TypeScript-Core functionality to verify signatures

[tomholub]

prerequisite for #278

parseDecryptMsg currently accepts these values: { keys: PrvKeyInfo[], msgPwd: string?, isEmail: boolean }

I'd like to add optional verificationPubkeys: string[]? which will accept an array of armored public keys.

This will get passed into:

const decryptRes = await PgpMsg.decrypt({ kisWithPp, msgPwd, encryptedData: Buf.with(rawBlock.content) });
// which is
public static decrypt: PgpMsgMethod.Decrypt = async ({ kisWithPp, encryptedData, msgPwd }) => {

in the PgpMsg.decrypt method you need to edit const keys = await PgpMsg.getSortedKeys(kisWithPp, prepared.message); to accept this array as well (optionally - can be undefined), which means updating the signature of private static getSortedKeys = async (kiWithPp: PrvKeyInfo[], msg: OpenpgpMsgOrCleartext): Promise<SortedKeysForDecrypt> => { to accept it.

Then finally in getSortedKeys, this line:

await PgpMsg.cryptoMsgGetSignedBy(msg, keys);

should be changed to something like:

if(typeof verificationPubkeys !== 'undefined') {
  keys.forVerification = [];
  for (const verificationPubkey of verificationPubkeys) {
    const { keys: keysForVerification } = await openpgp.key.readArmored(verificationPubkey);
    keys.forVerification.push(...keysForVerification);
  }
} else {
  await PgpMsg.cryptoMsgGetSignedBy(msg, keys);
}

Then please remove everything related to keys.verificationContacts, which includes changing singature of PpgMsg.verify to not accept a Contact? and not return it either.

Once you do all that, and run parseDecryptMsg, you should see it return verification results automatically.

This issue should involve the following tests:

• verify encrypted+signed message by providing it correct public key (pass)
• verify encrypted+signed message by providing it one wrong and one correct (pass)
• verify encrypted+signed message by providing it only a wrong public key (fail: cannot verify)
• verify plain-text signed message by providing it correct key (pass)
• verify plain-text signed message by providing it wrong key (fail: cannot verify)
• verify plain-text signed message that you edited after signing. This invalidates the signature. With correct key. (fail: signature mismatch)

[IvanPizhenko]

@tomholub Is there a difference between:

if (typeof verificationPubkeys !== 'undefined')

and

if (verificationPubkeys !== undefined)

?

[IvanPizhenko]

@tomholub Are there ready test messages that I can use or I need to create new ones?

[tomholub]

@tomholub Are there ready test messages that I can use or I need to create new ones?

You may be able to create most of them by editing https://github.com/FlowCrypt/flowcrypt-ios/blob/master/Core/source/gen-compat-assets.ts and then running it.

[tomholub]

@tomholub Is there a difference between:

if (typeof verificationPubkeys !== 'undefined')

and

if (verificationPubkeys !== undefined)

?

The second one will throw exception in strict mode if the value actually hasn't been defined at all --- as opposed to defined but assigned with undefined (let x = undefined;) or defined without assigning value (let x;).

[tomholub]

javascript is full of footguns, and that's why the compiler and linter will warn you away from these. x === undefined is one of the many.

[IvanPizhenko]

@tomholub in https://github.com/FlowCrypt/flowcrypt-ios/blob/master/Core/source/gen-compat-assets.ts - what does mean this email header:

Openpgp: id=6D24791A5B106262B06217C606CA553EC2455D70

is it:

• a fingerprint of the sender's key
• a fingerprint of the recepient's key
• something else?

[tomholub]

Fingerprint of the sender's key. But currently unused, and does not need to be tested.

[IvanPizhenko]

@tomholub There's a problem with writing tests, at least for the first 3 cases, (I didn't try other 3 yet). Signature verification result exists inside parseDecryptMsg(), however then it is lost through multiple transformations. In particular,

      } else if (rawBlock.type === 'encryptedMsg' || rawBlock.type === 'signedMsg') {
        const decryptRes = await PgpMsg.decrypt({ kisWithPp, msgPwd, encryptedData: Buf.with(rawBlock.content), verificationPubkeys });
        console.log(">>>> " + JSON.stringify(decryptRes));
        if (decryptRes.success) {
          if (decryptRes.isEncrypted) {
            const formatted = await MsgBlockParser.fmtDecryptedAsSanitizedHtmlBlocks(decryptRes.content);
            sequentialProcessedBlocks.push(...formatted.blocks);
            subject = formatted.subject || subject;
          } else {

prints out json like this, when signature was verified:

{"success":true,"content":{"0":115,"1":111,"2":109,"3":101,"4":10,"5":230,"6":177,"7":137,"8":10,"9":116,"10":120,"11":116},"isEncrypted":true,"filename":"msg.txt","signature":{"match":true,"signer":"3A30F4CC0A9A8F10"}}

and like this:

{"success":true,"content":{"0":115,"1":111,"2":109,"3":101,"4":10,"5":230,"6":177,"7":137,"8":10,"9":116,"10":120,"11":116},"isEncrypted":true,"filename":"msg.txt","signature":{"match":null,"signer":"3A30F4CC0A9A8F10"}}

when signature could not be verified. However, this never gets out of parseDecryptMsg.

[tomholub]

I suppose you would have to pass that signature into fmtDecryptedAsSanitizedHtmlBlocks and then add the signature into SanitizedBlocks type. And similarly onwards, until it bubbles through.

[IvanPizhenko]

@tomholub I've implemented all tests mentioned above and they are passing now, but I am trying to add one more test for the "detached" signature and it fails. First, there is big question for me how to generate correctly email message with detached signature. At this moment I've ended up with generating something like this:

Delivered-To: flowcrypt.compatibility@gmail.com
Return-Path: <flowcrypt.compatibility@gmail.com>
Openpgp: id=E76853E128A0D376CAE47C143A30F4CC0A9A8F10
From: flowcrypt.compatibility@gmail.com
MIME-Version: 1.0
Date: Thu, 2 Nov 2017 17:54:14 -0700
Message-ID: <CANzaQHU9A@mail.gmail.com>
Subject: mime email plain signed detached
To: flowcrypt.compatibility@gmail.com
Content-Type: text/plain; charset="UTF-8"

some
汉
txt

-----BEGIN PGP SIGNATURE-----
Version: FlowCrypt [BUILD_REPLACEABLE_VERSION] Gmail Encryption
Comment: Seamlessly send and receive encrypted email

wsBcBAEBCAAGBQJhZKj9AAoJEDow9MwKmo8Q9GAH/0VkC/MbhTkCjpvQ0PVQ
WVd+/lpDyOzB/6paHdY7aKeSSlXF9W5t3G3R+azv41WLW+J9J/wrh3TNtMWl
WA7Wz0VSzjp0CbJDNh67IeyooT1rQ98IADXD8zQk5lv2MogzaKqjjhenWRYD
YXDmfYzrj9pPa/p7qombWtiKxNLS16mTubd/ae2NSIAN6P0q5NipMbyBw+Wc
jnZroTErhZrVgQRNQRfODI8uIkA6gU2lff5742jAZEWhQDIREPTNqgoC3OiY
HDTk4LlG1eavKJLCyHFRdO6BOStf5fDwh+04BZtwzfRs48svg69Iza9L+IMX
GMKMMBmjDsQlzYUf6S+3WZ0=
=XKCS
-----END PGP SIGNATURE-----

But this is parsed into MsgBlock not as I would expect:

{"type":"plainText","content":"some\n汉\ntxt\n\n-----BEGIN PGP SIGNATURE-----\nVersion: FlowCrypt [BUILD_REPLACEABLE_VERSION] Gmail Encryption\nComment: Seamlessly send and receive encrypted email\n\nwsBcBAEBCAAGBQJhZKj9AAoJEDow9MwKmo8Q9GAH/0VkC/MbhTkCjpvQ0PVQ\nWVd+/lpDyOzB/6paHdY7aKeSSlXF9W5t3G3R+azv41WLW+J9J/wrh3TNtMWl\nWA7Wz0VSzjp0CbJDNh67IeyooT1rQ98IADXD8zQk5lv2MogzaKqjjhenWRYD\nYXDmfYzrj9pPa/p7qombWtiKxNLS16mTubd/ae2NSIAN6P0q5NipMbyBw+Wc\njnZroTErhZrVgQRNQRfODI8uIkA6gU2lff5742jAZEWhQDIREPTNqgoC3OiY\nHDTk4LlG1eavKJLCyHFRdO6BOStf5fDwh+04BZtwzfRs48svg69Iza9L+IMX\nGMKMMBmjDsQlzYUf6S+3WZ0=\n=XKCS\n-----END PGP SIGNATURE-----","complete":true}

Call const signed = await PgpMsg.sign(signingPrv, data, true); returns only signature block itself.
But how should I put it into email message?