Re: [PATCH 1/2] kexec, KEYS: make the code in bzImage64_verify_sig public

[Coiby Xu <coiby.xu@gmail.com>]

Hi Dave,

On Thu, Sep 30, 2021 at 08:49:02PM +0800, Dave Young wrote:
>Hi Coiby,
>On 09/27/21 at 08:50am, Coiby Xu wrote:
>> From: Coiby Xu <coxu@redhat.com>
>>
>> The code in bzImage64_verify_sig could make use of system keyrings including
>> .buitin_trusted_keys, .secondary_trusted_keys and .platform keyring to verify
>> signed kernel image as PE file. Move it to a public function.
>>
>> Signed-off-by: Coiby Xu <coiby.xu@gmail.com>
>> ---
>>  arch/x86/kernel/kexec-bzimage64.c | 13 +------------
>>  include/linux/kexec.h             |  3 +++
>>  kernel/kexec_file.c               | 15 +++++++++++++++
>>  3 files changed, 19 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
>> index 170d0fd68b1f..4136dd3be5a9 100644
>> --- a/arch/x86/kernel/kexec-bzimage64.c
>> +++ b/arch/x86/kernel/kexec-bzimage64.c
>> @@ -17,7 +17,6 @@
>>  #include <linux/kernel.h>
>>  #include <linux/mm.h>
>>  #include <linux/efi.h>
>> -#include <linux/verification.h>
>>
>>  #include <asm/bootparam.h>
>>  #include <asm/setup.h>
>> @@ -531,17 +530,7 @@ static int bzImage64_cleanup(void *loader_data)
>>  #ifdef CONFIG_KEXEC_BZIMAGE_VERIFY_SIG
>>  static int bzImage64_verify_sig(const char *kernel, unsigned long kernel_len)
>>  {
>> -	int ret;
>> -
>> -	ret = verify_pefile_signature(kernel, kernel_len,
>> -				      VERIFY_USE_SECONDARY_KEYRING,
>> -				      VERIFYING_KEXEC_PE_SIGNATURE);
>> -	if (ret == -ENOKEY && IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING)) {
>> -		ret = verify_pefile_signature(kernel, kernel_len,
>> -					      VERIFY_USE_PLATFORM_KEYRING,
>> -					      VERIFYING_KEXEC_PE_SIGNATURE);
>> -	}
>> -	return ret;
>> +	return arch_kexec_kernel_verify_pe_sig(kernel, kernel_len);
>>  }
>>  #endif
>>
>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
>> index 0c994ae37729..d45f32336dbe 100644
>> --- a/include/linux/kexec.h
>> +++ b/include/linux/kexec.h
>> @@ -19,6 +19,7 @@
>>  #include <asm/io.h>
>>
>>  #include <uapi/linux/kexec.h>
>> +#include <linux/verification.h>
>>
>>  #ifdef CONFIG_KEXEC_CORE
>>  #include <linux/list.h>
>> @@ -199,6 +200,8 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image);
>>  #ifdef CONFIG_KEXEC_SIG
>>  int arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
>>  				 unsigned long buf_len);
>> +int arch_kexec_kernel_verify_pe_sig(const char *kernel,
>> +				    unsigned long kernel_len);
>>  #endif
>>  int arch_kexec_locate_mem_hole(struct kexec_buf *kbuf);
>>
>> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
>> index 33400ff051a8..85ed6984ad8f 100644
>> --- a/kernel/kexec_file.c
>> +++ b/kernel/kexec_file.c
>> @@ -106,6 +106,21 @@ int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
>>  {
>>  	return kexec_image_verify_sig_default(image, buf, buf_len);
>>  }
>> +
>> +int arch_kexec_kernel_verify_pe_sig(const char *kernel, unsigned long kernel_len)
>> +{
>> +	int ret;
>> +
>> +	ret = verify_pefile_signature(kernel, kernel_len,
>> +				      VERIFY_USE_SECONDARY_KEYRING,
>> +				      VERIFYING_KEXEC_PE_SIGNATURE);
>> +	if (ret == -ENOKEY && IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING)) {
>> +		ret = verify_pefile_signature(kernel, kernel_len,
>> +					      VERIFY_USE_PLATFORM_KEYRING,
>> +					      VERIFYING_KEXEC_PE_SIGNATURE);
>> +	}
>> +	return ret;
>> +}
>
>Since the function is moved as generic code, the kconfig option
>CONFIG_KEXEC_BZIMAGE_VERIFY_SIG can be removed.

>
>Instead a CONFIG_KEXEC_PEFILE_VERIFY_SIG can be added so that it does
>not need to be compiled for only platform which support UEFI pefile
>signature verification.  And the related arch kexec_file kconfig can
>just select it.


Thanks for the suggestion! I notice KEXEC_BZIMAGE_VERIFY_SIG depends 
on SIGNED_PE_FILE_VERIFICATION and selects SYSTEM_TRUSTED_KEYRING. So 
maybe SIGNED_PE_FILE_VERIFICATION could do the job of 
CONFIG_KEXEC_PEFILE_VERIFY_SIG. And arch/arm64/Kconfig also have 
KEXEC_IMAGE_VERIFY_SIG. So maybe it's better we don't keep
CONFIG_KEXEC_BZIMAGE_VERIFY_SIG.

>
>Coiby, can you try above?
>
>>  #endif
>>
>>  /*
>> --
>> 2.33.0
>>
>>
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>>
>>
>
>Thanks
>Dave
>

-- 
Best regards,
Coiby