// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2011 IBM Corporation
 *
 * Author:
 * Mimi Zohar <zohar@us.ibm.com>
 */
#include <linux/module.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/binfmts.h>
#include <linux/fs.h>
#include <linux/xattr.h>
#include <linux/magic.h>
#include <linux/ima.h>
#include <linux/evm.h>
#include <linux/fsverity.h>
#include <keys/system_keyring.h>
#include <uapi/linux/fsverity.h>

#include "ima.h"

#ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
static char *ima_appraise_cmdline_default __initdata;
core_param(ima_appraise, ima_appraise_cmdline_default, charp, 0);

void __init ima_appraise_parse_cmdline(void)
{
        const char *str = ima_appraise_cmdline_default;
        bool sb_state = arch_ima_get_secureboot();
        int appraisal_state = ima_appraise;

        if (!str)
                return;

        if (strncmp(str, "off", 3) == 0)
                appraisal_state = 0;
        else if (strncmp(str, "log", 3) == 0)
                appraisal_state = IMA_APPRAISE_LOG;
        else if (strncmp(str, "fix", 3) == 0)
                appraisal_state = IMA_APPRAISE_FIX;
        else if (strncmp(str, "enforce", 7) == 0)
                appraisal_state = IMA_APPRAISE_ENFORCE;
        else
                pr_err("invalid \"%s\" appraise option", str);

        /* If appraisal state was changed, but secure boot is enabled,
         * keep its default */
        if (sb_state) {
                if (!(appraisal_state & IMA_APPRAISE_ENFORCE))
                        pr_info("Secure boot enabled: ignoring ima_appraise=%s option",
                                str);
        } else {
                ima_appraise = appraisal_state;
        }
}
#endif

/*
 * is_ima_appraise_enabled - return appraise status
 *
 * Only return enabled, if not in ima_appraise="fix" or "log" modes.
 */
bool is_ima_appraise_enabled(void)
{
        return ima_appraise & IMA_APPRAISE_ENFORCE;
}

/*
 * ima_must_appraise - set appraise flag
 *
 * Return 1 to appraise or hash
 */
int ima_must_appraise(struct mnt_idmap *idmap, struct inode *inode,
                      int mask, enum ima_hooks func)
{
        struct lsm_prop prop;

        if (!ima_appraise)
                return 0;

        security_current_getlsmprop_subj(&prop);
        return ima_match_policy(idmap, inode, current_cred(), &prop,
                                func, mask, IMA_APPRAISE | IMA_HASH, NULL,
                                NULL, NULL, NULL);
}

static int ima_fix_xattr(struct dentry *dentry, struct ima_iint_cache *iint)
{
        int rc, offset;
        u8 algo = iint->ima_hash->algo;

        if (algo <= HASH_ALGO_SHA1) {
                offset = 1;
                iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST;
        } else {
                offset = 0;
                iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG;
                iint->ima_hash->xattr.ng.algo = algo;
        }
        rc = __vfs_setxattr_noperm(&nop_mnt_idmap, dentry, XATTR_NAME_IMA,
                                   &iint->ima_hash->xattr.data[offset],
                                   (sizeof(iint->ima_hash->xattr) - offset) +
                                   iint->ima_hash->length, 0);
        return rc;
}

/* Return specific func appraised cached result */
enum integrity_status ima_get_cache_status(struct ima_iint_cache *iint,
                                           enum ima_hooks func)
{
        switch (func) {
        case MMAP_CHECK:
        case MMAP_CHECK_REQPROT:
                return iint->ima_mmap_status;
        case BPRM_CHECK:
                return iint->ima_bprm_status;
        case CREDS_CHECK:
                return iint->ima_creds_status;
        case FILE_CHECK:
        case POST_SETATTR:
                return iint->ima_file_status;
        case MODULE_CHECK ... MAX_CHECK - 1:
        default:
                return iint->ima_read_status;
        }
}

static void ima_set_cache_status(struct ima_iint_cache *iint,
                                 enum ima_hooks func,
                                 enum integrity_status status)
{
        switch (func) {
        case MMAP_CHECK:
        case MMAP_CHECK_REQPROT:
                iint->ima_mmap_status = status;
                break;
        case BPRM_CHECK:
                iint->ima_bprm_status = status;
                break;
        case CREDS_CHECK:
                iint->ima_creds_status = status;
                break;
        case FILE_CHECK:
        case POST_SETATTR:
                iint->ima_file_status = status;
                break;
        case MODULE_CHECK ... MAX_CHECK - 1:
        default:
                iint->ima_read_status = status;
                break;
        }
}

static void ima_cache_flags(struct ima_iint_cache *iint, enum ima_hooks func)
{
        switch (func) {
        case MMAP_CHECK:
        case MMAP_CHECK_REQPROT:
                iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
                break;
        case BPRM_CHECK:
                iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
                break;
        case CREDS_CHECK:
                iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED);
                break;
        case FILE_CHECK:
        case POST_SETATTR:
                iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
                break;
        case MODULE_CHECK ... MAX_CHECK - 1:
        default:
                iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED);
                break;
        }
}

enum hash_algo ima_get_hash_algo(const struct evm_ima_xattr_data *xattr_value,
                                 int xattr_len)
{
        struct signature_v2_hdr *sig;
        enum hash_algo ret;

        if (!xattr_value || xattr_len < 2)
                /* return default hash algo */
                return ima_hash_algo;

        switch (xattr_value->type) {
        case IMA_VERITY_DIGSIG:
                sig = (typeof(sig))xattr_value;
                if (sig->version != 3 || xattr_len <= sizeof(*sig) ||
                    sig->hash_algo >= HASH_ALGO__LAST)
                        return ima_hash_algo;
                return sig->hash_algo;
        case EVM_IMA_XATTR_DIGSIG:
                sig = (typeof(sig))xattr_value;
                if (sig->version != 2 || xattr_len <= sizeof(*sig)
                    || sig->hash_algo >= HASH_ALGO__LAST)
                        return ima_hash_algo;
                return sig->hash_algo;
        case IMA_XATTR_DIGEST_NG:
                /* first byte contains algorithm id */
                ret = xattr_value->data[0];
                if (ret < HASH_ALGO__LAST)
                        return ret;
                break;
        case IMA_XATTR_DIGEST:
                /* this is for backward compatibility */
                if (xattr_len == 21) {
                        unsigned int zero = 0;
                        if (!memcmp(&xattr_value->data[16], &zero, 4))
                                return HASH_ALGO_MD5;
                        else
                                return HASH_ALGO_SHA1;
                } else if (xattr_len == 17)
                        return HASH_ALGO_MD5;
                break;
        }

        /* return default hash algo */
        return ima_hash_algo;
}

int ima_read_xattr(struct dentry *dentry,
                   struct evm_ima_xattr_data **xattr_value, int xattr_len)
{
        int ret;

        ret = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, XATTR_NAME_IMA,
                                 (char **)xattr_value, xattr_len, GFP_NOFS);
        if (ret == -EOPNOTSUPP)
                ret = 0;
        return ret;
}

/*
 * calc_file_id_hash - calculate the hash of the ima_file_id struct data
 * @type: xattr type [enum evm_ima_xattr_type]
 * @algo: hash algorithm [enum hash_algo]
 * @digest: pointer to the digest to be hashed
 * @hash: (out) pointer to the hash
 *
 * IMA signature version 3 disambiguates the data that is signed by
 * indirectly signing the hash of the ima_file_id structure data.
 *
 * Signing the ima_file_id struct is currently only supported for
 * IMA_VERITY_DIGSIG type xattrs.
 *
 * Return 0 on success, error code otherwise.
 */
static int calc_file_id_hash(enum evm_ima_xattr_type type,
                             enum hash_algo algo, const u8 *digest,
                             struct ima_digest_data *hash)
{
        struct ima_file_id file_id = {
                .hash_type = IMA_VERITY_DIGSIG, .hash_algorithm = algo};
        unsigned int unused = HASH_MAX_DIGESTSIZE - hash_digest_size[algo];

        if (type != IMA_VERITY_DIGSIG)
                return -EINVAL;

        memcpy(file_id.hash, digest, hash_digest_size[algo]);

        hash->algo = algo;
        hash->length = hash_digest_size[algo];

        return ima_calc_buffer_hash(&file_id, sizeof(file_id) - unused, hash);
}

/*
 * xattr_verify - verify xattr digest or signature
 *
 * Verify whether the hash or signature matches the file contents.
 *
 * Return 0 on success, error code otherwise.
 */
static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
                        struct evm_ima_xattr_data *xattr_value, int xattr_len,
                        enum integrity_status *status, const char **cause)
{
        struct ima_max_digest_data hash;
        struct signature_v2_hdr *sig;
        int rc = -EINVAL, hash_start = 0;
        int mask;

        switch (xattr_value->type) {
        case IMA_XATTR_DIGEST_NG:
                /* first byte contains algorithm id */
                hash_start = 1;
                fallthrough;
        case IMA_XATTR_DIGEST:
                if (*status != INTEGRITY_PASS_IMMUTABLE) {
                        if (iint->flags & IMA_DIGSIG_REQUIRED) {
                                if (iint->flags & IMA_VERITY_REQUIRED)
                                        *cause = "verity-signature-required";
                                else
                                        *cause = "IMA-signature-required";
                                *status = INTEGRITY_FAIL;
                                break;
                        }
                        clear_bit(IMA_DIGSIG, &iint->atomic_flags);
                } else {
                        set_bit(IMA_DIGSIG, &iint->atomic_flags);
                }
                if (xattr_len - sizeof(xattr_value->type) - hash_start >=
                                iint->ima_hash->length)
                        /*
                         * xattr length may be longer. md5 hash in previous
                         * version occupied 20 bytes in xattr, instead of 16
                         */
                        rc = memcmp(&xattr_value->data[hash_start],
                                    iint->ima_hash->digest,
                                    iint->ima_hash->length);
                else
                        rc = -EINVAL;
                if (rc) {
                        *cause = "invalid-hash";
                        *status = INTEGRITY_FAIL;
                        break;
                }
                *status = INTEGRITY_PASS;
                break;
        case EVM_IMA_XATTR_DIGSIG:
                set_bit(IMA_DIGSIG, &iint->atomic_flags);

                mask = IMA_DIGSIG_REQUIRED | IMA_VERITY_REQUIRED;
                if ((iint->flags & mask) == mask) {
                        *cause = "verity-signature-required";
                        *status = INTEGRITY_FAIL;
                        break;
                }

                sig = (typeof(sig))xattr_value;
                if (sig->version >= 3) {
                        *cause = "invalid-signature-version";
                        *status = INTEGRITY_FAIL;
                        break;
                }
                rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
                                             (const char *)xattr_value,
                                             xattr_len,
                                             iint->ima_hash->digest,
                                             iint->ima_hash->length);
                if (rc == -EOPNOTSUPP) {
                        *status = INTEGRITY_UNKNOWN;
                        break;
                }
                if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
                    func == KEXEC_KERNEL_CHECK)
                        rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
                                                     (const char *)xattr_value,
                                                     xattr_len,
                                                     iint->ima_hash->digest,
                                                     iint->ima_hash->length);
                if (rc) {
                        *cause = "invalid-signature";
                        *status = INTEGRITY_FAIL;
                } else {
                        *status = INTEGRITY_PASS;
                }
                break;
        case IMA_VERITY_DIGSIG:
                set_bit(IMA_DIGSIG, &iint->atomic_flags);

                if (iint->flags & IMA_DIGSIG_REQUIRED) {
                        if (!(iint->flags & IMA_VERITY_REQUIRED)) {
                                *cause = "IMA-signature-required";
                                *status = INTEGRITY_FAIL;
                                break;
                        }
                }

                sig = (typeof(sig))xattr_value;
                if (sig->version != 3) {
                        *cause = "invalid-signature-version";
                        *status = INTEGRITY_FAIL;
                        break;
                }

                rc = calc_file_id_hash(IMA_VERITY_DIGSIG, iint->ima_hash->algo,
                                       iint->ima_hash->digest,
                                       container_of(&hash.hdr,
                                               struct ima_digest_data, hdr));
                if (rc) {
                        *cause = "sigv3-hashing-error";
                        *status = INTEGRITY_FAIL;
                        break;
                }

                rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
                                             (const char *)xattr_value,
                                             xattr_len, hash.digest,
                                             hash.hdr.length);
                if (rc) {
                        *cause = "invalid-verity-signature";
                        *status = INTEGRITY_FAIL;
                } else {
                        *status = INTEGRITY_PASS;
                }

                break;
        default:
                *status = INTEGRITY_UNKNOWN;
                *cause = "unknown-ima-data";
                break;
        }

        return rc;
}

/*
 * modsig_verify - verify modsig signature
 *
 * Verify whether the signature matches the file contents.
 *
 * Return 0 on success, error code otherwise.
 */
static int modsig_verify(enum ima_hooks func, const struct modsig *modsig,
                         enum integrity_status *status, const char **cause)
{
        int rc;

        rc = integrity_modsig_verify(INTEGRITY_KEYRING_IMA, modsig);
        if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
            func == KEXEC_KERNEL_CHECK)
                rc = integrity_modsig_verify(INTEGRITY_KEYRING_PLATFORM,
                                             modsig);
        if (rc) {
                *cause = "invalid-signature";
                *status = INTEGRITY_FAIL;
        } else {
                *status = INTEGRITY_PASS;
        }

        return rc;
}

/*
 * ima_check_blacklist - determine if the binary is blacklisted.
 *
 * Add the hash of the blacklisted binary to the measurement list, based
 * on policy.
 *
 * Returns -EPERM if the hash is blacklisted.
 */
int ima_check_blacklist(struct ima_iint_cache *iint,
                        const struct modsig *modsig, int pcr)
{
        enum hash_algo hash_algo;
        const u8 *digest = NULL;
        u32 digestsize = 0;
        int rc = 0;

        if (!(iint->flags & IMA_CHECK_BLACKLIST))
                return 0;

        if (iint->flags & IMA_MODSIG_ALLOWED && modsig) {
                ima_get_modsig_digest(modsig, &hash_algo, &digest, &digestsize);

                rc = is_binary_blacklisted(digest, digestsize);
        } else if (iint->flags & IMA_DIGSIG_REQUIRED && iint->ima_hash)
                rc = is_binary_blacklisted(iint->ima_hash->digest, iint->ima_hash->length);

        if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
                process_buffer_measurement(&nop_mnt_idmap, NULL, digest, digestsize,
                                           "blacklisted-hash", NONE,
                                           pcr, NULL, false, NULL, 0);

        return rc;
}

/*
 * ima_appraise_measurement - appraise file measurement
 *
 * Call evm_verifyxattr() to verify the integrity of 'security.ima'.
 * Assuming success, compare the xattr hash with the collected measurement.
 *
 * Return 0 on success, error code otherwise
 */
int ima_appraise_measurement(enum ima_hooks func, struct ima_iint_cache *iint,
                             struct file *file, const unsigned char *filename,
                             struct evm_ima_xattr_data *xattr_value,
                             int xattr_len, const struct modsig *modsig,
                             bool bprm_is_check)
{
        static const char op[] = "appraise_data";
        int audit_msgno = AUDIT_INTEGRITY_DATA;
        const char *cause = "unknown";
        struct dentry *dentry = file_dentry(file);
        struct inode *inode = d_backing_inode(dentry);
        enum integrity_status status = INTEGRITY_UNKNOWN;
        int rc = xattr_len;
        bool try_modsig = iint->flags & IMA_MODSIG_ALLOWED && modsig;

        /* If not appraising a modsig, we need an xattr. */
        if (!(inode->i_opflags & IOP_XATTR) && !try_modsig)
                return INTEGRITY_UNKNOWN;

        /*
         * Unlike any of the other LSM hooks where the kernel enforces file
         * integrity, enforcing file integrity for the bprm_creds_for_exec()
         * LSM hook with the AT_EXECVE_CHECK flag is left up to the discretion
         * of the script interpreter(userspace). Differentiate kernel and
         * userspace enforced integrity audit messages.
         */
        if (bprm_is_check)
                audit_msgno = AUDIT_INTEGRITY_USERSPACE;

        /* If reading the xattr failed and there's no modsig, error out. */
        if (rc <= 0 && !try_modsig) {
                if (rc && rc != -ENODATA)
                        goto out;

                if (iint->flags & IMA_DIGSIG_REQUIRED) {
                        if (iint->flags & IMA_VERITY_REQUIRED)
                                cause = "verity-signature-required";
                        else
                                cause = "IMA-signature-required";
                } else {
                        cause = "missing-hash";
                }

                status = INTEGRITY_NOLABEL;
                if (file->f_mode & FMODE_CREATED)
                        iint->flags |= IMA_NEW_FILE;
                if ((iint->flags & IMA_NEW_FILE) &&
                    (!(iint->flags & IMA_DIGSIG_REQUIRED) ||
                     (inode->i_size == 0)))
                        status = INTEGRITY_PASS;
                goto out;
        }

        status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value,
                                 rc < 0 ? 0 : rc);
        switch (status) {
        case INTEGRITY_PASS:
        case INTEGRITY_PASS_IMMUTABLE:
        case INTEGRITY_UNKNOWN:
                break;
        case INTEGRITY_NOXATTRS:        /* No EVM protected xattrs. */
                /* It's fine not to have xattrs when using a modsig. */
                if (try_modsig)
                        break;
                fallthrough;
        case INTEGRITY_NOLABEL:         /* No security.evm xattr. */
                cause = "missing-HMAC";
                goto out;
        case INTEGRITY_FAIL_IMMUTABLE:
                set_bit(IMA_DIGSIG, &iint->atomic_flags);
                cause = "invalid-fail-immutable";
                goto out;
        case INTEGRITY_FAIL:            /* Invalid HMAC/signature. */
                cause = "invalid-HMAC";
                goto out;
        default:
                WARN_ONCE(true, "Unexpected integrity status %d\n", status);
        }

        if (xattr_value)
                rc = xattr_verify(func, iint, xattr_value, xattr_len, &status,
                                  &cause);

        /*
         * If we have a modsig and either no imasig or the imasig's key isn't
         * known, then try verifying the modsig.
         */
        if (try_modsig &&
            (!xattr_value || xattr_value->type == IMA_XATTR_DIGEST_NG ||
             rc == -ENOKEY))
                rc = modsig_verify(func, modsig, &status, &cause);

out:
        /*
         * File signatures on some filesystems can not be properly verified.
         * When such filesystems are mounted by an untrusted mounter or on a
         * system not willing to accept such a risk, fail the file signature
         * verification.
         */
        if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
            ((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) ||
             (iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) {
                status = INTEGRITY_FAIL;
                cause = "unverifiable-signature";
                integrity_audit_msg(audit_msgno, inode, filename,
                                    op, cause, rc, 0);
        } else if (status != INTEGRITY_PASS) {
                /* Fix mode, but don't replace file signatures. */
                if ((ima_appraise & IMA_APPRAISE_FIX) && !try_modsig &&
                    (!xattr_value ||
                     xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
                        if (!ima_fix_xattr(dentry, iint))
                                status = INTEGRITY_PASS;
                }

                /*
                 * Permit new files with file/EVM portable signatures, but
                 * without data.
                 */
                if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE &&
                    test_bit(IMA_DIGSIG, &iint->atomic_flags)) {
                        status = INTEGRITY_PASS;
                }

                integrity_audit_msg(audit_msgno, inode, filename,
                                    op, cause, rc, 0);
        } else {
                ima_cache_flags(iint, func);
        }

        ima_set_cache_status(iint, func, status);
        return status;
}

/*
 * ima_update_xattr - update 'security.ima' hash value
 */
void ima_update_xattr(struct ima_iint_cache *iint, struct file *file)
{
        struct dentry *dentry = file_dentry(file);
        int rc = 0;

        /* do not collect and update hash for digital signatures */
        if (test_bit(IMA_DIGSIG, &iint->atomic_flags))
                return;

        if ((iint->ima_file_status != INTEGRITY_PASS) &&
            !(iint->flags & IMA_HASH))
                return;

        rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo, NULL);
        if (rc < 0)
                return;

        inode_lock(file_inode(file));
        ima_fix_xattr(dentry, iint);
        inode_unlock(file_inode(file));
}

/**
 * ima_inode_post_setattr - reflect file metadata changes
 * @idmap:  idmap of the mount the inode was found from
 * @dentry: pointer to the affected dentry
 * @ia_valid: for the UID and GID status
 *
 * Changes to a dentry's metadata might result in needing to appraise.
 *
 * This function is called from notify_change(), which expects the caller
 * to lock the inode's i_mutex.
 */
static void ima_inode_post_setattr(struct mnt_idmap *idmap,
                                   struct dentry *dentry, int ia_valid)
{
        struct inode *inode = d_backing_inode(dentry);
        struct ima_iint_cache *iint;
        int action;

        if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)
            || !(inode->i_opflags & IOP_XATTR))
                return;

        action = ima_must_appraise(idmap, inode, MAY_ACCESS, POST_SETATTR);
        iint = ima_iint_find(inode);
        if (iint) {
                set_bit(IMA_CHANGE_ATTR, &iint->atomic_flags);
                if (!action)
                        clear_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
        }
}

/*
 * ima_protect_xattr - protect 'security.ima'
 *
 * Ensure that not just anyone can modify or remove 'security.ima'.
 */
static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name,
                             const void *xattr_value, size_t xattr_value_len)
{
        if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
                if (!capable(CAP_SYS_ADMIN))
                        return -EPERM;
                return 1;
        }
        return 0;
}

/*
 * ima_reset_appraise_flags - reset ima_iint_cache flags
 *
 * @digsig: whether to clear/set IMA_DIGSIG flag, tristate values
 *          0: clear IMA_DIGSIG
 *          1: set IMA_DIGSIG
 *         -1: don't change IMA_DIGSIG
 *
 */
static void ima_reset_appraise_flags(struct inode *inode, int digsig)
{
        struct ima_iint_cache *iint;

        if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode))
                return;

        iint = ima_iint_find(inode);
        if (!iint)
                return;
        iint->measured_pcrs = 0;
        set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags);
        if (digsig == 1)
                set_bit(IMA_DIGSIG, &iint->atomic_flags);
        else if (digsig == 0)
                clear_bit(IMA_DIGSIG, &iint->atomic_flags);
}

/**
 * validate_hash_algo() - Block setxattr with unsupported hash algorithms
 * @dentry: object of the setxattr()
 * @xattr_value: userland supplied xattr value
 * @xattr_value_len: length of xattr_value
 *
 * The xattr value is mapped to its hash algorithm, and this algorithm
 * must be built in the kernel for the setxattr to be allowed.
 *
 * Emit an audit message when the algorithm is invalid.
 *
 * Return: 0 on success, else an error.
 */
static int validate_hash_algo(struct dentry *dentry,
                              const struct evm_ima_xattr_data *xattr_value,
                              size_t xattr_value_len)
{
        char *path = NULL, *pathbuf = NULL;
        enum hash_algo xattr_hash_algo;
        const char *errmsg = "unavailable-hash-algorithm";
        unsigned int allowed_hashes;

        xattr_hash_algo = ima_get_hash_algo(xattr_value, xattr_value_len);

        allowed_hashes = atomic_read(&ima_setxattr_allowed_hash_algorithms);

        if (allowed_hashes) {
                /* success if the algorithm is allowed in the ima policy */
                if (allowed_hashes & (1U << xattr_hash_algo))
                        return 0;

                /*
                 * We use a different audit message when the hash algorithm
                 * is denied by a policy rule, instead of not being built
                 * in the kernel image
                 */
                errmsg = "denied-hash-algorithm";
        } else {
                if (likely(xattr_hash_algo == ima_hash_algo))
                        return 0;

                /* allow any xattr using an algorithm built in the kernel */
                if (crypto_has_alg(hash_algo_name[xattr_hash_algo], 0, 0))
                        return 0;
        }

        pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
        if (!pathbuf)
                return -EACCES;

        path = dentry_path(dentry, pathbuf, PATH_MAX);

        integrity_audit_msg(AUDIT_INTEGRITY_DATA, d_inode(dentry), path,
                            "set_data", errmsg, -EACCES, 0);

        kfree(pathbuf);

        return -EACCES;
}

static int ima_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 *xvalue = xattr_value;
        int digsig = 0;
        int result;
        int err;

        result = ima_protect_xattr(dentry, xattr_name, xattr_value,
                                   xattr_value_len);
        if (result == 1) {
                if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
                        return -EINVAL;

                err = validate_hash_algo(dentry, xvalue, xattr_value_len);
                if (err)
                        return err;

                digsig = (xvalue->type == EVM_IMA_XATTR_DIGSIG);
        } else if (!strcmp(xattr_name, XATTR_NAME_EVM) && xattr_value_len > 0) {
                digsig = (xvalue->type == EVM_XATTR_PORTABLE_DIGSIG);
        } else {
                digsig = -1;
        }
        if (result == 1 || evm_revalidate_status(xattr_name)) {
                ima_reset_appraise_flags(d_backing_inode(dentry), digsig);
                if (result == 1)
                        result = 0;
        }
        return result;
}

static int ima_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
                             const char *acl_name, struct posix_acl *kacl)
{
        if (evm_revalidate_status(acl_name))
                ima_reset_appraise_flags(d_backing_inode(dentry), -1);

        return 0;
}

static int ima_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
                                 const char *xattr_name)
{
        int result, digsig = -1;

        result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
        if (result == 1 || evm_revalidate_status(xattr_name)) {
                if (!strcmp(xattr_name, XATTR_NAME_IMA))
                        digsig = 0;
                ima_reset_appraise_flags(d_backing_inode(dentry), digsig);
                if (result == 1)
                        result = 0;
        }
        return result;
}

static int ima_inode_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
                                const char *acl_name)
{
        return ima_inode_set_acl(idmap, dentry, acl_name, NULL);
}

static struct security_hook_list ima_appraise_hooks[] __ro_after_init = {
        LSM_HOOK_INIT(inode_post_setattr, ima_inode_post_setattr),
        LSM_HOOK_INIT(inode_setxattr, ima_inode_setxattr),
        LSM_HOOK_INIT(inode_set_acl, ima_inode_set_acl),
        LSM_HOOK_INIT(inode_removexattr, ima_inode_removexattr),
        LSM_HOOK_INIT(inode_remove_acl, ima_inode_remove_acl),
};

void __init init_ima_appraise_lsm(const struct lsm_id *lsmid)
{
        security_add_hooks(ima_appraise_hooks, ARRAY_SIZE(ima_appraise_hooks),
                           lsmid);
}