Subject: Re: [PATCH v7 5/8] ima: make process_buffer_measurement() generic

From: Mimi Zohar <[email-masked]>
Date: Fri, 11 Oct 2019 09:14:01 -0400

[Cc'ing Prakhar Srivastava]

On Mon, 2019-10-07 at 21:14 -0400, Nayna Jain wrote:
> An additional measurement record is needed to indicate the blacklisted
> binary. The record will measure the blacklisted binary hash.
> 
> This patch makes the function process_buffer_measurement() generic to be
> called by the blacklisting function. It modifies the function to handle
> more than just the KEXEC_CMDLINE.

The purpose of this patch is to make process_buffer_measurement() more
generic.  The patch description should simply say,
process_buffer_measurement() is limited to measuring the kexec boot
command line.  This patch makes process_buffer_measurement() more
generic, allowing it to measure other types of buffer data (eg.
blacklisted binary hashes).

Mimi

> 
> Signed-off-by: Nayna Jain <[email-masked]>
> ---
>  security/integrity/ima/ima.h      |  3 +++
>  security/integrity/ima/ima_main.c | 29 ++++++++++++++---------------
>  2 files changed, 17 insertions(+), 15 deletions(-)
> 
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 3689081aaf38..ed86c1f70d7f 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -217,6 +217,9 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
>  			   struct evm_ima_xattr_data *xattr_value,
>  			   int xattr_len, const struct modsig *modsig, int pcr,
>  			   struct ima_template_desc *template_desc);
> +void process_buffer_measurement(const void *buf, int size,
> +				const char *eventname, int pcr,
> +				struct ima_template_desc *template_desc);
>  void ima_audit_measurement(struct integrity_iint_cache *iint,
>  			   const unsigned char *filename);
>  int ima_alloc_init_template(struct ima_event_data *event_data,
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 60027c643ecd..77115e884496 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -626,14 +626,14 @@ int ima_load_data(enum kernel_load_data_id id)
>   * @buf: pointer to the buffer that needs to be added to the log.
>   * @size: size of buffer(in bytes).
>   * @eventname: event name to be used for the buffer entry.
> - * @cred: a pointer to a credentials structure for user validation.
> - * @secid: the secid of the task to be validated.
> + * @pcr: pcr to extend the measurement
> + * @template_desc: template description
>   *
>   * Based on policy, the buffer is measured into the ima log.
>   */
> -static void process_buffer_measurement(const void *buf, int size,
> -				       const char *eventname,
> -				       const struct cred *cred, u32 secid)
> +void process_buffer_measurement(const void *buf, int size,
> +				const char *eventname, int pcr,
> +				struct ima_template_desc *template_desc)
>  {
>  	int ret = 0;
>  	struct ima_template_entry *entry = NULL;
> @@ -642,19 +642,11 @@ static void process_buffer_measurement(const void *buf, int size,
>  					    .filename = eventname,
>  					    .buf = buf,
>  					    .buf_len = size};
> -	struct ima_template_desc *template_desc = NULL;
>  	struct {
>  		struct ima_digest_data hdr;
>  		char digest[IMA_MAX_DIGEST_SIZE];
>  	} hash = {};
>  	int violation = 0;
> -	int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
> -	int action = 0;
> -
> -	action = ima_get_action(NULL, cred, secid, 0, KEXEC_CMDLINE, &pcr,
> -				&template_desc);
> -	if (!(action & IMA_MEASURE))
> -		return;
>  
>  	iint.ima_hash = &hash.hdr;
>  	iint.ima_hash->algo = ima_hash_algo;
> @@ -686,12 +678,19 @@ static void process_buffer_measurement(const void *buf, int size,
>   */
>  void ima_kexec_cmdline(const void *buf, int size)
>  {
> +	int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
> +	struct ima_template_desc *template_desc = NULL;
> +	int action;
>  	u32 secid;
>  
>  	if (buf && size != 0) {
>  		security_task_getsecid(current, &secid);
> -		process_buffer_measurement(buf, size, "kexec-cmdline",
> -					   current_cred(), secid);
> +		action = ima_get_action(NULL, current_cred(), secid, 0,
> +					KEXEC_CMDLINE, &pcr, &template_desc);
> +		if (!(action & IMA_MEASURE))
> +			return;
> +		process_buffer_measurement(buf, size, "kexec-cmdline", pcr,
> +					   template_desc);
>  	}
>  }
>