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").
thanks,
Mimi
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.
--
Best
GUO Zihua
---
Documentation/admin-guide/kernel-parameters.txt | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f5a27f067db9..1b5aa6ca65f8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1843,6 +1843,10 @@
The list of supported hash algorithms is defined
in crypto/hash_info.h.
+ This parameter must be specified after ima_template=,
+ as it would set the default template and that cannot be
+ changed by ima_template= afterwards.
+
ima_policy= [IMA]
The builtin policies to load during IMA setup.
Format: "tcb | appraise_tcb | secure_boot |
@@ -1879,6 +1883,9 @@
Formats: { "ima" | "ima-ng" | "ima-sig" }
Default: "ima-ng"
+ This parameter must be specified before ima_hash=.
+ Please refer to ima_hash= for further explanation.
+
ima_template_fmt=
[IMA] Define a custom template format.
Format: { "field1|...|fieldN" }
.
