crypto.hpp

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#pragma once
 
// Cryptographic primitives.
// Portable SHA-256; Mbed TLS: SHA-1, MD5, AES-CBC/GCM, HMAC.
// TweetNaCl: Ed25519 sign/verify.
 
#include <string>
#include <string_view>
#include <vector>
#include <cstddef>
#include <cstdint>
#include <filesystem>
#include <optional>
 
namespace pulp::runtime {
 
// ── Secure random bytes ─────────────────────────────────────────────────

std::optional<std::vector<uint8_t>> secure_random_bytes(size_t size);

void secure_zero_memory(void* data, size_t size) noexcept;
 
// ── Encoding ────────────────────────────────────────────────────────────

inline std::string hex_encode(const uint8_t* data, size_t size) {
    static const char* d = "0123456789abcdef";
    std::string out;
    out.reserve(size * 2);
    for (size_t i = 0; i < size; ++i) {
        out.push_back(d[data[i] >> 4]);
        out.push_back(d[data[i] & 0xF]);
    }
    return out;
}
inline std::string hex_encode(const std::vector<uint8_t>& bytes) {
    return hex_encode(bytes.data(), bytes.size());
}
 
// ── Hashing ─────────────────────────────────────────────────────────────

std::vector<uint8_t> sha256(const uint8_t* data, size_t size);
std::vector<uint8_t> sha256(std::string_view data);

std::string sha256_hex(const uint8_t* data, size_t size);
std::string sha256_hex(std::string_view data);

std::optional<std::string> sha256_file_hex(const std::filesystem::path& path,
                                           std::uint64_t max_bytes);

std::vector<uint8_t> sha1(const uint8_t* data, size_t size);
std::vector<uint8_t> sha1(std::string_view data);

std::vector<uint8_t> md5(const uint8_t* data, size_t size);
std::vector<uint8_t> md5(std::string_view data);

std::string md5_hex(std::string_view data);
 
// ── AES ─────────────────────────────────────────────────────────────────

std::optional<std::vector<uint8_t>> aes_encrypt(
    const uint8_t* plaintext, size_t size,
    const uint8_t* key_32, const uint8_t* iv_16);

std::optional<std::vector<uint8_t>> aes_decrypt(
    const uint8_t* ciphertext, size_t size,
    const uint8_t* key_32, const uint8_t* iv_16);
 
// ── HMAC (RFC 2104 / RFC 2202 / RFC 4231) ───────────────────────────────

std::optional<std::vector<uint8_t>> hmac_sha256(
    const uint8_t* key, size_t key_size,
    const uint8_t* data, size_t data_size);
std::optional<std::vector<uint8_t>> hmac_sha256(std::string_view key,
                                                  std::string_view data);

std::optional<std::vector<uint8_t>> hmac_sha1(
    const uint8_t* key, size_t key_size,
    const uint8_t* data, size_t data_size);
 
// ── AES-GCM (AEAD, NIST SP 800-38D) ─────────────────────────────────────

struct GcmOutput {
    std::vector<uint8_t> ciphertext;
    std::vector<uint8_t> tag; 
};

std::optional<GcmOutput> aes_gcm_encrypt(
    const uint8_t* plaintext, size_t plaintext_size,
    const uint8_t* key_32,
    const uint8_t* iv_12, size_t iv_size,
    const uint8_t* aad, size_t aad_size);

std::optional<std::vector<uint8_t>> aes_gcm_decrypt(
    const uint8_t* ciphertext, size_t ciphertext_size,
    const uint8_t* key_32,
    const uint8_t* iv_12, size_t iv_size,
    const uint8_t* aad, size_t aad_size,
    const uint8_t* tag_16);
 
// ── Constant-time comparison ────────────────────────────────────────────

bool constant_time_equal(const uint8_t* a, const uint8_t* b, size_t size);
 
// ── Ed25519 (RFC 8032) ──────────────────────────────────────────────────
//
// Detached EdDSA signing over the Ed25519 curve. Used by:
//   - Sparkle appcast `edSignature` (macOS auto-update)
//
// Implementation: vendored TweetNaCl reference (public domain, RFC 8032
// compliant). TweetNaCl exposes a combined sign-and-message API; the
// wrappers here expose a detached 64-byte signature for direct
// interoperability with Sparkle and most ecosystem tools.

inline constexpr size_t ed25519_public_key_size = 32;
inline constexpr size_t ed25519_private_key_size = 64;  // seed (32) + public key (32)
inline constexpr size_t ed25519_seed_size = 32;
inline constexpr size_t ed25519_signature_size = 64;

struct Ed25519KeyPair {
    std::vector<uint8_t> public_key;   
    std::vector<uint8_t> private_key;  
};

std::optional<Ed25519KeyPair> ed25519_keypair_generate();

std::optional<Ed25519KeyPair> ed25519_keypair_from_seed(
    const uint8_t* seed_32, size_t seed_size);

std::optional<std::vector<uint8_t>> ed25519_sign(
    const uint8_t* private_key_64, size_t private_key_size,
    const uint8_t* message, size_t message_size);

bool ed25519_verify(
    const uint8_t* public_key_32, size_t public_key_size,
    const uint8_t* signature_64, size_t signature_size,
    const uint8_t* message, size_t message_size);
 
// ── X25519 (RFC 7748) ───────────────────────────────────────────────────
//
// Elliptic-curve Diffie-Hellman over Curve25519. Used by:
//   - Forge private-backup capsules, to wrap a content key to the
//     creator's identity key and to a recovery key
//
// Implementation: the same vendored TweetNaCl reference that backs
// Ed25519 above. `crypto_scalarmult` performs RFC 7748 scalar decoding
// (clamping) on its own private copy, so a private key here is 32
// arbitrary bytes and callers must not pre-clamp.
//
// Ed25519 keys cannot stand in for these. Ed25519 signs; it carries no
// key-agreement operation, which is the whole reason this section exists.

inline constexpr size_t x25519_public_key_size = 32;
inline constexpr size_t x25519_private_key_size = 32;
inline constexpr size_t x25519_shared_secret_size = 32;

struct X25519KeyPair {
    std::vector<uint8_t> public_key;   
    std::vector<uint8_t> private_key;  
};

std::optional<X25519KeyPair> x25519_keypair_generate();

std::optional<X25519KeyPair> x25519_keypair_from_private_key(
    const uint8_t* private_key_32, size_t private_key_size);

std::optional<std::vector<uint8_t>> x25519_shared_secret(
    const uint8_t* private_key_32, size_t private_key_size,
    const uint8_t* peer_public_key_32, size_t peer_public_key_size);
 
// ── Machine ID ──────────────────────────────────────────────────────────

std::string machine_id();
 
}  // namespace pulp::runtime