[RFC PATCH v5 3/4] ima: define '.ima' as a builtin 'trusted' keyring

Mimi Zohar
2014-06-03T17:59:00Z

Require all keys added to the IMA keyring be signed by an
existing trusted key on the system trusted keyring.

Changelog v5:
- Move integrity_init_keyring() to init_ima() - Dmitry
- reset keyring[id] on failure - Dmitry

Changelog v1:
- don't link IMA trusted keyring to user keyring

Changelog:
- define stub integrity_init_keyring() function (reported-by Fengguang Wu)
- differentiate between regular and trusted keyring names.
- replace printk with pr_info (D. Kasatkin)
- only make the IMA keyring a trusted keyring (reported-by D. Kastatkin)
- define stub integrity_init_keyring() definition based on
CONFIG_INTEGRITY_SIGNATURE, not CONFIG_INTEGRITY_ASYMMETRIC_KEYS.
(reported-by Jim Davis)

Signed-off-by: Mimi Zohar<zohar@linux.vnet.ibm.com>
---
security/integrity/digsig.c | 26 ++++++++++++++++++++++++++
security/integrity/ima/Kconfig | 8 ++++++++
security/integrity/ima/ima_main.c | 12 ++++++++++--
security/integrity/integrity.h | 5 +++++
4 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index b4af4eb..fa4c2fd 100644
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -13,7 +13,9 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/err.h>
+#include <linux/sched.h>
#include <linux/rbtree.h>
+#include <linux/cred.h>
#include <linux/key-type.h>
#include <linux/digsig.h>

@@ -24,7 +26,11 @@ static struct key *keyring[INTEGRITY_KEYRING_MAX];
static const char *keyring_name[INTEGRITY_KEYRING_MAX] = {
"_evm",
"_module",
+#ifndef CONFIG_IMA_TRUSTED_KEYRING
"_ima",
+#else
+ ".ima",
+#endif
};

int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
@@ -56,3 +62,23 @@ int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,

return -EOPNOTSUPP;
}
+
+int integrity_init_keyring(const unsigned int id)
+{
+ const struct cred *cred = current_cred();
+
+ keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
+ KGIDT_INIT(0), cred,
+ ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
+ KEY_USR_VIEW | KEY_USR_READ |
+ KEY_USR_WRITE | KEY_USR_SEARCH),
+ KEY_ALLOC_NOT_IN_QUOTA, NULL);
+ if (!IS_ERR(keyring[id]))
+ set_bit(KEY_FLAG_TRUSTED_ONLY, &keyring[id]->flags);
+ else {
+ pr_info("Can't allocate %s keyring (%ld)\n",
+ keyring_name[id], PTR_ERR(keyring[id]));
+ keyring[id] = NULL;
+ }
+ return 0;
+}
diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 81a2797..dad8d4c 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -123,3 +123,11 @@ config IMA_APPRAISE
For more information on integrity appraisal refer to:
<http://linux-ima.sourceforge.net>
If unsure, say N.
+
+config IMA_TRUSTED_KEYRING
+ bool "Require all keys on the _ima keyring be signed"
+ depends on IMA_APPRAISE && SYSTEM_TRUSTED_KEYRING
+ default y
+ help
+ This option requires that all keys added to the _ima
+ keyring be signed by a key on the system trusted keyring.
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 09baa33..4c60cc5 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -328,8 +328,16 @@ static int __init init_ima(void)

hash_setup(CONFIG_IMA_DEFAULT_HASH);
error = ima_init();
- if (!error)
- ima_initialized = 1;
+ if (error)
+ goto out;
+
+#ifdef CONFIG_IMA_TRUSTED_KEYRING
+ error = integrity_init_keyring(INTEGRITY_KEYRING_IMA);
+ if (error)
+ goto out;
+#endif
+ ima_initialized = 1;
+out:
return error;
}

diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 33c0a70..09c440d 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -124,6 +124,7 @@ struct integrity_iint_cache *integrity_iint_find(struct inode *inode);
int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
const char *digest, int digestlen);

+int integrity_init_keyring(const unsigned int id);
#else

static inline int integrity_digsig_verify(const unsigned int id,
@@ -133,6 +134,10 @@ static inline int integrity_digsig_verify(const unsigned int id,
return -EOPNOTSUPP;
}

+static inline int integrity_init_keyring(const unsigned int id)
+{
+ return 0;
+}
#endif /* CONFIG_INTEGRITY_SIGNATURE */

#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
--
1.8.1.4