catstodon/app/lib/signature_parser.rb

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# frozen_string_literal: true
class SignatureParser
class ParsingError < StandardError; end
# The syntax of this header is defined in:
# https://datatracker.ietf.org/doc/html/draft-cavage-http-signatures-12#section-4
# See https://datatracker.ietf.org/doc/html/rfc7235#appendix-C
# and https://datatracker.ietf.org/doc/html/rfc7230#section-3.2.6
# In addition, ignore a `Signature ` string prefix that was added by old versions
# of `node-http-signatures`
TOKEN_RE = /[0-9a-zA-Z!#$%&'*+.^_`|~-]+/
# qdtext and quoted_pair are not exactly according to spec but meh
QUOTED_STRING_RE = /"([^\\"]|(\\.))*"/
PARAM_RE = /(?<key>#{TOKEN_RE})\s*=\s*((?<value>#{TOKEN_RE})|(?<quoted_value>#{QUOTED_STRING_RE}))/
def self.parse(raw_signature)
# Old versions of node-http-signature add an incorrect "Signature " prefix to the header
raw_signature = raw_signature.delete_prefix('Signature ')
params = {}
scanner = StringScanner.new(raw_signature)
# Use `skip` instead of `scan` as we only care about the subgroups
while scanner.skip(PARAM_RE)
# This is not actually correct with regards to quoted pairs, but it's consistent
# with our previous implementation, and good enough in practice.
params[scanner[:key]] = scanner[:value] || scanner[:quoted_value][1...-1]
scanner.skip(/\s*/)
return params if scanner.eos?
raise ParsingError unless scanner.skip(/\s*,\s*/)
end
raise ParsingError
end
end