sudo gem install sinatra-basic-auth

require "sinatra"
require "sinatra/basic_auth"

# Specify your authorization logic
authorize do |username, password|
  username == "john" && password == "doe"
end

# Set protected routes
protect do
  get "/admin" do
    "Restricted page that only admin can access"
  end
end

You can specify different authorization logic for different realms.

authorize "Public" do |username, password|
  username == "myapp" && password == "beta"
end

authorize "Admin" do |username, password|
  username == "admin" && password == "a complex password"
end

protect "Public" do
  get "/" do
    "Home page"
  end
end

protect "Admin" do
  get "/admin" do
    "Welcome, Mr. Administrator"
  end
end

If you need to retrieve the credentials:

protect do
  get "/" do
    "Hello, #{auth.credentials.first}"
  end
end

(The MIT License)

Copyright © 2010:

• Nando Vieira (nandovieira.com.br)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ‘Software’), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED ‘AS IS’, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.