// 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, evm_verifyxattr, and evm_inode_set_acl.
 */

#define pr_fmt(fmt) "EVM: "fmt

#include <linux/init.h>
#include <linux/audit.h>
#include <linux/xattr.h>
#include <linux/integrity.h>
#include <linux/evm.h>
#include <linux/magic.h>
#include <linux/posix_acl_xattr.h>
#include <linux/lsm_hooks.h>

#include <crypto/hash.h>
#include <crypto/hash_info.h>
#include <crypto/utils.h>
#include "evm.h"

int evm_initialized;

static const char * const integrity_status_msg[] = {
        "pass", "pass_immutable", "fail", "fail_immutable", "no_label",
        "no_xattrs", "unknown"
};
int evm_hmac_attrs;

static struct xattr_list evm_config_default_xattrnames[] = {
        {
         .name = XATTR_NAME_SELINUX,
         .enabled = IS_ENABLED(CONFIG_SECURITY_SELINUX)
        },
        {
         .name = XATTR_NAME_SMACK,
         .enabled = IS_ENABLED(CONFIG_SECURITY_SMACK)
        },
        {
         .name = XATTR_NAME_SMACKEXEC,
         .enabled = IS_ENABLED(CONFIG_EVM_EXTRA_SMACK_XATTRS)
        },
        {
         .name = XATTR_NAME_SMACKTRANSMUTE,
         .enabled = IS_ENABLED(CONFIG_EVM_EXTRA_SMACK_XATTRS)
        },
        {
         .name = XATTR_NAME_SMACKMMAP,
         .enabled = IS_ENABLED(CONFIG_EVM_EXTRA_SMACK_XATTRS)
        },
        {
         .name = XATTR_NAME_APPARMOR,
         .enabled = IS_ENABLED(CONFIG_SECURITY_APPARMOR)
        },
        {
         .name = XATTR_NAME_IMA,
         .enabled = IS_ENABLED(CONFIG_IMA_APPRAISE)
        },
        {
         .name = XATTR_NAME_CAPS,
         .enabled = true
        },
};

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%s\n", evm_config_default_xattrnames[i].name,
                        !evm_config_default_xattrnames[i].enabled ?
                        " (disabled)" : "");
                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);
}

/*
 * This function determines whether or not it is safe to ignore verification
 * errors, based on the ability of EVM to calculate HMACs. If the HMAC key
 * is not loaded, and it cannot be loaded in the future due to the
 * EVM_SETUP_COMPLETE initialization flag, allowing an operation despite the
 * attrs/xattrs being found invalid will not make them valid.
 */
static bool evm_hmac_disabled(void)
{
        if (evm_initialized & EVM_INIT_HMAC)
                return false;

        if (!(evm_initialized & EVM_SETUP_COMPLETE))
                return false;

        return true;
}

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);
                if (error < 0) {
                        if (error == -ENODATA)
                                continue;
                        return error;
                }
                count++;
        }

        return count;
}

static int is_unsupported_hmac_fs(struct dentry *dentry)
{
        struct inode *inode = d_backing_inode(dentry);

        if (inode->i_sb->s_iflags & SB_I_EVM_HMAC_UNSUPPORTED) {
                pr_info_once("%s not supported\n", inode->i_sb->s_type->name);
                return 1;
        }
        return 0;
}

/*
 * 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 previously 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 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 = d_backing_inode(dentry);
        struct evm_iint_cache *iint = evm_iint_inode(inode);
        int rc, xattr_len, evm_immutable = 0;

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

        /*
         * On unsupported filesystems without EVM_INIT_X509 enabled, skip
         * signature verification.
         */
        if (!(evm_initialized & EVM_INIT_X509) &&
            is_unsupported_hmac_fs(dentry))
                return INTEGRITY_UNKNOWN;

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

        /* first need to know the sig type */
        rc = vfs_getxattr_alloc(&nop_mnt_idmap, 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, iint);
                if (rc)
                        break;
                rc = crypto_memneq(xattr_data->data, digest.digest,
                                   SHA1_DIGEST_SIZE);
                if (rc)
                        rc = -EINVAL;
                break;
        case EVM_XATTR_PORTABLE_DIGSIG:
                evm_immutable = 1;
                fallthrough;
        case EVM_IMA_XATTR_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,
                                   iint);
                if (rc)
                        break;
                rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
                                        (const char *)xattr_data, xattr_len,
                                        digest.digest, digest.hdr.length);
                if (!rc) {
                        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) &&
                                   !is_unsupported_hmac_fs(dentry)) {
                                evm_update_evmxattr(dentry, xattr_name,
                                                    xattr_value,
                                                    xattr_value_len);
                        }
                }
                break;
        default:
                rc = -EINVAL;
                break;
        }

        if (rc) {
                if (rc == -ENODATA)
                        evm_status = INTEGRITY_NOXATTRS;
                else if (evm_immutable)
                        evm_status = INTEGRITY_FAIL_IMMUTABLE;
                else
                        evm_status = INTEGRITY_FAIL;
        }
        pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length,
                  digest.digest);
out:
        if (iint)
                iint->evm_status = evm_status;
        kfree(xattr_data);
        return evm_status;
}

static int evm_protected_xattr_common(const char *req_xattr_name,
                                      bool all_xattrs)
{
        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 (!all_xattrs && !xattr->enabled)
                        continue;

                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;
}

int evm_protected_xattr(const char *req_xattr_name)
{
        return evm_protected_xattr_common(req_xattr_name, false);
}

int evm_protected_xattr_if_enabled(const char *req_xattr_name)
{
        return evm_protected_xattr_common(req_xattr_name, true);
}

/**
 * evm_read_protected_xattrs - read EVM protected xattr names, lengths, values
 * @dentry: dentry of the read xattrs
 * @buffer: buffer xattr names, lengths or values are copied to
 * @buffer_size: size of buffer
 * @type: n: names, l: lengths, v: values
 * @canonical_fmt: data format (true: little endian, false: native format)
 *
 * Read protected xattr names (separated by |), lengths (u32) or values for a
 * given dentry and return the total size of copied data. If buffer is NULL,
 * just return the total size.
 *
 * Returns the total size on success, a negative value on error.
 */
int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer,
                              int buffer_size, char type, bool canonical_fmt)
{
        struct xattr_list *xattr;
        int rc, size, total_size = 0;

        list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
                rc = __vfs_getxattr(dentry, d_backing_inode(dentry),
                                    xattr->name, NULL, 0);
                if (rc < 0 && rc == -ENODATA)
                        continue;
                else if (rc < 0)
                        return rc;

                switch (type) {
                case 'n':
                        size = strlen(xattr->name) + 1;
                        if (buffer) {
                                if (total_size)
                                        *(buffer + total_size - 1) = '|';

                                memcpy(buffer + total_size, xattr->name, size);
                        }
                        break;
                case 'l':
                        size = sizeof(u32);
                        if (buffer) {
                                if (canonical_fmt)
                                        rc = (__force int)cpu_to_le32(rc);

                                *(u32 *)(buffer + total_size) = rc;
                        }
                        break;
                case 'v':
                        size = rc;
                        if (buffer) {
                                rc = __vfs_getxattr(dentry,
                                        d_backing_inode(dentry), xattr->name,
                                        buffer + total_size,
                                        buffer_size - total_size);
                                if (rc < 0)
                                        return rc;
                        }
                        break;
                default:
                        return -EINVAL;
                }

                total_size += size;
        }

        return total_size;
}

/**
 * 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)
{
        if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
                return INTEGRITY_UNKNOWN;

        return evm_verify_hmac(dentry, xattr_name, xattr_value,
                                 xattr_value_len);
}
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 INTEGRITY_PASS;
        return evm_verify_hmac(dentry, NULL, NULL, 0);
}

/*
 * evm_xattr_change - check if passed xattr value differs from current value
 * @idmap: idmap of the mount
 * @dentry: pointer to the affected dentry
 * @xattr_name: requested xattr
 * @xattr_value: requested xattr value
 * @xattr_value_len: requested xattr value length
 *
 * Check if passed xattr value differs from current value.
 *
 * Returns 1 if passed xattr value differs from current value, 0 otherwise.
 */
static int evm_xattr_change(struct mnt_idmap *idmap,
                            struct dentry *dentry, const char *xattr_name,
                            const void *xattr_value, size_t xattr_value_len)
{
        char *xattr_data = NULL;
        int rc = 0;

        rc = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, xattr_name, &xattr_data,
                                0, GFP_NOFS);
        if (rc < 0) {
                rc = 1;
                goto out;
        }

        if (rc == xattr_value_len)
                rc = !!memcmp(xattr_value, xattr_data, rc);
        else
                rc = 1;

out:
        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 mnt_idmap *idmap,
                             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;
                if (is_unsupported_hmac_fs(dentry))
                        return -EPERM;
        } else if (!evm_protected_xattr(xattr_name)) {
                if (!posix_xattr_acl(xattr_name))
                        return 0;
                if (is_unsupported_hmac_fs(dentry))
                        return 0;

                evm_status = evm_verify_current_integrity(dentry);
                if ((evm_status == INTEGRITY_PASS) ||
                    (evm_status == INTEGRITY_NOXATTRS))
                        return 0;
                goto out;
        } else if (is_unsupported_hmac_fs(dentry))
                return 0;

        evm_status = evm_verify_current_integrity(dentry);
        if (evm_status == INTEGRITY_NOXATTRS) {
                struct evm_iint_cache *iint;

                /* Exception if the HMAC is not going to be calculated. */
                if (evm_hmac_disabled())
                        return 0;

                iint = evm_iint_inode(d_backing_inode(dentry));
                if (iint && (iint->flags & EVM_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(idmap, 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
 * @idmap: idmap of the 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
 * @flags: flags to pass into filesystem operations
 *
 * 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.
 */
static int evm_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
                              const char *xattr_name, const void *xattr_value,
                              size_t xattr_value_len, int flags)
{
        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(idmap, dentry, xattr_name, xattr_value,
                                 xattr_value_len);
}

/**
 * evm_inode_removexattr - protect the EVM extended attribute
 * @idmap: idmap of the 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.
 */
static int evm_inode_removexattr(struct mnt_idmap *idmap, 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(idmap, dentry, xattr_name, NULL, 0);
}

#ifdef CONFIG_FS_POSIX_ACL
static int evm_inode_set_acl_change(struct mnt_idmap *idmap,
                                    struct dentry *dentry, const char *name,
                                    struct posix_acl *kacl)
{
        int rc;

        umode_t mode;
        struct inode *inode = d_backing_inode(dentry);

        if (!kacl)
                return 1;

        rc = posix_acl_update_mode(idmap, inode, &mode, &kacl);
        if (rc || (inode->i_mode != mode))
                return 1;

        return 0;
}
#else
static inline int evm_inode_set_acl_change(struct mnt_idmap *idmap,
                                           struct dentry *dentry,
                                           const char *name,
                                           struct posix_acl *kacl)
{
        return 0;
}
#endif

/**
 * evm_inode_set_acl - protect the EVM extended attribute from posix acls
 * @idmap: idmap of the idmapped mount
 * @dentry: pointer to the affected dentry
 * @acl_name: name of the posix acl
 * @kacl: pointer to the posix acls
 *
 * Prevent modifying posix acls causing the EVM HMAC to be re-calculated
 * and 'security.evm' xattr updated, unless the existing 'security.evm' is
 * valid.
 *
 * Return: zero on success, -EPERM on failure.
 */
static int evm_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
                             const char *acl_name, struct posix_acl *kacl)
{
        enum integrity_status evm_status;

        /* Policy permits modification of the protected xattrs even though
         * there's no HMAC key loaded
         */
        if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
                return 0;

        evm_status = evm_verify_current_integrity(dentry);
        if ((evm_status == INTEGRITY_PASS) ||
            (evm_status == INTEGRITY_NOXATTRS))
                return 0;

        /* 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_inode_set_acl_change(idmap, dentry, acl_name, kacl))
                return 0;

        if (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 -EPERM;
}

/**
 * evm_inode_remove_acl - Protect the EVM extended attribute from posix acls
 * @idmap: idmap of the mount
 * @dentry: pointer to the affected dentry
 * @acl_name: name of the posix acl
 *
 * Prevent removing posix acls causing the EVM HMAC to be re-calculated
 * and 'security.evm' xattr updated, unless the existing 'security.evm' is
 * valid.
 *
 * Return: zero on success, -EPERM on failure.
 */
static int evm_inode_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
                                const char *acl_name)
{
        return evm_inode_set_acl(idmap, dentry, acl_name, NULL);
}

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

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

/**
 * evm_metadata_changed: Detect changes to the metadata
 * @inode: a file's inode
 * @metadata_inode: metadata inode
 *
 * On a stacked filesystem detect whether the metadata has changed. If this is
 * the case reset the evm_status associated with the inode that represents the
 * file.
 */
bool evm_metadata_changed(struct inode *inode, struct inode *metadata_inode)
{
        struct evm_iint_cache *iint = evm_iint_inode(inode);
        bool ret = false;

        if (iint) {
                ret = (!IS_I_VERSION(metadata_inode) ||
                       integrity_inode_attrs_changed(&iint->metadata_inode,
                                                     metadata_inode));
                if (ret)
                        iint->evm_status = INTEGRITY_UNKNOWN;
        }

        return ret;
}

/**
 * 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
 * @flags: flags to pass into filesystem operations
 *
 * 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.
 */
static void evm_inode_post_setxattr(struct dentry *dentry,
                                    const char *xattr_name,
                                    const void *xattr_value,
                                    size_t xattr_value_len,
                                    int flags)
{
        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;

        if (is_unsupported_hmac_fs(dentry))
                return;

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

/**
 * evm_inode_post_set_acl - Update the EVM extended attribute from posix acls
 * @dentry: pointer to the affected dentry
 * @acl_name: name of the posix acl
 * @kacl: pointer to the posix acls
 *
 * Update the 'security.evm' xattr with the EVM HMAC re-calculated after setting
 * posix acls.
 */
static void evm_inode_post_set_acl(struct dentry *dentry, const char *acl_name,
                                   struct posix_acl *kacl)
{
        return evm_inode_post_setxattr(dentry, acl_name, NULL, 0, 0);
}

/**
 * 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.
 */
static 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);
}

/**
 * evm_inode_post_remove_acl - Update the EVM extended attribute from posix acls
 * @idmap: idmap of the mount
 * @dentry: pointer to the affected dentry
 * @acl_name: name of the posix acl
 *
 * Update the 'security.evm' xattr with the EVM HMAC re-calculated after
 * removing posix acls.
 */
static inline void evm_inode_post_remove_acl(struct mnt_idmap *idmap,
                                             struct dentry *dentry,
                                             const char *acl_name)
{
        evm_inode_post_removexattr(dentry, acl_name);
}

static int evm_attr_change(struct mnt_idmap *idmap,
                           struct dentry *dentry, struct iattr *attr)
{
        struct inode *inode = d_backing_inode(dentry);
        unsigned int ia_valid = attr->ia_valid;

        if (!i_uid_needs_update(idmap, attr, inode) &&
            !i_gid_needs_update(idmap, attr, inode) &&
            (!(ia_valid & ATTR_MODE) || attr->ia_mode == inode->i_mode))
                return 0;

        return 1;
}

/**
 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
 * @idmap: idmap of the mount
 * @dentry: pointer to the affected dentry
 * @attr: iattr structure containing the new file attributes
 *
 * Permit update of file attributes when files have a valid EVM signature,
 * except in the case of them having an immutable portable signature.
 */
static int evm_inode_setattr(struct mnt_idmap *idmap, 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 (is_unsupported_hmac_fs(dentry))
                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(idmap, 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
 * @idmap: idmap of the idmapped mount
 * @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.
 */
static void evm_inode_post_setattr(struct mnt_idmap *idmap,
                                   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 (is_unsupported_hmac_fs(dentry))
                return;

        if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
                evm_update_evmxattr(dentry, NULL, NULL, 0);
}

static int evm_inode_copy_up_xattr(struct dentry *src, const char *name)
{
        struct evm_ima_xattr_data *xattr_data = NULL;
        int rc;

        if (strcmp(name, XATTR_NAME_EVM) != 0)
                return -EOPNOTSUPP;

        /* first need to know the sig type */
        rc = vfs_getxattr_alloc(&nop_mnt_idmap, src, XATTR_NAME_EVM,
                                (char **)&xattr_data, 0, GFP_NOFS);
        if (rc <= 0)
                return -EPERM;

        if (rc < offsetof(struct evm_ima_xattr_data, type) +
                 sizeof(xattr_data->type))
                return -EPERM;

        switch (xattr_data->type) {
        case EVM_XATTR_PORTABLE_DIGSIG:
                rc = 0; /* allow copy-up */
                break;
        case EVM_XATTR_HMAC:
        case EVM_IMA_XATTR_DIGSIG:
        default:
                rc = -ECANCELED; /* discard */
        }

        kfree(xattr_data);
        return rc;
}

/*
 * evm_inode_init_security - initializes security.evm HMAC value
 */
int evm_inode_init_security(struct inode *inode, struct inode *dir,
                            const struct qstr *qstr, struct xattr *xattrs,
                            int *xattr_count)
{
        struct evm_xattr *xattr_data;
        struct xattr *xattr, *evm_xattr;
        bool evm_protected_xattrs = false;
        int rc;

        if (!(evm_initialized & EVM_INIT_HMAC) || !xattrs)
                return 0;

        /*
         * security_inode_init_security() makes sure that the xattrs array is
         * contiguous, there is enough space for security.evm, and that there is
         * a terminator at the end of the array.
         */
        for (xattr = xattrs; xattr->name; xattr++) {
                if (evm_protected_xattr(xattr->name))
                        evm_protected_xattrs = true;
        }

        /* EVM xattr not needed. */
        if (!evm_protected_xattrs)
                return 0;

        evm_xattr = lsm_get_xattr_slot(xattrs, xattr_count);
        /*
         * Array terminator (xattr name = NULL) must be the first non-filled
         * xattr slot.
         */
        WARN_ONCE(evm_xattr != xattr,
                  "%s: xattrs terminator is not the first non-filled slot\n",
                  __func__);

        xattr_data = kzalloc_obj(*xattr_data, GFP_NOFS);
        if (!xattr_data)
                return -ENOMEM;

        xattr_data->data.type = EVM_XATTR_HMAC;
        rc = evm_init_hmac(inode, xattrs, 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 evm_inode_alloc_security(struct inode *inode)
{
        struct evm_iint_cache *iint = evm_iint_inode(inode);

        /* Called by security_inode_alloc(), it cannot be NULL. */
        iint->flags = 0UL;
        iint->evm_status = INTEGRITY_UNKNOWN;

        return 0;
}

static void evm_file_release(struct file *file)
{
        struct inode *inode = file_inode(file);
        struct evm_iint_cache *iint = evm_iint_inode(inode);
        fmode_t mode = file->f_mode;

        if (!S_ISREG(inode->i_mode) || !(mode & FMODE_WRITE))
                return;

        if (iint && iint->flags & EVM_NEW_FILE &&
            atomic_read(&inode->i_writecount) == 1)
                iint->flags &= ~EVM_NEW_FILE;
}

static void evm_post_path_mknod(struct mnt_idmap *idmap, struct dentry *dentry)
{
        struct inode *inode = d_backing_inode(dentry);
        struct evm_iint_cache *iint = evm_iint_inode(inode);

        if (!S_ISREG(inode->i_mode))
                return;

        if (iint)
                iint->flags |= EVM_NEW_FILE;
}

#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;
}

static struct security_hook_list evm_hooks[] __ro_after_init = {
        LSM_HOOK_INIT(inode_setattr, evm_inode_setattr),
        LSM_HOOK_INIT(inode_post_setattr, evm_inode_post_setattr),
        LSM_HOOK_INIT(inode_copy_up_xattr, evm_inode_copy_up_xattr),
        LSM_HOOK_INIT(inode_setxattr, evm_inode_setxattr),
        LSM_HOOK_INIT(inode_post_setxattr, evm_inode_post_setxattr),
        LSM_HOOK_INIT(inode_set_acl, evm_inode_set_acl),
        LSM_HOOK_INIT(inode_post_set_acl, evm_inode_post_set_acl),
        LSM_HOOK_INIT(inode_remove_acl, evm_inode_remove_acl),
        LSM_HOOK_INIT(inode_post_remove_acl, evm_inode_post_remove_acl),
        LSM_HOOK_INIT(inode_removexattr, evm_inode_removexattr),
        LSM_HOOK_INIT(inode_post_removexattr, evm_inode_post_removexattr),
        LSM_HOOK_INIT(inode_init_security, evm_inode_init_security),
        LSM_HOOK_INIT(inode_alloc_security, evm_inode_alloc_security),
        LSM_HOOK_INIT(file_release, evm_file_release),
        LSM_HOOK_INIT(path_post_mknod, evm_post_path_mknod),
};

static const struct lsm_id evm_lsmid = {
        .name = "evm",
        .id = LSM_ID_EVM,
};

static int __init init_evm_lsm(void)
{
        security_add_hooks(evm_hooks, ARRAY_SIZE(evm_hooks), &evm_lsmid);
        return 0;
}

struct lsm_blob_sizes evm_blob_sizes __ro_after_init = {
        .lbs_inode = sizeof(struct evm_iint_cache),
        .lbs_xattr_count = 1,
};

DEFINE_LSM(evm) = {
        .id = &evm_lsmid,
        .init = init_evm_lsm,
        .order = LSM_ORDER_LAST,
        .blobs = &evm_blob_sizes,
        .initcall_late = init_evm,
};