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![Stefan Berger](/assets/img/avatar_default.png)
Return INTEGRITY_PASS for the enum integrity_status rather than 0. Signed-off-by: Stefan Berger <stefanb@linux.ibm.com> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
910 lines
24 KiB
C
910 lines
24 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2005-2010 IBM Corporation
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*
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* Author:
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* Mimi Zohar <zohar@us.ibm.com>
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* Kylene Hall <kjhall@us.ibm.com>
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*
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* File: evm_main.c
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* implements evm_inode_setxattr, evm_inode_post_setxattr,
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* evm_inode_removexattr, and evm_verifyxattr
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*/
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#define pr_fmt(fmt) "EVM: "fmt
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#include <linux/init.h>
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#include <linux/crypto.h>
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#include <linux/audit.h>
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#include <linux/xattr.h>
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#include <linux/integrity.h>
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#include <linux/evm.h>
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#include <linux/magic.h>
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#include <linux/posix_acl_xattr.h>
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#include <crypto/hash.h>
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#include <crypto/hash_info.h>
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#include <crypto/algapi.h>
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#include "evm.h"
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int evm_initialized;
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static const char * const integrity_status_msg[] = {
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"pass", "pass_immutable", "fail", "fail_immutable", "no_label",
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"no_xattrs", "unknown"
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};
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int evm_hmac_attrs;
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static struct xattr_list evm_config_default_xattrnames[] = {
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{.name = XATTR_NAME_SELINUX,
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#ifdef CONFIG_SECURITY_SELINUX
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.enabled = true
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#endif
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},
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{.name = XATTR_NAME_SMACK,
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#ifdef CONFIG_SECURITY_SMACK
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.enabled = true
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#endif
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},
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{.name = XATTR_NAME_SMACKEXEC,
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#ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
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.enabled = true
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#endif
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},
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{.name = XATTR_NAME_SMACKTRANSMUTE,
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#ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
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.enabled = true
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#endif
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},
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{.name = XATTR_NAME_SMACKMMAP,
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#ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
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.enabled = true
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#endif
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},
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{.name = XATTR_NAME_APPARMOR,
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#ifdef CONFIG_SECURITY_APPARMOR
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.enabled = true
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#endif
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},
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{.name = XATTR_NAME_IMA,
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#ifdef CONFIG_IMA_APPRAISE
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.enabled = true
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#endif
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},
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{.name = XATTR_NAME_CAPS,
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.enabled = true
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},
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};
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LIST_HEAD(evm_config_xattrnames);
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static int evm_fixmode __ro_after_init;
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static int __init evm_set_fixmode(char *str)
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{
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if (strncmp(str, "fix", 3) == 0)
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evm_fixmode = 1;
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else
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pr_err("invalid \"%s\" mode", str);
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return 1;
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}
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__setup("evm=", evm_set_fixmode);
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static void __init evm_init_config(void)
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{
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int i, xattrs;
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xattrs = ARRAY_SIZE(evm_config_default_xattrnames);
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pr_info("Initialising EVM extended attributes:\n");
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for (i = 0; i < xattrs; i++) {
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pr_info("%s%s\n", evm_config_default_xattrnames[i].name,
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!evm_config_default_xattrnames[i].enabled ?
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" (disabled)" : "");
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list_add_tail(&evm_config_default_xattrnames[i].list,
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&evm_config_xattrnames);
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}
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#ifdef CONFIG_EVM_ATTR_FSUUID
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evm_hmac_attrs |= EVM_ATTR_FSUUID;
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#endif
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pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
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}
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static bool evm_key_loaded(void)
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{
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return (bool)(evm_initialized & EVM_KEY_MASK);
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}
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/*
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* This function determines whether or not it is safe to ignore verification
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* errors, based on the ability of EVM to calculate HMACs. If the HMAC key
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* is not loaded, and it cannot be loaded in the future due to the
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* EVM_SETUP_COMPLETE initialization flag, allowing an operation despite the
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* attrs/xattrs being found invalid will not make them valid.
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*/
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static bool evm_hmac_disabled(void)
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{
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if (evm_initialized & EVM_INIT_HMAC)
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return false;
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if (!(evm_initialized & EVM_SETUP_COMPLETE))
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return false;
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return true;
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}
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static int evm_find_protected_xattrs(struct dentry *dentry)
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{
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struct inode *inode = d_backing_inode(dentry);
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struct xattr_list *xattr;
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int error;
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int count = 0;
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if (!(inode->i_opflags & IOP_XATTR))
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return -EOPNOTSUPP;
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list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
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error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0);
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if (error < 0) {
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if (error == -ENODATA)
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continue;
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return error;
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}
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count++;
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}
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return count;
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}
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/*
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* evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
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*
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* Compute the HMAC on the dentry's protected set of extended attributes
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* and compare it against the stored security.evm xattr.
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*
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* For performance:
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* - use the previoulsy retrieved xattr value and length to calculate the
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* HMAC.)
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* - cache the verification result in the iint, when available.
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*
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* Returns integrity status
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*/
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static enum integrity_status evm_verify_hmac(struct dentry *dentry,
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const char *xattr_name,
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char *xattr_value,
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size_t xattr_value_len,
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struct integrity_iint_cache *iint)
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{
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struct evm_ima_xattr_data *xattr_data = NULL;
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struct signature_v2_hdr *hdr;
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enum integrity_status evm_status = INTEGRITY_PASS;
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struct evm_digest digest;
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struct inode *inode;
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int rc, xattr_len, evm_immutable = 0;
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if (iint && (iint->evm_status == INTEGRITY_PASS ||
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iint->evm_status == INTEGRITY_PASS_IMMUTABLE))
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return iint->evm_status;
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/* if status is not PASS, try to check again - against -ENOMEM */
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/* first need to know the sig type */
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rc = vfs_getxattr_alloc(&init_user_ns, dentry, XATTR_NAME_EVM,
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(char **)&xattr_data, 0, GFP_NOFS);
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if (rc <= 0) {
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evm_status = INTEGRITY_FAIL;
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if (rc == -ENODATA) {
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rc = evm_find_protected_xattrs(dentry);
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if (rc > 0)
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evm_status = INTEGRITY_NOLABEL;
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else if (rc == 0)
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evm_status = INTEGRITY_NOXATTRS; /* new file */
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} else if (rc == -EOPNOTSUPP) {
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evm_status = INTEGRITY_UNKNOWN;
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}
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goto out;
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}
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xattr_len = rc;
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/* check value type */
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switch (xattr_data->type) {
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case EVM_XATTR_HMAC:
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if (xattr_len != sizeof(struct evm_xattr)) {
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evm_status = INTEGRITY_FAIL;
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goto out;
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}
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digest.hdr.algo = HASH_ALGO_SHA1;
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rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
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xattr_value_len, &digest);
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if (rc)
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break;
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rc = crypto_memneq(xattr_data->data, digest.digest,
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SHA1_DIGEST_SIZE);
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if (rc)
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rc = -EINVAL;
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break;
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case EVM_XATTR_PORTABLE_DIGSIG:
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evm_immutable = 1;
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fallthrough;
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case EVM_IMA_XATTR_DIGSIG:
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/* accept xattr with non-empty signature field */
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if (xattr_len <= sizeof(struct signature_v2_hdr)) {
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evm_status = INTEGRITY_FAIL;
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goto out;
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}
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hdr = (struct signature_v2_hdr *)xattr_data;
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digest.hdr.algo = hdr->hash_algo;
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rc = evm_calc_hash(dentry, xattr_name, xattr_value,
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xattr_value_len, xattr_data->type, &digest);
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if (rc)
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break;
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rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
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(const char *)xattr_data, xattr_len,
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digest.digest, digest.hdr.length);
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if (!rc) {
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inode = d_backing_inode(dentry);
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if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) {
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if (iint)
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iint->flags |= EVM_IMMUTABLE_DIGSIG;
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evm_status = INTEGRITY_PASS_IMMUTABLE;
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} else if (!IS_RDONLY(inode) &&
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!(inode->i_sb->s_readonly_remount) &&
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!IS_IMMUTABLE(inode)) {
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evm_update_evmxattr(dentry, xattr_name,
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xattr_value,
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xattr_value_len);
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}
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}
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break;
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default:
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rc = -EINVAL;
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break;
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}
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if (rc) {
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if (rc == -ENODATA)
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evm_status = INTEGRITY_NOXATTRS;
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else if (evm_immutable)
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evm_status = INTEGRITY_FAIL_IMMUTABLE;
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else
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evm_status = INTEGRITY_FAIL;
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}
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pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length,
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digest.digest);
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out:
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if (iint)
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iint->evm_status = evm_status;
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kfree(xattr_data);
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return evm_status;
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}
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static int evm_protected_xattr_common(const char *req_xattr_name,
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bool all_xattrs)
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{
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int namelen;
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int found = 0;
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struct xattr_list *xattr;
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namelen = strlen(req_xattr_name);
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list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
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if (!all_xattrs && !xattr->enabled)
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continue;
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if ((strlen(xattr->name) == namelen)
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&& (strncmp(req_xattr_name, xattr->name, namelen) == 0)) {
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found = 1;
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break;
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}
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if (strncmp(req_xattr_name,
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xattr->name + XATTR_SECURITY_PREFIX_LEN,
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strlen(req_xattr_name)) == 0) {
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found = 1;
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break;
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}
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}
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return found;
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}
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static int evm_protected_xattr(const char *req_xattr_name)
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{
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return evm_protected_xattr_common(req_xattr_name, false);
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}
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int evm_protected_xattr_if_enabled(const char *req_xattr_name)
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{
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return evm_protected_xattr_common(req_xattr_name, true);
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}
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/**
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* evm_read_protected_xattrs - read EVM protected xattr names, lengths, values
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* @dentry: dentry of the read xattrs
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* @inode: inode of the read xattrs
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* @buffer: buffer xattr names, lengths or values are copied to
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* @buffer_size: size of buffer
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* @type: n: names, l: lengths, v: values
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* @canonical_fmt: data format (true: little endian, false: native format)
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*
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* Read protected xattr names (separated by |), lengths (u32) or values for a
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* given dentry and return the total size of copied data. If buffer is NULL,
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* just return the total size.
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*
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* Returns the total size on success, a negative value on error.
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*/
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int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer,
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int buffer_size, char type, bool canonical_fmt)
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{
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struct xattr_list *xattr;
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int rc, size, total_size = 0;
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list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
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rc = __vfs_getxattr(dentry, d_backing_inode(dentry),
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xattr->name, NULL, 0);
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if (rc < 0 && rc == -ENODATA)
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continue;
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else if (rc < 0)
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return rc;
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switch (type) {
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case 'n':
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size = strlen(xattr->name) + 1;
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if (buffer) {
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if (total_size)
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*(buffer + total_size - 1) = '|';
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memcpy(buffer + total_size, xattr->name, size);
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}
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break;
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case 'l':
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size = sizeof(u32);
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if (buffer) {
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if (canonical_fmt)
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rc = (__force int)cpu_to_le32(rc);
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*(u32 *)(buffer + total_size) = rc;
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}
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break;
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case 'v':
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size = rc;
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if (buffer) {
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rc = __vfs_getxattr(dentry,
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d_backing_inode(dentry), xattr->name,
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buffer + total_size,
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buffer_size - total_size);
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if (rc < 0)
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return rc;
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}
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break;
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default:
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return -EINVAL;
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}
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total_size += size;
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}
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return total_size;
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}
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/**
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* evm_verifyxattr - verify the integrity of the requested xattr
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* @dentry: object of the verify xattr
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* @xattr_name: requested xattr
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* @xattr_value: requested xattr value
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* @xattr_value_len: requested xattr value length
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*
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* Calculate the HMAC for the given dentry and verify it against the stored
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* security.evm xattr. For performance, use the xattr value and length
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* previously retrieved to calculate the HMAC.
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*
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* Returns the xattr integrity status.
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*
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* This function requires the caller to lock the inode's i_mutex before it
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* is executed.
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*/
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enum integrity_status evm_verifyxattr(struct dentry *dentry,
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const char *xattr_name,
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void *xattr_value, size_t xattr_value_len,
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struct integrity_iint_cache *iint)
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{
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if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
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return INTEGRITY_UNKNOWN;
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if (!iint) {
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iint = integrity_iint_find(d_backing_inode(dentry));
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if (!iint)
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return INTEGRITY_UNKNOWN;
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}
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return evm_verify_hmac(dentry, xattr_name, xattr_value,
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xattr_value_len, iint);
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}
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EXPORT_SYMBOL_GPL(evm_verifyxattr);
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/*
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* evm_verify_current_integrity - verify the dentry's metadata integrity
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* @dentry: pointer to the affected dentry
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*
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* Verify and return the dentry's metadata integrity. The exceptions are
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* before EVM is initialized or in 'fix' mode.
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*/
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static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
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{
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struct inode *inode = d_backing_inode(dentry);
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if (!evm_key_loaded() || !S_ISREG(inode->i_mode) || evm_fixmode)
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return INTEGRITY_PASS;
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return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
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}
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/*
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* evm_xattr_acl_change - check if passed ACL changes the inode mode
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* @mnt_userns: user namespace of the idmapped mount
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* @dentry: pointer to the affected dentry
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* @xattr_name: requested xattr
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* @xattr_value: requested xattr value
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* @xattr_value_len: requested xattr value length
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*
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* Check if passed ACL changes the inode mode, which is protected by EVM.
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*
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* Returns 1 if passed ACL causes inode mode change, 0 otherwise.
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*/
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static int evm_xattr_acl_change(struct user_namespace *mnt_userns,
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struct dentry *dentry, const char *xattr_name,
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const void *xattr_value, size_t xattr_value_len)
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{
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#ifdef CONFIG_FS_POSIX_ACL
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umode_t mode;
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struct posix_acl *acl = NULL, *acl_res;
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struct inode *inode = d_backing_inode(dentry);
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int rc;
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/*
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* user_ns is not relevant here, ACL_USER/ACL_GROUP don't have impact
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* on the inode mode (see posix_acl_equiv_mode()).
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*/
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acl = posix_acl_from_xattr(&init_user_ns, xattr_value, xattr_value_len);
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if (IS_ERR_OR_NULL(acl))
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return 1;
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acl_res = acl;
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/*
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* Passing mnt_userns is necessary to correctly determine the GID in
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* an idmapped mount, as the GID is used to clear the setgid bit in
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* the inode mode.
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*/
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rc = posix_acl_update_mode(mnt_userns, inode, &mode, &acl_res);
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posix_acl_release(acl);
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if (rc)
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return 1;
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if (inode->i_mode != mode)
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return 1;
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#endif
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return 0;
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}
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/*
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* evm_xattr_change - check if passed xattr value differs from current value
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* @mnt_userns: user namespace of the idmapped mount
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* @dentry: pointer to the affected dentry
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* @xattr_name: requested xattr
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* @xattr_value: requested xattr value
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* @xattr_value_len: requested xattr value length
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*
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* Check if passed xattr value differs from current value.
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*
|
|
* Returns 1 if passed xattr value differs from current value, 0 otherwise.
|
|
*/
|
|
static int evm_xattr_change(struct user_namespace *mnt_userns,
|
|
struct dentry *dentry, const char *xattr_name,
|
|
const void *xattr_value, size_t xattr_value_len)
|
|
{
|
|
char *xattr_data = NULL;
|
|
int rc = 0;
|
|
|
|
if (posix_xattr_acl(xattr_name))
|
|
return evm_xattr_acl_change(mnt_userns, dentry, xattr_name,
|
|
xattr_value, xattr_value_len);
|
|
|
|
rc = vfs_getxattr_alloc(&init_user_ns, dentry, xattr_name, &xattr_data,
|
|
0, GFP_NOFS);
|
|
if (rc < 0)
|
|
return 1;
|
|
|
|
if (rc == xattr_value_len)
|
|
rc = !!memcmp(xattr_value, xattr_data, rc);
|
|
else
|
|
rc = 1;
|
|
|
|
kfree(xattr_data);
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
* 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 unless the EVM signature is immutable.
|
|
*/
|
|
static int evm_protect_xattr(struct user_namespace *mnt_userns,
|
|
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;
|
|
|
|
/* Exception if the HMAC is not going to be calculated. */
|
|
if (evm_hmac_disabled())
|
|
return 0;
|
|
|
|
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:
|
|
/* Exception if the HMAC is not going to be calculated. */
|
|
if (evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL ||
|
|
evm_status == INTEGRITY_UNKNOWN))
|
|
return 0;
|
|
|
|
/*
|
|
* Writing other xattrs is safe for portable signatures, as portable
|
|
* signatures are immutable and can never be updated.
|
|
*/
|
|
if (evm_status == INTEGRITY_FAIL_IMMUTABLE)
|
|
return 0;
|
|
|
|
if (evm_status == INTEGRITY_PASS_IMMUTABLE &&
|
|
!evm_xattr_change(mnt_userns, dentry, xattr_name, xattr_value,
|
|
xattr_value_len))
|
|
return 0;
|
|
|
|
if (evm_status != INTEGRITY_PASS &&
|
|
evm_status != INTEGRITY_PASS_IMMUTABLE)
|
|
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
|
|
* @mnt_userns: user namespace of the idmapped mount
|
|
* @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 user_namespace *mnt_userns, 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;
|
|
|
|
/* Policy permits modification of the protected xattrs even though
|
|
* there's no HMAC key loaded
|
|
*/
|
|
if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
|
|
return 0;
|
|
|
|
if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
|
|
if (!xattr_value_len)
|
|
return -EINVAL;
|
|
if (xattr_data->type != EVM_IMA_XATTR_DIGSIG &&
|
|
xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG)
|
|
return -EPERM;
|
|
}
|
|
return evm_protect_xattr(mnt_userns, dentry, xattr_name, xattr_value,
|
|
xattr_value_len);
|
|
}
|
|
|
|
/**
|
|
* evm_inode_removexattr - protect the EVM extended attribute
|
|
* @mnt_userns: user namespace of the idmapped mount
|
|
* @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 user_namespace *mnt_userns,
|
|
struct dentry *dentry, const char *xattr_name)
|
|
{
|
|
/* Policy permits modification of the protected xattrs even though
|
|
* there's no HMAC key loaded
|
|
*/
|
|
if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
|
|
return 0;
|
|
|
|
return evm_protect_xattr(mnt_userns, 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_revalidate_status - report whether EVM status re-validation is necessary
|
|
* @xattr_name: pointer to the affected extended attribute name
|
|
*
|
|
* Report whether callers of evm_verifyxattr() should re-validate the
|
|
* EVM status.
|
|
*
|
|
* Return true if re-validation is necessary, false otherwise.
|
|
*/
|
|
bool evm_revalidate_status(const char *xattr_name)
|
|
{
|
|
if (!evm_key_loaded())
|
|
return false;
|
|
|
|
/* evm_inode_post_setattr() passes NULL */
|
|
if (!xattr_name)
|
|
return true;
|
|
|
|
if (!evm_protected_xattr(xattr_name) && !posix_xattr_acl(xattr_name) &&
|
|
strcmp(xattr_name, XATTR_NAME_EVM))
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* 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_revalidate_status(xattr_name))
|
|
return;
|
|
|
|
evm_reset_status(dentry->d_inode);
|
|
|
|
if (!strcmp(xattr_name, XATTR_NAME_EVM))
|
|
return;
|
|
|
|
if (!(evm_initialized & EVM_INIT_HMAC))
|
|
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.
|
|
*
|
|
* 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_revalidate_status(xattr_name))
|
|
return;
|
|
|
|
evm_reset_status(dentry->d_inode);
|
|
|
|
if (!strcmp(xattr_name, XATTR_NAME_EVM))
|
|
return;
|
|
|
|
if (!(evm_initialized & EVM_INIT_HMAC))
|
|
return;
|
|
|
|
evm_update_evmxattr(dentry, xattr_name, NULL, 0);
|
|
}
|
|
|
|
static int evm_attr_change(struct dentry *dentry, struct iattr *attr)
|
|
{
|
|
struct inode *inode = d_backing_inode(dentry);
|
|
unsigned int ia_valid = attr->ia_valid;
|
|
|
|
if ((!(ia_valid & ATTR_UID) || uid_eq(attr->ia_uid, inode->i_uid)) &&
|
|
(!(ia_valid & ATTR_GID) || gid_eq(attr->ia_gid, inode->i_gid)) &&
|
|
(!(ia_valid & ATTR_MODE) || attr->ia_mode == inode->i_mode))
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
|
|
/**
|
|
* evm_inode_setattr - prevent updating an invalid EVM extended attribute
|
|
* @dentry: pointer to the affected dentry
|
|
*
|
|
* Permit update of file attributes when files have a valid EVM signature,
|
|
* except in the case of them having an immutable portable signature.
|
|
*/
|
|
int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
|
|
{
|
|
unsigned int ia_valid = attr->ia_valid;
|
|
enum integrity_status evm_status;
|
|
|
|
/* Policy permits modification of the protected attrs even though
|
|
* there's no HMAC key loaded
|
|
*/
|
|
if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
|
|
return 0;
|
|
|
|
if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
|
|
return 0;
|
|
evm_status = evm_verify_current_integrity(dentry);
|
|
/*
|
|
* Writing attrs is safe for portable signatures, as portable signatures
|
|
* are immutable and can never be updated.
|
|
*/
|
|
if ((evm_status == INTEGRITY_PASS) ||
|
|
(evm_status == INTEGRITY_NOXATTRS) ||
|
|
(evm_status == INTEGRITY_FAIL_IMMUTABLE) ||
|
|
(evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL ||
|
|
evm_status == INTEGRITY_UNKNOWN)))
|
|
return 0;
|
|
|
|
if (evm_status == INTEGRITY_PASS_IMMUTABLE &&
|
|
!evm_attr_change(dentry, attr))
|
|
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_revalidate_status(NULL))
|
|
return;
|
|
|
|
evm_reset_status(dentry->d_inode);
|
|
|
|
if (!(evm_initialized & EVM_INIT_HMAC))
|
|
return;
|
|
|
|
if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
|
|
evm_update_evmxattr(dentry, NULL, NULL, 0);
|
|
}
|
|
|
|
/*
|
|
* evm_inode_init_security - initializes security.evm HMAC value
|
|
*/
|
|
int evm_inode_init_security(struct inode *inode,
|
|
const struct xattr *lsm_xattr,
|
|
struct xattr *evm_xattr)
|
|
{
|
|
struct evm_xattr *xattr_data;
|
|
int rc;
|
|
|
|
if (!(evm_initialized & EVM_INIT_HMAC) ||
|
|
!evm_protected_xattr(lsm_xattr->name))
|
|
return 0;
|
|
|
|
xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
|
|
if (!xattr_data)
|
|
return -ENOMEM;
|
|
|
|
xattr_data->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;
|
|
struct list_head *pos, *q;
|
|
|
|
evm_init_config();
|
|
|
|
error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
|
|
if (error)
|
|
goto error;
|
|
|
|
error = evm_init_secfs();
|
|
if (error < 0) {
|
|
pr_info("Error registering secfs\n");
|
|
goto error;
|
|
}
|
|
|
|
error:
|
|
if (error != 0) {
|
|
if (!list_empty(&evm_config_xattrnames)) {
|
|
list_for_each_safe(pos, q, &evm_config_xattrnames)
|
|
list_del(pos);
|
|
}
|
|
}
|
|
|
|
return error;
|
|
}
|
|
|
|
late_initcall(init_evm);
|