Add file encryption functions and Encryption/DecryptionDevice

The devices allow it to encrypt or decrypt data on the fly when reading
or writing data.

2 files changed, 353 insertions, 0 deletions

diff --git a/src/client/QXmppFileEncryption.cpp b/src/client/QXmppFileEncryption.cpp
new file mode 100644
index 00000000..99ccd474
--- /dev/null
+++ b/src/client/QXmppFileEncryption.cpp
@@ -0,0 +1,279 @@
+// SPDX-FileCopyrightText: 2022 Linus Jahn <lnj@kaidan.im>
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
+#include "QXmppFileEncryption.h"
+
+#include <QByteArray>
+#include <QtCrypto>
+
+using namespace QCA;
+
+constexpr std::size_t AES128_BLOCK_SIZE = 128 / 8;
+constexpr std::size_t AES256_BLOCK_SIZE = 256 / 8;
+constexpr int GCM_IV_SIZE = 12;
+
+namespace QXmpp::Private::Encryption {
+
+static QString cipherName(QXmpp::Cipher cipher)
+{
+    switch (cipher) {
+    case Aes128GcmNoPad:
+        return QStringLiteral("aes128");
+    case Aes256GcmNoPad:
+    case Aes256CbcPkcs7:
+        return QStringLiteral("aes256");
+    }
+    Q_UNREACHABLE();
+}
+
+static std::size_t blockSize(QXmpp::Cipher cipher)
+{
+    switch (cipher) {
+    case Aes128GcmNoPad:
+        return AES128_BLOCK_SIZE;
+    case Aes256GcmNoPad:
+    case Aes256CbcPkcs7:
+        return AES256_BLOCK_SIZE;
+    }
+    Q_UNREACHABLE();
+}
+
+static QCA::Cipher::Mode cipherMode(QXmpp::Cipher cipher)
+{
+    switch (cipher) {
+    case Aes128GcmNoPad:
+    case Aes256GcmNoPad:
+        return QCA::Cipher::GCM;
+    case Aes256CbcPkcs7:
+        return QCA::Cipher::CBC;
+    }
+    Q_UNREACHABLE();
+}
+
+static QCA::Cipher::Padding padding(QXmpp::Cipher cipher)
+{
+    switch (cipher) {
+    case Aes128GcmNoPad:
+    case Aes256GcmNoPad:
+        return QCA::Cipher::NoPadding;
+    case Aes256CbcPkcs7:
+        return QCA::Cipher::PKCS7;
+    }
+    Q_UNREACHABLE();
+}
+
+QCA::Direction toQcaDirection(Direction direction)
+{
+    switch (direction) {
+    case Encode:
+        return QCA::Encode;
+    case Decode:
+        return QCA::Decode;
+    }
+    Q_UNREACHABLE();
+}
+
+static std::size_t roundUpToBlockSize(qint64 size, std::size_t blockSize)
+{
+    Q_ASSERT(size >= 0);
+    return (size / blockSize + 1) * blockSize;
+}
+
+QByteArray process(const QByteArray &data, QXmpp::Cipher cipherConfig, Direction direction, const QByteArray &key, const QByteArray &iv)
+{
+    return QCA::Cipher(cipherName(cipherConfig),
+                       cipherMode(cipherConfig),
+                       padding(cipherConfig),
+                       toQcaDirection(direction),
+                       SymmetricKey(key),
+                       InitializationVector(iv))
+        .process(MemoryRegion(data))
+        .toByteArray();
+}
+
+QByteArray generateKey(QXmpp::Cipher cipher)
+{
+    return Random::randomArray(int(blockSize(cipher))).toByteArray();
+}
+
+QByteArray generateInitializationVector(QXmpp::Cipher config)
+{
+    switch (config) {
+    case Aes128GcmNoPad:
+    case Aes256GcmNoPad:
+        return Random::randomArray(GCM_IV_SIZE).toByteArray();
+    case Aes256CbcPkcs7:
+        return Random::randomArray(int(blockSize(config))).toByteArray();
+    }
+    Q_UNREACHABLE();
+}
+
+EncryptionDevice::EncryptionDevice(std::unique_ptr<QIODevice> input,
+                                   Cipher config,
+                                   const QByteArray &key,
+                                   const QByteArray &iv)
+    : m_cipherConfig(config),
+      m_input(std::move(input)),
+      m_cipher(std::make_unique<QCA::Cipher>(
+          cipherName(config),
+          cipherMode(config),
+          padding(config),
+          QCA::Encode,
+          SymmetricKey(key),
+          InitializationVector(iv)))
+{
+    // output must not be sequential
+    Q_ASSERT(!m_input->isSequential());
+
+    Q_ASSERT(m_outputBuffer.empty());
+
+    setOpenMode(m_input->openMode() & QIODevice::ReadOnly);
+}
+
+EncryptionDevice::~EncryptionDevice() = default;
+
+bool EncryptionDevice::open(OpenMode mode)
+{
+    return m_input->open(mode);
+}
+
+void EncryptionDevice::close()
+{
+    m_input->close();
+}
+
+bool EncryptionDevice::isSequential() const
+{
+    return false;
+}
+
+qint64 EncryptionDevice::size() const
+{
+    switch (m_cipherConfig) {
+    case Aes128GcmNoPad:
+    case Aes256GcmNoPad:
+        return m_input->size();
+    case Aes256CbcPkcs7: {
+        // padding is done with 128 bits blocks
+        return roundUpToBlockSize(m_input->size(), 128 / 8);
+    }
+    }
+    Q_UNREACHABLE();
+}
+
+qint64 EncryptionDevice::readData(char *data, qint64 len)
+{
+    auto requestedLen = len;
+    qint64 read = 0;
+
+    {
+        // try to read from output buffer
+        qint64 outputBufferRead = std::min(qint64(m_outputBuffer.size()), len);
+        std::copy_n(m_outputBuffer.cbegin(), outputBufferRead, data);
+        m_outputBuffer.erase(m_outputBuffer.begin(), m_outputBuffer.begin() + outputBufferRead);
+        read += outputBufferRead;
+        len -= outputBufferRead;
+    }
+
+    if (len > 0) {
+        // read from input and encrypt new data
+
+        // output buffer is empty here
+        Q_ASSERT(m_outputBuffer.empty());
+
+        // read unencrypted data (may read one block more than needed)
+        auto inputBufferSize = roundUpToBlockSize(len, blockSize(m_cipherConfig));
+        Q_ASSERT(inputBufferSize > 0);
+        QByteArray inputBuffer;
+        inputBuffer.resize(inputBufferSize);
+        inputBuffer.resize(m_input->read(inputBuffer.data(), inputBufferSize));
+
+        // process input buffer
+        auto processed = [&]() {
+            if (inputBuffer.isEmpty()) {
+                m_finalized = true;
+                return m_cipher->final();
+            }
+            // encrypt data
+            return m_cipher->process(MemoryRegion(inputBuffer));
+        }();
+
+        // split up into part for user and put rest into output buffer
+        auto processedReadBytes = std::min(qint64(processed.size()), len);
+        std::copy_n(processed.constData(), processedReadBytes, data + read);
+        read += processedReadBytes;
+        len -= processedReadBytes;
+
+        Q_ASSERT(processed.size() >= processedReadBytes);
+        auto restBytes = size_t(processed.size() - processedReadBytes);
+        m_outputBuffer.resize(restBytes);
+        std::copy_n(processed.constData() + processedReadBytes, restBytes, m_outputBuffer.data());
+    }
+
+    Q_ASSERT((len + read) == requestedLen);
+    return read;
+}
+
+qint64 EncryptionDevice::writeData(const char *, qint64)
+{
+    return 0;
+}
+
+DecryptionDevice::DecryptionDevice(std::unique_ptr<QIODevice> input,
+                                   Cipher config,
+                                   const QByteArray &key,
+                                   const QByteArray &iv)
+    : m_cipherConfig(config),
+      m_output(std::move(input)),
+      m_cipher(std::make_unique<QCA::Cipher>(
+          cipherName(config),
+          cipherMode(config),
+          padding(config),
+          QCA::Decode,
+          SymmetricKey(key),
+          InitializationVector(iv)))
+{
+    // output must not be sequential
+    Q_ASSERT(!m_output->isSequential());
+
+    Q_ASSERT(m_outputBuffer.empty());
+
+    setOpenMode(m_output->openMode() & QIODevice::WriteOnly);
+}
+
+DecryptionDevice::~DecryptionDevice() = default;
+
+bool DecryptionDevice::open(OpenMode mode)
+{
+    return m_output->open(mode);
+}
+
+void DecryptionDevice::close()
+{
+    m_output->close();
+}
+
+bool DecryptionDevice::isSequential() const
+{
+    return true;
+}
+
+qint64 DecryptionDevice::size() const
+{
+    return 0;
+}
+
+qint64 DecryptionDevice::readData(char *, qint64)
+{
+    return 0;
+}
+
+qint64 DecryptionDevice::writeData(const char *data, qint64 len)
+{
+    auto decrypted = m_cipher->process(QByteArray(data, len));
+    m_output->write(decrypted.constData(), decrypted.size());
+    return len;
+}
+
+}  // namespace QXmpp::Private::Encryption
diff --git a/src/client/QXmppFileEncryption.h b/src/client/QXmppFileEncryption.h
new file mode 100644
index 00000000..b1108b22
--- /dev/null
+++ b/src/client/QXmppFileEncryption.h
@@ -0,0 +1,74 @@
+// SPDX-FileCopyrightText: 2022 Linus Jahn <lnj@kaidan.im>
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
+#ifndef QXMPPFILEENCRYPTION_H
+#define QXMPPFILEENCRYPTION_H
+
+#include "QXmppGlobal.h"
+
+#include <memory>
+
+#include <QIODevice>
+
+namespace QCA {
+class Cipher;
+class Initializer;
+}  // namespace QCA
+
+namespace QXmpp::Private::Encryption {
+
+enum Direction {
+    Encode,
+    Decode,
+};
+
+QByteArray process(const QByteArray &data, Cipher cipherConfig, Direction direction, const QByteArray &key, const QByteArray &iv);
+QByteArray generateKey(Cipher cipher);
+QByteArray generateInitializationVector(Cipher);
+
+// export for tests
+class QXMPP_EXPORT EncryptionDevice : public QIODevice
+{
+public:
+    EncryptionDevice(std::unique_ptr<QIODevice> input, Cipher config, const QByteArray &key, const QByteArray &iv);
+    ~EncryptionDevice() override;
+
+    bool open(QIODevice::OpenMode mode) override;
+    void close() override;
+    bool isSequential() const override;
+    qint64 size() const override;
+    qint64 readData(char *data, qint64 maxlen) override;
+    qint64 writeData(const char *data, qint64 len) override;
+
+private:
+    Cipher m_cipherConfig;
+    bool m_finalized = false;
+    std::vector<char> m_outputBuffer;
+    std::unique_ptr<QIODevice> m_input;
+    std::unique_ptr<QCA::Cipher> m_cipher;
+};
+
+class DecryptionDevice : public QIODevice
+{
+public:
+    DecryptionDevice(std::unique_ptr<QIODevice> output, Cipher config, const QByteArray &key, const QByteArray &iv);
+    ~DecryptionDevice() override;
+
+    bool open(QIODevice::OpenMode mode) override;
+    void close() override;
+    bool isSequential() const override;
+    qint64 size() const override;
+    qint64 readData(char *data, qint64 maxlen) override;
+    qint64 writeData(const char *data, qint64 len) override;
+
+private:
+    Cipher m_cipherConfig;
+    std::vector<char> m_outputBuffer;
+    std::unique_ptr<QIODevice> m_output;
+    std::unique_ptr<QCA::Cipher> m_cipher;
+};
+
+}  // namespace QXmpp::Private::Encryption
+
+#endif  // QXMPPFILEENCRYPTION_H