RE: [PATCH v2 2/3] ima: Return int in the functions to measure a buffer

[Roberto Sassu]

> From: Lakshmi Ramasubramanian [mailto:nramas@xxxxxxxxxxxxxxxxxxx]
> Sent: Thursday, July 1, 2021 6:16 PM
> 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@xxxxxxxxxx>
> > ---
> >   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.

Hi Lakshmi

ok. I was worried about possible warnings. If it is not an issue,
I will remove the assignment.

Thanks

Roberto

HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Li Peng, Li Jian, Shi Yanli

> > +						   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);
> >   }
> >