Update mattermost library

vendor/github.com/gorilla/websocket/util.go

@@ -6,7 +6,7 @@ package websocket
 
 import (
 	"crypto/rand"
-	"crypto/sha1"
+	"crypto/sha1" //#nosec G505 -- (CWE-327) https://datatracker.ietf.org/doc/html/rfc6455#page-54
 	"encoding/base64"
 	"io"
 	"net/http"
@@ -17,7 +17,7 @@ import (
 var keyGUID = []byte("258EAFA5-E914-47DA-95CA-C5AB0DC85B11")
 
 func computeAcceptKey(challengeKey string) string {
-	h := sha1.New()
+	h := sha1.New() //#nosec G401 -- (CWE-326) https://datatracker.ietf.org/doc/html/rfc6455#page-54
 	h.Write([]byte(challengeKey))
 	h.Write(keyGUID)
 	return base64.StdEncoding.EncodeToString(h.Sum(nil))
@@ -281,3 +281,18 @@ headers:
 	}
 	return result
 }
+
+// isValidChallengeKey checks if the argument meets RFC6455 specification.
+func isValidChallengeKey(s string) bool {
+	// From RFC6455:
+	//
+	// A |Sec-WebSocket-Key| header field with a base64-encoded (see
+	// Section 4 of [RFC4648]) value that, when decoded, is 16 bytes in
+	// length.
+
+	if s == "" {
+		return false
+	}
+	decoded, err := base64.StdEncoding.DecodeString(s)
+	return err == nil && len(decoded) == 16
+}