linux-kernel - Re: [PATCH 1/3] IMA:Define a new hook to measure the kexec boot command line arguments

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Date:   Wed, 19 Jun 2019 15:21:40 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Prakhar Srivastava <prsriva02@...il.com>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     roberto.sassu@...wei.com
Subject: Re: [PATCH 1/3] IMA:Define a new hook to measure the kexec boot
 command line arguments

On Mon, 2019-06-17 at 11:35 -0700, Prakhar Srivastava wrote:
> Currently during soft reboot(kexec_file_load) boot command line
> arguments are not measured. Define hooks needed to measure kexec
> command line arguments during soft reboot(kexec_file_load).
> 
> - A new ima hook ima_kexec_cmdline is defined to be called by the
> kexec code.
> - A new function process_buffer_measurement is defined to measure
> the buffer hash into the IMA measurement list.
> - A new func policy KEXEC_CMDLINE is defined to control the
>  measurement.[Suggested by Mimi]
> 
> Signed-off-by: Prakhar Srivastava <prsriva02@...il.com>

With minor changes below, 
     Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>

> ---

> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index af341a80118f..1e233417a7af 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -605,6 +605,80 @@ int ima_load_data(enum kernel_load_data_id id)
>  	return 0;
>  }
>  
> +/*
> + * process_buffer_measurement - Measure the buffer to ima log.
> + * @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.
> + *
> + * 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)
> +{
> +	int ret = 0;
> +	struct ima_template_entry *entry = NULL;
> +	struct integrity_iint_cache iint = {};
> +	struct ima_event_data event_data = {.iint = &iint };
> +	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))
> +		goto out;

"out:" is a simple return, no freeing memory.  Just return here.

> +
> +	event_data.filename = eventname;

No need to initialize even_data.filename, here initialize it when it
is defined.

> +
> +	iint.ima_hash = &hash.hdr;
> +	iint.ima_hash->algo = ima_hash_algo;
> +	iint.ima_hash->length = hash_digest_size[ima_hash_algo];
> +
> +	ret = ima_calc_buffer_hash(buf, size, iint.ima_hash);
> +	if (ret < 0)
> +		goto out;
> +
> +	ret = ima_alloc_init_template(&event_data, &entry, template_desc);
> +	if (ret < 0)
> +		goto out;
> +
> +	if (action & IMA_MEASURE)

Why is this test needed again?

Mimi

> +		ret = ima_store_template(entry, violation, NULL, buf, pcr);
> +
> +	if (ret < 0)
> +		ima_free_template_entry(entry);
> +
> +out:
> +	return;
> +}
> +
> +/**
> + * ima_kexec_cmdline - measure kexec cmdline boot args
> + * @buf: pointer to buffer
> + * @size: size of buffer
> + *
> + * Buffers can only be measured, not appraised.
> + */
> +void ima_kexec_cmdline(const void *buf, int size)
> +{
> +	u32 secid;
> +
> +	if (buf && size != 0) {
> +		security_task_getsecid(current, &secid);
> +		process_buffer_measurement(buf, size, "kexec-cmdline",
> +					   current_cred(), secid);
> +	}
> +}
> +
>  static int __init init_ima(void)
>  {
>  	int error;
>