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Subject[PATCH] ima: define '_ima' as a builtin 'trusted' keyring
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Date
Require all keys added to the IMA keyring be signed by an
existing trusted key on the system trusted 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)

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
---
security/integrity/digsig.c | 30 +++++++++++++++++++++++++++++-
security/integrity/ima/Kconfig | 8 ++++++++
security/integrity/ima/ima_appraise.c | 11 +++++++++++
security/integrity/integrity.h | 7 +++++++
4 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index b4af4eb..77ca965 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>

@@ -21,11 +23,19 @@

static struct key *keyring[INTEGRITY_KEYRING_MAX];

+#ifdef CONFIG_IMA_TRUSTED_KEYRING
+static const char *keyring_name[INTEGRITY_KEYRING_MAX] = {
+ ".evm",
+ ".module",
+ ".ima",
+};
+#else
static const char *keyring_name[INTEGRITY_KEYRING_MAX] = {
"_evm",
"_module",
"_ima",
};
+#endif

int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
const char *digest, int digestlen)
@@ -35,7 +45,7 @@ int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,

if (!keyring[id]) {
keyring[id] =
- request_key(&key_type_keyring, keyring_name[id], NULL);
+ request_key(&key_type_keyring, keyring_name[id], NULL);
if (IS_ERR(keyring[id])) {
int err = PTR_ERR(keyring[id]);
pr_err("no %s keyring: %d\n", keyring_name[id], err);
@@ -56,3 +66,21 @@ 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();
+ const struct user_struct *user = cred->user;
+
+ 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_ALLOC_NOT_IN_QUOTA, user->uid_keyring);
+ 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]));
+ 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_appraise.c b/security/integrity/ima/ima_appraise.c
index 734e946..46353ee 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -381,3 +381,14 @@ int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
}
return result;
}
+
+#ifdef CONFIG_IMA_TRUSTED_KEYRING
+static int __init init_ima_keyring(void)
+{
+ int ret;
+
+ ret = integrity_init_keyring(INTEGRITY_KEYRING_IMA);
+ return 0;
+}
+late_initcall(init_ima_keyring);
+#endif
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 2fb5e53..b9e7c13 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -137,12 +137,19 @@ static inline int integrity_digsig_verify(const unsigned int id,
#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
int asymmetric_verify(struct key *keyring, const char *sig,
int siglen, const char *data, int datalen);
+
+int integrity_init_keyring(const unsigned int id);
#else
static inline int asymmetric_verify(struct key *keyring, const char *sig,
int siglen, const char *data, int datalen)
{
return -EOPNOTSUPP;
}
+
+static int integrity_init_keyring(const unsigned int id)
+{
+ return 0;
+}
#endif

#ifdef CONFIG_INTEGRITY_AUDIT
--
1.8.1.4




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