jose/lib/jws/serializers.js

const isObject = require('../help/is_object')
let validateCrit = require('../help/validate_crit')
const { JWSInvalid } = require('../errors')

validateCrit = validateCrit.bind(undefined, JWSInvalid)

const compactSerializer = (payload, [recipient]) => {
  return `${recipient.protected}.${payload}.${recipient.signature}`
}
compactSerializer.validate = (jws, { 0: { unprotectedHeader, protectedHeader }, length }) => {
  if (length !== 1 || unprotectedHeader) {
    throw new JWSInvalid('JWS Compact Serialization doesn\'t support multiple recipients or JWS unprotected headers')
  }
  validateCrit(protectedHeader, unprotectedHeader, protectedHeader ? protectedHeader.crit : undefined)
}

const flattenedSerializer = (payload, [recipient]) => {
  const { header, signature, protected: prot } = recipient

  return {
    payload,
    ...prot ? { protected: prot } : undefined,
    ...header ? { header } : undefined,
    signature
  }
}
flattenedSerializer.validate = (jws, { 0: { unprotectedHeader, protectedHeader }, length }) => {
  if (length !== 1) {
    throw new JWSInvalid('Flattened JWS JSON Serialization doesn\'t support multiple recipients')
  }
  validateCrit(protectedHeader, unprotectedHeader, protectedHeader ? protectedHeader.crit : undefined)
}

const generalSerializer = (payload, recipients) => {
  return {
    payload,
    signatures: recipients.map(({ header, signature, protected: prot }) => {
      return {
        ...prot ? { protected: prot } : undefined,
        ...header ? { header } : undefined,
        signature
      }
    })
  }
}
generalSerializer.validate = (jws, recipients) => {
  let validateB64 = false
  recipients.forEach(({ protectedHeader, unprotectedHeader }) => {
    if (protectedHeader && !validateB64 && 'b64' in protectedHeader) {
      validateB64 = true
    }
    validateCrit(protectedHeader, unprotectedHeader, protectedHeader ? protectedHeader.crit : undefined)
  })

  if (validateB64) {
    const values = recipients.map(({ protectedHeader }) => protectedHeader && protectedHeader.b64)
    if (!values.every((actual, i, [expected]) => actual === expected)) {
      throw new JWSInvalid('the "b64" Header Parameter value MUST be the same for all recipients')
    }
  }
}

const isJSON = (input) => {
  return isObject(input) && (typeof input.payload === 'string' || Buffer.isBuffer(input.payload))
}

const isValidRecipient = (recipient) => {
  return isObject(recipient) && typeof recipient.signature === 'string' &&
    (recipient.header === undefined || isObject(recipient.header)) &&
    (recipient.protected === undefined || typeof recipient.protected === 'string')
}

const isMultiRecipient = (input) => {
  if (Array.isArray(input.signatures) && input.signatures.every(isValidRecipient)) {
    return true
  }

  return false
}

const detect = (input) => {
  if (typeof input === 'string' && input.split('.').length === 3) {
    return 'compact'
  }

  if (isJSON(input)) {
    if (isMultiRecipient(input)) {
      return 'general'
    }

    if (isValidRecipient(input)) {
      return 'flattened'
    }
  }

  throw new JWSInvalid('JWS malformed or invalid serialization')
}

module.exports = {
  compact: compactSerializer,
  flattened: flattenedSerializer,
  general: generalSerializer,
  detect
}