Re: [PATCH v10 01/12] MODSIGN: Export module signature definitions

Mimi Zohar
2019-05-09T15:42:46Z

On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
> IMA will use the module_signature format for append signatures, so export
> the relevant definitions and factor out the code which verifies that the
> appended signature trailer is valid.
>
> Also, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it
> and be able to use mod_check_sig() without having to depend on either
> CONFIG_MODULE_SIG or CONFIG_MODULES.
>
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> Cc: Jessica Yu <jeyu@kernel.org>

Just a couple minor questions/comments below.

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

> ---

< snip >

> diff --git a/init/Kconfig b/init/Kconfig
> index 4592bf7997c0..a71019553ee1 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1906,7 +1906,7 @@ config MODULE_SRCVERSION_ALL
> config MODULE_SIG
> bool "Module signature verification"
> depends on MODULES
> - select SYSTEM_DATA_VERIFICATION
> + select MODULE_SIG_FORMAT
> help
> Check modules for valid signatures upon load: the signature
> is simply appended to the module. For more information see
> @@ -2036,6 +2036,10 @@ config TRIM_UNUSED_KSYMS
>
> endif # MODULES
>
> +config MODULE_SIG_FORMAT
> + def_bool n
> + select SYSTEM_DATA_VERIFICATION

Normally Kconfigs, in the same file, are defined before they are used.
I'm not sure if that is required or just a convention.

> config MODULES_TREE_LOOKUP
> def_bool y
> depends on PERF_EVENTS || TRACING
> diff --git a/kernel/Makefile b/kernel/Makefile
> index 6c57e78817da..d2f2488f80ab 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -57,6 +57,7 @@ endif
> obj-$(CONFIG_UID16) += uid16.o
> obj-$(CONFIG_MODULES) += module.o
> obj-$(CONFIG_MODULE_SIG) += module_signing.o
> +obj-$(CONFIG_MODULE_SIG_FORMAT) += module_signature.o
> obj-$(CONFIG_KALLSYMS) += kallsyms.o
> obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
> obj-$(CONFIG_CRASH_CORE) += crash_core.o
> diff --git a/kernel/module.c b/kernel/module.c
> index 985caa467aef..326ddeb364dd 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -19,6 +19,7 @@
> #include <linux/export.h>
> #include <linux/extable.h>
> #include <linux/moduleloader.h>
> +#include <linux/module_signature.h>
> #include <linux/trace_events.h>
> #include <linux/init.h>
> #include <linux/kallsyms.h>
> diff --git a/kernel/module_signature.c b/kernel/module_signature.c
> new file mode 100644
> index 000000000000..6d5e59f27f55
> --- /dev/null
> +++ b/kernel/module_signature.c
> @@ -0,0 +1,45 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Module signature checker
> + *
> + * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
> + * Written by David Howells (dhowells@redhat.com)
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/printk.h>
> +#include <linux/module_signature.h>
> +#include <asm/byteorder.h>
> +
> +/**
> + * mod_check_sig - check that the given signature is sane
> + *
> + * @ms: Signature to check.
> + * @file_len: Size of the file to which @ms is appended.

"name" is missing.

Mimi

> + */