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Fix Mastodon not correctly processing HTTP Signatures with query strings (#28476)

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Claire 2024-01-03 12:29:26 +01:00 • committed by GitHub
commit 092bb8a27a
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3 changed files with 95 additions and 4 deletions
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22
app/controllers/concerns/signature_verification.rb
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@ -91,14 +91,23 @@ module SignatureVerification
raise SignatureVerificationError, "Public key not found for key #{signature_params['keyId']}" if actor.nil?
signature = Base64.decode64(signature_params['signature'])
compare_signed_string = build_signed_string
compare_signed_string = build_signed_string(include_query_string: true)
return actor unless verify_signature(actor, signature, compare_signed_string).nil?
# Compatibility quirk with older Mastodon versions
compare_signed_string = build_signed_string(include_query_string: false)
return actor unless verify_signature(actor, signature, compare_signed_string).nil?
actor = stoplight_wrap_request { actor_refresh_key!(actor) }
raise SignatureVerificationError, "Could not refresh public key #{signature_params['keyId']}" if actor.nil?
compare_signed_string = build_signed_string(include_query_string: true)
return actor unless verify_signature(actor, signature, compare_signed_string).nil?
# Compatibility quirk with older Mastodon versions
compare_signed_string = build_signed_string(include_query_string: false)
return actor unless verify_signature(actor, signature, compare_signed_string).nil?
fail_with! "Verification failed for #{actor.to_log_human_identifier} #{actor.uri} using rsa-sha256 (RSASSA-PKCS1-v1_5 with SHA-256)", signed_string: compare_signed_string, signature: signature_params['signature']
@ -180,11 +189,18 @@ module SignatureVerification
nil
end
def build_signed_string
def build_signed_string(include_query_string: true)
signed_headers.map do |signed_header|
case signed_header
when Request::REQUEST_TARGET
"#{Request::REQUEST_TARGET}: #{request.method.downcase} #{request.path}"
if include_query_string
"#{Request::REQUEST_TARGET}: #{request.method.downcase} #{request.original_fullpath}"
else
# Current versions of Mastodon incorrectly omit the query string from the (request-target) pseudo-header.
# Therefore, temporarily support such incorrect signatures for compatibility.
# TODO: remove eventually some time after release of the fixed version
"#{Request::REQUEST_TARGET}: #{request.method.downcase} #{request.path}"
end
when '(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?