levain 0.10.2

A security fix. Upgrade if Levain runs bash on Linux where you use gpg, or if you use the cockpit's signing keys.

Security

• On Linux, gnupg's configuration files are now read-only to the entity in a gnupg home where Levain finds a running dirmngr. 0.9.1 made gpg-agent.conf and gnupg's other configuration files read-only to bash in ~/.gnupg, and in $GNUPGHOME when Levain's own environment sets it. That did not cover a gnupg home outside both that holds a dirmngr started where /run/user/<uid> did not exist, such as from cron or before linger. In 0.10.0, bash without network gets a fresh view of such a home, and that view bound the home's files back writable, next to the socket of the gpg-agent that reads them. A bash session could therefore get your gpg-agent to run a program of its choosing outside the floor. In that home those files are now read-only to bash, with or without network, and to the file editor. A configuration file that is a symlink comes back as its file's content, read-only. One that leads into a directory the floor denies, or leads nowhere, is left out. If bash has network and such a configuration file is a symlink that leads nowhere, bash is refused, as it has been in ~/.gnupg since 0.9.1. Found in Levain's own review, reproduced in the floor's plan, and checked on Linux by running bash under bubblewrap.
• Still open, as 0.9.1 stated: a gnupg home that Levain is not told about, and where it finds no dirmngr, keeps writable configuration files, on Linux and macOS. That closes before Levain 2.0.
• The cockpit's signing keys are now behind the floor. levain cockpit key create puts the keys that sign T2 and T3 writes in <levain home>/keys (~/.levain/keys), and 0.10.0 did not deny that directory to bash or the file editor. A bash session could copy a passphrase-protected key and guess the passphrase offline. It could also replace a new key between key create and enroll, so the touch you gave to enrol it enrolled a key bash chose. The directory is now denied, read and write, like ~/.ssh. Known edges: a directory you pick with key create --dir is not covered, and enroll still accepts the new key's public half without a signature from that key, so a program running as you outside Levain can make the same swap. The README's passphrase custody already says it is no defence against such a program.
• A FIDO key now needs a touch for a cockpit write, as it already did for an authority link. OpenSSH's signature check does not enforce the touch itself. A key made with no-touch-required had its authority links refused but could sign a T2 or T3 write without a touch. Both checks now use one rule.