doipjs/src/signatures.js

/*
Copyright 2021 Yarmo Mackenbach

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
const openpgp = require('openpgp')
const Claim = require('./claim')
const keys = require('./keys')

/**
 * @module signatures 
 */

/**
 * Extract data from a signature and fetch the associated key
 * @async
 * @param {string} signature - The plaintext signature to process
 * @returns {Promise<object>}
 */
const process = (signature) => {
  return new Promise(async (resolve, reject) => {
    let sigData,
      result = {
        fingerprint: null,
        users: [
          {
            userData: {},
            claims: [],
          },
        ],
        primaryUserIndex: null,
        key: {
          data: null,
          fetchMethod: null,
          uri: null,
        },
      }

    try {
      sigData = await openpgp.cleartext.readArmored(signature)
    } catch (error) {
      reject(new Error('invalid_signature'))
      return
    }

    const issuerKeyId = sigData.signature.packets[0].issuerKeyId.toHex()
    const signersUserId = sigData.signature.packets[0].signersUserId
    const preferredKeyServer =
      sigData.signature.packets[0].preferredKeyServer ||
      'https://keys.openpgp.org/'
    const text = sigData.getText()
    let sigKeys = []

    text.split('\n').forEach((line, i) => {
      const match = line.match(/^([a-zA-Z0-9]*)\=(.*)$/i)
      if (!match) {
        return
      }
      switch (match[1].toLowerCase()) {
        case 'key':
          sigKeys.push(match[2])
          break

        case 'proof':
          result.users[0].claims.push(new Claim(match[2]))
          break

        default:
          break
      }
    })

    // Try overruling key
    if (sigKeys.length > 0) {
      try {
        result.key.uri = sigKeys[0]
        result.key.data = await keys.fetchURI(result.key.uri)
        result.key.fetchMethod = result.key.uri.split(':')[0]
      } catch (e) {}
    }
    // Try WKD
    if (!result.key.data && signersUserId) {
      try {
        result.key.uri = `wkd:${signersUserId}`
        result.key.data = await keys.fetchURI(result.key.uri)
        result.key.fetchMethod = 'wkd'
      } catch (e) {}
    }
    // Try HKP
    if (!result.key.data) {
      try {
        const match = preferredKeyServer.match(/^(.*\:\/\/)?([^/]*)(?:\/)?$/i)
        result.key.uri = `hkp:${match[2]}:${
          issuerKeyId ? issuerKeyId : signersUserId
        }`
        result.key.data = await keys.fetchURI(result.key.uri)
        result.key.fetchMethod = 'hkp'
      } catch (e) {
        reject(new Error('key_not_found'))
        return
      }
    }

    result.fingerprint = result.key.data.keyPacket.getFingerprint()

    result.users[0].claims.forEach((claim) => {
      claim.fingerprint = result.fingerprint
    })

    const primaryUserData = await result.key.data.getPrimaryUser()
    let userData

    if (signersUserId) {
      result.key.data.users.forEach((user) => {
        if (user.userId.email == signersUserId) {
          userData = user
        }
      })
    }
    if (!userData) {
      userData = primaryUserData.user
    }

    result.users[0].userData = {
      id: userData.userId ? userData.userId.userid : null,
      name: userData.userId ? userData.userId.name : null,
      email: userData.userId ? userData.userId.email : null,
      comment: userData.userId ? userData.userId.comment : null,
      isPrimary: primaryUserData.user.userId.userid === userData.userId.userid,
    }

    result.primaryUserIndex = result.users[0].userData.isPrimary ? 0 : null

    resolve(result)
  })
}

exports.process = process