[PATCH v3 3/3] ima: enable loading of build time generated key on .ima keyring

From: Nayna Jain
Date: Tue Mar 30 2021 - 09:18:05 EST


The kernel currently only loads the kernel module signing key onto the
builtin trusted keyring. Load the module signing key onto the IMA keyring
as well.

Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxx>
---
certs/system_certificates.S | 13 +++++++++-
certs/system_keyring.c | 47 +++++++++++++++++++++++++++--------
include/keys/system_keyring.h | 7 ++++++
security/integrity/digsig.c | 2 ++
4 files changed, 58 insertions(+), 11 deletions(-)

diff --git a/certs/system_certificates.S b/certs/system_certificates.S
index 8f29058adf93..dcad27ea8527 100644
--- a/certs/system_certificates.S
+++ b/certs/system_certificates.S
@@ -8,9 +8,11 @@
.globl system_certificate_list
system_certificate_list:
__cert_list_start:
-#ifdef CONFIG_MODULE_SIG
+__module_cert_start:
+#if defined(CONFIG_MODULE_SIG) || defined(CONFIG_IMA_APPRAISE_MODSIG)
.incbin "certs/signing_key.x509"
#endif
+__module_cert_end:
.incbin "certs/x509_certificate_list"
__cert_list_end:

@@ -35,3 +37,12 @@ system_certificate_list_size:
#else
.long __cert_list_end - __cert_list_start
#endif
+
+ .align 8
+ .globl module_cert_size
+module_cert_size:
+#ifdef CONFIG_64BIT
+ .quad __module_cert_end - __module_cert_start
+#else
+ .long __module_cert_end - __module_cert_start
+#endif
diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index 4b693da488f1..bb122bf4cc17 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -27,6 +27,7 @@ static struct key *platform_trusted_keys;

extern __initconst const u8 system_certificate_list[];
extern __initconst const unsigned long system_certificate_list_size;
+extern __initconst const unsigned long module_cert_size;

/**
* restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
@@ -132,19 +133,11 @@ static __init int system_trusted_keyring_init(void)
*/
device_initcall(system_trusted_keyring_init);

-/*
- * Load the compiled-in list of X.509 certificates.
- */
-static __init int load_system_certificate_list(void)
+static __init int load_cert(const u8 *p, const u8 *end, struct key *keyring)
{
key_ref_t key;
- const u8 *p, *end;
size_t plen;

- pr_notice("Loading compiled-in X.509 certificates\n");
-
- p = system_certificate_list;
- end = p + system_certificate_list_size;
while (p < end) {
/* Each cert begins with an ASN.1 SEQUENCE tag and must be more
* than 256 bytes in size.
@@ -159,7 +152,7 @@ static __init int load_system_certificate_list(void)
if (plen > end - p)
goto dodgy_cert;

- key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),
+ key = key_create_or_update(make_key_ref(keyring, 1),
"asymmetric",
NULL,
p,
@@ -186,6 +179,40 @@ static __init int load_system_certificate_list(void)
pr_err("Problem parsing in-kernel X.509 certificate list\n");
return 0;
}
+
+__init int load_module_cert(struct key *keyring)
+{
+ const u8 *p, *end;
+
+ if (!IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG))
+ return 0;
+
+ pr_notice("Loading compiled-in module X.509 certificates\n");
+
+ p = system_certificate_list;
+ end = p + module_cert_size;
+
+ return load_cert(p, end, keyring);
+}
+
+/*
+ * Load the compiled-in list of X.509 certificates.
+ */
+static __init int load_system_certificate_list(void)
+{
+ const u8 *p, *end;
+
+ pr_notice("Loading compiled-in X.509 certificates\n");
+
+#ifdef CONFIG_MODULE_SIG
+ p = system_certificate_list;
+#else
+ p = system_certificate_list + module_cert_size;
+#endif
+
+ end = p + system_certificate_list_size;
+ return load_cert(p, end, builtin_trusted_keys);
+}
late_initcall(load_system_certificate_list);

#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
index fb8b07daa9d1..f954276c616a 100644
--- a/include/keys/system_keyring.h
+++ b/include/keys/system_keyring.h
@@ -16,9 +16,16 @@ extern int restrict_link_by_builtin_trusted(struct key *keyring,
const struct key_type *type,
const union key_payload *payload,
struct key *restriction_key);
+extern __init int load_module_cert(struct key *keyring);

#else
#define restrict_link_by_builtin_trusted restrict_link_reject
+
+static inline __init int load_module_cert(struct key *keyring)
+{
+ return 0;
+}
+
#endif

#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index 250fb0836156..3b06a01bd0fd 100644
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -111,6 +111,8 @@ 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_IMA)
+ load_module_cert(keyring[id]);
}

return err;
--
2.29.2