RE: potential bug in GMAC implementation. not work in ESN mode

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Thanks Jussi, the patch fixes the problem.

You may commit it officially.

-----Original Message-----
From: Jussi Kivilinna [mailto:jussi.kivilinna@xxxxxx] 
Sent: Tuesday, March 26, 2013 4:16 PM
To: Chaoxing Lin
Cc: linux-crypto@xxxxxxxxxxxxxxx
Subject: Re: potential bug in GMAC implementation. not work in ESN mode

On 25.03.2013 18:12, Chaoxing Lin wrote:
> 2nd ping....
> 
> Nobody is maintaining crypto/gcm.c?
> 
> 
> 
> -----Original Message-----
> From: Chaoxing Lin
> Sent: Friday, March 08, 2013 11:38 AM
> To: 'linux-crypto@xxxxxxxxxxxxxxx'
> Subject: potential bug in GMAC implementation. not work in ESN mode
> 
> I was testing ipsec with GMAC and found that the rfc4543 GMAC implementation in kernel software crypto work in "esp=aes256gmac-noesn!" mode.
> It does not work in in "esp=aes256gmac-esn!" mode. The tunnel was established but no data traffic is possible.
> 
> Looking at source code, I found this piece of code is suspicious.
> Line 1146~1147 tries to put req->assoc to assoc[1]. But I think this way only works when req->assoc has only one segment. In ESN mode, req->assoc contains 3 segments (SPI, SN-hi, SN-low). Line 1146~1147 will only attach SPI segment(with total length) in assoc.
> 
> Please let me know whether I understand it right.

Your analysis seems correct. Does attached the patch fix the problem? (I've only compile tested it.)

-Jussi

> Thanks,
> 
> Chaoxing
> 
> 
> Source from kernel 3.8.2
> path: root/crypto/gcm.c
> 
> 1136: /* construct the aad */
> 1137:	dstp = sg_page(dst);
> 	vdst = PageHighMem(dstp) ? NULL : page_address(dstp) + dst->offset;
> 
> 	sg_init_table(payload, 2);
> 	sg_set_buf(payload, req->iv, 8);
> 	scatterwalk_crypto_chain(payload, dst, vdst == req->iv + 8, 2);
> 	assoclen += 8 + req->cryptlen - (enc ? 0 : authsize);
> 
> 	sg_init_table(assoc, 2);
> 1146:	sg_set_page(assoc, sg_page(req->assoc), req->assoc->length,
> 1147:		    req->assoc->offset);
> 	scatterwalk_crypto_chain(assoc, payload, 0, 2);
> 
> 	aead_request_set_tfm(subreq, ctx->child);
> 	aead_request_set_callback(subreq, req->base.flags, req->base.complete,
> 				  req->base.data);
> 	aead_request_set_crypt(subreq, cipher, cipher, enc ? 0 : authsize, iv);
> 1154:	aead_request_set_assoc(subreq, assoc, assoclen);
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