revertws (#17216)

* Revert "MM-34000: Use non-epoll mode for TLS connections (#17172)"

This reverts commit 2743089b54.

* Revert "MM-33233: Fix double close of webconn pump (#17026)"

This reverts commit 0f98620b65.

* Revert "MM-33836: Detect and upgrade incorrect HTTP version for websocket handshakes (#17142)"

This reverts commit 4c5ea07aff.

* revert i18n

* Revert "MM-21012: Revamp websocket implementation (#16620)"

This reverts commit a246104d04.

* fix go.mod

* Trigger CI

utils/api.go

@@ -13,7 +13,6 @@ import (
 	"net/url"
 	"path"
 	"strings"
-	"unicode/utf8"
 
 	"github.com/mattermost/mattermost-server/v5/model"
 	"github.com/mattermost/mattermost-server/v5/shared/i18n"
@@ -29,58 +28,19 @@ func CheckOrigin(r *http.Request, allowedOrigins string) bool {
 		return true
 	}
 	for _, allowed := range strings.Split(allowedOrigins, " ") {
-		if equalASCIIFold(allowed, origin) {
+		if allowed == origin {
 			return true
 		}
 	}
 	return false
 }
 
-// equalASCIIFold returns true if s is equal to t with ASCII case folding as
-// defined in RFC 4790.
-// Copied from gorilla/websocket/util.go
-func equalASCIIFold(s, t string) bool {
-	for s != "" && t != "" {
-		sr, size := utf8.DecodeRuneInString(s)
-		s = s[size:]
-		tr, size := utf8.DecodeRuneInString(t)
-		t = t[size:]
-		if sr == tr {
-			continue
-		}
-		if 'A' <= sr && sr <= 'Z' {
-			sr = sr + 'a' - 'A'
-		}
-		if 'A' <= tr && tr <= 'Z' {
-			tr = tr + 'a' - 'A'
-		}
-		if sr != tr {
-			return false
-		}
-	}
-	return s == t
-}
-
 func OriginChecker(allowedOrigins string) func(*http.Request) bool {
 	return func(r *http.Request) bool {
 		return CheckOrigin(r, allowedOrigins)
 	}
 }
 
-func SameOriginChecker() func(*http.Request) bool {
-	return func(r *http.Request) bool {
-		origURL, err := url.Parse(r.Header.Get("Origin"))
-		if err != nil {
-			return false
-		}
-		u := url.URL{
-			Host:   r.Host,
-			Scheme: origURL.Scheme,
-		}
-		return CheckOrigin(r, u.String())
-	}
-}
-
 func RenderWebAppError(config *model.Config, w http.ResponseWriter, r *http.Request, err *model.AppError, s crypto.Signer) {
 	RenderWebError(config, w, r, err.StatusCode, url.Values{
 		"message": []string{err.Message},