Currently, IMA adds a measurement entry and an audit log even if access
to the file will be denied when appraisal is in enforce mode. This gives
the false indication to a verifier analyzing the data that file access
occurred. It also has the undesirable effect of unnecessarily revoking
access to TPM-protected objects sealed to PCRs.
Given that a potentially corrupted file will not be accessed by any user
space process, it is safe for the purpose of integrity evaluation to avoid
to record a measurement or audit log in this case.
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
security/integrity/ima/ima_main.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 9ef748ea829f..0faddcb8c71a 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -328,16 +328,14 @@ static int process_measurement(struct file *file, const struct cred *cred,
hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
rc = ima_collect_measurement(iint, file, buf, size, hash_algo, modsig);
- if (rc != 0 && rc != -EBADF && rc != -EINVAL)
+ if (rc != 0 && rc != -EBADF && rc != -EINVAL) {
+ action &= ~(IMA_MEASURE | IMA_AUDIT);
goto out_locked;
+ }
if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */
pathname = ima_d_path(&file->f_path, &pathbuf, filename);
- if (action & IMA_MEASURE)
- ima_store_measurement(iint, file, pathname,
- xattr_value, xattr_len, modsig, pcr,
- template_desc);
if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
rc = ima_check_blacklist(iint, modsig, pcr);
if (rc != -EPERM) {
@@ -351,15 +349,21 @@ static int process_measurement(struct file *file, const struct cred *cred,
rc = mmap_violation_check(func, file, &pathbuf,
&pathname, filename);
}
- if (action & IMA_AUDIT)
- ima_audit_measurement(iint, pathname);
-
if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO))
rc = 0;
out_locked:
if ((mask & MAY_WRITE) && test_bit(IMA_DIGSIG, &iint->atomic_flags) &&
!(iint->flags & IMA_NEW_FILE))
rc = -EACCES;
+ if (must_appraise)
+ if (rc && (ima_appraise & IMA_APPRAISE_ENFORCE))
+ action &= ~(IMA_MEASURE | IMA_AUDIT);
+ if (action & IMA_MEASURE)
+ ima_store_measurement(iint, file, pathname,
+ xattr_value, xattr_len, modsig, pcr,
+ template_desc);
+ if (action & IMA_AUDIT)
+ ima_audit_measurement(iint, pathname);
mutex_unlock(&iint->mutex);
kfree(xattr_value);
ima_free_modsig(modsig);
--
2.26.2
