linux-kernel - Re: [PATCH v2] ima: instantiate the bprm_creds_for

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Message-ID: <c1c61f20-a4ee-437f-840b-2433345e74b6@linux.ibm.com>
Date: Wed, 4 Dec 2024 14:01:02 -0500
From: Stefan Berger <stefanb@...ux.ibm.com>
To: Mimi Zohar <zohar@...ux.ibm.com>, linux-integrity@...r.kernel.org
Cc: Mickaël Salaün <mic@...ikod.net>,
        roberto.sassu@...wei.com, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jeff Xu <jeffxu@...omium.org>,
        Kees Cook <kees@...nel.org>, Paul Moore <paul@...l-moore.com>,
        audit@...r.kernel.org
Subject: Re: [PATCH v2] ima: instantiate the bprm_creds_for_exec() hook

On 12/3/24 6:34 PM, Mimi Zohar wrote:
> Like direct file execution (e.g. ./script.sh), indirect file exection

typo: execution

> (e.g. sh script.sh) needs to be measured and appraised.  Instantiate

If I understand the underlying patches correctly then 'sh script.sh' 
would be evaluated with execveat(AT_CHECK) but this requires the execute 
flag to be set. To maintain backwards compatibility  sh cannot assume 
that script.sh has the execute flag set since it doesn't need today:

$ echo 'echo hi' > foo.sh
$ sh foo.sh
hi

the same is true for python:

$ echo 'print("hi")' > foo.py
$ python foo.py
hi

I am not sure which interpreters are going to be able to take advantage 
of this or whether they will behave differently if the x bit is set 
versus when it is not set...?