70ecd6caa0
Transaction Science open standards monorepo. Each subdirectory is a self-contained reference protocol with its own README and licence. - openpay/ Apache-2.0 payment-acceptance stack (Rust, 26 crates) - smart-byte/ CC-BY-4.0 content-addressed value carrier (spec) - eoc/ CC-BY-4.0 energy-optimised compute (spec) The wire format and the right to fork are public. The optional hosted services are the offer; the protocols are not.
538 lines
18 KiB
Rust
538 lines
18 KiB
Rust
//! [`InMemoryVault`] — reference implementation backed by AES-256-GCM-SIV.
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//!
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//! ## Status
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//!
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//! This is a **reference implementation**. It is correct, well-tested,
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//! and exhibits the exact behavior the [`Vault`] trait promises. It is
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//! NOT a PCI-compliant production vault on its own:
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//!
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//! - **State is in RAM only.** A restart loses every token. Real vaults
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//! persist ciphertext to durable storage (DB, HSM, KMS-encrypted file).
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//! - **The encryption key is operator-supplied.** Real vaults integrate
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//! with KMS / HSM for key management with rotation, dual control,
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//! split knowledge, and FIPS 140-2 Level 2/3 modules.
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//! - **No audit logging.** PCI DSS requires log emission for every
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//! detokenize call with user identity, timestamp, and outcome.
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//! - **No rate limiting.** Real vaults bound detokenize throughput per
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//! caller to limit blast radius on credential compromise.
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//!
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//! Use this in tests, CI, and local development. For production deploy
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//! a platform vault (iOS Keychain / Android Keystore / AWS KMS /
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//! `HashiCorp` Vault / on-prem HSM) behind the same [`Vault`] trait.
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//!
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//! ## Cryptography
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//!
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//! AES-256-GCM-SIV per RFC 8452. Misuse-resistant: a nonce collision
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//! doesn't catastrophically break confidentiality the way it does in
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//! plain AES-GCM. Each ciphertext carries its own 96-bit random nonce
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//! prepended to the bytes.
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//!
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//! ## Token format
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//!
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//! Tokens are UUID v7 strings prefixed with `tok_v7_`. UUID v7 carries
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//! a timestamp prefix that makes tokens sortable by issuance time —
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//! useful for vault analytics — without revealing the underlying PAN
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//! mapping (the random suffix dominates).
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use std::collections::HashMap;
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use std::sync::Mutex;
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use aes_gcm_siv::aead::{Aead, KeyInit, OsRng};
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use aes_gcm_siv::{AeadCore, Aes256GcmSiv, Key, Nonce};
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use op_core::VaultRef;
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use rand_core::RngCore;
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use time::OffsetDateTime;
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use uuid::Uuid;
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use zeroize::{Zeroize, ZeroizeOnDrop};
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use crate::card_data::CardData;
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use crate::error::{Error, Result};
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use crate::policy::{TokenLifetime, TokenizationPolicy};
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use crate::vault::Vault;
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/// Token id prefix. Picked so tokens are visually distinguishable from
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/// PANs (which are all-digit) — per PCI DSS Tokenization Guidelines
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/// §3.3, tokens must not be confusable with their underlying PAN.
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pub const TOKEN_PREFIX: &str = "tok_v7_";
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/// Plaintext payload that gets encrypted into the vault.
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///
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/// JSON-serialized then encrypted. We use JSON for forward-compat
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/// (adding a field doesn't break existing ciphertexts) at the cost of
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/// some size overhead. The encryption itself doesn't care about the
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/// payload format; this is a vault-internal choice.
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#[derive(serde::Serialize, serde::Deserialize, Zeroize, ZeroizeOnDrop)]
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struct StoredCard {
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pan: String,
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exp_month: u8,
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exp_year: u16,
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}
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/// Per-token metadata held alongside the ciphertext. Not encrypted —
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/// these fields are used to enforce policy before attempting decryption.
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struct Metadata {
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/// 96-bit nonce used to encrypt this entry.
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nonce: [u8; 12],
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/// Encrypted JSON of `StoredCard`.
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ciphertext: Vec<u8>,
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/// Original policy at issuance.
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policy: TokenizationPolicy,
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/// Unix-seconds at which the token was minted.
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issued_at: i64,
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/// Single-use tokens flip this on first successful detokenize.
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consumed: bool,
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}
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/// AES-256-GCM-SIV-backed reference vault.
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pub struct InMemoryVault {
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name: String,
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cipher: Aes256GcmSiv,
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store: Mutex<HashMap<String, Metadata>>,
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}
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impl InMemoryVault {
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/// Construct with a fresh random key. Useful for tests and ephemeral
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/// development. The key is lost on drop; tokens issued by this
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/// vault are unrecoverable across instances.
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#[must_use]
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pub fn ephemeral(name: impl Into<String>) -> Self {
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let key = Aes256GcmSiv::generate_key(&mut OsRng);
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Self::with_key(name, &key)
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}
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/// Construct with an operator-supplied 32-byte key. The operator
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/// is responsible for key management, rotation, and persistence;
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/// the vault stores only ciphertext.
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#[must_use]
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pub fn with_key(name: impl Into<String>, key: &Key<Aes256GcmSiv>) -> Self {
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let cipher = Aes256GcmSiv::new(key);
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Self {
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name: name.into(),
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cipher,
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store: Mutex::new(HashMap::new()),
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}
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}
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/// Number of tokens currently held. Test-only utility.
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#[cfg(test)]
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pub(crate) fn len(&self) -> usize {
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self.store.lock().expect("poisoned").len()
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}
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}
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impl Vault for InMemoryVault {
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fn name(&self) -> &str {
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&self.name
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}
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fn tokenize(&self, card: CardData, policy: TokenizationPolicy) -> Result<VaultRef> {
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// Serialize the card payload.
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let stored = StoredCard {
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pan: core::str::from_utf8(card.raw().pan_bytes())
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.map_err(|_| Error::Backend("non-utf8 pan".into()))?
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.to_owned(),
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exp_month: card.exp_month(),
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exp_year: card.exp_year(),
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};
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let plaintext =
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serde_json::to_vec(&stored).map_err(|e| Error::Backend(format!("serialize: {e}")))?;
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// Random 96-bit nonce. GCM-SIV is misuse-resistant so the
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// catastrophic failure on accidental reuse doesn't apply, but
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// we still want fresh nonces per entry as a defense in depth.
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let nonce = Aes256GcmSiv::generate_nonce(&mut OsRng);
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let ciphertext = self
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.cipher
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.encrypt(&nonce, plaintext.as_ref())
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.map_err(|_| Error::Backend("encrypt".into()))?;
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// Mint a token id. UUID v7 carries a millisecond timestamp
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// prefix; the random suffix is what makes it cryptographically
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// independent from the PAN.
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let token_id = format!("{TOKEN_PREFIX}{}", Uuid::now_v7().simple());
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let issued_at = OffsetDateTime::now_utc().unix_timestamp();
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let mut nonce_arr = [0u8; 12];
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nonce_arr.copy_from_slice(nonce.as_slice());
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let metadata = Metadata {
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nonce: nonce_arr,
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ciphertext,
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policy,
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issued_at,
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consumed: false,
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};
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self.store
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.lock()
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.map_err(|_| Error::Backend("lock poisoned".into()))?
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.insert(token_id.clone(), metadata);
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Ok(VaultRef::new(token_id))
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}
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fn detokenize(&self, token: &VaultRef) -> Result<CardData> {
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let id = token.as_str();
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if !id.starts_with(TOKEN_PREFIX) {
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return Err(Error::InvalidToken);
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}
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let mut store = self
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.store
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.lock()
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.map_err(|_| Error::Backend("lock poisoned".into()))?;
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let metadata = store.get_mut(id).ok_or(Error::NotFound)?;
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// Check expiration.
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if let Some(ttl) = metadata.policy.ttl_seconds {
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let now = OffsetDateTime::now_utc().unix_timestamp();
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// `ttl` is u64, `now - issued_at` is i64. A negative age
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// (clock skew / backdated issue) can't be expired.
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let age = now.saturating_sub(metadata.issued_at);
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if u64::try_from(age).is_ok_and(|a| a >= ttl) {
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return Err(Error::Expired);
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}
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}
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// Check single-use.
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if metadata.policy.lifetime == TokenLifetime::SingleUse && metadata.consumed {
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return Err(Error::AlreadyConsumed);
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}
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// Decrypt.
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let nonce = Nonce::from_slice(&metadata.nonce);
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let plaintext = self
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.cipher
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.decrypt(nonce, metadata.ciphertext.as_ref())
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.map_err(|_| Error::AuthFailed)?;
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let stored: StoredCard = serde_json::from_slice(&plaintext)
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.map_err(|e| Error::Backend(format!("deserialize: {e}")))?;
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// Flip single-use marker AFTER successful decryption so a
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// failed attempt doesn't burn the token. Real vaults debate
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// both orderings; we choose forgiveness on the in-memory
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// reference.
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if metadata.policy.lifetime == TokenLifetime::SingleUse {
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metadata.consumed = true;
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}
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// Re-construct CardData by going through the validated
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// constructor — this means we re-run Luhn on detokenize, which
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// catches ciphertext tampering that somehow produced a valid
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// decryption but invalid PAN. Belt and braces.
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CardData::new(stored.pan.clone(), stored.exp_month, stored.exp_year)
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}
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fn exists(&self, token: &VaultRef) -> Result<bool> {
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let id = token.as_str();
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if !id.starts_with(TOKEN_PREFIX) {
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return Ok(false);
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}
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Ok(self
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.store
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.lock()
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.map_err(|_| Error::Backend("lock poisoned".into()))?
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.contains_key(id))
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}
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fn delete(&self, token: &VaultRef) -> Result<bool> {
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let id = token.as_str();
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if !id.starts_with(TOKEN_PREFIX) {
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return Ok(false);
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}
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Ok(self
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.store
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.lock()
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.map_err(|_| Error::Backend("lock poisoned".into()))?
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.remove(id)
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.is_some())
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}
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}
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/// Generate a fresh 32-byte key. Convenience helper; operators should
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/// derive keys from KMS / HSM in production.
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#[must_use]
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pub fn generate_key() -> [u8; 32] {
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let mut key = [0u8; 32];
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OsRng.fill_bytes(&mut key);
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key
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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const VALID_VISA: &str = "4242424242424242";
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const VALID_MC: &str = "5555555555554444";
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fn vault() -> InMemoryVault {
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InMemoryVault::ephemeral("test")
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}
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fn card() -> CardData {
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CardData::new(VALID_VISA, 12, 2030).unwrap()
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}
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#[test]
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fn tokenize_returns_well_formed_token() {
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let v = vault();
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let token = v.tokenize(card(), TokenizationPolicy::default()).unwrap();
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assert!(token.as_str().starts_with(TOKEN_PREFIX));
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assert!(token.as_str().len() > TOKEN_PREFIX.len() + 10);
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}
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#[test]
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fn tokenize_then_detokenize_round_trips() {
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let v = vault();
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let original = card();
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let token = v
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.tokenize(original.clone(), TokenizationPolicy::default())
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.unwrap();
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let recovered = v.detokenize(&token).unwrap();
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// Verify last4 / first6 match — never compare full PAN in test logs.
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assert_eq!(original.last_four(), recovered.last_four());
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assert_eq!(original.first_six(), recovered.first_six());
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assert_eq!(original.exp_month(), recovered.exp_month());
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assert_eq!(original.exp_year(), recovered.exp_year());
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}
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#[test]
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fn detokenize_unknown_token_returns_not_found() {
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let v = vault();
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let fake = VaultRef::new(format!("{TOKEN_PREFIX}{}", Uuid::now_v7().simple()));
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let err = v.detokenize(&fake).unwrap_err();
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assert!(matches!(err, Error::NotFound));
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}
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#[test]
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fn detokenize_malformed_token_returns_invalid() {
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let v = vault();
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let bad = VaultRef::new("4242424242424242"); // looks like a PAN
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let err = v.detokenize(&bad).unwrap_err();
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assert!(matches!(err, Error::InvalidToken));
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}
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#[test]
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fn delete_removes_mapping() {
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let v = vault();
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let token = v.tokenize(card(), TokenizationPolicy::default()).unwrap();
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assert!(v.exists(&token).unwrap());
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let removed = v.delete(&token).unwrap();
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assert!(removed);
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assert!(!v.exists(&token).unwrap());
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// Second delete is a no-op (idempotent).
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let removed = v.delete(&token).unwrap();
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assert!(!removed);
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}
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#[test]
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fn exists_returns_false_for_unknown() {
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let v = vault();
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let fake = VaultRef::new(format!("{TOKEN_PREFIX}deadbeef"));
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assert!(!v.exists(&fake).unwrap());
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}
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#[test]
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fn exists_returns_false_for_non_token_string() {
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let v = vault();
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let not_a_token = VaultRef::new("definitely-not-a-token");
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assert!(!v.exists(¬_a_token).unwrap());
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}
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#[test]
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fn single_use_token_consumed_on_first_detokenize() {
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let v = vault();
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let policy = TokenizationPolicy::single_use(60);
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let token = v.tokenize(card(), policy).unwrap();
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// First call succeeds.
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let _ = v.detokenize(&token).unwrap();
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// Second call fails.
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let err = v.detokenize(&token).unwrap_err();
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assert!(matches!(err, Error::AlreadyConsumed));
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}
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#[test]
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fn reusable_token_survives_multiple_detokenizes() {
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let v = vault();
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let token = v.tokenize(card(), TokenizationPolicy::default()).unwrap();
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for _ in 0..5 {
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assert!(v.detokenize(&token).is_ok());
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}
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}
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#[test]
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fn tokens_for_same_pan_are_unique_under_random_policy() {
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let v = vault();
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let policy = TokenizationPolicy::default();
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let a = v.tokenize(card(), policy).unwrap();
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let b = v.tokenize(card(), policy).unwrap();
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assert_ne!(
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a.as_str(),
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b.as_str(),
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"Random format must produce distinct tokens for identical PANs"
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);
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}
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#[test]
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fn different_cards_produce_different_tokens() {
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let v = vault();
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let c1 = CardData::new(VALID_VISA, 12, 2030).unwrap();
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let c2 = CardData::new(VALID_MC, 12, 2030).unwrap();
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let t1 = v.tokenize(c1, TokenizationPolicy::default()).unwrap();
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let t2 = v.tokenize(c2, TokenizationPolicy::default()).unwrap();
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assert_ne!(t1.as_str(), t2.as_str());
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}
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#[test]
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fn vault_with_different_key_cannot_decrypt() {
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let v1 = vault();
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let v2 = vault(); // different ephemeral key
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let token = v1.tokenize(card(), TokenizationPolicy::default()).unwrap();
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// v2 doesn't have this token at all (separate HashMap), so it's
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// NotFound rather than AuthFailed. This is the right behavior —
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// AuthFailed would leak existence.
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let err = v2.detokenize(&token).unwrap_err();
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assert!(matches!(err, Error::NotFound));
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}
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#[test]
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fn with_key_constructor_is_deterministic_per_key() {
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// Same key → same vault can decrypt tokens issued by the other.
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// We achieve this by sharing the key array.
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let key_bytes = generate_key();
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let key = Key::<Aes256GcmSiv>::from_slice(&key_bytes);
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let v1 = InMemoryVault::with_key("v1", key);
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// Issue a token, manually copy ciphertext+nonce to a fresh
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// vault with the same key.
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let token = v1.tokenize(card(), TokenizationPolicy::default()).unwrap();
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// Build a new vault with the same key and inject the metadata.
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let v2 = InMemoryVault::with_key("v2", key);
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{
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let mut s1 = v1.store.lock().unwrap();
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let mut s2 = v2.store.lock().unwrap();
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for (k, m) in s1.drain() {
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s2.insert(
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k,
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Metadata {
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nonce: m.nonce,
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ciphertext: m.ciphertext,
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policy: m.policy,
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issued_at: m.issued_at,
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consumed: m.consumed,
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},
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);
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}
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}
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// v2 can decrypt v1's token.
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let recovered = v2.detokenize(&token).unwrap();
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assert_eq!(recovered.last_four(), "4242");
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}
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#[test]
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fn vault_is_object_safe() {
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let v: Box<dyn Vault> = Box::new(vault());
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assert_eq!(v.name(), "test");
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}
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#[test]
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fn generate_key_produces_32_bytes_of_entropy() {
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let k1 = generate_key();
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let k2 = generate_key();
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assert_eq!(k1.len(), 32);
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assert_ne!(k1, k2, "two random keys must differ");
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// Sanity: not all zeros (extremely unlikely from CSPRNG).
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assert!(k1.iter().any(|&b| b != 0));
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}
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#[test]
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fn tokenize_len_increases_then_delete_decreases() {
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let v = vault();
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assert_eq!(v.len(), 0);
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let t1 = v.tokenize(card(), TokenizationPolicy::default()).unwrap();
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assert_eq!(v.len(), 1);
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let t2 = v.tokenize(card(), TokenizationPolicy::default()).unwrap();
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assert_eq!(v.len(), 2);
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v.delete(&t1).unwrap();
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assert_eq!(v.len(), 1);
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v.delete(&t2).unwrap();
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assert_eq!(v.len(), 0);
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}
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#[test]
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fn health_check_default_impl_returns_ok() {
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assert!(vault().health_check().is_ok());
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}
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#[test]
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fn token_prefix_makes_tokens_unlike_pans() {
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let v = vault();
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let token = v.tokenize(card(), TokenizationPolicy::default()).unwrap();
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// PCI Tokenization Guidelines §3.3: tokens must not be
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// confusable with PANs. Our prefix is non-numeric.
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assert!(
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token.as_str().chars().any(|c| !c.is_ascii_digit()),
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"token must contain non-digit characters to be distinguishable from PAN"
|
|
);
|
|
}
|
|
|
|
#[test]
|
|
fn ttl_expired_token_returns_expired() {
|
|
// Tokenize with a 60-second TTL, then mutate the issued_at
|
|
// timestamp backwards by 120 seconds to simulate the passage
|
|
// of time without actually sleeping.
|
|
let v = vault();
|
|
let policy = TokenizationPolicy {
|
|
ttl_seconds: Some(60),
|
|
..Default::default()
|
|
};
|
|
let token = v.tokenize(card(), policy).unwrap();
|
|
|
|
// Rewind the issued_at to make this entry "old".
|
|
{
|
|
let mut store = v.store.lock().unwrap();
|
|
let metadata = store.get_mut(token.as_str()).unwrap();
|
|
metadata.issued_at -= 120;
|
|
}
|
|
|
|
let err = v.detokenize(&token).unwrap_err();
|
|
assert!(matches!(err, Error::Expired));
|
|
}
|
|
|
|
#[test]
|
|
fn ttl_zero_means_expired_immediately() {
|
|
let v = vault();
|
|
let policy = TokenizationPolicy {
|
|
ttl_seconds: Some(0),
|
|
..Default::default()
|
|
};
|
|
let token = v.tokenize(card(), policy).unwrap();
|
|
let err = v.detokenize(&token).unwrap_err();
|
|
assert!(matches!(err, Error::Expired));
|
|
}
|
|
|
|
#[test]
|
|
fn clock_skew_does_not_falsely_expire() {
|
|
// If now < issued_at (clock went backwards), do NOT expire.
|
|
let v = vault();
|
|
let policy = TokenizationPolicy {
|
|
ttl_seconds: Some(60),
|
|
..Default::default()
|
|
};
|
|
let token = v.tokenize(card(), policy).unwrap();
|
|
|
|
// Push issued_at into the future.
|
|
{
|
|
let mut store = v.store.lock().unwrap();
|
|
let metadata = store.get_mut(token.as_str()).unwrap();
|
|
metadata.issued_at += 1000;
|
|
}
|
|
|
|
// Should NOT be expired (age is negative).
|
|
assert!(v.detokenize(&token).is_ok());
|
|
}
|
|
}
|