[RFC PATCH 1/3] keys: Add ability to trust the platform keyring

[Eric Snowberg]

Add the ability to allow the secondary_trusted keyring to trust
keys in the platform keyring. This is done by doing a key_link
of the platform_trusted_keys to the secondary_trusted_keys.
After they are linked, the platform_trusted_keys can be used for
validation instead of the secondary_trusted_keys if the user
chooses. This functionality will be used in a follow on patch.

Signed-off-by: Eric Snowberg <eric.snowberg@xxxxxxxxxx>
---
 certs/system_keyring.c        | 19 ++++++++++++++++++-
 include/keys/system_keyring.h | 10 ++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index 4b693da488f1..471eb13e3cca 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -23,6 +23,7 @@ static struct key *secondary_trusted_keys;
 #endif
 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 static struct key *platform_trusted_keys;
+bool  secondary_trusts_platform;
 #endif
 
 extern __initconst const u8 system_certificate_list[];
@@ -67,6 +68,10 @@ int restrict_link_by_builtin_and_secondary_trusted(
 		/* Allow the builtin keyring to be added to the secondary */
 		return 0;
 
+	if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && secondary_trusts_platform)
+		return restrict_link_by_signature(dest_keyring, type, payload,
+						  platform_trusted_keys);
+
 	return restrict_link_by_signature(dest_keyring, type, payload,
 					  secondary_trusted_keys);
 }
@@ -227,7 +232,11 @@ int verify_pkcs7_message_sig(const void *data, size_t len,
 		trusted_keys = builtin_trusted_keys;
 	} else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
-		trusted_keys = secondary_trusted_keys;
+		if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) &&
+		   secondary_trusts_platform)
+			trusted_keys = platform_trusted_keys;
+		else
+			trusted_keys = secondary_trusted_keys;
 #else
 		trusted_keys = builtin_trusted_keys;
 #endif
@@ -312,4 +321,12 @@ void __init set_platform_trusted_keys(struct key *keyring)
 {
 	platform_trusted_keys = keyring;
 }
+
+void __init set_trust_platform_keys(void)
+{
+	secondary_trusts_platform = true;
+
+	if (key_link(platform_trusted_keys, secondary_trusted_keys) < 0)
+		panic("Can't link trusted keyrings\n");
+}
 #endif
diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
index fb8b07daa9d1..ffa5f0173ba8 100644
--- a/include/keys/system_keyring.h
+++ b/include/keys/system_keyring.h
@@ -72,4 +72,14 @@ static inline void set_platform_trusted_keys(struct key *keyring)
 }
 #endif
 
+#if defined(CONFIG_INTEGRITY_PLATFORM_KEYRING) && \
+	defined(CONFIG_SYSTEM_TRUSTED_KEYRING) && \
+	defined(CONFIG_SECONDARY_TRUSTED_KEYRING)
+extern void __init set_trust_platform_keys(void);
+#else
+static inline void __init set_trust_platform_keys(void)
+{
+}
+#endif
+
 #endif /* _KEYS_SYSTEM_KEYRING_H */
-- 
2.18.4