________________________________________
From: Petko Manolov [petkan@xxxxxxxxxxxx]
Sent: Monday, February 08, 2016 12:35 PM
To: Dmitry Kasatkin
Cc: Mimi Zohar; linux-security-module at vger.kernel.org; Luis R. Rodriguez; kexec at lists.infradead.org; linux-modules at vger.kernel.org; fsdevel at vger.kernel.org; David Howells; David Woodhouse; Kees Cook; Dmitry Torokhov; Dmitry Kasatkin; Eric Biederman; Rusty Russell; Dmitry Kasatkin
Subject: Re: [PATCH v3 20/22] ima: load policy using path
On 16-02-08 09:58:16, Dmitry Kasatkin wrote:
>
> ________________________________________
> From: Petko Manolov [petkan at mip-labs.com]
> Sent: Sunday, February 07, 2016 9:59 PM
> To: Mimi Zohar
> Cc: linux-security-module at vger.kernel.org; Luis R. Rodriguez; kexec at lists.infradead.org; linux-modules at vger.kernel.org; fsdevel at vger.kernel.org; David Howells; David Woodhouse; Kees Cook; Dmitry Torokhov; Dmitry Kasatkin; Eric Biederman; Rusty Russell; Dmitry Kasatkin; Dmitry Kasatkin
> Subject: Re: [PATCH v3 20/22] ima: load policy using path
>
> On 16-02-03 14:06:28, Mimi Zohar wrote:
> > From: Dmitry Kasatkin <d.kasatkin at samsung.com>
> >
> > We currently cannot do appraisal or signature vetting of IMA policies
> > since we currently can only load IMA policies by writing the contents
> > of the policy directly in, as follows:
> >
> > cat policy-file > <securityfs>/ima/policy
> >
> > If we provide the kernel the path to the IMA policy so it can load
> > the policy itself it'd be able to later appraise or vet the file
> > signature if it has one. This patch adds support to load the IMA
> > policy with a given path as follows:
> >
> > echo /etc/ima/ima_policy > /sys/kernel/security/ima/policy
> >
> > Changelog v3:
> > - moved kernel_read_file_from_path() to a separate patch
> > v2:
> > - after re-ordering the patches, replace calling integrity_kernel_read()
> > to read the file with kernel_read_file_from_path() (Mimi)
> > - Patch description re-written by Luis R. Rodriguez
> >
> > Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin at huawei.com>
> > Signed-off-by: Mimi Zohar <zohar at linux.vnet.ibm.com>
> > ---
> > include/linux/fs.h | 1 +
> > security/integrity/ima/ima_fs.c | 43 +++++++++++++++++++++++++++++++++++++++--
> > 2 files changed, 42 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index d4d556e..b648e6d 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -2531,6 +2531,7 @@ enum kernel_read_file_id {
> > READING_MODULE,
> > READING_KEXEC_IMAGE,
> > READING_KEXEC_INITRAMFS,
> > + READING_POLICY,
> > READING_MAX_ID
> > };
> >
> > diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
> > index f355231..00ccd67 100644
> > --- a/security/integrity/ima/ima_fs.c
> > +++ b/security/integrity/ima/ima_fs.c
> > @@ -22,6 +22,7 @@
> > #include <linux/rculist.h>
> > #include <linux/rcupdate.h>
> > #include <linux/parser.h>
> > +#include <linux/vmalloc.h>
> >
> > #include "ima.h"
> >
> > @@ -258,6 +259,41 @@ static const struct file_operations ima_ascii_measurements_ops = {
> > .release = seq_release,
> > };
> >
> > +static ssize_t ima_read_policy(char *path)
> > +{
> > + void *data;
> > + char *datap;
> > + loff_t size;
> > + int rc, pathlen = strlen(path);
> > +
> > + char *p;
> > +
> > + /* remove \n */
> > + datap = path;
> > + strsep(&datap, "\n");
> > +
> > + rc = kernel_read_file_from_path(path, &data, &size, 0, READING_POLICY);
> > + if (rc < 0)
> > + return rc;
> > +
> > + datap = data;
> > + while (size > 0 && (p = strsep(&datap, "\n"))) {
> > + pr_debug("rule: %s\n", p);
> > + rc = ima_parse_add_rule(p);
> > + if (rc < 0)
> > + break;
> > + size -= rc;
> > + }
> > +
> > + vfree(data);
> > + if (rc < 0)
> > + return rc;
> > + else if (size)
> > + return -EINVAL;
> > + else
> > + return pathlen;
> > +}
> > +
> > static ssize_t ima_write_policy(struct file *file, const char __user *buf,
> > size_t datalen, loff_t *ppos)
> > {
> > @@ -286,9 +322,12 @@ static ssize_t ima_write_policy(struct file *file, const char __user *buf,
> > result = mutex_lock_interruptible(&ima_write_mutex);
> > if (result < 0)
> > goto out_free;
> > - result = ima_parse_add_rule(data);
> > - mutex_unlock(&ima_write_mutex);
> >
> > + if (data[0] == '/')
>
> >It seems that if we feed relative path to ima_policy the update will fail...
>
> Yes, i think it is always a good idea to pass absolute path.
What if we at least emit a warning so people know what's wrong?
Petko
DK: May be a good idea to print that loading policy by path or not.
