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authorDmitry Kasatkin <dmitry.kasatkin@huawei.com>2015-10-22 21:26:32 +0300
committerMimi Zohar <zohar@linux.vnet.ibm.com>2015-12-15 16:53:36 +0300
commit7626676320f398980a6bb4490fd58e924c888f6a (patch)
treebb852548419b70be34dc7f32765d70bd94cd8bbb /security/integrity/evm
parent26ddabfe96bb7468763c9c92791404d991b16250 (diff)
downloadlinux-7626676320f398980a6bb4490fd58e924c888f6a.tar.xz
evm: provide a function to set the EVM key from the kernel
A crypto HW kernel module can possibly initialize the EVM key from the kernel __init code to enable EVM before calling the 'init' process. This patch provides a function evm_set_key() to set the EVM key directly without using the KEY subsystem. Changes in v4: * kernel-doc style for evm_set_key Changes in v3: * error reporting moved to evm_set_key * EVM_INIT_HMAC moved to evm_set_key * added bitop to prevent key setting race Changes in v2: * use size_t for key size instead of signed int * provide EVM_MAX_KEY_SIZE macro in <linux/evm.h> * provide EVM_MIN_KEY_SIZE macro in <linux/evm.h> Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@huawei.com> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Diffstat (limited to 'security/integrity/evm')
-rw-r--r--security/integrity/evm/evm_crypto.c50
-rw-r--r--security/integrity/evm/evm_secfs.c10
2 files changed, 46 insertions, 14 deletions
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index 2c3591eca989..30b6b7d0429f 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -18,6 +18,7 @@
#include <linux/module.h>
#include <linux/crypto.h>
#include <linux/xattr.h>
+#include <linux/evm.h>
#include <keys/encrypted-type.h>
#include <crypto/hash.h>
#include "evm.h"
@@ -32,6 +33,44 @@ struct crypto_shash *hash_tfm;
static DEFINE_MUTEX(mutex);
+#define EVM_SET_KEY_BUSY 0
+
+static unsigned long evm_set_key_flags;
+
+/**
+ * evm_set_key() - set EVM HMAC key from the kernel
+ * @key: pointer to a buffer with the key data
+ * @size: length of the key data
+ *
+ * This function allows setting the EVM HMAC key from the kernel
+ * without using the "encrypted" key subsystem keys. It can be used
+ * by the crypto HW kernel module which has its own way of managing
+ * keys.
+ *
+ * key length should be between 32 and 128 bytes long
+ */
+int evm_set_key(void *key, size_t keylen)
+{
+ int rc;
+
+ rc = -EBUSY;
+ if (test_and_set_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags))
+ goto busy;
+ rc = -EINVAL;
+ if (keylen > MAX_KEY_SIZE)
+ goto inval;
+ memcpy(evmkey, key, keylen);
+ evm_initialized |= EVM_INIT_HMAC;
+ pr_info("key initialized\n");
+ return 0;
+inval:
+ clear_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags);
+busy:
+ pr_err("key initialization failed\n");
+ return rc;
+}
+EXPORT_SYMBOL_GPL(evm_set_key);
+
static struct shash_desc *init_desc(char type)
{
long rc;
@@ -244,7 +283,7 @@ int evm_init_key(void)
{
struct key *evm_key;
struct encrypted_key_payload *ekp;
- int rc = 0;
+ int rc;
evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
if (IS_ERR(evm_key))
@@ -252,12 +291,9 @@ int evm_init_key(void)
down_read(&evm_key->sem);
ekp = evm_key->payload.data[0];
- if (ekp->decrypted_datalen > MAX_KEY_SIZE) {
- rc = -EINVAL;
- goto out;
- }
- memcpy(evmkey, ekp->decrypted_data, ekp->decrypted_datalen);
-out:
+
+ rc = evm_set_key(ekp->decrypted_data, ekp->decrypted_datalen);
+
/* burn the original key contents */
memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
up_read(&evm_key->sem);
diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
index 3f775dfea868..c8dccd54d501 100644
--- a/security/integrity/evm/evm_secfs.c
+++ b/security/integrity/evm/evm_secfs.c
@@ -62,7 +62,7 @@ static ssize_t evm_write_key(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
char temp[80];
- int i, error;
+ int i;
if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_INIT_HMAC))
return -EPERM;
@@ -78,12 +78,8 @@ static ssize_t evm_write_key(struct file *file, const char __user *buf,
if ((sscanf(temp, "%d", &i) != 1) || (i != 1))
return -EINVAL;
- error = evm_init_key();
- if (!error) {
- evm_initialized |= EVM_INIT_HMAC;
- pr_info("initialized\n");
- } else
- pr_err("initialization failed\n");
+ evm_init_key();
+
return count;
}