	return engine, nil
+}

server/internal/shared/bootstrap/http_test.go

@@ -0,0 +1,48 @@
+package bootstrap
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/require"
+
+	"github.com/geo-platform/tenant-api/internal/shared/config"
+)
+
+func TestNewEngineUsesForwardedClientIPFromTrustedProxy(t *testing.T) {
+	t.Parallel()
+
+	gin.SetMode(gin.TestMode)
+
+	engine, err := NewEngine(config.ServerConfig{
+		TrustedProxies: []string{"10.42.0.0/16"},
+	})
+	require.NoError(t, err)
+
+	engine.GET("/ip", func(c *gin.Context) {
+		c.String(http.StatusOK, c.ClientIP())
+	})
+
+	req := httptest.NewRequest(http.MethodGet, "/ip", nil)
+	req.RemoteAddr = "10.42.0.128:51234"
+	req.Header.Set("X-Forwarded-For", "106.14.89.27")
+	resp := httptest.NewRecorder()
+
+	engine.ServeHTTP(resp, req)
+
+	require.Equal(t, http.StatusOK, resp.Code)
+	require.Equal(t, "106.14.89.27", resp.Body.String())
+}
+
+func TestNewEngineRejectsInvalidTrustedProxy(t *testing.T) {
+	t.Parallel()
+
+	gin.SetMode(gin.TestMode)
+
+	_, err := NewEngine(config.ServerConfig{
+		TrustedProxies: []string{"not-a-cidr"},
+	})
+	require.Error(t, err)
+}