R/encryption.R

In KWB-R/kwb.utils: General Utility Functions Developed at KWB

# The functions defined in this file need package "PKI"

# generateKeyFile --------------------------------------------------------------

#' Generate a Decryption Key File
#' 
#' @param target full path to the file to which the key shall be written
#' @export
#' @seealso \code{\link{createPasswordFile}}, \code{\link{getPassword}}
generateKeyFile <- function(target)
{
  checkNamespace("PKI", "generateKeyFile")
  
  PKI::PKI.save.key(key = PKI::PKI.genRSAkey(), target = target) 
}

# checkNamespace ---------------------------------------------------------------

checkNamespace <- function(packageName, functionName)
{
  if (! requireNamespace(packageName, quietly = TRUE)) {
    
    stop(
      "Please install the package ", hsQuoteChr(packageName), " to use ", 
      "this function: ", hsQuoteChr(functionName), call. = FALSE
    )
  }
}

# createPasswordFile -----------------------------------------------------------

#' Create a File Storing a Password in Encrypted Form
#' 
#' @param account optional. Name of account the user is asked to enter the 
#'   password for. Only used for the input prompt.
#' @param keyFile path to the file containing the encryption/decryption key,
#'   as generated by \code{\link{generateKeyFile}}
#' @param passwordFile path to the password file to be created. An existing file
#'   will be overwritten!
#' @param password password for account. If \code{NULL} (default) the user will
#'   be asked to enter the password on the console
#' @export
#' @seealso \code{\link{generateKeyFile}}, \code{\link{getPassword}}
createPasswordFile <- function(
  account = NULL, keyFile, passwordFile, password = NULL
)
{
  checkNamespace("PKI", "createPasswordFile")
  
  password <- defaultIfNULL(password, askForPassword(account))
  
  password.encrypted <- PKI::PKI.encrypt(
    charToRaw(password), key = PKI::PKI.load.key(file = keyFile)
  )
  
  writeBin(password.encrypted, passwordFile)
}

# askForPassword ---------------------------------------------------------------

askForPassword <- function(account = NULL)
{
  clearConsole()

  prompt <- sprintf(
    "Enter password%s: ", 
    if (is.null(account)) "" else paste0("for account '", account, "'")
  )
    
  userInput <- readline(prompt)

  clearConsole()
  
  invisible(userInput)
}

# getPassword ------------------------------------------------------------------

#' Get Encrypted Password from File Using Key
#' 
#' Given the path to a file containing an encrypted password and given the path
#' to the file containing the key that was used to do the encryption this 
#' function returns the original password, invisibly.
#' 
#' @param passwordFile path to the password file, as generated by 
#'   \code{\link{createPasswordFile}}.
#' @param keyFile path to the key file, as generated by 
#'   \code{\link{generateKeyFile}}.
#' @return The password (character) or \code{NA} if no password is stored, both
#'   invisibly.
#' @export
#' @seealso \code{\link{generateKeyFile}}, \code{\link{createPasswordFile}}
getPassword <- function(passwordFile, keyFile) 
{
  checkNamespace("PKI", "getPassword")
  
  if (! file.exists(passwordFile)) {
    
    stop("Password file '", passwordFile, "' does not exist.")  
  }
  
  password.encrypted <- readBin(passwordFile, what = "raw", n = 256)
  
  invisible(rawToChar(PKI::PKI.decrypt(
    what = password.encrypted, 
    key = PKI::PKI.load.key(file = keyFile)
  )))
}