How do I tell the API who I am?

️✅ Learning objectives

  • Find authentication information in API docs.
  • Authenticate a request with an API key.
  • Authenticate a request with OAuth.

What is authentication?

Authentication vs Authorization


  • Verifying who you are
  • Uses some sort of “credentials”


  • Granting access based on who you are
  • Both often abbreviated “auth”
  • Often used interchangeably

The HTTP Authorization request header can be used to provide credentials that authenticate a user agent with a server, allowing access to a protected resource. — MDN web docs

Credential dangers


  • How much account control does it have?
    • Can it lock you out?
    • Can it reveal sensitive data?
  • How long does it last?
    • Shorter = safer
    • Can you revoke it?
  • How likely is it to leak?
    • When do you send it?
    • Where do you send it?
    • How often do you send it?

Authentication schemes overview

  • HTTP Basic Authentication: username + password sent with request
  • API Keys/Bearer Tokens: password-like thing sent with request
    • Dirty secret: This is what more complex schemes are, eventually
  • OAuth: Multi-step process to generate a key
    • Goal: Make the key as short-lived as possible
    • Not everyone implements the same way (ie often wrong)
  • Other:

Dangers of leaking credentials

  • 🔴 Username + password
    • Access entire account
    • Often difficult to turn off/recover
  • 🟠 API key
    • Can access everything you can access
    • Sometimes short-lived
    • You can often revoke this
  • 🟡 OAuth exists to minimize these dangers


What are HTTP request headers?

Metadata about the request

  • Authentication
  • Cookies
  • Cache rules
  • Expected response
  • Etc

Names are case-insensitive!


TODO: Leftovers from httr2.qmd. Make it fit in this chapter!

req_fec_auth <- req_fec |> 
  req_headers("X-Api-Key" = "DEMO_KEY", .redact = "X-Api-Key")

Be careful!



  • Replace entire URL
  • eg: Same authentication, different base_url
req_fec_dev_auth <- req_fec_auth |> 

But first: Practice safe git

  • Run usethis::git_vaccinate()
  • Usually ignore project-level .Renviron

What does this API want?

  • Find “OpenAPI” or “Swagger” links (or “API json”, “API yaml”, etc)
    • Search for “secrutitySchemes”
    • Often easier-to-understand details than docs!
  • Might need to do something to “register”
    • “Request an API key”
    • “Register your App” (or “Client”) (see OAuth)

HTTP Basic Authentication

  • httr2::req_auth_basic(req, username, password = NULL)
  • Leave password blank: Prompt interactive semi-securely
  • Avoid using this if you can!
    • I can’t remember any API that only offers this

API Keys & Bearer Tokens

  • httr2::req_auth_bearer_token(req, token) (specific header)
    • Pass token as Sys.get("API_TOKEN_NAME")
    • Save token with usethis::edit_r_environ()
  • Catch-all: httr2::req_headers(.req, ..., .redact = NULL)
    • ... = token_parameter = Sys.get("API_TOKEN_NAME")
    • .redact = "token_parameter" to hide in print

OAuth: Terminology

  • User: You, or someone using your code
  • Client: The thing asking for permission to act as the user
    • Your code, but also
    • A reusable thing that represents your code
    • Client ID: Codename
    • Client secret: Client “password”, but often not very secret
  • Authorization server (auth): Thing granting permission (usually the API owner)
    • Often multiple servers (auth vs auth2 on next slide)
  • Resource server (API): Thing user is using (the API)

The OAuth “dance”

  • User to client: Hit this API for me!
  • Client (ID) to auth: Can I act as this user and do these things?
  • Auth to user: Is this ok?
  • User to auth: Yes
  • Auth to client’s home address: Use this to get a key
  • Client (ID + secret) to auth2: Turn this into a key (I’m really me!)
  • Auth2 to client: Here’s your key (and I’ll log what it can do)
  • Client to API: Here’s my key
  • API to auth: Can this key do this?
  • Auth to API: (checks logged scopes) Yes!
  • API to client: Ok, here’s the info!

TODO: Image of OAuth dance

OAuth credential dangers

  • 🟢 Client id: Like knowing a package name.
  • 🟡 Client secret:
    • Can pretend to be your client, but user still needs to say ok
    • Can your client do anything special?
      • Installed (e.g. Slack app)?
      • API usage limits?
  • 🟡 Authorization code: Unlikely to be an issue
    • Only sent to provided redirect_uri
    • Extremely short lived (often minutes or less)

OAuth credential dangers (cont)

  • 🟡 Refresh token: A longer-lived authorization code
    • Can be used to get a new access token
    • Usually revoked if you auth from scratch
    • Also need client secret to refresh
  • 🟠 Access token: The thing we’re protecting
    • Can do whatever it’s authorized to do
    • Usually easy to revoke
  • 🔴 Username + password: We don’t want to know these


  • Almost definitely only need these (from API provider):
    • id = Client ID
    • token_url = URL where clients exchange authorization codes for tokens
    • secret = Client secret
    • Often auth = "header"
    • If this client has multiple uses: name = unique for this use case
  • Construct once & reuse

OAuth client demo

yt_client <- oauth_client(
  secret = Sys.getenv("YOUTUBE_CLIENT_SECRET")


  • auth_url = URL to get an authorization code (from API)
  • scope = Usually comma-separated string of permissions
  • pkce = Good if supported, often have to turn off
  • redirect_uri = Where to send response
    • Often need specific local port “http://localhost:4242” or “”
    • Must be configured as part of client configuration (at API)
  • cache_disk = Set this TRUE if you can
    • cache_key if you’ll use this client for multiple tokens

Oauth request demo

playlists <- request("") |> 
  req_url_path_append("playlists") |> 
  req_url_query(part = "snippet", mine = TRUE, maxResults = 50) |> 
    scope = "",
    redirect_uri = ""
  ) |> 

Automating OAuth

  • If you can, use httr2 cache: easiest, but
    • auto-deletes when 30 days old
    • fills logs w/ “Caching httr2 token in …” messages
  • httr2::req_oauth_bearer_jwt() if you have JSON web token (service account)
  • httr2::req_oauth_refresh() if you have a refresh token
    • httr2::oauth_flow_auth_code() once to get refresh

Browser cookies

This will feel hacky because it is hacky.

  • Install EditThisCookie browser extension
  • Use API in browser
  • Open EditThisCookie extension
  • Options > “Choose the preferred export format for cookies” > Netscape HTTP Cookie File
  • Open EditThisCookie extension
  • Export
  • Paste into a file at path
  • httr2::req_cookie_preserve(req, path)

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