Add support for email whitelist/blacklist to GitHub auth

If a site is configured for GitHub logins, _**and**_ has an email domain
whitelist, it's possible to get in a state where a new user is locked to
a non-whitelist email (their GitHub primary) even though they have an
alternate email that's on the whitelist.  In all cases, the GitHub
primary email is attempted first so that previously existing behavior
will be the default.

- Add whitelist/blacklist support to GithubAuthenticator (via
  EmailValidator)

- Add multiple email support GithubAuthenticator

- Add test specs for GithubAuthenticator

- Add authenticator-agnostic "none of your email addresses are allowed"
  error message.

config/locales/server.en.yml

@@ -1538,6 +1538,7 @@ en:
     something_already_taken: "Something went wrong, perhaps the username or email is already registered. Try the forgot password link."
     omniauth_error: "Sorry, there was an error authorizing your account. Perhaps you did not approve authorization?"
     omniauth_error_unknown: "Something went wrong processing your log in, please try again."
+    authenticator_error_no_valid_email: "No email addresses associated with %{account} are allowed. You may need to configure your account with a different email address."
     new_registrations_disabled: "New account registrations are not allowed at this time."
     password_too_long: "Passwords are limited to 200 characters."
     email_too_long: "The email you provided is too long. Mailbox names must be no more than 254 characters, and domain names must be no more than 253 characters."

lib/auth/github_authenticator.rb

@@ -1,18 +1,34 @@
+require_dependency 'has_errors'
+
 class Auth::GithubAuthenticator < Auth::Authenticator
 
   def name
     "github"
   end
 
+  class GithubEmailChecker
+    include ::HasErrors
+
+    def initialize(validator, email)
+      @validator = validator
+      @email = Email.downcase(email)
+    end
+
+    def valid?()
+      @validator.validate_each(self, :email, @email)
+      return errors.blank?
+    end
+
+  end
+
   def after_authenticate(auth_token)
     result = Auth::Result.new
 
     data = auth_token[:info]
+    result.username = screen_name = data[:nickname]
+    result.name = data[:name]
 
-    result.username = screen_name = data["nickname"]
-    result.email = email = data["email"]
-
-    github_user_id = auth_token["uid"]
+    github_user_id = auth_token[:uid]
 
     result.extra_data = {
       github_user_id: github_user_id,
@@ -20,20 +36,64 @@ class Auth::GithubAuthenticator < Auth::Authenticator
     }
 
     user_info = GithubUserInfo.find_by(github_user_id: github_user_id)
-    result.email_valid = !!data["email_verified"]
 
     if user_info
+      # If there's existing user info with the given GitHub ID, that's all we
+      # need to know.
       user = user_info.user
-    elsif result.email_valid && (user = User.find_by_email(email))
-      user_info = GithubUserInfo.create(
-          user_id: user.id,
-          screen_name: screen_name,
-          github_user_id: github_user_id
-      )
+      result.email = data[:email],
+      result.email_valid = !!data[:email_verified]
+    else
+      # Potentially use *any* of the emails from GitHub to find a match or
+      # register a new user, with preference given to the primary email.
+      all_emails = Array.new(auth_token[:extra][:all_emails])
+      all_emails.unshift({
+          :email => data[:email],
+          :verified => !!data[:email_verified]
+      })
+
+      # Only consider verified emails to match an existing user.  We don't want
+      # someone to be able to create a GitHub account with an unverified email
+      # in order to access someone else's Discourse account!
+      all_emails.each do |candidate|
+        if !!candidate[:verified] && (user = User.find_by_email(candidate[:email]))
+          result.email = candidate[:email]
+          result.email_valid = !!candidate[:verified]
+          GithubUserInfo.create(
+              user_id: user.id,
+              screen_name: screen_name,
+              github_user_id: github_user_id
+          )
+          break
+        end
+      end
+
+      # If we *still* don't have a user, check to see if there's an email that
+      # passes validation (this includes whitelist/blacklist filtering if any is
+      # configured).  When no whitelist/blacklist is in play, this will simply
+      # choose the primary email since it's at the front of the list.
+      if !user
+        validator = EmailValidator.new(attributes: :email)
+        found_email = false
+        all_emails.each do |candidate|
+          checker = GithubEmailChecker.new(validator, candidate[:email])
+          if checker.valid?
+            result.email = candidate[:email]
+            result.email_valid = !!candidate[:verified]
+            found_email = true
+            break
+          end
+        end
+
+        if !found_email
+          result.failed = true
+          escaped = Rack::Utils.escape_html(screen_name)
+          result.failed_reason = I18n.t("login.authenticator_error_no_valid_email", account: escaped)
+        end
+      end
     end
 
     result.user = user
-
     result
   end
 

spec/components/auth/github_authenticator_spec.rb

@@ -0,0 +1,172 @@
+require 'rails_helper'
+
+# In the ghetto ... getting the spec to run in autospec
+#  thing is we need to load up all auth really early pre-fork
+#  it means that the require is not going to get a new copy
+Auth.send(:remove_const, :GithubAuthenticator)
+load 'auth/github_authenticator.rb'
+
+describe Auth::GithubAuthenticator do
+
+  context 'after_authenticate' do
+
+    it 'can authenticate and create a user record for already existing users' do
+      user = Fabricate(:user)
+
+      hash = {
+        :extra => {
+          :all_emails => [{
+            :email => user.email,
+            :primary => true,
+            :verified => true,
+          }]
+        },
+        :info => {
+          :email => user.email,
+          :email_verified => true,
+          :nickname => user.username,
+          :name => user.name,
+        },
+        :uid => "100"
+      }
+
+      authenticator = Auth::GithubAuthenticator.new
+      result = authenticator.after_authenticate(hash)
+
+      expect(result.user.id).to eq(user.id)
+      expect(result.username).to eq(user.username)
+      expect(result.name).to eq(user.name)
+      expect(result.email).to eq(user.email)
+      expect(result.email_valid).to eq(true)
+    end
+
+    it 'will not authenticate for already existing users with an unverified email' do
+      user = Fabricate(:user)
+
+      hash = {
+        :extra => {
+          :all_emails => [{
+            :email => user.email,
+            :primary => true,
+            :verified => false,
+          }]
+        },
+        :info => {
+          :email => user.email,
+          :email_verified => false,
+          :nickname => user.username,
+          :name => user.name,
+        },
+        :uid => "100"
+      }
+
+      authenticator = Auth::GithubAuthenticator.new
+      result = authenticator.after_authenticate(hash)
+
+      expect(result.user).to eq(nil)
+      expect(result.username).to eq(user.username)
+      expect(result.name).to eq(user.name)
+      expect(result.email).to eq(user.email)
+      expect(result.email_valid).to eq(false)
+    end
+
+    it 'can create a proper result for non existing users' do
+      hash = {
+        :extra => {
+          :all_emails => [{
+            :email => "person@example.com",
+            :primary => true,
+            :verified => true,
+          }]
+        },
+        :info => {
+          :email => "person@example.com",
+          :email_verified => true,
+          :nickname => "person",
+          :name => "Person Lastname",
+        },
+        :uid => "100"
+      }
+
+      authenticator = Auth::GithubAuthenticator.new
+      result = authenticator.after_authenticate(hash)
+
+      expect(result.user).to eq(nil)
+      expect(result.username).to eq(hash[:info][:nickname])
+      expect(result.name).to eq(hash[:info][:name])
+      expect(result.email).to eq(hash[:info][:email])
+      expect(result.email_valid).to eq(hash[:info][:email_verified])
+    end
+
+    it 'will skip blacklisted domains for non existing users' do
+      hash = {
+        :extra => {
+          :all_emails => [{
+            :email => "not_allowed@blacklist.com",
+            :primary => true,
+            :verified => true,
+          },{
+            :email => "allowed@whitelist.com",
+            :primary => false,
+            :verified => true,
+          }]
+        },
+        :info => {
+          :email => "not_allowed@blacklist.com",
+          :email_verified => true,
+          :nickname => "person",
+          :name => "Person Lastname",
+        },
+        :uid => "100"
+      }
+
+      authenticator = Auth::GithubAuthenticator.new
+      SiteSetting.email_domains_blacklist = "blacklist.com"
+      result = authenticator.after_authenticate(hash)
+
+      expect(result.user).to eq(nil)
+      expect(result.username).to eq(hash[:info][:nickname])
+      expect(result.name).to eq(hash[:info][:name])
+      expect(result.email).to eq("allowed@whitelist.com")
+      expect(result.email_valid).to eq(true)
+    end
+
+    it 'will find whitelisted domains for non existing users' do
+      hash = {
+        :extra => {
+          :all_emails => [{
+            :email => "person@example.com",
+            :primary => true,
+            :verified => true,
+          },{
+            :email => "not_allowed@blacklist.com",
+            :primary => true,
+            :verified => true,
+          },{
+            :email => "allowed@whitelist.com",
+            :primary => false,
+            :verified => true,
+          }]
+        },
+        :info => {
+          :email => "person@example.com",
+          :email_verified => true,
+          :nickname => "person",
+          :name => "Person Lastname",
+        },
+        :uid => "100"
+      }
+
+      authenticator = Auth::GithubAuthenticator.new
+      SiteSetting.email_domains_whitelist = "whitelist.com"
+      result = authenticator.after_authenticate(hash)
+
+      expect(result.user).to eq(nil)
+      expect(result.username).to eq(hash[:info][:nickname])
+      expect(result.name).to eq(hash[:info][:name])
+      expect(result.email).to eq("allowed@whitelist.com")
+      expect(result.email_valid).to eq(true)
+    end
+
+  end
+end