docs+scripts: switch to detached signatures

Due to a misunderstanding of how the gpg command line options work, we
didn't actually create detached signatures because the --clear-sign
flag would overwrite that. We update our verification script to now only
download the detached signatures and verify them against the main
manifest file.
We also update the signing instructions.

2021-02-15 10:33:20 +01:00

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`lnd`'s Reproducible Build System

This package contains the build script that the lnd project uses in order to build binaries for each new release. As of go1.13, with some new build flags, binaries are now reproducible, allowing developers to build the binary on distinct machines, and end up with a byte-for-byte identical binary. However, this wasn't fully solved in go1.13, as the build system still includes the directory the binary is built into the binary itself. As a result, our scripts utilize a work around needed until go1.13.2.

Building a New Release

MacOS

The first requirement is to have docker installed locally and running. The second requirement is to have make installed. Everything else (including golang) is included in the release helper image.

To build a release, run the following commands:

⛰  git clone https://github.com/lightningnetwork/lnd.git
⛰  cd lnd
⛰  git checkout <TAG> # <TAG> is the name of the next release/tag
⛰  make docker-release tag=<TAG>

Where <TAG> is the name of the next release of lnd.

Linux/Windows (WSL)

No prior set up is needed on Linux or macOS is required in order to build the release binaries. However, on Windows, the only way to build the release binaries at the moment is by using the Windows Subsystem Linux. One can build the release binaries following these steps:

⛰  git clone https://github.com/lightningnetwork/lnd.git
⛰  cd lnd
⛰  git checkout <TAG> # <TAG> is the name of the next release/tag
⛰  make release tag=<TAG>

This will then create a directory of the form lnd-<TAG> containing archives of the release binaries for each supported operating system and architecture, and a manifest file containing the hash of each archive.

Verifying a Release

With go1.13, it's now possible for third parties to verify release binaries. Before this version of go, one had to trust the release manager(s) to build the proper binary. With this new system, third parties can now independently run the release process, and verify that all the hashes of the release binaries match exactly that of the release binaries produced by said third parties.

To verify a release, one must obtain the following tools (many of these come installed by default in most Unix systems): gpg/gpg2, shashum, and tar/unzip.

Once done, verifiers can proceed with the following steps:

Acquire the archive containing the release binaries for one's specific operating system and architecture, and the manifest file along with its signature.
Verify the signature of the manifest file with gpg --verify manifest-<TAG>.txt.sig. This will require obtaining the PGP keys which signed the manifest file, which are included in the release notes.
Recompute the SHA256 hash of the archive with shasum -a 256 <filename>, locate the corresponding one in the manifest file, and ensure they match exactly.

At this point, verifiers can use the release binaries acquired if they trust the integrity of the release manager(s). Otherwise, one can proceed with the guide to verify the release binaries were built properly by obtaining shasum and go (matching the same version used in the release):

Extract the release binaries contained within the archive, compute their hashes as done above, and note them down.
Ensure go is installed, matching the same version as noted in the release notes.
Obtain a copy of lnd's source code with git clone https://github.com/lightningnetwork/lnd and checkout the source code of the release with git checkout <TAG>.
Proceed to verify the tag with git verify-tag <TAG> and compile the binaries from source for the intended operating system and architecture with make release sys=OS-ARCH tag=<TAG>.
Extract the archive found in the lnd-<TAG> directory created by the release script and recompute the SHA256 hash of the release binaries (lnd and lncli) with shasum -a 256 <filename>. These should match exactly as the ones noted above.

Verifying Docker Images

To verify the lnd and lncli binaries inside the official provided docker images against the signed, reproducible release binaries, there is a verification script in the image that can be called (before starting the container for example):

⛰  docker pull lightninglabs/lnd:v0.12.0-beta
⛰  docker run --rm --entrypoint="" lightninglabs/lnd:v0.12.0-beta /verify-install.sh
⛰  OK=$?
⛰  if [ "$OK" -ne "0" ]; then echo "Verification failed!"; exit 1; done
⛰  docker run lightninglabs/lnd [command-line options]

Signing an Existing Manifest File

If you're a developer of lnd and are interested in attaching your signature to the final release archive, the manifest MUST be signed in a manner that allows your signature to be verified by our verify script scripts/verify-install.sh.

Assuming you've done a local build for all release targets, then you should have a file called manifest-TAG.txt where TAG is the actual release tag description being signed. The release script expects a particular file name for each included signature, so we'll need to modify the name of our output signature during signing.

Assuming USERNAME is your current nick as a developer, then the following command will generate a proper signature:

⛰  gpg --detach-sig --output manifest-USERNAME-TAG.sig manifest-TAG.txt

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lnd's Reproducible Build System