Re: [Linux-ima-devel] [PATCH v4 4/5] ima: define "fs_unsafe" builtin policy

[Dmitry Kasatkin <dmitry.kasatkin@gmail.com>]

Looks good to me.

On Wed, Jul 26, 2017 at 4:22 PM, Mimi Zohar <zohar@linux.vnet.ibm.com> wrote:
> Permit normally denied access/execute permission for files in policy
> on IMA unsupported filesystems.  This patch defines "fs_unsafe", a
> builtin policy.
>
> Mimi Zohar <zohar@linux.vnet.ibm.com>
>
> ---
> Changelog v3:
> - include dont_failsafe rule when displaying policy
>
>  Documentation/admin-guide/kernel-parameters.txt |  8 +++++++-
>  security/integrity/ima/ima_policy.c             | 12 ++++++++++++
>  2 files changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index d9c171ce4190..4e303be83df6 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1502,7 +1502,7 @@
>
>         ima_policy=     [IMA]
>                         The builtin policies to load during IMA setup.
> -                       Format: "tcb | appraise_tcb | secure_boot"
> +                       Format: "tcb | appraise_tcb | secure_boot | fs_unsafe"
>
>                         The "tcb" policy measures all programs exec'd, files
>                         mmap'd for exec, and all files opened with the read
> @@ -1517,6 +1517,12 @@
>                         of files (eg. kexec kernel image, kernel modules,
>                         firmware, policy, etc) based on file signatures.
>
> +                       The "fs_unsafe" policy permits normally denied
> +                       access/execute permission for files in policy on IMA
> +                       unsupported filesystems.  Note this option, as the
> +                       name implies, is not safe and not recommended for
> +                       any environments other than testing.
> +
>         ima_tcb         [IMA] Deprecated.  Use ima_policy= instead.
>                         Load a policy which meets the needs of the Trusted
>                         Computing Base.  This means IMA will measure all
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 43b85a4fb8e8..cddd9dfb01e1 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -169,6 +169,10 @@ static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
>          .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
>  };
>
> +static struct ima_rule_entry dont_failsafe_rules[] __ro_after_init = {
> +       {.action = DONT_FAILSAFE}
> +};
> +
>  static LIST_HEAD(ima_default_rules);
>  static LIST_HEAD(ima_policy_rules);
>  static LIST_HEAD(ima_temp_rules);
> @@ -188,6 +192,7 @@ __setup("ima_tcb", default_measure_policy_setup);
>
>  static bool ima_use_appraise_tcb __initdata;
>  static bool ima_use_secure_boot __initdata;
> +static bool ima_use_dont_failsafe __initdata;
>  static int __init policy_setup(char *str)
>  {
>         char *p;
> @@ -201,6 +206,10 @@ static int __init policy_setup(char *str)
>                         ima_use_appraise_tcb = 1;
>                 else if (strcmp(p, "secure_boot") == 0)
>                         ima_use_secure_boot = 1;
> +               else if (strcmp(p, "fs_unsafe") == 0) {
> +                       ima_use_dont_failsafe = 1;
> +                       set_failsafe(0);
> +               }
>         }
>
>         return 1;
> @@ -470,6 +479,9 @@ void __init ima_init_policy(void)
>                         temp_ima_appraise |= IMA_APPRAISE_POLICY;
>         }
>
> +       if (ima_use_dont_failsafe)
> +               list_add_tail(&dont_failsafe_rules[0].list, &ima_default_rules);
> +
>         ima_rules = &ima_default_rules;
>         ima_update_policy_flag();
>  }
> --
> 2.7.4
>
>
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-- 
Thanks,
Dmitry