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

Roberto Sassu
2021-07-02T10:52:03Z

> From: Lakshmi Ramasubramanian [mailto:nramas@linux.microsoft.com]
> 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@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.

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);
> > }
> >