- 根目录:
- security
- integrity
- evm
- evm_main.c
/*
* 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 <crypto/hash.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_op->getxattr)
return -EOPNOTSUPP;
for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
error = inode->i_op->getxattr(dentry, *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:
rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
xattr_value_len, calc.digest);
if (rc)
break;
rc = memcmp(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;
}
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);
}
/**
* 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_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.
*/
void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
{
struct inode *inode = d_backing_inode(dentry);
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);
}
/**
* 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);
static int __init init_evm(void)
{
int error;
evm_init_config();
error = evm_init_secfs();
if (error < 0) {
pr_info("Error registering secfs\n");
goto err;
}
return 0;
err:
return error;
}
/*
* 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");