[PATCH] ipe: allow secondary and platform keyrings to install/update policies

[luca.boccassi@gmail.com]

From: Luca Boccassi <bluca@debian.org>

The current policy management makes it impossible to use IPE
in a general purpose distribution. In such cases the users are not
building the kernel, the distribution is, and access to the private
key included in the trusted keyring is, for obvious reason, not
available.
This means that users have no way to enable IPE, since there will
be no built-in generic policy, and no access to the key to sign
updates validated by the trusted keyring.

Just as we do for dm-verity, kernel modules and more, allow the
secondary and platform keyrings to also validate policies. This
allows users enrolling their own keys in UEFI db or MOK to also
sign policies, and enroll them. This makes it sensible to enable
IPE in general purpose distributions, as it becomes usable by
any user wishing to do so. Keys in these keyrings can already
load kernels and kernel modules, so there is no security
downgrade.

Signed-off-by: Luca Boccassi <bluca@debian.org>
---
 security/ipe/policy.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/security/ipe/policy.c b/security/ipe/policy.c
index d8e7db857a2e..cac304dc86c2 100644
--- a/security/ipe/policy.c
+++ b/security/ipe/policy.c
@@ -169,9 +169,15 @@ struct ipe_policy *ipe_new_policy(const char *text, size_t textlen,
 			goto err;
 		}
 
-		rc = verify_pkcs7_signature(NULL, 0, new->pkcs7, pkcs7len, NULL,
+		rc = verify_pkcs7_signature(NULL, 0, new->pkcs7, pkcs7len,
+					    VERIFY_USE_SECONDARY_KEYRING,
 					    VERIFYING_UNSPECIFIED_SIGNATURE,
 					    set_pkcs7_data, new);
+		if (rc == -ENOKEY)
+			rc = verify_pkcs7_signature(NULL, 0, new->pkcs7, pkcs7len,
+						    VERIFY_USE_PLATFORM_KEYRING,
+						    VERIFYING_UNSPECIFIED_SIGNATURE,
+						    set_pkcs7_data, new);
 		if (rc)
 			goto err;
 	} else {
-- 
2.39.2