testsAndMisc/linux_configuration/features/lib/pi_flash_remote.sh

#!/bin/bash
# Remote laptop discovery and SSH key setup.
#
# Sourced by raspberry_pi_flash_sd.sh; split out to keep it under the 250-line
# cap. Sourced rather than run, so it inherits the caller's strict mode
# and the variables defined above the source line.

discover_remote_laptop() {
  log_info "Auto-discovering remote laptop on local network..."

  ensure_dependencies

  local my_ip
  my_ip=$(ip -4 addr show | grep -oP '(?<=inet\s)(?!127\.)\d+(\.\d+){3}' | head -1)

  local gateway
  gateway=$(ip route | grep default | awk '{print $3}' | head -1)
  local network="${gateway%.*}.0/24"

  log_info "Local IP: $my_ip, Gateway: $gateway, Network: $network"
  log_info "Scanning network for SSH-enabled devices (using nmap)..."

  local ssh_hosts
  nmap -sn -T4 "$network" &> /dev/null || true
  ssh_hosts=$(nmap -p 22 --open -sT -T4 "$network" 2> /dev/null | grep "Nmap scan report" | grep -oP '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+' | grep -vw "$my_ip" | sort -u)

  if [[ -z $ssh_hosts ]]; then
    die "No SSH-enabled devices found on network"
  fi

  local host_count
  host_count=$(echo "$ssh_hosts" | wc -l)
  log_info "Found $host_count SSH-enabled device(s): $(echo "$ssh_hosts" | tr '\n' ' ')"

  local common_users=("$REMOTE_LAPTOP_USER" "kuchy" "kuhy" "$(whoami)" "pi" "user" "admin")
  local users=()
  for u in "${common_users[@]}"; do
    local is_dup=0
    for existing in "${users[@]}"; do
      if [[ $u == "$existing" ]]; then
        is_dup=1
        break
      fi
    done
    if [[ $is_dup -eq 0 ]]; then
      users+=("$u")
    fi
  done

  log_info "Will try usernames: ${users[*]}"

  local found_laptop=""
  local found_user=""
  local idx=0

  for ip in $ssh_hosts; do
    idx=$((idx + 1))

    if [[ $ip == "$gateway" ]]; then
      log_info "[$idx/$host_count] Skipping $ip (gateway)"
      continue
    fi

    log_info "[$idx/$host_count] $ip - Trying SSH key access with common usernames..."

    for try_user in "${users[@]}"; do
      if ssh -o BatchMode=yes -o ConnectTimeout=2 -o StrictHostKeyChecking=accept-new "${try_user}@${ip}" "echo ok" 2> /dev/null | grep -q "ok"; then
        log_success "[$idx/$host_count] $ip - SSH key access confirmed with user '$try_user'!"
        found_user="$try_user"

        log_info "[$idx/$host_count] $ip - Checking for SD card..."
        local has_sd
        has_sd=$(ssh -o BatchMode=yes -o ConnectTimeout=2 "${try_user}@${ip}" "lsblk -d -o NAME,RM,TRAN 2>/dev/null | grep -E '1.*(usb|mmc)' | head -1" 2> /dev/null || true)

        if [[ -n $has_sd ]]; then
          log_success "[$idx/$host_count] $ip - Found SD card: $has_sd"
          found_laptop="$ip"
          break 2
        else
          log_warning "[$idx/$host_count] $ip - No SD card detected, saving as fallback..."
          if [[ -z $found_laptop ]]; then
            found_laptop="$ip"
          fi
        fi
        break
      fi
    done
  done

  if [[ -z $found_laptop ]] || [[ -z $found_user ]]; then
    log_warning "No device with passwordless SSH found using common usernames."

    found_laptop=$(echo "$ssh_hosts" | grep -vw "$gateway" | head -1)

    if [[ -z $found_laptop ]]; then
      die "Could not find any suitable SSH-enabled device"
    fi

    log_info "Found SSH host at $found_laptop but need credentials."
    read -r -p "Enter username for $found_laptop: " found_user

    if [[ -z $found_user ]]; then
      die "No username provided"
    fi
  fi

  REMOTE_LAPTOP_IP="$found_laptop"
  REMOTE_LAPTOP_USER="$found_user"
  log_success "Selected remote laptop: ${REMOTE_LAPTOP_USER}@${REMOTE_LAPTOP_IP}"

  save_config
}

setup_ssh_key_to_remote() {
  local remote_host="$1"
  local remote_user="$2"

  if ssh -o BatchMode=yes -o ConnectTimeout=5 "${remote_user}@${remote_host}" "echo 'SSH key works'" 2> /dev/null; then
    log_success "SSH key authentication to ${remote_user}@${remote_host} already configured"
    return 0
  fi

  log_info "Setting up SSH key authentication to ${remote_user}@${remote_host}..."

  if [[ ! -f ~/.ssh/id_rsa.pub ]] && [[ ! -f ~/.ssh/id_ed25519.pub ]]; then
    log_info "Generating SSH key..."
    ssh-keygen -t ed25519 -f ~/.ssh/id_ed25519 -N "" -q
  fi

  log_info "Copying SSH key to remote host (you may be prompted for password)..."

  if command -v ssh-copy-id &> /dev/null; then
    ssh-copy-id -o StrictHostKeyChecking=no "${remote_user}@${remote_host}"
  else
    local pub_key
    pub_key=$(cat ~/.ssh/id_ed25519.pub 2> /dev/null || cat ~/.ssh/id_rsa.pub)
    ssh -o StrictHostKeyChecking=no "${remote_user}@${remote_host}" "mkdir -p ~/.ssh && echo '$pub_key' >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys"
  fi

  log_success "SSH key authentication configured"
}