Add QCryptographicHash::supportsAlgorithm() to check supported algorithm

Adds QCH::supportsAlgorithm() method which returns whether the selected
algorithm is supported and we guarantee to get a result when generating
hashes. OpenSSL will be responsible for providing us this information.
Returns TRUE if OpenSSL is not used as a provider.

[ChangeLog][QtCore][QCryptographicHash] Add supportsAlgorithm() method
that can be used to query OpenSSL and check whether the selected
algorithm is supported.

Change-Id: I0d94e02b8c70beb79520150fab6c32bdd1da3fca
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
(cherry picked from commit 0657b0734ef78cbaeb5f9d800df79647790d3163)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/tools/qcryptographichash.cpp

@@ -217,6 +217,7 @@ public:
     void addData(QByteArrayView bytes) noexcept;
     void finalize() noexcept;
     QByteArrayView resultView() const noexcept { return result.toByteArrayView(); }
+    static bool supportsAlgorithm(QCryptographicHash::Algorithm method);
 
     const QCryptographicHash::Algorithm method;
 
@@ -865,6 +866,40 @@ int QCryptographicHash::hashLength(QCryptographicHash::Algorithm method)
     return hashLengthInternal(method);
 }
 
+/*!
+  Returns whether the selected algorithm \a method is supported and if
+  result() will return a value when the \a method is used.
+
+  \note OpenSSL will be responsible for providing this information when
+  used as a provider, otherwise \c true will be returned as the non-OpenSSL
+  implementation doesn't have any restrictions.
+  We return \c false if we fail to query OpenSSL.
+
+  \since 6.5
+*/
+
+
+bool QCryptographicHash::supportsAlgorithm(QCryptographicHash::Algorithm method)
+{
+    return QCryptographicHashPrivate::supportsAlgorithm(method);
+}
+
+bool QCryptographicHashPrivate::supportsAlgorithm(QCryptographicHash::Algorithm method)
+{
+#ifdef USING_OPENSSL30
+    OSSL_PROVIDER_load(nullptr, "legacy");
+    OSSL_PROVIDER_load(nullptr, "default");
+
+    const char *restriction = "-fips";
+    EVP_MD_ptr algorithm = EVP_MD_ptr(EVP_MD_fetch(nullptr, methodToName(method), restriction));
+
+    return algorithm != nullptr;
+#else
+    Q_UNUSED(method);
+    return true;
+#endif
+}
+
 QT_END_NAMESPACE
 
 #ifndef QT_NO_QOBJECT

src/corelib/tools/qcryptographichash.h

@@ -91,6 +91,7 @@ public:
 #endif
     static QByteArray hash(QByteArrayView data, Algorithm method);
     static int hashLength(Algorithm method);
+    static bool supportsAlgorithm(Algorithm method);
 private:
     Q_DISABLE_COPY(QCryptographicHash)
     QCryptographicHashPrivate *d;