On Fri, Oct 22, 2021 at 9:23 AM Pavel Shilovsky <piastryyy(a)gmail.com> wrote:
I do not get that warning on my system, but this patch should fix it?
Author: Ronnie Sahlberg <lsahlber(a)redhat.com>
Date: Fri Oct 22 09:41:24 2021 +1000
cifs.upcall.c: fix compiler warning
Signed-off-by: Ronnie Sahlberg <lsahlber(a)redhat.com>
diff --git a/cifs.upcall.c b/cifs.upcall.c
index e9c7f5f..5e7c0a1 100644
--- a/cifs.upcall.c
+++ b/cifs.upcall.c
@@ -69,6 +69,10 @@
#include <cap-ng.h>
#endif
+#ifndef discard_const
+#define discard_const(ptr) ((void *)((intptr_t)(ptr)))
+#endif
+
static krb5_context context;
static const char *prog = "cifs.upcall";
@@ -805,7 +809,7 @@ cifs_gss_get_req(const char *host, DATA_BLOB
*mechtoken, DATA_BLOB *sess_key)
GSS_C_NO_CREDENTIAL, /* claimant_cred_handle */
&ctx,
target_name,
- gss_mech_krb5, /* force krb5 */
+ discard_const(gss_mech_krb5), /* force krb5 */
0, /* flags */
0, /* time_req */
GSS_C_NO_CHANNEL_BINDINGS, /* input_chan_bindings */
mv -f .deps/cifs.upcall.Tpo .deps/cifs.upcall.Po
gcc -Wall -Wextra -D_FORTIFY_SOURCE=2 -fpie -pie -Wl,-z,relro,-z,now
-g -O2 -o cifs.upcall cifs.upcall.o data_blob.o asn1.o spnego.o
-ltalloc -lkeyutils -lgssapi_krb5 -lkrb5
--
Best regards,
Pavel Shilovsky
чт, 30 сент. 2021 г. в 16:18, Jacob Shivers <jshivers(a)redhat.com>:
>
> Hello Pavel/Michael,
>
> The only other addition would be to modify
> /etc/gssproxy/99-nfs-client.conf to also use the 'program' directive,
> i.e. 'program = /usr/sbin/rpc.gssd' so that both rpc.gssd and
> cifs.upcall can make use of the default gssproxy socket
> '/var/lib/gssproxy/default.sock'
>
> If the 'program' directive is not included in the respective drop
> files, then gssproxy can not differentiate which service is to be used
> and will fail to start.
>
> In total, a gssproxy drop file for cifs.upcall, modifying the gssproxy
> drop file for rpc.gssd, and an inclusion of a parameter that sets an
> environmental variable for cifs.upcall to use gssproxy should be all
> that is needed. I had not submitted a pull request for gssproxy yet as
> the extended cifs.upcall functionality had not received any further
> feedback. I can submit something if you are ready to include the patch
> to cifs.upcall
>
> Thanks,
>
> Jacob Shivers
>
> On Mon, Sep 27, 2021 at 3:20 AM Weiser, Michael <michael.weiser(a)atos.net>
wrote:
> >
> > Hello Pavel,
> >
> > > Do we have any more-up-to-date version of the cifs-utils patch other
> > > than the one attached to the email thread? I would like to merge the
> > > patch into the "next" branch so it makes the next release of
> > > cifs-utils.
> >
> > I'm also not aware of a newer version. As one of the initiators of the
discussion, who's highly interested in seeing this merged, I'm standing by
to help out with background context, testing or improving the code. (The
patch was meant as a PoC which is why I skipped some reindenting and
niceties to keep its approach and impact easy to gauge.)
> >
> > > Also there is a potential helper script mentioned above that is
needed
> > > to set up gssproxy properly?
> >
> > I'm not aware of a helper script. gssproxy just needs to be told about
cifs-utils and how it should be treated using a single config drop file.
Also in the meantime, Jacob and I have streamlined the configuration so a
separate UNIX domain socket and tweaking its permissions using a systemd
service drop-in file is no longer needed. Instead, gssproxy can distinguish
multiple clients on the same socket using the calling binary derived from
getsockopt/SO_PEERCRED.
> >
> > Finally, environment variable GSS_USE_PROXY needs to be set for
cifs.upcall to enable the gssproxy proxy mech. (Instead of using the env
command, cifs.upcall could have a command line option similar to
rpc.gssd[1] which ends up doing the same thing.)
> >
> > Here's the config summary:
> >
> > # cat /etc/request-key.d/cifs.spnego.conf
> > create cifs.spnego * * /usr/bin/env GSS_USE_PROXY=yes
/usr/sbin/cifs.upcall %k
> >
> > # cat /etc/gssproxy/99-cifs.conf
> > [service/cifs]
> > mechs = krb5
> > # not needed when program option is used
> > # socket = /var/lib/gssproxy/cifs.sock
> > program = /usr/sbin/cifs.upcall
> > cred_store = keytab:/etc/krb5.keytab
> > cred_store = ccache:FILE:/var/lib/gssproxy/clients/krb5cc_%U
> > cred_store = client_keytab:/var/lib/gssproxy/clients/%U.keytab
> > cred_usage = initiate
> > # allow process with any euid to use the service and receive
impersonated
> > # tickets for services
> > allow_any_uid = yes
> > # allow euid access to keytab
> > trusted = yes
> > # allow impersonation
> > impersonate = yes
> > # allow process with euid 0 to use the keytab
> > euid = 0
> >
> > The actual mount can be done using system credentials from the keytab.
Small proof session showcasing that gssproxy is involved and working:
> >
> > # systemctl stop gssproxy
> > # mount -o sec=krb5,multiuser,user=FEDORA33\$ //dc/share /mnt
> > # su - adsuser -c "touch /mnt/test"
> > touch: cannot touch '/mnt/test': Permission denied
> > # systemctl start gssproxy
> > # su - adsuser -c "touch /mnt/test"
> > #
> >
> > [1]
http://git.linux-nfs.org/?p=steved/nfs-utils.git;a=blob;f=utils/gssd/gssd...
> >
> > Thanks,
> > Michael
> >
> > ________________________________________
> > From: Pavel Shilovsky <piastryyy(a)gmail.com>
> > Sent: 24 September 2021 19:09:47
> > To: Jacob Shivers
> > Cc: Simo Sorce; Shyam Prasad N; Steve French; The GSS-Proxy developers
and users mailing list; linux-cifs(a)vger.kernel.org;
samba-technical(a)lists.samba.org
> > Subject: Re: [gssproxy] cifs-utils, Linux cifs kernel client and
gssproxy
> >
> > Caution! External email. Do not open attachments or click links,
unless this email comes from a known sender and you know the content is
safe.
> >
> > Catching up on the email thread. For some reason I missed it
originally somehow.
> >
> > Do we have any more-up-to-date version of the cifs-utils patch other
> > than the one attached to the email thread? I would like to merge the
> > patch into the "next" branch so it makes the next release of
> > cifs-utils.
> >
> > Also there is a potential helper script mentioned above that is needed
> > to set up gssproxy properly?
> >
> > --
> > Best regards,
> > Pavel Shilovsky
> >
> > вт, 23 февр. 2021 г. в 09:43, Jacob Shivers <jshivers(a)redhat.com>:
> > >
> > > I have tested the patches for cifs.upcall and can say that with some
> > > additional modifications to gssproxy the end setup brings a degree of
> > > feature parity to SMB clients that had been previously exclusive to
> > > NFS clients.
> > > Deployment does require some additional configuration, including the
> > > creation of a drop-in file for gssproxy under /etc/gssproxy and for
> > > the gssproxy service managed by systemd
> > >
> > >
> > > ### KDC configuration
> > >
> > > *** delegation ***
> > >
> > > Constrained Delegation (CD) for the SMB host to the Kerberized SMB
server
> > > Resource Based Constrained Delegation (RBCD) on the Kerberized SMB
> > > server to determine which SMB clients can delegate
> > >
> > >
> > > ### SMB client configuration
> > >
> > > *** sssd ***
> > >
> > > Configuration file modification.
> > >
> > > Disable using fully qualified domain names as impersonation does not
> > > correctly handle fully qualified names at time of ticket acquisition.
> > >
> > > use_fully_qualified_names = False
> > >
> > > *** gssproxy ***
> > >
> > > Drop file creation
> > >
> > > Add a drop file for gssproxy to create the necessary socket and
> > > corresponding settings.
> > >
> > > # cat /etc/gssproxy/99-cifs-client.conf with contents
> > > [service/cifs]
> > > mechs = krb5
> > > socket = /var/lib/gssproxy/cifs.sock
> > > cred_store = keytab:/etc/krb5.keytab
> > > cred_usage = initiate
> > > euid = 0
> > > impersonate = yes
> > > allow_any_uid = yes
> > >
> > > Service drop-in file.
> > >
> > > Create a drop-in file to limit socket access for an unattended user,
if desired.
> > >
> > > # cat /etc/systemd/system/gssproxy.service.d/90-cifs.conf
> > > [Service]
> > > # Limit cifs.sock socket file accessiblility to just the unattended
user.
> > > ExecStartPost=/bin/bash -c 'chmod 660 /var/lib/gssproxy/cifs.sock
&&
> > > setfacl -m u:chang:rw /var/lib/gssproxy/cifs.sock'
> > >
> > >
> > > *** cifs.upcall ***
> > >
> > > cifs.spnego.conf modification
> > >
> > > Allow for gssprxy to be used and specify socket file
> > >
> > > # cat /etc/request-key.d/cifs.spnego.conf
> > > create cifs.spnego * * /usr/bin/env GSS_USE_PROXY=yes
> > > GSSPROXY_SOCKET=/var/lib/gssproxy/cifs.sock /usr/sbin/cifs.upcall %k
> > >
> > > include the '-t' flag to allow for accessing a Kerberized DFS
> > > namespace using a domain based mount, i.e //example.net/dfs/share
> > >
> > > create cifs.spnego * * /usr/bin/env GSS_USE_PROXY=yes
> > > GSSPROXY_SOCKET=/var/lib/gssproxy/cifs.sock /usr/sbin/cifs.upcall -t
> > > %k
> > >
> > >
> > > The above does allow for unattended users to access a Kerberized SMB
> > > share while limiting access to only a specific user:
> > >
> > > # mount //win2k16-dfs1.example.net/greendale/ /mnt -o
> > > sec=krb5,username='TEST-BOX$(a)EXAMPLE.NET',multiuser
> > >
> > > # su - jeff
> > > Last login: Fri Feb 5 12:14:42 EST 2021 on pts/0
> > > [jeff@test-box ~]$ ll /mnt
> > > ls: cannot access '/mnt': Permission denied
> > > [jeff@test-box ~]$ logout
> > >
> > > # su - chang
> > > Last login: Fri Feb 5 12:14:46 EST 2021 on pts/0
> > > [chang@test-box ~]$ klist
> > > klist: No credentials cache found (filename: /tmp/krb5cc_602001123)
> > > [chang@test-box ~]$ ls -l /mnt
> > > total 143
> > >
> > > drwxr-xr-x. 2 chang domain users 0 Oct 4 2018 DfsrPrivate
> > > -rwxr-xr-x. 1 chang domain users 0 Sep 22 10:07 test_file
> > > -rwxr-xr-x. 1 chang domain users 0 Dec 14 15:22 whoami
> > > drwxr-xr-x. 2 chang domain users 0 Dec 7 12:54 winhome
> > >
> > > [chang@test-box ~]$ klist
> > > klist: No credentials cache found (filename: /tmp/krb5cc_602001123)
> > >
> > >
> > > Feb 23 12:22:44.857956
test-box.example.net su[1672]: (to jeff)
root on pts/1
> > > Feb 23 12:22:44.866263
test-box.example.net su[1672]:
> > > pam_systemd(su-l:session): Cannot create session: Already running in
a
> > > session or user slice
> > > Feb 23 12:22:44.867158
test-box.example.net su[1672]:
> > > pam_unix(su-l:session): session opened for user jeff by root(uid=0)
> > > Feb 23 12:22:46.253310
test-box.example.net cifs.upcall[1700]: key
> > > description: cifs.spnego;0;0;39010000;ver=0x2;host=
win2k16-dfs1.example.net
;ip4=192.168.124.132;sec=krb5;uid=0x23e1cedc;creduid=0x23e1cedc;pid=0x6a3
> > > Feb 23 12:22:46.253335
test-box.example.net cifs.upcall[1700]: ver=2
> > > Feb 23 12:22:46.253338
test-box.example.net cifs.upcall[1700]:
> > >
host=win2k16-dfs1.example.net
> > > Feb 23 12:22:46.253342
test-box.example.net cifs.upcall[1700]:
> > > ip=192.168.124.132
> > > Feb 23 12:22:46.253344
test-box.example.net cifs.upcall[1700]: sec=1
> > > Feb 23 12:22:46.253348
test-box.example.net cifs.upcall[1700]:
uid=602001116
> > > Feb 23 12:22:46.253352
test-box.example.net cifs.upcall[1700]:
creduid=602001116
> > > Feb 23 12:22:46.253365
test-box.example.net cifs.upcall[1700]:
pid=1699
> > > Feb 23 12:22:46.253978
test-box.example.net cifs.upcall[1700]:
> > > get_cachename_from_process_env: pathname=/proc/1699/environ
> > > Feb 23 12:22:46.254995
test-box.example.net cifs.upcall[1700]:
> > > get_existing_cc: default ccache is FILE:/tmp/krb5cc_602001116
> > > Feb 23 12:22:46.255015
test-box.example.net cifs.upcall[1700]:
> > > get_tgt_time: unable to get principal
> > > Feb 23 12:22:46.255021
test-box.example.net cifs.upcall[1700]:
> > > handle_krb5_mech: getting service ticket for
win2k16-dfs1.example.net
> > > Feb 23 12:22:46.255024
test-box.example.net cifs.upcall[1700]:
> > > handle_krb5_mech: using GSS-API
> > > Feb 23 12:22:46.259295
test-box.example.net cifs.upcall[1700]:
GSS-API
> > > error init_sec_context: Unspecified GSS failure. Minor code may
> > > provide more information
> > > Feb 23 12:22:46.259306
test-box.example.net cifs.upcall[1700]:
GSS-API
> > > error init_sec_context: No Kerberos credentials available (default
> > > cache: FILE:/tmp/krb5cc_602001116)
> > > Feb 23 12:22:46.259311
test-box.example.net cifs.upcall[1700]:
> > > handle_krb5_mech: failed to obtain service ticket via GSS (851968)
> > > Feb 23 12:22:46.259314
test-box.example.net cifs.upcall[1700]:
Unable
> > > to obtain service ticket
> > > Feb 23 12:22:46.259323
test-box.example.net cifs.upcall[1700]: Exit
> > > status 851968
> > > Feb 23 12:22:46.262827
test-box.example.net kernel: CIFS VFS:
> > > \\win2k16-dfs1.example.net Send error in SessSetup = -126
> > > Feb 23 12:22:47.398266
test-box.example.net su[1672]:
> > > pam_unix(su-l:session): session closed for user jeff
> > > Feb 23 12:22:49.159640
test-box.example.net su[1702]: (to chang)
root on pts/1
> > > Feb 23 12:22:49.173264
test-box.example.net su[1702]:
> > > pam_systemd(su-l:session): Cannot create session: Already running in
a
> > > session or user slice
> > > Feb 23 12:22:49.173967
test-box.example.net su[1702]:
> > > pam_unix(su-l:session): session opened for user chang by root(uid=0)
> > > Feb 23 12:22:51.878743
test-box.example.net cifs.upcall[1729]: key
> > > description: cifs.spnego;0;0;39010000;ver=0x2;host=
win2k16-dfs1.example.net
;ip4=192.168.124.132;sec=krb5;uid=0x23e1cee3;creduid=0x23e1cee3;pid=0x6c0
> > > Feb 23 12:22:51.878765
test-box.example.net cifs.upcall[1729]: ver=2
> > > Feb 23 12:22:51.878769
test-box.example.net cifs.upcall[1729]:
> > >
host=win2k16-dfs1.example.net
> > > Feb 23 12:22:51.878773
test-box.example.net cifs.upcall[1729]:
> > > ip=192.168.124.132
> > > Feb 23 12:22:51.878776
test-box.example.net cifs.upcall[1729]: sec=1
> > > Feb 23 12:22:51.878780
test-box.example.net cifs.upcall[1729]:
uid=602001123
> > > Feb 23 12:22:51.878783
test-box.example.net cifs.upcall[1729]:
creduid=602001123
> > > Feb 23 12:22:51.878786
test-box.example.net cifs.upcall[1729]:
pid=1728
> > > Feb 23 12:22:51.879060
test-box.example.net cifs.upcall[1729]:
> > > get_cachename_from_process_env: pathname=/proc/1728/environ
> > > Feb 23 12:22:51.879799
test-box.example.net cifs.upcall[1729]:
> > > get_existing_cc: default ccache is FILE:/tmp/krb5cc_602001123
> > > Feb 23 12:22:51.879819
test-box.example.net cifs.upcall[1729]:
> > > get_tgt_time: unable to get principal
> > > Feb 23 12:22:51.879824
test-box.example.net cifs.upcall[1729]:
> > > handle_krb5_mech: getting service ticket for
win2k16-dfs1.example.net
> > > Feb 23 12:22:51.879827
test-box.example.net cifs.upcall[1729]:
> > > handle_krb5_mech: using GSS-API
> > > Feb 23 12:22:51.886573
test-box.example.net gssproxy[1000]:
> > > [2021/02/23 17:22:51]: Client [2021/02/23 17:22:51]:
> > > (/usr/sbin/cifs.upcall) [2021/02/23 17:22:51]: connected (fd =
> > > 14)[2021/02/23 17:22:51]: (pid = 1729) (uid = 602001123) (gid =
> > > 602000513)[2021/02/23 17:22:51]: (context =
> > > system_u:system_r:kernel_t:s0)[>
> > > Feb 23 12:22:51.886573
test-box.example.net gssproxy[1000]: [CID
> > > 14][2021/02/23 17:22:51]: Connection matched service cifs
> > > Feb 23 12:22:51.886573
test-box.example.net gssproxy[1000]: [CID
> > > 14][2021/02/23 17:22:51]: gp_rpc_execute: executing 6
> > > (GSSX_ACQUIRE_CRED) for service "cifs", euid: 602001123,socket:
> > > /var/lib/gssproxy/cifs.sock
> > > Feb 23 12:22:51.886573
test-box.example.net gssproxy[1000]:
> > > GSSX_ARG_ACQUIRE_CRED( call_ctx: { "" [ ] } input_cred_handle:
<Null>
> > > add_cred: 0 desired_name: <Null> time_req: 0 desired_mechs: { }
> > > cred_usage: INITIATE initiator_time_req: 0 acceptor_time_req: 0 )
> > > Feb 23 12:22:52.346639
test-box.example.net gssproxy[1000]:
> > > GSSX_RES_ACQUIRE_CRED( status: { 0 { 1 2 840 113554 1 2 2 } 0 ""
"" [
> > > ] } output_cred_handle: { "chang(a)EXAMPLE.NET" [ {
"chang(a)EXAMPLE.NET
"
> > > { 1 2 840 113554 1 2 2 } INITIATE 36000 0 } ] [ K.....T.....pJv.... ]
> > > 0 } )
> > > Feb 23 12:22:52.348086
test-box.example.net gssproxy[1000]: [CID
> > > 14][2021/02/23 17:22:52]: Connection matched service cifs
> > > Feb 23 12:22:52.348086
test-box.example.net gssproxy[1000]: [CID
> > > 14][2021/02/23 17:22:52]: gp_rpc_execute: executing 8
> > > (GSSX_INIT_SEC_CONTEXT) for service "cifs", euid:
602001123,socket:
> > > /var/lib/gssproxy/cifs.sock
> > > Feb 23 12:22:52.348086
test-box.example.net gssproxy[1000]:
> > > GSSX_ARG_INIT_SEC_CONTEXT( call_ctx: { "" [ ] }
context_handle:
> > > <Null> cred_handle: { "chang(a)EXAMPLE.NET" [ {
"chang(a)EXAMPLE.NET" {
1
> > > 2 840 113554 1 2 2 } INITIATE 36000 0 } ] [ K.....T.....pJv.... ] 0 }
> > > target_name: "cifs(a)win2k16-dfs1.example.net" mech>
> > > Feb 23 12:22:52.348086
test-box.example.net gssproxy[1000]: [CID
> > > 14][2021/02/23 17:22:52]: Credentials allowed by configuration
> > > Feb 23 12:22:52.357103
test-box.example.net gssproxy[1000]:
> > > GSSX_RES_INIT_SEC_CONTEXT( status: { 0 { 1 2 840 113554 1 2 2 } 0
""
> > > "" [ ] } context_handle: { [ ......H............ ] [ ] 0 { 1 2
840
> > > 113554 1 2 2 } "chang(a)EXAMPLE.NET"
> > > "cifs/win2k16-dfs1.example.net(a)EXAMPLE.NET" 36000 432 1 1 }
> > > output_token: [ .....>
> > > Feb 23 12:22:52.357419
test-box.example.net cifs.upcall[1729]: Exit
status 0
> > >
> > >
> > > Ultimately a helper-script packaged with cifs-utils or a separate
> > > package entirely could be responsible for adding the file under
> > > /etc/gssproxy and the drop-in file for systemd. The helper script
> > > could take a series of users/groups as arguments that would limit
> > > access to the socket file or there could be a separate config file
> > > that is read from to determine if access to the cifs.sock socket
> > > should be limited.
> > >
> > >
> > > On Fri, Feb 19, 2021 at 12:38 PM Simo Sorce <simo(a)redhat.com>
wrote:
> > > >
> > > > On Fri, 2021-02-19 at 03:30 -0800, Shyam Prasad N wrote:
> > > > > Hi Simo,
> > > > >
> > > > > > Finally the GSS-Proxy mechanism is namespace compatible,
so
you also
> > > > > > get the ability to define different auth daemons per
different
> > > > > > containers, no need to invent new mechanisms for that or
change yet
> > > > > > again protocols/userspace to obtain container
capabilities.
> > > > >
> > > > > Could you please point me to the documentation for doing this?
> > > >
> > > > I do not know if the kernel documents this, but the way gssproxy
works
> > > > is that when you start the daemon it pokes at the kernel to let it
know
> > > > the socket is available. So then the kernel opens the socket in the
> > > > namespace the proxy is running into (detected from the poking
> > > > operation, which is a write in a proc file).
> > > >
> > > > HTH,
> > > > Simo.
> > > >
> > > > >
> > > > > Regards,
> > > > > Shyam
> > > > >
> > > > > On Thu, Dec 17, 2020 at 5:41 AM Simo Sorce
<simo(a)redhat.com>
wrote:
> > > > > > Hi Steve,
> > > > > >
> > > > > > GSSAPI and krb5 as implemented in system krb5 libraries
exists
from
> > > > > > longer than Samba has implemented those capabilities, I do
not
think it
> > > > > > make sense to reason along those lines.
> > > > > >
> > > > > > GSS-Proxy has been built with a protocol to talk from the
kernel that
> > > > > > resolved a number of issues for knfsd (eg big packet sizes
when a MS-
> > > > > > PAC is present).
> > > > > >
> > > > > > And Samba uses internally exactly the same krb5 mechanism
as
it defers
> > > > > > to the kerberos libraries as well.
> > > > > >
> > > > > > Additionally GSS-Proxy can be very easily extended to also
do
NTLMSSP
> > > > > > using the same interface as I have built the gssntlmssp
long
ago from
> > > > > > the MS spec, and is probably the most correct NTLMSSP
implementation
> > > > > > you can find around.
> > > > > >
> > > > > > Gssntlmssp also has a Winbind backend so you get
automaticaly
access to
> > > > > > whatever cached credentials Winbindd has for users as a
bonus
(although
> > > > > > the integration can be improved there), yet you *can* use
it
w/o
> > > > > > Winbindd just fine providing a credential file (smbpasswd
format
> > > > > > compatible).
> > > > > >
> > > > > > GSS-Proxy is already integrated in distributions because it
is
used by
> > > > > > knfsd, and can be as easily used by cifsd, and you
*should*
really use
> > > > > > it there, so we can have a single, consistent, maintained,
mechanism
> > > > > > for server side GSS authentication, and not have to repeat
and
reinvent
> > > > > > kernel to userspace mechanisms.
> > > > > >
> > > > > > And if you add it for cifsd you have yet another reason to
do
it for
> > > > > > cifs.ko as well.
> > > > > >
> > > > > > Finally the GSS-Proxy mechanism is namespace compatible,
so
you also
> > > > > > get the ability to define different auth daemons per
different
> > > > > > containers, no need to invent new mechanisms for that or
change yet
> > > > > > again protocols/userspace to obtain container
capabilities.
> > > > > >
> > > > > > For the client we'll need to add some XDR parsing
functions in
kernel,
> > > > > > they were omitted from my original patches because there
was
no client
> > > > > > side kernel consumer back then, but it i an easy,
mechanical
change.
> > > > > >
> > > > > > HTH,
> > > > > > Simo.
> > > > > >
> > > > > > On Wed, 2020-12-16 at 16:43 -0600, Steve French wrote:
> > > > > > > generally I would feel more comfortable using
something
(library or
> > > > > > > utility) in Samba (if needed) for additional SPNEGO
support
if
> > > > > > > something is missing (in what the kernel drivers are
doing to
> > > > > > > encapsulate Active Directory or Samba AD krb5 tickets
in
SPNEGO) as
> > > > > > > Samba is better maintained/tested etc. than most
components. Is there
> > > > > > > something in Samba that could be used here instead of
having
a
> > > > > > > dependency on another project - Samba has been doing
Kerberos/SPNEGO
> > > > > > > longer than most ...? There are probably others
(jra,
Metze etc.)
> > > > > > > that have would know more about gssproxy vs. Samba
equivalents though
> > > > > > > and would defer to them ...
> > > > > > >
> > > > > > > On Wed, Dec 16, 2020 at 8:33 AM Simo Sorce
<simo(a)redhat.com>
wrote:
> > > > > > > > Hi Michael,
> > > > > > > > as you say the best course of action would be for
cifs.ko
to move to
> > > > > > > > use the RPC interface we defined for knfsd (with
any
extensions that
> > > > > > > > may be needed), and we had discussions in the
past with
cifs upstream
> > > > > > > > developers about it. But nothing really
materialized.
> > > > > > > >
> > > > > > > > If something is needed in the short term, I
thjink the
quickest course
> > > > > > > > of action is indeed to change the userspace
helper to use
gssapi
> > > > > > > > function calls, so that they can be intercepted
like we do
for rpc.gssd
> > > > > > > > (nfs client's userspace helper).
> > > > > > > >
> > > > > > > > Unfortunately I do not have the cycles to work on
that
myself at this
> > > > > > > > time :-(
> > > > > > > >
> > > > > > > > HTH,
> > > > > > > > Simo.
> > > > > > > >
> > > > > > > > On Wed, 2020-12-16 at 10:01 +0000, Weiser,
Michael wrote:
> > > > > > > > > Hello,
> > > > > > > > >
> > > > > > > > > I have a use-case for authentication of
Linux cifs
client mounts without the user being present (e.g. from batch jobs) using
gssproxy's impersonation feature with Kerberos Constrained Delegation
similar to how it can be done for NFS[1].
> > > > > > > > >
> > > > > > > > > My understanding is that currently neither
the Linux
cifs kernel client nor cifs-utils userland tools support acquiring
credentials using gssproxy. The former uses a custom upcall interface to
talk to cifs.spnego from cifs-utils. The latter then goes looking for
Kerberos ticket caches using libkrb5 functions, not GSSAPI, which prevents
gssproxy from interacting with it.[2]
> > > > > > > > >
> > > > > > > > > From what I understand, the preferred method
would be to
switch the Linux kernel client upcall to the RPC protocol defined by
gssproxy[3] (as has been done for the Linux kernel NFS server already
replacing rpc.svcgssd[4]). The kernel could then, at least optionally, talk
to gssproxy directly to try and obtain credentials.
> > > > > > > > >
> > > > > > > > > Failing that, cifs-utils' cifs.spnego
could be switched
to GSSAPI so that gssproxy's interposer plugin could intercept GSSAPI calls
and provide them with the required credentials (similar to the NFS client
rpc.gssd[5]).
> > > > > > > > >
> > > > > > > > > Assuming my understanding is correct so
far:
> > > > > > > > >
> > > > > > > > > Is anyone doing any work on this and could
use some help
(testing, coding)?
> > > > > > > > > What would be expected complexity and
possible
roadblocks when trying to make a start at implementing this?
> > > > > > > > > Or is the idea moot due to some constraint
or recent
development I'm not aware of?
> > > > > > > > >
> > > > > > > > > I have found a recent discussion of the
topic on
linux-cifs[6] which provided no definite answer though.
> > > > > > > > >
> > > > > > > > > As a crude attempt at an explicit userspace
workaround I
tried but failed to trick smbclient into initialising a ticket cache using
gssproxy for cifs.spnego to find later on.
> > > > > > > > > Is this something that could be implemented
without too
much redundant effort (or should already work, perhaps using a different
tool)?
> > > > > > > > >
> > > > > > > > > [1]
https://github.com/gssapi/gssproxy/blob/main/docs/NFS.md#user-impersonati...
> > > > > > > > > [2]
https://pagure.io/gssproxy/issue/56
> > > > > > > > > [3]
https://github.com/gssapi/gssproxy/blob/main/docs/ProtocolDocumentation.md
> > > > > > > > > [4]
https://github.com/gssapi/gssproxy/blob/main/docs/NFS.md#nfs-server
> > > > > > > > > [5]
https://github.com/gssapi/gssproxy/blob/main/docs/NFS.md#nfs-client
> > > > > > > > > [6]
https://www.spinics.net/lists/linux-cifs/msg20182.html
> > > > > > > > > --
> > > > > > > > > Thanks,
> > > > > > > > > Michael
> > > > > > > > >
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> > > > > > > >
> > > > > > > > --
> > > > > > > > Simo Sorce
> > > > > > > > RHEL Crypto Team
> > > > > > > > Red Hat, Inc
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > >
> > > > > > --
> > > > > > Simo Sorce
> > > > > > RHEL Crypto Team
> > > > > > Red Hat, Inc
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > >
> > > > --
> > > > Simo Sorce
> > > > RHEL Crypto Team
> > > > Red Hat, Inc
> > > >
> > > >
> > > >
> > > >
> > >
> >
>