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Rewrite signature verification using regexps and StringScanner (#29133)

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Claire 2024-02-07 18:24:42 +01:00 committed by GitHub
parent 79b4b94f3a
commit eff447a455
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2 changed files with 24 additions and 37 deletions
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55
app/lib/signature_parser.rb
View file

@ -11,43 +11,30 @@ class SignatureParser
# In addition, ignore a `Signature ` string prefix that was added by old versions
# of `node-http-signatures`
class SignatureParamsParser < Parslet::Parser
rule(:token) { match("[0-9a-zA-Z!#$%&'*+.^_`|~-]").repeat(1).as(:token) }
rule(:quoted_string) { str('"') >> (qdtext | quoted_pair).repeat.as(:quoted_string) >> str('"') }
TOKEN_RE = /[0-9a-zA-Z!#$%&'*+.^_`|~-]+/
# 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(:param)) do
(param.is_a?(Array) ? param : [param]).each_with_object({}) { |(key, value), hash| hash[key] = value }
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
QUOTED_STRING_RE = /"([^\\"]|(\\.))*"/
PARAM_RE = /(?<key>#{TOKEN_RE})\s*=\s*((?<value>#{TOKEN_RE})|(?<quoted_value>#{QUOTED_STRING_RE}))/
def self.parse(raw_signature)
tree = SignatureParamsParser.new.parse(raw_signature)
SignatureParamsTransformer.new.apply(tree)
rescue Parslet::ParseFailed
# 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

4
spec/lib/signature_parser_spec.rb
View file

@ -10,12 +10,12 @@ RSpec.describe SignatureParser do
let(:header) do
# This example signature string deliberately mixes uneven spacing
# and quoting styles to ensure everything is covered
'keyId = "https://remote.domain/users/bob#main-key",algorithm= rsa-sha256 , headers="host date digest (request-target)",signature="gmhMjgMROGElJU3fpehV2acD5kMHeELi8EFP2UPHOdQ54H0r55AxIpji+J3lPe+N2qSb/4H1KXIh6f0lRu8TGSsu12OQmg5hiO8VA9flcA/mh9Lpk+qwlQZIPRqKP9xUEfqD+Z7ti5wPzDKrWAUK/7FIqWgcT/mlqB1R1MGkpMFc/q4CIs2OSNiWgA4K+Kp21oQxzC2kUuYob04gAZ7cyE/FTia5t08uv6lVYFdRsn4XNPn1MsHgFBwBMRG79ng3SyhoG4PrqBEi5q2IdLq3zfre/M6He3wlCpyO2VJNdGVoTIzeZ0Zz8jUscPV3XtWUchpGclLGSaKaq/JyNZeiYQ=="' # rubocop:disable Layout/LineLength
'keyId = "https://remote.domain/users/bob#main-key,",algorithm= rsa-sha256 , headers="host date digest (request-target)",signature="gmhMjgMROGElJU3fpehV2acD5kMHeELi8EFP2UPHOdQ54H0r55AxIpji+J3lPe+N2qSb/4H1KXIh6f0lRu8TGSsu12OQmg5hiO8VA9flcA/mh9Lpk+qwlQZIPRqKP9xUEfqD+Z7ti5wPzDKrWAUK/7FIqWgcT/mlqB1R1MGkpMFc/q4CIs2OSNiWgA4K+Kp21oQxzC2kUuYob04gAZ7cyE/FTia5t08uv6lVYFdRsn4XNPn1MsHgFBwBMRG79ng3SyhoG4PrqBEi5q2IdLq3zfre/M6He3wlCpyO2VJNdGVoTIzeZ0Zz8jUscPV3XtWUchpGclLGSaKaq/JyNZeiYQ=="' # rubocop:disable Layout/LineLength
end
it 'correctly parses the header' do
expect(subject).to eq({
'keyId' => 'https://remote.domain/users/bob#main-key',
'keyId' => 'https://remote.domain/users/bob#main-key,',
'algorithm' => 'rsa-sha256',
'headers' => 'host date digest (request-target)',
'signature' => 'gmhMjgMROGElJU3fpehV2acD5kMHeELi8EFP2UPHOdQ54H0r55AxIpji+J3lPe+N2qSb/4H1KXIh6f0lRu8TGSsu12OQmg5hiO8VA9flcA/mh9Lpk+qwlQZIPRqKP9xUEfqD+Z7ti5wPzDKrWAUK/7FIqWgcT/mlqB1R1MGkpMFc/q4CIs2OSNiWgA4K+Kp21oQxzC2kUuYob04gAZ7cyE/FTia5t08uv6lVYFdRsn4XNPn1MsHgFBwBMRG79ng3SyhoG4PrqBEi5q2IdLq3zfre/M6He3wlCpyO2VJNdGVoTIzeZ0Zz8jUscPV3XtWUchpGclLGSaKaq/JyNZeiYQ==', # rubocop:disable Layout/LineLength