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

[Dmitry Kasatkin]

On Wed, Feb 3, 2016 at 9:06 PM, Mimi Zohar <zohar at 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 at 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 }
};

Dmitry


>         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
>



-- 
Thanks,
Dmitry