linux-kernel - Re: [PATCH v11 9/9] ima: measure kexec load and exec events as critical data

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <59ba139f5454f00cd25e3b802780a5cae0e51978.camel@linux.ibm.com>
Date: Tue, 08 Apr 2025 12:31:22 -0400
From: Mimi Zohar <zohar@...ux.ibm.com>
To: steven chen <chenste@...ux.microsoft.com>, stefanb@...ux.ibm.com,
        roberto.sassu@...weicloud.com, roberto.sassu@...wei.com,
        eric.snowberg@...cle.com, ebiederm@...ssion.com, paul@...l-moore.com,
        code@...icks.com, bauermann@...abnow.com,
        linux-integrity@...r.kernel.org, kexec@...ts.infradead.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: madvenka@...ux.microsoft.com, nramas@...ux.microsoft.com,
        James.Bottomley@...senPartnership.com, bhe@...hat.com,
        vgoyal@...hat.com, dyoung@...hat.com
Subject: Re: [PATCH v11 9/9] ima: measure kexec load and exec events as
 critical data

On Wed, 2025-04-02 at 05:47 -0700, steven chen wrote:
> The amount of memory allocated at kexec load, even with the extra memory
> allocated, might not be large enough for the entire measurement list.  The
> indeterminate interval between kexec 'load' and 'execute' could exacerbate
> this problem.
> 
> Define two new IMA events, 'kexec_load' and 'kexec_execute', to be 
> measured as critical data at kexec 'load' and 'execute' respectively.
> Report the allocated kexec segment size, IMA binary log size and the
> runtime measurements count as part of those events.
> 
> These events, and the values reported through them, serve as markers in
> the IMA log to verify the IMA events are captured during kexec soft
> reboot.  The presence of a 'kexec_load' event in between the last two
> 'boot_aggregate' events in the IMA log implies this is a kexec soft
> reboot, and not a cold-boot. And the absence of 'kexec_execute' event
> after kexec soft reboot implies missing events in that window which
> results in inconsistency with TPM PCR quotes, necessitating a cold boot
> for a successful remote attestation.
> 
> These critical data events are displayed as hex encoded ascii in the
> ascii_runtime_measurement_list.  Verifying the critical data hash requires 
> calculating the hash of the decoded ascii string.  
> 
> For example, to verify the 'kexec_load' data hash:
> 
> sudo cat /sys/kernel/security/integrity/ima/ascii_runtime_measurements 
> > grep  kexec_load | cut -d' ' -f 6 | xxd -r -p | sha256sum
> 
> 
> To verify the 'kexec_execute' data hash:
> 
> sudo cat /sys/kernel/security/integrity/ima/ascii_runtime_measurements 
> > grep kexec_execute | cut -d' ' -f 6 | xxd -r -p | sha256sum
> 
> Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
> Signed-off-by: steven chen <chenste@...ux.microsoft.com>
> Reviewed-by: Stefan Berger <stefanb@...ux.ibm.com>

Thanks, Steven. 

Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>