Hi again,
On Mon, 29 Jul 2013 14:50:03 +0200 Marcus Moeller <marcus.moeller@xxxxxx> wrote:[ 124.607810] fs/cifs/cifssmb.c: negprot rc 0 [ 124.607814] fs/cifs/connect.c: Security Mode: 0xf Capabilities: 0x8001f3fc TimeAdjust: -7200 [ 124.607817] fs/cifs/sess.c: sess setup type 4 [ 124.607826] fs/cifs/cifs_spnego.c: key description = ver=0x2;host=d.ethz.ch;ip4=82.130.70.6;sec=krb5;uid=0xaf05;creduid=0xaf05;user=mam4tst;pid=0x61a [ 124.803185] fs/cifs/sess.c: ssetup freeing small buf ffff88022c31a000 [ 124.803195] CIFS VFS: Send error in SessSetup = -126 [ 124.803203] fs/cifs/connect.c: CIFS VFS: leaving cifs_get_smb_ses (xid = 5) rc = -126 [ 124.803212] fs/cifs/fscache.c: cifs_fscache_release_client_cookie: (0xffff88022a1b6000/0xffff88022a6430f0) [ 124.803368] fs/cifs/connect.c: CIFS VFS: leaving cifs_mount (xid = 4) rc = -126 [ 124.803374] CIFS VFS: cifs_mount failed w/return code = -126The only failure I see is the one above, and that's because it failed to upcall for the correct key. Are you sure you have krb5 creds as that user?Yes, creds are there and it also works when mounting from one of the servers directly. Only mounting using the domainname does not work.[ 131.324798] fs/cifs/cifssmb.c: negprot rc 0 [ 131.324804] fs/cifs/connect.c: Security Mode: 0xf Capabilities: 0x8001f3fc TimeAdjust: -7200 [ 131.324808] fs/cifs/sess.c: sess setup type 4 [ 131.324821] fs/cifs/cifs_spnego.c: key description = ver=0x2;host=d.ethz.ch;ip4=172.31.65.62;sec=krb5;uid=0xaf05;creduid=0xaf05;user=mam4tst;pid=0x62c[ 131.384335] fs/cifs/transport.c: For smb_command 115 [ 131.384344] fs/cifs/transport.c: Sending smb: smb_len=1666 [ 131.387043] fs/cifs/connect.c: RFC1002 header 0xf9 [ 131.387055] fs/cifs/misc.c: checkSMB Length: 0xfd, smb_buf_length: 0xf9 [ 131.387095] fs/cifs/transport.c: cifs_sync_mid_result: cmd=115 mid=2 state=4 [ 131.387100] fs/cifs/misc.c: Null buffer passed to cifs_small_buf_releaseHere' the upcall for a similar set of creds worked fine. The only thing that seems to have changed in the key description is the IP address. Do you have cifs.upcall set up to use the --trust-dns flag? If so, why?A relict from the past. I have removed it from the config. Thanks for pointing out.Sorry, I was wrong. Without the -t option I am not even able to mount it at all. The man page states a few words on that parameter, but I am still not sure how it works when -t is not set. With -t set, the initial problem with the domain lookup works, when reverse DNS is configured propably.Ok, that makes sense then. The problem here is that the kernel needs to know what service principal name to use when contacting the server, and I suspect your krb5 configuration is not quite right. It looks like you're doing something like: mount //d.ethz.ch/dfs /mnt/dfs -o sec=krb5... ...at this point, what happens is that the kernel needs to get a krb5 service ticket to talk to the CIFS service on the host. What it typically does is take the hostname in the UNC that you're trying to mount, prepend it with "cifs/" and then try to get a service ticket for that. In your case, it'll look something like this: cifs/d.ethz.ch@xxxxxxxxxxxxxxxxxxxxxx ...now, typically if that fails, we'll give up. Trying to do anything else is not considered safe since it's vulernable to DNS spoofing. If however, you add the '-t' flag to cifs.upcall, that tells it to try and guess the hostname part of that principal by reverse resolving it in DNS. It takes the IP address to which you are connecting, does a reverse DNS lookup and then uses that in the SPN. This is less safe, since if your DNS server is compromised someone could redirect you to a malicious server, and your client wouldn't be able to trivially detect that. So it in effect waters down krb5 security. The correct fix is to ensure that the server(s) to which you are connecting have the ability to accept SPNs for the "hostnames" to which you want to connect. That means that you need to add SPNs for cifs/d.ethz.ch and ensure that the server will accept them to talk to its cifs service. Alternately, you can continue to use the '-t' flag and ensure that each possible server accepts principals for the hostnames to which their IP addresses reverse-resolve, with the caveat that its less safe than doing that the "right way". As to how to add these principals and make the server accept them...it depends on the server. Clear as mud?Hehe, thanks for pointing that out. One thing I am not yet aware of is where the SPN cifs/d.ethz.ch has to be set? On the DFS Servers and/or on the servers which hold the shares? The latter ones are EMC and the DFS Servers are 2008R2. Greets MarcusDefinitely on the first DFS server. On the others, they'll need to accept SPNs holding the hostnames that are in the DFS referrals. So if your DFS server gives you a referral that's something like this: bar -> //foo.d.ethz.ch/bar ...then you'll need to ensure that foo.d.ethz.ch accepts SPNs that have that hostname in them.
I have found some time to talk to our Active Directory Admins. They mentioned that every DC in our setup is a DFS server and there is nothing like a 'first DFS'. So is it possible to set the same SPN on all of these servers?
Greets Marcus
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