security/integrity/evm/evm_main.c - arm/linux - Git at Google

 /*
  * 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
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/module.h>
 #include <linux/crypto.h>
 #include <linux/audit.h>
 #include <linux/xattr.h>
 #include <linux/integrity.h>
 #include <linux/evm.h>
 #include <linux/magic.h>

 #include <crypto/hash.h>
 #include <crypto/algapi.h>
 #include "evm.h"

 int evm_initialized;

 static char *integrity_status_msg[] = {
 	"pass", "fail", "no_label", "no_xattrs", "unknown"
 };
 char *evm_hmac = "hmac(sha1)";
 char *evm_hash = "sha1";
 int evm_hmac_attrs;

 char *evm_config_xattrnames[] = {
 #ifdef CONFIG_SECURITY_SELINUX
 	XATTR_NAME_SELINUX,
 #endif
 #ifdef CONFIG_SECURITY_SMACK
 	XATTR_NAME_SMACK,
 #ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
 	XATTR_NAME_SMACKEXEC,
 	XATTR_NAME_SMACKTRANSMUTE,
 	XATTR_NAME_SMACKMMAP,
 #endif
 #endif
 #ifdef CONFIG_IMA_APPRAISE
 	XATTR_NAME_IMA,
 #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);

 static void __init evm_init_config(void)
 {
 #ifdef CONFIG_EVM_ATTR_FSUUID
 	evm_hmac_attrs |= EVM_ATTR_FSUUID;
 #endif
 	pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
 }

 static int evm_find_protected_xattrs(struct dentry *dentry)
 {
 	struct inode *inode = d_backing_inode(dentry);
 	char **xattr;
 	int error;
 	int count = 0;

 	if (!(inode->i_opflags & IOP_XATTR))
 		return -EOPNOTSUPP;

 	for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
 		error = __vfs_getxattr(dentry, inode, *xattr, NULL, 0);
 		if (error < 0) {
 			if (error == -ENODATA)
 				continue;
 			return error;
 		}
 		count++;
 	}

 	return count;
 }

 /*
  * 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 = NULL;
 	struct evm_ima_xattr_data calc;
 	enum integrity_status evm_status = INTEGRITY_PASS;
 	int rc, xattr_len;

 	if (iint && iint->evm_status == INTEGRITY_PASS)
 		return iint->evm_status;

 	/* if status is not PASS, try to check again - against -ENOMEM */

 	/* first need to know the sig type */
 	rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
 				GFP_NOFS);
 	if (rc <= 0) {
 		evm_status = INTEGRITY_FAIL;
 		if (rc == -ENODATA) {
 			rc = evm_find_protected_xattrs(dentry);
 			if (rc > 0)
 				evm_status = INTEGRITY_NOLABEL;
 			else if (rc == 0)
 				evm_status = INTEGRITY_NOXATTRS; /* new file */
 		} else if (rc == -EOPNOTSUPP) {
 			evm_status = INTEGRITY_UNKNOWN;
 		}
 		goto out;
 	}

 	xattr_len = rc;

 	/* check value type */
 	switch (xattr_data->type) {
 	case EVM_XATTR_HMAC:
 		if (xattr_len != sizeof(struct evm_ima_xattr_data)) {
 			evm_status = INTEGRITY_FAIL;
 			goto out;
 		}
 		rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
 				   xattr_value_len, calc.digest);
 		if (rc)
 			break;
 		rc = crypto_memneq(xattr_data->digest, calc.digest,
 			    sizeof(calc.digest));
 		if (rc)
 			rc = -EINVAL;
 		break;
 	case EVM_IMA_XATTR_DIGSIG:
 		rc = evm_calc_hash(dentry, xattr_name, xattr_value,
 				xattr_value_len, calc.digest);
 		if (rc)
 			break;
 		rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
 					(const char *)xattr_data, xattr_len,
 					calc.digest, sizeof(calc.digest));
 		if (!rc) {
 			/* Replace RSA with HMAC if not mounted readonly and
 			 * not immutable
 			 */
 			if (!IS_RDONLY(d_backing_inode(dentry)) &&
 			    !IS_IMMUTABLE(d_backing_inode(dentry)))
 				evm_update_evmxattr(dentry, xattr_name,
 						    xattr_value,
 						    xattr_value_len);
 		}
 		break;
 	default:
 		rc = -EINVAL;
 		break;
 	}

 	if (rc)
 		evm_status = (rc == -ENODATA) ?
 				INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
 out:
 	if (iint)
 		iint->evm_status = evm_status;
 	kfree(xattr_data);
 	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(d_backing_inode(dentry));
 		if (!iint)
 			return INTEGRITY_UNKNOWN;
 	}
 	return evm_verify_hmac(dentry, xattr_name, xattr_value,
 				 xattr_value_len, iint);
 }
 EXPORT_SYMBOL_GPL(evm_verifyxattr);

 /*
  * 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 = d_backing_inode(dentry);

 	if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
 		return 0;
 	return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
 }

 /*
  * evm_protect_xattr - protect the EVM extended attribute
  *
  * Prevent security.evm from being modified or removed without the
  * necessary permissions or when the existing value is invalid.
  *
  * The posix xattr acls are 'system' prefixed, which normally would not
  * affect security.evm.  An interesting side affect of writing posix xattr
  * acls is their modifying of the i_mode, which is included in security.evm.
  * For posix xattr acls only, permit security.evm, even if it currently
  * doesn't exist, to be updated.
  */
 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
 			     const void *xattr_value, size_t xattr_value_len)
 {
 	enum integrity_status evm_status;

 	if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
 		if (!capable(CAP_SYS_ADMIN))
 			return -EPERM;
 	} else if (!evm_protected_xattr(xattr_name)) {
 		if (!posix_xattr_acl(xattr_name))
 			return 0;
 		evm_status = evm_verify_current_integrity(dentry);
 		if ((evm_status == INTEGRITY_PASS) ||
 		    (evm_status == INTEGRITY_NOXATTRS))
 			return 0;
 		goto out;
 	}
 	evm_status = evm_verify_current_integrity(dentry);
 	if (evm_status == INTEGRITY_NOXATTRS) {
 		struct integrity_iint_cache *iint;

 		iint = integrity_iint_find(d_backing_inode(dentry));
 		if (iint && (iint->flags & IMA_NEW_FILE))
 			return 0;

 		/* exception for pseudo filesystems */
 		if (dentry->d_sb->s_magic == TMPFS_MAGIC
 		    || dentry->d_sb->s_magic == SYSFS_MAGIC)
 			return 0;

 		integrity_audit_msg(AUDIT_INTEGRITY_METADATA,
 				    dentry->d_inode, dentry->d_name.name,
 				    "update_metadata",
 				    integrity_status_msg[evm_status],
 				    -EPERM, 0);
 	}
 out:
 	if (evm_status != INTEGRITY_PASS)
 		integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
 				    dentry->d_name.name, "appraise_metadata",
 				    integrity_status_msg[evm_status],
 				    -EPERM, 0);
 	return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
 }

 /**
  * 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
  *
  * Before allowing the 'security.evm' protected xattr to be updated,
  * verify the existing value is valid.  As only the kernel should have
  * access to the EVM encrypted key needed to calculate the HMAC, prevent
  * userspace from writing HMAC value.  Writing 'security.evm' requires
  * requires CAP_SYS_ADMIN privileges.
  */
 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
 		       const void *xattr_value, size_t xattr_value_len)
 {
 	const struct evm_ima_xattr_data *xattr_data = xattr_value;

 	if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
 		if (!xattr_value_len)
 			return -EINVAL;
 		if (xattr_data->type != EVM_IMA_XATTR_DIGSIG)
 			return -EPERM;
 	}
 	return evm_protect_xattr(dentry, xattr_name, xattr_value,
 				 xattr_value_len);
 }

 /**
  * 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)
 {
 	return evm_protect_xattr(dentry, xattr_name, NULL, 0);
 }

 static void evm_reset_status(struct inode *inode)
 {
 	struct integrity_iint_cache *iint;

 	iint = integrity_iint_find(inode);
 	if (iint)
 		iint->evm_status = INTEGRITY_UNKNOWN;
 }

 /**
  * 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)
 				 && !posix_xattr_acl(xattr_name)))
 		return;

 	evm_reset_status(dentry->d_inode);

 	evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
 }

 /**
  * 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.
  *
  * No need to take the i_mutex lock here, as this function is called from
  * vfs_removexattr() which takes the i_mutex.
  */
 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
 {
 	if (!evm_initialized || !evm_protected_xattr(xattr_name))
 		return;

 	evm_reset_status(dentry->d_inode);

 	evm_update_evmxattr(dentry, xattr_name, NULL, 0);
 }

 /**
  * 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);
 	if ((evm_status == INTEGRITY_PASS) ||
 	    (evm_status == INTEGRITY_NOXATTRS))
 		return 0;
 	integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
 			    dentry->d_name.name, "appraise_metadata",
 			    integrity_status_msg[evm_status], -EPERM, 0);
 	return -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);
 }

 /*
  * 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 0;

 	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 = XATTR_EVM_SUFFIX;
 	return 0;
 out:
 	kfree(xattr_data);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(evm_inode_init_security);

 #ifdef CONFIG_EVM_LOAD_X509
 void __init evm_load_x509(void)
 {
 	int rc;

 	rc = integrity_load_x509(INTEGRITY_KEYRING_EVM, CONFIG_EVM_X509_PATH);
 	if (!rc)
 		evm_initialized |= EVM_INIT_X509;
 }
 #endif

 static int __init init_evm(void)
 {
 	int error;

 	evm_init_config();

 	error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
 	if (error)
 		return error;

 	error = evm_init_secfs();
 	if (error < 0) {
 		pr_info("Error registering secfs\n");
 		return error;
 	}

 	return 0;
 }

 /*
  * 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++)
 		pr_info("%s\n", *xattrname);
 	return 0;
 }

 pure_initcall(evm_display_config);
 late_initcall(init_evm);

 MODULE_DESCRIPTION("Extended Verification Module");
 MODULE_LICENSE("GPL");
	/*
	* 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
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/module.h>
	#include <linux/crypto.h>
	#include <linux/audit.h>
	#include <linux/xattr.h>
	#include <linux/integrity.h>
	#include <linux/evm.h>
	#include <linux/magic.h>

	#include <crypto/hash.h>
	#include <crypto/algapi.h>
	#include "evm.h"

	int evm_initialized;

	static char *integrity_status_msg[] = {
	"pass", "fail", "no_label", "no_xattrs", "unknown"
	};
	char *evm_hmac = "hmac(sha1)";
	char *evm_hash = "sha1";
	int evm_hmac_attrs;

	char *evm_config_xattrnames[] = {
	#ifdef CONFIG_SECURITY_SELINUX
	XATTR_NAME_SELINUX,
	#endif
	#ifdef CONFIG_SECURITY_SMACK
	XATTR_NAME_SMACK,
	#ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
	XATTR_NAME_SMACKEXEC,
	XATTR_NAME_SMACKTRANSMUTE,
	XATTR_NAME_SMACKMMAP,
	#endif
	#endif
	#ifdef CONFIG_IMA_APPRAISE
	XATTR_NAME_IMA,
	#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);

	static void __init evm_init_config(void)
	{
	#ifdef CONFIG_EVM_ATTR_FSUUID
	evm_hmac_attrs \|= EVM_ATTR_FSUUID;
	#endif
	pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
	}

	static int evm_find_protected_xattrs(struct dentry *dentry)
	{
	struct inode *inode = d_backing_inode(dentry);
	char **xattr;
	int error;
	int count = 0;

	if (!(inode->i_opflags & IOP_XATTR))
	return -EOPNOTSUPP;

	for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
	error = __vfs_getxattr(dentry, inode, *xattr, NULL, 0);
	if (error < 0) {
	if (error == -ENODATA)
	continue;
	return error;
	}
	count++;
	}

	return count;
	}

	/*
	* 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 = NULL;
	struct evm_ima_xattr_data calc;
	enum integrity_status evm_status = INTEGRITY_PASS;
	int rc, xattr_len;

	if (iint && iint->evm_status == INTEGRITY_PASS)
	return iint->evm_status;

	/* if status is not PASS, try to check again - against -ENOMEM */

	/* first need to know the sig type */
	rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
	GFP_NOFS);
	if (rc <= 0) {
	evm_status = INTEGRITY_FAIL;
	if (rc == -ENODATA) {
	rc = evm_find_protected_xattrs(dentry);
	if (rc > 0)
	evm_status = INTEGRITY_NOLABEL;
	else if (rc == 0)
	evm_status = INTEGRITY_NOXATTRS; /* new file */
	} else if (rc == -EOPNOTSUPP) {
	evm_status = INTEGRITY_UNKNOWN;
	}
	goto out;
	}

	xattr_len = rc;

	/* check value type */
	switch (xattr_data->type) {
	case EVM_XATTR_HMAC:
	if (xattr_len != sizeof(struct evm_ima_xattr_data)) {
	evm_status = INTEGRITY_FAIL;
	goto out;
	}
	rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
	xattr_value_len, calc.digest);
	if (rc)
	break;
	rc = crypto_memneq(xattr_data->digest, calc.digest,
	sizeof(calc.digest));
	if (rc)
	rc = -EINVAL;
	break;
	case EVM_IMA_XATTR_DIGSIG:
	rc = evm_calc_hash(dentry, xattr_name, xattr_value,
	xattr_value_len, calc.digest);
	if (rc)
	break;
	rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
	(const char *)xattr_data, xattr_len,
	calc.digest, sizeof(calc.digest));
	if (!rc) {
	/* Replace RSA with HMAC if not mounted readonly and
	* not immutable
	*/
	if (!IS_RDONLY(d_backing_inode(dentry)) &&
	!IS_IMMUTABLE(d_backing_inode(dentry)))
	evm_update_evmxattr(dentry, xattr_name,
	xattr_value,
	xattr_value_len);
	}
	break;
	default:
	rc = -EINVAL;
	break;
	}

	if (rc)
	evm_status = (rc == -ENODATA) ?
	INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
	out:
	if (iint)
	iint->evm_status = evm_status;
	kfree(xattr_data);
	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(d_backing_inode(dentry));
	if (!iint)
	return INTEGRITY_UNKNOWN;
	}
	return evm_verify_hmac(dentry, xattr_name, xattr_value,
	xattr_value_len, iint);
	}
	EXPORT_SYMBOL_GPL(evm_verifyxattr);

	/*
	* 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 = d_backing_inode(dentry);

	if (!evm_initialized \|\| !S_ISREG(inode->i_mode) \|\| evm_fixmode)
	return 0;
	return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
	}

	/*
	* evm_protect_xattr - protect the EVM extended attribute
	*
	* Prevent security.evm from being modified or removed without the
	* necessary permissions or when the existing value is invalid.
	*
	* The posix xattr acls are 'system' prefixed, which normally would not
	* affect security.evm. An interesting side affect of writing posix xattr
	* acls is their modifying of the i_mode, which is included in security.evm.
	* For posix xattr acls only, permit security.evm, even if it currently
	* doesn't exist, to be updated.
	*/
	static int evm_protect_xattr(struct dentry dentry, const char xattr_name,
	const void *xattr_value, size_t xattr_value_len)
	{
	enum integrity_status evm_status;

	if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
	if (!capable(CAP_SYS_ADMIN))
	return -EPERM;
	} else if (!evm_protected_xattr(xattr_name)) {
	if (!posix_xattr_acl(xattr_name))
	return 0;
	evm_status = evm_verify_current_integrity(dentry);
	if ((evm_status == INTEGRITY_PASS) \|\|
	(evm_status == INTEGRITY_NOXATTRS))
	return 0;
	goto out;
	}
	evm_status = evm_verify_current_integrity(dentry);
	if (evm_status == INTEGRITY_NOXATTRS) {
	struct integrity_iint_cache *iint;

	iint = integrity_iint_find(d_backing_inode(dentry));
	if (iint && (iint->flags & IMA_NEW_FILE))
	return 0;

	/* exception for pseudo filesystems */
	if (dentry->d_sb->s_magic == TMPFS_MAGIC
	\|\| dentry->d_sb->s_magic == SYSFS_MAGIC)
	return 0;

	integrity_audit_msg(AUDIT_INTEGRITY_METADATA,
	dentry->d_inode, dentry->d_name.name,
	"update_metadata",
	integrity_status_msg[evm_status],
	-EPERM, 0);
	}
	out:
	if (evm_status != INTEGRITY_PASS)
	integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
	dentry->d_name.name, "appraise_metadata",
	integrity_status_msg[evm_status],
	-EPERM, 0);
	return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
	}

	/**
	* 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
	*
	* Before allowing the 'security.evm' protected xattr to be updated,
	* verify the existing value is valid. As only the kernel should have
	* access to the EVM encrypted key needed to calculate the HMAC, prevent
	* userspace from writing HMAC value. Writing 'security.evm' requires
	* requires CAP_SYS_ADMIN privileges.
	*/
	int evm_inode_setxattr(struct dentry dentry, const char xattr_name,
	const void *xattr_value, size_t xattr_value_len)
	{
	const struct evm_ima_xattr_data *xattr_data = xattr_value;

	if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
	if (!xattr_value_len)
	return -EINVAL;
	if (xattr_data->type != EVM_IMA_XATTR_DIGSIG)
	return -EPERM;
	}
	return evm_protect_xattr(dentry, xattr_name, xattr_value,
	xattr_value_len);
	}

	/**
	* 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)
	{
	return evm_protect_xattr(dentry, xattr_name, NULL, 0);
	}

	static void evm_reset_status(struct inode *inode)
	{
	struct integrity_iint_cache *iint;

	iint = integrity_iint_find(inode);
	if (iint)
	iint->evm_status = INTEGRITY_UNKNOWN;
	}

	/**
	* 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)
	&& !posix_xattr_acl(xattr_name)))
	return;

	evm_reset_status(dentry->d_inode);

	evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
	}

	/**
	* 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.
	*
	* No need to take the i_mutex lock here, as this function is called from
	* vfs_removexattr() which takes the i_mutex.
	*/
	void evm_inode_post_removexattr(struct dentry dentry, const char xattr_name)
	{
	if (!evm_initialized \|\| !evm_protected_xattr(xattr_name))
	return;

	evm_reset_status(dentry->d_inode);

	evm_update_evmxattr(dentry, xattr_name, NULL, 0);
	}

	/**
	* 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);
	if ((evm_status == INTEGRITY_PASS) \|\|
	(evm_status == INTEGRITY_NOXATTRS))
	return 0;
	integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
	dentry->d_name.name, "appraise_metadata",
	integrity_status_msg[evm_status], -EPERM, 0);
	return -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);
	}

	/*
	* 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 0;

	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 = XATTR_EVM_SUFFIX;
	return 0;
	out:
	kfree(xattr_data);
	return rc;
	}
	EXPORT_SYMBOL_GPL(evm_inode_init_security);

	#ifdef CONFIG_EVM_LOAD_X509
	void __init evm_load_x509(void)
	{
	int rc;

	rc = integrity_load_x509(INTEGRITY_KEYRING_EVM, CONFIG_EVM_X509_PATH);
	if (!rc)
	evm_initialized \|= EVM_INIT_X509;
	}
	#endif

	static int __init init_evm(void)
	{
	int error;

	evm_init_config();

	error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
	if (error)
	return error;

	error = evm_init_secfs();
	if (error < 0) {
	pr_info("Error registering secfs\n");
	return error;
	}

	return 0;
	}

	/*
	* 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++)
	pr_info("%s\n", *xattrname);
	return 0;
	}

	pure_initcall(evm_display_config);
	late_initcall(init_evm);

	MODULE_DESCRIPTION("Extended Verification Module");
	MODULE_LICENSE("GPL");