Orange Pi5 kernel

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2005-2010 IBM Corporation
 *
 * Author:
 * Mimi Zohar <zohar@us.ibm.com>
 * Kylene Hall <kjhall@us.ibm.com>
 *
 * File: evm_main.c
 *	implements evm_inode_setxattr, evm_inode_post_setxattr,
 *	evm_inode_removexattr, and evm_verifyxattr
 */
 
#include <linux/init.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/hash_info.h>
#include <crypto/algapi.h>
#include "evm.h"
 
int evm_initialized;
 
static const char * const integrity_status_msg[] = {
<------>"pass", "pass_immutable", "fail", "no_label", "no_xattrs", "unknown"
};
int evm_hmac_attrs;
 
static struct xattr_list evm_config_default_xattrnames[] = {
#ifdef CONFIG_SECURITY_SELINUX
<------>{.name = XATTR_NAME_SELINUX},
#endif
#ifdef CONFIG_SECURITY_SMACK
<------>{.name = XATTR_NAME_SMACK},
#ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
<------>{.name = XATTR_NAME_SMACKEXEC},
<------>{.name = XATTR_NAME_SMACKTRANSMUTE},
<------>{.name = XATTR_NAME_SMACKMMAP},
#endif
#endif
#ifdef CONFIG_SECURITY_APPARMOR
<------>{.name = XATTR_NAME_APPARMOR},
#endif
#ifdef CONFIG_IMA_APPRAISE
<------>{.name = XATTR_NAME_IMA},
#endif
<------>{.name = XATTR_NAME_CAPS},
};
 
LIST_HEAD(evm_config_xattrnames);
 
static int evm_fixmode __ro_after_init;
static int __init evm_set_fixmode(char *str)
{
<------>if (strncmp(str, "fix", 3) == 0)
<------><------>evm_fixmode = 1;
<------>else
<------><------>pr_err("invalid \"%s\" mode", str);
 
<------>return 1;
}
__setup("evm=", evm_set_fixmode);
 
static void __init evm_init_config(void)
{
<------>int i, xattrs;
 
<------>xattrs = ARRAY_SIZE(evm_config_default_xattrnames);
 
<------>pr_info("Initialising EVM extended attributes:\n");
<------>for (i = 0; i < xattrs; i++) {
<------><------>pr_info("%s\n", evm_config_default_xattrnames[i].name);
<------><------>list_add_tail(&evm_config_default_xattrnames[i].list,
<------><------><------>      &evm_config_xattrnames);
<------>}
 
#ifdef CONFIG_EVM_ATTR_FSUUID
<------>evm_hmac_attrs |= EVM_ATTR_FSUUID;
#endif
<------>pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
}
 
static bool evm_key_loaded(void)
{
<------>return (bool)(evm_initialized & EVM_KEY_MASK);
}
 
static int evm_find_protected_xattrs(struct dentry *dentry)
{
<------>struct inode *inode = d_backing_inode(dentry);
<------>struct xattr_list *xattr;
<------>int error;
<------>int count = 0;
 
<------>if (!(inode->i_opflags & IOP_XATTR))
<------><------>return -EOPNOTSUPP;
 
<------>list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
<------><------>error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0,
<------><------><------><------>       XATTR_NOSECURITY);
<------><------>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 signature_v2_hdr *hdr;
<------>enum integrity_status evm_status = INTEGRITY_PASS;
<------>struct evm_digest digest;
<------>struct inode *inode;
<------>int rc, xattr_len;
 
<------>if (iint && (iint->evm_status == INTEGRITY_PASS ||
<------><------>     iint->evm_status == INTEGRITY_PASS_IMMUTABLE))
<------><------>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_xattr)) {
<------><------><------>evm_status = INTEGRITY_FAIL;
<------><------><------>goto out;
<------><------>}
 
<------><------>digest.hdr.algo = HASH_ALGO_SHA1;
<------><------>rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
<------><------><------><------>   xattr_value_len, &digest);
<------><------>if (rc)
<------><------><------>break;
<------><------>rc = crypto_memneq(xattr_data->data, digest.digest,
<------><------><------><------>   SHA1_DIGEST_SIZE);
<------><------>if (rc)
<------><------><------>rc = -EINVAL;
<------><------>break;
<------>case EVM_IMA_XATTR_DIGSIG:
<------>case EVM_XATTR_PORTABLE_DIGSIG:
<------><------>/* accept xattr with non-empty signature field */
<------><------>if (xattr_len <= sizeof(struct signature_v2_hdr)) {
<------><------><------>evm_status = INTEGRITY_FAIL;
<------><------><------>goto out;
<------><------>}
 
<------><------>hdr = (struct signature_v2_hdr *)xattr_data;
<------><------>digest.hdr.algo = hdr->hash_algo;
<------><------>rc = evm_calc_hash(dentry, xattr_name, xattr_value,
<------><------><------><------>   xattr_value_len, xattr_data->type, &digest);
<------><------>if (rc)
<------><------><------>break;
<------><------>rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
<------><------><------><------><------>(const char *)xattr_data, xattr_len,
<------><------><------><------><------>digest.digest, digest.hdr.length);
<------><------>if (!rc) {
<------><------><------>inode = d_backing_inode(dentry);
 
<------><------><------>if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) {
<------><------><------><------>if (iint)
<------><------><------><------><------>iint->flags |= EVM_IMMUTABLE_DIGSIG;
<------><------><------><------>evm_status = INTEGRITY_PASS_IMMUTABLE;
<------><------><------>} else if (!IS_RDONLY(inode) &&
<------><------><------><------>   !(inode->i_sb->s_readonly_remount) &&
<------><------><------><------>   !IS_IMMUTABLE(inode)) {
<------><------><------><------>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)
{
<------>int namelen;
<------>int found = 0;
<------>struct xattr_list *xattr;
 
<------>namelen = strlen(req_xattr_name);
<------>list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
<------><------>if ((strlen(xattr->name) == namelen)
<------><------>    && (strncmp(req_xattr_name, xattr->name, namelen) == 0)) {
<------><------><------>found = 1;
<------><------><------>break;
<------><------>}
<------><------>if (strncmp(req_xattr_name,
<------><------><------>    xattr->name + 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_key_loaded() || !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_key_loaded() || !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 unless the EVM signature is immutable.
 */
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;
 
<------>/* 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(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)
{
<------>/* 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(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_key_loaded() || (!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_key_loaded() || !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
 *
 * 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);
<------>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_key_loaded())
<------><------>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);