IMA: Define a new template field buf

A buffer(kexec boot command line arguments) measured into IMA
measuremnt list cannot be appraised, without already being
aware of the buffer contents. Since hashes are non-reversible,
raw buffer is needed for validation or regenerating hash for
appraisal/attestation.

Add support to store/read the buffer contents in HEX.
The kexec cmdline hash is stored in the "d-ng" field of the
template data.  It can be verified using
sudo cat /sys/kernel/security/integrity/ima/ascii_runtime_measurements |
  grep  kexec-cmdline | cut -d' ' -f 6 | xxd -r -p | sha256sum

- Add two new fields to ima_event_data to hold the buf and
buf_len
- Add a new template field 'buf' to be used to store/read
the buffer data.
- Updated process_buffer_meaurement to add the buffer to
ima_event_data. process_buffer_measurement added in
"Define a new IMA hook to measure the boot command line
 arguments"
- Add a new template policy name ima-buf to represent
'd-ng|n-ng|buf'

Signed-off-by: Prakhar Srivastava <prsriva02@gmail.com>
Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/Documentation/security/IMA-templates.rst b/Documentation/security/IMA-templates.rst
index 2cd0e273cc9a..3d1cca287aa4 100644
--- a/Documentation/security/IMA-templates.rst
+++ b/Documentation/security/IMA-templates.rst
@@ -69,15 +69,16 @@ descriptors by adding their identifier to the format string
    algorithm (field format: [<hash algo>:]digest, where the digest
    prefix is shown only if the hash algorithm is not SHA1 or MD5);
  - 'n-ng': the name of the event, without size limitations;
- - 'sig': the file signature.
+ - 'sig': the file signature;
+ - 'buf': the buffer data that was used to generate the hash without size limitations;
 
 
 Below, there is the list of defined template descriptors:
 
  - "ima": its format is ``d|n``;
  - "ima-ng" (default): its format is ``d-ng|n-ng``;
- - "ima-sig": its format is ``d-ng|n-ng|sig``.
-
+ - "ima-sig": its format is ``d-ng|n-ng|sig``;
+ - "ima-buf": its format is ``d-ng|n-ng|buf``;
 
 
 Use