From d8e5871dca9425811873058150677a158235613d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ingo=20Kl=C3=B6cker?= <dev@ingo-kloecker.de>
Date: Fri, 22 Apr 2022 17:34:41 +0200
Subject: [PATCH] qt: Report better error if decryption failed because of bad
 passphrase

* lang/qt/src/qgpgmedecryptverifyjob.cpp (patch_decryption_result): New.
(decrypt_verify): Call patch_decryption_result.
--

Replace the generic "decryption failed" error with the more specific
"bad passphrase" error if the audit log indicates that a wrong symmetric
password caused the decryption to fail.

GnuPG-bug-id: 5939
---
 lang/qt/src/qgpgmedecryptverifyjob.cpp | 27 +++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/lang/qt/src/qgpgmedecryptverifyjob.cpp b/lang/qt/src/qgpgmedecryptverifyjob.cpp
index 5f9a8abe..bc24d93e 100644
--- a/lang/qt/src/qgpgmedecryptverifyjob.cpp
+++ b/lang/qt/src/qgpgmedecryptverifyjob.cpp
@@ -49,6 +49,7 @@
 #include "qgpgme_debug.h"
 
 #include <QBuffer>
+#include <QRegularExpression>
 
 #include <cassert>
 
@@ -63,12 +64,23 @@ QGpgMEDecryptVerifyJob::QGpgMEDecryptVerifyJob(Context *context)
 
 QGpgMEDecryptVerifyJob::~QGpgMEDecryptVerifyJob() {}
 
+static void patch_decryption_result(DecryptionResult &result, const QString &auditLog)
+{
+    if (result.error().code() == GPG_ERR_DECRYPT_FAILED) {
+        // check for wrong symmetric password
+        if (auditLog.contains(QLatin1String{"gpg: decryption of the symmetrically encrypted session key failed: Checksum error"})
+            || (auditLog.contains(QRegularExpression{QStringLiteral("gpg: encrypted with \\d+ passphrase")})
+                && auditLog.contains(QLatin1String{"gpg: decryption failed: Bad session key"}))) {
+            result.setError(Error::fromCode(GPG_ERR_BAD_PASSPHRASE));
+        }
+    }
+}
+
 static QGpgMEDecryptVerifyJob::result_type decrypt_verify(Context *ctx, QThread *thread,
                                                           const std::weak_ptr<QIODevice> &cipherText_,
                                                           const std::weak_ptr<QIODevice> &plainText_)
 {
-
-    qCDebug(QGPGME_LOG);
+    qCDebug(QGPGME_LOG) << __func__;
 
     const std::shared_ptr<QIODevice> cipherText = cipherText_.lock();
     const std::shared_ptr<QIODevice> plainText = plainText_.lock();
@@ -83,22 +95,23 @@ static QGpgMEDecryptVerifyJob::result_type decrypt_verify(Context *ctx, QThread
         QGpgME::QByteArrayDataProvider out;
         Data outdata(&out);
 
-        const std::pair<DecryptionResult, VerificationResult> res = ctx->decryptAndVerify(indata, outdata);
+        std::pair<DecryptionResult, VerificationResult> res = ctx->decryptAndVerify(indata, outdata);
         Error ae;
         const QString log = _detail::audit_log_as_html(ctx, ae);
-        qCDebug(QGPGME_LOG) << "End no plainText. Error: " << ae;
+        qCDebug(QGPGME_LOG) << __func__ << "- End no plainText. Error:" << ae.asString();
+        patch_decryption_result(res.first, log);
         return std::make_tuple(res.first, res.second, out.data(), log, ae);
     } else {
         QGpgME::QIODeviceDataProvider out(plainText);
         Data outdata(&out);
 
-        const std::pair<DecryptionResult, VerificationResult> res = ctx->decryptAndVerify(indata, outdata);
+        std::pair<DecryptionResult, VerificationResult> res = ctx->decryptAndVerify(indata, outdata);
         Error ae;
         const QString log = _detail::audit_log_as_html(ctx, ae);
-        qCDebug(QGPGME_LOG) << "End plainText. Error: " << ae;
+        qCDebug(QGPGME_LOG) << __func__ << "- End plainText. Error:" << ae.asString();
+        patch_decryption_result(res.first, log);
         return std::make_tuple(res.first, res.second, QByteArray(), log, ae);
     }
-
 }
 
 static QGpgMEDecryptVerifyJob::result_type decrypt_verify_qba(Context *ctx, const QByteArray &cipherText)