Re: [PATCH v5 2/2] kexec, KEYS: Make use of platform keyring for signature verify

[Mimi Zohar <zohar@linux.ibm.com>]

On Mon, 2019-01-21 at 17:59 +0800, Kairui Song wrote:
> This patch let kexec_file_load makes use of .platform keyring as fall
> back if it failed to verify a PE signed image against secondary or
> builtin key ring, make it possible to verify kernel image signed with
> preboot keys as well.
> 
> This commit adds a VERIFY_USE_PLATFORM_KEYRING similar to previous
> VERIFY_USE_SECONDARY_KEYRING indicating that verify_pkcs7_signature
> should verify the signature using platform keyring. Also, decrease
> the error message log level when verification failed with -ENOKEY,
> so that if called tried multiple time with different keyring it
> won't generate extra noises.
> 
> Signed-off-by: Kairui Song <kasong@redhat.com>

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

> ---
>  arch/x86/kernel/kexec-bzimage64.c | 13 ++++++++++---
>  certs/system_keyring.c            | 13 ++++++++++++-
>  include/linux/verification.h      |  1 +
>  3 files changed, 23 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
> index 7d97e432cbbc..2c007abd3d40 100644
> --- a/arch/x86/kernel/kexec-bzimage64.c
> +++ b/arch/x86/kernel/kexec-bzimage64.c
> @@ -534,9 +534,16 @@ 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)
>  {
> -	return verify_pefile_signature(kernel, kernel_len,
> -				       VERIFY_USE_SECONDARY_KEYRING,
> -				       VERIFYING_KEXEC_PE_SIGNATURE);
> +	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;
>  }
>  #endif
>  
> diff --git a/certs/system_keyring.c b/certs/system_keyring.c
> index 4690ef9cda8a..7085c286f4bd 100644
> --- a/certs/system_keyring.c
> +++ b/certs/system_keyring.c
> @@ -240,11 +240,22 @@ int verify_pkcs7_signature(const void *data, size_t len,
>  #else
>  		trusted_keys = builtin_trusted_keys;
>  #endif
> +	} else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
> +#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
> +		trusted_keys = platform_trusted_keys;
> +#else
> +		trusted_keys = NULL;
> +#endif
> +		if (!trusted_keys) {
> +			ret = -ENOKEY;
> +			pr_devel("PKCS#7 platform keyring is not available\n");
> +			goto error;
> +		}
>  	}
>  	ret = pkcs7_validate_trust(pkcs7, trusted_keys);
>  	if (ret < 0) {
>  		if (ret == -ENOKEY)
> -			pr_err("PKCS#7 signature not signed with a trusted key\n");
> +			pr_devel("PKCS#7 signature not signed with a trusted key\n");
>  		goto error;
>  	}
>  
> diff --git a/include/linux/verification.h b/include/linux/verification.h
> index cfa4730d607a..018fb5f13d44 100644
> --- a/include/linux/verification.h
> +++ b/include/linux/verification.h
> @@ -17,6 +17,7 @@
>   * should be used.
>   */
>  #define VERIFY_USE_SECONDARY_KEYRING ((struct key *)1UL)
> +#define VERIFY_USE_PLATFORM_KEYRING  ((struct key *)2UL)
>  
>  /*
>   * The use to which an asymmetric key is being put.