[PATCH 11/11] evm: Don't update hmacs in user ns mounts

[PATCH 11/11] evm: Don't update hmacs in user ns mounts

[Dongsu Park]

From: Seth Forshee <seth.forshee@canonical.com>

The kernel should not calculate new hmacs for mounts done by
non-root users. Update evm_calc_hmac_or_hash() to refuse to
calculate new hmacs for mounts for non-init user namespaces.

Cc: linux-integrity@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: James Morris <james.l.morris@oracle.com>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Dongsu Park <dongsu@kinvolk.io>
---
 security/integrity/evm/evm_crypto.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index bcd64baf..729f4545 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -190,7 +190,8 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
 	int error;
 	int size;
 
-	if (!(inode->i_opflags & IOP_XATTR))
+	if (!(inode->i_opflags & IOP_XATTR) ||
+	    inode->i_sb->s_user_ns != &init_user_ns)
 		return -EOPNOTSUPP;
 
 	desc = init_desc(type);
-- 
2.13.6

Re: [PATCH 11/11] evm: Don't update hmacs in user ns mounts

[Serge E. Hallyn]

On Fri, Dec 22, 2017 at 03:32:35PM +0100, Dongsu Park wrote:
> From: Seth Forshee <seth.forshee@canonical.com>
> 
> The kernel should not calculate new hmacs for mounts done by
> non-root users. Update evm_calc_hmac_or_hash() to refuse to
> calculate new hmacs for mounts for non-init user namespaces.
> 
> Cc: linux-integrity@vger.kernel.org
> Cc: linux-security-module@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: James Morris <james.l.morris@oracle.com>
> Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>

Hi Mimi,

does this change seem sufficient to you?

> Cc: "Serge E. Hallyn" <serge@hallyn.com>
> Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
> Signed-off-by: Dongsu Park <dongsu@kinvolk.io>
> ---
>  security/integrity/evm/evm_crypto.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> index bcd64baf..729f4545 100644
> --- a/security/integrity/evm/evm_crypto.c
> +++ b/security/integrity/evm/evm_crypto.c
> @@ -190,7 +190,8 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
>  	int error;
>  	int size;
>  
> -	if (!(inode->i_opflags & IOP_XATTR))
> +	if (!(inode->i_opflags & IOP_XATTR) ||
> +	    inode->i_sb->s_user_ns != &init_user_ns)
>  		return -EOPNOTSUPP;
>  
>  	desc = init_desc(type);
> -- 
> 2.13.6

Re: [PATCH 11/11] evm: Don't update hmacs in user ns mounts

[Mimi Zohar]

Hi Serge,

On Fri, 2017-12-22 at 22:03 -0600, Serge E. Hallyn wrote:
> On Fri, Dec 22, 2017 at 03:32:35PM +0100, Dongsu Park wrote:
> > From: Seth Forshee <seth.forshee@canonical.com>
> > 
> > The kernel should not calculate new hmacs for mounts done by
> > non-root users. Update evm_calc_hmac_or_hash() to refuse to
> > calculate new hmacs for mounts for non-init user namespaces.
> > 
> > Cc: linux-integrity@vger.kernel.org
> > Cc: linux-security-module@vger.kernel.org
> > Cc: linux-kernel@vger.kernel.org
> > Cc: James Morris <james.l.morris@oracle.com>
> > Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
> 
> Hi Mimi,
> 
> does this change seem sufficient to you?

I think this is the correct behavior in the context of fuse file
systems.  This patch, the "ima: define a new policy option named
force" patch, and an updated IMA policy should be upstreamed together.
 The cover letter should provide the motivation for these patches.

Mimi

> 
> > Cc: "Serge E. Hallyn" <serge@hallyn.com>
> > Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
> > Signed-off-by: Dongsu Park <dongsu@kinvolk.io>
> > ---
> >  security/integrity/evm/evm_crypto.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> > index bcd64baf..729f4545 100644
> > --- a/security/integrity/evm/evm_crypto.c
> > +++ b/security/integrity/evm/evm_crypto.c
> > @@ -190,7 +190,8 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
> >  	int error;
> >  	int size;
> >  
> > -	if (!(inode->i_opflags & IOP_XATTR))
> > +	if (!(inode->i_opflags & IOP_XATTR) ||
> > +	    inode->i_sb->s_user_ns != &init_user_ns)
> >  		return -EOPNOTSUPP;
> >  
> >  	desc = init_desc(type);
> > -- 
> > 2.13.6
> 

Re: [PATCH 11/11] evm: Don't update hmacs in user ns mounts

[Mimi Zohar]

On Sun, 2017-12-24 at 00:12 -0500, Mimi Zohar wrote:
> Hi Serge,
> 
> On Fri, 2017-12-22 at 22:03 -0600, Serge E. Hallyn wrote:
> > On Fri, Dec 22, 2017 at 03:32:35PM +0100, Dongsu Park wrote:
> > > From: Seth Forshee <seth.forshee@canonical.com>
> > > 
> > > The kernel should not calculate new hmacs for mounts done by
> > > non-root users. Update evm_calc_hmac_or_hash() to refuse to
> > > calculate new hmacs for mounts for non-init user namespaces.
> > > 
> > > Cc: linux-integrity@vger.kernel.org
> > > Cc: linux-security-module@vger.kernel.org
> > > Cc: linux-kernel@vger.kernel.org
> > > Cc: James Morris <james.l.morris@oracle.com>
> > > Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
> > 
> > Hi Mimi,
> > 
> > does this change seem sufficient to you?
> 
> I think this is the correct behavior in the context of fuse file
> systems.  This patch, the "ima: define a new policy option named
> force" patch, and an updated IMA policy should be upstreamed together.
>  The cover letter should provide the motivation for these patches.

Ah, this patch is being upstreamed with the fuse mounts patches.  I
guess Seth is planning on posting the IMA policy changes for fuse
separately.

Mimi