Golang mime/quotedprintable: support message with long lines

What version of Go are you using (go version)?

$ go version
go version go1.14.5 darwin/amd64

Does this issue reproduce with the latest release?

Yes.

What operating system and processor architecture are you using (go env)?

$ go env

What did you do?

Tried to parse message which does not follow RFC to not having longer than 76 characters (has 4953 characters). Currently, quotedprintable is using bufio.Reader which fails on line longer than ~4k characters because of the bufio.Rader default limit.

What did you expect to see?

Even though it's not a message following RFC, it's better to parse it anyway as there is no reason not to support it.

What did you see instead?

Message cannot be parsed.

Comment From: cagedmantis

Could you provide an example of the code that produced the error, preferably as a Go playground link?

Comment From: networkimprov

cc @minux @bradfitz @neild

Comment From: Lazyshot

We are also seeing this behavior.

https://play.golang.org/p/mNwpwJRrqkn

It's causing some other side affects. Specifically for textproto and bufio:

https://play.golang.org/p/WzCbLdVg0pj

The second play will always timeout because of an infinite loop. This appears to be due to the fact that once the reader encounters a buffer full error, it will always return that error on all subsequent calls.

Comment From: networkimprov

@gopherbot remove WaitingForInfo

Comment From: cagedmantis

/cc @bradfitz @minux

Comment From: gopherbot

Change https://go.dev/cl/705655 mentions this issue: mime/quotedprintable: support long lines