litetlog

README

litetlog

The litetlog repository is a collection of open-source tooling for transparency logs designed to be simple and lightweight.

litewitness

litewitness is a synchronous low-latency cosigning witness. (A witness is a service that accepts a new signed tree head, checks its consistency with the previous latest tree head, and returns a signature over it.) It implements the c2sp.org/tlog-witness protocol.

It's backed by a SQLite database for storage, and by an ssh-agent for private key operations.

To install it, use go install.

# from anywhere
go install filippo.io/litetlog/cmd/{litewitness,witnessctl}@latest

# from within a source tree
go install filippo.io/litetlog/cmd/{litewitness,witnessctl}

litewitness has no config file. All configuration is done via command line flags or witnessctl (see below).

-db string
        path to sqlite database (default "litewitness.db")

The SQLite database is where known trees and tree heads are stored. It needs to be on a filesystem that supports locking (not a network file system). It will be created if it does not exist.

-name string
        URL-like (e.g. example.com/foo) name of this witness

The name of the witness is a URL-like value that will appear in cosignature lines. It does not need to be where the witness is reachable but should be recognizable.

-key string
        hex-encoded SHA-256 hash of the witness key
-ssh-agent string
        path to ssh-agent socket (default "litewitness.sock")

The witness Ed25519 private key is provided by a ssh-agent instance. The socket is specified explicitly because it's recommended that a dedicated instance is run for litewitness. The use of the ssh-agent protocol allows the key to be provided by a key file, a PKCS#11 module, or custom hardware agents.

Example of starting a dedicated ssh-agent and loading a key:

ssh-agent -a litewitness.sock
SSH_AUTH_SOCK=litewitness.sock ssh-add litewitness.pem

-bastion string
        address of the bastion(s) to reverse proxy through, comma separated, the first online one is selected
-listen string
        address to listen for HTTP requests (default "localhost:7380")

Only one of -bastion or -listen must be specified. The former will cause litewitness to serve requests through a bastion reverse proxy (see below). The latter will listen for HTTP requests on the specified port. (HTTPS needs to be terminated outside of litewitness.) The bastion flag is an optionally comma-separated list of bastions to try in order until one connects successfully. If the connection drops after establishing, litewitness exits.

witnessctl

witnessctl is a CLI tool to operate on the litewitness database. It can be used while litewitness is running.

witnessctl add-log -db <path> -origin <origin> -key <base64-encoded Ed25519 key>
witnessctl add-sigsum-log -db <path> -key <hex-encoded key>

The add-log and add-sigsum-log commands add a new known log starting at a size of zero.

witnessctl list-logs -db <path>

The list-logs command lists known logs, in JSON lines like the following.

{"origin":"sigsum.org/v1/tree/4d6d8825a6bb689d459628312889dfbb0bcd41b5211d9e1ce768b0ff0309e562","size":5,"root_hash":"QrtXrQZCCvpIgsSmOsah7HdICzMLLyDfxToMql9WTjY=","keys":["sigsum.org/v1/tree/4d6d8825a6bb689d459628312889dfbb0bcd41b5211d9e1ce768b0ff0309e562+5202289b+Af/cLU2Y5BJNP+r3iMDC+av9eWCD0fBJVDfzAux5zxAP"]}

litebastion

litebastion is a public-service reverse proxy for witnesses that can't be exposed directly to the internet.

In short, a witness connects to a bastion over TLS with a Ed25519 client certificate, "reverses" the direction of the connection, and serves HTTP/2 requests over that connection. The bastion then proxies requests received at /<hex-encoded hash of Ed25519 key>/* to that witness.

-backends string
        file of accepted key hashes, one per line, reloaded on SIGHUP

The only configuration file of litebastion is the backends file, which lists the acceptable client/witness key hashes.

-listen string
        host and port to listen at (default "localhost:8443")
-cache string
        directory to cache ACME certificates at
-email string
        email address to register the ACME account with
-host string
        host to obtain ACME certificate for

Since litebastion needs to operate at a lower level than HTTPS on the witness side, it can't be behind a reverse proxy, and needs to configure its own TLS certificate. Use the -cache, -email, and -host flags to configure the ACME client. The ALPN ACME challenge is used, so as long as the -listen port receives connections to the -host name at port 443, everything should just work.

bastion as a library

It might be desirable to integrate bastion functionality in an existing binary, for example because there is only one IP address and hence only one port 443 to listen on.

In that case, you can use the filippo.io/litetlog/bastion package.

See pkg.go.dev for the documentation and in particular the package example.