1 files changed, 77 insertions, 0 deletions

diff --git a/echo/middleware/www_redirect.go b/echo/middleware/www_redirect.go
new file mode 100644
index 0000000..905a5cf
--- /dev/null
+++ b/echo/middleware/www_redirect.go
@@ -0,0 +1,77 @@
+package middleware
+
+import (
+        "fmt"
+        "net"
+        "net/http"
+        "strings"
+
+        "github.com/labstack/echo/v4"
+        "github.com/labstack/echo/v4/middleware"
+)
+
+/*
+WWW Redirect Middleware
+
+This is a duplicate of existing functionality in Echo. This exists
+because we don't want to prefix www to a request that is an IP address
+only, only requests that use hostnames.
+*/
+
+type WWWRedirectConfig struct {
+        Skipper middleware.Skipper
+        Code    int
+}
+
+var DefaultWWWRedirectConfig = WWWRedirectConfig{
+        Skipper: middleware.DefaultSkipper,
+        Code:    http.StatusMovedPermanently,
+}
+
+func WWWRedirect() echo.MiddlewareFunc {
+        return WWWRedirectWithConfig(DefaultWWWRedirectConfig)
+}
+
+func WWWRedirectWithConfig(config WWWRedirectConfig) echo.MiddlewareFunc {
+        if config.Skipper == nil {
+                config.Skipper = DefaultWWWRedirectConfig.Skipper
+        }
+        if config.Code == 0 {
+                config.Code = DefaultWWWRedirectConfig.Code
+        }
+
+        return func(next echo.HandlerFunc) echo.HandlerFunc {
+                return func(c echo.Context) error {
+                        req := c.Request()
+
+                        if config.Skipper(c) || strings.HasPrefix(req.Host, "www.") {
+                                return next(c)
+                        }
+
+                        host, _, err := net.SplitHostPort(req.Host)
+                        if err != nil {
+                                return echo.ErrBadRequest
+                        }
+
+                        // Never prefix an IP with www
+                        //
+                        // We have to parse the hostname for something that looks like an IP
+                        // because the golang http server removes the header from the header
+                        // map and there's no good way to unambiguously determine if this was
+                        // a raw IP request or if a hostname was submitted.
+                        //
+                        // TLS connections could use the req.TLS.ServerName property which
+                        // should have the correct hostname but there's no such thing for HTTP.
+                        // Instead we just try to parse anything that makes it to this point
+                        // because it should be a small one-time cost for a few requests.
+                        if ip := net.ParseIP(host); ip != nil {
+                                return next(c)
+                        }
+
+                        return c.Redirect(
+                                config.Code,
+                                fmt.Sprintf("https://www.%s%s", req.Host, req.RequestURI),
+                        )
+                }
+        }
+}