keyoxide-web/server/keys.js

/*
Copyright (C) 2021 Yarmo Mackenbach

This program is free software: you can redistribute it and/or modify it under
the terms of the GNU Affero General Public License as published by the Free
Software Foundation, either version 3 of the License, or (at your option)
any later version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
details.

You should have received a copy of the GNU Affero General Public License along
with this program. If not, see <https://www.gnu.org/licenses/>.

Also add information on how to contact you by electronic and paper mail.

If your software can interact with users remotely through a computer network,
you should also make sure that it provides a way for users to get its source.
For example, if your program is a web application, its interface could display
a "Source" link that leads users to an archive of the code. There are many
ways you could offer source, and different solutions will be better for different
programs; see section 13 for the specific requirements.

You should also get your employer (if you work as a programmer) or school,
if any, to sign a "copyright disclaimer" for the program, if necessary. For
more information on this, and how to apply and follow the GNU AGPL, see <https://www.gnu.org/licenses/>.
*/
import got from 'got'
import * as doipjs from 'doipjs'
import { readKey, readCleartextMessage, verify } from 'openpgp'
import { computeWKDLocalPart } from './utils.js'
import { createHash } from 'crypto'
import Keyv from 'keyv'

const c = process.env.ENABLE_EXPERIMENTAL_CACHE ? new Keyv() : null

const fetchWKD = (id) => {
    return new Promise(async (resolve, reject) => {
        let output = {
            publicKey: null,
            fetchURL: null
        }

        if (!id.includes('@')) {
            reject(new Error(`The WKD identifier "${id}" is invalid`));
        }

        const [, localPart, domain] = /([^\@]*)@(.*)/.exec(id)
        if (!localPart || !domain) {
            reject(new Error(`The WKD identifier "${id}" is invalid`));
        }
        const localEncoded = await computeWKDLocalPart(localPart)
        const urlAdvanced = `https://openpgpkey.${domain}/.well-known/openpgpkey/${domain}/hu/${localEncoded}`
        const urlDirect = `https://${domain}/.well-known/openpgpkey/hu/${localEncoded}`
        let plaintext
        
        const hash = createHash('md5').update(id).digest('hex')
        if (c && await c.get(hash)) {
            plaintext = Uint8Array.from((await c.get(hash)).split(','))
        }

        if (!plaintext) {
            try {
                plaintext = await got(urlAdvanced).then((response) => {
                    if (response.statusCode === 200) {
                        output.fetchURL = urlAdvanced
                        return new Uint8Array(response.rawBody)
                    } else {
                        return null
                    }
                })
            } catch (e) {
                try {
                    plaintext = await got(urlDirect).then((response) => {
                        if (response.statusCode === 200) {
                            output.fetchURL = urlDirect
                            return new Uint8Array(response.rawBody)
                        } else {
                            return null
                        }
                    })
                } catch (error) {
                    reject(new Error(`No public keys could be fetched using WKD`))
                }
            }

            if (!plaintext) {
                reject(new Error(`No public keys could be fetched using WKD`))
            }

            if (c) {
                await c.set(hash, plaintext.toString(), 60 * 1000)
            }
        }

        try {
            output.publicKey = await readKey({
                binaryKey: plaintext
            })
        } catch(error) {
            reject(new Error(`No public keys could be read from the data fetched using WKD`))
        }

        if (!output.publicKey) {
            reject(new Error(`No public keys could be read from the data fetched using WKD`))
        }

        resolve(output)
    })
}

const fetchHKP = (id, keyserverDomain) => {
    return new Promise(async (resolve, reject) => {
        let output = {
            publicKey: null,
            fetchURL: null
        }

        keyserverDomain = keyserverDomain ? keyserverDomain : 'keys.openpgp.org'

        let query = ''
        if (id.includes('@')) {
            query = id
        } else {
            query = `0x${id}`
        }

        output.fetchURL = `https://${keyserverDomain}/pks/lookup?op=get&options=mr&search=${query}`

        const hash = createHash('md5').update(`${id}__${keyserverDomain}`).digest('hex')

        if (c && await c.get(hash)) {
            output.publicKey = await readKey({
                armoredKey: await c.get(hash)
            })
        } else {
            try {
                output.publicKey = await doipjs.keys.fetchHKP(id, keyserverDomain)
            } catch(error) {
                reject(new Error(`No public keys could be fetched using HKP`))
            }
        }

        if (!output.publicKey) {
            reject(new Error(`No public keys could be fetched using HKP`))
        }

        if (c) {
            await c.set(hash, output.publicKey.armor(), 60 * 1000)
        }

        resolve(output)
    })
}

const fetchSignature = (signature) => {
    return new Promise(async (resolve, reject) => {
        let output = {
            publicKey: null,
            fetchURL: null,
            keyData: null
        }

        // Check validity of signature
        let signatureData
        try {
            signatureData = await readCleartextMessage({
                cleartextMessage: signature
            })
        } catch (error) {
            reject(new Error(`Signature could not be properly read (${error.message})`))
        }

        // Process the signature
        try {
            output.keyData = await doipjs.signatures.process(signature)
            output.publicKey = output.keyData.key.data
            // TODO Find the URL to the key
            output.fetchURL = null
        } catch(error) {
            reject(new Error(`Signature could not be properly read (${error.message})`))
        }

        // Check if a key was fetched
        if (!output.publicKey) {
            reject(new Error(`No public keys could be fetched`))
        }

        // Check validity of signature
        const verified = await verify({
            message: signatureData,
            verificationKeys: output.publicKey
        })
        
        if (!await verified.signatures[0].verified) {
            reject(new Error('Signature was invalid'))
        }

        resolve(output)
    })
}

const fetchKeybase = (username, fingerprint) => {
    return new Promise(async (resolve, reject) => {
        let output = {
            publicKey: null,
            fetchURL: null
        }

        try {
            output.publicKey = await doipjs.keys.fetchKeybase(username, fingerprint)
            output.fetchURL = `https://keybase.io/${username}/pgp_keys.asc?fingerprint=${fingerprint}`
        } catch(error) {
            reject(new Error(`No public keys could be fetched from Keybase`))
        }

        if (!output.publicKey) {
            reject(new Error(`No public keys could be fetched from Keybase`))
        }

        resolve(output)
    })
}

export { fetchWKD }
export { fetchHKP }
export { fetchSignature }
export { fetchKeybase }