2018-03-14 23:39 GMT-07:00 Srivatsa S. Bhat <srivatsa@xxxxxxxxxxxxx>:
> On 3/13/18 11:51 PM, Steve French wrote:
>> 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.
>
> Thank you!
>
>> 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.
>>
>
> Agreed... And unfortunately mainline has diverged so much from stable
> around this code (with lots of code re-organization etc) that it seems
> rather hard to isolate the rest of the fix for this issue.
>
>> Aurelien/Pavel,
>> Ideas?
>>
>
>
> Regards,
> Srivatsa
>
>>
>> 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;
>>>
Hi Steve, Srivatsa,
Have you tried to amend the rest of the patch (CIFS: Enable encryption
during session setup phase) ?
https://git.samba.org/?p=sfrench/cifs-2.6.git;a=commitdiff;h=cabfb3680f78981d26c078a26e5c748531257ebb
The remaining portion has the important piece:
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -344,13 +344,12 @@ void build_ntlmssp_negotiate_blob(unsigned char *pbuffer,
/* BB is NTLMV2 session security format easier to use here? */
flags = NTLMSSP_NEGOTIATE_56 | NTLMSSP_REQUEST_TARGET |
NTLMSSP_NEGOTIATE_128 | NTLMSSP_NEGOTIATE_UNICODE |
- NTLMSSP_NEGOTIATE_NTLM | NTLMSSP_NEGOTIATE_EXTENDED_SEC;
- if (ses->server->sign) {
+ NTLMSSP_NEGOTIATE_NTLM | NTLMSSP_NEGOTIATE_EXTENDED_SEC |
+ NTLMSSP_NEGOTIATE_SEAL;
^^^
we are adding NTLMSSP_NEGOTIATE_SEAL and...
+ if (ses->server->sign)
flags |= NTLMSSP_NEGOTIATE_SIGN;
- if (!ses->server->session_estab ||
- ses->ntlmssp->sesskey_per_smbsess)
- flags |= NTLMSSP_NEGOTIATE_KEY_XCH;
- }
+ if (!ses->server->session_estab || ses->ntlmssp->sesskey_per_smbsess)
+ flags |= NTLMSSP_NEGOTIATE_KEY_XCH;
NTLMSSP_NEGOTIATE_KEY_XCH to instruct the server to exchange keys
sec_blob->NegotiateFlags = cpu_to_le32(flags);
@@ -407,13 +406,12 @@ int build_ntlmssp_auth_blob(unsigned char **pbuffer,
flags = NTLMSSP_NEGOTIATE_56 |
NTLMSSP_REQUEST_TARGET | NTLMSSP_NEGOTIATE_TARGET_INFO |
NTLMSSP_NEGOTIATE_128 | NTLMSSP_NEGOTIATE_UNICODE |
- NTLMSSP_NEGOTIATE_NTLM | NTLMSSP_NEGOTIATE_EXTENDED_SEC;
- if (ses->server->sign) {
+ NTLMSSP_NEGOTIATE_NTLM | NTLMSSP_NEGOTIATE_EXTENDED_SEC |
+ NTLMSSP_NEGOTIATE_SEAL;
^^^
the same as above.
+ if (ses->server->sign)
flags |= NTLMSSP_NEGOTIATE_SIGN;
- if (!ses->server->session_estab ||
- ses->ntlmssp->sesskey_per_smbsess)
- flags |= NTLMSSP_NEGOTIATE_KEY_XCH;
- }
+ if (!ses->server->session_estab || ses->ntlmssp->sesskey_per_smbsess)
+ flags |= NTLMSSP_NEGOTIATE_KEY_XCH;
the same.
tmp = *pbuffer + sizeof(AUTHENTICATE_MESSAGE);
sec_blob->NegotiateFlags = cpu_to_le32(flags);
According to the MS-NLMP
(https://msdn.microsoft.com/en-us/library/cc236692.aspx), the server
will generate the exchange the key in presence of any flag from two:
NTLMSSP_NEGOTIATE_SEAL or NTLMSSP_NEGOTIATE_SIGN.
Basically, the proper fix would be to add NTLMSSP_NEGOTIATE_SIGN flag
unconditionally if we allow signed requests on mounts without signing
enabled by the client.
--
Best regards,
Pavel Shilovsky
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