1# `btcd`'s Reproducible Build System
2
3This package contains the build script that the `btcd` project uses in order to
4build binaries for each new release. As of `go1.13`, with some new build flags,
5binaries are now reproducible, allowing developers to build the binary on
6distinct machines, and end up with a byte-for-byte identical binary. However,
7this wasn't _fully_ solved in `go1.13`, as the build system still includes the
8directory the binary is built into the binary itself. As a result, our scripts
9utilize a work around needed until `go1.13.2`.
10
11## Building a New Release
12
13### macOS/Linux/Windows (WSL)
14
15No prior set up is needed on Linux or macOS is required in order to build the
16release binaries. However, on Windows, the only way to build the release
17binaries at the moment is by using the Windows Subsystem Linux. One can build
18the release binaries following these steps:
19
201. `git clone https://github.com/btcsuite/btcd.git`
212. `cd btcd`
223. `./build/release/release.sh <TAG> # <TAG> is the name of the next
23   release/tag`
24
25This will then create a directory of the form `btcd-<TAG>` containing archives
26of the release binaries for each supported operating system and architecture,
27and a manifest file containing the hash of each archive.
28
29## Verifying a Release
30
31With `go1.13`, it's now possible for third parties to verify release binaries.
32Before this version of `go`, one had to trust the release manager(s) to build the
33proper binary. With this new system, third parties can now _independently_ run
34the release process, and verify that all the hashes of the release binaries
35match exactly that of the release binaries produced by said third parties.
36
37To verify a release, one must obtain the following tools (many of these come
38installed by default in most Unix systems): `gpg`/`gpg2`, `shashum`, and
39`tar`/`unzip`.
40
41Once done, verifiers can proceed with the following steps:
42
431. Acquire the archive containing the release binaries for one's specific
44   operating system and architecture, and the manifest file along with its
45   signature.
462. Verify the signature of the manifest file with `gpg --verify
47   manifest-<TAG>.txt.sig`. This will require obtaining the PGP keys which
48   signed the manifest file, which are included in the release notes.
493. Recompute the `SHA256` hash of the archive with `shasum -a 256 <filename>`,
50   locate the corresponding one in the manifest file, and ensure they match
51   __exactly__.
52
53At this point, verifiers can use the release binaries acquired if they trust
54the integrity of the release manager(s). Otherwise, one can proceed with the
55guide to verify the release binaries were built properly by obtaining `shasum`
56and `go` (matching the same version used in the release):
57
584. Extract the release binaries contained within the archive, compute their
59   hashes as done above, and note them down.
605. Ensure `go` is installed, matching the same version as noted in the release
61   notes.
626. Obtain a copy of `btcd`'s source code with `git clone
63   https://github.com/btcsuite/btcd` and checkout the source code of the
64   release with `git checkout <TAG>`.
657. Proceed to verify the tag with `git verify-tag <TAG>` and compile the
66   binaries from source for the intended operating system and architecture with
67   `BTCDBUILDSYS=OS-ARCH ./build/release/release.sh <TAG>`.
688. Extract the archive found in the `btcd-<TAG>` directory created by the
69   release script and recompute the `SHA256` hash of the release binaries (btcd
70   and btcctl) with `shasum -a 256 <filename>`. These should match __exactly__
71   as the ones noted above.
72