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/**
* Copyright (C) 2021-2024 Saturneric <eric@bktus.com>
*
* This file is part of GpgFrontend.
*
* GpgFrontend is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GpgFrontend is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GpgFrontend. If not, see <https://www.gnu.org/licenses/>.
*
* The initial version of the source code is inherited from
* the gpg4usb project, which is under GPL-3.0-or-later.
*
* All the source code of GpgFrontend was modified and released by
* Saturneric <eric@bktus.com> starting on May 12, 2021.
*
* SPDX-License-Identifier: GPL-3.0-or-later
*
*/
// Whether a secret can actually be erased.
//
// Every wipe in this module used to be `password.fill(QChar('\0'))` on a
// QString. QString is implicitly shared and fill() detaches before writing, so
// whenever anything else held a reference -- a queued signal argument, a
// worker's parameter, an authenticator's member -- the call zeroed a FRESH
// buffer and dropped the reference to the original, which was then freed with
// the plaintext still in it. It read as protection and performed none.
//
// The first test below demonstrates that on QString directly, so the reason
// this class exists is recorded rather than asserted. The rest hold
// EMailSecret to the behaviour that replaces it.
#include <GFSDKBuffer.h>
#include <GFSDKContext.h>
#include <gtest/gtest.h>
#include <QString>
#include <cstring>
#include "EMailSecret.h"
using namespace Qt::StringLiterals;
/// Supplied by the harness (EMailSdkStubs.cpp).
auto GFModuleSdkContext() -> GFSDKContext*;
namespace {
TEST(EMailSecretTest, AQStringWipeDoesNotReachASharedBuffer) {
QString original = u"correct-horse-battery"_s;
// Force a heap buffer of our own rather than a literal's shared data.
original.detach();
const QString shared = original; // refcount 2, same buffer
const auto* buffer = shared.constData();
original.fill(QChar('\0'));
// The copy still reads the secret: original detached and zeroed elsewhere.
EXPECT_EQ(shared, u"correct-horse-battery"_s);
EXPECT_EQ(buffer[0], QChar('c'))
<< "if this ever fails, QString has changed and the note above is stale";
}
TEST(EMailSecretTest, WipingClearsTheOnlyCopy) {
auto secret = EMailSecret::CopyFrom(u"hunter2"_s);
ASSERT_FALSE(secret->IsEmpty());
EXPECT_EQ(secret->Size(), 7U);
secret->Wipe();
EXPECT_TRUE(secret->IsEmpty());
EXPECT_EQ(secret->Size(), 0U);
EXPECT_TRUE(secret->StdStringCopy().empty());
}
TEST(EMailSecretTest, WipingTwiceIsHarmless) {
auto secret = EMailSecret::CopyFrom(u"hunter2"_s);
secret->Wipe();
secret->Wipe();
EXPECT_TRUE(secret->IsEmpty());
}
TEST(EMailSecretTest, AnEmptySecretIsUsable) {
EMailSecret secret;
EXPECT_TRUE(secret.IsEmpty());
EXPECT_TRUE(secret.StdStringCopy().empty());
secret.Wipe();
EXPECT_TRUE(secret.IsEmpty());
}
TEST(EMailSecretTest, MovingTransfersAndLeavesNothingBehind) {
EMailSecret from;
{
auto source = EMailSecret::CopyFrom(u"s3cret"_s);
from = std::move(*source);
}
EXPECT_EQ(from.StdStringCopy(), "s3cret");
EMailSecret to = std::move(from);
EXPECT_EQ(to.StdStringCopy(), "s3cret");
EXPECT_TRUE(from.IsEmpty()) << "the moved-from secret still holds bytes";
}
TEST(EMailSecretTest, MoveAssignmentWipesWhatItReplaces) {
auto first = EMailSecret::CopyFrom(u"first-secret"_s);
auto second = EMailSecret::CopyFrom(u"second"_s);
*first = std::move(*second);
EXPECT_EQ(first->StdStringCopy(), "second");
EXPECT_TRUE(second->IsEmpty());
}
TEST(EMailSecretTest, TheLastHolderReleasingErasesTheBytes) {
// The property the queued-connection hand-off depends on: the GUI thread
// drops its reference immediately after posting, and the worker's copy is
// the same bytes, not a duplicate.
EMailSecretPtr shared;
{
auto secret = EMailSecret::CopyFrom(u"shared-secret"_s);
shared = secret;
EXPECT_EQ(shared.use_count(), 2);
secret.reset();
}
ASSERT_EQ(shared.use_count(), 1);
EXPECT_EQ(shared->StdStringCopy(), "shared-secret")
<< "releasing one holder erased bytes the other still needed";
}
TEST(EMailSecretTest, AdoptingABufferTakesTheBytesAndReleasesIt) {
// The SDK hands a secret back as a buffer now, not a secure char*. A buffer
// wipes itself on release, so the bytes exist in one place afterwards and
// that place is the vector this class can erase.
const char* text = "from-the-sdk";
const auto length = std::strlen(text);
auto* ctx = GFModuleSdkContext();
auto* raw = GFBufferNewFromBytes(ctx, text, length);
ASSERT_NE(raw, nullptr);
auto secret = EMailSecret::AdoptBuffer(ctx, raw);
EXPECT_EQ(secret->StdStringCopy(), "from-the-sdk");
EXPECT_EQ(secret->Size(), length);
}
TEST(EMailSecretTest, AdoptingNullIsEmptyRatherThanACrash) {
auto secret = EMailSecret::AdoptBuffer(GFModuleSdkContext(), nullptr);
ASSERT_NE(secret, nullptr);
EXPECT_TRUE(secret->IsEmpty());
}
TEST(EMailSecretTest, ASecretIsNotCopyable) {
// Compile-time, and the point of the class: an accidental copy is another
// plaintext buffer nobody remembers to erase.
static_assert(!std::is_copy_constructible_v<EMailSecret>);
static_assert(!std::is_copy_assignable_v<EMailSecret>);
static_assert(std::is_move_constructible_v<EMailSecret>);
static_assert(std::is_move_assignable_v<EMailSecret>);
SUCCEED();
}
// --- reaching the SDK without a QString on the way --------------------------
TEST(EMailSecretTest, ASecureCStringCarriesTheSecretVerbatim) {
// The route a stored password takes now. It used to go out as
// QSecStrDup(QString), which builds an unwiped QByteArray temporary on the
// way -- one more copy of the password than there needs to be, and one
// nothing can erase.
auto secret = EMailSecret::CopyFrom(u"correct-horse"_s);
auto* buffer = secret->ToSecureCString();
ASSERT_NE(buffer, nullptr);
EXPECT_EQ(std::strlen(buffer), secret->Size());
EXPECT_STREQ(buffer, "correct-horse");
// NUL-terminated one past the secret, so a C API can read it as a string.
EXPECT_EQ(buffer[secret->Size()], '\0');
GFMemFree(GFModuleSdkContext(), GF_ARENA_SECURE, buffer);
}
TEST(EMailSecretTest, AnEmptySecretStillProducesAUsableString) {
auto secret = EMailSecret::CopyFrom(QString());
auto* buffer = secret->ToSecureCString();
ASSERT_NE(buffer, nullptr);
EXPECT_STREQ(buffer, "");
GFMemFree(GFModuleSdkContext(), GF_ARENA_SECURE, buffer);
}
TEST(EMailSecretTest, NonAsciiSurvivesTheRoundTrip) {
// A password is whatever the user typed, and UTF-8 is not optional.
const QString typed = QString::fromUtf8("pa\xC3\x9Fwort-\xE9\x94\xAE");
auto secret = EMailSecret::CopyFrom(typed);
auto* buffer = secret->ToSecureCString();
ASSERT_NE(buffer, nullptr);
EXPECT_EQ(QString::fromUtf8(buffer), typed);
GFMemFree(GFModuleSdkContext(), GF_ARENA_SECURE, buffer);
}
} // namespace
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