control channel???

Andreas Metzler ametzler at
Sat Jan 13 20:12:02 CET 2007

Tavis Ormandy <taviso at> wrote:
> Bernhard Reiter <bernhard at> wrote:
>> There is some criticism by Felix von Leitner about the gnupg code in
>> German:

> I audited the code in question in detail a few months ago, and found
> no problems. I cant read german, but if he is complaining about the
> volatile trick, I suspect it is used so as not to deplete any entropy
> pool, which seems perfectly reasonable to me (it doesnt buy an attacker
> any advantage if he can guess it).

> Id be interested to hear any attack I might have missed, could any
> german speakers give a rough translation?

| [code snippet]
| Ich habe da genau so viel Kontext wie ihr, aber ich würde das so
| interpretieren, daß Herr Koch hier ein Protokoll mit in-band
| signalling gebaut hat, und ein Angreifer hier Pakete einfügen kann,
| und er will das jetzt "reparieren", indem er "Zufallswerte" einfügt,
| die der Angreifer nicht raten können soll.
| Also ich könnte euch jetzt erzählen, daß Werte auf dem Stack alles
| andere als zufällig sind, daß PID und Uhrzeit auch eher gut ratbar
| sind, aber die eigentliche Nachricht ist: gnupg hat einen "control
| channel", der in-band signalling benutzt, und auf dem Angreifer Daten
| einschleusen können. Mehr muß man nicht sagen. Und diesen Müll-Code
| habe ich seit Jahren eingesetzt! OMFG! Ich glaube nicht, daß das mit
| einem Patch fixbar ist. Wegschmeißen, neu machen. Im Übrigen schreibt
| man das "although", nicht "also". 

[code snippet]
I have got as much context as you but I think that Mr Koch has created
a protocol with in-band signaling and that an attacker could insert
packages here. Mr Koch seems to be trying to "repair" this by
inserting "random values" which the attacker should not be able to

Well, I could start telling you that values on the stack are very much
not random and that PID and time are rather well guessable, too but
the real message is this one: gnupg has got a "control channel" which
is using in-band signalling and which could be used by an attacker to
insert packets. That is all there is to say. I do not think this is
fixable at all. Throw away, rewrite. An BTW the comment should say
"although" instead of "also".

I probably made some errors when translating so please take with a
heap of salt.
cu andreas
The 'Galactic Cleaning' policy undertaken by Emperor Zhark is a personal
vision of the emperor's, and its inclusion in this work does not constitute
tacit approval by the author or the publisher for any such projects,
howsoever undertaken.                                (c) Jasper Ffforde

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