On 2022/1/26 12:37, Mimi Zohar wrote:
On Wed, 2022-01-26 at 10:28 +0800, Guozihua (Scott) wrote:
On 2022/1/26 9:07, Mimi Zohar wrote:
On Tue, 2022-01-25 at 17:02 +0800, GUO Zihua wrote:
From: Guo Zihua <guozihua@xxxxxxxxxx>
Commandline parameter ima_hash= and ima_template= has order requirement
for them to work correctly together. Namely ima_hash= must be
specified after ima_template=, otherwise ima_template= will be ignored.
The reason is that when handling ima_hash=, ima template would be set to
the default value if it has not been initialized already, and that value
cannot be changed afterwards by ima_template=.
This patch adds this limitation to the documentation.
Reviewed-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
Signed-off-by: Guo Zihua <guozihua@xxxxxxxxxx>
This issue should be limited to the original "ima" template format,
which only supports hash algorithms of 20 bytes or less. The "ima_ng"
template has been the default since larger digests and templates were
upstreamed back in Linux 3.13[1]. Do you really still have kernels
built with the original "ima" template?
[1] Refer to commit 4286587dccd4 ("ima: add Kconfig default measurement
list template").
Hi Mimi,
The issue is that if ima_hash is specified before ima_template,
ima_template will not work. Built-in default only affects which template
will be loaded eventually.
For example, if the built-in default template is ima-ng and user would
like to change it to ima-sig with sha512 by specifying "ima_hash=sha512
ima_template=ima-sig" in command line, the result will be ima-ng with
sha512, not ima-sig with sha512.
Ok. Once the template name is set, ima_template_setup() doesn't allow
it to be reset. This was probably done to set the template name to the
first occurance of "ima_template=" on the boot command line. This
concern could be addressed by defining a static local variable in
ima_template_setup().
So either documenting the ordering requirement, as you've done, or
allowing the template_name to be reset are fine.
thanks,
Mimi
.
The main issue lies in ima_template_desc_current called by hash_setup,
which does not just read ima_template global variable, but also tries to
set it if that hasn't been done already. Causing ima_template_setup to quit.
--
Best
GUO Zihua
