pihole_FTL_API.sh

#!/usr/bin/env bash

# read previous history
history -r ftl_api_history

DisplayHelp()
{
    echo ""
    echo "Query FTLv6's API"
    echo ""
    echo "Usage: $0 [--server <DOMAIN|IP>] [--secret <secret password>] "
    echo ""
    echo "To connect to FTL's API use the following options"
    echo ""
    echo " --server <DOMAIN|IP>  		        URL or address of your Pi-hole (default: localhost)"
    echo " --secret <secret password>		Your Pi-hole password, required to access the API"
    echo ""
    echo "End script with Ctrl+C"
    echo ""
    echo ""
    echo "The returned data can be processed further by appending the desired command"
    echo "to the API endpoint. So things like"
    echo ""
    echo "'stats/summary | jq .queries.blocked'"
    echo ""
    echo "will work."
    echo ""
}

secretRead() {

    # POSIX compliant function to read user-input and
    # mask every character entered by (*)
    #
    # This is challenging, because in POSIX, `read` does not support
    # `-s` option (suppressing the input) or
    # `-n` option (reading n chars)


    # This workaround changes the terminal characteristics to not echo input and later rests this option
    # credits https://stackoverflow.com/a/4316765
    # showing astrix instead of password
    # https://stackoverflow.com/a/24600839
    # https://unix.stackexchange.com/a/464963

    stty -echo # do not echo user input
    stty -icanon min 1 time 0 # disable cannonical mode https://man7.org/linux/man-pages/man3/termios.3.html

    unset password
    unset key
    unset charcount
    charcount=0
    while key=$(dd ibs=1 count=1 2>/dev/null); do #read one byte of input
        if [ "${key}" = "$(printf '\0' | tr -d '\0')" ] ; then
            # Enter - accept password
            break
        fi
        if [ "${key}" = "$(printf '\177')" ] ; then
            # Backspace
            if [ $charcount -gt 0 ] ; then
                charcount=$((charcount-1))
                printf '\b \b'
                password="${password%?}"
            fi
        else
            # any other character
            charcount=$((charcount+1))
            printf '*'
            password="$password$key"
        fi
    done

    # restore original terminal settings
    stty "${stty_orig}"
}

TestAPIAvailability() {

    local chaos_api_list availabilityResonse cmdResult digReturnCode

    # Query the API URLs from FTL using CHAOS TXT
    # The result is a space-separated enumeration of full URLs
    # e.g., "http://localhost:80/api" or "https://domain.com:443/api"
    if [ -z "${SERVER}" ] || [ "${SERVER}" = "localhost" ] || [ "${SERVER}" = "127.0.0.1" ]; then
        # --server was not set or set to local, assuming we're running locally
        cmdResult="$(dig +short chaos txt local.api.ftl @localhost 2>&1; echo $?)"
    else
        # --server was set, try to get response from there
        cmdResult="$(dig +short chaos txt domain.api.ftl @"${SERVER}" 2>&1; echo $?)"
    fi

    # Gets the return code of the dig command (last line)
    # We can't use${cmdResult##*$'\n'*} here as $'..' is not POSIX
    digReturnCode="$(echo "${cmdResult}" | tail -n 1)"

    if [ ! "${digReturnCode}" = "0" ]; then
        # If the query was not successful
        echo "API not available. Please check server address and connectivity"
        exit 1
    else
      # Dig returned 0 (success), so get the actual response (first line)
      chaos_api_list="$(echo "${cmdResult}" | head -n 1)"
    fi

    # Iterate over space-separated list of URLs
    while [ -n "${chaos_api_list}" ]; do
        # Get the first URL
        API_URL="${chaos_api_list%% *}"
        # Strip leading and trailing quotes
        API_URL="${API_URL%\"}"
        API_URL="${API_URL#\"}"

        # Test if the API is available at this URL
        availabilityResonse=$(curl -skS -o /dev/null -w "%{http_code}" "${API_URL}auth")

        # Test if http status code was 200 (OK) or 401 (authentication required)
        if [ ! "${availabilityResonse}" = 200 ] && [ ! "${availabilityResonse}" = 401 ]; then
            # API is not available at this port/protocol combination
            API_PORT=""
        else
            # API is available at this URL combination
            break
        fi

        # Remove the first URL from the list
        local last_api_list
        last_api_list="${chaos_api_list}"
        chaos_api_list="${chaos_api_list#* }"

        # If the list did not change, we are at the last element
        if [ "${last_api_list}" = "${chaos_api_list}" ]; then
            # Remove the last element
            chaos_api_list=""
        fi
    done

    # if API_PORT is empty, no working API port was found
    if [ -n "${API_PORT}" ]; then
        echo "API not available at: ${API_URL}"
        echo "Exiting."
        exit 1
    fi
}

Authenthication() {
    # Try to authenticate
    LoginAPI

    while [ "${validSession}" = false ] || [ -z "${validSession}" ] ; do
        echo "Authentication failed."

        # no password was supplied as argument
        if [ -z "${password}" ]; then
            echo "No password supplied. Please enter your password:"
        else
            echo "Wrong password supplied, please enter the correct password:"
        fi

        # secretly read the password
        secretRead

        echo ""

        # Try to authenticate again
        LoginAPI
    done

    # Loop exited, authentication was successful
    echo "Authentication successful."

}

DeleteSession() {
    # if a valid Session exists (no password required or successful authenthication) and
    # SID is not null (successful authenthication only), delete the session
    if [ "${validSession}" = true ] && [ ! "${SID}" = null ]; then
        # Try to delte the session. Omitt the output, but get the http status code
        deleteResponse=$(curl -skS -o /dev/null -w "%{http_code}" -X DELETE "${API_URL}auth"  -H "Accept: application/json" -H "sid: ${SID}")

        case "${deleteResponse}" in
            "204") printf "%b" "Session successfully deleted.\n";;
            "401") printf "%b" "Logout attempt without a valid session. Unauthorized!\n";;
         esac;
    fi

}

LoginAPI() {
    sessionResponse="$(curl -skS -X POST "${API_URL}auth" --data "{\"password\":\"${password}\"}" )"

    if [ -z "${sessionResponse}" ]; then
        echo "No response from FTL server. Please check connectivity and use the options to set the server domain/IP"
        echo "Usage: $0 [--server <domain|IP>]"
    exit 1
  fi

	# obtain validity and session ID from session response
	validSession=$(echo "${sessionResponse}"| jq .session.valid 2>/dev/null)
	SID=$(echo "${sessionResponse}"| jq --raw-output .session.sid 2>/dev/null)
}

GetFTLData() {
    local response
    # get the data from querying the API as well as the http status code
	response=$(curl -skS -w "%{http_code}" -X GET "${API_URL}$1" -H "Accept: application/json" -H "sid: ${SID}" )

    # status are the last 3 characters
    # not using ${response#"${response%???}"}" here because it's extremely slow on big responses
    status=$(printf "%s" "${response}" | tail -c 3)
    # data is everything from repsonse without the last 3 characters
    data=$(printf %s "${response%???}")

    if [ "${status}" = 200 ]; then
        echo "${data}"
    elif [ "${status}" = 000 ]; then
        # connection lost
        echo "000"
    elif [ "${status}" = 401 ]; then
        # unauthorized
        echo "401"
    fi
}

# Called on signals INT QUIT TERM
sig_cleanup() {
    # save error code (130 for SIGINT, 143 for SIGTERM, 131 for SIGQUIT)
    err=$?

    # some shells will call EXIT after the INT signal
    # causing EXIT trap to be executed, so we trap EXIT after INT
    trap '' EXIT

    # write history to file
    history -w ftl_api_history

    (exit $err) # execute in a subshell just to pass $? to clean_exit()
    clean_exit
}

# Called on signal EXIT, or indirectly on INT QUIT TERM
clean_exit() {
    # save the return code of the script
    err=$?

    # reset trap for all signals to not interrupt clean_tempfiles() on any next signal
    trap '' EXIT INT QUIT TERM

    # restore terminal settings if they have been changed (e.g. user cancled script while at password  input prompt)
    if [ "$(stty -g)" != "${stty_orig}" ]; then
        stty "${stty_orig}"
    fi

    #  Delete session from FTL server
    DeleteSession
    exit $err # exit the script with saved $?
}

QueryAPI() {
    while true; do
        local input endpoint the_rest data
        printf "%b" "\nRequest data from API endpoint:\n"

        # read the input and split it into $endpoint and $the_rest after the first space
        read -r -e input
        IFS=' ' read -r endpoint the_rest <<< "$input"

        # save last input to history
        history -s "$input"

        data=$(GetFTLData "${endpoint}")

        # check if connection to FTL was lost
        # GetFTLData() will return "000"
        if [ "${data}" = 000 ]; then
            printf "%b" "\nConection to FTL lost! Please re-establish connection.\n"
        elif [ "${data}" = 401 ]; then
            # check if a new authentication is required (e.g. after connection to FTL has re-established)
            # GetFTLData() will return "401" if a 401 http status code is returned
            # as $password should be set already, it should automatically re-authenticate
            LoginAPI
            printf "%b" "\nNeeded to re-authenticate. Please request endpoint again.\n"
        else
            # Data was returned

            # if there was any command supplied run it on the returned data
            if [ -n "${the_rest}" ]; then
                eval 'echo ${data}' "${the_rest}"
            else
                # only print the API response
                echo "${data}"
            fi
        fi
    done
}


################################# Main ################
# Process all options (if present)
while [ "$#" -gt 0 ]; do
  case "$1" in
    "-h" | "--help"     ) DisplayHelp; exit 0;;
    "--server"          ) SERVER="$2"; shift;;
    "--secret"          ) password="$2"; shift;;
    *                   ) DisplayHelp; exit 1;;
  esac
  shift
done

# Save current terminal settings (needed for later restore after password prompt)
stty_orig=$(stty -g)

# Traps for graceful shutdown
# https://unix.stackexchange.com/a/681201
trap clean_exit EXIT
trap sig_cleanup INT QUIT TERM

# Test if the authentication endpoint is availabe
TestAPIAvailability

# Authenticate with the server
Authenthication

# Query the API
QueryAPI