On Tue, Jan 4, 2011 at 2:09 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: > On Tue, 4 Jan 2011 13:51:41 -0600 > Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx> wrote: > >> On Tue, Jan 4, 2011 at 1:31 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: >> > On Tue, 4 Jan 2011 13:20:38 -0600 >> > Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx> wrote: >> > >> >> On Tue, Jan 4, 2011 at 1:11 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: >> >> > On Mon, 6 Dec 2010 14:56:46 -0600 >> >> > shirishpargaonkar@xxxxxxxxx wrote: >> >> > >> >> >> From: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx> >> >> >> >> >> >> >> >> >> If a DACL has entries for ACEs for SID Everyone and Authenticated Users, >> >> >> factor in mask in respective entries during calculation of permissions >> >> >> for all three, user, group, and other. >> >> >> >> >> >> http://technet.microsoft.com/en-us/library/bb463216.aspx >> >> >> >> >> >> >> >> >> Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx> >> >> >> --- >> >> >> fs/cifs/cifsacl.c | 13 +++++++++++-- >> >> >> 1 files changed, 11 insertions(+), 2 deletions(-) >> >> >> >> >> >> diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c >> >> >> index c6ebea0..a520091 100644 >> >> >> --- a/fs/cifs/cifsacl.c >> >> >> +++ b/fs/cifs/cifsacl.c >> >> >> @@ -43,9 +43,12 @@ static struct cifs_wksid wksidarr[NUM_WK_SIDS] = { >> >> >> ; >> >> >> >> >> >> >> >> >> -/* security id for everyone */ >> >> >> +/* security id for everyone/world system group */ >> >> >> static const struct cifs_sid sid_everyone = { >> >> >> 1, 1, {0, 0, 0, 0, 0, 1}, {0} }; >> >> >> +/* security id for Authenticated Users system group */ >> >> >> +static const struct cifs_sid sid_authusers = { >> >> >> + 1, 1, {0, 0, 0, 0, 0, 5}, {11} }; >> >> >> /* group users */ >> >> >> static const struct cifs_sid sid_user = {1, 2 , {0, 0, 0, 0, 0, 5}, {} }; >> >> >> >> >> >> @@ -367,7 +370,7 @@ static void parse_dacl(struct cifs_acl *pdacl, char *end_of_acl, >> >> >> if (num_aces > 0) { >> >> >> umode_t user_mask = S_IRWXU; >> >> >> umode_t group_mask = S_IRWXG; >> >> >> - umode_t other_mask = S_IRWXO; >> >> >> + umode_t other_mask = S_IRWXU | S_IRWXG | S_IRWXO; >> >> >> >> >> >> ppace = kmalloc(num_aces * sizeof(struct cifs_ace *), >> >> >> GFP_KERNEL); >> >> >> @@ -392,6 +395,12 @@ static void parse_dacl(struct cifs_acl *pdacl, char *end_of_acl, >> >> >> ppace[i]->type, >> >> >> &fattr->cf_mode, >> >> >> &other_mask); >> >> >> + if (compare_sids(&(ppace[i]->sid), &sid_authusers)) >> >> >> + access_flags_to_mode(ppace[i]->access_req, >> >> >> + ppace[i]->type, >> >> >> + &fattr->cf_mode, >> >> >> + &other_mask); >> >> >> + >> >> >> >> >> >> /* memcpy((void *)(&(cifscred->aces[i])), >> >> >> (void *)ppace[i], >> >> > >> >> > This looks like a harmless change... >> >> > >> >> > Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx> >> >> > >> >> >> >> Jeff, Thanks. >> >> >> >> > I have real doubts however about the owner/group parts of the cifsacl >> >> > scheme. It sets the user and group mode bits without setting the user >> >> > and group owners to meaningful values. So, those permissions have no >> >> > basis in reality. >> >> >> >> With the sid to uid and gid mapping code using winbind in the works, >> >> would that address these concerns? >> >> >> > >> > Yes, that would help some. >> > >> > That would give you the ability to present permissions that have some >> > basis in reality. You'll still have to figure out what to do when you >> > get a SID that can't be mapped for some reason. >> >> If we are using winbind, I do not see how this can happen. >> A SID perhaps could not be looked up but winbind, when asked, >> can/will always map a Owner SID to an uid and Group SID to a gid. >> > > Ahh ok. Good to know. Still, we need a meaningful owner to set it to > when the upcall fails. For instance, if the upcall isn't set up at > all... > I think at least two things can go against, either upcall is not setup at all so an upcall fails or we run out of idmap range as specified in smb.conf file for either uid or gid or both and so upcall fails. >> > >> > The real solution is to get rid of client-side permissions enforcement >> > altogether. The server is the only place that they can be reliably >> > enforced. >> >> I can see when changing mode or group or owner for an object, >> client should just be a conduit for that action (i.e. dispatch a >> fabricated DACL) and server is the one that should decide to enforce >> the change. > > Agreed. > >> But cifs client nonetheless needs to calculate and set mode and fill in >> uid and gid for an inode since none of these values (mode, uid, and gid) >> exist at the equivalent object on the server. >> > > Well, you need to have something to return in a stat() call. Those > values do not necessarily have to be used to enforce permissions. Note > the way that CIFS_MOUNT_NO_PERM is used. > >> I think we had this conversation before so I will dig it up, but I am >> trying to figure out how and where client enforces permissions >> (which it should not) other than when mode or user or group ids are >> being changed. >> > > See cifs_permission which eventually calls generic_permission, which > uses the i_mode/i_uid/i_gid to determine whether access is allowed. > > The problem though is that cifs mounts use a single set of credentials > by default. Unless we make multiuser mounts the default, we're sort of > stuck with this broken model for legacy reasons. > > -- > Jeff Layton <jlayton@xxxxxxxxxx> > -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
