smimesign: macOS Big Sur: smimesign v0.1.0: Invalid Signatures

smimesign v0.1.0 when installed via Homebrew for macOS Big Sur creates invalid/corrupt signatures. Specifically, this happens when smimesign is installed as follows on macOS Big Sur:

brew install smimesign

This causes the following bottle to be used: https://homebrew.bintray.com/bottles/smimesign-0.1.0.big_sur.bottle.tar.gz

Interestingly enough, these invalid signatures (signatures created with the smimesign binary for macOS Big Sur) can be verified successfully by the same smimesign binary that created them, but are (correctly) reported as invalid by all other smimesign binaries as well as the GitHub UI/API.

To workaround this issue, when installing smimesign on macOS Big Sur, you can explicitly request a bottle that does not suffer from this issue. Specifically, the smimesign-0.1.0.catalina.bottle.tar.gz bottle (compiled for macOS Catalina) does not suffer from the issue and works on macOS BigSur:

brew install https://homebrew.bintray.com/bottles/smimesign-0.1.0.catalina.bottle.tar.gz

If this workaround is not performed, corrupt git commit signatures will be produced. Any attempt to verify these commits using a version of smimesign that does not suffer from the issue will result in the following failure:

[~/dev/test-repo]$ git log --show-signature -1
commit 982cca63826ab8e894fc48db2825dd7805d1f9ae (HEAD -> master, origin/master, origin/HEAD)
failed to verify signature: crypto/rsa: verification error
Merge: 59b2361 26ce50c
Author: Redacted User <redacted@redacted.com>
Date:   Fri Sep 18 19:07:50 2020 -0400

    #1: Test Issue
[~/dev/test-repo]$ git verify-commit HEAD
failed to verify signature: crypto/rsa: verification error