Srivatsa -
I dug up an earlier note of yours - and yes you are correct, I verified that
crypto_shash_setkey is called with cmacaes set to NULL
You did good work isolating this - I had missed one of your important
earlier emails. I tried a similar approach - but calling
server->ops->generate_signingkey(ses)
later (before crypto_shash_setkey) which didn't work. So more than
one thing missing.
Aurelien/Pavel,
Ideas?
On Wed, Jan 3, 2018 at 6:15 PM, Srivatsa S. Bhat <srivatsa@xxxxxxxxxxxxx> wrote:
> On 11/1/17 8:18 AM, Greg Kroah-Hartman wrote:
>> On Tue, Oct 31, 2017 at 03:02:11PM +0200, Thomas Backlund wrote:
>>> Den 31.10.2017 kl. 11:55, skrev Greg Kroah-Hartman:
>>>> 4.13-stable review patch. If anyone has any objections, please let me know.
>>>>
>>>> ------------------
>>>>
>>>> From: Steve French <smfrench@xxxxxxxxx>
>>>>
>>>> commit 4587eee04e2ac7ac3ac9fa2bc164fb6e548f99cd upstream.
>>>>
>>>> According to MS-SMB2 3.2.55 validate_negotiate request must
>>>> always be signed. Some Windows can fail the request if you send it unsigned
>>>>
>>>> See kernel bugzilla bug 197311
>>>>
>>>> Acked-by: Ronnie Sahlberg <lsahlber.redhat.com>
>>>> Signed-off-by: Steve French <smfrench@xxxxxxxxx>
>>>> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>>>>
>>>> ---
>>>> fs/cifs/smb2pdu.c | 3 +++
>>>> 1 file changed, 3 insertions(+)
>>>>
>>>> --- a/fs/cifs/smb2pdu.c
>>>> +++ b/fs/cifs/smb2pdu.c
>>>> @@ -1963,6 +1963,9 @@ SMB2_ioctl(const unsigned int xid, struc
>>>> } else
>>>> iov[0].iov_len = get_rfc1002_length(req) + 4;
>>>> + /* validate negotiate request must be signed - see MS-SMB2 3.2.5.5 */
>>>> + if (opcode == FSCTL_VALIDATE_NEGOTIATE_INFO)
>>>> + req->hdr.sync_hdr.Flags |= SMB2_FLAGS_SIGNED;
>>>> rc = SendReceive2(xid, ses, iov, n_iov, &resp_buftype, flags, &rsp_iov);
>>>> cifs_small_buf_release(req);
>>>>
>>>>
>>>>
>>>
>>> This one needs to be backported to all stable kernels as the commit that
>>> introduced the regression:
>>> '
>>> 0603c96f3af50e2f9299fa410c224ab1d465e0f9
>>> SMB: Validate negotiate (to protect against downgrade) even if signing off
>>>
>>> is backported in stable trees as of: 4.9.53, 4.4.90, 3.18.73
>>
>> Oh wait, it breaks the builds on older kernels, that's why I didn't
>> apply it :)
>>
>> Can you provide me with a working backport?
>>
>
> Hi Steve,
>
> Is there a version of this fix available for stable kernels?
>
> I tried applying this patch to 4.4.109 (and a similar one for 4.9.74),
> but it didn't fix the problem. Instead, I actually got a NULL pointer
> dereference when I tried to mount an SMB3 share.
>
> Here is the patch I tried on 4.4.109:
>
> diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
> index f2ff60e..3963bd2 100644
> --- a/fs/cifs/smb2pdu.c
> +++ b/fs/cifs/smb2pdu.c
> @@ -1559,6 +1559,9 @@ SMB2_ioctl(const unsigned int xid, struct cifs_tcon *tcon, u64 persistent_fid,
> } else
> iov[0].iov_len = get_rfc1002_length(req) + 4;
>
> + /* validate negotiate request must be signed - see MS-SMB2 3.2.5.5 */
> + if (opcode == FSCTL_VALIDATE_NEGOTIATE_INFO)
> + req->hdr.Flags |= SMB2_FLAGS_SIGNED;
>
> rc = SendReceive2(xid, ses, iov, num_iovecs, &resp_buftype, 0);
> rsp = (struct smb2_ioctl_rsp *)iov[0].iov_base;
>
>
> This results in the following NULL pointer dereference when I try
> mounting:
>
> # mount -vvv -t cifs -o vers=3.0,credentials=.smbcred //<ip_addr>/TestSMB/ testdir
>
> [ 53.073057] BUG: unable to handle kernel NULL pointer dereference at 0000000000000050
> [ 53.073511] IP: [<ffffffff8138ee9a>] crypto_shash_setkey+0x1a/0xc0
> [ 53.073973] PGD 0
> [ 53.074427] Oops: 0000 [#1] SMP
> [ 53.074946] Modules linked in: arc4(E) ecb(E) md4(E) cifs(E) dns_resolver(E) vmw_vsock_vmci_transport(E) vsock(E) hid_generic(E) usbhid(E) hid(E) xt_conntrack(E) mousedev(E) iptable_nat(E) nf_conntrack_ipv4(E) nf_defrag_ipv4(E) nf_nat_ipv4(E) nf_nat(E) iptable_filter(E) ip_tables(E) crc32c_intel(E) xt_LOG(E) nf_conntrack(E) jitterentropy_rng(E) hmac(E) sha256_ssse3(E) sha256_generic(E) drbg(E) vmw_balloon(E) ansi_cprng(E) aesni_intel(E) aes_x86_64(E) glue_helper(E) lrw(E) gf128mul(E) ablk_helper(E) cryptd(E) psmouse(E) evdev(E) uhci_hcd(E) ehci_pci(E) ehci_hcd(E) usbcore(E) intel_agp(E) usb_common(E) vmw_vmci(E) i2c_piix4(E) intel_gtt(E) nfit(E) battery(E) tpm_tis(E) tpm(E) ac(E) button(E) sch_fq_codel(E) autofs4(E)
> [ 53.079435] CPU: 3 PID: 829 Comm: mount.cifs Tainted: G E 4.4.109-possible-fix1+ #21
> [ 53.079983] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 04/05/2016
> [ 53.081086] task: ffff8800b4f41940 ti: ffff8800b92ac000 task.ti: ffff8800b92ac000
> [ 53.081667] RIP: 0010:[<ffffffff8138ee9a>] [<ffffffff8138ee9a>] crypto_shash_setkey+0x1a/0xc0
> [ 53.082247] RSP: 0018:ffff8800b92af9a8 EFLAGS: 00010282
> [ 53.082604] systemd-journald[284]: Compressed data object 721 -> 468 using XZ
> [ 53.083419] RAX: ffff8800af5943c0 RBX: ffff8800b484a800 RCX: 00000000ffff0ec7
> [ 53.084001] RDX: 0000000000000010 RSI: ffff8800b900af18 RDI: 0000000000000000
> [ 53.084602] RBP: ffff8800b92af9e0 R08: ffff8800b92afb64 R09: 0000000000000000
> [ 53.085184] R10: 3031322e3030312e R11: 00000000000007f5 R12: 0000000000000002
> [ 53.085755] R13: 0000000000000000 R14: ffff8800b900af18 R15: 0000000000000010
> [ 53.086333] FS: 00007fb659b45740(0000) GS:ffff88013fcc0000(0000) knlGS:0000000000000000
> [ 53.086907] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 53.087480] CR2: 0000000000000050 CR3: 00000000b7970000 CR4: 00000000001606e0
> [ 53.088107] Stack:
> [ 53.088681] ffff8800bba5d8c0 ffff8800b92afa08 ffff8800b484a800 0000000000000002
> [ 53.089281] ffff8800b92afac8 000008012400007d ffff8800b484a800 ffff8800b92afa50
> [ 53.089871] ffffffffa02194a6 ffff8800b92afb70 ffff8800af5943c0 ffff8800b7a2f800
> [ 53.090457] Call Trace:
> [ 53.091054] [<ffffffffa02194a6>] smb3_calc_signature+0xb6/0x290 [cifs]
> [ 53.091650] [<ffffffffa0218b5b>] smb2_sign_rqst+0x2b/0x40 [cifs]
<snip>
> The problem seems to be that crypto_shash_setkey() is called without
> calling smb3_crypto_shash_allocate() first. So I looked up how mainline
> avoids this issue, and it looks like the following commit makes a call
> to generate_signingkey() even when server->sign == false, and this path
> eventually calls smb3_crytpto_shash_allocate()), thus avoiding the NULL
> pointer dereference.
>
> cabfb3680f78 (CIFS: Enable encryption during session setup phase)
>
>
> So, I adopted this change, and now my resulting patch looks like this:
>
> diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
> index f2ff60e..19cc92c 100644
> --- a/fs/cifs/smb2pdu.c
> +++ b/fs/cifs/smb2pdu.c
> @@ -833,7 +833,7 @@ ssetup_exit:
>
> if (!rc) {
> mutex_lock(&server->srv_mutex);
> - if (server->sign && server->ops->generate_signingkey) {
> + if (server->ops->generate_signingkey) {
> rc = server->ops->generate_signingkey(ses);
> kfree(ses->auth_key.response);
> ses->auth_key.response = NULL;
> @@ -1559,6 +1559,9 @@ SMB2_ioctl(const unsigned int xid, struct cifs_tcon *tcon, u64 persistent_fid,
> } else
> iov[0].iov_len = get_rfc1002_length(req) + 4;
>
> + /* validate negotiate request must be signed - see MS-SMB2 3.2.5.5 */
> + if (opcode == FSCTL_VALIDATE_NEGOTIATE_INFO)
> + req->hdr.Flags |= SMB2_FLAGS_SIGNED;
>
> rc = SendReceive2(xid, ses, iov, num_iovecs, &resp_buftype, 0);
> rsp = (struct smb2_ioctl_rsp *)iov[0].iov_base;
>
>
>
> This fixes the NULL pointer dereference, but the mount still fails, but
> this time for a different reason -- due to STATUS_ACCESS_DENIED:
>
> Any thoughts on what is the right fix for stable kernels? Mounting SMB3
> shares works great on mainline (v4.15-rc5). It also works on 4.4.109 if
> I pass the sec=ntlmsspi option to the mount command (as opposed to the
> default: sec=ntlmssp). Please let me know if you need any other info.
>
> Thank you!
>
> Regards,
> Srivatsa
--
Thanks,
Steve
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