linux-kernel - Re: [PATCH v6 04/12] ima: Introduce is_ima

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Message-Id: <1522074273.3541.83.camel@linux.vnet.ibm.com>
Date:   Mon, 26 Mar 2018 10:24:33 -0400
From:   Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:     Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>,
        linux-integrity@...r.kernel.org
Cc:     linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Jessica Yu <jeyu@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        "AKASHI, Takahiro" <takahiro.akashi@...aro.org>
Subject: Re: [PATCH v6 04/12] ima: Introduce is_ima_sig()

On Fri, 2018-03-16 at 17:38 -0300, Thiago Jung Bauermann wrote:
> With the introduction of another IMA signature type (modsig), some places
> will need to check for both of them. It is cleaner to do that if there's a
> helper function to tell whether an xattr_value represents an IMA
> signature.

Initially the function name "is_ima_sig" is fine, since it reflects
the 'imasig' type.  Having a more generic function name would be
better when adding 'modsig' support.  As long as the function is
locally define, we can drop 'ima' from the name.  Perhaps something
like has_signature or is_signed() would be preferable.

Mimi


> 
> Suggested-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
> Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
> ---
>  security/integrity/ima/ima.h              | 5 +++++
>  security/integrity/ima/ima_appraise.c     | 7 +++----
>  security/integrity/ima/ima_template_lib.c | 2 +-
>  3 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 35fe91aa1fc9..4bafa6a97967 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -155,6 +155,11 @@ unsigned long ima_get_binary_runtime_size(void);
>  int ima_init_template(void);
>  void ima_init_template_list(void);
> 
> +static inline bool is_ima_sig(const struct evm_ima_xattr_data *xattr_value)
> +{
> +	return xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG;
> +}
> +
>  /*
>   * used to protect h_table and sha_table
>   */
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index a6b2995b7d0b..01172eab297b 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -325,15 +325,14 @@ int ima_appraise_measurement(enum ima_hooks func,
>  	} else if (status != INTEGRITY_PASS) {
>  		/* Fix mode, but don't replace file signatures. */
>  		if ((ima_appraise & IMA_APPRAISE_FIX) &&
> -		    (!xattr_value ||
> -		     xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
> +		    !is_ima_sig(xattr_value)) {
>  			if (!ima_fix_xattr(dentry, iint))
>  				status = INTEGRITY_PASS;
>  		}
> 
>  		/* Permit new files with file signatures, but without data. */
>  		if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE &&
> -		    xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) {
> +		    is_ima_sig(xattr_value)) {
>  			status = INTEGRITY_PASS;
>  		}
> 
> @@ -448,7 +447,7 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
>  		if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
>  			return -EINVAL;
>  		ima_reset_appraise_flags(d_backing_inode(dentry),
> -			xvalue->type == EVM_IMA_XATTR_DIGSIG);
> +					 is_ima_sig(xvalue));
>  		result = 0;
>  	}
>  	return result;
> diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
> index 5afaa53decc5..afb52a90e532 100644
> --- a/security/integrity/ima/ima_template_lib.c
> +++ b/security/integrity/ima/ima_template_lib.c
> @@ -380,7 +380,7 @@ int ima_eventsig_init(struct ima_event_data *event_data,
>  {
>  	struct evm_ima_xattr_data *xattr_value = event_data->xattr_value;
> 
> -	if ((!xattr_value) || (xattr_value->type != EVM_IMA_XATTR_DIGSIG))
> +	if (!is_ima_sig(xattr_value))
>  		return 0;
> 
>  	return ima_write_template_field_data(xattr_value, event_data->xattr_len,
>