[PATCH v6 3/6] ima: always measure and audit files in policy

On Tue, 2017-08-22 at 13:05 +0300, Dmitry Kasatkin wrote:

On Tue, Aug 15, 2017 at 5:43 PM, Mimi Zohar [off-list ref] wrote:

quoted

All files matching a "measure" rule must be included in the IMA
measurement list, even when the file hash cannot be calculated.
Similarly, all files matching an "audit" rule must be audited, even when
the file hash can not be calculated.

The file data hash field contained in the IMA measurement list template
data will contain 0's instead of the actual file hash digest.

Signed-off-by: Mimi Zohar <redacted>

---
Changelog v6:
- replace "?:" with if/then
- annotate i_version usage
- reword O_DIRECT comment

Changelog v5:
- Fail files opened O_DIRECT, but include attempt in measurement list.

Changelog v4:
- Based on both -EBADF and -EINVAL
- clean up ima_collect_measurement()

 security/integrity/ima/ima_api.c    | 67 +++++++++++++++++++++++--------------
 security/integrity/ima/ima_crypto.c | 10 ++++++
 security/integrity/ima/ima_main.c   |  7 ++--
 3 files changed, 54 insertions(+), 30 deletions(-)

diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index c2edba8de35e..1dee695642a4 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c

@@ -199,42 +199,59 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
        struct inode *inode = file_inode(file);
        const char *filename = file->f_path.dentry->d_name.name;
        int result = 0;
+       int length;
+       void *tmpbuf;
+       u64 i_version;
        struct {
                struct ima_digest_data hdr;
                char digest[IMA_MAX_DIGEST_SIZE];
        } hash;

-       if (!(iint->flags & IMA_COLLECTED)) {
-               u64 i_version = file_inode(file)->i_version;
+       if (iint->flags & IMA_COLLECTED)
+               goto out;

-               if (file->f_flags & O_DIRECT) {
-                       audit_cause = "failed(directio)";
-                       result = -EACCES;
-                       goto out;
-               }
+       /*
+        * Dectecting file change is based on i_version. On filesystems
+        * which do not support i_version, support is limited to an initial
+        * measurement/appraisal/audit.
+        */
+       i_version = file_inode(file)->i_version;
+       hash.hdr.algo = algo;

-               hash.hdr.algo = algo;
-
-               result = (!buf) ?  ima_calc_file_hash(file, &hash.hdr) :
-                       ima_calc_buffer_hash(buf, size, &hash.hdr);
-               if (!result) {
-                       int length = sizeof(hash.hdr) + hash.hdr.length;
-                       void *tmpbuf = krealloc(iint->ima_hash, length,
-                                               GFP_NOFS);
-                       if (tmpbuf) {
-                               iint->ima_hash = tmpbuf;
-                               memcpy(iint->ima_hash, &hash, length);
-                               iint->version = i_version;
-                               iint->flags |= IMA_COLLECTED;
-                       } else
-                               result = -ENOMEM;
-               }
+       /* Initialize hash digest to 0's in case of failure */
+       memset(&hash.digest, 0, sizeof(hash.digest));
+
+       if (buf)
+               result = ima_calc_buffer_hash(buf, size, &hash.hdr);
+       else
+               result = ima_calc_file_hash(file, &hash.hdr);
+
+       if (result && result != -EBADF && result != -EINVAL)
+               goto out;
+
+       length = sizeof(hash.hdr) + hash.hdr.length;
+       tmpbuf = krealloc(iint->ima_hash, length, GFP_NOFS);
+       if (!tmpbuf) {
+               result = -ENOMEM;
+               goto out;
        }
+
+       iint->ima_hash = tmpbuf;
+       memcpy(iint->ima_hash, &hash, length);
+       iint->version = i_version;
+
+       /* Possibly temporary failure due to type of read (eg. O_DIRECT) */
+       if (result != -EBADF && result != -EINVAL)
+               iint->flags |= IMA_COLLECTED;

Result can be other than 0, EBADF and EINVAL here?
It is confusing.. simpler than can be just

if (!result)
 iint->flags |= IMA_COLLECTED;

Isn't it?

Yes, that is better.

Mimi

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