fac529975b
* Downcase signed_headers string before building the signed string
The HTTP Signatures draft does not mandate the “headers” field to be downcased,
but mandates the header field names to be downcased in the signed string, which
means that prior to this patch, Mastodon could fail to process signatures from
some compliant clients. It also means that it would not actually check the
Digest of non-compliant clients that wouldn't use a lowercased Digest field
name.
Thankfully, I don't know of any such client.
* Revert "Remove dead code (#8919)"
This reverts commit a00ce8c92c
.
* Restore time window checking, change it to 12 hours
By checking the Date header, we can prevent replaying old vulnerable
signatures. The focus is to prevent replaying old vulnerable requests
from software that has been fixed in the meantime, so a somewhat long
window should be fine and accounts for timezone misconfiguration.
* Escape users' URLs when formatting them
Fixes possible HTML injection
* Escape all string interpolations in Formatter class
Slightly improve performance by reducing class allocations
from repeated Formatter#encode calls
* Fix code style issues
128 lines
4 KiB
Ruby
128 lines
4 KiB
Ruby
# frozen_string_literal: true
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# Implemented according to HTTP signatures (Draft 6)
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# <https://tools.ietf.org/html/draft-cavage-http-signatures-06>
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module SignatureVerification
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extend ActiveSupport::Concern
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def signed_request?
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request.headers['Signature'].present?
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end
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def signature_verification_failure_reason
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return @signature_verification_failure_reason if defined?(@signature_verification_failure_reason)
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end
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def signed_request_account
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return @signed_request_account if defined?(@signed_request_account)
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unless signed_request?
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@signature_verification_failure_reason = 'Request not signed'
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@signed_request_account = nil
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return
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end
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if request.headers['Date'].present? && !matches_time_window?
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@signature_verification_failure_reason = 'Signed request date outside acceptable time window'
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@signed_request_account = nil
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return
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end
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raw_signature = request.headers['Signature']
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signature_params = {}
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raw_signature.split(',').each do |part|
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parsed_parts = part.match(/([a-z]+)="([^"]+)"/i)
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next if parsed_parts.nil? || parsed_parts.size != 3
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signature_params[parsed_parts[1]] = parsed_parts[2]
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end
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if incompatible_signature?(signature_params)
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@signature_verification_failure_reason = 'Incompatible request signature'
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@signed_request_account = nil
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return
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end
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account = account_from_key_id(signature_params['keyId'])
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if account.nil?
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@signature_verification_failure_reason = "Public key not found for key #{signature_params['keyId']}"
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@signed_request_account = nil
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return
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end
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signature = Base64.decode64(signature_params['signature'])
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compare_signed_string = build_signed_string(signature_params['headers'])
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if account.keypair.public_key.verify(OpenSSL::Digest::SHA256.new, signature, compare_signed_string)
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@signed_request_account = account
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@signed_request_account
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elsif account.possibly_stale?
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account = account.refresh!
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if account.keypair.public_key.verify(OpenSSL::Digest::SHA256.new, signature, compare_signed_string)
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@signed_request_account = account
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@signed_request_account
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else
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@signature_verification_failure_reason = "Verification failed for #{account.username}@#{account.domain} #{account.uri}"
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@signed_request_account = nil
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end
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else
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@signature_verification_failure_reason = "Verification failed for #{account.username}@#{account.domain} #{account.uri}"
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@signed_request_account = nil
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end
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end
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def request_body
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@request_body ||= request.raw_post
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end
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private
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def build_signed_string(signed_headers)
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signed_headers = 'date' if signed_headers.blank?
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signed_headers.downcase.split(' ').map do |signed_header|
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if signed_header == Request::REQUEST_TARGET
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"#{Request::REQUEST_TARGET}: #{request.method.downcase} #{request.path}"
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elsif signed_header == 'digest'
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"digest: #{body_digest}"
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else
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"#{signed_header}: #{request.headers[to_header_name(signed_header)]}"
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end
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end.join("\n")
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end
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def matches_time_window?
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begin
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time_sent = Time.httpdate(request.headers['Date'])
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rescue ArgumentError
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return false
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end
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(Time.now.utc - time_sent).abs <= 12.hours
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end
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def body_digest
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"SHA-256=#{Digest::SHA256.base64digest(request_body)}"
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end
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def to_header_name(name)
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name.split(/-/).map(&:capitalize).join('-')
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end
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def incompatible_signature?(signature_params)
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signature_params['keyId'].blank? ||
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signature_params['signature'].blank?
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end
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def account_from_key_id(key_id)
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if key_id.start_with?('acct:')
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ResolveAccountService.new.call(key_id.gsub(/\Aacct:/, ''))
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elsif !ActivityPub::TagManager.instance.local_uri?(key_id)
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account = ActivityPub::TagManager.instance.uri_to_resource(key_id, Account)
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account ||= ActivityPub::FetchRemoteKeyService.new.call(key_id, id: false)
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account
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end
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end
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end
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