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... > >> > >> > 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 permission checking has to be done by the client. What cifs/smb command can a client send to the server to verify permissions? >> 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
