[PATCH v2 4/6] integrity: check whether imputed trust is enabled

From: Nayna Jain
Date: Wed Aug 09 2023 - 15:53:58 EST


trust_moklist() is specific to UEFI enabled systems. Other platforms
rely only on the Kconfig.

Define a generic wrapper named imputed_trust_enabled().

Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxx>
Reviewed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
---
security/integrity/digsig.c | 2 +-
security/integrity/integrity.h | 5 +++--
.../integrity/platform_certs/keyring_handler.c | 3 ++-
.../integrity/platform_certs/machine_keyring.c | 18 ++++++++++++++++--
4 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index d0704b1597d4..df387de29bfa 100644
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -113,7 +113,7 @@ static int __init __integrity_init_keyring(const unsigned int id,
} else {
if (id == INTEGRITY_KEYRING_PLATFORM)
set_platform_trusted_keys(keyring[id]);
- if (id == INTEGRITY_KEYRING_MACHINE && trust_moklist())
+ if (id == INTEGRITY_KEYRING_MACHINE && imputed_trust_enabled())
set_machine_trusted_keys(keyring[id]);
if (id == INTEGRITY_KEYRING_IMA)
load_module_cert(keyring[id]);
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 7167a6e99bdc..d7553c93f5c0 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -320,13 +320,14 @@ static inline void __init add_to_platform_keyring(const char *source,

#ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
void __init add_to_machine_keyring(const char *source, const void *data, size_t len);
-bool __init trust_moklist(void);
+bool __init imputed_trust_enabled(void);
#else
static inline void __init add_to_machine_keyring(const char *source,
const void *data, size_t len)
{
}
-static inline bool __init trust_moklist(void)
+
+static inline bool __init imputed_trust_enabled(void)
{
return false;
}
diff --git a/security/integrity/platform_certs/keyring_handler.c b/security/integrity/platform_certs/keyring_handler.c
index 1649d047e3b8..586027b9a3f5 100644
--- a/security/integrity/platform_certs/keyring_handler.c
+++ b/security/integrity/platform_certs/keyring_handler.c
@@ -61,7 +61,8 @@ __init efi_element_handler_t get_handler_for_db(const efi_guid_t *sig_type)
__init efi_element_handler_t get_handler_for_mok(const efi_guid_t *sig_type)
{
if (efi_guidcmp(*sig_type, efi_cert_x509_guid) == 0) {
- if (IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING) && trust_moklist())
+ if (IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING) &&
+ imputed_trust_enabled())
return add_to_machine_keyring;
else
return add_to_platform_keyring;
diff --git a/security/integrity/platform_certs/machine_keyring.c b/security/integrity/platform_certs/machine_keyring.c
index 9482e16cb2ca..a401640a63cd 100644
--- a/security/integrity/platform_certs/machine_keyring.c
+++ b/security/integrity/platform_certs/machine_keyring.c
@@ -34,7 +34,8 @@ void __init add_to_machine_keyring(const char *source, const void *data, size_t
* If the restriction check does not pass and the platform keyring
* is configured, try to add it into that keyring instead.
*/
- if (rc && efi_enabled(EFI_BOOT) && IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING))
+ if (rc && efi_enabled(EFI_BOOT) &&
+ IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING))
rc = integrity_load_cert(INTEGRITY_KEYRING_PLATFORM, source,
data, len, perm);

@@ -60,7 +61,7 @@ static __init bool uefi_check_trust_mok_keys(void)
return false;
}

-bool __init trust_moklist(void)
+static bool __init trust_moklist(void)
{
static bool initialized;
static bool trust_mok;
@@ -75,3 +76,16 @@ bool __init trust_moklist(void)

return trust_mok;
}
+
+/*
+ * Provides platform specific check for trusting imputed keys before loading
+ * on .machine keyring. UEFI systems enable this trust based on a variable,
+ * and for other platforms, it is always enabled.
+ */
+bool __init imputed_trust_enabled(void)
+{
+ if (efi_enabled(EFI_BOOT))
+ return trust_moklist();
+
+ return true;
+}
--
2.31.1