#!/usr/bin/env bash

#########################################################################################
#### gcp-firewall-auditor.sh — Audit GCP VPC firewall rules for risky configs        ####
#### Finds 0.0.0.0/0 rules, dangerous ports, overly permissive access, unused rules  ####
#### Requires: bash 4+, gcloud CLI, jq                                               ####
####                                                                                 ####
#### Author: Phil Connor                                                             ####
#### Contact: contact@mylinux.work                                                   ####
#### License: MIT                                                                    ####
#### Version 1.01                                                                    ####
####                                                                                 ####
#### Usage:                                                                          ####
####   ./gcp-firewall-auditor.sh --full                                              ####
####                                                                                 ####
#### See --help for all options.                                                     ####
#########################################################################################

set -euo pipefail

# ── Colors (pre-initialized) ─────────────────────────────────────────
RED="" GREEN="" YELLOW="" BLUE="" CYAN="" BOLD="" DIM="" RESET=""

setup_colors() {
    if [[ "${COLOR:-auto}" == "never" ]]; then
        return
    fi
    if [[ "${COLOR:-auto}" == "always" ]] || [[ -t 1 ]]; then
        RED='\033[0;31m'
        GREEN='\033[0;32m'
        YELLOW='\033[0;33m'
        BLUE='\033[0;34m'
        CYAN='\033[0;36m'
        BOLD='\033[1m'
        DIM='\033[2m'
        RESET='\033[0m'
    fi
}

# ── Logging ───────────────────────────────────────────────────────────
log()     { echo -e "${BLUE}[INFO]${RESET} $*"; }
warn()    { echo -e "${YELLOW}[WARN]${RESET} $*" >&2; }
err()     { echo -e "${RED}[ERROR]${RESET} $*" >&2; }
verbose() { if [[ "$VERBOSE" == "true" ]]; then echo -e "${DIM}[DEBUG]${RESET} $*"; fi; }
die()     { err "$*"; exit 1; }

# ── Severity counters ────────────────────────────────────────────────
TOTAL_CRIT=0
TOTAL_WARN=0
TOTAL_INFO=0
TOTAL_OK=0

flag_crit() { ((TOTAL_CRIT++)) || true; }
flag_warn() { ((TOTAL_WARN++)) || true; }
flag_info() { ((TOTAL_INFO++)) || true; }
flag_ok()   { ((TOTAL_OK++)) || true; }

# ── Defaults ──────────────────────────────────────────────────────────
RUN_MODE=""
DANGEROUS_PORTS="${DANGEROUS_PORTS:-22,3389,3306,5432,1433,6379,27017,9200,8080,8443}"
VERBOSE="${VERBOSE:-false}"
COLOR="${COLOR:-auto}"
GCP_PROJECT=""
VPC_NETWORK=""

# ── State ─────────────────────────────────────────────────────────────
SCRIPT_NAME="$(basename "$0")"
readonly SCRIPT_NAME
START_TIME=""

# ── Dependency and credential checks ────────────────────────────────
check_deps() {
    command -v gcloud &>/dev/null || die "gcloud CLI is required (install: https://cloud.google.com/sdk/docs/install)"
    command -v jq &>/dev/null || die "jq is required"
}

check_credentials() {
    local account
    account=$(gcloud auth list --filter="status:ACTIVE" --format="value(account)" 2>/dev/null)
    [[ -z "$account" ]] && die "No active gcloud credentials — run 'gcloud auth login'"

    if [[ -n "$GCP_PROJECT" ]]; then
        gcloud config set project "$GCP_PROJECT" --quiet 2>/dev/null \
            || die "Cannot set project: ${GCP_PROJECT}"
    else
        GCP_PROJECT=$(gcloud config get-value project 2>/dev/null)
        [[ -z "$GCP_PROJECT" || "$GCP_PROJECT" == "(unset)" ]] && die "No project set — use --project or 'gcloud config set project'"
    fi

    verbose "Account: ${account}"
    log "Project: ${GCP_PROJECT}"
}

# ── gcloud wrapper ───────────────────────────────────────────────────
gc_cmd() {
    local args=("$@")
    [[ -n "$GCP_PROJECT" ]] && args+=(--project "$GCP_PROJECT")
    verbose "gcloud ${args[*]}"
    gcloud "${args[@]}"
}

# ── Port-to-service mapping ─────────────────────────────────────────
port_to_service() {
    local port="$1"
    case "$port" in
        22)    echo "SSH" ;;
        80)    echo "HTTP" ;;
        443)   echo "HTTPS" ;;
        3306)  echo "MySQL" ;;
        5432)  echo "PostgreSQL" ;;
        1433)  echo "MSSQL" ;;
        3389)  echo "RDP" ;;
        6379)  echo "Redis" ;;
        27017) echo "MongoDB" ;;
        9200)  echo "Elasticsearch" ;;
        8080)  echo "HTTP-Alt" ;;
        8443)  echo "HTTPS-Alt" ;;
        53)    echo "DNS" ;;
        25)    echo "SMTP" ;;
        5900)  echo "VNC" ;;
        11211) echo "Memcached" ;;
        2379)  echo "etcd" ;;
        9090)  echo "Prometheus" ;;
        *)     echo "" ;;
    esac
}

# ── Check if port is in dangerous list ───────────────────────────────
is_dangerous_port() {
    local port="$1"
    local IFS=','
    for dp in $DANGEROUS_PORTS; do
        if [[ "$port" == "$dp" ]]; then
            return 0
        fi
    done
    return 1
}

# ── Check if port falls in a range ───────────────────────────────────
port_in_range() {
    local port="$1" range="$2"
    if [[ "$range" == *-* ]]; then
        local start="${range%-*}"
        local end="${range#*-}"
        [[ "$port" -ge "$start" && "$port" -le "$end" ]]
    else
        [[ "$port" == "$range" ]]
    fi
}

# ── Fetch firewall rules ────────────────────────────────────────────
fetch_rules() {
    local args=(compute firewall-rules list --format=json)
    if [[ -n "$VPC_NETWORK" ]]; then
        args+=(--filter="network~${VPC_NETWORK}")
    fi
    gc_cmd "${args[@]}" 2>/dev/null
}

# ══════════════════════════════════════════════════════════════════════
#                       OPEN PORTS AUDIT
# ══════════════════════════════════════════════════════════════════════
audit_open_ports() {
    log "Auditing firewall rules for dangerous open ports..."
    log "Dangerous ports: ${DANGEROUS_PORTS}"
    echo ""

    printf "  %-28s %-14s %-8s %-8s %-18s %s\n" \
        "RULE_NAME" "NETWORK" "PROTO" "PORT" "SOURCE" "SEVERITY"
    printf "  %s\n" "$(printf '%.0s─' {1..95})"

    local rules_json
    rules_json=$(fetch_rules)

    echo "$rules_json" | jq -c '.[] | select(.direction == "INGRESS" and .disabled != true)' 2>/dev/null | while IFS= read -r rule; do
        local rule_name network
        rule_name=$(echo "$rule" | jq -r '.name')
        network=$(echo "$rule" | jq -r '.network' | rev | cut -d/ -f1 | rev)

        local has_open="false"
        while IFS= read -r src; do
            if [[ "$src" == "0.0.0.0/0" ]]; then
                has_open="true"
                break
            fi
        done < <(echo "$rule" | jq -r '.sourceRanges[]? // empty' 2>/dev/null)

        [[ "$has_open" != "true" ]] && continue

        echo "$rule" | jq -c '.allowed[]? // empty' 2>/dev/null | while IFS= read -r allowed; do
            local protocol
            protocol=$(echo "$allowed" | jq -r '.IPProtocol')

            local ports
            ports=$(echo "$allowed" | jq -r '.ports[]? // empty' 2>/dev/null)

            if [[ -z "$ports" ]]; then
                if [[ "$protocol" == "all" ]]; then
                    printf "  %-28s %-14s %-8s %-8s %-18s %b%s%b\n" \
                        "${rule_name:0:27}" "${network:0:13}" "all" "all" \
                        "0.0.0.0/0" "$RED" "CRITICAL" "$RESET"
                    flag_crit
                else
                    local IFS=','
                    for dp in $DANGEROUS_PORTS; do
                        local svc
                        svc=$(port_to_service "$dp")
                        printf "  %-28s %-14s %-8s %-8s %-18s %b%s%b\n" \
                            "${rule_name:0:27}" "${network:0:13}" "$protocol" "$dp" \
                            "0.0.0.0/0" "$RED" "CRITICAL" "$RESET"
                        flag_crit
                    done
                fi
                continue
            fi

            while IFS= read -r port_spec; do
                [[ -z "$port_spec" ]] && continue

                local IFS=','
                for dp in $DANGEROUS_PORTS; do
                    if port_in_range "$dp" "$port_spec"; then
                        local svc severity color
                        svc=$(port_to_service "$dp")
                        if [[ "$dp" == "80" || "$dp" == "443" ]]; then
                            severity="INFO"; color="$CYAN"; flag_info
                        else
                            severity="CRITICAL"; color="$RED"; flag_crit
                        fi
                        printf "  %-28s %-14s %-8s %-8s %-18s %b%s%b\n" \
                            "${rule_name:0:27}" "${network:0:13}" "$protocol" \
                            "${dp} (${svc})" "0.0.0.0/0" "$color" "$severity" "$RESET"
                    fi
                done
            done <<< "$ports"
        done
    done

    echo ""
}

# ══════════════════════════════════════════════════════════════════════
#                       PERMISSIVE RULES AUDIT
# ══════════════════════════════════════════════════════════════════════
audit_permissive() {
    log "Auditing overly permissive firewall rules..."
    echo ""

    printf "  %-28s %-14s %-14s %-18s %s\n" \
        "RULE_NAME" "NETWORK" "PROTOCOLS" "SOURCE" "SEVERITY"
    printf "  %s\n" "$(printf '%.0s─' {1..85})"

    local rules_json
    rules_json=$(fetch_rules)

    echo "$rules_json" | jq -c '.[] | select(.direction == "INGRESS" and .disabled != true)' 2>/dev/null | while IFS= read -r rule; do
        local rule_name network
        rule_name=$(echo "$rule" | jq -r '.name')
        network=$(echo "$rule" | jq -r '.network' | rev | cut -d/ -f1 | rev)

        local has_open="false"
        while IFS= read -r src; do
            if [[ "$src" == "0.0.0.0/0" ]]; then
                has_open="true"
                break
            fi
        done < <(echo "$rule" | jq -r '.sourceRanges[]? // empty' 2>/dev/null)

        [[ "$has_open" != "true" ]] && continue

        local has_all_traffic="false"
        while IFS= read -r allowed; do
            local proto
            proto=$(echo "$allowed" | jq -r '.IPProtocol')
            local port_count
            port_count=$(echo "$allowed" | jq '.ports // [] | length')

            if [[ "$proto" == "all" ]]; then
                has_all_traffic="true"
            elif [[ "$port_count" -eq 0 ]]; then
                has_all_traffic="true"
            fi
        done < <(echo "$rule" | jq -c '.allowed[]? // empty' 2>/dev/null)

        if [[ "$has_all_traffic" == "true" ]]; then
            local proto_list
            proto_list=$(echo "$rule" | jq -r '[.allowed[]?.IPProtocol] | join(",")' 2>/dev/null)
            printf "  %-28s %-14s %-14s %-18s %b%s%b\n" \
                "${rule_name:0:27}" "${network:0:13}" "${proto_list:0:13}" \
                "0.0.0.0/0" "$RED" "CRITICAL" "$RESET"
            flag_crit
        fi
    done

    echo ""
}

# ══════════════════════════════════════════════════════════════════════
#                       EGRESS AUDIT
# ══════════════════════════════════════════════════════════════════════
audit_egress() {
    log "Auditing egress firewall rules..."
    echo ""

    printf "  %-28s %-14s %-14s %-18s %s\n" \
        "RULE_NAME" "NETWORK" "PROTOCOLS" "DESTINATION" "SEVERITY"
    printf "  %s\n" "$(printf '%.0s─' {1..85})"

    local rules_json
    rules_json=$(fetch_rules)

    echo "$rules_json" | jq -c '.[] | select(.direction == "EGRESS" and .disabled != true)' 2>/dev/null | while IFS= read -r rule; do
        local rule_name network
        rule_name=$(echo "$rule" | jq -r '.name')
        network=$(echo "$rule" | jq -r '.network' | rev | cut -d/ -f1 | rev)

        local has_wide="false"
        while IFS= read -r dest; do
            if [[ "$dest" == "0.0.0.0/0" ]]; then
                has_wide="true"
                break
            fi
        done < <(echo "$rule" | jq -r '.destinationRanges[]? // empty' 2>/dev/null)

        [[ "$has_wide" != "true" ]] && continue

        local proto_list
        proto_list=$(echo "$rule" | jq -r '[.allowed[]?.IPProtocol] | join(",")' 2>/dev/null)

        local severity="WARN" color="$YELLOW"
        if [[ "$proto_list" == "all" ]]; then
            severity="WARN"; color="$YELLOW"; flag_warn
        else
            severity="INFO"; color="$CYAN"; flag_info
        fi

        printf "  %-28s %-14s %-14s %-18s %b%s%b\n" \
            "${rule_name:0:27}" "${network:0:13}" "${proto_list:0:13}" \
            "0.0.0.0/0" "$color" "$severity" "$RESET"
    done

    echo ""
}

# ══════════════════════════════════════════════════════════════════════
#                       UNUSED RULES AUDIT
# ══════════════════════════════════════════════════════════════════════
audit_unused() {
    log "Checking for disabled or potentially unused firewall rules..."
    echo ""

    printf "  %-28s %-14s %-10s %-10s %s\n" \
        "RULE_NAME" "NETWORK" "DIRECTION" "DISABLED" "SEVERITY"
    printf "  %s\n" "$(printf '%.0s─' {1..80})"

    local rules_json
    rules_json=$(fetch_rules)

    echo "$rules_json" | jq -c '.[]' 2>/dev/null | while IFS= read -r rule; do
        local rule_name network direction disabled
        rule_name=$(echo "$rule" | jq -r '.name')
        network=$(echo "$rule" | jq -r '.network' | rev | cut -d/ -f1 | rev)
        direction=$(echo "$rule" | jq -r '.direction')
        disabled=$(echo "$rule" | jq -r '.disabled // false')

        if [[ "$disabled" == "true" ]]; then
            printf "  %-28s %-14s %-10s %-10s %b%s%b\n" \
                "${rule_name:0:27}" "${network:0:13}" "$direction" "YES" \
                "$YELLOW" "WARN — disabled" "$RESET"
            flag_warn
            continue
        fi

        local target_tags
        target_tags=$(echo "$rule" | jq -r '.targetTags // [] | join(",")' 2>/dev/null)

        if [[ -n "$target_tags" && "$target_tags" != "null" ]]; then
            local first_tag="${target_tags%%,*}"
            local instance_count
            instance_count=$(gcloud compute instances list \
                --filter="tags.items=${first_tag}" \
                --format="value(name)" 2>/dev/null | wc -l)

            if [[ "$instance_count" -eq 0 ]]; then
                printf "  %-28s %-14s %-10s %-10s %b%s%b\n" \
                    "${rule_name:0:27}" "${network:0:13}" "$direction" "NO" \
                    "$YELLOW" "WARN — no targets" "$RESET"
                flag_warn
            else
                verbose "Rule ${rule_name}: ${instance_count} matching instance(s)"
                flag_ok
            fi
        else
            flag_ok
        fi
    done

    echo ""
}

# ══════════════════════════════════════════════════════════════════════
#                       LIST ALL RULES
# ══════════════════════════════════════════════════════════════════════
list_rules() {
    log "Listing all firewall rules..."
    echo ""

    printf "  %-28s %-14s %-10s %-8s %-12s %-18s %s\n" \
        "RULE_NAME" "NETWORK" "DIR" "PROTO" "PORTS" "SOURCE/DEST" "PRIORITY"
    printf "  %s\n" "$(printf '%.0s─' {1..105})"

    local rules_json
    rules_json=$(fetch_rules)

    echo "$rules_json" | jq -c '.[]' 2>/dev/null | while IFS= read -r rule; do
        local rule_name network direction priority
        rule_name=$(echo "$rule" | jq -r '.name')
        network=$(echo "$rule" | jq -r '.network' | rev | cut -d/ -f1 | rev)
        direction=$(echo "$rule" | jq -r '.direction')
        priority=$(echo "$rule" | jq -r '.priority')

        local cidr_list
        if [[ "$direction" == "INGRESS" ]]; then
            cidr_list=$(echo "$rule" | jq -r '.sourceRanges[0]? // "any"' 2>/dev/null)
        else
            cidr_list=$(echo "$rule" | jq -r '.destinationRanges[0]? // "any"' 2>/dev/null)
        fi

        echo "$rule" | jq -c '.allowed[]? // empty' 2>/dev/null | while IFS= read -r allowed; do
            local proto port_str
            proto=$(echo "$allowed" | jq -r '.IPProtocol')
            port_str=$(echo "$allowed" | jq -r '.ports // ["all"] | join(",")' 2>/dev/null)
            [[ "$port_str" == "null" ]] && port_str="all"

            local dir_color="$CYAN"
            [[ "$direction" == "EGRESS" ]] && dir_color="$YELLOW"

            printf "  %-28s %-14s %b%-10s%b %-8s %-12s %-18s %s\n" \
                "${rule_name:0:27}" "${network:0:13}" "$dir_color" "$direction" "$RESET" \
                "$proto" "${port_str:0:11}" "${cidr_list:0:17}" "$priority"
        done
    done

    echo ""
}

# ══════════════════════════════════════════════════════════════════════
#                       SUMMARY
# ══════════════════════════════════════════════════════════════════════
print_summary() {
    local elapsed
    elapsed=$(( $(date +%s) - START_TIME ))

    echo ""
    echo "  ══════════════════════════════════════════"
    echo "  Firewall Audit Summary"
    echo "  ══════════════════════════════════════════"
    printf "  %-20s %b%d%b\n" "CRITICAL:" "$RED" "$TOTAL_CRIT" "$RESET"
    printf "  %-20s %b%d%b\n" "WARN:" "$YELLOW" "$TOTAL_WARN" "$RESET"
    printf "  %-20s %b%d%b\n" "INFO:" "$CYAN" "$TOTAL_INFO" "$RESET"
    printf "  %-20s %b%d%b\n" "OK:" "$GREEN" "$TOTAL_OK" "$RESET"
    echo "  ──────────────────────────────────────────"
    printf "  Completed in %ds\n" "$elapsed"
    echo ""

    if [[ "$TOTAL_CRIT" -gt 0 ]]; then
        echo -e "  ${RED}${BOLD}Action required:${RESET} ${TOTAL_CRIT} critical finding(s)"
        echo ""
        echo "  Top recommendations:"
        echo "    • Close 0.0.0.0/0 rules on SSH (22), RDP (3389), and database ports"
        echo "    • Replace all-protocol allow rules with specific port lists"
        echo "    • Use target tags or service accounts to scope rules"
        echo "    • Delete disabled rules that are no longer needed"
        echo ""
    elif [[ "$TOTAL_WARN" -gt 0 ]]; then
        echo -e "  ${YELLOW}Review recommended:${RESET} ${TOTAL_WARN} warning(s)"
        echo ""
        echo "  Suggestions:"
        echo "    • Review disabled rules for deletion"
        echo "    • Check rules with no matching target instances"
        echo "    • Restrict egress where applicable"
        echo ""
    else
        echo -e "  ${GREEN}All checks passed${RESET}"
        echo ""
    fi
}

# ══════════════════════════════════════════════════════════════════════
#                       USAGE
# ══════════════════════════════════════════════════════════════════════
show_help() {
    cat <<EOF
${BOLD}${SCRIPT_NAME}${RESET} — GCP Firewall Auditor

Audit GCP VPC firewall rules across all networks for risky
configurations via gcloud CLI.

${BOLD}MODES${RESET}
  --full              Run all audits
  --open-ports        Find dangerous ports open to 0.0.0.0/0
  --permissive        Find overly broad allow rules
  --unused            Find disabled or targetless rules
  --egress            Audit wide egress rules
  --rules             List all firewall rules

${BOLD}OPTIONS${RESET}
  --project PROJECT   GCP project ID
  --network NETWORK   Limit to specific VPC network
  --ports PORTS       Override dangerous ports (comma-separated)
  --verbose           Debug output
  --no-color          Disable colored output
  --help              Show this help message

${BOLD}ENVIRONMENT VARIABLES${RESET}
  DANGEROUS_PORTS      Comma-separated ports to flag (default: 22,3389,...)
  VERBOSE              Enable verbose output (true/false)
  COLOR                Color mode: auto, always, never

${BOLD}EXAMPLES${RESET}
  # Full audit
  ${SCRIPT_NAME} --full

  # Check open ports only
  ${SCRIPT_NAME} --open-ports

  # Audit a specific project
  ${SCRIPT_NAME} --full --project my-prod-project

  # Filter by VPC network
  ${SCRIPT_NAME} --open-ports --network prod-vpc

  # Custom dangerous ports
  ${SCRIPT_NAME} --open-ports --ports "22,3389,5432,6379"

  # List all firewall rules
  ${SCRIPT_NAME} --rules

${BOLD}EXIT CODES${RESET}
  0   All checks passed
  1   Warnings found (review recommended)
  2   Critical findings (action required)
EOF
}

# ══════════════════════════════════════════════════════════════════════
#                       PARSE ARGS
# ══════════════════════════════════════════════════════════════════════
parse_args() {
    local modes=()

    while [[ $# -gt 0 ]]; do
        case "$1" in
            --full)
                modes=(open-ports permissive unused egress)
                shift ;;
            --open-ports)
                modes+=(open-ports); shift ;;
            --permissive)
                modes+=(permissive); shift ;;
            --unused)
                modes+=(unused); shift ;;
            --egress)
                modes+=(egress); shift ;;
            --rules)
                modes+=(rules); shift ;;
            --project)
                GCP_PROJECT="${2:?--project requires a value}"; shift 2 ;;
            --network)
                VPC_NETWORK="${2:?--network requires a value}"; shift 2 ;;
            --ports)
                DANGEROUS_PORTS="${2:?--ports requires a value}"; shift 2 ;;
            --verbose)
                VERBOSE="true"; shift ;;
            --no-color)
                COLOR="never"; shift ;;
            --help|-h)
                setup_colors; show_help; exit 0 ;;
            *)
                die "Unknown option: $1 (see --help)" ;;
        esac
    done

    if [[ ${#modes[@]} -eq 0 ]]; then
        err "No audit mode specified"
        echo "Run ${SCRIPT_NAME} --help for usage" >&2
        exit 1
    fi

    RUN_MODE="${modes[*]}"
}

# ══════════════════════════════════════════════════════════════════════
#                       MAIN
# ══════════════════════════════════════════════════════════════════════
main() {
    parse_args "$@"
    setup_colors
    check_deps
    check_credentials

    START_TIME=$(date +%s)

    echo ""
    echo -e "${BOLD}GCP Firewall Auditor${RESET}"
    echo -e "Project: ${GCP_PROJECT}"
    echo -e "Mode:    ${RUN_MODE}"
    if [[ -n "$VPC_NETWORK" ]]; then
        echo -e "Network: ${VPC_NETWORK}"
    fi
    echo -e "Time:    $(date -u +%Y-%m-%dT%H:%M:%SZ)"
    echo ""

    for mode in $RUN_MODE; do
        case "$mode" in
            open-ports)  audit_open_ports ;;
            permissive)  audit_permissive ;;
            unused)      audit_unused ;;
            egress)      audit_egress ;;
            rules)       list_rules ;;
        esac
    done

    print_summary

    if [[ "$TOTAL_CRIT" -gt 0 ]]; then
        exit 2
    elif [[ "$TOTAL_WARN" -gt 0 ]]; then
        exit 1
    fi
    exit 0
}

main "$@"