From 008f1caf79eb21455ad0f1508251dc5320197f6d Mon Sep 17 00:00:00 2001 From: Phill Kelley <34226495+Paraphraser@users.noreply.github.com> Date: Thu, 29 Jun 2023 11:35:30 +1000 Subject: [PATCH] explain use of card URL field to obtain public key from keyserver Signed-off-by: Phill Kelley <34226495+Paraphraser@users.noreply.github.com> --- README.md | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) diff --git a/README.md b/README.md index 31ef283..d9feffd 100644 --- a/README.md +++ b/README.md @@ -1750,6 +1750,75 @@ If you need to set up a second host when you are travelling and don't have ready ``` console $ gpg --card-status ``` + +Another approach is to add the URL of your public key to your YubiKey: + +1. Define your KEYID. For example: + + ``` console + $ KEYID=0xFF3E7D88647EBCDB + ``` + +2. Construct the URL (based on [Shaw 2003](https://datatracker.ietf.org/doc/html/draft-shaw-openpgp-hkp-00)): + + ``` + $ [[ ! "$KEYID" =~ ^"0x" ]] && KEYID="0x${KEYID}" + $ URL="hkps://keyserver.ubuntu.com:443/pks/lookup?op=get&search=${KEYID}" + $ echo $URL + hkps://keyserver.ubuntu.com:443/pks/lookup?op=get&search=0xFF3E7D88647EBCDB + ``` + +3. Insert your YubiKey into a USB port. +4. Add the URL to your YubiKey (will prompt for your YubiKey's admin PIN): + + ``` + $ gpg --edit-card + gpg/card> admin + gpg/card> url + URL to retrieve public key: hkps://keyserver.ubuntu.com:443/pks/lookup?op=get&search=0xFF3E7D88647EBCDB + gpg/card> quit + ``` + + Note: + + * You do not have to use a *keyserver* URL. You can export your public key as an armored ASCII file and upload it to any place on the web where it can be downloaded using HTTP/HTTPS. + +Once the URL of your public key is present on your YubiKey, setting up a new host becomes: + +1. Insert your YubiKey into a USB port. + +2. Use the `fetch` sub-command to retrieve your public key using the URL stored on the card: + + ``` + $ gpg --edit-card + + gpg/card> fetch + gpg: requesting key from 'hkps://keyserver.ubuntu.com:443/pks/lookup?op=get&search=0xFF3E7D88647EBCDB' + gpg: /home/pi/.gnupg/trustdb.gpg: trustdb created + gpg: key FF3E7D88647EBCDB: public key "Dr Duh " imported + gpg: Total number processed: 1 + gpg: imported: 1 + + gpg/card> quit + ``` + + This step also imports the private key stubs from the YubiKey. + +3. Define your KEYID (which appears in the output in the previous step): + + ``` console + $ export KEYID=0xFF3E7D88647EBCDB + ``` + +4. Set ultimate trust: + + ``` console + $ gpg --edit-key $KEYID + gpg> trust + Your decision? 5 + Do you really want to set this key to ultimate trust? (y/N) y + gpg> quit + ``` # Cleanup