Re: [Sks-devel] Proposal: Start verifying self-signatures

[Daniel Roesler]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On May 17, 2015, Kristian Fiskerstrand wrote:
>> 2. Prevents denial of service attacks that allows Mallory to
>> spam a bunch of new subkeys, user ids, or huge images onto a
>> public key.
>
> Please elaborate on how this is a DoS, I can see it being
> un-appealing, but for it to qualify as a DoS the bar is higher
> than that.

A User Attribute subpacket can be up to 256^4 bytes long[1],
which means that a someone can upload a 4.2 GB jpeg onto your
public key and then when gpg --recv-key tries to retreive your
public key, it will have download a huge, overbloated file that
you did not add yourself.

This is a DOS because Mallory could effectively increase Alice's
public key to a size that it would be untenable for Bob to
download it from the pool.

Daniel

[1]: https://tools.ietf.org/html/rfc4880#section-5.12

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
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=kOYQ
-----END PGP SIGNATURE-----