Re: [PATCH v3 20/22] ima: load policy using path

[Petko Manolov <petkan@mip-labs.com>]

On 16-02-08 09:58:16, Dmitry Kasatkin wrote:
> 
> ________________________________________
> From: Petko Manolov [petkan@mip-labs.com]
> Sent: Sunday, February 07, 2016 9:59 PM
> To: Mimi Zohar
> Cc: linux-security-module@vger.kernel.org; Luis R. Rodriguez; kexec@lists.infradead.org; linux-modules@vger.kernel.org; fsdevel@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@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@huawei.com>
> > Signed-off-by: Mimi Zohar <zohar@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