#!/bin/bash

## Note that the shebang is not used, but it's the login shell that
## will execute this command.

RSYNC_KEY_PATH=/etc/rsync/keys
RECOVER_KEY_PATH=${RSYNC_KEY_PATH}/recover

exname=$(basename "$0")

mkdir -p /var/log/rsync

LOG="/var/log/rsync/$exname.log"


ssh_connection=(${SSH_CONNECTION})
SSH_SOURCE_IP="${ssh_connection[0]}:${ssh_connection[1]}"

log() {
    printf "%s [%s] %s - %s\n" \
           "$(date --rfc-3339=seconds)" "$$" "$SSH_SOURCE_IP" "$*" \
           >> "$LOG"
}

log "NEW RECOVER CONNECTION"

if [ -z "$1" ] || ! [[ "$1" =~ ^[a-z0-9]+$ ]]; then
    log "INVALID SETUP, ARG 1 SHOULD BE MD5 AND IS: '$1'"
    echo "Your command has been rejected. Contact administrator."
    exit 1
fi

md5="$1"
log "RECOVER KEY $md5"

if [ -z "$2" ] || ! [[ "$2" =~ ^[a-zA-Z0-9._-]+$ ]]; then
    log "INVALID SETUP, IDENT IS: '$1'"
    echo "Your command has been rejected. Contact administrator."
    exit 1
fi

ident="$2"
log "IDENTIFIED AS $ident"

reject() {
    log "REJECTED: $SSH_ORIGINAL_COMMAND"
    # echo "ORIG: $SSH_ORIGINAL_COMMAND" >&2
    echo "Your command has been rejected and reported to sys admin." >&2
    exit 1
}


if [[ "$SSH_ORIGINAL_COMMAND" =~ [\&\(\{\;\<\>\`\$\}] ]]; then
    log "BAD CHARS DETECTED"
    # echo "Bad chars: $SSH_ORIGINAL_COMMAND" >&2
    reject
fi

if [[ "$SSH_ORIGINAL_COMMAND" =~ ^"rsync --server --sender -"[vnloHgDtpArRzCeiLsfx\.]+(" --"[a-z=%-]+|" --partial-dir .rsync-partial")*" . /var/mirror/$ident"(|/.*)$ ]]; then

    ## Interpret \ to allow passing spaces (want to avoid possible issue with \n)
    #read -a ssh_args <<< "${SSH_ORIGINAL_COMMAND}"
    ssh_args=(${SSH_ORIGINAL_COMMAND})

    last_arg="${ssh_args[@]: -1:1}"
    if ! new_path=$(realpath "$last_arg" 2>/dev/null); then
        log "FINAL PATH INVALID"
        reject
    fi

    if [[ "$new_path" != "$last_arg" ]] &&
           [[ "$new_path" != "/var/mirror/$ident/"* ]] &&
           [[ "$new_path" != "/var/mirror/$ident" ]]; then
        log "FINAL PATH SUSPICIOUS"
        reject
    fi

    sudo /usr/local/sbin/ssh-update-keys
    if ! [ -e "${RECOVER_KEY_PATH}/$md5" ]; then
        log "RECOVERY KEY $md5 JUST EXPIRED"
        reject
    fi

	log "ACCEPTED RECOVER COMMAND: $SSH_ORIGINAL_COMMAND"
	sudo "${ssh_args[@]}"
    errlvl="$?"

    for key_file in "${RECOVER_KEY_PATH}/$md5"{,.pub}; do
        [ -e "$key_file" ] || continue
        sudo touch "$key_file"  ## Update modified time to keep key longer
    done

    exit "$errlvl"
else
    log "REFUSED COMMAND AS IT DOESN'T MATCH ANY EXPECTED COMMAND"
	reject
fi