Authentication.Rmd

---
title: "Authentication"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Authentication}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>", 
  results= 'markup'
)
```

Out of the box RestRserve provides two authentication schemas: [`Basic`](https://swagger.io/docs/specification/authentication/basic-authentication/) and [`Bearer`](https://swagger.io/docs/specification/authentication/bearer-authentication/).

## Basic

**Note that Basic authentication, should only be used over HTTPS (SSL) or within secure network.** In HTTP protocol `Authorization` header (as well as other parts of the HTTP request) are plain text and are not encrypted!

According to `AuthBackendBasic` documentation first of all we need to provide an authentication function. It should take 2 arguments - `user` and `password` and return `logical` value - whether access is allowed for a given user  or not.
```{r}
library(RestRserve)

allowed_access = list(
  "user-1" = "password-1",
  "user-2" = "password-2"
)

auth_fun = function(user, password) {
  res = FALSE
  try({
    res = identical(allowed_access[[user]], password)
  }, silent = TRUE)
  return(res)
}
```

Now we can create authentication backend.

```{r}
basic_auth_backend = AuthBackendBasic$new(FUN = auth_fun)
```

Now let's create application which requires authorization in order to use `/secure/factorial` endpoint:
```{r}

auth_mw = AuthMiddleware$new(
  auth_backend = basic_auth_backend, 
  routes = "/secure/factorial", 
  id = "auth_middleware"
)

app = Application$new(middleware = list(auth_mw))
```
Let's add two endpoints - first public (`/factorial`) and second with restricted access (`/secure/factorial`):
```{r}
factorial_handler = function(.req, .res) {
  x = .req$get_param_query("x")
  x = as.integer(x)
  .res$set_body(factorial(x))
}
app$add_get("/factorial", factorial_handler)
app$add_get("/secure/factorial", factorial_handler)
```

As we can see first endpoint doesn't require any authentication:
```{r}
req = Request$new(path = "/factorial", parameters_query = list(x = "5"))
res = app$process_request(req)
res$body
```

Let's try to send a request without credentials to the second endpoint:
```{r}
req = Request$new(path = "/secure/factorial", parameters_query = list(x = "5"))
res = app$process_request(req)
res$body
```
As expected this gives `405` error.

Now let's add correct credentials:
```{r}
credentials = jsonlite::base64_enc("user-1:password-1")
headers = list("Authorization" = sprintf("Basic %s", credentials))

req = Request$new(
  path = "/secure/factorial", 
  parameters_query = list(x = "5"), 
  headers = headers
)

res = app$process_request(req)
res$body
```
Success!

Let's see what happens if password is wrong:
```{r}
credentials = jsonlite::base64_enc("user-1:password-2")
headers = list("Authorization" = sprintf("Basic %s", credentials))

req = Request$new(
  path = "/secure/factorial", 
  parameters_query = list(x = "5"), 
  headers = headers
)

res = app$process_request(req)
res$body
```

## Bearer

`Bearer` authentication (also called "token" authentication) is an HTTP authentication scheme that involves security tokens called bearer tokens. The name "Bearer authentication" can be understood as "give access to the bearer of this token." The bearer token is a cryptic string, usually generated by the server in response to a login request. The client must send this token in the Authorization header when making requests to protected resources.

The `Bearer` authentication scheme was originally created as part of `OAuth 2.0` in [RFC 6750](https://datatracker.ietf.org/doc/html/rfc6750), but is sometimes also used on its own. Similarly to Basic authentication, Bearer authentication should only be used over HTTPS (SSL).


```{r}


allowed_tokens = c(
  "super_secure_token_1",
  "super_secure_token_2"
)

auth_fun = function(token) {
  res = FALSE
  try({
    res = token %in% allowed_tokens
  }, silent = TRUE)
  return(res)
}
basic_auth_backend = AuthBackendBearer$new(FUN = auth_fun)

```

As an alternative to requiring authentication for a single endpoint we can make it mandatory for all endpoints which start with certain pattern:
```{r}
auth_mw = AuthMiddleware$new(
  auth_backend = basic_auth_backend, 
  routes = "/secure/", 
  match = "partial",
  id = "auth_middleware"
)
app = Application$new(middleware = list(auth_mw))
```

For example:

```{r}
app$add_get("/hello0", function(req, res) {res$body = "OK"})
app$add_get("/secure/hello1", function(req, res) {res$body = "OK"})
app$add_get("/secure/hello2", function(req, res) {res$body = "OK"})
```

Request with valid token to `/secure/hello1`:
```{r}
headers = list("Authorization" = "Bearer super_secure_token_1")
req = Request$new(
  path = "/secure/hello1", 
  headers = headers
)

res = app$process_request(req)
res$body
```
Request with invalid token to `/secure/hello2`:
```{r}
headers = list("Authorization" = "Bearer abcd")
req = Request$new(
  path = "/secure/hello2", 
  headers = headers
)

res = app$process_request(req)
res$body
```
Request to endpoint which doesn't require authorization: `/hello0`:
```{r}
req = Request$new(path = "/hello0")
res = app$process_request(req)
res$body
```