Module: Foil::Server::GateDelivery

Defined in:
lib/foil/server/gate_delivery.rb

Constant Summary collapse

GATE_DELIVERY_VERSION = 
1
GATE_DELIVERY_ALGORITHM = 
"x25519-hkdf-sha256/aes-256-gcm"
GATE_AGENT_TOKEN_ENV_SUFFIX = 
"_GATE_AGENT_TOKEN"
BLOCKED_GATE_ENV_VAR_KEYS = 
%w[
  BASH_ENV
  BROWSER
  CDPATH
  DYLD_INSERT_LIBRARIES
  DYLD_LIBRARY_PATH
  EDITOR
  ENV
  GIT_ASKPASS
  GIT_SSH_COMMAND
  HOME
  LD_LIBRARY_PATH
  LD_PRELOAD
  NODE_OPTIONS
  NODE_PATH
  PATH
  PERL5OPT
  PERLLIB
  PROMPT_COMMAND
  PYTHONHOME
  PYTHONPATH
  PYTHONSTARTUP
  RUBYLIB
  RUBYOPT
  SHELLOPTS
  SSH_ASKPASS
  VISUAL
  XDG_CONFIG_HOME
].freeze
BLOCKED_GATE_ENV_VAR_PREFIXES = 
%w[NPM_CONFIG_ BUN_CONFIG_ GIT_CONFIG_].freeze
WEBHOOK_EVENT_TYPES = 
%w[
  session.fingerprint.calculated
  session.result.persisted
  gate.session.approved
  webhook.test
].freeze
GATE_DELIVERY_HKDF_INFO = 
"foil-gate-delivery:v1".b.freeze
X25519_SPKI_PREFIX = 
["302a300506032b656e032100"].pack("H*").freeze

Class Method Summary collapse

Class Method Details

.create_delivery_key_pair ⇒ Object 



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# File 'lib/foil/server/gate_delivery.rb', line 85

def create_delivery_key_pair
  CryptoSupport.ensure_supported_runtime!
  private_key = OpenSSL::PKey.generate_key("X25519")
  raw_public_key = raw_x25519_public_key_from_key_object(private_key.public_key)
  {
    delivery: {
      version: GATE_DELIVERY_VERSION,
      algorithm: GATE_DELIVERY_ALGORITHM,
      key_id: key_id_for_raw_x25519_public_key(raw_public_key),
      public_key: Base64.urlsafe_encode64(raw_public_key, padding: false)
    },
    private_key: private_key
  }
end

.create_encrypted_delivery_response(input) ⇒ Object 



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# File 'lib/foil/server/gate_delivery.rb', line 129

def create_encrypted_delivery_response(input)
  {
    encrypted_delivery: encrypt_gate_delivery_payload(
      input.fetch(:delivery),
      {
        version: GATE_DELIVERY_VERSION,
        outputs: input.fetch(:outputs)
      }
    )
  }
end

.create_gate_approved_webhook_response(input) ⇒ Object 



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# File 'lib/foil/server/gate_delivery.rb', line 141

def create_gate_approved_webhook_response(input)
  create_encrypted_delivery_response(input)
end

.decrypt_gate_delivery_envelope(private_key, envelope) ⇒ Object 



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# File 'lib/foil/server/gate_delivery.rb', line 192

def decrypt_gate_delivery_envelope(private_key, envelope)
  CryptoSupport.ensure_supported_runtime!
  validated = validate_encrypted_gate_delivery_envelope(envelope)
  shared_secret = private_key.derive(
    OpenSSL::PKey.read(X25519_SPKI_PREFIX + b64url_decode(validated[:ephemeral_public_key], "encrypted_delivery.ephemeral_public_key"))
  )
  key = OpenSSL::KDF.hkdf(
    shared_secret,
    salt: b64url_decode(validated[:salt], "encrypted_delivery.salt"),
    info: GATE_DELIVERY_HKDF_INFO,
    length: 32,
    hash: "SHA256"
  )
  cipher = OpenSSL::Cipher.new("aes-256-gcm")
  cipher.decrypt
  cipher.key = key
  cipher.iv = b64url_decode(validated[:iv], "encrypted_delivery.iv")
  cipher.auth_tag = b64url_decode(validated[:tag], "encrypted_delivery.tag")
  cipher.auth_data = ""
  plaintext = cipher.update(b64url_decode(validated[:ciphertext], "encrypted_delivery.ciphertext")) + cipher.final
  payload = JSON.parse(plaintext)
  raise ArgumentError, "encrypted_delivery payload must be an object" unless payload.is_a?(Hash)

  symbolize(payload).tap do |candidate|
    raise ArgumentError, "encrypted_delivery payload version must be 1" unless candidate[:version] == GATE_DELIVERY_VERSION
    raise ArgumentError, "encrypted_delivery payload outputs must be an object" unless candidate[:outputs].is_a?(Hash)
    candidate[:outputs].each do |key_name, item|
      raise ArgumentError, "encrypted_delivery output #{key_name} must be a string" unless item.is_a?(String)
    end
  end
rescue JSON::ParserError
  raise ArgumentError, "encrypted_delivery decrypted to invalid JSON"
end

.derive_gate_agent_token_env_key(service_id) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/foil/server/gate_delivery.rb', line 53

def derive_gate_agent_token_env_key(service_id)
  normalized = service_id.to_s.strip.gsub(/[^A-Za-z0-9]+/, "_").gsub(/^_+|_+$/, "").gsub(/_+/, "_").upcase
  raise ArgumentError, "service_id is required to derive a Gate agent token env key" if normalized.empty?

  return "FOIL#{GATE_AGENT_TOKEN_ENV_SUFFIX}" if ["FOIL", "FOIL"].include?(normalized)

  "#{normalized}#{GATE_AGENT_TOKEN_ENV_SUFFIX}"
end

.encrypt_gate_delivery_payload(delivery, payload) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/foil/server/gate_delivery.rb', line 160

def encrypt_gate_delivery_payload(delivery, payload)
  CryptoSupport.ensure_supported_runtime!
  validated_delivery = validate_gate_delivery_request(delivery)
  payload = symbolize(payload)
  raise ArgumentError, "Gate delivery payload version must be 1" unless payload[:version] == GATE_DELIVERY_VERSION

  recipient_public_key = OpenSSL::PKey.read(X25519_SPKI_PREFIX + b64url_decode(validated_delivery[:public_key], "delivery.public_key"))
  ephemeral_private_key = OpenSSL::PKey.generate_key("X25519")
  shared_secret = ephemeral_private_key.derive(recipient_public_key)
  salt = OpenSSL::Random.random_bytes(32)
  iv = OpenSSL::Random.random_bytes(12)
  key = OpenSSL::KDF.hkdf(shared_secret, salt: salt, info: GATE_DELIVERY_HKDF_INFO, length: 32, hash: "SHA256")

  cipher = OpenSSL::Cipher.new("aes-256-gcm")
  cipher.encrypt
  cipher.key = key
  cipher.iv = iv
  ciphertext = cipher.update(JSON.generate(compact_payload(payload))) + cipher.final
  tag = cipher.auth_tag

  {
    version: GATE_DELIVERY_VERSION,
    algorithm: GATE_DELIVERY_ALGORITHM,
    key_id: validated_delivery[:key_id],
    ephemeral_public_key: Base64.urlsafe_encode64(raw_x25519_public_key_from_key_object(ephemeral_private_key.public_key), padding: false),
    salt: Base64.urlsafe_encode64(salt, padding: false),
    iv: Base64.urlsafe_encode64(iv, padding: false),
    ciphertext: Base64.urlsafe_encode64(ciphertext, padding: false),
    tag: Base64.urlsafe_encode64(tag, padding: false)
  }
end

.export_delivery_private_key_pkcs8(private_key) ⇒ Object 



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# File 'lib/foil/server/gate_delivery.rb', line 100

def export_delivery_private_key_pkcs8(private_key)
  CryptoSupport.ensure_supported_runtime!
  Base64.urlsafe_encode64(private_key.private_to_der, padding: false)
end

.import_delivery_private_key_pkcs8(value) ⇒ Object 



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# File 'lib/foil/server/gate_delivery.rb', line 105

def import_delivery_private_key_pkcs8(value)
  CryptoSupport.ensure_supported_runtime!
  OpenSSL::PKey.read(b64url_decode(value, "delivery.private_key_pkcs8"))
end

.is_blocked_gate_env_var_key(key) ⇒ Object 



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# File 'lib/foil/server/gate_delivery.rb', line 66

def is_blocked_gate_env_var_key(key)
  normalized = key.to_s.strip.upcase
  BLOCKED_GATE_ENV_VAR_KEYS.include?(normalized) || BLOCKED_GATE_ENV_VAR_PREFIXES.any? { |prefix| normalized.start_with?(prefix) }
end

.is_gate_managed_env_var_key(key) ⇒ Object 



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# File 'lib/foil/server/gate_delivery.rb', line 62

def is_gate_managed_env_var_key(key)
  key == "FOIL_AGENT_TOKEN" || key.to_s.end_with?(GATE_AGENT_TOKEN_ENV_SUFFIX)
end

.key_id_for_raw_x25519_public_key(raw_public_key) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/foil/server/gate_delivery.rb', line 79

def key_id_for_raw_x25519_public_key(raw_public_key)
  raise ArgumentError, "X25519 public key must be 32 bytes" unless raw_public_key.bytesize == 32

  Base64.urlsafe_encode64(Digest::SHA256.digest(raw_public_key), padding: false)
end

.parse_webhook_event(raw_body) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/foil/server/gate_delivery.rb', line 265

def parse_webhook_event(raw_body)
  envelope = symbolize(JSON.parse(raw_body))
  raise ArgumentError, "webhook event object must be webhook_event" unless envelope[:object] == "webhook_event"
  raise ArgumentError, "webhook event id is required" if envelope[:id].to_s.empty?
  raise ArgumentError, "webhook event type is required" if envelope[:type].to_s.empty?
  raise ArgumentError, "unsupported webhook event type: #{envelope[:type]}" unless WEBHOOK_EVENT_TYPES.include?(envelope[:type])
  raise ArgumentError, "webhook event created timestamp is required" if envelope[:created].to_s.empty?
  raise ArgumentError, "webhook event data must be an object" unless envelope[:data].is_a?(Hash)

  envelope[:data] = validate_gate_approved_webhook_payload(envelope[:data]) if envelope[:type] == "gate.session.approved"
  envelope
end

.raw_x25519_public_key_from_key_object(public_key) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/foil/server/gate_delivery.rb', line 71

def raw_x25519_public_key_from_key_object(public_key)
  der = public_key.public_to_der
  raise ArgumentError, "Unexpected X25519 public key encoding" unless der.bytesize == X25519_SPKI_PREFIX.bytesize + 32
  raise ArgumentError, "Unexpected X25519 public key prefix" unless der.byteslice(0, X25519_SPKI_PREFIX.bytesize) == X25519_SPKI_PREFIX

  der.byteslice(X25519_SPKI_PREFIX.bytesize, 32)
end

.validate_encrypted_gate_delivery_envelope(value) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/foil/server/gate_delivery.rb', line 145

def validate_encrypted_gate_delivery_envelope(value)
  candidate = symbolize(value)
  raise ArgumentError, "encrypted_delivery.version must be 1" unless candidate[:version] == GATE_DELIVERY_VERSION
  raise ArgumentError, "encrypted_delivery.algorithm must be #{GATE_DELIVERY_ALGORITHM}" unless candidate[:algorithm] == GATE_DELIVERY_ALGORITHM
  %i[key_id ephemeral_public_key salt iv ciphertext tag].each do |field|
    raise ArgumentError, "encrypted_delivery.#{field} is required" if candidate[field].to_s.empty?
  end
  raise ArgumentError, "encrypted_delivery.ephemeral_public_key must be 32 bytes" unless b64url_decode(candidate[:ephemeral_public_key], "encrypted_delivery.ephemeral_public_key").bytesize == 32
  raise ArgumentError, "encrypted_delivery.salt must be 32 bytes" unless b64url_decode(candidate[:salt], "encrypted_delivery.salt").bytesize == 32
  raise ArgumentError, "encrypted_delivery.iv must be 12 bytes" unless b64url_decode(candidate[:iv], "encrypted_delivery.iv").bytesize == 12
  raise ArgumentError, "encrypted_delivery.tag must be 16 bytes" unless b64url_decode(candidate[:tag], "encrypted_delivery.tag").bytesize == 16

  candidate
end

.validate_gate_approved_webhook_payload(value) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/foil/server/gate_delivery.rb', line 226

def validate_gate_approved_webhook_payload(value)
  candidate = symbolize(value)
  raise ArgumentError, "webhook payload must not include event; use the webhook event envelope type" if candidate.key?(:event)
  raise ArgumentError, "service_id is required" if candidate[:service_id].to_s.empty?
  raise ArgumentError, "gate_session_id is required" if candidate[:gate_session_id].to_s.empty?
  raise ArgumentError, "gate_account_id is required" if candidate[:gate_account_id].to_s.empty?
  raise ArgumentError, "account_name is required" if candidate[:account_name].to_s.empty?
  raise ArgumentError, "metadata must be an object or null" unless candidate[:metadata].nil? || candidate[:metadata].is_a?(Hash)
  raise ArgumentError, "foil must be an object" unless candidate[:foil].is_a?(Hash)
  verdict = candidate[:foil][:verdict]
  raise ArgumentError, "foil.verdict is invalid" unless %w[bot human inconclusive].include?(verdict)
  score = candidate[:foil][:score]
  raise ArgumentError, "foil.score must be a number or null" unless score.nil? || score.is_a?(Numeric)

  {
    service_id: candidate[:service_id],
    gate_session_id: candidate[:gate_session_id],
    gate_account_id: candidate[:gate_account_id],
    account_name: candidate[:account_name],
    metadata: candidate[:metadata]&.dup,
    foil: {
      verdict: verdict,
      score: score
    },
    delivery: validate_gate_delivery_request(candidate[:delivery])
  }
end

.validate_gate_delivery_request(value) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/foil/server/gate_delivery.rb', line 110

def validate_gate_delivery_request(value)
  candidate = symbolize(value)
  raise ArgumentError, "delivery.version must be 1" unless candidate[:version] == GATE_DELIVERY_VERSION
  raise ArgumentError, "delivery.algorithm must be #{GATE_DELIVERY_ALGORITHM}" unless candidate[:algorithm] == GATE_DELIVERY_ALGORITHM
  raise ArgumentError, "delivery.public_key is required" if candidate[:public_key].to_s.empty?
  raise ArgumentError, "delivery.key_id is required" if candidate[:key_id].to_s.empty?

  raw_public_key = b64url_decode(candidate[:public_key], "delivery.public_key")
  raise ArgumentError, "delivery.public_key must be a raw X25519 public key" unless raw_public_key.bytesize == 32
  raise ArgumentError, "delivery.key_id does not match delivery.public_key" unless key_id_for_raw_x25519_public_key(raw_public_key) == candidate[:key_id]

  {
    version: GATE_DELIVERY_VERSION,
    algorithm: GATE_DELIVERY_ALGORITHM,
    key_id: candidate[:key_id],
    public_key: candidate[:public_key]
  }
end

.verify_and_parse_webhook_event(secret:, timestamp:, raw_body:, signature:, max_age_seconds: 300, now_seconds: nil) ⇒ Object 



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# File 'lib/foil/server/gate_delivery.rb', line 278

def verify_and_parse_webhook_event(secret:, timestamp:, raw_body:, signature:, max_age_seconds: 300, now_seconds: nil)
  unless verify_gate_webhook_signature(secret: secret, timestamp: timestamp, raw_body: raw_body, signature: signature, max_age_seconds: max_age_seconds, now_seconds: now_seconds)
    raise ArgumentError, "Invalid Foil webhook signature"
  end
  parse_webhook_event(raw_body)
end

.verify_gate_webhook_signature(secret:, timestamp:, raw_body:, signature:, max_age_seconds: 300, now_seconds: nil) ⇒ Object 



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# File 'lib/foil/server/gate_delivery.rb', line 254

def verify_gate_webhook_signature(secret:, timestamp:, raw_body:, signature:, max_age_seconds: 300, now_seconds: nil)
  parsed_timestamp = Integer(timestamp)
  current = now_seconds || Time.now.to_i
  return false if (current - parsed_timestamp).abs > max_age_seconds

  expected = OpenSSL::HMAC.hexdigest("SHA256", secret, "#{timestamp}.#{raw_body}")
  secure_compare(expected, signature)
rescue ArgumentError
  false
end