From 9ff0768bdcca06836ccc673eacfa648e801930cb Mon Sep 17 00:00:00 2001 From: Pieter Wuille Date: Fri, 30 Jun 2023 00:30:34 -0400 Subject: [PATCH] crypto: add the ChaCha20Poly1305 AEAD as specified in RFC8439 This adds an implementation of the ChaCha20Poly1305 AEAD exactly matching the version specified in RFC8439 section 2.8, including tests and official test vectors. --- src/Makefile.am | 2 + src/crypto/chacha20poly1305.cpp | 101 ++++++++++++++++++++++++++++++++ src/crypto/chacha20poly1305.h | 51 ++++++++++++++++ src/test/crypto_tests.cpp | 77 ++++++++++++++++++++++++ 4 files changed, 231 insertions(+) create mode 100644 src/crypto/chacha20poly1305.cpp create mode 100644 src/crypto/chacha20poly1305.h diff --git a/src/Makefile.am b/src/Makefile.am index d8ea4bbd285..b6fe2563350 100644 --- a/src/Makefile.am +++ b/src/Makefile.am @@ -548,6 +548,8 @@ crypto_libbitcoin_crypto_base_la_SOURCES = \ crypto/aes.h \ crypto/chacha20.h \ crypto/chacha20.cpp \ + crypto/chacha20poly1305.h \ + crypto/chacha20poly1305.cpp \ crypto/common.h \ crypto/hkdf_sha256_32.cpp \ crypto/hkdf_sha256_32.h \ diff --git a/src/crypto/chacha20poly1305.cpp b/src/crypto/chacha20poly1305.cpp new file mode 100644 index 00000000000..5f27857213c --- /dev/null +++ b/src/crypto/chacha20poly1305.cpp @@ -0,0 +1,101 @@ +// Copyright (c) 2023 The Bitcoin Core developers +// Distributed under the MIT software license, see the accompanying +// file COPYING or http://www.opensource.org/licenses/mit-license.php. + +#include + +#include +#include +#include +#include + +#include +#include +#include +#include + +AEADChaCha20Poly1305::AEADChaCha20Poly1305(Span key) noexcept : m_chacha20(UCharCast(key.data())) +{ + assert(key.size() == KEYLEN); +} + +void AEADChaCha20Poly1305::SetKey(Span key) noexcept +{ + assert(key.size() == KEYLEN); + m_chacha20.SetKey32(UCharCast(key.data())); +} + +namespace { + +#ifndef HAVE_TIMINGSAFE_BCMP +#define HAVE_TIMINGSAFE_BCMP + +int timingsafe_bcmp(const unsigned char* b1, const unsigned char* b2, size_t n) noexcept +{ + const unsigned char *p1 = b1, *p2 = b2; + int ret = 0; + for (; n > 0; n--) + ret |= *p1++ ^ *p2++; + return (ret != 0); +} + +#endif + +/** Compute poly1305 tag. chacha20 must be set to the right nonce, block 0. Will be at block 1 after. */ +void ComputeTag(ChaCha20& chacha20, Span aad, Span cipher, Span tag) noexcept +{ + static const std::byte PADDING[16] = {{}}; + + // Get block of keystream (use a full 64 byte buffer to avoid the need for chacha20's own buffering). + std::byte first_block[64]; + chacha20.Keystream(UCharCast(first_block), sizeof(first_block)); + + // Use the first 32 bytes of the first keystream block as poly1305 key. + Poly1305 poly1305{Span{first_block}.first(Poly1305::KEYLEN)}; + + // Compute tag: + // - Process the padded AAD with Poly1305. + const unsigned aad_padding_length = (16 - (aad.size() % 16)) % 16; + poly1305.Update(aad).Update(Span{PADDING}.first(aad_padding_length)); + // - Process the padded ciphertext with Poly1305. + const unsigned cipher_padding_length = (16 - (cipher.size() % 16)) % 16; + poly1305.Update(cipher).Update(Span{PADDING}.first(cipher_padding_length)); + // - Process the AAD and plaintext length with Poly1305. + std::byte length_desc[Poly1305::TAGLEN]; + WriteLE64(UCharCast(length_desc), aad.size()); + WriteLE64(UCharCast(length_desc + 8), cipher.size()); + poly1305.Update(length_desc); + + // Output tag. + poly1305.Finalize(tag); +} + +} // namespace + +void AEADChaCha20Poly1305::Encrypt(Span plain, Span aad, Nonce96 nonce, Span cipher) noexcept +{ + assert(cipher.size() == plain.size() + EXPANSION); + + // Encrypt using ChaCha20 (starting at block 1). + m_chacha20.Seek64(nonce, 1); + m_chacha20.Crypt(UCharCast(plain.data()), UCharCast(cipher.data()), plain.size()); + + // Seek to block 0, and compute tag using key drawn from there. + m_chacha20.Seek64(nonce, 0); + ComputeTag(m_chacha20, aad, cipher.first(plain.size()), cipher.last(EXPANSION)); +} + +bool AEADChaCha20Poly1305::Decrypt(Span cipher, Span aad, Nonce96 nonce, Span plain) noexcept +{ + assert(cipher.size() == plain.size() + EXPANSION); + + // Verify tag (using key drawn from block 0). + m_chacha20.Seek64(nonce, 0); + std::byte expected_tag[EXPANSION]; + ComputeTag(m_chacha20, aad, cipher.first(plain.size()), expected_tag); + if (timingsafe_bcmp(UCharCast(expected_tag), UCharCast(cipher.data() + plain.size()), EXPANSION)) return false; + + // Decrypt (starting at block 1). + m_chacha20.Crypt(UCharCast(cipher.data()), UCharCast(plain.data()), plain.size()); + return true; +} diff --git a/src/crypto/chacha20poly1305.h b/src/crypto/chacha20poly1305.h new file mode 100644 index 00000000000..0007ee63a96 --- /dev/null +++ b/src/crypto/chacha20poly1305.h @@ -0,0 +1,51 @@ +// Copyright (c) 2023 The Bitcoin Core developers +// Distributed under the MIT software license, see the accompanying +// file COPYING or http://www.opensource.org/licenses/mit-license.php. + +#ifndef BITCOIN_CRYPTO_CHACHA20POLY1305_H +#define BITCOIN_CRYPTO_CHACHA20POLY1305_H + +#include +#include +#include + +#include +#include +#include + +/** The AEAD_CHACHA20_POLY1305 authenticated encryption algorithm from RFC8439 section 2.8. */ +class AEADChaCha20Poly1305 +{ + /** Internal stream cipher. */ + ChaCha20 m_chacha20; + +public: + /** Expected size of key argument in constructor. */ + static constexpr unsigned KEYLEN = 32; + + /** Expansion when encrypting. */ + static constexpr unsigned EXPANSION = Poly1305::TAGLEN; + + /** Initialize an AEAD instance with a specified 32-byte key. */ + AEADChaCha20Poly1305(Span key) noexcept; + + /** Switch to another 32-byte key. */ + void SetKey(Span key) noexcept; + + /** 96-bit nonce type. */ + using Nonce96 = ChaCha20::Nonce96; + + /** Encrypt a message with a specified 96-bit nonce and aad. + * + * Requires cipher.size() = plain.size() + EXPANSION. + */ + void Encrypt(Span plain, Span aad, Nonce96 nonce, Span cipher) noexcept; + + /** Decrypt a message with a specified 96-bit nonce and aad. Returns true if valid. + * + * Requires cipher.size() = plain.size() + EXPANSION. + */ + bool Decrypt(Span cipher, Span aad, Nonce96 nonce, Span plain) noexcept; +}; + +#endif // BITCOIN_CRYPTO_CHACHA20POLY1305_H diff --git a/src/test/crypto_tests.cpp b/src/test/crypto_tests.cpp index 809b8979985..f62072f5bbe 100644 --- a/src/test/crypto_tests.cpp +++ b/src/test/crypto_tests.cpp @@ -4,6 +4,7 @@ #include #include +#include #include #include #include @@ -207,6 +208,24 @@ static void TestPoly1305(const std::string &hexmessage, const std::string &hexke } } +static void TestChaCha20Poly1305(const std::string& plain_hex, const std::string& aad_hex, const std::string& key_hex, ChaCha20::Nonce96 nonce, const std::string& cipher_hex) +{ + auto plain = ParseHex(plain_hex); + auto aad = ParseHex(aad_hex); + auto key = ParseHex(key_hex); + auto expected_cipher = ParseHex(cipher_hex); + + std::vector cipher(plain.size() + AEADChaCha20Poly1305::EXPANSION); + AEADChaCha20Poly1305 aead{key}; + aead.Encrypt(plain, aad, nonce, cipher); + BOOST_CHECK(cipher == expected_cipher); + + std::vector decipher(cipher.size() - AEADChaCha20Poly1305::EXPANSION); + bool ret = aead.Decrypt(cipher, aad, nonce, decipher); + BOOST_CHECK(ret); + BOOST_CHECK(decipher == plain); +} + static void TestHKDF_SHA256_32(const std::string &ikm_hex, const std::string &salt_hex, const std::string &info_hex, const std::string &okm_check_hex) { std::vector initial_key_material = ParseHex(ikm_hex); std::vector salt = ParseHex(salt_hex); @@ -818,6 +837,64 @@ BOOST_AUTO_TEST_CASE(poly1305_testvector) "0e410fa9d7a40ac582e77546be9a72bb"); } +BOOST_AUTO_TEST_CASE(chacha20poly1305_testvectors) +{ + // Note that in our implementation, the authentication is suffixed to the ciphertext. + // The RFC test vectors specify them separately. + + // RFC 8439 Example from section 2.8.2 + TestChaCha20Poly1305("4c616469657320616e642047656e746c656d656e206f662074686520636c6173" + "73206f66202739393a204966204920636f756c64206f6666657220796f75206f" + "6e6c79206f6e652074697020666f7220746865206675747572652c2073756e73" + "637265656e20776f756c642062652069742e", + "50515253c0c1c2c3c4c5c6c7", + "808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f", + {7, 0x4746454443424140}, + "d31a8d34648e60db7b86afbc53ef7ec2a4aded51296e08fea9e2b5a736ee62d6" + "3dbea45e8ca9671282fafb69da92728b1a71de0a9e060b2905d6a5b67ecd3b36" + "92ddbd7f2d778b8c9803aee328091b58fab324e4fad675945585808b4831d7bc" + "3ff4def08e4b7a9de576d26586cec64b61161ae10b594f09e26a7e902ecbd060" + "0691"); + + // RFC 8439 Test vector A.5 + TestChaCha20Poly1305("496e7465726e65742d4472616674732061726520647261667420646f63756d65" + "6e74732076616c696420666f722061206d6178696d756d206f6620736978206d" + "6f6e74687320616e64206d617920626520757064617465642c207265706c6163" + "65642c206f72206f62736f6c65746564206279206f7468657220646f63756d65" + "6e747320617420616e792074696d652e20497420697320696e617070726f7072" + "6961746520746f2075736520496e7465726e65742d4472616674732061732072" + "65666572656e6365206d6174657269616c206f7220746f206369746520746865" + "6d206f74686572207468616e206173202fe2809c776f726b20696e2070726f67" + "726573732e2fe2809d", + "f33388860000000000004e91", + "1c9240a5eb55d38af333888604f6b5f0473917c1402b80099dca5cbc207075c0", + {0, 0x0807060504030201}, + "64a0861575861af460f062c79be643bd5e805cfd345cf389f108670ac76c8cb2" + "4c6cfc18755d43eea09ee94e382d26b0bdb7b73c321b0100d4f03b7f355894cf" + "332f830e710b97ce98c8a84abd0b948114ad176e008d33bd60f982b1ff37c855" + "9797a06ef4f0ef61c186324e2b3506383606907b6a7c02b0f9f6157b53c867e4" + "b9166c767b804d46a59b5216cde7a4e99040c5a40433225ee282a1b0a06c523e" + "af4534d7f83fa1155b0047718cbc546a0d072b04b3564eea1b422273f548271a" + "0bb2316053fa76991955ebd63159434ecebb4e466dae5a1073a6727627097a10" + "49e617d91d361094fa68f0ff77987130305beaba2eda04df997b714d6c6f2c29" + "a6ad5cb4022b02709beead9d67890cbb22392336fea1851f38"); + + // Test vectors exercising aad and plaintext which are multiples of 16 bytes. + TestChaCha20Poly1305("8d2d6a8befd9716fab35819eaac83b33269afb9f1a00fddf66095a6c0cd91951" + "a6b7ad3db580be0674c3f0b55f618e34", + "", + "72ddc73f07101282bbbcf853b9012a9f9695fc5d36b303a97fd0845d0314e0c3", + {0x3432b75f, 0xb3585537eb7f4024}, + "f760b8224fb2a317b1b07875092606131232a5b86ae142df5df1c846a7f6341a" + "f2564483dd77f836be45e6230808ffe402a6f0a3e8be074b3d1f4ea8a7b09451"); + TestChaCha20Poly1305("", + "36970d8a704c065de16250c18033de5a400520ac1b5842b24551e5823a3314f3" + "946285171e04a81ebfbe3566e312e74ab80e94c7dd2ff4e10de0098a58d0f503", + "77adda51d6730b9ad6c995658cbd49f581b2547e7c0c08fcc24ceec797461021", + {0x1f90da88, 0x75dafa3ef84471a4}, + "aaae5bb81e8407c94b2ae86ae0c7efbe"); +} + BOOST_AUTO_TEST_CASE(hkdf_hmac_sha256_l32_tests) { // Use rfc5869 test vectors but truncated to 32 bytes (our implementation only support length 32)