Re: Message takeover attacks against S/MIME

I do not know of any user agents that can be configured to accept only intern message/rfc822 type, or even flag the difference to the user.  Most users would not understand the flag if it was there.

I would like to know if there is enough energy to work on a re-charter for the SMIME working group and then produce an updated specification.  If there is enough interest, Stephen Farrell is willing to sponsor the charter.

I am willing to work on it.

Russ


On Jan 28, 2016, at 5:02 AM, Lijun Liao wrote:

> Indeed there are much simple ways to get the encrypted messages by adding some header fields like Reply-To, Sender, To, CC, etc. Since these header fields are not cryptographically protected by the signature and encryption, the recipient mail client is not able to detect the modification. If she answers the email, a copy will be delivered to the attacker.
> 
> Sure the aforementioned attack can be HINDERED by the inline message type message/rfc822 introducted in S/MIME v3.1. I use here the word HINDER instead of PREVENT due to the fact that the specification does not prevent the recipient client from using the outer header fields which are not protected. By the way, not all of email clients (indeed I know none) can be configured to accept only intern message/rfc822 type.
> 
> Lijun Liao

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