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Magic-Wormhole – Get things from one computer to another, safely

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Re: Magic-Wormhole – Get things from one computer to another, safely

#61

Post by benzinschleuder »

lotharrr wrote: post #49
benzinschleuder wrote: post #41

Earlier quoted context omitted.

Does the session key hash help if the attacker guessed the code correctly?

Yup, it still does. In the face of a lucky-guessing attacker, PAKE basically degenerates down into plain unauthenticated Diffie-Hellman, which means Alice-Mallory has one key, and Mallory-Bob has a different key. Mallory could decrypt the messages from Alice and then reencrypt them for Bob, but Alice and Bob will still both see different keys. If they have some out-of-band means to compare those keys (which Mallory c…

Thanks!

Re: Magic-Wormhole – Get things from one computer to another, safely

#62

Post by lotharrr »

tonyhb wrote: post #57
daxorid wrote: post #50

So, basically, scp (with a 16-bit session key that has to be exchanged oob)?

or, like, netcat? `nc -l -p 8888 > foo` to listen, `nc 10.10.10.1 8888 Still cool though :)

yup, except with netcat:

* the network-side attacker gets to see and modify all your data * the receiver must have a public IP address * the receiver must tell something to the sender, which is the opposite of the direction the data will flow * you have to transcribe your IP address and port number to the other person, which I always get wrong (so many meaningless numbers!) * you don't get much confirmation that all the data arrived, or that it arrived accurately

The wormhole code uses a wordlist that was carefully designed (not by me.. I'm using the PGP wordlist, as used by PGPfone and Zfone) for accurate spoken transcription in noisy environments. So it's more likely that they'll type in the right thing.

Re: Magic-Wormhole – Get things from one computer to another, safely

#63

Post by meejah »

0x0 wrote: post #53
meejah wrote: post #46

Earlier quoted context omitted.

The attacker still just gets 1 guess per wormhole / send request. Each send-request / wormhole is its own separate thing.

I'm still unclear on a couple of things. How do you even know which send request the attacker attempted to attack if only the codeword identifies the send request, and the codeword was wrong? Also, what stops an attacker from trying again - alternatively, what stops an attacker from doing a denial-of-service by purposefully guessing the wrong codeword?

The codes have a small number in front; these are the requests. So if the server did allow 65k requests, each one would be a different number. You can guess once per request.

Yes, an attacker can denial-of-service by guessing once on all the (possible) requests. There is some work towards stopping this sort of behavior (see e.g. https://github.com/warner/magic-wormhole/issues/126)

Re: Magic-Wormhole – Get things from one computer to another, safely

#64

Post by 0x0 »

meejah wrote: post #63
0x0 wrote: post #53

Earlier quoted context omitted.

I'm still unclear on a couple of things. How do you even know which send request the attacker attempted to attack if only the codeword identifies the send request, and the codeword was wrong? Also, what stops an attacker from trying again - alternatively, what stops an attacker from doing a denial-of-service by purposefully guessing the wrong codeword?

The codes have a small number in front; these are the requests. So if the server did allow 65k requests, each one would be a different number. You can guess once per request. Yes, an attacker can denial-of-service by guessing once on all the (possible) requests. There is some work towards stopping this sort of behavior (see e.g. https://github.com/warner/magic-wormhole/issues/126 )

Thanks for the explanation!

Re: Magic-Wormhole – Get things from one computer to another, safely

#66

Post by mschuster91 »

bhenc wrote: post #60

> Copying files with ssh/scp is fine, but requires previous arrangements and an account on the target machine, and how do you bootstrap the account?~ Assuming that you have openssh and rssh installed, you bootstrap like this: useradd -m -g users -s /usr/bin/rssh tmp passwd tmp edit /etc/rssh.conf and uncomment allowscp Share the password with the party you want to exchange data with. Make sure your ports are open. Se…

When both parties are in a corp network (eg across companies) you would need a server anyway. Many either offer a FTP server or have switched to Accellion (which is kinda cr.p, and full of security holes)... so this is a nice, fast and secure alternative.

Re: Magic-Wormhole – Get things from one computer to another, safely

#68

Post by dmd »

bhenc wrote: post #60

> Copying files with ssh/scp is fine, but requires previous arrangements and an account on the target machine, and how do you bootstrap the account?~ Assuming that you have openssh and rssh installed, you bootstrap like this: useradd -m -g users -s /usr/bin/rssh tmp passwd tmp edit /etc/rssh.conf and uncomment allowscp Share the password with the party you want to exchange data with. Make sure your ports are open. Se…

> you bootstrap like this

Ah, yes. oh come on please it's easy just /etc/init.apt-get/frob-set-conf --arc=0 - +/lib/syn.${SETDCONPATH}.so.4.2 even my grandma can do that

Re: Magic-Wormhole – Get things from one computer to another, safely

#69

Post by bhenc »

mschuster91 wrote: post #66
bhenc wrote: post #60

> Copying files with ssh/scp is fine, but requires previous arrangements and an account on the target machine, and how do you bootstrap the account?~ Assuming that you have openssh and rssh installed, you bootstrap like this: useradd -m -g users -s /usr/bin/rssh tmp passwd tmp edit /etc/rssh.conf and uncomment allowscp Share the password with the party you want to exchange data with. Make sure your ports are open. Se…

When both parties are in a corp network (eg across companies) you would need a server anyway. Many either offer a FTP server or have switched to Accellion (which is kinda cr.p, and full of security holes)... so this is a nice, fast and secure alternative.

That is a good use case.
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