path: root/lib/keyringer/functions

#!/usr/bin/env bash
#
# Common functions.
#

# Setup main configuration and load preferences
function keyringer_config_load {
  if [ -f "$HOME/.$NAME" ]; then
    echo "Converting legacy configuration scheme..."
    mv "$HOME/.$NAME" "$HOME/.$NAME.tmp"
    mkdir "$HOME/.$NAME"
    mv "$HOME/.$NAME.tmp" "$CONFIG"
  fi

  if [ ! -e "$CONFIG" ]; then
    echo "Creating $CONFIG..."
    mkdir -p `dirname $CONFIG`
    touch "$CONFIG"
    chmod 600 "$CONFIG"
    echo "# Keyringer config file." > "$CONFIG"
    echo "" >> "$CONFIG"
  fi

  keyringer_config_load_preferences
}

# Load config preferences
function keyringer_config_load_preferences {
  # Load custom keyring preferences
  if [ ! -z "$PREFERENCES" ] && [ -f "$PREFERENCES" ]; then
    source "$PREFERENCES"
  elif [ ! -z "$PREFERENCES" ]; then
    touch $PREFERENCES
  fi
}

# Load a parameter from config
function keyringer_config {
  if [ -z "$CONFIG" ]; then
    echo "Your have to set CONFIG variable in the code"
    exit 1
  elif [ -e "$CONFIG" ]; then
    grep -e "^$1=" "$CONFIG" | tail -n 1 | cut -d = -f 2 | sed -e 's/"//g' -e "s/'//g" | sed -e 's/ *#.*$//'
  else
    echo "Config file not found: $CONFIG"
    exit 1
  fi
}

# Return the list of recipients
function keyringer_recipients {
  grep -v '^#' "$1" | grep -v '^$' | awk '{ print "-r " $2 }' | xargs
}

# Check if keyringer has a given action
function keyringer_has_action {
 if [ -z "$ACTIONS" ]; then
   echo "Your have to set ACTIONS variable in the code"
   exit 1
 fi

 if [ -e "$ACTIONS/$1" ] && [ ! -d "$ACTIONS/$1" ]; then
   true
 else
   false
 fi
}

# Execute an action
function keyringer_exec {
  # Setup
  action="$1"
  basedir="$2"
  shift 2

  # Dispatch
  if keyringer_has_action "$action"; then
    "$ACTIONS/$action" "$basedir" $*
    err="$?"
    if [ "$err" != "0" ]; then
      exit "$err"
    fi
  fi
}

# Return a filename with correct extension
function keyringer_filename {
  if [ -z "$1" ]; then
    return
  else
    printf "%s/%s.asc\n" "$(dirname "$1")" "$(basename "$1" .asc)"
  fi
}

# Check if a folder is inside a git repository
function keyringer_is_git {
  if [ -z "$1" ]; then
    false
  elif [ ! -d "$1" ]; then
    false
  elif [ -d "$1/.git" ]; then
    true
  else
    ( cd "$1" && git status &> /dev/null )

    if [ "$?" != "128" ]; then
      true
    else
      false
    fi
  fi
}

# Check the security of a temporary folder
function keyringer_check_tmp {
  local path="$1"
  local mount

  # Mode check
  if [ -z "$path" ] || [ ! -d "$path" ] || [ ! -w "$path" ] || [ ! -x "$path" ]; then
    return 1
  fi

  # Ramdisk check
  mount="`df "$path" | sed -n '$p' | awk '{ print $NF }'`"
  mount -l -t tmpfs | awk '{ print $3 }' | grep -q -e "^$mount$"
}

# Setup a temporary file
function keyringer_set_tmpfile {
  local tmp
  local candidate
  local candidates="$TMPDIR $TMP /tmp /run/shm"

  if [ -z "$BASEDIR" ]; then
    echo "Please set BASEDIR before creating a tmp file"
    exit 1
  fi

  # Ramdisk check
  for candidate in $candidates; do
    if keyringer_check_tmp $candidate; then
      tmp="$candidate/keyringer.`whoami`"
      break
    fi
  done

  # Set base temp folder
  if [ -z "$tmp" ]; then
    echo "WARNING: neither one of $candidates is mounted in a tmpfs/ramdisk, using $BASEDIR/tmp as fallback."
    echo "Make sure that $BASEDIR is atop of an encrypted volume."
    echo "Press any key to continue, Ctrl-C to abort"
    read key
    tmp="$BASEDIR/tmp"

    # Just to be sure
    keyringer_git_ignore 'tmp/*'
  fi

  # Determine template
  if [ -z "$1" ]; then
    template="$tmp/keyringer.XXXXXXXXXX"
  else
    template="$tmp/XXXXXXXXXX.$1"
  fi

  mkdir -p "$tmp"

  if [ "$2" == "-d" ]; then
    TMPWORK="$(mktemp -d "$template")"
  else
    TMPWORK="$(mktemp "$template")"
  fi

  if [ "$?" != "0" ]; then
    printf "Error: can't set TMPWORK %s\n" "$TMPWORK"
    exit 1
  fi

  trap "keyringer_unset_tmpfile $TMPWORK; exit" INT TERM EXIT
}

# Shred files
function keyringer_shred {
  local path="$1"
  local tool
  local message="Removing"

  if [ -z "$path" ]; then
    return
  elif [ ! -e "$path" ]; then
    return
  fi

  # Get shred implementation
  if which wipe &> /dev/null; then
    tool="wipe"
  elif which shred &> /dev/null; then
    tool="shred"
  else
    # Worst implementation
    message="WARNING $message"
    tool="rm"
  fi

  echo "$message $path using $tool..."

  if [ -d "$path" ]; then
    if [ "$tool" == "wipe" ] || [ "$tool" == "rm" ]; then
      $tool -rf $path
    else
      find $path -exec $tool -uf {} \;
    fi
  else
    if [ "$tool" == "wipe" ] || [ "$tool" == "rm" ]; then
      $tool -f "$path"
    else
      $tool -uf "$path"
    fi
  fi
}

# Remove a temporary file
function keyringer_unset_tmpfile {
  if [ -z "$1" ]; then
    echo "No tmp file set"
  fi

  keyringer_shred "$1"

  if [ "$?" != "0" ]; then
    echo "Warning: could not delete file $1. Please delete it manually as it might have sensitive information."
    exit 1
  fi
}

# Add a pattern into gitignore
function keyringer_git_ignore {
  if [ ! -z "$BASEDIR/.gitignore" ]; then
    echo "$1" > "$BASEDIR/.gitignore"
    keyringer_exec git "$BASEDIR" add .gitignore
  else
    if ! grep -q -e "^$1$" "$BASEDIR/.gitignore"; then
      echo "$1" >> "$BASEDIR/.gitignore"
    fi
  fi
}

# Set needed environment variables and do basic checks.
function keyringer_set_env {
  if [ -z "$1" ]; then
    echo "Error: missing arguments for keyringer_set_env"
    exit 1
  fi

  ACTIONS="`dirname $0`"
  BASENAME="`basename $0`"
  BASEDIR="$1"
  SUBCOMMAND="$2"
  KEYDIR="$BASEDIR/keys"
  RECIPIENTS_BASE="config/recipients"
  RECIPIENTS="$BASEDIR/$RECIPIENTS_BASE"
  OPTIONS="$BASEDIR/config/options"
  VERSION_INFO="$BASEDIR/config/version"

  if [ -z "$BASEDIR" ]; then
    keyringer_action_usage
    exit 1
  fi

  if [ ! -e "$RECIPIENTS" ]; then
    echo "No recipient config was found"
    exit 1
  fi

  if [ -z "$EDITOR" ]; then
    if type sensible-editor > /dev/null 2>&1 ; then
      EDITOR=sensible-editor
    elif type editor > /dev/null 2>&1 ; then
      EDITOR=editor
    else
      echo "You have to set EDITOR env variable"
      exit 1
    fi
  fi

  # Avoid viminfo, see https://keyringer.pw/trac/ticket/50
  if $EDITOR --help | grep -q -e "^VIM"; then
    if ! echo $EDITOR | grep -q -- "-i NONE"; then
      EDITOR="$EDITOR -S $SHARE/editors/vim"
    fi
  fi

  if [ ! -f "$OPTIONS" ]; then
    echo "No option config was found"
    exit 1
  fi

  if [ ! -z "$KEYID" ]; then
    GPG="gpg --quiet -u $KEYID"
  else
    GPG="gpg --quiet"
  fi

  # Check keyring config version
  keyringer_check_version

  # Upgrade configuration
  keyringer_upgrade

  # Check repository integrity
  if [ "$BASENAME" == "check" ]; then
    keyringer_check_repository
  fi

  # Check recipients file
  keyringer_check_recipients $SUBCOMMAND

  # Ensure that keydir exists
  mkdir -p "$KEYDIR" && chmod 700 "$KEYDIR"
}

# Configuration version tracking to help keyring upgrades
function keyringer_check_version {
  if [ "$KEYRINGER_CHECK_VERSION" == "false" ]; then
    if [ -f "$VERSION_INFO" ]; then
      VERSION="`cat $VERSION_INFO`"
    else
      VERSION=""
    fi

    return
  fi

  if [ ! -f "$VERSION_INFO" ]; then
    echo "Configuration version file not found, trying to pull from remotes..."
    # Do not use keyringer_exec as it would trigger keyringer_check_version again
    ( cd "$BASEDIR" && git pull )

    if [ ! -f "$VERSION_INFO" ]; then
      echo "Creating configuration version file..."
      echo 0 > "$VERSION_INFO"
      if keyringer_is_git "$BASEDIR"; then
        keyringer_exec git "$BASEDIR" add config/version
        echo "Pushing configuration version file to remotes..."
        for remote in "$BASEDIR/.git/refs/remotes/*"; do
          keyringer_exec git "$BASEDIR" push $remote master
        done
      fi
    fi
  fi

  VERSION="`cat $VERSION_INFO`"

  # Check if config version is supported by keyringer
  if [ "$VERSION" != "$CONFIG_VERSION" ]; then
    echo "Configuration version differs from keyringer version, trying to pull from remotes"
    # Do not use keyringer_exec as it would trigger keyringer_check_version again
    ( cd "$BASEDIR" && git pull )

    if [ "$VERSION" != "$CONFIG_VERSION" ]; then
      NEWEST="`echo -e "$VERSION\n$CONFIG_VERSION" | sort -V | tail -n 1`"
      if [ "$NEWEST" == "$VERSION" ]; then
        echo "Fatal: config version: $CONFIG_VERSION / config version: $VERSION"
        echo "Please upgrade your keyringer application"
        exit 1
      fi
    fi
  fi
}

# Configuration upgrades
function keyringer_upgrade {
  # Variable used to hold applied version upgrades
  local version="$VERSION"

  if [ "$KEYRINGER_CHECK_VERSION" == "false" ]; then
    return
  fi

  # Upgrade 0.1
  if [ "$version" == "0" ]; then
    if [ ! -d "$RECIPIENTS" ]; then
      echo "Converting recipients to the new scheme..."
      mv $RECIPIENTS $RECIPIENTS.tmp
      mkdir $RECIPIENTS
      mv $RECIPIENTS.tmp $RECIPIENTS/default
      keyringer_exec git "$BASEDIR" add $RECIPIENTS_BASE/default
      keyringer_exec git "$BASEDIR" commit -m "Config-upgrade-0.1"
    fi

    # Done 0.1 upgrade
    echo "0.1" > $VERSION_INFO
    version="0.1"
  fi

  # Upgrade 0.X
  #if [ "$version" == "0.1" ]; then
  #  echo "Upgrading to 0.X config format..."
  #
  #  # Done 0.X upgrade
  #  echo "0.X" > $VERSION_INFO
  #  version="0.X"
  #fi

  # Update version information
  if [ "$CONFIG_VERSION" != "$VERSION" ]; then
    echo $CONFIG_VERSION > $VERSION_INFO
    keyringer_exec git "$BASEDIR" add config/version
    keyringer_exec git "$BASEDIR" commit -m "Config-update-$CONFIG_VERSION"
    echo "Upgrade to version $CONFIG_VERSION completed, pushing to remotes..."
    for remote in "$BASEDIR/.git/refs/remotes/*"; do
      keyringer_exec git "$BASEDIR" push $remote master
    done
  fi
}

# Get an option
#
# Given that options are shared among users through the
# repository, we can't just "source $OPTIONS" as we would
# be opening a simple arbitrary code execution hole.
#
# TODO
function keyringer_get_option {
  false
}

# Get a file argument
function keyringer_get_file {
  FILE="$(keyringer_filename "$RELATIVE_PATH/$1")"

  if [ -z "$FILE" ]; then
    keyringer_action_usage
    exit 1
  elif [ ! -f "$KEYDIR/$FILE" ]; then
    # Try to find a similar file
    count=0
    candidates=(`keyringer_exec find "$BASEDIR" | grep -i "$1" | grep -e '.asc$'`)

    if [ ! -z "$candidates" ]; then
      echo "Could not find exact match for \"$1\", please choose one of the following secrets:"
      echo ""

      for candidate in ${candidates[@]}; do
        echo -e "\t[$count] $candidate"
        let count++
      done

      echo ""
      read -p "Enter option (Ctrl-C to abort): " option

      if [[ "$option" =~ ^[0-9]+$ ]] && [ ! -z "${candidates[$option]}" ]; then
        FILE="$(keyringer_filename "$RELATIVE_PATH/${candidates[$option]}")"
      else
        echo "Invalid option"
        exit 1
      fi
    else
      echo "File not found: $KEYDIR/$FILE"
      exit 1
    fi
  fi
}

# Get a new file argument
function keyringer_get_new_file {
  # File must not contain spaces
  if [ ! -z "$2" ] ; then
    FILE="`echo "$*" | sed -e 's/ /_/g'`"
  else
    FILE="$1"
  fi

  # Sanitize and complete file name
  FILE="`echo $FILE | sed -e 's/[^A-Za-z0-9.\/\-]/_/g'`"

  # Warn user about file name change
  if [ "`basename "$*"`" != "`basename $FILE`" ]; then
    echo "Sanitizing destination filename to `basename $FILE`"
  fi

  # Complete file name
  FILE="$RELATIVE_PATH/$(keyringer_filename "$FILE")"

  if [ -z "$*" ]; then
    keyringer_action_usage
    exit 1
  fi
}

# Get a command argument
function keyringer_get_command {
  # Aditional parameters
  COMMAND="$1"

  if [ -z "$COMMAND" ]; then
    keyringer_action_usage command
    exit 1
  fi
}

# Run the action usage
function keyringer_action_usage {
  if [ "`type -t "keyringer_usage_$BASENAME"`" == "function" ]; then
    # Use custom action usage
    "keyringer_usage_$BASENAME"
  else
    # Default usage
    if [ "$1" == "command" ]; then
      echo "Usage: keyringer <keyring> $BASENAME <command> [arguments]"
    else
      echo "Usage: keyringer <keyring> $BASENAME <file>"
    fi
  fi
}

# Return available actions
function keyringer_show_actions {
  ls -C $ACTIONS
}

# Usage
function keyringer_usage {
  local keyrings="$(ls --color=never `dirname $CONFIG` | sed -e 's/config//' | xargs)"

  printf "Keyringer $KEYRINGER_VERSION\n"
  printf "Usage: keyringer <keyring> <action> [arguments]\n\n"

  # Display only when not in a keyring context
  if [ ! -z "$keyrings" ] && [ -z "$1" ]; then
    printf "Available keyrings: %s \n" "$keyrings"
  fi

  # Show available actions
  printf "Available actions: \n\n"
  if [ ! -z "$keyrings" ] && [ -z "$1" ]; then
    printf "\tinit <path> [remote]\n" $BASENAME
  fi
  keyringer_show_actions | sed -e 's/^/\t/'
  printf "\n"
}

# Check repository integrity
function keyringer_check_repository {
  # Check if it's a git repository
  if [ ! -d "$BASEDIR/.git" ]; then
    echo "Fatal: not a git repository: $BASEDIR"
    exit 1
  fi

  # Git maintenance operations
  echo "Running git maintenance operations..."
  keyringer_exec git "$BASEDIR" fsck
  keyringer_exec git "$BASEDIR" gc
  echo ""

  # Sync the repository
  if [ "`keyringer_exec git "$BASEDIR" remote | wc -l`" != "0" ]; then
    echo "Syncing git repository..."
    keyringer_exec git "$BASEDIR" pull
    echo ""
  fi
}

# Receive keys from keyservers
# TODO: gpg-maintenance trickery
# TODO: should be controlled by user preference
function keyringer_recv_keys {
  local recipient="$1"

  echo "Trying to receive missing key $recipient..."
  gpg --batch --recv-keys "$recipient"
}

# Refresh keys from keyserver
# TODO: gpg-maintenance trickery
# TODO: should be controlled by user preference
function keyringer_refresh_keys {
  local recipient="$1"

  echo "Trying to refresh key $recipient..."
  gpg --batch --recv-keys "$recipient"
}

# Check recipient size
function keyringer_check_recipient_size {
  local recipient="$1"
  local size=$(echo "$recipient" | wc -c)

  if (( $size < 41 )); then
    echo "Fatal: please set the full OpenPGP fingerprint for key ID $recipient:"
    cat <<-EOF

Please provide a full OpenPGP fingerprint, for example:

  john@doe.com ABCD1234ABCD12345678ABCD1234ABCD12345678

Short key ids (for example, DEADBEEF or DECAF123) are not allowed in
recipient files because they are easy to spoof. Researchers have proven
that it is possible to build fake keys to match any possible short key
id by using a few gigabytes of disk space, and a day of computation on
common hardware.

Otherwise, the encryption can be broken, if someone spoofs a short key
id, and causes a participant in a keyringer repository to encrypt
secrets to a fake key.
EOF
   exit 1
 fi
}

# Check recipients
function keyringer_check_recipients {
  # Shall we check recipients?
  if [ "$KEYRINGER_CHECK_RECIPIENTS" == "false" ]; then
    return
  fi

  # Local variables
  local processed=":"

  # Check if recipients file is empty.
  if [ "`grep -vE "^#|^$" "$RECIPIENTS"/* | wc -l`" == 0 ] && [ "$SUBCOMMAND" != "edit" ]; then
    echo "Fatal: no recipients configured for this keyring."
    echo "Please edit your recipients file first."
    exit 1
  fi

  # Check recipients header for updates.
  if grep -qe ' XXXXXXXX$' "$RECIPIENTS"/*; then
    echo "Updating recipients file..."
    sed -i -e 's/ XXXXXXXX$/ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/' "$RECIPIENTS"/*
  fi

  if [ "$1" == "edit" ]; then
    # Don't do the other checks at edit mode.
    return
  fi

  for recipient in $(cat "$RECIPIENTS"/* | grep -v '^#' | awk '{ print $2 }'); do
    # Process a recipient just once
    if echo $processed | grep -q "$recipient:"; then
      continue
    else
      processed="$processed$recipient:"
    fi

    # Check recipient size
    keyringer_check_recipient_size "$recipient"

    # Check if key is present
    keyringer_check_recipient_key "$recipient"

    # Refresh keys
    if [ "$BASENAME" == "check" ] && [ "$refresh" != "no" ]; then
      keyringer_refresh_keys "$recipient"
      echo ""
    fi

    # Check key expiration
    keyringer_check_expiration "$recipient"
  done
}

# Check if a key is present
function keyringer_check_recipient_key {
  local recipient="$1"

  gpg --list-key "$recipient" &> /dev/null
  if [ "$?" != "0" ]; then
    if [ "$BASENAME" == "check" ]; then
      refresh="no"
      keyringer_recvs_keys "$recipient"
      if [ "$?" != 0 ]; then
        echo "Error fetching $recipient from keyservers."
        continue
      fi
      echo ""
    else
      echo "Fatal: no such key $recipient on your GnuPG keyring."
      echo "Please retrieve this key yourself or fix the recipient file."

      exit 1
    fi
  fi
}

# Check key expiration
function keyringer_check_expiration {
  # Variables
  local recipient="$1"
  local not_expired="0"

  # Current date
  seconds="`date +%s`"

  # Check the main key
  expiry="`gpg --with-colons --fixed-list-mode --list-keys "$recipient" | grep ^pub | cut -d : -f 7`"

  # TODO: Time to expire can be configured via repository options.
  ahead="$((86400 * 30 + $seconds))"

  # Check if key is expired
  if [ ! -z "$expiry" ] && [[ "$seconds" -gt "$expiry" ]]; then
    echo "Fatal: primary key for $recipient expired on `date --date="@$expiry"`"
    exit 1
  fi

  # Check if key is about to expire
  # TODO: Users can be alerted by mail if configured by user preferences.
  # TODO: Outgoing emails can be encrypted.
  if [ "$BASENAME" == "check" ] && [ ! -z "$expiry" ] && [[ "$ahead" -gt "$expiry" ]]; then
    echo "Warning: key $recipient will expire soon, on `date --date="@$expiry"`"
  fi

  # Check the subkeys
  expiry=""
  for expiry in `gpg --with-colons --fixed-list-mode --list-keys "$recipient" | grep ^sub | cut -d : -f 7`; do
    if [[ "$seconds" -lt "$expiry" ]]; then
      not_expired="1"

      if [[ "$ahead" -gt "$expiry" ]] && [ "$BASENAME" == "check" ]; then
        echo "Warning: subkey from $recipient will expire soon, on `date --date="@$expiry"`"
      fi
    fi
  done

  # All subkeys are expired
  if [ ! -z "$expiry" ] && [ "$not_expired" != "1" ]; then
    echo "Fatal: key $recipient has no keys suitable for encryption: all subkeys expired."
    exit 1
  fi
}

# Set recipients
function keyringer_set_recipients {
  if [ -z "$1" ]; then
    keyringer_set_default_recipients
  else
    candidate="$1"
    candidate_no_extension="`echo $1 | sed -e 's/.asc$//'`"

    # Find the first matching recipient
    while [ ! -z "$candidate" ] && [ "$candidate" != "." ] && [ "$candidate" != "/" ] && [ "$candidate" != "/." ]; do
      if [ -e "$RECIPIENTS/$candidate" ]; then
        RECIPIENTS_FILE="$RECIPIENTS/$candidate"
        RECIPIENTS_FILE_BASE="$RECIPIENTS_BASE/$candidate"
        return
      elif [ -e "$RECIPIENTS/$candidate_no_extension" ]; then
        RECIPIENTS_FILE="$RECIPIENTS/$candidate_no_extension"
        RECIPIENTS_FILE_BASE="$RECIPIENTS_BASE/$candidate_no_extension"
        return
      fi

      candidate="`dirname $candidate`"
    done

    keyringer_set_default_recipients "$1"

  fi
}

# Set default recipients
function keyringer_set_default_recipients {
  if [ -e "$RECIPIENTS/default" ]; then
    RECIPIENTS_FILE="$RECIPIENTS/default"
    RECIPIENTS_FILE_BASE="$RECIPIENTS_BASE/default"
  else
    echo "Fatal: no suitable recipient file found for path $1"
    exit 1
  fi
}

# Set a new recipient, avoid file checks
function keyringer_set_new_recipients {
  if [ -z "$1" ]; then
    keyringer_set_default_recipients
  else
    RECIPIENTS_FILE="$RECIPIENTS/$1"
    RECIPIENTS_FILE_BASE="$RECIPIENTS_BASE/$1"
  fi
}

# Create a new recipients file
function keyringer_create_new_recipients {
  local recipients="$1"
  local recipient
  local key
  local uid
  local fpr

  if [ ! -e "$recipients" ]; then
    mkdir -p "`dirname $recipients`"
    echo "# Use entries in the form of 'john@doe.com XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'" > "$1"
    echo "" >> "$recipients"

    # Try to get an initial recipient
    if [ -e "$HOME/.gnupg/gpg.conf" ]; then
      recipient="`grep -e "^default-key" ~/.gnupg/gpg.conf | cut -d ' ' -f 2`"

      if [ ! -z "$recipient" ]; then
        key="`gpg --fingerprint --with-colons $recipient 2> /dev/null`"

        if [ "$?" == "0" ]; then
          fpr="`echo "$key" | grep -e '^fpr:' | head -1 | cut -d : -f 10`"
          uid="`echo "$key" | grep -e '^uid:' | head -1 | cut -d : -f 10 | sed -e 's|^[^<]*<||' -e 's|>$||'`"

          if [ ! -z "$uid" ] && [ ! -z "$fpr" ]; then
            echo "Default key $fpr ($uid) found at ~/.gnupg/gpg.conf, using as initial recipient."
            echo "$uid $fpr" >> "$recipients"
          fi
        fi
      fi
    fi
  fi
}

# Setup environment
if [ "$(basename "$0")" != "keyringer" ]; then
  keyringer_config_load_preferences
  keyringer_set_env $*
fi