[PATCH 4.9 89/92] ima: always measure and audit files in policy

Greg Kroah-Hartman
2018-11-29T14:24:01Z

From: Mimi Zohar <zohar@linux.vnet.ibm.com>

commit f3cc6b25dcc5616f0d5c720009b2ac66f97df2ff upstream.

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.

Note:
In general, adding, deleting or in anyway changing which files are
included in the IMA measurement list is not a good idea, as it might
result in not being able to unseal trusted keys sealed to a specific
TPM PCR value. This patch not only adds file measurements that were
not previously measured, but specifies that the file hash value for
these files will be 0's.

As the IMA measurement list ordering is not consistent from one boot
to the next, it is unlikely that anyone is sealing keys based on the
IMA measurement list. Remote attestation servers should be able to
process these new measurement records, but might complain about
these unknown records.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Reviewed-by: Dmitry Kasatkin <dmitry.kasatkin@huawei.com>
Cc: Aditya Kali <adityakali@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
security/integrity/ima/ima_api.c | 69 ++++++++++++++++++++++--------------
security/integrity/ima/ima_crypto.c | 10 +++++
security/integrity/ima/ima_main.c | 9 ++--
3 files changed, 57 insertions(+), 31 deletions(-)

--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -198,42 +198,59 @@ int ima_collect_measurement(struct integ
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;
- }
-
- 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;
- }
+ /*
+ * 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;
+
+ /* 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)
+ iint->flags |= IMA_COLLECTED;
out:
- if (result)
+ if (result) {
+ if (file->f_flags & O_DIRECT)
+ audit_cause = "failed(directio)";
+
integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
filename, "collect_data", audit_cause,
result, 0);
+ }
return result;
}

@@ -277,7 +294,7 @@ void ima_store_measurement(struct integr
}

result = ima_store_template(entry, violation, inode, filename, pcr);
- if (!result || result == -EEXIST) {
+ if ((!result || result == -EEXIST) && !(file->f_flags & O_DIRECT)) {
iint->flags |= IMA_MEASURED;
iint->measured_pcrs |= (0x1 << pcr);
}
--- a/security/integrity/ima/ima_crypto.c
+++ b/security/integrity/ima/ima_crypto.c
@@ -443,6 +443,16 @@ int ima_calc_file_hash(struct file *file
loff_t i_size;
int rc;

+ /*
+ * For consistency, fail file's opened with the O_DIRECT flag on
+ * filesystems mounted with/without DAX option.
+ */
+ if (file->f_flags & O_DIRECT) {
+ hash->length = hash_digest_size[ima_hash_algo];
+ hash->algo = ima_hash_algo;
+ return -EINVAL;
+ }
+
i_size = i_size_read(file_inode(file));

if (ima_ahash_minsize && i_size >= ima_ahash_minsize) {
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -242,11 +242,8 @@ static int process_measurement(struct fi
hash_algo = ima_get_hash_algo(xattr_value, xattr_len);

rc = ima_collect_measurement(iint, file, buf, size, hash_algo);
- if (rc != 0) {
- if (file->f_flags & O_DIRECT)
- rc = (iint->flags & IMA_PERMIT_DIRECTIO) ? 0 : -EACCES;
+ if (rc != 0 && rc != -EBADF && rc != -EINVAL)
goto out_digsig;
- }

if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */
pathname = ima_d_path(&file->f_path, &pathbuf, filename);
@@ -254,12 +251,14 @@ static int process_measurement(struct fi
if (action & IMA_MEASURE)
ima_store_measurement(iint, file, pathname,
xattr_value, xattr_len, pcr);
- if (action & IMA_APPRAISE_SUBMASK)
+ if (rc == 0 && (action & IMA_APPRAISE_SUBMASK))
rc = ima_appraise_measurement(func, iint, file, pathname,
xattr_value, xattr_len, opened);
if (action & IMA_AUDIT)
ima_audit_measurement(iint, pathname);

+ if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO))
+ rc = 0;
out_digsig:
if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG) &&
!(iint->flags & IMA_NEW_FILE))