Re: [PATCH 3/6] ima: Simplify policy_func_show.

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

On Thu, 2017-04-20 at 17:40 -0300, Thiago Jung Bauermann wrote:
> Am Donnerstag, 20. April 2017, 08:13:23 BRT schrieb Mimi Zohar:
> > On Tue, 2017-04-18 at 17:17 -0300, Thiago Jung Bauermann wrote:
> > > If the func_tokens array uses the same indices as enum ima_hooks,
> > > policy_func_show can be a lot simpler, and the func_* enum becomes
> > > unnecessary.
> > 
> > My main concern with separating the enumeration from the string
> > definition is that they might become out of sync.  Perhaps using
> > macros, similar to those used for kernel_read_file_id_str(), would be
> > better?
> 
> I agree that it would be better. Is the patch below what you had in mind?

Yes, I haven't tested it yet, but it looks right.
> 
> I also noticed that policy_func_show can be even simpler if we stop using the 
> printf format string from the policy_tokens table. What do you think?
> 
> -- 
> Thiago Jung Bauermann
> IBM Linux Technology Center
> 
> 
> From 594628c94f5dd7c6d2624944a76b6a01f9668128 Mon Sep 17 00:00:00 2001
> From: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
> Date: Mon, 10 Apr 2017 14:59:44 -0300
> Subject: [PATCH 3/6] ima: Simplify policy_func_show.
> 
> If the func_tokens array uses the same indices as enum ima_hooks,
> policy_func_show can be a lot simpler, and the func_* enum becomes
> unnecessary.
> 
> Also, if we use the same macro trick used by kernel_read_file_id_str we can
> use one hooks list for both the enum and the string array, making sure they
> are always in sync (suggested by Mimi Zohar).

> Finally, by using the printf pattern for the function token directly
> instead of using the pt macro we can simplify policy_func_show even further
> and avoid the need of having a temporary buffer. Since the only use of
> Opt_func's printf pattern in policy_tokens was in policy_func_show, we
> don't need it at all anymore so remove it.
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
> ---
>  security/integrity/ima/ima.h        | 25 +++++++++-------
>  security/integrity/ima/ima_policy.c | 60 +++++--------------------------------
>  2 files changed, 22 insertions(+), 63 deletions(-)
> 
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index b563fbd4d122..51ef805cf7f3 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -172,17 +172,22 @@ static inline unsigned long ima_hash_key(u8 *digest)
>  	return hash_long(*digest, IMA_HASH_BITS);
>  }
> 
> +#define __ima_hooks(hook)		\
> +	hook(NONE)			\
> +	hook(FILE_CHECK)		\
> +	hook(MMAP_CHECK)		\
> +	hook(BPRM_CHECK)		\
> +	hook(POST_SETATTR)		\
> +	hook(MODULE_CHECK)		\
> +	hook(FIRMWARE_CHECK)		\
> +	hook(KEXEC_KERNEL_CHECK)	\
> +	hook(KEXEC_INITRAMFS_CHECK)	\
> +	hook(POLICY_CHECK)		\
> +	hook(MAX_CHECK)
> +#define __ima_hook_enumify(ENUM)	ENUM,
> +
>  enum ima_hooks {
> -	FILE_CHECK = 1,
> -	MMAP_CHECK,
> -	BPRM_CHECK,
> -	POST_SETATTR,
> -	MODULE_CHECK,
> -	FIRMWARE_CHECK,
> -	KEXEC_KERNEL_CHECK,
> -	KEXEC_INITRAMFS_CHECK,
> -	POLICY_CHECK,
> -	MAX_CHECK
> +	__ima_hooks(__ima_hook_enumify)
>  };
> 
>  /* LIM API function definitions */
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index cfda5d7b17ec..39d43a5beb5a 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -503,7 +503,7 @@ static match_table_t policy_tokens = {
>  	{Opt_subj_user, "subj_user=%s"},
>  	{Opt_subj_role, "subj_role=%s"},
>  	{Opt_subj_type, "subj_type=%s"},
> -	{Opt_func, "func=%s"},
> +	{Opt_func, NULL},
>  	{Opt_mask, "mask=%s"},
>  	{Opt_fsmagic, "fsmagic=%s"},
>  	{Opt_fsuuid, "fsuuid=%s"},
> @@ -896,23 +896,10 @@ static const char *const mask_tokens[] = {
>  	"MAY_APPEND"
>  };
> 
> -enum {
> -	func_file = 0, func_mmap, func_bprm,
> -	func_module, func_firmware, func_post,
> -	func_kexec_kernel, func_kexec_initramfs,
> -	func_policy
> -};
> +#define __ima_hook_stringify(str)	#str,
> 
>  static const char *const func_tokens[] = {
> -	"FILE_CHECK",
> -	"MMAP_CHECK",
> -	"BPRM_CHECK",
> -	"MODULE_CHECK",
> -	"FIRMWARE_CHECK",
> -	"POST_SETATTR",
> -	"KEXEC_KERNEL_CHECK",
> -	"KEXEC_INITRAMFS_CHECK",
> -	"POLICY_CHECK"
> +	__ima_hooks(__ima_hook_stringify)
>  };
> 
>  void *ima_policy_start(struct seq_file *m, loff_t *pos)
> @@ -949,49 +936,16 @@ void ima_policy_stop(struct seq_file *m, void *v)
> 
>  #define pt(token)	policy_tokens[token + Opt_err].pattern
>  #define mt(token)	mask_tokens[token]
> -#define ft(token)	func_tokens[token]
> 
>  /*
>   * policy_func_show - display the ima_hooks policy rule
>   */
>  static void policy_func_show(struct seq_file *m, enum ima_hooks func)
>  {
> -	char tbuf[64] = {0,};
> -
> -	switch (func) {
> -	case FILE_CHECK:
> -		seq_printf(m, pt(Opt_func), ft(func_file));
> -		break;
> -	case MMAP_CHECK:
> -		seq_printf(m, pt(Opt_func), ft(func_mmap));
> -		break;
> -	case BPRM_CHECK:
> -		seq_printf(m, pt(Opt_func), ft(func_bprm));
> -		break;
> -	case MODULE_CHECK:
> -		seq_printf(m, pt(Opt_func), ft(func_module));
> -		break;
> -	case FIRMWARE_CHECK:
> -		seq_printf(m, pt(Opt_func), ft(func_firmware));
> -		break;
> -	case POST_SETATTR:
> -		seq_printf(m, pt(Opt_func), ft(func_post));
> -		break;
> -	case KEXEC_KERNEL_CHECK:
> -		seq_printf(m, pt(Opt_func), ft(func_kexec_kernel));
> -		break;
> -	case KEXEC_INITRAMFS_CHECK:
> -		seq_printf(m, pt(Opt_func), ft(func_kexec_initramfs));
> -		break;
> -	case POLICY_CHECK:
> -		seq_printf(m, pt(Opt_func), ft(func_policy));
> -		break;
> -	default:
> -		snprintf(tbuf, sizeof(tbuf), "%d", func);
> -		seq_printf(m, pt(Opt_func), tbuf);
> -		break;
> -	}
> -	seq_puts(m, " ");
> +	if (func > 0 && func < MAX_CHECK)
> +		seq_printf(m, "func=%s ", func_tokens[func]);
> +	else
> +		seq_printf(m, "func=%d ", func);

The only time this can happen is when __kernel_read_file_id() is
updated without updating the read_idmap[].  Perhaps we can display the
number and the appropriate __kernel_read_file_id string.

Mimi

>  }
> 
>  int ima_policy_show(struct seq_file *m, void *v)