glitchier-soc/app/controllers/concerns/signature_verification.rb
Claire 1145dbd327
Improve error reporting and logging when processing remote accounts (#15605)
* Add a more descriptive PrivateNetworkAddressError exception class

* Remove unnecessary exception class to rescue clause

* Remove unnecessary include to JsonLdHelper

* Give more neutral error message when too many webfinger redirects

* Remove unnecessary guard condition

* Rework how “ActivityPub::FetchRemoteAccountService” handles errors

Add “suppress_errors” keyword argument to avoid raising errors in
ActivityPub::FetchRemoteAccountService#call (default/previous behavior).

* Rework how “ActivityPub::FetchRemoteKeyService” handles errors

Add “suppress_errors” keyword argument to avoid raising errors in
ActivityPub::FetchRemoteKeyService#call (default/previous behavior).

* Fix Webfinger::RedirectError not being a subclass of Webfinger::Error

* Add suppress_errors option to ResolveAccountService

Defaults to true (to preserve previous behavior). If set to false,
errors will be raised instead of caught, allowing the caller to be
informed of what went wrong.

* Return more precise error when failing to fetch account signing AP payloads

* Add tests

* Fixes

* Refactor error handling a bit

* Fix various issues

* Add specific error when provided Digest is not 256 bits of base64-encoded data

* Please CodeClimate

* Improve webfinger error reporting
2022-09-20 23:30:26 +02:00

266 lines
11 KiB
Ruby

# 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
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
def signed_request?
request.headers['Signature'].present?
end
def signature_verification_failure_reason
@signature_verification_failure_reason
end
def signature_verification_failure_code
@signature_verification_failure_code || 401
end
def signature_key_id
signature_params['keyId']
rescue SignatureVerificationError
nil
end
def signed_request_account
return @signed_request_account if defined?(@signed_request_account)
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?
verify_signature_strength!
verify_body_digest!
account = account_from_key_id(signature_params['keyId'])
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
return account unless verify_signature(account, signature, compare_signed_string).nil?
account = stoplight_wrap_request { account.possibly_stale? ? account.refresh! : account_refresh_key(account) }
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?
fail_with! "Verification failed for #{account.username}@#{account.domain} #{account.uri} using rsa-sha256 (RSASSA-PKCS1-v1_5 with SHA-256)"
rescue SignatureVerificationError => e
fail_with! e.message
rescue HTTP::Error, OpenSSL::SSL::SSLError => e
fail_with! "Failed to fetch remote data: #{e.message}"
rescue Mastodon::UnexptectedResponseError
fail_with! 'Failed to fetch remote data (got unexpected reply from server)'
rescue Stoplight::Error::RedLight
fail_with! 'Fetching attempt skipped because of recent connection failure'
end
def request_body
@request_body ||= request.raw_post
end
private
def fail_with!(message)
@signature_verification_failure_reason = message
@signed_request_account = nil
end
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 when doing a GET request' if request.get? && !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_body_digest!
return unless signed_headers.include?('digest')
raise SignatureVerificationError, 'Digest header missing' unless request.headers.key?('Digest')
digests = request.headers['Digest'].split(',').map { |digest| digest.split('=', 2) }.map { |key, value| [key.downcase, value] }
sha256 = digests.assoc('sha-256')
raise SignatureVerificationError, "Mastodon only supports SHA-256 in Digest header. Offered algorithms: #{digests.map(&:first).join(', ')}" if sha256.nil?
return if body_digest == sha256[1]
digest_size = begin
Base64.strict_decode64(sha256[1].strip).length
rescue ArgumentError
raise SignatureVerificationError, "Invalid Digest value. The provided Digest value is not a valid base64 string. Given digest: #{sha256[1]}"
end
raise SignatureVerificationError, "Invalid Digest value. The provided Digest value is not a SHA-256 digest. Given digest: #{sha256[1]}" if digest_size != 32
raise SignatureVerificationError, "Invalid Digest value. Computed SHA-256 digest: #{body_digest}; given: #{sha256[1]}"
end
def verify_signature(account, signature, compare_signed_string)
if account.keypair.public_key.verify(OpenSSL::Digest.new('SHA256'), signature, compare_signed_string)
@signed_request_account = account
@signed_request_account
end
rescue OpenSSL::PKey::RSAError
nil
end
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']}"
else
"#{signed_header}: #{request.headers[to_header_name(signed_header)]}"
end
end.join("\n")
end
def matches_time_window?
created_time = nil
expires_time = nil
begin
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
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
@body_digest ||= Digest::SHA256.base64digest(request_body)
end
def to_header_name(name)
name.split(/-/).map(&:capitalize).join('-')
end
def missing_required_signature_parameters?
signature_params['keyId'].blank? || signature_params['signature'].blank?
end
def account_from_key_id(key_id)
domain = key_id.start_with?('acct:') ? key_id.split('@').last : key_id
if domain_not_allowed?(domain)
@signature_verification_failure_code = 403
return
end
if key_id.start_with?('acct:')
stoplight_wrap_request { ResolveAccountService.new.call(key_id.gsub(/\Aacct:/, ''), suppress_errors: false) }
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, suppress_errors: false) }
account
end
rescue Mastodon::PrivateNetworkAddressError => e
raise SignatureVerificationError, "Requests to private network addresses are disallowed (tried to query #{e.host})"
rescue Mastodon::HostValidationError, ActivityPub::FetchRemoteAccountService::Error, ActivityPub::FetchRemoteKeyService::Error, Webfinger::Error => e
raise SignatureVerificationError, e.message
end
def stoplight_wrap_request(&block)
Stoplight("source:#{request.remote_ip}", &block)
.with_threshold(1)
.with_cool_off_time(5.minutes.seconds)
.with_error_handler { |error, handle| error.is_a?(HTTP::Error) || error.is_a?(OpenSSL::SSL::SSLError) ? 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, suppress_errors: false)
rescue Mastodon::PrivateNetworkAddressError => e
raise SignatureVerificationError, "Requests to private network addresses are disallowed (tried to query #{e.host})"
rescue Mastodon::HostValidationError, ActivityPub::FetchRemoteAccountService::Error, Webfinger::Error => e
raise SignatureVerificationError, e.message
end
end