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# frozen_string_literal: true
class ActivityPub::LinkedDataSignature
include JsonLdHelper
CONTEXT = 'https://w3id.org/identity/v1'
def initialize(json)
@json = json.with_indifferent_access
end
def verify_account!
return unless @json['signature'].is_a?(Hash)
type = @json['signature']['type']
creator_uri = @json['signature']['creator']
signature = @json['signature']['signatureValue']
return unless type == 'RsaSignature2017'
creator = ActivityPub::TagManager.instance.uri_to_resource(creator_uri, Account)
creator ||= ActivityPub::FetchRemoteKeyService.new.call(creator_uri, id: false)
return if creator.nil?
options_hash = hash(@json['signature'].without('type', 'id', 'signatureValue').merge('@context' => CONTEXT))
document_hash = hash(@json.without('signature'))
to_be_verified = options_hash + document_hash
if creator.keypair.public_key.verify(OpenSSL::Digest::SHA256.new, Base64.decode64(signature), to_be_verified)
creator
end
end
def sign!(creator, sign_with: nil)
options = {
'type' => 'RsaSignature2017',
'creator' => [ActivityPub::TagManager.instance.uri_for(creator), '#main-key'].join,
'created' => Time.now.utc.iso8601,
}
options_hash = hash(options.without('type', 'id', 'signatureValue').merge('@context' => CONTEXT))
document_hash = hash(@json.without('signature'))
to_be_signed = options_hash + document_hash
keypair = sign_with.present? ? OpenSSL::PKey::RSA.new(sign_with) : creator.keypair
signature = Base64.strict_encode64(keypair.sign(OpenSSL::Digest::SHA256.new, to_be_signed))
@json.merge('signature' => options.merge('signatureValue' => signature))
end
private
def hash(obj)
Digest::SHA256.hexdigest(canonicalize(obj))
end
end
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