aldabra/README.md
Kayos d1c9e7a732 security: enforce max_send_lovelace + sandbox *_path args
Two CRIT findings from the 2026-05-12 Opus audit. Both are
mainnet-blocking against the aldabra-mainnet container.

CRIT-1 — cap-bypass via unsigned-build → sign_partial → submit chain.
Previously `wallet_send` / `wallet_mint` / `wallet_mint_cip68_nft` /
`wallet_script_spend` enforced `max_send_lovelace`, but the unsigned-
build tools + `wallet_sign_partial` + `wallet_submit_signed_tx` did
not. A prompt-injection that walked the cold-signer chain could drain
the wallet past the cap with zero policy enforcement.

Fix:
- `wallet_send_unsigned` / `wallet_mint_unsigned` /
  `wallet_plutus_mint_unsigned` now enforce the cap on the user-
  supplied destination lovelace, mirroring their signed equivalents.
  All three gain a `force: bool` arg with `#[serde(default)]`.
- `wallet_sign_partial` and `wallet_submit_signed_tx` decode the
  Conway tx CBOR, sum lovelace across every output whose address is
  NOT this wallet's own primary address, and enforce the cap on that
  total. Both gain `force: bool`. The chokepoint covers cold-signed
  multi-sig flows and any hand-built CBOR the daemon would otherwise
  blindly sign or submit.
- New free fn `sum_non_self_lovelace` is the unit-testable core of
  the chokepoint logic; `enforce_cap_on_cbor` wraps it.
- The sum uses `try_fold` + `checked_add` (NOT `.sum::<u64>()`) so a
  crafted CBOR that overflows `u64::MAX` fails the check instead of
  wrapping silently in release builds.

CRIT-2 — path traversal via `reference_script_path` and
`policy_cbor_path`. Previously the tools called `std::fs::read_to_
string(p)` on any path the LLM passed. The MCP daemon runs as the
same user that owns `$ALDABRA_DATA/mnemonic.age` /
`$ALDABRA_DATA/root-xprv.age`. Decode-error messages included the
hex_decode position offset — a small but real information leak about
non-hex file structure.

Fix:
- New `Config::safe_reads_root` field (default `$ALDABRA_DATA/scripts/`,
  override via `ALDABRA_SAFE_READS_ROOT` env or TOML).
- New `assert_inside_sandbox` helper canonicalize()s both the root and
  the user-supplied path, then enforces `starts_with`. Rejects
  outside-root paths, `..`-traversal, and nonexistent paths with
  generic messages.
- Hardlink-rejection: post-canonicalize, stat the file and refuse if
  `nlink > 1`. `canonicalize` resolves symlinks but NOT hardlinks (a
  hardlink IS the file — same inode, different directory entry), so
  without this check an attacker with daemon-uid write access could
  plant a hardlink to the encrypted key blob inside the sandbox and
  exfiltrate bytes through the read path.
- `resolve_ref_script_bytes` + `resolve_policy_cbor_bytes` + the
  `resolve_validator_required` wrapper used by all 5 escrow spend
  tools take `&Path` and route through the sandbox.
- Error messages on hex_decode failures no longer carry the path
  string or byte-offset position — return a constant "contents are
  not valid hex" instead.
- `main.rs` creates the sandbox root with 0o700 perms at startup if
  missing. chmod errors are surfaced (not swallowed) so a broken
  filesystem doesn't silently fall back to umask 0o755.
- README documents the new `ALDABRA_SAFE_READS_ROOT` env var alongside
  `ALDABRA_MAX_SEND_LOVELACE` (also previously undocumented).

Tests (243 → 253, +10):
- 5 sandbox tests: accept-inside, reject-outside, reject-dotdot,
  reject-nonexistent, reject-hardlink.
- 1 non-hex regression: constant message (no byte-offset leak).
- 3 cap tests: self-send → 0 non-self total, outbound counts,
  overflow → Err (regression for the prompt-injection `u64::MAX`
  wraparound attempt).
- 1 garbage-CBOR test: clean error.

No new clippy warnings, no new fmt drift, `cargo audit` unchanged
(0 CVEs, 2 transitive unmaintained warnings).

Adversarial review of the first draft (3 Opus reviewers) caught the
u64 overflow, the hardlink bypass, and the swallowed chmod error.
2026-05-12 12:45:03 -07:00

7 KiB

aldabra

Rust-native Cardano lite wallet with an MCP-server interface. Built for LLM-first usage — send/receive ADA + native assets, mint, Plutus script interaction, Conway governance, and a full Agora-on-Cardano DAO client.

Named for the Aldabra giant tortoise: long-lived, defended, slow but unstoppable.

What it does

  • Wallet primitives. Address derivation (CIP-1852), balance + UTXO queries, ADA + native-asset transfers, multi-sig partial signing, encrypted-at-rest mnemonic.
  • Minting. CIP-25 + CIP-68 native assets, custom timelock / multisig policies, unsigned-tx flows for cold signing.
  • Plutus V3. Spending script-locked UTXOs with redeemers, reference scripts, inline datum support.
  • Stake + Conway governance. Pool delegation, DRep registration
    • deregistration, vote delegation, DRep vote casting on governance actions.
  • DAO. Agora-on-Cardano client — register multiple DAOs, view stakes, create + cosign + vote on proposals, advance state-machine, retract votes, destroy stakes.
  • Escrow. Two-party agreement-with-veto Plutus V3 validator with off-chain builders for the full open / deposit / agree / veto / settle / refund lifecycle.

Architecture

Cargo workspace with four crates:

Crate Responsibility
aldabra-core Pure crypto + types. Mnemonic → root key (CIP-3), root → payment + stake keys (CIP-1852), address construction, signing. No I/O, no network. This is the security boundary.
aldabra-chain Pluggable backends for chain queries. ChainBackend trait, with Koios as the default implementation.
aldabra-dao Off-chain side of the Agora DAO + escrow validators. Codecs + unsigned-tx builders.
aldabra-mcp Binary. MCP server speaking stdio. Wires the other crates together and exposes tools to the LLM client.
            ┌─────────────────────────────┐
LLM client  │       aldabra-mcp (bin)     │  stdio
─────────►  │   tool handlers, lifecycle  │  ────►
            └──────────┬──────────────────┘
                       │
              ┌────────┼────────┐
              ▼        ▼        ▼
       ┌──────────┐ ┌──────┐ ┌─────────┐
       │  -core   │ │-chain│ │  -dao   │
       │ keys/sig │ │ Koios│ │ Agora/  │
       │          │ │      │ │ escrow  │
       └──────────┘ └──────┘ └─────────┘

Build

# Requires rustc 1.75+
cargo build --release

For the Plutus validators (escrow) you also need Aiken:

cd aiken-escrow
aiken build       # produces plutus.json blueprint

Run

# Smoke test (does nothing useful standalone — needs an MCP client)
./target/release/aldabra

# As an MCP server registered with Claude Code, add to ~/.claude.json:
#   "aldabra": {
#     "command": "/path/to/aldabra",
#     "env": {
#       "ALDABRA_DATA": "/path/to/wallet-data-dir",
#       "ALDABRA_NETWORK": "preprod",
#       "ALDABRA_KOIOS_BASE": "https://preprod.koios.rest/api/v1"
#     }
#   }

Bootstrap a wallet on first run by setting ALDABRA_BOOTSTRAP=new or ALDABRA_BOOTSTRAP=import in env — the binary prompts for a passphrase, generates or imports a mnemonic, and writes an age-encrypted mnemonic.age to ALDABRA_DATA.

Configuration

Environment variables consumed at startup:

Var Required Default Notes
ALDABRA_DATA yes Directory holding mnemonic.age. Must exist; bootstrap before first MCP run.
ALDABRA_NETWORK no preprod One of mainnet, preview, preprod.
ALDABRA_KOIOS_BASE no public Koios for the chosen network Override to point at a self-hosted Koios.
ALDABRA_PASSPHRASE yes Unlocks mnemonic.age. Source from a docker secret or systemd EnvironmentFile — never commit it.
ALDABRA_BOOTSTRAP no (unset) Set to new or import to enter bootstrap mode on next launch.
ALDABRA_MAX_SEND_LOVELACE no mainnet 10 ADA / preprod|preview 100 tADA Hard cap on lovelace flowing to any non-self destination. Enforced by every tool that signs or submits; pass force=true per-tool to override.
ALDABRA_SAFE_READS_ROOT no $ALDABRA_DATA/scripts/ Sandbox dir for the reference_script_path / policy_cbor_path tool args. Files outside this dir (canonical) are refused. Created with 0o700 at startup if missing.

MCP tools

The server exposes ~40 tools across four prefixes. A summary:

  • wallet_* — read (address/balance/utxos/network/stake_address), send (with optional inline datum for script locks), mint, Plutus script spending, stake delegation, Conway governance (vote delegation, DRep operations).
  • chain_* — read-only Koios passthroughs (tx info, address info, pool list/info, epoch params, asset info, account info, tip).
  • dao_* — Agora DAO client. Multi-DAO via config files. Live reads (governor state, stake list, my stake) plus the full write set: proposal create / cosign / vote / advance / retract-votes / stake-destroy.
  • escrow_* — two-party agreement-with-veto escrow. Build unsigned txs for open / deposit / agree / veto / settle / refund-timeout.

Every write tool produces an unsigned tx for the caller to sign + submit. No tool ever holds private keys outside the in-memory derived-key scope.

Security model

  • Mnemonic source: interactive bootstrap on first run, paste once or generate, encrypted at rest with age. Never written to disk in plaintext.
  • Derived keys: in-memory only, ZeroizeOnDrop on every container.
  • Network exposure: stdio MCP transport — the binary never opens a TCP listener. Only the spawning client process can talk to it.
  • Multi-network: safe to point at preprod for development; the same binary handles mainnet when you flip ALDABRA_NETWORK.

Status

Wallet + governance paths exercised on mainnet. DAO + escrow paths exercised end-to-end on preprod; the escrow validator has undergone internal review (audits/) but no third-party audit. Treat the escrow flows as use-at-own-risk until external review lands — see aiken-escrow/README.md for the WIP threat model.

License

See LICENSE.

Dependencies of note

  • txpipe/pallas — Rust Cardano primitives. Aldabra uses a fork on the feat-aux-data branch that adds auxiliary_data + voting_procedures support to pallas-txbuilder. PR upstream pending.
  • Aiken — Plutus V3 validator language used for the escrow contract.
  • modelcontextprotocol/rust-sdk (rmcp) — MCP server framework.
  • age — at-rest encryption.