diff options
Diffstat (limited to 'app/controllers/concerns/signature_verification.rb')
| -rw-r--r-- | app/controllers/concerns/signature_verification.rb | 163 |
1 files changed, 108 insertions, 55 deletions
diff --git a/app/controllers/concerns/signature_verification.rb b/app/controllers/concerns/signature_verification.rb index 10efbf2e0..18f549de9 100644 --- a/app/controllers/concerns/signature_verification.rb +++ b/app/controllers/concerns/signature_verification.rb @@ -7,6 +7,44 @@ module SignatureVerification include DomainControlHelper + EXPIRATION_WINDOW_LIMIT = 12.hours + CLOCK_SKEW_MARGIN = 1.hour + + class SignatureVerificationError < StandardError; end + + class SignatureParamsParser < Parslet::Parser + rule(:token) { match("[0-9a-zA-Z!#$%&'*+.^_`|~-]").repeat(1).as(:token) } + rule(:quoted_string) { str('"') >> (qdtext | quoted_pair).repeat.as(:quoted_string) >> str('"') } + # qdtext and quoted_pair are not exactly according to spec but meh + rule(:qdtext) { match('[^\\\\"]') } + rule(:quoted_pair) { str('\\') >> any } + rule(:bws) { match('\s').repeat } + rule(:param) { (token.as(:key) >> bws >> str('=') >> bws >> (token | quoted_string).as(:value)).as(:param) } + rule(:comma) { bws >> str(',') >> bws } + # Old versions of node-http-signature add an incorrect "Signature " prefix to the header + rule(:buggy_prefix) { str('Signature ') } + rule(:params) { buggy_prefix.maybe >> (param >> (comma >> param).repeat).as(:params) } + root(:params) + end + + class SignatureParamsTransformer < Parslet::Transform + rule(params: subtree(:p)) do + (p.is_a?(Array) ? p : [p]).each_with_object({}) { |(key, val), h| h[key] = val } + end + + rule(param: { key: simple(:key), value: simple(:val) }) do + [key, val] + end + + rule(quoted_string: simple(:string)) do + string.to_s + end + + rule(token: simple(:string)) do + string.to_s + end + end + def require_signature! render plain: signature_verification_failure_reason, status: signature_verification_failure_code unless signed_request_account end @@ -24,72 +62,40 @@ module SignatureVerification end def signature_key_id - 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 - signature_params['keyId'] + rescue SignatureVerificationError + nil 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 + raise SignatureVerificationError, 'Request not signed' unless signed_request? + raise SignatureVerificationError, 'Incompatible request signature. keyId and signature are required' if missing_required_signature_parameters? + raise SignatureVerificationError, 'Unsupported signature algorithm (only rsa-sha256 and hs2019 are supported)' unless %w(rsa-sha256 hs2019).include?(signature_algorithm) + raise SignatureVerificationError, 'Signed request date outside acceptable time window' unless matches_time_window? - 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 + verify_signature_strength! 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 + raise SignatureVerificationError, "Public key not found for key #{signature_params['keyId']}" if account.nil? signature = Base64.decode64(signature_params['signature']) - compare_signed_string = build_signed_string(signature_params['headers']) + compare_signed_string = build_signed_string 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 + raise SignatureVerificationError, "Public key not found for key #{signature_params['keyId']}" if account.nil? return account unless verify_signature(account, signature, compare_signed_string).nil? - @signature_verification_failure_reason = "Verification failed for #{account.username}@#{account.domain} #{account.uri}" + @signature_verification_failure_reason = "Verification failed for #{account.username}@#{account.domain} #{account.uri} using rsa-sha256 (RSASSA-PKCS1-v1_5 with SHA-256)" + @signed_request_account = nil + rescue SignatureVerificationError => e + @signature_verification_failure_reason = e.message @signed_request_account = nil end @@ -99,6 +105,31 @@ module SignatureVerification private + def signature_params + @signature_params ||= begin + raw_signature = request.headers['Signature'] + tree = SignatureParamsParser.new.parse(raw_signature) + SignatureParamsTransformer.new.apply(tree) + end + rescue Parslet::ParseFailed + raise SignatureVerificationError, 'Error parsing signature parameters' + end + + def signature_algorithm + signature_params.fetch('algorithm', 'hs2019') + end + + def signed_headers + signature_params.fetch('headers', signature_algorithm == 'hs2019' ? '(created)' : 'date').downcase.split(' ') + end + + def verify_signature_strength! + raise SignatureVerificationError, 'Mastodon requires the Date header or (created) pseudo-header to be signed' unless signed_headers.include?('date') || signed_headers.include?('(created)') + raise SignatureVerificationError, 'Mastodon requires the Digest header or (request-target) pseudo-header to be signed' unless signed_headers.include?(Request::REQUEST_TARGET) || signed_headers.include?('digest') + raise SignatureVerificationError, 'Mastodon requires the Host header to be signed' unless signed_headers.include?('host') + raise SignatureVerificationError, 'Mastodon requires the Digest header to be signed when doing a POST request' if request.post? && !signed_headers.include?('digest') + end + 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 @@ -108,12 +139,20 @@ module SignatureVerification nil end - def build_signed_string(signed_headers) - signed_headers = 'date' if signed_headers.blank? - - signed_headers.downcase.split(' ').map do |signed_header| + def build_signed_string + signed_headers.map do |signed_header| if signed_header == Request::REQUEST_TARGET "#{Request::REQUEST_TARGET}: #{request.method.downcase} #{request.path}" + elsif signed_header == '(created)' + raise SignatureVerificationError, 'Invalid pseudo-header (created) for rsa-sha256' unless signature_algorithm == 'hs2019' + raise SignatureVerificationError, 'Pseudo-header (created) used but corresponding argument missing' if signature_params['created'].blank? + + "(created): #{signature_params['created']}" + elsif signed_header == '(expires)' + raise SignatureVerificationError, 'Invalid pseudo-header (expires) for rsa-sha256' unless signature_algorithm == 'hs2019' + raise SignatureVerificationError, 'Pseudo-header (expires) used but corresponding argument missing' if signature_params['expires'].blank? + + "(expires): #{signature_params['expires']}" elsif signed_header == 'digest' "digest: #{body_digest}" else @@ -123,13 +162,28 @@ module SignatureVerification end def matches_time_window? + created_time = nil + expires_time = nil + begin - time_sent = Time.httpdate(request.headers['Date']) + if signature_algorithm == 'hs2019' && signature_params['created'].present? + created_time = Time.at(signature_params['created'].to_i).utc + elsif request.headers['Date'].present? + created_time = Time.httpdate(request.headers['Date']).utc + end + + expires_time = Time.at(signature_params['expires'].to_i).utc if signature_params['expires'].present? rescue ArgumentError return false end - (Time.now.utc - time_sent).abs <= 12.hours + expires_time ||= created_time + 5.minutes unless created_time.nil? + expires_time = [expires_time, created_time + EXPIRATION_WINDOW_LIMIT].min unless created_time.nil? + + return false if created_time.present? && created_time > Time.now.utc + CLOCK_SKEW_MARGIN + return false if expires_time.present? && Time.now.utc > expires_time + CLOCK_SKEW_MARGIN + + true end def body_digest @@ -140,9 +194,8 @@ module SignatureVerification name.split(/-/).map(&:capitalize).join('-') end - def incompatible_signature?(signature_params) - signature_params['keyId'].blank? || - signature_params['signature'].blank? + def missing_required_signature_parameters? + signature_params['keyId'].blank? || signature_params['signature'].blank? end def account_from_key_id(key_id) |