[stunnel-users] hex key support for psk

[Michal Trojnara]

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On 29.10.2015 00:12, Reese Wilson wrote:
> I ran into an issue with PSK reading the key as ascii instead of
> hex. I had a gnutls-serv and gnutls-cli set up with a hex key, and
> I switched the server for one wrapped using stunnel, but using the
> same key in psk.txt was failing. I eventually got it working by
> converting the hex characters to binary and placing that in the
> contents of the file specified by PSKsecrets (psk.txt), but this
> won't work for certain scenarios. For example, what if the key
> contains ascii newline characters?

Do it the other way around: generate sufficiently long printable ASCII
pre-shared keys, and then hex-encode them for applications that
require hex-encoded pre-shared keys.  The same applies to any other
encoding (base64, rot13, etc.).

Yes, the interface of stunnel restricts the subset of bytes that may
be used for pre-shared keys (but not the length of those keys).  Yes,
this may require generating new pre-shared keys when you migrate to
stunnel from another product.  Yes, I consider this to be a feature.
You can use passphrases or your favourite password generator to
generate pre-shared keys for stunnel.  Changing the pre-shared key
when you migrate to stunnel is also *good* for your security.

Mike
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