Return-Path: linux-nfs-owner@vger.kernel.org Received: from nm15-vm0.access.bullet.mail.sp2.yahoo.com ([98.139.44.164]:45535 "EHLO nm15-vm0.access.bullet.mail.sp2.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754908Ab3C2PZG (ORCPT ); Fri, 29 Mar 2013 11:25:06 -0400 Message-ID: <5155B0E3.9040108@schaufler-ca.com> Date: Fri, 29 Mar 2013 08:18:59 -0700 From: Casey Schaufler MIME-Version: 1.0 To: David Quigley CC: "J. Bruce Fields" , Steve Dickson , Trond Myklebust , "J. Bruce Fields" , "David P. Quigley" , Linux NFS list , Linux Security List , SELinux List , Casey Schaufler Subject: Re: [PATCH 13/14] NFSD: Server implementation of MAC Labeling References: <1364478845-29796-1-git-send-email-SteveD@redhat.com> <1364478845-29796-14-git-send-email-SteveD@redhat.com> <20130328161444.GF7080@fieldses.org> <51550C03.1000107@davequigley.com> <20130329144050.GB22307@fieldses.org> <001ff69afd411b0318d7122bf07bd218@countercultured.net> In-Reply-To: <001ff69afd411b0318d7122bf07bd218@countercultured.net> Content-Type: text/plain; charset=UTF-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: On 3/29/2013 7:49 AM, David Quigley wrote: > On 03/29/2013 10:40, J. Bruce Fields wrote: >> On Thu, Mar 28, 2013 at 11:35:31PM -0400, Dave Quigley wrote: >>> On 3/28/2013 12:14 PM, J. Bruce Fields wrote: >>> >On Thu, Mar 28, 2013 at 09:54:04AM -0400, Steve Dickson wrote: >>> >>From: David Quigley >>> >> >>> >>This patch adds the ability to encode and decode file labels on >>> the server for >>> >>the purpose of sending them to the client and also to process >>> label change >>> >>requests from the client. >>> >> >>> >>Signed-off-by: Matthew N. Dodd >>> >>Signed-off-by: Miguel Rodel Felipe >>> >>Signed-off-by: Phua Eu Gene >>> >>Signed-off-by: Khin Mi Mi Aung >>> >>--- >>> >> fs/nfsd/nfs4proc.c | 41 +++++++++++++++++++ >>> >> fs/nfsd/nfs4xdr.c | 116 >>> ++++++++++++++++++++++++++++++++++++++++++++++++++--- >>> >> fs/nfsd/nfsd.h | 6 ++- >>> >> fs/nfsd/vfs.c | 29 ++++++++++++++ >>> >> fs/nfsd/vfs.h | 2 + >>> >> fs/nfsd/xdr4.h | 3 ++ >>> >> 6 files changed, 191 insertions(+), 6 deletions(-) >>> >> >>> >>diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c >>> >>index ae73175..bb17589 100644 >>> >>--- a/fs/nfsd/nfs4proc.c >>> >>+++ b/fs/nfsd/nfs4proc.c >>> >>@@ -42,6 +42,36 @@ >>> >> #include "current_stateid.h" >>> >> #include "netns.h" >>> >> >>> >>+#ifdef CONFIG_NFSD_V4_SECURITY_LABEL >>> >>+#include >>> >>+ >>> >>+static inline void >>> >>+nfsd4_security_inode_setsecctx(struct svc_fh *resfh, struct >>> nfs4_label *label, u32 *bmval) >>> >>+{ >>> >>+ struct inode *inode = resfh->fh_dentry->d_inode; >>> >>+ int status; >>> >>+ >>> >>+ mutex_lock(&inode->i_mutex); >>> >>+ status = security_inode_setsecctx(resfh->fh_dentry, >>> >>+ label->label, label->len); >>> >>+ mutex_unlock(&inode->i_mutex); >>> >>+ >>> >>+ if (status) >>> >>+ /* >>> >>+ * We should probably fail the whole open at this point, >>> >>+ * but we've already created or opened the file, so it's >>> >>+ * too late; So this seems the least of evils: >>> >>+ */ >>> >>+ bmval[2] &= ~FATTR4_WORD2_SECURITY_LABEL; >>> > >>> >Is there any way to avoid this? >>> > >>> >How does the vfs open code handle this? It has to be able to set a >>> >security contexts atomically on open(O_CREAT), doesn't it? >>> > >>> >>> I believe the way this is handled is that the inode is created and >>> labeled and then only after that is it bound to the namespace. >>> Because of that ordering we can fail and release the inode without >>> it ever having a dentry in the namespace. >> >> Grepping around.... Looks like that's done by >> security_inode_init_security(), from the filesystem's create method. >> >> So we'd need to be able to pass something down to there. >> >> Is the current client actually expected to use this? (So are we going >> to see a lot of opens that set the label?) >> >> --b. > > I don't have all the code infront of me but we have a different hook > to do that. The call to nfsd4_security_inode_setsecctx is supposed to > be used from the setattr handlers to do the equivalent of a setxattr > on the file over NFS. The actual creation gets done with something > like security_dentry_init_security which should be in an earlier > patch. I'd have to look more clearly at the code to find out. Also > where did we come up with 128 for label length? The SELinux code > assumes a starting point of 255 and goes up from there as needed. The > MLS policies will definitely exceed a 128 byte label. If anyone cares, Smack labels can (now) be 255 characters. Also, when (if) we get multiple concurrent LSMs the "security context" may include information for more than one LSM. 128 bytes is going to look pretty tiny then. smack='com.corportation.service'selinux='system_u:object_r:bin_t:s0' > > Dave > -- > To unsubscribe from this list: send the line "unsubscribe > linux-security-module" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >