From 8a83dcb462cfd3b42cc92c3b843b7ca2f4b76634 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?M=C3=A5rten=20Nordheim?= <marten.nordheim@qt.io>
Date: Wed, 10 May 2023 16:43:41 +0200
Subject: [PATCH 095/147] Schannel: Reject certificate not signed by a
 configured CA certificate

Not entirely clear why, but when building the certificate chain for a
peer the system certificate store is searched for root certificates.
General expectation is that after calling
`sslConfiguration.setCaCertificates()` the system certificates will
not be taken into consideration.

To work around this behavior, we do a manual check that the root of the
chain is part of the configured CA certificates.

Pick-to: 6.5 6.2 5.15
Change-Id: I03666a4d9b0eac39ae97e150b4743120611a11b3
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit ada2c573c1a25f8d96577734968fe317ddfa292a)
---
 src/network/ssl/qsslsocket_schannel.cpp | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/network/ssl/qsslsocket_schannel.cpp b/src/network/ssl/qsslsocket_schannel.cpp
index c956ce3c2b..d1b23af29b 100644
--- a/src/network/ssl/qsslsocket_schannel.cpp
+++ b/src/network/ssl/qsslsocket_schannel.cpp
@@ -1880,6 +1880,28 @@ bool QSslSocketBackendPrivate::verifyCertContext(CERT_CONTEXT *certContext)
     if (configuration.peerVerifyDepth > 0 && DWORD(configuration.peerVerifyDepth) < verifyDepth)
         verifyDepth = DWORD(configuration.peerVerifyDepth);
 
+    const auto &caCertificates = q->sslConfiguration().caCertificates();
+
+    if (!rootCertOnDemandLoadingAllowed()
+            && !(chain->TrustStatus.dwErrorStatus & CERT_TRUST_IS_PARTIAL_CHAIN)
+            && (q->peerVerifyMode() == QSslSocket::VerifyPeer
+                    || (isClient && q->peerVerifyMode() == QSslSocket::AutoVerifyPeer))) {
+        // When verifying a peer Windows "helpfully" builds a chain that
+        // may include roots from the system store. But we don't want that if
+        // the user has set their own CA certificates.
+        // Since Windows claims this is not a partial chain the root is included
+        // and we have to check that it is one of our configured CAs.
+        CERT_CHAIN_ELEMENT *element = chain->rgpElement[chain->cElement - 1];
+        QSslCertificate certificate = getCertificateFromChainElement(element);
+        if (!caCertificates.contains(certificate)) {
+            auto error = QSslError(QSslError::CertificateUntrusted, certificate);
+            sslErrors += error;
+            emit q->peerVerifyError(error);
+            if (q->state() != QAbstractSocket::ConnectedState)
+                return false;
+        }
+    }
+
     for (DWORD i = 0; i < verifyDepth; i++) {
         CERT_CHAIN_ELEMENT *element = chain->rgpElement[i];
         QSslCertificate certificate = getCertificateFromChainElement(element);
-- 
2.40.1