#!/bin/bash

# script to migrate fully from pubring.gpg to pubring.kbx

# Author: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
# Date: 2016-04-01
# License: GPLv3+

# This was written for the Debian project

set -e

GPG="${GPG:-gpg}"

# select the default GnuPG home directory to work from:
GHD=${GNUPGHOME:-${HOME:-$(getent passwd "$(id -u)" | cut -f6 -d:)}/.gnupg}

# Check that this is gnupg 2.1 or 2.2:
VERSION=$("$GPG" --version | head -n1 | cut -f3 -d\  | cut -f1,2 -d.)
if [ "$VERSION" != 2.1 ] && [ "$VERSION" != 2.2 ] ; then
    printf '%s is version %s not version 2.1 or 2.2, this script might be wrong\n' "$GPG" "$VERSION" >&2
    exit 1
fi    

usage() {
    printf 'Usage: %s [GPGHOMEDIR|--default]
\tMigrate public keyring in GPGHOMEDIR from "classic" to "modern" GnuPG
\tusing %s version %s.

\t--default migrates the GnuPG home directory at "%s"
' "$0" "$GPG" "$VERSION" "$GHD"
}

if [ -z "$1" ]; then
    usage >&2
    exit 1
else
    case "$1" in
        --help|--usage|-h)
            usage
            exit
            ;;
        --default)
            ;;
        *)
            GHD="$1"
            ;;
    esac
fi

GPG=("$GPG" --homedir "$GHD" --batch)

# ensure that there is a pubring.gpg to migrate:
if ! [ -f "$GHD/pubring.gpg" ]; then
    printf 'There is no %s/pubring.gpg, no need to migrate\n' "$GHD" >&2
    exit
fi
if ! [ -s "$GHD/pubring.gpg" ]; then
    mv -- "$GHD/pubring.gpg" "$GHD/pubring.gpg.empty"
    printf '%s/pubring.gpg was empty (and has been moved out of the way), no need to migrate\n' "$GHD" >&2
    exit
fi

BACKUP="$(mktemp -d "$GHD/migrate-from-classic-backup.$(date +%F).XXXXXX")"
printf 'Migrating from:\n%s\n[Backing up to %s]\n' "$(ls -l "$GHD/pubring.gpg")" "$BACKUP" >&2

"${GPG[@]}" --export-ownertrust > "$BACKUP/ownertrust.txt"
mv "$GHD/pubring.gpg" "$BACKUP/"

revert() {
    printf >&2 'Restoring pubring.gpg...\n'
    cp "$BACKUP/pubring.gpg" "$GHD/pubring.gpg"
}

trap revert EXIT

if ! "${GPG[@]}" --status-file "$BACKUP/import-status" --import-options import-local-sigs,keep-ownertrust,repair-pks-subkey-bug --import < "$BACKUP/pubring.gpg" ; then
    cat >&2 <<EOF
Keyring import was not completely successful (see error message above,
and the LIMITATIONS section of migrate-pubring-from-classic-gpg(1) for
more details).

If you suspect a bug in the migration script, please use:

    reportbug gnupg-utils --subject='migrate-pubring-from-classic-gpg partial failure'

And include the above output (redacted for privacy as needed) in the
body of the report.

Continuing with the rest of the migration anyway...
EOF
fi
"${GPG[@]}" --import-ownertrust < "$BACKUP/ownertrust.txt"
"${GPG[@]}" --check-trustdb

if ! [ -f "$GHD/pubring.kbx" ]; then
    cat >&2 <<EOF
No keybox was created at $GHD/pubring.kbx.  Something went wrong!

Please report a bug in the migration script, using:

    reportbug gnupg-utils --subject='migrate-pubring-from-classic-gpg no pubring.kbx ($BACKUP)'
EOF
    exit 1
fi
trap - EXIT

printf 'Migration completed successfully:\n%s\n' "$(ls -l "$GHD/pubring.kbx")" >&2