linux-kernel - Re: [PATCH] crypto: fix handling of ccm vectors with null assoc data

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Date:	Wed, 21 Jan 2009 20:07:22 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	Jarod Wilson <jarod@...hat.com>
Cc:	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH] crypto: fix handling of ccm vectors with null assoc
	data

On Wed, Jan 21, 2009 at 04:41:01PM -0500, Jarod Wilson wrote:
> Its a valid use case to have null associated data in a ccm vector, but
> this case isn't being handled properly right now.
> 
> The following ccm decryption/verification test vector, using the
> rfc4309 implementation regularly triggers a panic, as will any
> other vector with null assoc data:
> 
> * key: ab2f8a74b71cd2b1ff802e487d82f8b9
> * iv: c6fb7d800d13abd8a6b2d8
> * Associated Data: [NULL]
> * Tag Length: 8
> * input: d5e8939fc7892e2b
> 
> The resulting panic looks like so:
> 
> Unable to handle kernel paging request at ffff810064ddaec0 RIP: 
>  [<ffffffff8864c4d7>] :ccm:get_data_to_compute+0x1a6/0x1d6
> PGD 8063 PUD 0 
> Oops: 0002 [1] SMP 
> last sysfs file: /module/libata/version
> CPU 0
> Modules linked in: crypto_tester_kmod(U) seqiv krng ansi_cprng chainiv rng ctr aes_generic aes_x86_64 ccm cryptomgr testmgr_cipher testmgr aead crypto_blkcipher crypto_a
> lgapi des ipv6 xfrm_nalgo crypto_api autofs4 hidp l2cap bluetooth nfs lockd fscache nfs_acl sunrpc ip_conntrack_netbios_ns ipt_REJECT xt_state ip_conntrack nfnetlink xt_
> tcpudp iptable_filter ip_tables x_tables dm_mirror dm_log dm_multipath scsi_dh dm_mod video hwmon backlight sbs i2c_ec button battery asus_acpi acpi_memhotplug ac lp sg 
> snd_intel8x0 snd_ac97_codec ac97_bus snd_seq_dummy snd_seq_oss joydev snd_seq_midi_event snd_seq snd_seq_device snd_pcm_oss snd_mixer_oss ide_cd snd_pcm floppy parport_p
> c shpchp e752x_edac snd_timer e1000 i2c_i801 edac_mc snd soundcore snd_page_alloc i2c_core cdrom parport serio_raw pcspkr ata_piix libata sd_mod scsi_mod ext3 jbd uhci_h
> cd ohci_hcd ehci_hcd
> Pid: 12844, comm: crypto-tester Tainted: G      2.6.18-128.el5.fips1 #1
> RIP: 0010:[<ffffffff8864c4d7>]  [<ffffffff8864c4d7>] :ccm:get_data_to_compute+0x1a6/0x1d6
> RSP: 0018:ffff8100134434e8  EFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffff8100104898b0 RCX: ffffffffab6aea10
> RDX: 0000000000000010 RSI: ffff8100104898c0 RDI: ffff810064ddaec0
> RBP: 0000000000000000 R08: ffff8100104898b0 R09: 0000000000000000
> R10: ffff8100103bac84 R11: ffff8100104898b0 R12: ffff810010489858
> R13: ffff8100104898b0 R14: ffff8100103bac00 R15: 0000000000000000
> FS:  00002ab881adfd30(0000) GS:ffffffff803ac000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: ffff810064ddaec0 CR3: 0000000012a88000 CR4: 00000000000006e0
> Process crypto-tester (pid: 12844, threadinfo ffff810013442000, task ffff81003d165860)
> Stack:  ffff8100103bac00 ffff8100104898e8 ffff8100134436f8 ffffffff00000000
>  0000000000000000 ffff8100104898b0 0000000000000000 ffff810010489858
>  0000000000000000 ffff8100103bac00 ffff8100134436f8 ffffffff8864c634
> Call Trace:
>  [<ffffffff8864c634>] :ccm:crypto_ccm_auth+0x12d/0x140
>  [<ffffffff8864cf73>] :ccm:crypto_ccm_decrypt+0x161/0x23a
>  [<ffffffff88633643>] :crypto_tester_kmod:cavs_test_rfc4309_ccm+0x4a5/0x559
> [...]
> 
> The above is from a RHEL5-based kernel, but upstream is susceptible too.
> 
> The fix is trivial: in crypto/ccm.c:crypto_ccm_auth(), pctx->ilen contains
> whatever was in memory when pctx was allocated if assoclen is 0. The tested
> fix is to simply add an else clause setting pctx->ilen to 0 for the
> assoclen == 0 case, so that get_data_to_compute() doesn't try doing
> things its not supposed to.
> 
> Signed-off-by: Jarod Wilson <jarod@...hat.com>
> 


This looks good to me.  Thanks Jarod!
Acked-by: Neil Horman <nhorman@...driver.com>

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