Merge branch 'next-evm' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/ima-2.6 into next

Conflicts:
	fs/attr.c

Resolve conflict manually.

Signed-off-by: James Morris <jmorris@namei.org>

6 files changed, 764 insertions, 0 deletions

diff --git a/security/integrity/evm/Kconfig b/security/integrity/evm/Kconfig
new file mode 100644
index 000000000000..73f654099a4b
--- /dev/null
+++ b/security/integrity/evm/Kconfig
@@ -0,0 +1,12 @@
+config EVM
+        boolean "EVM support"
+        depends on SECURITY && KEYS && ENCRYPTED_KEYS
+        select CRYPTO_HMAC
+        select CRYPTO_MD5
+        select CRYPTO_SHA1
+        default n
+        help
+          EVM protects a file's security extended attributes against
+          integrity attacks.
+
+          If you are unsure how to answer this question, answer N.
diff --git a/security/integrity/evm/Makefile b/security/integrity/evm/Makefile
new file mode 100644
index 000000000000..0787d262b9e3
--- /dev/null
+++ b/security/integrity/evm/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for building the Extended Verification Module(EVM)
+#
+obj-$(CONFIG_EVM) += evm.o
+
+evm-y := evm_main.o evm_crypto.o evm_secfs.o
diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h
new file mode 100644
index 000000000000..d320f5197437
--- /dev/null
+++ b/security/integrity/evm/evm.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2005-2010 IBM Corporation
+ *
+ * Authors:
+ * Mimi Zohar <zohar@us.ibm.com>
+ * Kylene Hall <kjhall@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * File: evm.h
+ *
+ */
+#include <linux/xattr.h>
+#include <linux/security.h>
+#include "../integrity.h"
+
+extern int evm_initialized;
+extern char *evm_hmac;
+
+extern struct crypto_shash *hmac_tfm;
+
+/* List of EVM protected security xattrs */
+extern char *evm_config_xattrnames[];
+
+extern int evm_init_key(void);
+extern int evm_update_evmxattr(struct dentry *dentry,
+                               const char *req_xattr_name,
+                               const char *req_xattr_value,
+                               size_t req_xattr_value_len);
+extern int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
+                         const char *req_xattr_value,
+                         size_t req_xattr_value_len, char *digest);
+extern int evm_init_hmac(struct inode *inode, const struct xattr *xattr,
+                         char *hmac_val);
+extern int evm_init_secfs(void);
+extern void evm_cleanup_secfs(void);
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
new file mode 100644
index 000000000000..5dd5b140242c
--- /dev/null
+++ b/security/integrity/evm/evm_crypto.c
@@ -0,0 +1,216 @@
+/*
+ * Copyright (C) 2005-2010 IBM Corporation
+ *
+ * Authors:
+ * Mimi Zohar <zohar@us.ibm.com>
+ * Kylene Hall <kjhall@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * File: evm_crypto.c
+ *       Using root's kernel master key (kmk), calculate the HMAC
+ */
+
+#include <linux/module.h>
+#include <linux/crypto.h>
+#include <linux/xattr.h>
+#include <keys/encrypted-type.h>
+#include <crypto/hash.h>
+#include "evm.h"
+
+#define EVMKEY "evm-key"
+#define MAX_KEY_SIZE 128
+static unsigned char evmkey[MAX_KEY_SIZE];
+static int evmkey_len = MAX_KEY_SIZE;
+
+struct crypto_shash *hmac_tfm;
+
+static struct shash_desc *init_desc(void)
+{
+        int rc;
+        struct shash_desc *desc;
+
+        if (hmac_tfm == NULL) {
+                hmac_tfm = crypto_alloc_shash(evm_hmac, 0, CRYPTO_ALG_ASYNC);
+                if (IS_ERR(hmac_tfm)) {
+                        pr_err("Can not allocate %s (reason: %ld)\n",
+                               evm_hmac, PTR_ERR(hmac_tfm));
+                        rc = PTR_ERR(hmac_tfm);
+                        hmac_tfm = NULL;
+                        return ERR_PTR(rc);
+                }
+        }
+
+        desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(hmac_tfm),
+                        GFP_KERNEL);
+        if (!desc)
+                return ERR_PTR(-ENOMEM);
+
+        desc->tfm = hmac_tfm;
+        desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
+
+        rc = crypto_shash_setkey(hmac_tfm, evmkey, evmkey_len);
+        if (rc)
+                goto out;
+        rc = crypto_shash_init(desc);
+out:
+        if (rc) {
+                kfree(desc);
+                return ERR_PTR(rc);
+        }
+        return desc;
+}
+
+/* Protect against 'cutting & pasting' security.evm xattr, include inode
+ * specific info.
+ *
+ * (Additional directory/file metadata needs to be added for more complete
+ * protection.)
+ */
+static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
+                          char *digest)
+{
+        struct h_misc {
+                unsigned long ino;
+                __u32 generation;
+                uid_t uid;
+                gid_t gid;
+                umode_t mode;
+        } hmac_misc;
+
+        memset(&hmac_misc, 0, sizeof hmac_misc);
+        hmac_misc.ino = inode->i_ino;
+        hmac_misc.generation = inode->i_generation;
+        hmac_misc.uid = inode->i_uid;
+        hmac_misc.gid = inode->i_gid;
+        hmac_misc.mode = inode->i_mode;
+        crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof hmac_misc);
+        crypto_shash_final(desc, digest);
+}
+
+/*
+ * Calculate the HMAC value across the set of protected security xattrs.
+ *
+ * Instead of retrieving the requested xattr, for performance, calculate
+ * the hmac using the requested xattr value. Don't alloc/free memory for
+ * each xattr, but attempt to re-use the previously allocated memory.
+ */
+int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
+                  const char *req_xattr_value, size_t req_xattr_value_len,
+                  char *digest)
+{
+        struct inode *inode = dentry->d_inode;
+        struct shash_desc *desc;
+        char **xattrname;
+        size_t xattr_size = 0;
+        char *xattr_value = NULL;
+        int error;
+        int size;
+
+        if (!inode->i_op || !inode->i_op->getxattr)
+                return -EOPNOTSUPP;
+        desc = init_desc();
+        if (IS_ERR(desc))
+                return PTR_ERR(desc);
+
+        error = -ENODATA;
+        for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
+                if ((req_xattr_name && req_xattr_value)
+                    && !strcmp(*xattrname, req_xattr_name)) {
+                        error = 0;
+                        crypto_shash_update(desc, (const u8 *)req_xattr_value,
+                                             req_xattr_value_len);
+                        continue;
+                }
+                size = vfs_getxattr_alloc(dentry, *xattrname,
+                                          &xattr_value, xattr_size, GFP_NOFS);
+                if (size == -ENOMEM) {
+                        error = -ENOMEM;
+                        goto out;
+                }
+                if (size < 0)
+                        continue;
+
+                error = 0;
+                xattr_size = size;
+                crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
+        }
+        hmac_add_misc(desc, inode, digest);
+
+out:
+        kfree(xattr_value);
+        kfree(desc);
+        return error;
+}
+
+/*
+ * Calculate the hmac and update security.evm xattr
+ *
+ * Expects to be called with i_mutex locked.
+ */
+int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
+                        const char *xattr_value, size_t xattr_value_len)
+{
+        struct inode *inode = dentry->d_inode;
+        struct evm_ima_xattr_data xattr_data;
+        int rc = 0;
+
+        rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
+                           xattr_value_len, xattr_data.digest);
+        if (rc == 0) {
+                xattr_data.type = EVM_XATTR_HMAC;
+                rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
+                                           &xattr_data,
+                                           sizeof(xattr_data), 0);
+        }
+        else if (rc == -ENODATA)
+                rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
+        return rc;
+}
+
+int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
+                  char *hmac_val)
+{
+        struct shash_desc *desc;
+
+        desc = init_desc();
+        if (IS_ERR(desc)) {
+                printk(KERN_INFO "init_desc failed\n");
+                return PTR_ERR(desc);
+        }
+
+        crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
+        hmac_add_misc(desc, inode, hmac_val);
+        kfree(desc);
+        return 0;
+}
+
+/*
+ * Get the key from the TPM for the SHA1-HMAC
+ */
+int evm_init_key(void)
+{
+        struct key *evm_key;
+        struct encrypted_key_payload *ekp;
+        int rc = 0;
+
+        evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
+        if (IS_ERR(evm_key))
+                return -ENOENT;
+
+        down_read(&evm_key->sem);
+        ekp = evm_key->payload.data;
+        if (ekp->decrypted_datalen > MAX_KEY_SIZE) {
+                rc = -EINVAL;
+                goto out;
+        }
+        memcpy(evmkey, ekp->decrypted_data, ekp->decrypted_datalen);
+out:
+        /* burn the original key contents */
+        memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
+        up_read(&evm_key->sem);
+        key_put(evm_key);
+        return rc;
+}
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
new file mode 100644
index 000000000000..8fc5b5d7ceaa
--- /dev/null
+++ b/security/integrity/evm/evm_main.c
@@ -0,0 +1,384 @@
+/*
+ * Copyright (C) 2005-2010 IBM Corporation
+ *
+ * Author:
+ * Mimi Zohar <zohar@us.ibm.com>
+ * Kylene Hall <kjhall@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * File: evm_main.c
+ *      implements evm_inode_setxattr, evm_inode_post_setxattr,
+ *      evm_inode_removexattr, and evm_verifyxattr
+ */
+
+#include <linux/module.h>
+#include <linux/crypto.h>
+#include <linux/xattr.h>
+#include <linux/integrity.h>
+#include <linux/evm.h>
+#include <crypto/hash.h>
+#include "evm.h"
+
+int evm_initialized;
+
+char *evm_hmac = "hmac(sha1)";
+
+char *evm_config_xattrnames[] = {
+#ifdef CONFIG_SECURITY_SELINUX
+        XATTR_NAME_SELINUX,
+#endif
+#ifdef CONFIG_SECURITY_SMACK
+        XATTR_NAME_SMACK,
+#endif
+        XATTR_NAME_CAPS,
+        NULL
+};
+
+static int evm_fixmode;
+static int __init evm_set_fixmode(char *str)
+{
+        if (strncmp(str, "fix", 3) == 0)
+                evm_fixmode = 1;
+        return 0;
+}
+__setup("evm=", evm_set_fixmode);
+
+/*
+ * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
+ *
+ * Compute the HMAC on the dentry's protected set of extended attributes
+ * and compare it against the stored security.evm xattr.
+ *
+ * For performance:
+ * - use the previoulsy retrieved xattr value and length to calculate the
+ *   HMAC.)
+ * - cache the verification result in the iint, when available.
+ *
+ * Returns integrity status
+ */
+static enum integrity_status evm_verify_hmac(struct dentry *dentry,
+                                             const char *xattr_name,
+                                             char *xattr_value,
+                                             size_t xattr_value_len,
+                                             struct integrity_iint_cache *iint)
+{
+        struct evm_ima_xattr_data xattr_data;
+        enum integrity_status evm_status;
+        int rc;
+
+        if (iint && iint->evm_status == INTEGRITY_PASS)
+                return iint->evm_status;
+
+        /* if status is not PASS, try to check again - against -ENOMEM */
+
+        rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
+                           xattr_value_len, xattr_data.digest);
+        if (rc < 0)
+                goto err_out;
+
+        xattr_data.type = EVM_XATTR_HMAC;
+        rc = vfs_xattr_cmp(dentry, XATTR_NAME_EVM, (u8 *)&xattr_data,
+                           sizeof xattr_data, GFP_NOFS);
+        if (rc < 0)
+                goto err_out;
+        evm_status = INTEGRITY_PASS;
+        goto out;
+
+err_out:
+        switch (rc) {
+        case -ENODATA:          /* file not labelled */
+                evm_status = INTEGRITY_NOLABEL;
+                break;
+        default:
+                evm_status = INTEGRITY_FAIL;
+        }
+out:
+        if (iint)
+                iint->evm_status = evm_status;
+        return evm_status;
+}
+
+static int evm_protected_xattr(const char *req_xattr_name)
+{
+        char **xattrname;
+        int namelen;
+        int found = 0;
+
+        namelen = strlen(req_xattr_name);
+        for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
+                if ((strlen(*xattrname) == namelen)
+                    && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
+                        found = 1;
+                        break;
+                }
+                if (strncmp(req_xattr_name,
+                            *xattrname + XATTR_SECURITY_PREFIX_LEN,
+                            strlen(req_xattr_name)) == 0) {
+                        found = 1;
+                        break;
+                }
+        }
+        return found;
+}
+
+/**
+ * evm_verifyxattr - verify the integrity of the requested xattr
+ * @dentry: object of the verify xattr
+ * @xattr_name: requested xattr
+ * @xattr_value: requested xattr value
+ * @xattr_value_len: requested xattr value length
+ *
+ * Calculate the HMAC for the given dentry and verify it against the stored
+ * security.evm xattr. For performance, use the xattr value and length
+ * previously retrieved to calculate the HMAC.
+ *
+ * Returns the xattr integrity status.
+ *
+ * This function requires the caller to lock the inode's i_mutex before it
+ * is executed.
+ */
+enum integrity_status evm_verifyxattr(struct dentry *dentry,
+                                      const char *xattr_name,
+                                      void *xattr_value, size_t xattr_value_len,
+                                      struct integrity_iint_cache *iint)
+{
+        if (!evm_initialized || !evm_protected_xattr(xattr_name))
+                return INTEGRITY_UNKNOWN;
+
+        if (!iint) {
+                iint = integrity_iint_find(dentry->d_inode);
+                if (!iint)
+                        return INTEGRITY_UNKNOWN;
+        }
+        return evm_verify_hmac(dentry, xattr_name, xattr_value,
+                                 xattr_value_len, iint);
+}
+EXPORT_SYMBOL_GPL(evm_verifyxattr);
+
+/*
+ * evm_protect_xattr - protect the EVM extended attribute
+ *
+ * Prevent security.evm from being modified or removed.
+ */
+static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
+                             const void *xattr_value, size_t xattr_value_len)
+{
+        if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
+                if (!capable(CAP_SYS_ADMIN))
+                        return -EPERM;
+        }
+        return 0;
+}
+
+/*
+ * evm_verify_current_integrity - verify the dentry's metadata integrity
+ * @dentry: pointer to the affected dentry
+ *
+ * Verify and return the dentry's metadata integrity. The exceptions are
+ * before EVM is initialized or in 'fix' mode.
+ */
+static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
+{
+        struct inode *inode = dentry->d_inode;
+
+        if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
+                return 0;
+        return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
+}
+
+/**
+ * evm_inode_setxattr - protect the EVM extended attribute
+ * @dentry: pointer to the affected dentry
+ * @xattr_name: pointer to the affected extended attribute name
+ * @xattr_value: pointer to the new extended attribute value
+ * @xattr_value_len: pointer to the new extended attribute value length
+ *
+ * Updating 'security.evm' requires CAP_SYS_ADMIN privileges and that
+ * the current value is valid.
+ */
+int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
+                       const void *xattr_value, size_t xattr_value_len)
+{
+
+        enum integrity_status evm_status;
+        int ret;
+
+        ret = evm_protect_xattr(dentry, xattr_name, xattr_value,
+                                xattr_value_len);
+        if (ret)
+                return ret;
+        evm_status = evm_verify_current_integrity(dentry);
+        return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
+}
+
+/**
+ * evm_inode_removexattr - protect the EVM extended attribute
+ * @dentry: pointer to the affected dentry
+ * @xattr_name: pointer to the affected extended attribute name
+ *
+ * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
+ * the current value is valid.
+ */
+int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
+{
+        enum integrity_status evm_status;
+        int ret;
+
+        ret = evm_protect_xattr(dentry, xattr_name, NULL, 0);
+        if (ret)
+                return ret;
+        evm_status = evm_verify_current_integrity(dentry);
+        return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
+}
+
+/**
+ * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
+ * @dentry: pointer to the affected dentry
+ * @xattr_name: pointer to the affected extended attribute name
+ * @xattr_value: pointer to the new extended attribute value
+ * @xattr_value_len: pointer to the new extended attribute value length
+ *
+ * Update the HMAC stored in 'security.evm' to reflect the change.
+ *
+ * No need to take the i_mutex lock here, as this function is called from
+ * __vfs_setxattr_noperm().  The caller of which has taken the inode's
+ * i_mutex lock.
+ */
+void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
+                             const void *xattr_value, size_t xattr_value_len)
+{
+        if (!evm_initialized || !evm_protected_xattr(xattr_name))
+                return;
+
+        evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
+        return;
+}
+
+/**
+ * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
+ * @dentry: pointer to the affected dentry
+ * @xattr_name: pointer to the affected extended attribute name
+ *
+ * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
+ */
+void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
+{
+        struct inode *inode = dentry->d_inode;
+
+        if (!evm_initialized || !evm_protected_xattr(xattr_name))
+                return;
+
+        mutex_lock(&inode->i_mutex);
+        evm_update_evmxattr(dentry, xattr_name, NULL, 0);
+        mutex_unlock(&inode->i_mutex);
+        return;
+}
+
+/**
+ * evm_inode_setattr - prevent updating an invalid EVM extended attribute
+ * @dentry: pointer to the affected dentry
+ */
+int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
+{
+        unsigned int ia_valid = attr->ia_valid;
+        enum integrity_status evm_status;
+
+        if (ia_valid & ~(ATTR_MODE | ATTR_UID | ATTR_GID))
+                return 0;
+        evm_status = evm_verify_current_integrity(dentry);
+        return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
+}
+
+/**
+ * evm_inode_post_setattr - update 'security.evm' after modifying metadata
+ * @dentry: pointer to the affected dentry
+ * @ia_valid: for the UID and GID status
+ *
+ * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
+ * changes.
+ *
+ * This function is called from notify_change(), which expects the caller
+ * to lock the inode's i_mutex.
+ */
+void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
+{
+        if (!evm_initialized)
+                return;
+
+        if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
+                evm_update_evmxattr(dentry, NULL, NULL, 0);
+        return;
+}
+
+/*
+ * evm_inode_init_security - initializes security.evm
+ */
+int evm_inode_init_security(struct inode *inode,
+                                 const struct xattr *lsm_xattr,
+                                 struct xattr *evm_xattr)
+{
+        struct evm_ima_xattr_data *xattr_data;
+        int rc;
+
+        if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
+                return -EOPNOTSUPP;
+
+        xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
+        if (!xattr_data)
+                return -ENOMEM;
+
+        xattr_data->type = EVM_XATTR_HMAC;
+        rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
+        if (rc < 0)
+                goto out;
+
+        evm_xattr->value = xattr_data;
+        evm_xattr->value_len = sizeof(*xattr_data);
+        evm_xattr->name = kstrdup(XATTR_EVM_SUFFIX, GFP_NOFS);
+        return 0;
+out:
+        kfree(xattr_data);
+        return rc;
+}
+EXPORT_SYMBOL_GPL(evm_inode_init_security);
+
+static int __init init_evm(void)
+{
+        int error;
+
+        error = evm_init_secfs();
+        if (error < 0) {
+                printk(KERN_INFO "EVM: Error registering secfs\n");
+                goto err;
+        }
+err:
+        return error;
+}
+
+static void __exit cleanup_evm(void)
+{
+        evm_cleanup_secfs();
+        if (hmac_tfm)
+                crypto_free_shash(hmac_tfm);
+}
+
+/*
+ * evm_display_config - list the EVM protected security extended attributes
+ */
+static int __init evm_display_config(void)
+{
+        char **xattrname;
+
+        for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
+                printk(KERN_INFO "EVM: %s\n", *xattrname);
+        return 0;
+}
+
+pure_initcall(evm_display_config);
+late_initcall(init_evm);
+
+MODULE_DESCRIPTION("Extended Verification Module");
+MODULE_LICENSE("GPL");
diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
new file mode 100644
index 000000000000..ac7629950578
--- /dev/null
+++ b/security/integrity/evm/evm_secfs.c
@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2010 IBM Corporation
+ *
+ * Authors:
+ * Mimi Zohar <zohar@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * File: evm_secfs.c
+ *      - Used to signal when key is on keyring
+ *      - Get the key and enable EVM
+ */
+
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include "evm.h"
+
+static struct dentry *evm_init_tpm;
+
+/**
+ * evm_read_key - read() for <securityfs>/evm
+ *
+ * @filp: file pointer, not actually used
+ * @buf: where to put the result
+ * @count: maximum to send along
+ * @ppos: where to start
+ *
+ * Returns number of bytes read or error code, as appropriate
+ */
+static ssize_t evm_read_key(struct file *filp, char __user *buf,
+                            size_t count, loff_t *ppos)
+{
+        char temp[80];
+        ssize_t rc;
+
+        if (*ppos != 0)
+                return 0;
+
+        sprintf(temp, "%d", evm_initialized);
+        rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
+
+        return rc;
+}
+
+/**
+ * evm_write_key - write() for <securityfs>/evm
+ * @file: file pointer, not actually used
+ * @buf: where to get the data from
+ * @count: bytes sent
+ * @ppos: where to start
+ *
+ * Used to signal that key is on the kernel key ring.
+ * - get the integrity hmac key from the kernel key ring
+ * - create list of hmac protected extended attributes
+ * Returns number of bytes written or error code, as appropriate
+ */
+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;
+
+        if (!capable(CAP_SYS_ADMIN) || evm_initialized)
+                return -EPERM;
+
+        if (count >= sizeof(temp) || count == 0)
+                return -EINVAL;
+
+        if (copy_from_user(temp, buf, count) != 0)
+                return -EFAULT;
+
+        temp[count] = '\0';
+
+        if ((sscanf(temp, "%d", &i) != 1) || (i != 1))
+                return -EINVAL;
+
+        error = evm_init_key();
+        if (!error) {
+                evm_initialized = 1;
+                pr_info("EVM: initialized\n");
+        } else
+                pr_err("EVM: initialization failed\n");
+        return count;
+}
+
+static const struct file_operations evm_key_ops = {
+        .read           = evm_read_key,
+        .write          = evm_write_key,
+};
+
+int __init evm_init_secfs(void)
+{
+        int error = 0;
+
+        evm_init_tpm = securityfs_create_file("evm", S_IRUSR | S_IRGRP,
+                                              NULL, NULL, &evm_key_ops);
+        if (!evm_init_tpm || IS_ERR(evm_init_tpm))
+                error = -EFAULT;
+        return error;
+}
+
+void __exit evm_cleanup_secfs(void)
+{
+        if (evm_init_tpm)
+                securityfs_remove(evm_init_tpm);
+}