On Mon, 2015-06-01 at 15:49 +0200, Stephan Mueller wrote: > >The contents, now, that's a more interesting question. I believe it can > >never be all zeroes, since association request frames are not > >encrypted/protected and thus at least one byte in here must be non-zero. > >The MAC addresses are also very likely non-zero, but technically > >00:00:00:00:00:00 is a valid MAC address I believe. > > So, even when having a malicious AP, that value is never zero? The driver of > the question is the following code in the patch set: > > + sg_set_buf(&sg[0], &aad[2], be16_to_cpup((__be16 *)aad)); > > ... > > + aead_request_set_crypt(aead_req, sg, sg, data_len, b_0); > > ... > > crypto_aead_encrypt(aead_req); > > > When I played around with the aead_request_set_crypt, I saw a crash in the > scatterlist handling of the crypto API when the first SGL entry has a zero > length. Wait, I guess that's a *third* way for this to be "zero" a valid pointer but zero length data? Oh, no - you're referring to the CCM/GCM cases only, I guess, i.e. this part: - sg_init_one(&assoc, &aad[2], be16_to_cpup((__be16 *)aad)); + sg_set_buf(&sg[0], &aad[2], be16_to_cpup((__be16 *)aad)); I was looking at GMAC and that has a constant for the length :-) Ok - here the length is kinda passed a part of the AAD buffer, but this is really just some arcane code that should be fixed to use a proper struct. The value there, even though it is __be16 and looks like it came from the data, is actually created locally, see ccmp_special_blocks() and gcmp_special_blocks(). johannes -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
