Tendermint KMS 🔐

Key Management System for Tendermint applications, initially targeting Cosmos Validators.

About

This repository contains tmkms, a key management service intended to be deployed in conjunction with Tendermint applications (ideally on separate physical hosts) which provides the following:

• High-availability access to validator signing keys
• Double-signing prevention even in the event the validator process is compromised
• Hardware security module storage for validator keys which can survive host compromise

Status

Tendermint KMS is currently beta quality. It has undergone one security audit with only one low-severity finding.

Double Signing / High Availability

Tendermint KMS implements beta quality double signing detection. It has undergone some testing, however we do not (yet) recommend using the KMS in conjunction with multiple simultaneously active validators on the same network for prolonged periods of time.

In particular, there is presently no double signing defense in the case that multiple KMS instances are running simultaneously and connecting to multiple validators on the same network.

The longer-term story around double-signing is more complex, as it includes such scenarios as signing while unbonded. For more information on future-plans to provide double-signing defense and high availability in such scenarios, see #115: Improving double-signing prevention.

Signing Providers

You MUST select one or more signing provider(s) when compiling the KMS, passed as the argument to the --features flag (see below for more instructions on how to build Tendermint KMS).

The following signing backend providers are presently supported:

Hardware Security Modules (recommended)

• YubiHSM2 (gated under the yubihsm cargo feature. See README.yubihsm.md for more info)
• Ledger (gated under the ledgertm cargo feature)

Software-Only (not recommended)

• softsign backend which uses ed25519-dalek

Supported Platforms

tmkms should build on any supported Rust platform which is also supported by libusb, however there are some platforms which meet those criteria which are unsuitable for cryptography purposes due to lack of constant-time CPU instructions. Below are some of the available tier 1, 2, and 3 Rust platforms which meet our minimum criteria for KMS use.

NOTE: tmkms is presently tested on Linux/x86_64. We don't otherwise guarantee support for any of the platforms below, but they theoretically meet the necessary prerequisites for support.

Operating Systems

• Linux (recommended)
• FreeBSD
• NetBSD
• OpenBSD
• macOS

CPU Architectures

• x86_64 (recommended)
• arm (32-bit ARM)
• aarch64 (64-bit ARM)
• riscv32 (32-bit RISC-V)
• riscv64 (64-bit RISC-V)

Installation

You will need the following prerequisites:

• Rust (stable; 1.35+): https://rustup.rs/
• C compiler: e.g. gcc, clang
• pkg-config
• libusb (1.0+). Install instructions for common platforms:
  • Debian/Ubuntu: apt install libusb-1.0-0-dev
  • RedHat/CentOS: yum install libusb1-devel
  • macOS (Homebrew): brew install libusb

NOTE (x86_64 only): Configure RUSTFLAGS environment variable: export RUSTFLAGS=-Ctarget-feature=+aes,+ssse3

There are two ways to install tmkms: either compiling the source code after cloning it from git, or using Rust's cargo install command.

Compiling from source code (via git)

tmkms can be compiled directly from the git repository source code using the following method.

The following example adds --features=yubihsm to enable YubiHSM 2 support.

$ git clone https://github.com/tendermint/kms.git && cd kms
[...]
$ cargo build --release --features=yubihsm

Alternatively, substitute --features=ledgertm to enable Ledger support.

If successful, this will produce a tmkms executable located at ./target/release/tmkms

Installing with the cargo install command

With Rust (1.35+) installed, you can install tmkms with the following:

cargo install tmkms --features=yubihsm

Or to install a specific version (recommended):

cargo install tmkms --features=yubihsm --version=0.4.0

Alternatively, substitute --features=ledgertm to enable Ledger support.

Usage

After compiling, start tmkms with the following:

$ tmkms start

This will read the configuration from the tmkms.toml file in the current working directory.

To explicitly specify the path to the configuration, use the -c flag:

$ tmkms start -c /path/to/tmkms.toml

Development

The following are instructions for setting up a development environment. They assume you've already followed steps 1 & 2 from the Installation section above.

• Install rustfmt: rustup component add rustfmt
• Install clippy: rustup component add clippy

Alternatively, you can build a Docker image from the Dockerfile in the top level of the repository, which is what is used to run tests in CI.

Before opening a pull request, please run the checks below:

Testing

Run the test suite with:

cargo test --all-features

Format checking (rustfmt)

Make sure your code is well-formatted by running:

cargo fmt

Lint (clippy)

Lint your code (i.e. check it for common issues) with:

cargo clippy

License

Copyright © 2018-2019 Tendermint

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.