linux-kernel - Re: [PATCH v3 2/3] ima: enable signing of modules with build time generated key

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Message-ID: <c0df8b07-79de-80cb-9eaa-ed70fbf8414b@linux.ibm.com>
Date:   Fri, 2 Apr 2021 07:27:18 -0400
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Nayna Jain <nayna@...ux.ibm.com>, linux-integrity@...r.kernel.org,
        keyrings@...r.kernel.org
Cc:     linux-security-module@...r.kernel.org,
        David Howells <dhowells@...hat.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH v3 2/3] ima: enable signing of modules with build time
 generated key


On 3/30/21 9:16 AM, Nayna Jain wrote:
> The kernel build process currently only signs kernel modules when
> MODULE_SIG is enabled. Also, sign the kernel modules at build time when
> IMA_APPRAISE_MODSIG is enabled.
>
> Signed-off-by: Nayna Jain <nayna@...ux.ibm.com>
Acked-by: Stefan Berger <stefanb@...ux.ibm.com>
> ---
>   certs/Kconfig  | 2 +-
>   certs/Makefile | 8 ++++++++
>   init/Kconfig   | 6 +++---
>   3 files changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/certs/Kconfig b/certs/Kconfig
> index c94e93d8bccf..48675ad319db 100644
> --- a/certs/Kconfig
> +++ b/certs/Kconfig
> @@ -4,7 +4,7 @@ menu "Certificates for signature checking"
>   config MODULE_SIG_KEY
>   	string "File name or PKCS#11 URI of module signing key"
>   	default "certs/signing_key.pem"
> -	depends on MODULE_SIG
> +	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
>   	help
>            Provide the file name of a private key/certificate in PEM format,
>            or a PKCS#11 URI according to RFC7512. The file should contain, or
> diff --git a/certs/Makefile b/certs/Makefile
> index f4c25b67aad9..e3185c57fbd8 100644
> --- a/certs/Makefile
> +++ b/certs/Makefile
> @@ -32,6 +32,14 @@ endif # CONFIG_SYSTEM_TRUSTED_KEYRING
>   clean-files := x509_certificate_list .x509.list
>   
>   ifeq ($(CONFIG_MODULE_SIG),y)
> +	SIGN_KEY = y
> +endif
> +
> +ifeq ($(CONFIG_IMA_APPRAISE_MODSIG),y)
> +	SIGN_KEY = y
> +endif
> +
> +ifdef SIGN_KEY
>   ###############################################################################
>   #
>   # If module signing is requested, say by allyesconfig, but a key has not been
> diff --git a/init/Kconfig b/init/Kconfig
> index 5f5c776ef192..85e48a578f90 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -2164,7 +2164,7 @@ config MODULE_SIG_FORCE
>   config MODULE_SIG_ALL
>   	bool "Automatically sign all modules"
>   	default y
> -	depends on MODULE_SIG
> +	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
>   	help
>   	  Sign all modules during make modules_install. Without this option,
>   	  modules must be signed manually, using the scripts/sign-file tool.
> @@ -2174,7 +2174,7 @@ comment "Do not forget to sign required modules with scripts/sign-file"
>   
>   choice
>   	prompt "Which hash algorithm should modules be signed with?"
> -	depends on MODULE_SIG
> +	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
>   	help
>   	  This determines which sort of hashing algorithm will be used during
>   	  signature generation.  This algorithm _must_ be built into the kernel
> @@ -2206,7 +2206,7 @@ endchoice
>   
>   config MODULE_SIG_HASH
>   	string
> -	depends on MODULE_SIG
> +	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
>   	default "sha1" if MODULE_SIG_SHA1
>   	default "sha224" if MODULE_SIG_SHA224
>   	default "sha256" if MODULE_SIG_SHA256