Re: [RFC PATCH v5 3/4] ima: define '.ima' as a builtin 'trusted' keyring

[Mimi Zohar]

On Sat, 2014-06-07 at 00:53 +0300, Dmitry Kasatkin wrote: 
> On 3 June 2014 20:58, Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> wrote:
> > Require all keys added to the IMA keyring be signed by an
> > existing trusted key on the system trusted keyring.
> >
> > Changelog v5:
> > - Move integrity_init_keyring() to init_ima() - Dmitry
> > - reset keyring[id] on failure - Dmitry
> >
> > Changelog v1:
> > - don't link IMA trusted keyring to user keyring
> >
> > Changelog:
> > - define stub integrity_init_keyring() function (reported-by Fengguang Wu)
> > - differentiate between regular and trusted keyring names.
> > - replace printk with pr_info (D. Kasatkin)
> > - only make the IMA keyring a trusted keyring (reported-by D. Kastatkin)
> > - define stub integrity_init_keyring() definition based on
> >   CONFIG_INTEGRITY_SIGNATURE, not CONFIG_INTEGRITY_ASYMMETRIC_KEYS.
> >   (reported-by Jim Davis)
> >
> > Signed-off-by: Mimi Zohar<zohar@xxxxxxxxxxxxxxxxxx>
> > ---
> >  security/integrity/digsig.c       | 26 ++++++++++++++++++++++++++
> >  security/integrity/ima/Kconfig    |  8 ++++++++
> >  security/integrity/ima/ima_main.c | 12 ++++++++++--
> >  security/integrity/integrity.h    |  5 +++++
> >  4 files changed, 49 insertions(+), 2 deletions(-)
> >
> > diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
> > index b4af4eb..fa4c2fd 100644
> > --- a/security/integrity/digsig.c
> > +++ b/security/integrity/digsig.c
> > @@ -13,7 +13,9 @@
> >  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> >
> >  #include <linux/err.h>
> > +#include <linux/sched.h>
> >  #include <linux/rbtree.h>
> > +#include <linux/cred.h>
> >  #include <linux/key-type.h>
> >  #include <linux/digsig.h>
> >
> > @@ -24,7 +26,11 @@ static struct key *keyring[INTEGRITY_KEYRING_MAX];
> >  static const char *keyring_name[INTEGRITY_KEYRING_MAX] = {
> >         "_evm",
> >         "_module",
> > +#ifndef CONFIG_IMA_TRUSTED_KEYRING
> >         "_ima",
> > +#else
> > +       ".ima",
> > +#endif
> >  };
> >
> >  int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
> > @@ -56,3 +62,23 @@ int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
> >
> >         return -EOPNOTSUPP;
> >  }
> > +
> > +int integrity_init_keyring(const unsigned int id)
> > +{
> > +       const struct cred *cred = current_cred();
> > +
> > +       keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
> > +                                   KGIDT_INIT(0), cred,
> > +                                   ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
> > +                                     KEY_USR_VIEW | KEY_USR_READ |
> > +                                     KEY_USR_WRITE | KEY_USR_SEARCH),
> > +                                   KEY_ALLOC_NOT_IN_QUOTA, NULL);
> > +       if (!IS_ERR(keyring[id]))
> > +               set_bit(KEY_FLAG_TRUSTED_ONLY, &keyring[id]->flags);
> > +       else {
> > +               pr_info("Can't allocate %s keyring (%ld)\n",
> > +                       keyring_name[id], PTR_ERR(keyring[id]));
> > +               keyring[id] = NULL;
> > +       }
> > +       return 0;
> > +}
> > diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
> > index 81a2797..dad8d4c 100644
> > --- a/security/integrity/ima/Kconfig
> > +++ b/security/integrity/ima/Kconfig
> > @@ -123,3 +123,11 @@ config IMA_APPRAISE
> >           For more information on integrity appraisal refer to:
> >           <http://linux-ima.sourceforge.net>
> >           If unsure, say N.
> > +
> > +config IMA_TRUSTED_KEYRING
> > +       bool "Require all keys on the _ima keyring be signed"
> > +       depends on IMA_APPRAISE && SYSTEM_TRUSTED_KEYRING
> > +       default y
> > +       help
> > +          This option requires that all keys added to the _ima
> > +          keyring be signed by a key on the system trusted keyring.
> > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> > index 09baa33..4c60cc5 100644
> > --- a/security/integrity/ima/ima_main.c
> > +++ b/security/integrity/ima/ima_main.c
> > @@ -328,8 +328,16 @@ static int __init init_ima(void)
> >
> >         hash_setup(CONFIG_IMA_DEFAULT_HASH);
> >         error = ima_init();
> > -       if (!error)
> > -               ima_initialized = 1;
> > +       if (error)
> > +               goto out;
> > +
> > +#ifdef CONFIG_IMA_TRUSTED_KEYRING
> > +       error = integrity_init_keyring(INTEGRITY_KEYRING_IMA);
> > +       if (error)
> > +               goto out;
> > +#endif
> 
> integrity_init_keyring() has variation in header file...
> Why do you need #ifdef in .c file? You you usually do not like it...

Up to now, unsigned certificates could be added to the IMA keyring.  We
can not all of a sudden require all keys being added to the IMA keyring
to be signed.  Although there is a stub integrity_init_keyring()
function definition, it is based on CONFIG_INTEGRITY_SIGNATURE, not
CONFIG_IMA_TRUSTED_KEYRING.

Right, ifdef's don't belong in C code.  One solution would be to define
ima_init_keyring() as a wrapper for integrity_init_keyring() and a stub
function.

Mimi

> 
> > +       ima_initialized = 1;
> > +out:
> >         return error;
> >  }
> >
> > diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
> > index 33c0a70..09c440d 100644
> > --- a/security/integrity/integrity.h
> > +++ b/security/integrity/integrity.h
> > @@ -124,6 +124,7 @@ struct integrity_iint_cache *integrity_iint_find(struct inode *inode);
> >  int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
> >                             const char *digest, int digestlen);
> >
> > +int integrity_init_keyring(const unsigned int id);
> >  #else
> >
> >  static inline int integrity_digsig_verify(const unsigned int id,
> > @@ -133,6 +134,10 @@ static inline int integrity_digsig_verify(const unsigned int id,
> >         return -EOPNOTSUPP;
> >  }
> >
> > +static inline int integrity_init_keyring(const unsigned int id)
> > +{
> > +       return 0;
> > +}
> >  #endif /* CONFIG_INTEGRITY_SIGNATURE */
> >
> >  #ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
> > --
> > 1.8.1.4
> >
> > --
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> 
> 
> 


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