Add Keybase integration (#10297)

* create account_identity_proofs table

* add endpoint for keybase to check local proofs

* add async task to update validity and liveness of proofs from keybase

* first pass keybase proof CRUD

* second pass keybase proof creation

* clean up proof list and add badges

* add avatar url to keybase api

* Always highlight the “Identity Proofs” navigation item when interacting with proofs.

* Update translations.

* Add profile URL.

* Reorder proofs.

* Add proofs to bio.

* Update settings/identity_proofs front-end.

* Use `link_to`.

* Only encode query params if they exist.

URLs without params had a trailing `?`.

* Only show live proofs.

* change valid to active in proof list and update liveness before displaying

* minor fixes

* add keybase config at well-known path

* extremely naive feature flagging off the identity proof UI

* fixes for rubocop

* make identity proofs page resilient to potential keybase issues

* normalize i18n

* tweaks for brakeman

* remove two unused translations

* cleanup and add more localizations

* make keybase_contacts an admin setting

* fix ExternalProofService my_domain

* use Addressable::URI in identity proofs

* use active model serializer for keybase proof config

* more cleanup of keybase proof config

* rename proof is_valid and is_live to proof_valid and proof_live

* cleanup

* assorted tweaks for more robust communication with keybase

* Clean up

* Small fixes

* Display verified identity identically to verified links

* Clean up unused CSS

* Add caching for Keybase avatar URLs

* Remove keybase_contacts setting

29 files changed, 946 insertions, 2 deletions

diff --git a/app/controllers/api/proofs_controller.rb b/app/controllers/api/proofs_controller.rb
new file mode 100644
index 000000000..a84ad2014
--- /dev/null
+++ b/app/controllers/api/proofs_controller.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+class Api::ProofsController < Api::BaseController
+  before_action :set_account
+  before_action :set_provider
+  before_action :check_account_approval
+  before_action :check_account_suspension
+
+  def index
+    render json: @account, serializer: @provider.serializer_class
+  end
+
+  private
+
+  def set_provider
+    @provider = ProofProvider.find(params[:provider]) || raise(ActiveRecord::RecordNotFound)
+  end
+
+  def set_account
+    @account = Account.find_local!(params[:username])
+  end
+
+  def check_account_approval
+    not_found if @account.user_pending?
+  end
+
+  def check_account_suspension
+    gone if @account.suspended?
+  end
+end
diff --git a/app/controllers/settings/identity_proofs_controller.rb b/app/controllers/settings/identity_proofs_controller.rb
new file mode 100644
index 000000000..4a3b89a5e
--- /dev/null
+++ b/app/controllers/settings/identity_proofs_controller.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+class Settings::IdentityProofsController < Settings::BaseController
+  layout 'admin'
+
+  before_action :authenticate_user!
+  before_action :check_required_params, only: :new
+
+  def index
+    @proofs = AccountIdentityProof.where(account: current_account).order(provider: :asc, provider_username: :asc)
+    @proofs.each(&:refresh!)
+  end
+
+  def new
+    @proof = current_account.identity_proofs.new(
+      token: params[:token],
+      provider: params[:provider],
+      provider_username: params[:provider_username]
+    )
+
+    render layout: 'auth'
+  end
+
+  def create
+    @proof = current_account.identity_proofs.where(provider: resource_params[:provider], provider_username: resource_params[:provider_username]).first_or_initialize(resource_params)
+    @proof.token = resource_params[:token]
+
+    if @proof.save
+      redirect_to @proof.on_success_path(params[:user_agent])
+    else
+      flash[:alert] = I18n.t('identity_proofs.errors.failed', provider: @proof.provider.capitalize)
+      redirect_to settings_identity_proofs_path
+    end
+  end
+
+  private
+
+  def check_required_params
+    redirect_to settings_identity_proofs_path unless [:provider, :provider_username, :token].all? { |k| params[k].present? }
+  end
+
+  def resource_params
+    params.require(:account_identity_proof).permit(:provider, :provider_username, :token)
+  end
+end
diff --git a/app/controllers/well_known/keybase_proof_config_controller.rb b/app/controllers/well_known/keybase_proof_config_controller.rb
new file mode 100644
index 000000000..eb41e586f
--- /dev/null
+++ b/app/controllers/well_known/keybase_proof_config_controller.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+module WellKnown
+  class KeybaseProofConfigController < ActionController::Base
+    def show
+      render json: {}, serializer: ProofProvider::Keybase::ConfigSerializer
+    end
+  end
+end
diff --git a/app/javascript/images/logo_transparent_black.svg b/app/javascript/images/logo_transparent_black.svg
new file mode 100644
index 000000000..e44bcf5e1
--- /dev/null
+++ b/app/javascript/images/logo_transparent_black.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 216.4144 232.00976"><path d="M107.86523 0C78.203984.2425 49.672422 3.4535937 33.044922 11.089844c0 0-32.97656262 14.752031-32.97656262 65.082031 0 11.525-.224375 25.306175.140625 39.919925 1.19750002 49.22 9.02375002 97.72843 54.53124962 109.77343 20.9825 5.55375 38.99711 6.71547 53.505856 5.91797 26.31125-1.45875 41.08203-9.38867 41.08203-9.38867l-.86914-19.08984s-18.80171 5.92758-39.91796 5.20508c-20.921254-.7175-43.006879-2.25516-46.390629-27.94141-.3125-2.25625-.46875-4.66938-.46875-7.20313 0 0 20.536953 5.0204 46.564449 6.21289 15.915.73001 30.8393-.93343 45.99805-2.74218 29.07-3.47125 54.38125-21.3818 57.5625-37.74805 5.0125-25.78125 4.59961-62.916015 4.59961-62.916015 0-50.33-32.97461-65.082031-32.97461-65.082031C166.80539 3.4535938 138.255.2425 108.59375 0h-.72852zM74.296875 39.326172c12.355 0 21.710234 4.749297 27.896485 14.248047l6.01367 10.080078 6.01563-10.080078c6.185-9.49875 15.54023-14.248047 27.89648-14.248047 10.6775 0 19.28156 3.753672 25.85156 11.076172 6.36875 7.3225 9.53907 17.218828 9.53907 29.673828v60.941408h-24.14454V81.869141c0-12.46875-5.24453-18.798829-15.73828-18.798829-11.6025 0-17.41797 7.508516-17.41797 22.353516v32.375002H96.207031V85.423828c0-14.845-5.815468-22.353515-17.417969-22.353516-10.49375 0-15.740234 6.330079-15.740234 18.798829v59.148439H38.904297V80.076172c0-12.455 3.171016-22.351328 9.541015-29.673828 6.568751-7.3225 15.172813-11.076172 25.851563-11.076172z" fill="#000"/></svg>
diff --git a/app/javascript/images/proof_providers/keybase.png b/app/javascript/images/proof_providers/keybase.png
new file mode 100644
index 000000000..7e3ac657f
--- /dev/null
+++ b/app/javascript/images/proof_providers/keybase.png
Binary files differdiff --git a/app/javascript/styles/mastodon/forms.scss b/app/javascript/styles/mastodon/forms.scss
index 6051c1d00..9ef45e425 100644
--- a/app/javascript/styles/mastodon/forms.scss
+++ b/app/javascript/styles/mastodon/forms.scss
@@ -801,3 +801,58 @@ code {
     }
   }
 }
+
+.connection-prompt {
+  margin-bottom: 25px;
+
+  .fa-link {
+    background-color: darken($ui-base-color, 4%);
+    border-radius: 100%;
+    font-size: 24px;
+    padding: 10px;
+  }
+
+  &__column {
+    align-items: center;
+    display: flex;
+    flex: 1;
+    flex-direction: column;
+    flex-shrink: 1;
+
+    &-sep {
+      flex-grow: 0;
+      overflow: visible;
+      position: relative;
+      z-index: 1;
+    }
+  }
+
+  .account__avatar {
+    margin-bottom: 20px;
+  }
+
+  &__connection {
+    background-color: lighten($ui-base-color, 8%);
+    box-shadow: 0 0 15px rgba($base-shadow-color, 0.2);
+    border-radius: 4px;
+    padding: 25px 10px;
+    position: relative;
+    text-align: center;
+
+    &::after {
+      background-color: darken($ui-base-color, 4%);
+      content: '';
+      display: block;
+      height: 100%;
+      left: 50%;
+      position: absolute;
+      width: 1px;
+    }
+  }
+
+  &__row {
+    align-items: center;
+    display: flex;
+    flex-direction: row;
+  }
+}
diff --git a/app/lib/proof_provider.rb b/app/lib/proof_provider.rb
new file mode 100644
index 000000000..102c50f4f
--- /dev/null
+++ b/app/lib/proof_provider.rb
@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+module ProofProvider
+  SUPPORTED_PROVIDERS = %w(keybase).freeze
+
+  def self.find(identifier, proof = nil)
+    case identifier
+    when 'keybase'
+      ProofProvider::Keybase.new(proof)
+    end
+  end
+end
diff --git a/app/lib/proof_provider/keybase.rb b/app/lib/proof_provider/keybase.rb
new file mode 100644
index 000000000..96322a265
--- /dev/null
+++ b/app/lib/proof_provider/keybase.rb
@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+class ProofProvider::Keybase
+  BASE_URL = 'https://keybase.io'
+
+  class Error < StandardError; end
+
+  class ExpectedProofLiveError < Error; end
+
+  class UnexpectedResponseError < Error; end
+
+  def initialize(proof = nil)
+    @proof = proof
+  end
+
+  def serializer_class
+    ProofProvider::Keybase::Serializer
+  end
+
+  def worker_class
+    ProofProvider::Keybase::Worker
+  end
+
+  def validate!
+    unless @proof.token&.size == 66
+      @proof.errors.add(:base, I18n.t('identity_proofs.errors.keybase.invalid_token'))
+      return
+    end
+
+    return if @proof.provider_username.blank?
+
+    if verifier.valid?
+      @proof.verified = true
+      @proof.live     = false
+    else
+      @proof.errors.add(:base, I18n.t('identity_proofs.errors.keybase.verification_failed', kb_username: @proof.provider_username))
+    end
+  end
+
+  def refresh!
+    worker_class.new.perform(@proof)
+  rescue ProofProvider::Keybase::Error
+    nil
+  end
+
+  def on_success_path(user_agent = nil)
+    verifier.on_success_path(user_agent)
+  end
+
+  def badge
+    @badge ||= ProofProvider::Keybase::Badge.new(@proof.account.username, @proof.provider_username, @proof.token)
+  end
+
+  private
+
+  def verifier
+    @verifier ||= ProofProvider::Keybase::Verifier.new(@proof.account.username, @proof.provider_username, @proof.token)
+  end
+end
diff --git a/app/lib/proof_provider/keybase/badge.rb b/app/lib/proof_provider/keybase/badge.rb
new file mode 100644
index 000000000..3aa067ecf
--- /dev/null
+++ b/app/lib/proof_provider/keybase/badge.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+class ProofProvider::Keybase::Badge
+  include RoutingHelper
+
+  def initialize(local_username, provider_username, token)
+    @local_username    = local_username
+    @provider_username = provider_username
+    @token             = token
+  end
+
+  def proof_url
+    "#{ProofProvider::Keybase::BASE_URL}/#{@provider_username}/sigchain\##{@token}"
+  end
+
+  def profile_url
+    "#{ProofProvider::Keybase::BASE_URL}/#{@provider_username}"
+  end
+
+  def icon_url
+    "#{ProofProvider::Keybase::BASE_URL}/#{@provider_username}/proof_badge/#{@token}?username=#{@local_username}&domain=#{domain}"
+  end
+
+  def avatar_url
+    Rails.cache.fetch("proof_providers/keybase/#{@provider_username}/avatar_url", expires_in: 5.minutes) { remote_avatar_url } || default_avatar_url
+  end
+
+  private
+
+  def remote_avatar_url
+    request = Request.new(:get, "#{ProofProvider::Keybase::BASE_URL}/_/api/1.0/user/pic_url.json", params: { username: @provider_username })
+
+    request.perform do |res|
+      json = Oj.load(res.body_with_limit, mode: :strict)
+      json['pic_url'] if json.is_a?(Hash)
+    end
+  rescue Oj::ParseError, HTTP::Error, OpenSSL::SSL::SSLError
+    nil
+  end
+
+  def default_avatar_url
+    asset_pack_path('media/images/proof_providers/keybase.png')
+  end
+
+  def domain
+    Rails.configuration.x.local_domain
+  end
+end
diff --git a/app/lib/proof_provider/keybase/config_serializer.rb b/app/lib/proof_provider/keybase/config_serializer.rb
new file mode 100644
index 000000000..474ea74e2
--- /dev/null
+++ b/app/lib/proof_provider/keybase/config_serializer.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+class ProofProvider::Keybase::ConfigSerializer < ActiveModel::Serializer
+  include RoutingHelper
+
+  attributes :version, :domain, :display_name, :username,
+             :brand_color, :logo, :description, :prefill_url,
+             :profile_url, :check_url, :check_path, :avatar_path,
+             :contact
+
+  def version
+    1
+  end
+
+  def domain
+    Rails.configuration.x.local_domain
+  end
+
+  def display_name
+    Setting.site_title
+  end
+
+  def logo
+    { svg_black: full_asset_url(asset_pack_path('media/images/logo_transparent_black.svg')), svg_full: full_asset_url(asset_pack_path('media/images/logo.svg')) }
+  end
+
+  def brand_color
+    '#282c37'
+  end
+
+  def description
+    Setting.site_short_description.presence || Setting.site_description.presence || I18n.t('about.about_mastodon_html')
+  end
+
+  def username
+    { min: 1, max: 30, re: Account::USERNAME_RE.inspect }
+  end
+
+  def prefill_url
+    params = {
+      provider: 'keybase',
+      token: '%{sig_hash}',
+      provider_username: '%{kb_username}',
+      username: '%{username}',
+      user_agent: '%{kb_ua}',
+    }
+
+    CGI.unescape(new_settings_identity_proof_url(params))
+  end
+
+  def profile_url
+    CGI.unescape(short_account_url('%{username}')) # rubocop:disable Style/FormatStringToken
+  end
+
+  def check_url
+    CGI.unescape(api_proofs_url(username: '%{username}', provider: 'keybase'))
+  end
+
+  def check_path
+    ['signatures']
+  end
+
+  def avatar_path
+    ['avatar']
+  end
+
+  def contact
+    [Setting.site_contact_email.presence].compact
+  end
+end
diff --git a/app/lib/proof_provider/keybase/serializer.rb b/app/lib/proof_provider/keybase/serializer.rb
new file mode 100644
index 000000000..d29283600
--- /dev/null
+++ b/app/lib/proof_provider/keybase/serializer.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class ProofProvider::Keybase::Serializer < ActiveModel::Serializer
+  include RoutingHelper
+
+  attribute :avatar
+
+  has_many :identity_proofs, key: :signatures
+
+  def avatar
+    full_asset_url(object.avatar_original_url)
+  end
+
+  class AccountIdentityProofSerializer < ActiveModel::Serializer
+    attributes :sig_hash, :kb_username
+
+    def sig_hash
+      object.token
+    end
+
+    def kb_username
+      object.provider_username
+    end
+  end
+end
diff --git a/app/lib/proof_provider/keybase/verifier.rb b/app/lib/proof_provider/keybase/verifier.rb
new file mode 100644
index 000000000..86f249dd7
--- /dev/null
+++ b/app/lib/proof_provider/keybase/verifier.rb
@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+class ProofProvider::Keybase::Verifier
+  def initialize(local_username, provider_username, token)
+    @local_username    = local_username
+    @provider_username = provider_username
+    @token             = token
+  end
+
+  def valid?
+    request = Request.new(:get, "#{ProofProvider::Keybase::BASE_URL}/_/api/1.0/sig/proof_valid.json", params: query_params)
+
+    request.perform do |res|
+      json = Oj.load(res.body_with_limit, mode: :strict)
+
+      if json.is_a?(Hash)
+        json.fetch('proof_valid', false)
+      else
+        false
+      end
+    end
+  rescue Oj::ParseError, HTTP::Error, OpenSSL::SSL::SSLError
+    false
+  end
+
+  def on_success_path(user_agent = nil)
+    url = Addressable::URI.parse("#{ProofProvider::Keybase::BASE_URL}/_/proof_creation_success")
+    url.query_values = query_params.merge(kb_ua: user_agent || 'unknown')
+    url.to_s
+  end
+
+  def status
+    request = Request.new(:get, "#{ProofProvider::Keybase::BASE_URL}/_/api/1.0/sig/proof_live.json", params: query_params)
+
+    request.perform do |res|
+      raise ProofProvider::Keybase::UnexpectedResponseError unless res.code == 200
+
+      json = Oj.load(res.body_with_limit, mode: :strict)
+
+      raise ProofProvider::Keybase::UnexpectedResponseError unless json.is_a?(Hash) && json.key?('proof_valid') && json.key?('proof_live')
+
+      json
+    end
+  rescue Oj::ParseError, HTTP::Error, OpenSSL::SSL::SSLError
+    raise ProofProvider::Keybase::UnexpectedResponseError
+  end
+
+  private
+
+  def query_params
+    {
+      domain: domain,
+      kb_username: @provider_username,
+      username: @local_username,
+      sig_hash: @token,
+    }
+  end
+
+  def domain
+    Rails.configuration.x.local_domain
+  end
+end
diff --git a/app/lib/proof_provider/keybase/worker.rb b/app/lib/proof_provider/keybase/worker.rb
new file mode 100644
index 000000000..2872f59c1
--- /dev/null
+++ b/app/lib/proof_provider/keybase/worker.rb
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+class ProofProvider::Keybase::Worker
+  include Sidekiq::Worker
+
+  sidekiq_options queue: 'pull', retry: 20, unique: :until_executed
+
+  sidekiq_retry_in do |count, exception|
+    # Retry aggressively when the proof is valid but not live in Keybase.
+    # This is likely because Keybase just hasn't noticed the proof being
+    # served from here yet.
+
+    if exception.class == ProofProvider::Keybase::ExpectedProofLiveError
+      case count
+      when 0..2 then 0.seconds
+      when 2..6 then 1.second
+      end
+    end
+  end
+
+  def perform(proof_id)
+    proof    = proof_id.is_a?(AccountIdentityProof) ? proof_id : AccountIdentityProof.find(proof_id)
+    verifier = ProofProvider::Keybase::Verifier.new(proof.account.username, proof.provider_username, proof.token)
+    status   = verifier.status
+
+    # If Keybase thinks the proof is valid, and it exists here in Mastodon,
+    # then it should be live. Keybase just has to notice that it's here
+    # and then update its state. That might take a couple seconds.
+    raise ProofProvider::Keybase::ExpectedProofLiveError if status['proof_valid'] && !status['proof_live']
+
+    proof.update!(verified: status['proof_valid'], live: status['proof_live'])
+  end
+end
diff --git a/app/models/account_identity_proof.rb b/app/models/account_identity_proof.rb
new file mode 100644
index 000000000..e7a3f97e5
--- /dev/null
+++ b/app/models/account_identity_proof.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+# == Schema Information
+#
+# Table name: account_identity_proofs
+#
+#  id                :bigint(8)        not null, primary key
+#  account_id        :bigint(8)
+#  provider          :string           default(""), not null
+#  provider_username :string           default(""), not null
+#  token             :text             default(""), not null
+#  verified          :boolean          default(FALSE), not null
+#  live              :boolean          default(FALSE), not null
+#  created_at        :datetime         not null
+#  updated_at        :datetime         not null
+#
+
+class AccountIdentityProof < ApplicationRecord
+  belongs_to :account
+
+  validates :provider, inclusion: { in: ProofProvider::SUPPORTED_PROVIDERS }
+  validates :provider_username, format: { with: /\A[a-z0-9_]+\z/i }, length: { minimum: 2, maximum: 15 }
+  validates :provider_username, uniqueness: { scope: [:account_id, :provider] }
+  validates :token, format: { with: /\A[a-f0-9]+\z/ }, length: { maximum: 66 }
+
+  validate :validate_with_provider, if: :token_changed?
+
+  scope :active, -> { where(verified: true, live: true) }
+
+  after_create_commit :queue_worker
+
+  delegate :refresh!, :on_success_path, :badge, to: :provider_instance
+
+  private
+
+  def provider_instance
+    @provider_instance ||= ProofProvider.find(provider, self)
+  end
+
+  def queue_worker
+    provider_instance.worker_class.perform_async(id)
+  end
+
+  def validate_with_provider
+    provider_instance.validate!
+  end
+end
diff --git a/app/models/concerns/account_associations.rb b/app/models/concerns/account_associations.rb
index a8ba8fef1..70855e054 100644
--- a/app/models/concerns/account_associations.rb
+++ b/app/models/concerns/account_associations.rb
@@ -7,6 +7,9 @@ module AccountAssociations
     # Local users
     has_one :user, inverse_of: :account, dependent: :destroy
 
+    # Identity proofs
+    has_many :identity_proofs, class_name: 'AccountIdentityProof', dependent: :destroy, inverse_of: :account
+
     # Timelines
     has_many :stream_entries, inverse_of: :account, dependent: :destroy
     has_many :statuses, inverse_of: :account, dependent: :destroy
diff --git a/app/views/accounts/_bio.html.haml b/app/views/accounts/_bio.html.haml
index 2ea34a048..efc26d136 100644
--- a/app/views/accounts/_bio.html.haml
+++ b/app/views/accounts/_bio.html.haml
@@ -1,7 +1,17 @@
+- proofs = account.identity_proofs.active
+- fields = account.fields
+
 .public-account-bio
-  - unless account.fields.empty?
+  - unless fields.empty? && proofs.empty?
     .account__header__fields
-      - account.fields.each do |field|
+      - proofs.each do |proof|
+        %dl
+          %dt= proof.provider.capitalize
+          %dd.verified
+            = link_to fa_icon('check'), proof.badge.proof_url, class: 'verified__mark', title: t('accounts.link_verified_on', date: l(proof.updated_at))
+            = link_to proof.provider_username, proof.badge.profile_url
+
+      - fields.each do |field|
         %dl
           %dt.emojify{ title: field.name }= Formatter.instance.format_field(account, field.name, custom_emojify: true)
           %dd{ title: field.value, class: custom_field_classes(field) }
@@ -9,6 +19,7 @@
               %span.verified__mark{ title: t('accounts.link_verified_on', date: l(field.verified_at)) }
                 = fa_icon 'check'
             = Formatter.instance.format_field(account, field.value, custom_emojify: true)
+
   = account_badge(account)
 
   - if account.note.present?
diff --git a/app/views/settings/identity_proofs/_proof.html.haml b/app/views/settings/identity_proofs/_proof.html.haml
new file mode 100644
index 000000000..524827ad7
--- /dev/null
+++ b/app/views/settings/identity_proofs/_proof.html.haml
@@ -0,0 +1,20 @@
+%tr
+  %td
+    = link_to proof.badge.profile_url, class: 'name-tag' do
+      = image_tag proof.badge.avatar_url, width: 15, height: 15, alt: '', class: 'avatar'
+      %span.username
+        = proof.provider_username
+        %span= "(#{proof.provider.capitalize})"
+
+  %td
+    - if proof.live?
+      %span.positive-hint
+        = fa_icon 'check-circle fw'
+        = t('identity_proofs.active')
+    - else
+      %span.negative-hint
+        = fa_icon 'times-circle fw'
+        = t('identity_proofs.inactive')
+
+  %td
+    = table_link_to 'external-link', t('identity_proofs.view_proof'), proof.badge.proof_url if proof.badge.proof_url
diff --git a/app/views/settings/identity_proofs/index.html.haml b/app/views/settings/identity_proofs/index.html.haml
new file mode 100644
index 000000000..d0ea03ecd
--- /dev/null
+++ b/app/views/settings/identity_proofs/index.html.haml
@@ -0,0 +1,17 @@
+- content_for :page_title do
+  = t('settings.identity_proofs')
+
+%p= t('identity_proofs.explanation_html')
+
+- unless @proofs.empty?
+  %hr.spacer/
+
+  .table-wrapper
+    %table.table
+      %thead
+        %tr
+          %th= t('identity_proofs.identity')
+          %th= t('identity_proofs.status')
+          %th
+      %tbody
+        = render partial: 'settings/identity_proofs/proof', collection: @proofs, as: :proof
diff --git a/app/views/settings/identity_proofs/new.html.haml b/app/views/settings/identity_proofs/new.html.haml
new file mode 100644
index 000000000..8ce6e61c9
--- /dev/null
+++ b/app/views/settings/identity_proofs/new.html.haml
@@ -0,0 +1,31 @@
+- content_for :page_title do
+  = t('identity_proofs.authorize_connection_prompt')
+
+.form-container
+  .oauth-prompt
+    %h2= t('identity_proofs.authorize_connection_prompt')
+
+  = simple_form_for @proof, url: settings_identity_proofs_url, html: { method: :post } do |f|
+    = f.input :provider, as: :hidden
+    = f.input :provider_username, as: :hidden
+    = f.input :token, as: :hidden
+
+    = hidden_field_tag :user_agent, params[:user_agent]
+
+    .connection-prompt
+      .connection-prompt__row.connection-prompt__connection
+        .connection-prompt__column
+          = image_tag current_account.avatar.url(:original), size: 96, class: 'account__avatar'
+
+          %p= t('identity_proofs.i_am_html', username: content_tag(:strong,current_account.username), service: site_hostname)
+
+        .connection-prompt__column.connection-prompt__column-sep
+          = fa_icon 'link'
+
+        .connection-prompt__column
+          = image_tag @proof.badge.avatar_url, size: 96, class: 'account__avatar'
+
+          %p= t('identity_proofs.i_am_html', username: content_tag(:strong, @proof.provider_username), service: @proof.provider.capitalize)
+
+    = f.button :button, t('identity_proofs.authorize'), type: :submit
+    = link_to t('simple_form.no'), settings_identity_proofs_url, class: 'button negative'
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 9f1081fb8..ba42e7ce1 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -633,6 +633,21 @@ en:
     validation_errors:
       one: Something isn't quite right yet! Please review the error below
       other: Something isn't quite right yet! Please review %{count} errors below
+  identity_proofs:
+    active: Active
+    authorize: Yes, authorize
+    authorize_connection_prompt: Authorize this cryptographic connection?
+    errors:
+      failed: The cryptographic connection failed. Please try again from %{provider}.
+      keybase:
+        invalid_token: Keybase tokens are hashes of signatures and must be 66 hex characters
+        verification_failed: Keybase does not recognize this token as a signature of Keybase user %{kb_username}. Please retry from Keybase.
+    explanation_html: Here you can cryptographically connect your other identities, such as a Keybase profile. This lets other people send you encrypted messages and trust content you send them.
+    i_am_html: I am %{username} on %{service}.
+    identity: Identity
+    inactive: Inactive
+    status: Verification status
+    view_proof: View proof
   imports:
     modes:
       merge: Merge
@@ -835,6 +850,7 @@ en:
     edit_profile: Edit profile
     export: Data export
     featured_tags: Featured hashtags
+    identity_proofs: Identity proofs
     import: Import
     migrate: Account migration
     notifications: Notifications
diff --git a/config/navigation.rb b/config/navigation.rb
index 77a300bbf..07aec4b9d 100644
--- a/config/navigation.rb
+++ b/config/navigation.rb
@@ -14,6 +14,7 @@ SimpleNavigation::Configuration.run do |navigation|
       settings.item :import, safe_join([fa_icon('cloud-upload fw'), t('settings.import')]), settings_import_url
       settings.item :export, safe_join([fa_icon('cloud-download fw'), t('settings.export')]), settings_export_url
       settings.item :authorized_apps, safe_join([fa_icon('list fw'), t('settings.authorized_apps')]), oauth_authorized_applications_url
+      settings.item :identity_proofs, safe_join([fa_icon('key fw'), t('settings.identity_proofs')]), settings_identity_proofs_path, highlights_on: %r{/settings/identity_proofs*}
     end
 
     primary.item :relationships, safe_join([fa_icon('users fw'), t('settings.relationships')]), relationships_url
diff --git a/config/routes.rb b/config/routes.rb
index dc5633a68..194b4c09b 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -22,6 +22,8 @@ Rails.application.routes.draw do
   get '.well-known/host-meta', to: 'well_known/host_meta#show', as: :host_meta, defaults: { format: 'xml' }
   get '.well-known/webfinger', to: 'well_known/webfinger#show', as: :webfinger
   get '.well-known/change-password', to: redirect('/auth/edit')
+  get '.well-known/keybase-proof-config', to: 'well_known/keybase_proof_config#show'
+
   get 'manifest', to: 'manifests#show', defaults: { format: 'json' }
   get 'intent', to: 'intents#show'
   get 'custom.css', to: 'custom_css#show', as: :custom_css
@@ -106,6 +108,8 @@ Rails.application.routes.draw do
       resource :confirmation, only: [:new, :create]
     end
 
+    resources :identity_proofs, only: [:index, :show, :new, :create, :update]
+
     resources :applications, except: [:edit] do
       member do
         post :regenerate
@@ -248,6 +252,9 @@ Rails.application.routes.draw do
     # OEmbed
     get '/oembed', to: 'oembed#show', as: :oembed
 
+    # Identity proofs
+    get :proofs, to: 'proofs#index'
+
     # JSON / REST API
     namespace :v1 do
       resources :statuses, only: [:create, :show, :destroy] do
diff --git a/db/migrate/20190316190352_create_account_identity_proofs.rb b/db/migrate/20190316190352_create_account_identity_proofs.rb
new file mode 100644
index 000000000..ddcbce3f3
--- /dev/null
+++ b/db/migrate/20190316190352_create_account_identity_proofs.rb
@@ -0,0 +1,16 @@
+class CreateAccountIdentityProofs < ActiveRecord::Migration[5.2]
+  def change
+    create_table :account_identity_proofs do |t|
+      t.belongs_to :account, foreign_key: { on_delete: :cascade }
+      t.string :provider, null: false, default: ''
+      t.string :provider_username, null: false, default: ''
+      t.text :token, null: false, default: ''
+      t.boolean :verified, null: false, default: false
+      t.boolean :live, null: false, default: false
+
+      t.timestamps null: false
+    end
+
+    add_index :account_identity_proofs, [:account_id, :provider, :provider_username], unique: true, name: :index_account_proofs_on_account_and_provider_and_username
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 790e347c3..11535d867 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -36,6 +36,19 @@ ActiveRecord::Schema.define(version: 2019_03_17_135723) do
     t.index ["account_id", "domain"], name: "index_account_domain_blocks_on_account_id_and_domain", unique: true
   end
 
+  create_table "account_identity_proofs", force: :cascade do |t|
+    t.bigint "account_id"
+    t.string "provider", default: "", null: false
+    t.string "provider_username", default: "", null: false
+    t.text "token", default: "", null: false
+    t.boolean "verified", default: false, null: false
+    t.boolean "live", default: false, null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["account_id", "provider", "provider_username"], name: "index_account_proofs_on_account_and_provider_and_username", unique: true
+    t.index ["account_id"], name: "index_account_identity_proofs_on_account_id"
+  end
+
   create_table "account_moderation_notes", force: :cascade do |t|
     t.text "content", null: false
     t.bigint "account_id", null: false
@@ -732,6 +745,7 @@ ActiveRecord::Schema.define(version: 2019_03_17_135723) do
   add_foreign_key "account_conversations", "accounts", on_delete: :cascade
   add_foreign_key "account_conversations", "conversations", on_delete: :cascade
   add_foreign_key "account_domain_blocks", "accounts", name: "fk_206c6029bd", on_delete: :cascade
+  add_foreign_key "account_identity_proofs", "accounts", on_delete: :cascade
   add_foreign_key "account_moderation_notes", "accounts"
   add_foreign_key "account_moderation_notes", "accounts", column: "target_account_id"
   add_foreign_key "account_pins", "accounts", column: "target_account_id", on_delete: :cascade
diff --git a/spec/controllers/api/proofs_controller_spec.rb b/spec/controllers/api/proofs_controller_spec.rb
new file mode 100644
index 000000000..dbde4927f
--- /dev/null
+++ b/spec/controllers/api/proofs_controller_spec.rb
@@ -0,0 +1,96 @@
+require 'rails_helper'
+
+describe Api::ProofsController do
+  let(:alice) { Fabricate(:account, username: 'alice') }
+
+  before do
+    stub_request(:get, 'https://keybase.io/_/api/1.0/sig/proof_valid.json?domain=cb6e6126.ngrok.io&kb_username=crypto_alice&sig_hash=111111111111111111111111111111111111111111111111111111111111111111&username=alice').to_return(status: 200, body: '{"proof_valid":true,"proof_live":false}')
+    stub_request(:get, 'https://keybase.io/_/api/1.0/sig/proof_live.json?domain=cb6e6126.ngrok.io&kb_username=crypto_alice&sig_hash=111111111111111111111111111111111111111111111111111111111111111111&username=alice').to_return(status: 200, body: '{"proof_valid":true,"proof_live":true}')
+    stub_request(:get, 'https://keybase.io/_/api/1.0/sig/proof_valid.json?domain=cb6e6126.ngrok.io&kb_username=hidden_alice&sig_hash=222222222222222222222222222222222222222222222222222222222222222222&username=alice').to_return(status: 200, body: '{"proof_valid":true,"proof_live":true}')
+    stub_request(:get, 'https://keybase.io/_/api/1.0/sig/proof_live.json?domain=cb6e6126.ngrok.io&kb_username=hidden_alice&sig_hash=222222222222222222222222222222222222222222222222222222222222222222&username=alice').to_return(status: 200, body: '{"proof_valid":true,"proof_live":true}')
+  end
+
+  describe 'GET #index' do
+    describe 'with a non-existent username' do
+      it '404s' do
+        get :index, params: { username: 'nonexistent', provider: 'keybase' }
+
+        expect(response).to have_http_status(:not_found)
+      end
+    end
+
+    describe 'with a user that has no proofs' do
+      it 'is an empty list of signatures' do
+        get :index, params: { username: alice.username, provider: 'keybase' }
+
+        expect(body_as_json[:signatures]).to eq []
+      end
+    end
+
+    describe 'with a user that has a live, valid proof' do
+      let(:token1) { '111111111111111111111111111111111111111111111111111111111111111111' }
+      let(:kb_name1) { 'crypto_alice' }
+
+      before do
+        Fabricate(:account_identity_proof, account: alice, verified: true, live: true, token: token1, provider_username: kb_name1)
+      end
+
+      it 'is a list with that proof in it' do
+        get :index, params: { username: alice.username, provider: 'keybase' }
+
+        expect(body_as_json[:signatures]).to eq [
+          { kb_username: kb_name1, sig_hash: token1 },
+        ]
+      end
+
+      describe 'add one that is neither live nor valid' do
+        let(:token2) { '222222222222222222222222222222222222222222222222222222222222222222' }
+        let(:kb_name2) { 'hidden_alice' }
+
+        before do
+          Fabricate(:account_identity_proof, account: alice, verified: false, live: false, token: token2, provider_username: kb_name2)
+        end
+
+        it 'is a list with both proofs' do
+          get :index, params: { username: alice.username, provider: 'keybase' }
+
+          expect(body_as_json[:signatures]).to eq [
+            { kb_username: kb_name1, sig_hash: token1 },
+            { kb_username: kb_name2, sig_hash: token2 },
+          ]
+        end
+      end
+    end
+
+    describe 'a user that has an avatar' do
+      let(:alice) { Fabricate(:account, username: 'alice', avatar: attachment_fixture('avatar.gif')) }
+
+      context 'and a proof' do
+        let(:token1) { '111111111111111111111111111111111111111111111111111111111111111111' }
+        let(:kb_name1) { 'crypto_alice' }
+
+        before do
+          Fabricate(:account_identity_proof, account: alice, verified: true, live: true, token: token1, provider_username: kb_name1)
+          get :index, params: { username: alice.username, provider: 'keybase' }
+        end
+
+        it 'has two keys: signatures and avatar' do
+          expect(body_as_json.keys).to match_array [:signatures, :avatar]
+        end
+
+        it 'has the correct signatures' do
+          expect(body_as_json[:signatures]).to eq [
+            { kb_username: kb_name1, sig_hash: token1 },
+          ]
+        end
+
+        it 'has the correct avatar url' do
+          first_part = 'https://cb6e6126.ngrok.io/system/accounts/avatars/'
+          last_part  = 'original/avatar.gif'
+
+          expect(body_as_json[:avatar]).to match /#{Regexp.quote(first_part)}(?:\d{3,5}\/){3}#{Regexp.quote(last_part)}/
+        end
+      end
+    end
+  end
+end
diff --git a/spec/controllers/settings/identity_proofs_controller_spec.rb b/spec/controllers/settings/identity_proofs_controller_spec.rb
new file mode 100644
index 000000000..46af3ccf4
--- /dev/null
+++ b/spec/controllers/settings/identity_proofs_controller_spec.rb
@@ -0,0 +1,112 @@
+require 'rails_helper'
+
+describe Settings::IdentityProofsController do
+  render_views
+
+  let(:user) { Fabricate(:user) }
+  let(:valid_token) { '1'*66 }
+  let(:kbname) { 'kbuser' }
+  let(:provider) { 'keybase' }
+  let(:findable_id) { Faker::Number.number(5) }
+  let(:unfindable_id) { Faker::Number.number(5) }
+  let(:postable_params) do
+    { account_identity_proof: { provider: provider, provider_username: kbname, token: valid_token } }
+  end
+
+  before do
+    allow_any_instance_of(ProofProvider::Keybase::Verifier).to receive(:status) { { 'proof_valid' => true, 'proof_live' => true } }
+    sign_in user, scope: :user
+  end
+
+  describe 'new proof creation' do
+    context 'GET #new with no existing proofs' do
+      it 'redirects to :index' do
+        get :new
+        expect(response).to redirect_to settings_identity_proofs_path
+      end
+    end
+
+    context 'POST #create' do
+      context 'when saving works' do
+        before do
+          allow(ProofProvider::Keybase::Worker).to receive(:perform_async)
+          allow_any_instance_of(ProofProvider::Keybase::Verifier).to receive(:valid?) { true }
+          allow_any_instance_of(AccountIdentityProof).to receive(:on_success_path) { root_url }
+        end
+
+        it 'serializes a ProofProvider::Keybase::Worker' do
+          expect(ProofProvider::Keybase::Worker).to receive(:perform_async)
+          post :create, params: postable_params
+        end
+
+        it 'delegates redirection to the proof provider' do
+          expect_any_instance_of(AccountIdentityProof).to receive(:on_success_path)
+          post :create, params: postable_params
+          expect(response).to redirect_to root_url
+        end
+      end
+
+      context 'when saving fails' do
+        before do
+          allow_any_instance_of(ProofProvider::Keybase::Verifier).to receive(:valid?) { false }
+        end
+
+        it 'redirects to :index' do
+          post :create, params: postable_params
+          expect(response).to redirect_to settings_identity_proofs_path
+        end
+
+        it 'flashes a helpful message' do
+          post :create, params: postable_params
+          expect(flash[:alert]).to eq I18n.t('identity_proofs.errors.failed', provider: 'Keybase')
+        end
+      end
+
+      context 'it can also do an update if the provider and username match an existing proof' do
+        before do
+          allow_any_instance_of(ProofProvider::Keybase::Verifier).to receive(:valid?) { true }
+          allow(ProofProvider::Keybase::Worker).to receive(:perform_async)
+          Fabricate(:account_identity_proof, account: user.account, provider: provider, provider_username: kbname)
+          allow_any_instance_of(AccountIdentityProof).to receive(:on_success_path) { root_url }
+        end
+
+        it 'calls update with the new token' do
+          expect_any_instance_of(AccountIdentityProof).to receive(:save) do |proof|
+            expect(proof.token).to eq valid_token
+          end
+
+          post :create, params: postable_params
+        end
+      end
+    end
+  end
+
+  describe 'GET #index' do
+    context 'with no existing proofs' do
+      it 'shows the helpful explanation' do
+        get :index
+        expect(response.body).to match I18n.t('identity_proofs.explanation_html')
+      end
+    end
+
+    context 'with two proofs' do
+      before do
+        allow_any_instance_of(ProofProvider::Keybase::Verifier).to receive(:valid?) { true }
+        @proof1 = Fabricate(:account_identity_proof, account: user.account)
+        @proof2 = Fabricate(:account_identity_proof, account: user.account)
+        allow_any_instance_of(AccountIdentityProof).to receive(:badge) { double(avatar_url: '', profile_url: '', proof_url: '') }
+        allow_any_instance_of(AccountIdentityProof).to receive(:refresh!) { }
+      end
+
+      it 'has the first proof username on the page' do
+        get :index
+        expect(response.body).to match /#{Regexp.quote(@proof1.provider_username)}/
+      end
+
+      it 'has the second proof username on the page' do
+        get :index
+        expect(response.body).to match /#{Regexp.quote(@proof2.provider_username)}/
+      end
+    end
+  end
+end
diff --git a/spec/controllers/well_known/keybase_proof_config_controller_spec.rb b/spec/controllers/well_known/keybase_proof_config_controller_spec.rb
new file mode 100644
index 000000000..9067e676d
--- /dev/null
+++ b/spec/controllers/well_known/keybase_proof_config_controller_spec.rb
@@ -0,0 +1,15 @@
+require 'rails_helper'
+
+describe WellKnown::KeybaseProofConfigController, type: :controller do
+  render_views
+
+  describe 'GET #show' do
+    it 'renders json' do
+      get :show
+
+      expect(response).to have_http_status(200)
+      expect(response.content_type).to eq 'application/json'
+      expect { JSON.parse(response.body) }.not_to raise_exception
+    end
+  end
+end
diff --git a/spec/fabricators/account_identity_proof_fabricator.rb b/spec/fabricators/account_identity_proof_fabricator.rb
new file mode 100644
index 000000000..94f40dfd6
--- /dev/null
+++ b/spec/fabricators/account_identity_proof_fabricator.rb
@@ -0,0 +1,8 @@
+Fabricator(:account_identity_proof) do
+  account
+  provider 'keybase'
+  provider_username { sequence(:provider_username) { |i| "#{Faker::Lorem.characters(15)}" } }
+  token { sequence(:token) { |i| "#{i}#{Faker::Crypto.sha1()*2}"[0..65] } }
+  verified false
+  live false
+end
diff --git a/spec/lib/proof_provider/keybase/verifier_spec.rb b/spec/lib/proof_provider/keybase/verifier_spec.rb
new file mode 100644
index 000000000..4ce67da9c
--- /dev/null
+++ b/spec/lib/proof_provider/keybase/verifier_spec.rb
@@ -0,0 +1,82 @@
+require 'rails_helper'
+
+describe ProofProvider::Keybase::Verifier do
+  let(:my_domain) { Rails.configuration.x.local_domain }
+
+  let(:keybase_proof) do
+    local_proof = AccountIdentityProof.new(
+      provider: 'Keybase',
+      provider_username: 'cryptoalice',
+      token: '11111111111111111111111111'
+    )
+
+    described_class.new('alice', 'cryptoalice', '11111111111111111111111111')
+  end
+
+  let(:query_params) do
+    "domain=#{my_domain}&kb_username=cryptoalice&sig_hash=11111111111111111111111111&username=alice"
+  end
+
+  describe '#valid?' do
+    let(:base_url) { 'https://keybase.io/_/api/1.0/sig/proof_valid.json' }
+
+    context 'when valid' do
+      before do
+        json_response_body = '{"status":{"code":0,"name":"OK"},"proof_valid":true}'
+        stub_request(:get, "#{base_url}?#{query_params}").to_return(status: 200, body: json_response_body)
+      end
+
+      it 'calls out to keybase and returns true' do
+        expect(keybase_proof.valid?).to eq true
+      end
+    end
+
+    context 'when invalid' do
+      before do
+        json_response_body = '{"status":{"code":0,"name":"OK"},"proof_valid":false}'
+        stub_request(:get, "#{base_url}?#{query_params}").to_return(status: 200, body: json_response_body)
+      end
+
+      it 'calls out to keybase and returns false' do
+        expect(keybase_proof.valid?).to eq false
+      end
+    end
+
+    context 'with an unexpected api response' do
+      before do
+        json_response_body = '{"status":{"code":100,"desc":"wrong size hex_id","fields":{"sig_hash":"wrong size hex_id"},"name":"INPUT_ERROR"}}'
+        stub_request(:get, "#{base_url}?#{query_params}").to_return(status: 200, body: json_response_body)
+      end
+
+      it 'swallows the error and returns false' do
+        expect(keybase_proof.valid?).to eq false
+      end
+    end
+  end
+
+  describe '#status' do
+    let(:base_url) { 'https://keybase.io/_/api/1.0/sig/proof_live.json' }
+
+    context 'with a normal response' do
+      before do
+        json_response_body = '{"status":{"code":0,"name":"OK"},"proof_live":false,"proof_valid":true}'
+        stub_request(:get, "#{base_url}?#{query_params}").to_return(status: 200, body: json_response_body)
+      end
+
+      it 'calls out to keybase and returns the status fields as proof_valid and proof_live' do
+        expect(keybase_proof.status).to include({ 'proof_valid' => true, 'proof_live' => false })
+      end
+    end
+
+    context 'with an unexpected keybase response' do
+      before do
+        json_response_body = '{"status":{"code":100,"desc":"missing non-optional field sig_hash","fields":{"sig_hash":"missing non-optional field sig_hash"},"name":"INPUT_ERROR"}}'
+        stub_request(:get, "#{base_url}?#{query_params}").to_return(status: 200, body: json_response_body)
+      end
+
+      it 'raises a ProofProvider::Keybase::UnexpectedResponseError' do
+        expect { keybase_proof.status }.to raise_error ProofProvider::Keybase::UnexpectedResponseError
+      end
+    end
+  end
+end