% A Tool to Manage a Set of YAML Objects Representing Account Information — pwutil

A long time ago I wrote a bunch of scripts (first in bash, then zsh, and later perl) to manage a, sometimes encrypted, file containing account information I get asked to create and remember on a daily basis—accounts for shopping websites spring to mind.

[pwutil](git://git.yggdrasil.li/pwutil) is the newest iteration in this line of bunches of scripts.

## Features

  * Support for embedding common operation in any kind of record keeping

    Thus support for almost any encryption known to man (with absolutely no online security), version control, and synchronisation
  * [Human readable](https://en.wikipedia.org/wiki/YAML) backstore
  * [Command Line Interface](https://en.wikipedia.org/wiki/Command-line_interface)-only
  * New accounts can be partially generated by user defined functions with out of the box support for [pwgen](http://sourceforge.net/projects/pwgen/) and SSH

## Documentation

I shall document the project in a partial and file-wise fashion—amendments available on request.

### Structure

~~~ {#DirTree}
pwutil
├── default.nix
├── PWAdd.hs
├── PWGet.hs
├── PWUtil
│   ├── Encfs.hs
│   ├── Extra
│   │   ├── PWGen.hs
│   │   └── SSHCmd.hs
│   ├── Types.hs
│   └── Util.hs
├── pwutil.hs
├── PWUtil.hs
└── pwutil.nix
~~~

### `pwutil.nix`
is a [nix](https://nixos.org/nix) expression allowing easy installation using the nix package manager.
A `~/.nixpkgs/config.nix` allowing one to do so might look thus:

~~~ {.numberLines}
{
  packageOverrides = pkgs: {
    pwutil = pkgs.callPackage /path/to/pwutil.nix {};
  };
}
~~~

### `Types.hs`

`PWLocation` describes the location of a file containing a YAML object mapping human readable identifiers to account information.
`encryption`, which has essentially the same signature as [`withFile`](http://hackage.haskell.org/package/base-4.8.0.0/docs/System-IO.html#v:withFile) wraps all access to the file.
This in an extremely powerful way to deal with any kind of encryption desired (currently I implemented automatic mounting of an [EncFs](http://en.wikipedia.org/wiki/EncFS) container and `plain`, which does nothing.
`create` is used to try and create the location once should access fail due to a file [not existing](http://hackage.haskell.org/package/base-4.8.0.0/docs/System-IO-Error.html#v:doesNotExistErrorType).

~~~ {#Types.hs .haskell .numberLines}
module PWUtil.Types (
  PWLocation(..),
  Encryption(..),
  PW(..),
  PWConfig(..),
  Generator(..)
  ) where

import System.IO (Handle(..), IOMode(..))
import Control.Monad.State
import qualified Data.Map as M
import Data.Yaml

data PWLocation = PWLocation
                  { path :: FilePath
                  , encryption :: Encryption
                  , create :: IO ()
                  }

instance Show PWLocation where
  show loc = show $ path loc

type Encryption = FilePath -> IOMode -> (Handle -> IO ()) -> IO ()

type PW = StateT PWConfig IO

data PWConfig = PWConfig
               { location :: PWLocation
               , generators :: M.Map String Generator
               }

type Generator = [String] -> IO Value
~~~


### `pwutil.hs`

is, in a [xmonad](http://xmonad.org) kind of way, the configuration file.

~~~ {#pwutil.hs .haskell .numberLines}
import PWUtil

import System.FilePath ((</>))
import qualified Data.Map as M
import System.Directory (getHomeDirectory)

pWLocation :: IO PWLocation
pWLocation = do
  h <- getHomeDirectory
  return PWLocation { path = h </> "accounts.yaml"
                    , encryption = plain
                    , create = createFile $ h </> "accounts.yaml"
                    }

myGenerators :: M.Map String Generator
myGenerators = M.empty

main :: IO ()
main = do
  myLocation <- pWLocation
  runPW (PWConfig { location = myLocation, generators = myGenerators }) pwutil
~~~

### `Encfs.hs`

shall serve as an example for a module providing an encryption wrapper.
It exports

~~~{.haskell}
encfs :: Encfs -> Encryption
encfs (Encfs backStore mountpoint) = …
~~~

Upon execution it checks whether `mountpoint` is already mounted.
If not it executes `encfs backStore mountpoint` interactively and calls `fusermount -u` after completion.