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From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
To: Roberto Sassu <roberto.sassu@huawei.com>,
	zohar@linux.ibm.com, paul@paul-moore.com
Cc: stephen.smalley.work@gmail.com, prsriva02@gmail.com,
	tusharsu@linux.microsoft.com, linux-integrity@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, selinux@vger.kernel.org
Subject: Re: [PATCH v2 2/3] ima: Return int in the functions to measure a buffer
Date: Thu, 1 Jul 2021 09:15:46 -0700	[thread overview]
Message-ID: <75bf7a3f-fd0e-177b-5725-e5f8b1f68966@linux.microsoft.com> (raw)
In-Reply-To: <20210701125552.2958008-3-roberto.sassu@huawei.com>

On 7/1/2021 5:55 AM, Roberto Sassu wrote:
> ima_measure_critical_data() and process_buffer_measurement() currently
> don't return a result. A caller wouldn't be able to know whether those
> functions were executed successfully.
> 
> This patch modifies the return type from void to int, and returns 0 if the
> buffer has been successfully measured, a negative value otherwise.
> 
> Also, this patch does not modify the behavior of existing callers by
> processing the returned value. Instead, the value is stored in a variable
> marked as __maybe_unused.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
>   include/linux/ima.h                          | 15 +++---
>   security/integrity/ima/ima.h                 | 10 ++--
>   security/integrity/ima/ima_appraise.c        |  4 +-
>   security/integrity/ima/ima_asymmetric_keys.c |  4 +-
>   security/integrity/ima/ima_init.c            |  6 ++-
>   security/integrity/ima/ima_main.c            | 48 ++++++++++++--------
>   security/integrity/ima/ima_queue_keys.c      | 15 +++---
>   security/selinux/ima.c                       | 10 ++--
>   8 files changed, 66 insertions(+), 46 deletions(-)
> 
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index 81e830d01ced..60492263aa64 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -35,10 +35,10 @@ extern void ima_post_path_mknod(struct user_namespace *mnt_userns,
>   extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
>   extern int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size);
>   extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
> -extern void ima_measure_critical_data(const char *event_label,
> -				      const char *event_name,
> -				      const void *buf, size_t buf_len,
> -				      bool hash);
> +extern int ima_measure_critical_data(const char *event_label,
> +				     const char *event_name,
> +				     const void *buf, size_t buf_len,
> +				     bool hash);
>   
>   #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
>   extern void ima_appraise_parse_cmdline(void);
> @@ -144,10 +144,13 @@ static inline int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size
>   
>   static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
>   
> -static inline void ima_measure_critical_data(const char *event_label,
> +static inline int ima_measure_critical_data(const char *event_label,
>   					     const char *event_name,
>   					     const void *buf, size_t buf_len,
> -					     bool hash) {}
> +					     bool hash)
> +{
> +	return -ENOENT;
> +}
>   
>   #endif /* CONFIG_IMA */
>   
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index f0e448ed1f9f..03db221324c3 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -264,11 +264,11 @@ 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(struct user_namespace *mnt_userns,
> -				struct inode *inode, const void *buf, int size,
> -				const char *eventname, enum ima_hooks func,
> -				int pcr, const char *func_data,
> -				bool buf_hash);
> +int process_buffer_measurement(struct user_namespace *mnt_userns,
> +			       struct inode *inode, const void *buf, int size,
> +			       const char *eventname, enum ima_hooks func,
> +			       int pcr, const char *func_data,
> +			       bool buf_hash);
>   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_appraise.c b/security/integrity/ima/ima_appraise.c
> index ef9dcfce45d4..275a2377743f 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -345,6 +345,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint,
>   	enum hash_algo hash_algo;
>   	const u8 *digest = NULL;
>   	u32 digestsize = 0;
> +	int process_rc __maybe_unused;
>   	int rc = 0;
>   
>   	if (!(iint->flags & IMA_CHECK_BLACKLIST))
> @@ -355,7 +356,8 @@ int ima_check_blacklist(struct integrity_iint_cache *iint,
>   
>   		rc = is_binary_blacklisted(digest, digestsize);
>   		if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
> -			process_buffer_measurement(&init_user_ns, NULL, digest, digestsize,
> +			process_rc = process_buffer_measurement(&init_user_ns,
I think there is no need to make this change now. If and when 
ima_check_blacklist() needs to look at the return value of p_b_m(), this 
change can be made.

> +						   NULL, digest, digestsize,
>   						   "blacklisted-hash", NONE,
>   						   pcr, NULL, false);
>   	}
> diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
> index c985418698a4..910367cdd920 100644
> --- a/security/integrity/ima/ima_asymmetric_keys.c
> +++ b/security/integrity/ima/ima_asymmetric_keys.c
> @@ -31,6 +31,7 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
>   				   unsigned long flags, bool create)
>   {
>   	bool queued = false;
> +	int ret __maybe_unused;
>   
>   	/* Only asymmetric keys are handled by this hook. */
>   	if (key->type != &key_type_asymmetric)
> @@ -60,7 +61,8 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
>   	 * if the IMA policy is configured to measure a key linked
>   	 * to the given keyring.
>   	 */
> -	process_buffer_measurement(&init_user_ns, NULL, payload, payload_len,
> +	ret = process_buffer_measurement(&init_user_ns, NULL,
> +				   payload, payload_len,
Same comment as in ima_check_blacklist() - this change be made when needed.

>   				   keyring->description, KEY_CHECK, 0,
>   				   keyring->description, false);
>   }
> diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
> index 5076a7d9d23e..6790eea88db8 100644
> --- a/security/integrity/ima/ima_init.c
> +++ b/security/integrity/ima/ima_init.c
> @@ -118,6 +118,7 @@ void __init ima_load_x509(void)
>   
>   int __init ima_init(void)
>   {
> +	int measure_rc __maybe_unused;
>   	int rc;
>   
>   	ima_tpm_chip = tpm_default_chip();
> @@ -153,8 +154,9 @@ int __init ima_init(void)
>   
>   	ima_init_key_queue();
>   
> -	ima_measure_critical_data("kernel_info", "kernel_version",
> -				  UTS_RELEASE, strlen(UTS_RELEASE), false);
> +	measure_rc = ima_measure_critical_data("kernel_info", "kernel_version",
> +					       UTS_RELEASE, strlen(UTS_RELEASE),
> +					       false);
Same comment as in ima_check_blacklist() - this change be made when needed.

>   
>   	return rc;
>   }
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 8ef1fa357e0c..3386e7436440 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -827,7 +827,7 @@ int ima_post_load_data(char *buf, loff_t size,
>   	return 0;
>   }
>   
> -/*
> +/**
>    * process_buffer_measurement - Measure the buffer or the buffer data hash
>    * @mnt_userns:	user namespace of the mount the inode was found from
>    * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
> @@ -840,12 +840,15 @@ int ima_post_load_data(char *buf, loff_t size,
>    * @buf_hash: measure buffer data hash
>    *
>    * Based on policy, either the buffer data or buffer data hash is measured
> + *
> + * Return: 0 if the buffer has been successfully measured, a negative value
> + * otherwise.
>    */
> -void process_buffer_measurement(struct user_namespace *mnt_userns,
> -				struct inode *inode, const void *buf, int size,
> -				const char *eventname, enum ima_hooks func,
> -				int pcr, const char *func_data,
> -				bool buf_hash)
> +int process_buffer_measurement(struct user_namespace *mnt_userns,
> +			       struct inode *inode, const void *buf, int size,
> +			       const char *eventname, enum ima_hooks func,
> +			       int pcr, const char *func_data,
> +			       bool buf_hash)
>   {
>   	int ret = 0;
>   	const char *audit_cause = "ENOMEM";
> @@ -867,7 +870,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns,
>   	u32 secid;
>   
>   	if (!ima_policy_flag)
> -		return;
> +		return -ENOENT;
>   
>   	template = ima_template_desc_buf();
>   	if (!template) {
> @@ -889,7 +892,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns,
>   					secid, 0, func, &pcr, &template,
>   					func_data);
>   		if (!(action & IMA_MEASURE))
> -			return;
> +			return -ENOENT;
>   	}
>   
>   	if (!pcr)
> @@ -937,7 +940,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns,
>   					func_measure_str(func),
>   					audit_cause, ret, 0, ret);
>   
> -	return;
> +	return ret;
>   }
>   
>   /**
> @@ -951,6 +954,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns,
>   void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
>   {
>   	struct fd f;
> +	int ret __maybe_unused;
>   
>   	if (!buf || !size)
>   		return;
> @@ -959,9 +963,10 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
>   	if (!f.file)
>   		return;
>   
> -	process_buffer_measurement(file_mnt_user_ns(f.file), file_inode(f.file),
> -				   buf, size, "kexec-cmdline", KEXEC_CMDLINE, 0,
> -				   NULL, false);
> +	ret = process_buffer_measurement(file_mnt_user_ns(f.file),
> +					 file_inode(f.file), buf, size,
> +					 "kexec-cmdline", KEXEC_CMDLINE, 0,
> +					 NULL, false);
Since the return value of p_b_m() is not used here, this change can be 
made when needed.

>   	fdput(f);
>   }
>   
> @@ -977,18 +982,21 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
>    * and extend the pcr.  Examples of critical data could be various data
>    * structures, policies, and states stored in kernel memory that can
>    * impact the integrity of the system.
> + *
> + * Return: 0 if the buffer has been successfully measured, a negative value
> + * otherwise.
>    */
> -void ima_measure_critical_data(const char *event_label,
> -			       const char *event_name,
> -			       const void *buf, size_t buf_len,
> -			       bool hash)
> +int ima_measure_critical_data(const char *event_label,
> +			      const char *event_name,
> +			      const void *buf, size_t buf_len,
> +			      bool hash)
>   {
>   	if (!event_name || !event_label || !buf || !buf_len)
> -		return;
> +		return -ENOPARAM;
>   
> -	process_buffer_measurement(&init_user_ns, NULL, buf, buf_len, event_name,
> -				   CRITICAL_DATA, 0, event_label,
> -				   hash);
> +	return process_buffer_measurement(&init_user_ns, NULL, buf, buf_len,
> +					  event_name, CRITICAL_DATA, 0,
> +					  event_label, hash);
>   }
>   
>   static int __init init_ima(void)
> diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
> index 979ef6c71f3d..e3047ce64f39 100644
> --- a/security/integrity/ima/ima_queue_keys.c
> +++ b/security/integrity/ima/ima_queue_keys.c
> @@ -134,6 +134,7 @@ void ima_process_queued_keys(void)
>   {
>   	struct ima_key_entry *entry, *tmp;
>   	bool process = false;
> +	int ret __maybe_unused;
>   
>   	if (ima_process_keys)
>   		return;
> @@ -159,13 +160,13 @@ void ima_process_queued_keys(void)
>   
>   	list_for_each_entry_safe(entry, tmp, &ima_keys, list) {
>   		if (!timer_expired)
> -			process_buffer_measurement(&init_user_ns, NULL,
> -						   entry->payload,
> -						   entry->payload_len,
> -						   entry->keyring_name,
> -						   KEY_CHECK, 0,
> -						   entry->keyring_name,
> -						   false);
> +			ret = process_buffer_measurement(&init_user_ns, NULL,
> +							 entry->payload,
> +							 entry->payload_len,
> +							 entry->keyring_name,
> +							 KEY_CHECK, 0,
> +							 entry->keyring_name,
> +							 false);
Same comment as above.

>   		list_del(&entry->list);
>   		ima_free_key_entry(entry);
>   	}
> diff --git a/security/selinux/ima.c b/security/selinux/ima.c
> index 34d421861bfc..4db9fa211638 100644
> --- a/security/selinux/ima.c
> +++ b/security/selinux/ima.c
> @@ -75,6 +75,7 @@ void selinux_ima_measure_state_locked(struct selinux_state *state)
>   	char *state_str = NULL;
>   	void *policy = NULL;
>   	size_t policy_len;
> +	int measure_rc __maybe_unused;
>   	int rc = 0;
>   
>   	WARN_ON(!mutex_is_locked(&state->policy_mutex));
> @@ -85,8 +86,9 @@ void selinux_ima_measure_state_locked(struct selinux_state *state)
>   		return;
>   	}
>   
> -	ima_measure_critical_data("selinux", "selinux-state",
> -				  state_str, strlen(state_str), false);
> +	measure_rc = ima_measure_critical_data("selinux", "selinux-state",
> +					       state_str, strlen(state_str),
> +					       false);
Since the return value of ima_measure_critical_data() is not used here, 
this change can be made when needed.

>   
>   	kfree(state_str);
>   
> @@ -102,8 +104,8 @@ void selinux_ima_measure_state_locked(struct selinux_state *state)
>   		return;
>   	}
>   
> -	ima_measure_critical_data("selinux", "selinux-policy-hash",
> -				  policy, policy_len, true);
> +	measure_rc = ima_measure_critical_data("selinux", "selinux-policy-hash",
> +					       policy, policy_len, true);
Same comment as above.

  -lakshmi

>   
>   	vfree(policy);
>   }
> 

  reply	other threads:[~2021-07-01 16:13 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-01 12:55 [PATCH v2 0/3] ima: Provide more info about buffer measurement Roberto Sassu
2021-07-01 12:55 ` [PATCH v2 1/3] ima: Introduce ima_get_current_hash_algo() Roberto Sassu
2021-07-01 16:01   ` Lakshmi Ramasubramanian
2021-07-01 12:55 ` [PATCH v2 2/3] ima: Return int in the functions to measure a buffer Roberto Sassu
2021-07-01 16:15   ` Lakshmi Ramasubramanian [this message]
2021-07-02 10:51     ` Roberto Sassu
2021-07-01 12:55 ` [PATCH v2 3/3] ima: Add digest and digest_len params to " Roberto Sassu
2021-07-01 17:27   ` Lakshmi Ramasubramanian
2021-07-02 10:54     ` Roberto Sassu

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