From: Paul Menzel <pmenzel@molgen.mpg.de>
To: Michal Suchanek <msuchanek@suse.de>,
keyrings@vger.kernel.org, linux-crypto@vger.kernel.org,
linux-integrity@vger.kernel.org
Cc: kexec@lists.infradead.org, Philipp Rudo <prudo@redhat.com>,
Mimi Zohar <zohar@linux.ibm.com>,
Nayna <nayna@linux.vnet.ibm.com>, Rob Herring <robh@kernel.org>,
linux-s390@vger.kernel.org, Vasily Gorbik <gor@linux.ibm.com>,
Lakshmi Ramasubramanian <nramas@linux.microsoft.com>,
Heiko Carstens <hca@linux.ibm.com>, Jessica Yu <jeyu@kernel.org>,
linux-kernel@vger.kernel.org, David Howells <dhowells@redhat.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Luis Chamberlain <mcgrof@kernel.org>,
Paul Mackerras <paulus@samba.org>,
Hari Bathini <hbathini@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
linuxppc-dev@lists.ozlabs.org,
Frank van der Linden <fllinden@amazon.com>,
Thiago Jung Bauermann <bauerman@linux.ibm.com>,
Daniel Axtens <dja@axtens.net>,
buendgen@de.ibm.com, Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
"David S. Miller" <davem@davemloft.net>,
Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
Sven Schnelle <svens@linux.ibm.com>, Baoquan He <bhe@redhat.com>,
linux-security-module@vger.kernel.org
Subject: Re: [PATCH v5 2/6] powerpc/kexec_file: Add KEXEC_SIG support.
Date: Wed, 9 Feb 2022 07:44:15 +0100 [thread overview]
Message-ID: <b56fe3a2-b145-9d4e-acf2-4991204b3102@molgen.mpg.de> (raw)
In-Reply-To: <d95f7c6865bcad5ee37dcbec240e79aa742f5e1d.1641900831.git.msuchanek@suse.de>
Dear Michal,
Thank you for the patch.
Am 11.01.22 um 12:37 schrieb Michal Suchanek:
Could you please remove the dot/period at the end of the git commit
message summary?
> Copy the code from s390x
>
> Both powerpc and s390x use appended signature format (as opposed to EFI
> based patforms using PE format).
patforms → platforms
How can this be tested?
> Signed-off-by: Michal Suchanek <msuchanek@suse.de>
> ---
> v3: - Philipp Rudo <prudo@redhat.com>: Update the comit message with
> explanation why the s390 code is usable on powerpc.
> - Include correct header for mod_check_sig
> - Nayna <nayna@linux.vnet.ibm.com>: Mention additional IMA features
> in kconfig text
> ---
> arch/powerpc/Kconfig | 16 ++++++++++++++++
> arch/powerpc/kexec/elf_64.c | 36 ++++++++++++++++++++++++++++++++++++
> 2 files changed, 52 insertions(+)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index dea74d7717c0..1cde9b6c5987 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -560,6 +560,22 @@ config KEXEC_FILE
> config ARCH_HAS_KEXEC_PURGATORY
> def_bool KEXEC_FILE
>
> +config KEXEC_SIG
> + bool "Verify kernel signature during kexec_file_load() syscall"
> + depends on KEXEC_FILE && MODULE_SIG_FORMAT
> + help
> + This option makes kernel signature verification mandatory for
> + the kexec_file_load() syscall.
> +
> + In addition to that option, you need to enable signature
> + verification for the corresponding kernel image type being
> + loaded in order for this to work.
> +
> + Note: on powerpc IMA_ARCH_POLICY also implements kexec'ed kernel
> + verification. In addition IMA adds kernel hashes to the measurement
> + list, extends IMA PCR in the TPM, and implements kernel image
> + blacklist by hash.
So, what is the takeaway for the user? IMA_ARCH_POLICY is preferred?
What is the disadvantage, and two implementations(?) needed then? More
overhead?
> +
> config RELOCATABLE
> bool "Build a relocatable kernel"
> depends on PPC64 || (FLATMEM && (44x || FSL_BOOKE))
> diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
> index eeb258002d1e..98d1cb5135b4 100644
> --- a/arch/powerpc/kexec/elf_64.c
> +++ b/arch/powerpc/kexec/elf_64.c
> @@ -23,6 +23,7 @@
> #include <linux/of_fdt.h>
> #include <linux/slab.h>
> #include <linux/types.h>
> +#include <linux/module_signature.h>
>
> static void *elf64_load(struct kimage *image, char *kernel_buf,
> unsigned long kernel_len, char *initrd,
> @@ -151,7 +152,42 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
> return ret ? ERR_PTR(ret) : NULL;
> }
>
> +#ifdef CONFIG_KEXEC_SIG
> +int elf64_verify_sig(const char *kernel, unsigned long kernel_len)
> +{
> + const unsigned long marker_len = sizeof(MODULE_SIG_STRING) - 1;
> + struct module_signature *ms;
> + unsigned long sig_len;
Use size_t to match the signature of `verify_pkcs7_signature()`?
> + int ret;
> +
> + if (marker_len > kernel_len)
> + return -EKEYREJECTED;
> +
> + if (memcmp(kernel + kernel_len - marker_len, MODULE_SIG_STRING,
> + marker_len))
> + return -EKEYREJECTED;
> + kernel_len -= marker_len;
> +
> + ms = (void *)kernel + kernel_len - sizeof(*ms);
> + ret = mod_check_sig(ms, kernel_len, "kexec");
> + if (ret)
> + return ret;
> +
> + sig_len = be32_to_cpu(ms->sig_len);
> + kernel_len -= sizeof(*ms) + sig_len;
> +
> + return verify_pkcs7_signature(kernel, kernel_len,
> + kernel + kernel_len, sig_len,
> + VERIFY_USE_PLATFORM_KEYRING,
> + VERIFYING_MODULE_SIGNATURE,
> + NULL, NULL);
> +}
> +#endif /* CONFIG_KEXEC_SIG */
> +
> const struct kexec_file_ops kexec_elf64_ops = {
> .probe = kexec_elf_probe,
> .load = elf64_load,
> +#ifdef CONFIG_KEXEC_SIG
> + .verify_sig = elf64_verify_sig,
> +#endif
> };
Kind regards,
Paul
next prev parent reply other threads:[~2022-02-09 6:44 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-11 11:37 [PATCH v5 0/6] KEXEC_SIG with appended signature Michal Suchanek
2022-01-11 11:37 ` [PATCH v5 1/6] s390/kexec_file: Don't opencode appended signature check Michal Suchanek
2022-01-11 11:37 ` [PATCH v5 2/6] powerpc/kexec_file: Add KEXEC_SIG support Michal Suchanek
2022-02-09 4:43 ` Michael Ellerman
2022-02-09 6:44 ` Paul Menzel [this message]
2022-02-09 12:01 ` Michal Suchánek
2022-02-11 15:31 ` Paul Menzel
2022-02-13 17:50 ` Mimi Zohar
2022-02-14 2:59 ` Mimi Zohar
2022-02-14 15:14 ` Mimi Zohar
2022-02-14 15:55 ` Michal Suchánek
2022-02-14 17:09 ` Mimi Zohar
2022-01-11 11:37 ` [PATCH v5 3/6] kexec_file: Don't opencode appended signature verification Michal Suchanek
2022-01-25 20:15 ` Luis Chamberlain
2022-02-03 10:49 ` Michal Suchánek
2022-01-11 11:37 ` [PATCH v5 4/6] module: strip the signature marker in the verification function Michal Suchanek
2022-01-25 20:23 ` Luis Chamberlain
2022-01-11 11:37 ` [PATCH v5 5/6] module: Use key_being_used_for for log messages in verify_appended_signature Michal Suchanek
2022-01-25 20:24 ` Luis Chamberlain
2022-01-11 11:37 ` [PATCH v5 6/6] module: Move duplicate mod_check_sig users code to mod_parse_sig Michal Suchanek
2022-01-25 20:27 ` Luis Chamberlain
2022-01-25 20:30 ` [PATCH v5 0/6] KEXEC_SIG with appended signature Luis Chamberlain
2022-02-09 4:46 ` Michael Ellerman
2022-02-10 23:30 ` Luis Chamberlain
2022-02-13 18:53 ` Mimi Zohar
2022-02-13 20:27 ` Mimi Zohar
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