gpg-agent and allow-loopback-pinentry

[Patrick Brunschwig]

On 02.01.15 14:18, Werner Koch wrote:
> On Tue, 30 Dec 2014 23:33, dkg at fifthhorseman.net said:
> 
>> to be honest, when i've watched users set up enigmail with GnuPG for the
>> first time, they're often confused by the fact of a password for the key
>> in the first place.
> 
> Right, I bet that 80% of all users do not fully understand for what the
> passphrase is used.  It is even questionable whether a passphrase
> protected key is useful for a non-mobile computer given that attacker
> able to grab a protected key will in most cases also be able to
> install a keylogger.
> 
>> And an OpenPGP key by default is not the same thing as a web service,
>> either.
> 
> Right - Documentation should stree that point.
> 
>> What about generating the key with no passphrase initially, and
>> presenting a big "protect this key with a passphrase" button to the user
>> when no passphrase is set?
> 
> Given the above scenario I actually kind of like that.
> 
>>  * passphraseless keys will be written to the filesystem and might not
>> ever be erased.
>>
>>  * some users will never click the "protect this key with a passphrase"
>> button.
> 
> As an alternative we could keep the key in memory (gpg-agent is running
> in the background) and only write it to the disk once a change
> passphrase has been done.  We would also not allow to send the key to a
> keyserver before it has not been passphrase protected.
> 
> Instead of "please protect your key now" we could use a "you now need to
> test your key" and in course of that setup a passphrase.  Creating a
> signed message and decrypt an automagically created message would also
> help to remember the passphrase.
> 
>>  * it's not clear to me whether there's an easy way for enigmail to tell
>> whether the secret key in question has a passphrase set on it or not
> 
> gpg-agent has this command:
> 
>   > help keyinfo
>   # KEYINFO [--[ssh-]list] [--data] [--ssh-fpr] [--with-ssh] <keygrip>
> 
>   #   KEYINFO <keygrip> <type> <serialno> <idstr> <cached> <protection> <fpr>
> 
>   # PROTECTION describes the key protection type:
>   #     'P' - The key is protected with a passphrase,
>   #     'C' - The key is not protected,
>   #     '-' - Unknown protection.
> 
> Enigmail can use it via gpg-connect-agent to check for a key or we can
> add a wrapper command to gpg.  If a keep-in-memory-until-passwd approach
> would be implemented this command can also be used to return relevant
> info.
> 
>> I don't know if there are any usability studies that would help make
>> this decision easier.
> 
> Anyone who has time to research this?

We recently had a usability study on Enigmail done by a German
University (I'm not sure if I'm allowed to publish the name, so I
don't). Enigmail has a setup wizard (which generates a key if needed),
and recommendation was to design the key creation dialog as follows:

----------------------------------------
*Key Creation*

Your _public key_ is used by others to send you encrypted messages. You
can be distribute it to anyone."

Your _private key_ is required for you to decrypt received mails and to
send signed mails. You should not give it to anyone. To secure your
private key, please enter a passphrase below.

*Important:* your passphrase is not your private key.

Passphrase        : [         ]
Confirm passphrase: [         ]

Password Quality:   [color bar]
----------------------------------------

I am right now modifying our wizard to look and work exactly this way.

-Patrick