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#!/bin/sh
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# sish-client: environment-driven connector for a sish edge.
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# Claims hostnames on the edge via SSH reverse forwards and relays them to local
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# targets. Reconnects forever with exponential backoff. See README.md.
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set -eu
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set -f # routes may contain wildcards (*.example.com); never glob-expand them
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ESC=$(printf '\033')
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log() { printf '%s sish-client: %s\n' "$(date -u +%Y-%m-%dT%H:%M:%SZ)" "$*"; }
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die() { log "error: $*"; exit 64; }
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is_true() {
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case "$(printf '%s' "$1" | tr 'A-Z' 'a-z')" in
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1 | true | yes | on) return 0 ;;
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*) return 1 ;;
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esac
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}
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is_uint() { case "$1" in '' | *[!0-9]*) return 1 ;; *) return 0 ;; esac; }
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# --- configuration -----------------------------------------------------------
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SISH_HOST=${SISH_HOST:-}
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SISH_PORT=${SISH_PORT:-2222}
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SISH_USER=${SISH_USER:-connector}
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SISH_KEY=${SISH_KEY:-}
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SISH_KEY_FILE=${SISH_KEY_FILE:-/secrets/id_ed25519}
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SISH_HOST_KEY=${SISH_HOST_KEY:-}
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SISH_KNOWN_HOSTS_FILE=${SISH_KNOWN_HOSTS_FILE:-}
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SISH_STRICT_HOST_KEY=${SISH_STRICT_HOST_KEY:-true}
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ROUTES=${ROUTES:-}
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ROUTES_FILE=${ROUTES_FILE:-}
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TARGET=${TARGET:-}
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DEFAULT_BIND_PORT=${DEFAULT_BIND_PORT:-443}
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SNI_PROXY=${SNI_PROXY:-true}
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PROXY_PROTOCOL=${PROXY_PROTOCOL:-2}
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KEEPALIVE_INTERVAL=${KEEPALIVE_INTERVAL:-15}
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CONNECT_TIMEOUT=${CONNECT_TIMEOUT:-10}
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BACKOFF_MIN=${BACKOFF_MIN:-2}
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BACKOFF_MAX=${BACKOFF_MAX:-60}
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SSH_EXTRA_OPTS=${SSH_EXTRA_OPTS:-}
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STATE_DIR=${STATE_DIR:-/tmp/sish-client}
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[ -n "$SISH_HOST" ] || die "SISH_HOST is required"
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for v in SISH_PORT DEFAULT_BIND_PORT KEEPALIVE_INTERVAL CONNECT_TIMEOUT BACKOFF_MIN BACKOFF_MAX; do
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eval "val=\$$v"
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is_uint "$val" || die "$v must be a non-negative integer (got '$val')"
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done
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case "$PROXY_PROTOCOL" in 1 | 2 | off | none | false | 0) ;; *) die "PROXY_PROTOCOL must be 1, 2 or off" ;; esac
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umask 077
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mkdir -p "$STATE_DIR" || die "STATE_DIR $STATE_DIR is not writable (mount a tmpfs on /tmp with a read-only root fs)"
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READY_FILE=$STATE_DIR/ready
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FIFO=$STATE_DIR/ssh.out
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KEY=$STATE_DIR/id_key
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KNOWN_HOSTS=$STATE_DIR/known_hosts
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rm -f "$READY_FILE"
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# --- private key: always copied so ssh sees a private 0600 file we own -------
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if [ -n "$SISH_KEY" ]; then
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printf '%s\n' "$SISH_KEY" > "$KEY"
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elif [ -r "$SISH_KEY_FILE" ]; then
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cat "$SISH_KEY_FILE" > "$KEY"
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else
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die "no private key: set SISH_KEY or mount a readable key at SISH_KEY_FILE ($SISH_KEY_FILE)"
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fi
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chmod 600 "$KEY"
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# --- host key verification ---------------------------------------------------
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HOST_KEY_OPTS=""
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if [ -n "$SISH_HOST_KEY" ]; then
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printf 'sish-edge %s\n' "$SISH_HOST_KEY" > "$KNOWN_HOSTS"
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HOST_KEY_OPTS="-o HostKeyAlias=sish-edge -o UserKnownHostsFile=$KNOWN_HOSTS -o StrictHostKeyChecking=yes"
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elif [ -n "$SISH_KNOWN_HOSTS_FILE" ]; then
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[ -r "$SISH_KNOWN_HOSTS_FILE" ] || die "SISH_KNOWN_HOSTS_FILE $SISH_KNOWN_HOSTS_FILE is not readable"
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HOST_KEY_OPTS="-o UserKnownHostsFile=$SISH_KNOWN_HOSTS_FILE -o StrictHostKeyChecking=yes"
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elif is_true "$SISH_STRICT_HOST_KEY"; then
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die "no host key: set SISH_HOST_KEY (e.g. 'ssh-ed25519 AAAA...') or SISH_KNOWN_HOSTS_FILE"
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else
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log "WARNING: host key verification disabled (SISH_STRICT_HOST_KEY=false)"
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HOST_KEY_OPTS="-o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no"
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fi
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# --- routes ------------------------------------------------------------------
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# Entry: <host>[:<bind-port>][=<target-host>:<target-port>]
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# Without "=target", TARGET is used. Bind port defaults to DEFAULT_BIND_PORT.
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route_entries() {
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{
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printf '%s\n' "$ROUTES" | tr ', ' '\n\n'
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if [ -n "$ROUTES_FILE" ]; then
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[ -r "$ROUTES_FILE" ] || die "ROUTES_FILE $ROUTES_FILE is not readable"
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sed 's/#.*//' "$ROUTES_FILE" | tr ', \t' '\n\n\n'
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fi
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} | sed '/^[[:space:]]*$/d'
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}
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FORWARDS=""
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ROUTE_COUNT=0
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for entry in $(route_entries); do
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case "$entry" in
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*=*) bind=${entry%%=*} target=${entry#*=} ;;
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*) bind=$entry target=$TARGET ;;
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esac
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[ -n "$target" ] || die "route '$entry' has no target and TARGET is not set"
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case "$target" in *:*) ;; *) die "target '$target' of route '$entry' must be host:port" ;; esac
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case "$bind" in *:*) ;; *) bind="$bind:$DEFAULT_BIND_PORT" ;; esac
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FORWARDS="$FORWARDS -R $bind:$target"
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ROUTE_COUNT=$((ROUTE_COUNT + 1))
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log "route: $bind -> $target"
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done
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[ "$ROUTE_COUNT" -gt 0 ] || die "no routes: set ROUTES and/or ROUTES_FILE"
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# --- sish session options (sent as the remote "command") ---------------------
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REMOTE_CMD=""
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is_true "$SNI_PROXY" && REMOTE_CMD="$REMOTE_CMD sni-proxy=true"
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case "$PROXY_PROTOCOL" in 1 | 2) REMOTE_CMD="$REMOTE_CMD proxy-protocol=$PROXY_PROTOCOL" ;; esac
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SSH_OPTS="-T -p $SISH_PORT -i $KEY
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-o IdentitiesOnly=yes -o BatchMode=yes -o LogLevel=ERROR
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-o ExitOnForwardFailure=yes
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-o ConnectTimeout=$CONNECT_TIMEOUT
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-o ServerAliveInterval=$KEEPALIVE_INTERVAL -o ServerAliveCountMax=3
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$HOST_KEY_OPTS $SSH_EXTRA_OPTS"
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# --- run loop ----------------------------------------------------------------
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SSH_PID=""
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shutdown() {
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log "received signal, shutting down"
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rm -f "$READY_FILE"
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[ -n "$SSH_PID" ] && kill "$SSH_PID" 2>/dev/null
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exit 0
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}
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trap shutdown TERM INT
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# Runs one ssh session. Marks ready once sish confirmed every forward.
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WAS_READY=0
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run_once() {
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WAS_READY=0
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rm -f "$READY_FILE" "$FIFO"
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mkfifo "$FIFO"
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# shellcheck disable=SC2086 # word splitting of option strings is intended
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ssh $SSH_OPTS $FORWARDS "$SISH_USER@$SISH_HOST" $REMOTE_CMD > "$FIFO" 2>&1 &
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SSH_PID=$!
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confirmed=0
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while IFS= read -r line; do
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line=$(printf '%s' "$line" | sed "s/${ESC}\[[0-9;]*m//g; s/\r\$//")
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[ -n "$line" ] || continue
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log "edge: $line"
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case "$line" in
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*"Starting SSH Forwarding service"*)
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confirmed=$((confirmed + 1))
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if [ "$confirmed" -ge "$ROUTE_COUNT" ] && [ "$WAS_READY" -eq 0 ]; then
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WAS_READY=1
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: > "$READY_FILE"
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log "ready: $confirmed/$ROUTE_COUNT forward(s) active"
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fi
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;;
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esac
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done < "$FIFO"
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rc=0
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wait "$SSH_PID" || rc=$?
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SSH_PID=""
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rm -f "$READY_FILE" "$FIFO"
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return "$rc"
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}
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delay=$BACKOFF_MIN
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while :; do
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log "connecting to $SISH_USER@$SISH_HOST:$SISH_PORT ($ROUTE_COUNT route(s))"
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rc=0
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run_once || rc=$?
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[ "$WAS_READY" -eq 1 ] && delay=$BACKOFF_MIN
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log "tunnel closed (exit $rc), reconnecting in ${delay}s"
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sleep "$delay" &
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wait $! || true
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delay=$((delay * 2))
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[ "$delay" -le "$BACKOFF_MAX" ] || delay=$BACKOFF_MAX
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done
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Reference in New Issue
Block a user