Re: [PATCH v2] KEYS: Make use of platform keyring for module signature verify

Hi,

On Thu, Apr 25, 2019 at 07:55:50AM -0400, Mimi Zohar wrote:

On Wed, 2019-04-24 at 14:33 +0000, Robert Holmes wrote:

...

This patch completes commit 278311e417be ("kexec, KEYS: Make use of platform keyring for signature verify") which, while adding the platform keyring for bzImage verification, neglected to also add this keyring for module verification.

As such, kernel modules signed with keys from the MokList variable were not successfully verified.

Using the platform keyring keys for verifying kernel modules was not neglected, but rather intentional.  This patch description should clearly explain the reason for needing to verify kernel module signatures based on the pre-boot keys.  (Hint: verifying kernel modules based on the pre-boot keys was previously rejected.)

So the background for this patch is that Fedora, which carries the lockdown patch set, recently regressed[0] with respect to user-signed modules. Previously, we carried a patch that added all the pre-boot keys to the secondary keyring. That way users could add a machine owner key and use secure boot and lockdown with their self-signed 3rd party modules.

Since the pre-boot keys are now loaded into the platform keyring, I suggested that Robert submit the patch upstream, but since the lockdown patches aren't upstream perhaps it doesn't make much sense to pick this up and Fedora should continue carrying it.

[0] https://bugzilla.redhat.com/show_bug.cgi?id=1701096

Regards, Jeremy

...

Signed-off-by: Robert Holmes robeholmes@gmail.com Cc: linux-integrity@vger.kernel.org Cc: keyrings@vger.kernel.org Cc: stable@vger.kernel.org

---

kernel/module_signing.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/kernel/module_signing.c b/kernel/module_signing.c index 6b9a926fd86b..cf94220e9154 100644 --- a/kernel/module_signing.c +++ b/kernel/module_signing.c @@ -49,6 +49,7 @@ int mod_verify_sig(const void *mod, struct load_info *info) { struct module_signature ms; size_t sig_len, modlen = info->len;

• int ret;

  pr_devel("==>%s(,%zu)\n", __func__, modlen);

@@ -82,8 +83,15 @@ int mod_verify_sig(const void *mod, struct load_info *info) return -EBADMSG; }

• return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,

• 		      VERIFY_USE_SECONDARY_KEYRING,
  

• 		      VERIFYING_MODULE_SIGNATURE,
  

• 		      NULL, NULL);
  

• ret = verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,

• 		     VERIFY_USE_SECONDARY_KEYRING,
  

• 		     VERIFYING_MODULE_SIGNATURE,
  

• 		     NULL, NULL);
  

• if (ret == -ENOKEY && IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING)) {

• ret = verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
  

• 			     VERIFY_USE_PLATFORM_KEYRING,
  

• 			     VERIFYING_MODULE_SIGNATURE,
  

• 			     NULL, NULL);
  

• }
• return ret;

}