about summary refs log tree commit diff
path: root/app/controllers/concerns/signature_verification.rb
blob: 90a57197c00bde2a1512e524887f69bba1b66640 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
# frozen_string_literal: true

# Implemented according to HTTP signatures (Draft 6)
# <https://tools.ietf.org/html/draft-cavage-http-signatures-06>
module SignatureVerification
  extend ActiveSupport::Concern

  def signed_request?
    request.headers['Signature'].present?
  end

  def signature_verification_failure_reason
    return @signature_verification_failure_reason if defined?(@signature_verification_failure_reason)
  end

  def signed_request_account
    return @signed_request_account if defined?(@signed_request_account)

    unless signed_request?
      @signature_verification_failure_reason = 'Request not signed'
      @signed_request_account = nil
      return
    end

    if request.headers['Date'].present? && !matches_time_window?
      @signature_verification_failure_reason = 'Signed request date outside acceptable time window'
      @signed_request_account = nil
      return
    end

    raw_signature    = request.headers['Signature']
    signature_params = {}

    raw_signature.split(',').each do |part|
      parsed_parts = part.match(/([a-z]+)="([^"]+)"/i)
      next if parsed_parts.nil? || parsed_parts.size != 3
      signature_params[parsed_parts[1]] = parsed_parts[2]
    end

    if incompatible_signature?(signature_params)
      @signature_verification_failure_reason = 'Incompatible request signature'
      @signed_request_account = nil
      return
    end

    account = account_from_key_id(signature_params['keyId'])

    if account.nil?
      @signature_verification_failure_reason = "Public key not found for key #{signature_params['keyId']}"
      @signed_request_account = nil
      return
    end

    signature             = Base64.decode64(signature_params['signature'])
    compare_signed_string = build_signed_string(signature_params['headers'])

    return account unless verify_signature(account, signature, compare_signed_string).nil?

    account = stoplight_wrap_request { account.possibly_stale? ? account.refresh! : account_refresh_key(account) }

    if account.nil?
      @signature_verification_failure_reason = "Public key not found for key #{signature_params['keyId']}"
      @signed_request_account = nil
      return
    end

    return account unless verify_signature(account, signature, compare_signed_string).nil?

    @signature_verification_failure_reason = "Verification failed for #{account.username}@#{account.domain} #{account.uri}"
    @signed_request_account = nil
  end

  def request_body
    @request_body ||= request.raw_post
  end

  private

  def verify_signature(account, signature, compare_signed_string)
    if account.keypair.public_key.verify(OpenSSL::Digest::SHA256.new, signature, compare_signed_string)
      @signed_request_account = account
      @signed_request_account
    end
  rescue OpenSSL::PKey::RSAError
    nil
  end

  def build_signed_string(signed_headers)
    signed_headers = 'date' if signed_headers.blank?

    signed_headers.downcase.split(' ').map do |signed_header|
      if signed_header == Request::REQUEST_TARGET
        "#{Request::REQUEST_TARGET}: #{request.method.downcase} #{request.path}"
      elsif signed_header == 'digest'
        "digest: #{body_digest}"
      else
        "#{signed_header}: #{request.headers[to_header_name(signed_header)]}"
      end
    end.join("\n")
  end

  def matches_time_window?
    begin
      time_sent = Time.httpdate(request.headers['Date'])
    rescue ArgumentError
      return false
    end

    (Time.now.utc - time_sent).abs <= 12.hours
  end

  def body_digest
    "SHA-256=#{Digest::SHA256.base64digest(request_body)}"
  end

  def to_header_name(name)
    name.split(/-/).map(&:capitalize).join('-')
  end

  def incompatible_signature?(signature_params)
    signature_params['keyId'].blank? ||
      signature_params['signature'].blank?
  end

  def account_from_key_id(key_id)
    if key_id.start_with?('acct:')
      stoplight_wrap_request { ResolveAccountService.new.call(key_id.gsub(/\Aacct:/, '')) }
    elsif !ActivityPub::TagManager.instance.local_uri?(key_id)
      account   = ActivityPub::TagManager.instance.uri_to_resource(key_id, Account)
      account ||= stoplight_wrap_request { ActivityPub::FetchRemoteKeyService.new.call(key_id, id: false) }
      account
    end
  end

  def stoplight_wrap_request(&block)
    Stoplight("source:#{request.remote_ip}", &block)
      .with_fallback { nil }
      .with_threshold(1)
      .with_cool_off_time(5.minutes.seconds)
      .with_error_handler { |error, handle| error.is_a?(HTTP::Error) ? handle.call(error) : raise(error) }
      .run
  end

  def account_refresh_key(account)
    return if account.local? || !account.activitypub?
    ActivityPub::FetchRemoteAccountService.new.call(account.uri, only_key: true)
  end
end