From c1e2ec16db05173afed1f625b9dfaedaa8a1b75a Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Fri, 24 Feb 2023 08:16:20 +0100
Subject: [PATCH] QMessageAuthenticationCode: statically assert HMAC works for
 all algorithms
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

... by checking that for each algorithm, that the algorithm's result
size is not larger than the algorithm's block size.

Pick-to: 6.5
Change-Id: I4daf7900e72766d180954b15edb06687a57f939f
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/tools/qcryptographichash.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/corelib/tools/qcryptographichash.cpp b/src/corelib/tools/qcryptographichash.cpp
index 78ab9836a1..09b53d4941 100644
--- a/src/corelib/tools/qcryptographichash.cpp
+++ b/src/corelib/tools/qcryptographichash.cpp
@@ -1150,7 +1150,14 @@ void QMessageAuthenticationCodePrivate::setKey(const QByteArray &newKey)
     if (newKey.size() > blockSize) {
         messageHash.addData(newKey);
         messageHash.finalizeUnchecked();
-        static_assert(maxHashLength() <= maxHashBlockSize());
+        static_assert([] {
+                using A = QCryptographicHash::Algorithm;
+                for (int i = 0; i < A::NumAlgorithms; ++i) {
+                    if (hashLengthInternal(A(i)) > qt_hash_block_size(A(i)))
+                        return false;
+                }
+                return true;
+            }(), "this code assumes that a hash's result always fits into that hash's block size");
         key = messageHash.result;
         messageHash.reset();
     } else {