Introducing shinyauthr

Installation

Install the package from github with devtools.

devtools::install_github("paulc91/shinyauthr")

Example

Below is a live example of shinyauthr in action within a shinydashboard UI.

Usage

The package provides 2 module functions each with a UI and server element:

• login
• loginUI
• logout
• logoutUI

Below is a minimal reproducible example of how to use the authentication modules in a shiny app. Note that you must initiate the use of the shinyjs package with shinyjs::useShinyjs() in your UI code for this to work appropriately.

library(shiny)
library(shinyauthr)
library(shinyjs)

# dataframe that holds usernames, passwords and other user data
user_base <- data.frame(
  user = c("user1", "user2"),
  password = c("pass1", "pass2"), 
  permissions = c("admin", "standard"),
  name = c("User One", "User Two"),
  stringsAsFactors = FALSE
)

ui <- fluidPage(
  # must turn shinyjs on
  shinyjs::useShinyjs(),
  # add logout button UI 
  div(class = "pull-right", shinyauthr::logoutUI(id = "logout")),
  # add login panel UI function
  shinyauthr::loginUI(id = "login"),
  # setup table output to show user info after login
  tableOutput("user_table")
)

server <- function(input, output, session) {
  
  # call the logout module with reactive trigger to hide/show
  logout_init <- callModule(shinyauthr::logout, 
                            id = "logout", 
                            active = reactive(credentials()$user_auth))
  
  # call login module supplying data frame, user and password cols
  # and reactive trigger
  credentials <- callModule(shinyauthr::login, 
                            id = "login", 
                            data = user_base,
                            user_col = user,
                            pwd_col = password,
                            log_out = reactive(logout_init()))
  
  # pulls out the user information returned from login module
  user_data <- reactive({credentials()$info})
  
  output$user_table <- renderTable({
    # use req to only render results when credentials()$user_auth is TRUE
    req(credentials()$user_auth)
    user_data()
  })
}

shinyApp(ui = ui, server = server)

Details

When the login module is called, it returns a reactive list containing 2 elements:

• user_auth
• info

The initial values of these variables are FALSE and NULL respectively. However, given a data frame or tibble containing user names, passwords and other user data (optional), the login module will assign a user_auth value of TRUE if the user supplies a matching user name and password. The value of info then becomes the row of data associated with that user which can be used in the main to control content based on user permission variables etc.

The logout button will only show when user_auth is TRUE. Clicking the button will reset user_auth back to FALSE which will hide the button and show the login panel again.

You can set the code in your server functions to only run after a successful login through use of the req() function inside all reactives, renders and observers. In the example above, using req(credentials()$user_auth) inside the renderTable function ensures the table showing the returned user information is only rendered when user_auth is TRUE.

Hashing Passwords with digest

⊕Note: your plain text passwords must be a character vector, not factors, prior to hashing for this to work as shiny inputs are passed as character strings.

If you are hosting your user passwords on the internet, it is a good idea to first encrypt them with a hashing algorithm. You can use the digest package to do this. You can then tell the shinyauthr::login module that your passwords are hashed and what algorithm you used when hashing with digest.

For example, a sample user base like the following can be incorporated for use with shinyauthr:

# create a user base then hash passwords with md5 algorithm
# then save to an rds file in app directory
library(digest)

user_base <- data.frame(
  user = c("user1", "user2"),
  password = sapply(c("pass1", "pass2"), digest, "md5"), 
  permissions = c("admin", "standard"),
  name = c("User One", "User Two"),
  stringsAsFactors = FALSE
)

saveRDS(user_base, "user_base.rds")

# in your app code, read in the user base rds file
user_base <- readRDS("user_base.rds")

# then when calling the module, set hashed = TRUE and algo = "md5"
credentials <- callModule(shinyauthr::login, "login", 
                          data = user_base,
                          user_col = user,
                          pwd_col = password,
                          hashed = TRUE,
                          algo = "md5",
                          log_out = reactive(logout_init()))

Use Cases

This isn’t an attempt at a substitute for any of RStudio’s excellent commercial shiny hosting platforms that provide built-in authentication. If you are a company or organisation looking for a secure on-premise solution, definitely opt for one of those.

⊕A Professional shinyapps.io plan could be used in this use-case but I’ve found managing a significant number of users with this to be a little cumbersome and there is currently no https support for custom domains.

However, there are some cases where these options may not be appropriate or feasible. One-off applications for an external client for example, may require authentication and user permissions that control in-app content. Having the option of deploying the app on VM with Shiny Server Open Source and controlling authentication and user permissions with shinyauthr could be a viable, cost-effective solution.

Disclaimer

I’m not a security professional so cannot guarantee this authentication procedure to be foolproof. It is ultimately the shiny app developer’s responsibility not to expose any sensitive content to the client without the necessary login criteria being met.

I would welcome any feedback on any potential vulnerabilities in the process. I know that apps hosted on a server without an SSL certificate could be open to interception of usernames and passwords submitted by a user. As such I would not recommend the use of shinyauthr without an HTTPS connection.

fin

That’s all for now. Issues and pull requests welcome over on the github repo.

a dopo!