On Wed, 2017-10-25 at 13:05 -0200, Bruno E. O. Meneguele wrote:
> On 24-10, Mimi Zohar wrote:
> > On Tue, 2017-10-24 at 15:37 -0200, Bruno E. O. Meneguele wrote:
> > > When the user requests MODULE_CHECK policy and its kernel is compiled
> > > with CONFIG_MODULE_SIG_FORCE not set, all modules would not load, just
> > > those loaded in initram time. One option the user would have would be
> > > set a kernel cmdline param (module.sig_enforce) to true, but the IMA
> > > module check code doesn't rely on this value, it checks just
> > > CONFIG_MODULE_SIG_FORCE.
> > >
> > > This patch solves this problem checking for the exported value of
> > > module.sig_enforce cmdline param intead of CONFIG_MODULE_SIG_FORCE,
> > > which holds the effective value (CONFIG || param).
> > >
> > > Signed-off-by: Bruno E. O. Meneguele <brdeoliv@xxxxxxxxxx>
> > > ---
> > > security/integrity/ima/ima_main.c | 6 +++---
> > > 1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> > > index e4ab8ef8016e..d11a7fcc5c8b 100644
> > > --- a/security/integrity/ima/ima_main.c
> > > +++ b/security/integrity/ima/ima_main.c
> > > @@ -356,12 +356,12 @@ void ima_post_path_mknod(struct dentry *dentry)
> > > */
> > > int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
> > > {
> > > + bool sig_enforce = is_module_sig_enforced();
> > > +
> > > if (!file && read_id == READING_MODULE) {
> >
> > The only reason for getting here is that you're using the old module
> > load syscall. Is there a reason for not using the new one, which
> > passes the file descriptor?
> Basicaly because the way kmod handles compressed (gz/xz) modules. The
> way it's today would require major changes in the code or some kind of
> memfd_create() + xattrs reassignement in order to finit_module() be used
> correctly.
>
> Considering it would take some time to be accepted or even to figure out
> the correct way to tackle it, the current IMA module check code works
> aside kernel module signature validation, which is fine for now for me,
> but has the problem that this patch tries to solve in the
> CONFIG_MODULE_SIG_FORCE check (ignoring module.sig_enforce cmdline
> param).
Thank you for the reasoning. BTW, these patches are now queued.
> > > -#ifndef CONFIG_MODULE_SIG_FORCE
> > > - if ((ima_appraise & IMA_APPRAISE_MODULES) &&
> > > + if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES) &&
> > > (ima_appraise & IMA_APPRAISE_ENFORCE))
> > > return -EACCES; /* INTEGRITY_UNKNOWN */
> > > -#endif
> > > return 0; /* We rely on module signature checking */
> > > }
> > > return 0;
> >
> >
>
