LibCrypto: Add Chacha20Poly1305

Userland/Libraries/LibCrypto/AEAD/ChaCha20Poly1305.cpp

@@ -0,0 +1,182 @@
+/*
+ * Copyright (c) 2023, stelar7 <dudedbz@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/ByteReader.h>
+#include <AK/Endian.h>
+#include <LibCrypto/AEAD/ChaCha20Poly1305.h>
+#include <LibCrypto/Authentication/Poly1305.h>
+#include <LibCrypto/Cipher/ChaCha20.h>
+
+namespace Crypto::AEAD {
+
+// https://datatracker.ietf.org/doc/html/rfc8439#section-2.6
+ErrorOr<ByteBuffer> ChaCha20Poly1305::poly1305_key()
+{
+    Crypto::Cipher::ChaCha20 cipher(m_key, m_nonce, 0);
+    cipher.generate_block();
+    auto state = cipher.block();
+    return TRY(ByteBuffer::copy(state.slice(0, 32)));
+}
+
+// https://datatracker.ietf.org/doc/html/rfc8439#section-2.8
+ErrorOr<ByteBuffer> ChaCha20Poly1305::encrypt(ReadonlyBytes aad, ReadonlyBytes input_plaintext)
+{
+    // First, a Poly1305 one-time key is generated from the 256-bit key
+    // and nonce using the procedure described in Section 2.6.
+    auto otk = TRY(poly1305_key());
+
+    // Next, the ChaCha20 encryption function is called to encrypt the
+    // plaintext, using the same key and nonce, and with the initial
+    // counter set to 1.
+    auto ciphertext_buffer = TRY(ByteBuffer::create_zeroed(input_plaintext.size()));
+    auto ciphertext = ciphertext_buffer.bytes();
+    auto chacha = Crypto::Cipher::ChaCha20(m_key, m_nonce, 1);
+    chacha.encrypt(input_plaintext, ciphertext);
+
+    // Finally, the Poly1305 function is called with the Poly1305 key
+    // calculated above, and a message constructed as a concatenation of
+    // the following:
+    auto mac_data = TRY(ByteBuffer::create_zeroed(0));
+    auto buffer_size = aad.size() + pad_to_16(aad) + ciphertext_buffer.size() + pad_to_16(ciphertext_buffer) + sizeof(u64) + sizeof(u64);
+    mac_data.ensure_capacity(buffer_size);
+
+    // The AAD
+    mac_data.append(aad);
+
+    // padding1 -- the padding is up to 15 zero bytes, and it brings
+    // the total length so far to an integral multiple of 16.  If the
+    // length of the AAD was already an integral multiple of 16 bytes,
+    // this field is zero-length.
+    for (size_t i = 0; i < pad_to_16(aad); ++i)
+        mac_data.append(0);
+
+    // The ciphertext
+    mac_data.append(ciphertext);
+
+    // padding2 -- the padding is up to 15 zero bytes, and it brings
+    // the total length so far to an integral multiple of 16.  If the
+    // length of the ciphertext was already an integral multiple of 16
+    // bytes, this field is zero-length.
+    for (size_t i = 0; i < pad_to_16(ciphertext); ++i)
+        mac_data.append(0);
+
+    u8 placeholder[8] = { 0 };
+    // The length of the additional data in octets (as a 64-bit little-endian integer).
+    mac_data.append(ReadonlyBytes { placeholder, 8 });
+    ByteReader::store(static_cast<u8*>(mac_data.end_pointer()) - sizeof(u64), AK::convert_between_host_and_little_endian(static_cast<u64>(aad.size())));
+
+    // The length of the ciphertext in octets (as a 64-bit little-endian integer).
+    mac_data.append(ReadonlyBytes { placeholder, 8 });
+    ByteReader::store(static_cast<u8*>(mac_data.end_pointer()) - sizeof(u64), AK::convert_between_host_and_little_endian(static_cast<u64>(ciphertext.size())));
+
+    Crypto::Authentication::Poly1305 mac_function(otk);
+    mac_function.update(mac_data.bytes());
+    auto tag = TRY(mac_function.digest());
+
+    // The output from the AEAD is the concatenation of:
+    auto result = TRY(ByteBuffer::create_zeroed(0));
+    result.ensure_capacity(ciphertext.size() + tag.size());
+
+    // A ciphertext of the same length as the plaintext.
+    result.append(ciphertext);
+
+    // A 128-bit tag, which is the output of the Poly1305 function.
+    result.append(tag);
+    return result;
+}
+
+// https://datatracker.ietf.org/doc/html/rfc8439#section-2.8
+ErrorOr<ByteBuffer> ChaCha20Poly1305::decrypt(ReadonlyBytes aad, ReadonlyBytes ciphertext)
+{
+    // Decryption is similar with the following differences:
+    // o  The roles of ciphertext and plaintext are reversed, so the
+    //    ChaCha20 encryption function is applied to the ciphertext,
+    //    producing the plaintext.
+    // o  The Poly1305 function is still run on the AAD and the ciphertext,
+    //    not the plaintext.
+
+    // First, a Poly1305 one-time key is generated from the 256-bit key
+    // and nonce using the procedure described in Section 2.6.
+    auto otk = TRY(poly1305_key());
+
+    // Next, the ChaCha20 encryption function is called to decrypt the
+    // ciphertext, using the same key and nonce, and with the initial
+    // counter set to 1.
+    auto chacha = Crypto::Cipher::ChaCha20(m_key, m_nonce, 1);
+    auto plaintext_buffer = TRY(ByteBuffer::create_zeroed(ciphertext.size()));
+    auto plaintext = plaintext_buffer.bytes();
+    chacha.encrypt(ciphertext, plaintext);
+
+    // Finally, the Poly1305 function is called with the Poly1305 key
+    // calculated above, and a message constructed as a concatenation of
+    // the following:
+    auto mac_data = TRY(ByteBuffer::create_zeroed(0));
+    auto buffer_size = aad.size() + pad_to_16(aad) + ciphertext.size() + pad_to_16(ciphertext) + sizeof(u64) + sizeof(u64);
+    mac_data.ensure_capacity(buffer_size);
+
+    // The AAD
+    mac_data.append(aad);
+
+    // padding1 -- the padding is up to 15 zero bytes, and it brings
+    // the total length so far to an integral multiple of 16.  If the
+    // length of the AAD was already an integral multiple of 16 bytes,
+    // this field is zero-length.
+    for (size_t i = 0; i < pad_to_16(aad); ++i)
+        mac_data.append(0);
+
+    // The ciphertext
+    mac_data.append(ciphertext);
+
+    // padding2 -- the padding is up to 15 zero bytes, and it brings
+    // the total length so far to an integral multiple of 16.  If the
+    // length of the ciphertext was already an integral multiple of 16
+    // bytes, this field is zero-length.
+    for (size_t i = 0; i < pad_to_16(ciphertext); ++i)
+        mac_data.append(0);
+
+    u8 placeholder[8] = { 0 };
+    // The length of the additional data in octets (as a 64-bit little-endian integer).
+    mac_data.append(ReadonlyBytes { placeholder, 8 });
+    ByteReader::store(static_cast<u8*>(mac_data.end_pointer()) - sizeof(u64), AK::convert_between_host_and_little_endian(static_cast<u64>(aad.size())));
+
+    // The length of the ciphertext in octets (as a 64-bit little-endian integer).
+    mac_data.append(ReadonlyBytes { placeholder, 8 });
+    ByteReader::store(static_cast<u8*>(mac_data.end_pointer()) - sizeof(u64), AK::convert_between_host_and_little_endian(static_cast<u64>(ciphertext.size())));
+
+    Crypto::Authentication::Poly1305 mac_function(otk);
+    mac_function.update(mac_data.bytes());
+    auto tag = TRY(mac_function.digest());
+
+    // The output from the AEAD is the concatenation of:
+    auto result = TRY(ByteBuffer::create_zeroed(0));
+    result.ensure_capacity(plaintext.size() + tag.size());
+
+    // A plaintext of the same length as the ciphertext.
+    result.append(plaintext);
+
+    // A 128-bit tag, which is the output of the Poly1305 function.
+    result.append(tag);
+    return result;
+}
+
+// https://datatracker.ietf.org/doc/html/rfc8439#section-4
+bool ChaCha20Poly1305::verify_tag(ReadonlyBytes encrypted, ReadonlyBytes decrypted)
+{
+    // With online protocols, implementation MUST use a constant-time comparison function rather
+    // than relying on optimized but insecure library functions such as the C language's memcmp().
+    auto encrypted_tag = encrypted.slice_from_end(16);
+    auto decrypted_tag = decrypted.slice_from_end(16);
+
+    if (encrypted_tag.size() != decrypted_tag.size())
+        return false;
+
+    auto result = 0;
+    for (size_t i = 0; i < encrypted_tag.size(); ++i)
+        result |= encrypted_tag[i] ^ decrypted_tag[i];
+
+    return result == 0;
+}
+}

Userland/Libraries/LibCrypto/AEAD/ChaCha20Poly1305.h

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2023, stelar7 <dudedbz@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/ByteBuffer.h>
+
+namespace Crypto::AEAD {
+
+class ChaCha20Poly1305 {
+public:
+    explicit ChaCha20Poly1305(ReadonlyBytes key, ReadonlyBytes nonce)
+    {
+        m_key = MUST(ByteBuffer::copy(key));
+        m_nonce = MUST(ByteBuffer::copy(nonce));
+    }
+
+    ErrorOr<ByteBuffer> encrypt(ReadonlyBytes aad, ReadonlyBytes plaintext);
+    ErrorOr<ByteBuffer> decrypt(ReadonlyBytes aad, ReadonlyBytes ciphertext);
+    ErrorOr<ByteBuffer> poly1305_key();
+    static bool verify_tag(ReadonlyBytes encrypted, ReadonlyBytes decrypted);
+
+private:
+    u8 pad_to_16(ReadonlyBytes data)
+    {
+        return 16 - (data.size() % 16);
+    }
+
+    ByteBuffer m_key;
+    ByteBuffer m_nonce;
+};
+}

Userland/Libraries/LibCrypto/CMakeLists.txt

@@ -1,6 +1,7 @@
 add_compile_options(-Wvla)
 
 set(SOURCES
+    AEAD/ChaCha20Poly1305.cpp
     ASN1/ASN1.cpp
     ASN1/DER.cpp
     ASN1/PEM.cpp

Userland/Libraries/LibCrypto/Cipher/ChaCha20.h

@@ -19,10 +19,11 @@ public:
 
     void encrypt(ReadonlyBytes input, Bytes& output);
     void decrypt(ReadonlyBytes input, Bytes& output);
+    void generate_block();
+    ReadonlyBytes block() const { return { m_block, 64 }; }
 
 private:
     void run_cipher(ReadonlyBytes input, Bytes& output);
-    void generate_block();
     ALWAYS_INLINE void do_quarter_round(u32& a, u32& b, u32& c, u32& d);
 
     u32 m_state[16] {};