[PATCH v2 2/2] IMA: Add audit log for failure conditions

Lakshmi Ramasubramanian
2020-06-13T02:26:49Z

process_buffer_measurement() and ima_alloc_key_entry() functions need to
log an audit message for auditing integrity measurement failures.

Add audit message in these two functions. Remove "pr_devel" log message
in process_buffer_measurement().

Sample audit messages:

[ 6.415374] audit: type=1804 audit(1592005945.627:2): pid=1 uid=0 auid=4294967295 ses=4294967295 subj=kernel op=measuring_kexec_cmdline cause=alloc_entry comm="swapper/0" name="kexec-cmdline" res=0 result=-12

[ 8.085456] audit: type=1802 audit(1592005947.297:9): pid=1 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:init_t:s0 op=policy_update cause=completed comm="systemd" res=1 result=0

[ 8.128004] audit: type=1804 audit(1592005947.341:11): pid=1 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:init_t:s0 op=measuring_key cause=hashing_error comm="systemd" name=".builtin_trusted_keys" res=0 result=-22

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
---
security/integrity/ima/ima.h | 48 ++++++++++++++++---------
security/integrity/ima/ima_main.c | 18 +++++++---
security/integrity/ima/ima_policy.c | 2 +-
security/integrity/ima/ima_queue_keys.c | 5 +++
4 files changed, 51 insertions(+), 22 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index df93ac258e01..c3a32e181b48 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -186,27 +186,43 @@ static inline unsigned int ima_hash_key(u8 *digest)
return (digest[0] | digest[1] << 8) % IMA_MEASURE_HTABLE_SIZE;
}

-#define __ima_hooks(hook) \
- hook(NONE) \
- hook(FILE_CHECK) \
- hook(MMAP_CHECK) \
- hook(BPRM_CHECK) \
- hook(CREDS_CHECK) \
- hook(POST_SETATTR) \
- hook(MODULE_CHECK) \
- hook(FIRMWARE_CHECK) \
- hook(KEXEC_KERNEL_CHECK) \
- hook(KEXEC_INITRAMFS_CHECK) \
- hook(POLICY_CHECK) \
- hook(KEXEC_CMDLINE) \
- hook(KEY_CHECK) \
- hook(MAX_CHECK)
-#define __ima_hook_enumify(ENUM) ENUM,
+#define __ima_hooks(hook) \
+ hook(NONE, none) \
+ hook(FILE_CHECK, file) \
+ hook(MMAP_CHECK, mmap) \
+ hook(BPRM_CHECK, bprm) \
+ hook(CREDS_CHECK, creds) \
+ hook(POST_SETATTR, post_setattr) \
+ hook(MODULE_CHECK, module) \
+ hook(FIRMWARE_CHECK, firmware) \
+ hook(KEXEC_KERNEL_CHECK, kexec_kernel) \
+ hook(KEXEC_INITRAMFS_CHECK, kexec_initramfs) \
+ hook(POLICY_CHECK, policy) \
+ hook(KEXEC_CMDLINE, kexec_cmdline) \
+ hook(KEY_CHECK, key) \
+ hook(MAX_CHECK, none)
+
+#define __ima_hook_enumify(ENUM, str) ENUM,
+#define __ima_stringify(arg) (#arg)
+#define __ima_hook_measuring_stringify(ENUM, str) \
+ (__ima_stringify(measuring_ ##str)),

enum ima_hooks {
__ima_hooks(__ima_hook_enumify)
};

+static const char * const ima_hooks_measure_str[] = {
+ __ima_hooks(__ima_hook_measuring_stringify)
+};
+
+static inline const char *func_measure_str(enum ima_hooks func)
+{
+ if (func >= MAX_CHECK)
+ return ima_hooks_measure_str[NONE];
+
+ return ima_hooks_measure_str[func];
+}
+
extern const char *const func_tokens[];

struct modsig;
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index c1583d98c5e5..8a001aa8e592 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -740,6 +740,7 @@ void process_buffer_measurement(const void *buf, int size,
int pcr, const char *keyring)
{
int ret = 0;
+ const char *audit_cause = "ENOMEM";
struct ima_template_entry *entry = NULL;
struct integrity_iint_cache iint = {};
struct ima_event_data event_data = {.iint = &iint,
@@ -794,21 +795,28 @@ void process_buffer_measurement(const void *buf, int size,
iint.ima_hash->length = hash_digest_size[ima_hash_algo];

ret = ima_calc_buffer_hash(buf, size, iint.ima_hash);
- if (ret < 0)
+ if (ret < 0) {
+ audit_cause = "hashing_error";
goto out;
+ }

ret = ima_alloc_init_template(&event_data, &entry, template);
- if (ret < 0)
+ if (ret < 0) {
+ audit_cause = "alloc_entry";
goto out;
+ }

ret = ima_store_template(entry, violation, NULL, buf, pcr);
-
- if (ret < 0)
+ if (ret < 0) {
+ audit_cause = "store_entry";
ima_free_template_entry(entry);
+ }

out:
if (ret < 0)
- pr_devel("%s: failed, result: %d\n", __func__, ret);
+ integrity_audit_msg(AUDIT_INTEGRITY_PCR, NULL, eventname,
+ func_measure_str(func),
+ audit_cause, ret, 0);

return;
}
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index e493063a3c34..66aa3e17a888 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -1414,7 +1414,7 @@ void ima_delete_rules(void)
}
}

-#define __ima_hook_stringify(str) (#str),
+#define __ima_hook_stringify(func, str) (#func),

const char *const func_tokens[] = {
__ima_hooks(__ima_hook_stringify)
diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
index cb3e3f501593..631fd7ab2dcd 100644
--- a/security/integrity/ima/ima_queue_keys.c
+++ b/security/integrity/ima/ima_queue_keys.c
@@ -68,6 +68,7 @@ static struct ima_key_entry *ima_alloc_key_entry(struct key *keyring,
size_t payload_len)
{
int rc = 0;
+ const char *audit_cause = "ENOMEM";
struct ima_key_entry *entry;

entry = kzalloc(sizeof(*entry), GFP_KERNEL);
@@ -88,6 +89,10 @@ static struct ima_key_entry *ima_alloc_key_entry(struct key *keyring,

out:
if (rc) {
+ integrity_audit_msg(AUDIT_INTEGRITY_PCR, NULL,
+ keyring->description,
+ func_measure_str(KEY_CHECK),
+ audit_cause, rc, 0);
ima_free_key_entry(entry);
entry = NULL;
}
--
2.27.0