[PATCH 3.16 005/134] ima: accept previously set IMA_NEW_FILE

Ben Hutchings
2017-08-18T13:15:41Z

From: Daniel Glöckner <dg@emlix.com>

commit 1ac202e978e18f045006d75bd549612620c6ec3a upstream.

Modifying the attributes of a file makes ima_inode_post_setattr reset
the IMA cache flags. So if the file, which has just been created,
is opened a second time before the first file descriptor is closed,
verification fails since the security.ima xattr has not been written
yet. We therefore have to look at the IMA_NEW_FILE even if the file
already existed.

With this patch there should no longer be an error when cat tries to
open testfile:

$ rm -f testfile
$ ( echo test >&3 ; touch testfile ; cat testfile ) 3>testfile

A file being new is no reason to accept that it is missing a digital
signature demanded by the policy.

Signed-off-by: Daniel Glöckner <dg@emlix.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
security/integrity/ima/ima_appraise.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -195,10 +195,11 @@ int ima_appraise_measurement(int func, s

cause = "missing-hash";
status = INTEGRITY_NOLABEL;
- if (opened & FILE_CREATED) {
+ if (opened & FILE_CREATED)
iint->flags |= IMA_NEW_FILE;
+ if ((iint->flags & IMA_NEW_FILE) &&
+ !(iint->flags & IMA_DIGSIG_REQUIRED))
status = INTEGRITY_PASS;
- }
goto out;
}