revoke_key() {
-# FIXME: implement!
-failure "not implemented yet!"
+# Coming in here, we expect $HOST_FINGERPRINT to be set, and we
+# believe that there is in fact a key.
+ if [ "$PROMPT" = "false" ] ; then
+ publish=N
+ else
+ cat <<EOF >&2
+This will generate a revocation certificate for your host key
+(fingerprint: $HOST_FINGERPRINT) and
+dump the certificate to standard output.
+
+It can also directly publish the new revocation certificate
+to the public keyservers via $KEYSERVER if you want it to.
+
+Publishing this certificate will IMMEDIATELY and PERMANENTLY revoke
+your host key!
+
+EOF
+ read -p "Publish the certificate after generation? (y/n/Q) " publish
+
+ if ! [ "${publish/y/Y}" = 'Y' -o "${publish/n/N}" = 'N' ] ; then
+ failure "aborting at user request"
+ fi
+ fi
+
+ # our current implementation is very simple: we just want to
+ # generate the revocation certificate on stdout. This provides
+ # for the two most likely (but hopefully not common) scenarios:
+
+ # an admin wants a revocation certificate for the host which they
+ # can store securely offline. In this case, the admin can
+ # redirect stdout to a file, or can simply copy/paste or
+ # transcribe from the terminal.
+
+ # Alternately, an admin might want to publish the revocation
+ # certificate immediately, which we can help them do as well.
+
+ if [ "$PROMPT" = 'false' ] ; then
+ # FIXME: allow the end user to choose something other than
+ # "key was compromised" (1) and to supply their own revocation
+ # string.
+
+ local revoke_commands="y
+1
+Monkeysphere host key revocation (automated) $(date '+%F_%T%z')
+
+y
+
+"
+ revcert=$(GNUPGHOME="$GNUPGHOME_HOST" gpg_host --command-fd 0 --armor --gen-revoke "0x${HOST_FINGERPRINT}!" <<<"$revoke_commands" ) \
+ || failure "Failed to generate revocation certificate!"
+
+
+ else
+ # note: we're not using the gpg_host function because we actually
+ # want to use gpg's UI in this case, so we want to omit --no-tty
+ revcert=$(GNUPGHOME="$GNUPGHOME_HOST" gpg --no-greeting --quiet --armor --gen-revoke "0x${HOST_FINGERPRINT}!") \
+ || failure "Failed to generate revocation certificate!"
+ fi
+
+ # if you run gpg --gen-revoke but cancel it or quit in the middle,
+ # it returns success, but emits no revocation certificate:
+ if ! [ "$revcert" ] ; then
+ failure "Revocation canceled."
+ fi
+
+ ## ok, now we have the revocation certificate. Print it, and
+ ## offer to publish if originally requested:
+ printf "%s\n" "$revcert"
+
+ if [ "${publish/y/Y}" = 'Y' ] ; then
+ printf "\n" >&2
+ read -p "Really publish this cert to $KEYSERVER ? (Y/n) " really
+ if [ "${really/n/N}" = 'N' ] ; then
+ printf "Not publishing.\n" >&2
+ else
+ local newhome=$(mkmstempdir)
+ GNUPGHOME="$newhome" gpg --no-tty --quiet --import < "$HOST_KEY_FILE"
+ GNUPGHOME="$newhome" gpg --no-tty --quiet --import <<< "$revcert"
+ GNUPGHOME="$newhome" gpg --keyserver "$KEYSERVER" --send "0x${HOST_FINGERPRINT}!"
+ rm -rf "$newhome"
+ fi
+ fi
}