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Improve resilience against memory attacks

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To reduce residual fragments of secret data in memory after
deallocation, this patch replaces the global delete operator with a
version that zeros out previously allocated memory. It makes use of
the new C++14 sized deallocation, but provides an unsized fallback
with platform-specific size deductions.

This change is only a minor mitigation and cannot protect against
buffer reallocations by the operating system or non-C++ libraries.
Thus, we still cannot guarantee all memory to be wiped after free.

As a further improvement, this patch uses libgcrypt and libsodium
to write long-lived master key component hashes into a secure
memory area and wipe it afterwards.

The patch also fixes compiler flags not being set properly on macOS.
This commit is contained in:
Janek Bevendorff
2019-02-21 22:28:45 +01:00
committed by Jonathan White
parent c7898fdeee
commit 13eb1c0bbd
14 changed files with 207 additions and 28 deletions
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24
src/keys/PasswordKey.cpp
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@@ -1,5 +1,5 @@
/*
* Copyright (C) 2010 Felix Geyer <debfx@fobos.de>
* Copyright (C) 2019 KeePassXC Team <team@keepassxc.org>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -16,35 +16,51 @@
*/
#include "PasswordKey.h"
#include "core/Tools.h"
#include "crypto/CryptoHash.h"
#include <gcrypt.h>
#include <algorithm>
#include <cstring>
QUuid PasswordKey::UUID("77e90411-303a-43f2-b773-853b05635ead");
constexpr int PasswordKey::SHA256_SIZE;
PasswordKey::PasswordKey()
: Key(UUID)
, m_key(static_cast<char*>(gcry_malloc_secure(SHA256_SIZE)))
{
}
PasswordKey::PasswordKey(const QString& password)
: Key(UUID)
, m_key(static_cast<char*>(gcry_malloc_secure(SHA256_SIZE)))
{
setPassword(password);
}
PasswordKey::~PasswordKey()
{
if (m_key) {
gcry_free(m_key);
m_key = nullptr;
}
}
QSharedPointer<PasswordKey> PasswordKey::fromRawKey(const QByteArray& rawKey)
{
auto result = QSharedPointer<PasswordKey>::create();
result->m_key = rawKey;
std::memcpy(result->m_key, rawKey.data(), std::min(SHA256_SIZE, rawKey.size()));
return result;
}
QByteArray PasswordKey::rawKey() const
{
return m_key;
return QByteArray::fromRawData(m_key, SHA256_SIZE);
}
void PasswordKey::setPassword(const QString& password)
{
m_key = CryptoHash::hash(password.toUtf8(), CryptoHash::Sha256);
std::memcpy(m_key, CryptoHash::hash(password.toUtf8(), CryptoHash::Sha256).data(), SHA256_SIZE);
}