Re: [PATCH v3 19/22] ima: support for kexec image and initramfs

[Mimi Zohar <zohar@linux.vnet.ibm.com>]

On Wed, 2016-02-10 at 23:09 +0200, Dmitry Kasatkin wrote:
> On Wed, Feb 3, 2016 at 9:06 PM, Mimi Zohar <zohar@linux.vnet.ibm.com> wrote:
> > Add IMA policy support for measuring/appraising the kexec image and
> > initramfs.
> >
> > Moving the enumeration to the vfs layer simplified the patches, allowing
> > the IMA changes, for the most part, to be separated from the other
> > changes.  Unfortunately, passing either a kernel_read_file_id or a
> > ima_hooks enumeration within IMA is messy.
> >
> > Option 1: duplicate kernel_read_file enumeration in ima_hooks
> >
> > enum kernel_read_file_id {
> >         ...
> >         READING_KEXEC_IMAGE,
> >         READING_KEXEC_INITRAMFS,
> >         READING_MAX_ID
> >
> > enum ima_hooks {
> >         ...
> >         KEXEC_CHECK
> >         INITRAMFS_CHECK
> >
> > Option 2: define ima_hooks as extension of kernel_read_file
> > eg: enum ima_hooks {
> >         FILE_CHECK = READING_MAX_ID,
> >         MMAP_CHECK,
> >
> > In order to pass both kernel_read_file_id and ima_hooks values, we
> > would need to specify a struct containing a union.
> >
> > struct caller_id {
> >         union {
> >                 enum ima_hooks func_id;
> >                 enum kernel_read_file_id read_id;
> >         };
> > };
> >
> > Option 3: incorportate the ima_hooks enumeration into kernel_read_file_id,
> > perhaps changing the enumeration name.
> >
> > For now, duplicate the new READING_KEXEC_IMAGE/INITRAMFS in ima_hooks.
> >
> > Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
> > ---
> >  Documentation/ABI/testing/ima_policy |  2 +-
> >  security/integrity/ima/ima.h         |  2 ++
> >  security/integrity/ima/ima_main.c    | 19 ++++++++++++++++---
> >  security/integrity/ima/ima_policy.c  | 13 ++++++++++++-
> >  4 files changed, 31 insertions(+), 5 deletions(-)
> >
> > diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
> > index 0a378a8..e80f767 100644
> > --- a/Documentation/ABI/testing/ima_policy
> > +++ b/Documentation/ABI/testing/ima_policy
> > @@ -26,7 +26,7 @@ Description:
> >                         option: [[appraise_type=]] [permit_directio]
> >
> >                 base:   func:= [BPRM_CHECK][MMAP_CHECK][FILE_CHECK][MODULE_CHECK]
> > -                               [FIRMWARE_CHECK]
> > +                               [FIRMWARE_CHECK] [KEXEC_CHECK] [INITRAMFS_CHECK]
> >                         mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
> >                                [[^]MAY_EXEC]
> >                         fsmagic:= hex value
> > diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> > index a5d2592..832e62a 100644
> > --- a/security/integrity/ima/ima.h
> > +++ b/security/integrity/ima/ima.h
> > @@ -147,6 +147,8 @@ enum ima_hooks {
> >         POST_SETATTR,
> >         MODULE_CHECK,
> >         FIRMWARE_CHECK,
> > +       KEXEC_CHECK,
> > +       INITRAMFS_CHECK,
> >         MAX_CHECK
> >  };
> >
> > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> > index 1e91d94..ccf9526 100644
> > --- a/security/integrity/ima/ima_main.c
> > +++ b/security/integrity/ima/ima_main.c
> > @@ -355,7 +355,7 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
> >  int ima_post_read_file(struct file *file, void *buf, loff_t size,
> >                        enum kernel_read_file_id read_id)
> >  {
> > -       enum ima_hooks func = FILE_CHECK;
> > +       enum ima_hooks func;
> >
> >         if (!file && read_id == READING_FIRMWARE) {
> >                 if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
> > @@ -373,10 +373,23 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
> >                 return 0;
> >         }
> >
> > -       if (read_id == READING_FIRMWARE)
> > +       switch (read_id) {
> > +       case READING_FIRMWARE:
> >                 func = FIRMWARE_CHECK;
> > -       else if (read_id == READING_MODULE)
> > +               break;
> > +       case READING_MODULE:
> >                 func = MODULE_CHECK;
> > +               break;
> > +       case READING_KEXEC_IMAGE:
> > +               func = KEXEC_CHECK;
> > +               break;
> > +       case READING_KEXEC_INITRAMFS:
> > +               func = INITRAMFS_CHECK;
> > +               break;
> > +       default:
> > +               func = FILE_CHECK;
> > +               break;
> > +       }
> >
> 
> I would define a separate function like "int ima_read_id_to_func(id)"
> which search over the map
> 
> Something like...
> 
> struct
> {
>      int id;
>      int func;
> }  map[] = {
>   { .id = READING_FIRMWARE, .fun = FIRMWARE_CHECK },
>    ...
>   { -1, 0 }
> };
> 

So we stay with the duplication (option 1), but clean it up.  That works
for me.

Mimi


> >         return process_measurement(file, buf, size, MAY_READ, func, 0);
> >  }
> > diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> > index 7571ce8..d02560e 100644
> > --- a/security/integrity/ima/ima_policy.c
> > +++ b/security/integrity/ima/ima_policy.c
> > @@ -612,6 +612,10 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
> >                                 entry->func = MMAP_CHECK;
> >                         else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
> >                                 entry->func = BPRM_CHECK;
> > +                       else if (strcmp(args[0].from, "KEXEC_CHECK") == 0)
> > +                               entry->func = KEXEC_CHECK;
> > +                       else if (strcmp(args[0].from, "INITRAMFS_CHECK") == 0)
> > +                               entry->func = INITRAMFS_CHECK;
> >                         else
> >                                 result = -EINVAL;
> >                         if (!result)
> > @@ -855,7 +859,8 @@ static char *mask_tokens[] = {
> >
> >  enum {
> >         func_file = 0, func_mmap, func_bprm,
> > -       func_module, func_firmware, func_post
> > +       func_module, func_firmware, func_post,
> > +       func_kexec, func_initramfs
> >  };
> >
> >  static char *func_tokens[] = {
> > @@ -929,6 +934,12 @@ static void policy_func_show(struct seq_file *m, enum ima_hooks func)
> >         case POST_SETATTR:
> >                 seq_printf(m, pt(Opt_func), ft(func_post));
> >                 break;
> > +       case KEXEC_CHECK:
> > +               seq_printf(m, pt(Opt_func), ft(func_kexec));
> > +               break;
> > +       case INITRAMFS_CHECK:
> > +               seq_printf(m, pt(Opt_func), ft(func_initramfs));
> > +               break;
> >         default:
> >                 snprintf(tbuf, sizeof(tbuf), "%d", func);
> >                 seq_printf(m, pt(Opt_func), tbuf);
> > --
> > 2.1.0
> >
> 
> 
>