[PATCH v12 19/26] ima: Namespace audit status flags

Stefan Berger
2022-04-20T14:09:36Z

From: Mehmet Kayaalp <mkayaalp@linux.vnet.ibm.com>

The iint cache stores whether the file is measured, appraised, audited
etc. This patch moves the IMA_AUDIT and IMA_AUDITED flags into the
per-namespace ns_status, enabling IMA audit mechanism to audit the same
file each time it is accessed in a new namespace.

Read and write operations on the iint flags is replaced with function
calls. For reading, iint_flags() returns the bitwise OR of iint->flags
and ns_status->flags. The ns_status flags are masked with
IMA_NS_STATUS_FLAGS (currently only IMA_AUDIT & IMA_AUDITED) while the
iint flags are masked with ~IMA_NS_STATUS_FLAGS. Similarly,
set_iint_flags() writes the one masked portion to the ns_status flags,
while the iint flags receive the remaining flags. The ns_status
parameter added to ima_audit_measurement() is used with the above
functions to query and set the ns_status flags.

Replace all occurrences where the IMA_AUDITED flag is set with the
iint_flags() and set_iint_flags() operations so that the splitting
and merging of the flags works properly. Whenever the IMA_AUDITED flag is
tested, use iint_flags() to receive the merged version of the flags.

Since IMA_AUDITED is also part of the IMA_DONE_MASK, use the new
functions wherever the IMA_DONE_MASK is involved.

Move the IMA_AUDIT flag also into the ns_status flags since this flag
is dependent on policy rules that may be different per namespace.

Signed-off-by: Mehmet Kayaalp <mkayaalp@linux.vnet.ibm.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>

---
v9:
- Use ns_status also in non-namespaced case and use same flag splitting
for namespaced and non-namespaced case, thus use one implementation
for iint_flags() and set_iint_flags()
- Merge-in patch 'Enable re-auditing of modified files'
- Use one implementation of mask_iint_ns_status_flags() for namespaced
and non-namespaced case
- Added IMA_AUDIT to IMA_NS_STATUS_FLAGS since it's a per namespace flag
---
security/integrity/ima/ima.h | 40 ++++++++++++++++++++--
security/integrity/ima/ima_api.c | 8 +++--
security/integrity/ima/ima_main.c | 56 ++++++++++++++++++++++++++-----
security/integrity/integrity.h | 3 ++
4 files changed, 94 insertions(+), 13 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 7a08fdce7ebc..b7e1f4b5eb30 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -314,7 +314,8 @@ int process_buffer_measurement(struct ima_namespace *ns,
int pcr, const char *func_data,
bool buf_hash, u8 *digest, size_t digest_len);
void ima_audit_measurement(struct integrity_iint_cache *iint,
- const unsigned char *filename);
+ const unsigned char *filename,
+ struct ns_status *ns_status);
int ima_alloc_init_template(struct ima_event_data *event_data,
struct ima_template_entry **entry,
struct ima_template_desc *template_desc);
@@ -497,6 +498,34 @@ static inline int ima_filter_rule_match(u32 secid, u32 field, u32 op,
#define POLICY_FILE_FLAGS S_IWUSR
#endif /* CONFIG_IMA_READ_POLICY */

+#define IMA_NS_STATUS_ACTIONS IMA_AUDIT
+#define IMA_NS_STATUS_FLAGS (IMA_AUDIT | IMA_AUDITED)
+
+static inline unsigned long iint_flags(struct integrity_iint_cache *iint,
+ struct ns_status *ns_status)
+{
+ if (!ns_status)
+ return iint->flags;
+
+ return (iint->flags & ~IMA_NS_STATUS_FLAGS) |
+ (ns_status->flags & IMA_NS_STATUS_FLAGS);
+}
+
+static inline unsigned long set_iint_flags(struct integrity_iint_cache *iint,
+ struct ns_status *ns_status,
+ unsigned long flags)
+{
+ unsigned long ns_status_flags = flags & IMA_NS_STATUS_FLAGS;
+
+ WARN_ON(!ns_status && ns_status_flags);
+
+ iint->flags = flags & ~IMA_NS_STATUS_FLAGS;
+ if (ns_status)
+ ns_status->flags = ns_status_flags;
+
+ return flags;
+}
+
static inline
struct user_namespace *ima_user_ns_from_file(const struct file *filp)
{
@@ -534,7 +563,14 @@ static inline struct ns_status *ima_get_ns_status
struct inode *inode,
struct integrity_iint_cache *iint)
{
- return NULL;
+ struct ns_status *ns_status = &iint->ns_status;
+
+ if (list_empty(&iint->ns_list)) {
+ ns_status_init(ns_status);
+ list_add(&ns_status->ns_next, &iint->ns_list);
+ }
+
+ return ns_status;
}

#endif /* CONFIG_IMA_NS */
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 1b6c3e6174cd..d179cb41b8c8 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -346,14 +346,16 @@ void ima_store_measurement(struct ima_namespace *ns,
}

void ima_audit_measurement(struct integrity_iint_cache *iint,
- const unsigned char *filename)
+ const unsigned char *filename,
+ struct ns_status *ns_status)
{
struct audit_buffer *ab;
char *hash;
const char *algo_name = hash_algo_name[iint->ima_hash->algo];
int i;
+ unsigned long flags = iint_flags(iint, ns_status);

- if (iint->flags & IMA_AUDITED)
+ if (flags & IMA_AUDITED)
return;

hash = kzalloc((iint->ima_hash->length * 2) + 1, GFP_KERNEL);
@@ -376,7 +378,7 @@ void ima_audit_measurement(struct integrity_iint_cache *iint,
audit_log_task_info(ab);
audit_log_end(ab);

- iint->flags |= IMA_AUDITED;
+ set_iint_flags(iint, ns_status, flags | IMA_AUDITED);
out:
kfree(hash);
return;
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 17eb2971eb36..26faf9f75645 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -149,6 +149,31 @@ static void ima_rdwr_violation_check(struct ima_namespace *ns,
"invalid_pcr", "open_writers");
}

+static void mask_iint_ns_status_flags(struct integrity_iint_cache *iint,
+ unsigned long mask)
+{
+ struct ns_status *ns_status;
+ unsigned long flags;
+
+ read_lock(&iint->ns_list_lock);
+ if (list_empty(&iint->ns_list)) {
+ /*
+ * An empty list is possible due to __process_measurement only
+ * creating ns_status for IMA_NS_STATUS_ACTIONS.
+ * No ns_status being used implies that for example IMA_AUDIT
+ * was never used and thus IMA_AUDITED cannot have been set.
+ */
+ flags = iint_flags(iint, NULL) & mask;
+ set_iint_flags(iint, NULL, flags);
+ } else {
+ list_for_each_entry(ns_status, &iint->ns_list, ns_next) {
+ flags = iint_flags(iint, ns_status) & mask;
+ set_iint_flags(iint, ns_status, flags);
+ }
+ }
+ read_unlock(&iint->ns_list_lock);
+}
+
static void ima_check_last_writer(struct integrity_iint_cache *iint,
struct inode *inode, struct file *file)
{
@@ -165,8 +190,11 @@ static void ima_check_last_writer(struct integrity_iint_cache *iint,
if (!IS_I_VERSION(inode) ||
!inode_eq_iversion(inode, iint->version) ||
(iint->flags & IMA_NEW_FILE)) {
- iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
+ mask_iint_ns_status_flags
+ (iint,
+ ~(IMA_DONE_MASK | IMA_NEW_FILE));
iint->measured_pcrs = 0;
+
if (update)
ima_update_xattr(iint, file);
}
@@ -203,6 +231,7 @@ static int __process_measurement(struct ima_namespace *ns,
{
struct inode *inode = file_inode(file);
struct integrity_iint_cache *iint = NULL;
+ struct ns_status *ns_status = NULL;
struct ima_template_desc *template_desc = NULL;
char *pathbuf = NULL;
char filename[NAME_MAX];
@@ -215,6 +244,7 @@ static int __process_measurement(struct ima_namespace *ns,
bool violation_check;
enum hash_algo hash_algo;
unsigned int allowed_algos = 0;
+ unsigned long flags;

if (!ns->ima_policy_flag || !S_ISREG(inode->i_mode))
return 0;
@@ -243,6 +273,14 @@ static int __process_measurement(struct ima_namespace *ns,
iint = integrity_inode_get(inode);
if (!iint)
rc = -ENOMEM;
+
+ if (!rc && (action & IMA_NS_STATUS_ACTIONS)) {
+ ns_status = ima_get_ns_status(ns, inode, iint);
+ if (IS_ERR(ns_status)) {
+ rc = PTR_ERR(ns_status);
+ ns_status = NULL;
+ }
+ }
}

if (!rc && violation_check)
@@ -258,11 +296,13 @@ static int __process_measurement(struct ima_namespace *ns,

mutex_lock(&iint->mutex);

+ flags = iint_flags(iint, ns_status);
+
if (test_and_clear_bit(IMA_CHANGE_ATTR, &iint->atomic_flags))
/* reset appraisal flags if ima_inode_post_setattr was called */
- iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
- IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
- IMA_NONACTION_FLAGS);
+ flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
+ IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
+ IMA_NONACTION_FLAGS);

/*
* Re-evaulate the file if either the xattr has changed or the
@@ -273,7 +313,7 @@ static int __process_measurement(struct ima_namespace *ns,
((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
!(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) &&
!(action & IMA_FAIL_UNVERIFIABLE_SIGS))) {
- iint->flags &= ~IMA_DONE_MASK;
+ flags &= ~IMA_DONE_MASK;
iint->measured_pcrs = 0;
}

@@ -281,9 +321,9 @@ static int __process_measurement(struct ima_namespace *ns,
* (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
* IMA_AUDIT, IMA_AUDITED)
*/
- iint->flags |= action;
+ flags = set_iint_flags(iint, ns_status, flags | action);
action &= IMA_DO_MASK;
- action &= ~((iint->flags & (IMA_DONE_MASK ^ IMA_MEASURED)) >> 1);
+ action &= ~((flags & (IMA_DONE_MASK ^ IMA_MEASURED)) >> 1);

/* If target pcr is already measured, unset IMA_MEASURE action */
if ((action & IMA_MEASURE) && (iint->measured_pcrs & (0x1 << pcr)))
@@ -358,7 +398,7 @@ static int __process_measurement(struct ima_namespace *ns,
&pathname, filename);
}
if (action & IMA_AUDIT)
- ima_audit_measurement(iint, pathname);
+ ima_audit_measurement(iint, pathname, ns_status);

if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO))
rc = 0;
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index ae0da8f1ba7e..33084ab2addd 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -181,6 +181,9 @@ struct integrity_iint_cache {
*/
rwlock_t ns_list_lock;
struct list_head ns_list;
+#ifndef CONFIG_IMA_NS
+ struct ns_status ns_status;
+#endif
};

/* rbtree tree calls to lookup, insert, delete
--
2.34.1