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61f12e13aa
Any AWS account holder can subscribe their own SNS topic to a Discourse instance's /webhooks/aws and publish bounce notifications that AWS will sign legitimately. The forged bounces are processed against arbitrary user emails, bumping bounce_score and eventually triggering email revocation.. This fix adds a new `aws_sns_topic_arn_allowlist` site setting. Also hardens Jobs::ProcessSnsNotification against three issues: - Binds bounces to (message_id, to_address) via find_by, so a legitimately-subscribed SNS publisher can no longer bounce arbitrary recipients we didn't send to. - Skips duplicate notifications (next if email_log.bounced?) — AWS SNS delivers at-least-once. - Uses update! instead of update_columns so EmailLog's existing before_save normalizes the bounce status code. Also add a dashboard problem flags self-hosted admins whose SMTP looks like SES but who haven't set the allowlist yet. https://github.com/discourse/discourse/security/advisories/GHSA-8f9m-v436-wr3x
15 lines
356 B
Ruby
Vendored
15 lines
356 B
Ruby
Vendored
# frozen_string_literal: true
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module Email
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class Sns
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def self.authentic?(raw)
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require "aws-sdk-sns"
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Aws::SNS::MessageVerifier.new.authentic?(raw)
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end
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def self.allowed_topic_arn?(topic_arn)
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return false if topic_arn.blank?
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SiteSetting.aws_sns_topic_arn_allowlist.to_s.split("|").include?(topic_arn)
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end
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end
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end
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