+# generate a subkey with the 'a' usage flags set
+# FIXME: this needs some tweaking to clean it up
+gen_subkey(){
+ local keyID
+ local gpgOut
+ local userID
+
+ keyID="$1"
+
+ gpgOut=$(gpg --quiet --fixed-list-mode --list-keys --with-colons \
+ "$keyID" 2> /dev/null)
+
+ # fail if there only "tru" lines are output from gpg, which
+ # indicates the key was not found.
+ if [ -z "$(echo "$gpgOut" | grep -v '^tru:')" ] ; then
+ failure "Key ID '$keyID' not found."
+ fi
+
+ # fail if multiple pub lines are returned, which means the id given
+ # is not unique
+ if [ $(echo "$gpgOut" | grep '^pub:' | wc -l) -gt '1' ] ; then
+ failure "Key ID '$keyID' is not unique."
+ fi
+
+ # prompt if an authentication subkey already exists
+ if echo "$gpgOut" | egrep "^(pub|sub):" | cut -d: -f 12 | grep -q a ; then
+ echo "An authentication subkey already exists for key '$keyID'."
+ read -p "Are you sure you would like to generate another one? (y/N) " OK; OK=${OK:N}
+ if [ "${OK/y/Y}" != 'Y' ] ; then
+ failure "aborting."
+ fi
+ fi
+
+ # set subkey defaults
+ KEY_TYPE="RSA"
+ KEY_LENGTH=${KEY_LENGTH:-}
+ KEY_USAGE="auth"
+ # prompt about key expiration if not specified
+ if [ -z "$KEY_EXPIRE" ] ; then
+ cat <<EOF
+Please specify how long the key should be valid.
+ 0 = key does not expire
+ <n> = key expires in n days
+ <n>w = key expires in n weeks
+ <n>m = key expires in n months
+ <n>y = key expires in n years
+EOF
+ while [ -z "$KEY_EXPIRE" ] ; do
+ read -p "Key is valid for? (0) " KEY_EXPIRE
+ if ! test_gpg_expire ${KEY_EXPIRE:=0} ; then
+ echo "invalid value"
+ unset KEY_EXPIRE
+ fi
+ done
+ elif ! test_gpg_expire "$KEY_EXPIRE" ; then
+ failure "invalid key expiration value '$KEY_EXPIRE'."
+ fi
+
+ # generate the list of commands that will be passed to edit-key
+ editCommands=$(cat <<EOF
+addkey
+7
+S
+E
+A
+Q
+$KEY_LENGTH
+$KEY_EXPIRE
+save
+EOF
+)
+
+ log "generating subkey..."
+ echo "$editCommands" | gpg --expert --command-fd 0 --edit-key "$keyID"
+ log "done."
+}
+