all: remove concept of read-write key

We don't need a read-write key: we can just SSH directly to
jim-backups@backup.jim.sh instead and run commands thay way.
Remove read-write key and document it in the README.

Also add some tools to update the README variables on updates.

Makefile

@@ -38,7 +38,9 @@ rebase:
 	git pull
 	git checkout -
 	git rebase master
+	./initial-setup.sh --update-paths
 	systemctl daemon-reload
+	git status
 
 # Show status of most recent backup run
 .PHONY: status

README.md

@@ -16,14 +16,14 @@ Cheat sheet
 *After setup, the copy of this file on the client will have the
 variables in this section filled in automatically*
 
-### Configuration
+## Configuration
 
     Hostname: ${HOSTNAME}
     Base directory: ${BORG_DIR}
     Destination: ${BACKUP_USER}@${BACKUP_HOST}
     Repository: ${BACKUP_REPO}
 
-### Commands
+## Commands
 
 See when next backup is scheduled:
 
@@ -61,12 +61,25 @@ Mount and look at files:
     sudo -s # to explore as root
     sudo umount mnt
 
-Prune old backups.  Only run if sure local system was never compromised,
-as object deletion could have been queued during append-only operations.
-Requires SSH key password from bitwarden.
 
-    sudo ${BORG_DIR}/prune.sh
+## Compaction and remote access
 
+Old backups are "pruned" automatically, but because the SSH key is
+append-only, no space is actually recovered on the server, it's just
+marked for deletion.  If you are sure that the client system was not
+compromised, then you can run compaction manually directly on the
+backup host by logging in via SSH (bitwarden `ssh ${BACKUP_HOST} /
+${BACKUP_USER}`) and compacting there:
+
+    ssh ${BACKUP_USER}@${BACKUP_HOST} borg/borg compact --verbose --progress ${BACKUP_REPO}
+
+This doesn't require the repo key.  It shouldn't be entered on the untrusted
+backup host, so for operations that need it, use a trusted host and run borg
+remotely instead, e.g.:
+
+    ${BORG_DIR}/Borg.bin --remote-path borg/borg info ${BACKUP_USER}@${BACKUP_HOST}:borg/${HOSTNAME}
+
+The repo passphrase is in bitwarden `borg ${HOSTNAME}/ repo key`.
 
 
 Design
@@ -81,20 +94,13 @@ Design
   - on clients (in `/opt/borg/passphrase`, for making backups)
   - in bitwarden (under `borg <hostname>`, user `repo key`)
 
-- Each client has two SSH keys for connecting to the server:
+- Each client has two passwordless SSH keys for connecting to the server:
   - `/opt/borg/ssh/id_ecdsa_appendonly`
     - configured on server for append-only operation
     - used for making backups
-    - no password
-  - `/opt/borg/ssh/id_ecdsa`
-    - configured on server for read-write operation
-    - used for manual recovery, management, pruning
-    - password in bitwarden (under `borg <hostname>`, user `read-write ssh key`)
-
-- Pruning requires the password and is a manual operation, and should only
-  be run when the client has not been compromised.
-
-      sudo /opt/borg/prune.sh
+  - `/opt/borg/ssh/id_ecdsa_notify`
+    - configured on server for running `borg/notify.sh` only
+    - used for sending email notifications on errors
 
 - Systemd timers start daily backups:
 
@@ -103,9 +109,7 @@ Design
 
 - Backup script `/opt/borg/backup.py` uses configuration in
   `/opt/borg/config.yaml` to generate our own list of files, excluding
-  anything that's too large by default.  This requires borg 1.2.0b1
-  or newer.
-
+  anything that's too large by default.  This requires borg 1.2 or newer.
 
 
 Notes

borg.sh

@@ -7,15 +7,6 @@ export BORG_PASSCOMMAND="cat ${BORG_DIR}/passphrase"
 export BORG_BASE_DIR=${BORG_DIR}
 export BORG_CACHE_DIR=${BORG_DIR}/cache
 export BORG_CONFIG_DIR=${BORG_DIR}/config
-if [ "$1" = "--rw" ] ; then
-    if [ "$BORG_RW_KEY_ADDED" != "1" ] ; then
-        echo "=== Need SSH key passphrase.  Check Bitwarden for:"
-        echo "===   borg $HOSTNAME / read-write SSH key"
-    fi
-    export BORG_RSH="ssh -F $SSH/config -o BatchMode=no -o PreferredAuthentications=publickey -i $SSH/id_ecdsa"
-    shift
-else
-    export BORG_RSH="ssh -F $SSH/config -i $SSH/id_ecdsa_appendonly"
-fi
+export BORG_RSH="ssh -F $SSH/config -i $SSH/id_ecdsa_appendonly"
 
 exec "${BORG_BIN}" "$@"

initial-setup.sh

@@ -27,8 +27,34 @@ trap 'error_handler ${BASH_SOURCE} ${LINENO} $?' ERR
 set -o errexit
 set -o errtrace
 
-if [ -e ".setup-complete" ]; then
-    echo "Error: BORG_DIR $BORG_DIR was already set up; giving up."
+update_paths()
+{
+    sed -i \
+        -e "s!\${HOSTNAME}!${HOSTNAME}!g" \
+        -e "s!\${BORG_DIR}!${BORG_DIR}!g" \
+        -e "s!\${BACKUP_USER}!${BACKUP_USER}!g" \
+        -e "s!\${BACKUP_HOST}!${BACKUP_HOST}!g" \
+        -e "s!\${BACKUP_REPO}!${BACKUP_REPO}!g" \
+        README.md
+
+    sed -i\
+        -e "1c#!${BORG_DIR}/.venv/bin/python" \
+        backup.py
+}
+
+if [ "$1" == "--update-paths" ] ; then
+    if [ -e "vars.sh" ]; then
+        echo "Updating paths"
+        update_paths
+        exit 0
+    else
+        echo "Can't update paths, not set up yet"
+        exit 1
+    fi
+fi
+
+if [ -e "vars.sh" ]; then
+    echo "Error: BORG_DIR $BORG_DIR already looks set up; giving up."
     echo "Use \"git clean\" to return it to original state if desired"
     exit 1
 fi
@@ -113,7 +139,6 @@ print_random_key()
 
 generate_keys()
 {
-    PASS_SSH=$(print_random_key)
     PASS_REPOKEY=$(print_random_key)
     echo "$PASS_REPOKEY" > passphrase
     chmod 600 passphrase
@@ -136,8 +161,6 @@ configure_ssh()
                -C "backup-appendonly@$HOSTID" -f "$SSH/id_ecdsa_appendonly"
     ssh-keygen -N "" -t ecdsa \
                -C "backup-notify@$HOSTID" -f "$SSH/id_ecdsa_notify"
-    ssh-keygen -N "$PASS_SSH" -t ecdsa \
-               -C "backup@$HOSTID" -f "$SSH/id_ecdsa"
 
     # Create config snippets
     log "Creating SSH config and wrapper script"
@@ -184,7 +207,6 @@ EOF
     run_ssh_command "cat >> .ssh/authorized_keys" <<EOF
 command="$cmd --append-only",restrict $(cat "$SSH/id_ecdsa_appendonly.pub")
 command="borg/notify.sh",restrict $(cat "$SSH/id_ecdsa_notify.pub")
-command="$cmd",restrict $(cat "$SSH/id_ecdsa.pub")
 EOF
 
     # Test that everything worked
@@ -281,21 +303,6 @@ EOF
     fi
 }
 
-update_paths()
-{
-    sed -i \
-        -e "s!\${HOSTNAME}!${HOSTNAME}!g" \
-        -e "s!\${BORG_DIR}!${BORG_DIR}!g" \
-        -e "s!\${BACKUP_USER}!${BACKUP_USER}!g" \
-        -e "s!\${BACKUP_HOST}!${BACKUP_HOST}!g" \
-        -e "s!\${BACKUP_REPO}!${BACKUP_REPO}!g" \
-        README.md
-
-    sed -i\
-        -e "1c#!${BORG_DIR}/.venv/bin/python" \
-        backup.py
-}
-
 git_setup()
 {
     if ! git checkout -b "setup-${HOSTNAME}" ; then
@@ -324,11 +331,7 @@ update_paths
 git_setup
 
 echo
-notice "Add these two passwords to Bitwarden:"
-notice ""
-notice "      Name: borg ${HOSTNAME}"
-notice "  Username: read-write ssh key"
-notice "  Password: $PASS_SSH"
+notice "Add this password to Bitwarden:"
 notice ""
 notice "      Name: borg ${HOSTNAME}"
 notice "  Username: repo key"

prune.sh

@@ -1,26 +0,0 @@
-#!/bin/bash
-
-set -e
-. "$(dirname "$0")"/vars.sh
-
-if [ "$BORG_RW_KEY_ADDED" != "1" ] ; then
-    echo "Re-executing under a new ssh agent"
-    exec env BORG_RW_KEY_ADDED=1 ssh-agent "$0"
-fi
-
-echo "=== Please enter SSH key passphrase.  Check Bitwarden for:"
-echo "===   borg $HOSTNAME / read-write SSH key"
-ssh-add "$(realpath "$(dirname "$0")")/ssh/id_ecdsa"
-
-$BORG --rw prune \
-        --verbose \
-        --progress \
-        --stats \
-        --keep-within=7d \
-        --keep-daily=14 \
-        --keep-weekly=8 \
-        --keep-monthly=-1
-
-$BORG --rw compact \
-        --verbose \
-        --progress