Fix issue with buffer concatenation while using scrypt

[chaitanyapotti]

While using scrypt, derivedKey is of type Uint8Array. While concatenating, Buffer checks for isBuffer and throws.!
This PR fixes that

[coveralls]

Coverage remained the same at 86.601% when pulling 9b5f5fe on torusresearch:master into 0681d67 on ethereumjs:master.

[FrederikBolding]

👍

[holgerd77]

Hi @chaitanyapotti, thanks for the fix! Do you have got any idea why this was not caught by the fromV3 related tests like here, especially since the tests are also executed with Karma within a browser context on CI with the test:browser script from package.json?

If you have got an idea, could you provide a simple test case along which would have failed without your fix? Thanks!

[chaitanyapotti]

Here's a simple repro case.
steps:

• build using npm run build:webpack
• serve index.html using serve/ python
• look at console

Most of us use webpack for bundling and hence are facing the issue.
Karma-typescript uses Buffer v5 shim whereas webpack 4 uses Buffer v4 shim.
As you can see here, support for Uint8Array in concat was added in 5.1.0 of Buffer.

I hope this explains the issue

[holgerd77]

@chaitanyapotti Thanks, that's a great explanation! 😄

Will merge here and prepare a bugfix release during the week, eventually we will include 1-2 other things.

[holgerd77]

LGTM

[holgerd77]

Just to let you know: we'll finish on some investigation being done right now in #138 around failing CI tests also happened here before we will do a bugfix release.

[holgerd77]

Sorry guys, we thought we could fix #138 along the road but we couldn't identify the root cause there yet. I'll know skip this and do a release separate from the Node 14 fix, have prepared the according release PR: #139

[holgerd77]

(so therefore the delay)