789 lines
20 KiB
C
789 lines
20 KiB
C
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2011 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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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/file.h>
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#include <linux/fs.h>
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#include <linux/xattr.h>
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#include <linux/magic.h>
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#include <linux/ima.h>
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#include <linux/evm.h>
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#include <linux/fsverity.h>
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#include <keys/system_keyring.h>
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#include <uapi/linux/fsverity.h>
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#include "ima.h"
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#ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
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static char *ima_appraise_cmdline_default __initdata;
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core_param(ima_appraise, ima_appraise_cmdline_default, charp, 0);
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void __init ima_appraise_parse_cmdline(void)
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{
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const char *str = ima_appraise_cmdline_default;
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bool sb_state = arch_ima_get_secureboot();
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int appraisal_state = ima_appraise;
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if (!str)
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return;
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if (strncmp(str, "off", 3) == 0)
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appraisal_state = 0;
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else if (strncmp(str, "log", 3) == 0)
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appraisal_state = IMA_APPRAISE_LOG;
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else if (strncmp(str, "fix", 3) == 0)
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appraisal_state = IMA_APPRAISE_FIX;
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else if (strncmp(str, "enforce", 7) == 0)
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appraisal_state = IMA_APPRAISE_ENFORCE;
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else
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pr_err("invalid \"%s\" appraise option", str);
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/* If appraisal state was changed, but secure boot is enabled,
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* keep its default */
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if (sb_state) {
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if (!(appraisal_state & IMA_APPRAISE_ENFORCE))
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pr_info("Secure boot enabled: ignoring ima_appraise=%s option",
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str);
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} else {
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ima_appraise = appraisal_state;
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}
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}
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#endif
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/*
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* is_ima_appraise_enabled - return appraise status
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*
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* Only return enabled, if not in ima_appraise="fix" or "log" modes.
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*/
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bool is_ima_appraise_enabled(void)
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{
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return ima_appraise & IMA_APPRAISE_ENFORCE;
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}
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/*
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* ima_must_appraise - set appraise flag
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*
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* Return 1 to appraise or hash
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*/
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int ima_must_appraise(struct user_namespace *mnt_userns, struct inode *inode,
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int mask, enum ima_hooks func)
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{
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u32 secid;
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if (!ima_appraise)
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return 0;
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security_current_getsecid_subj(&secid);
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return ima_match_policy(mnt_userns, inode, current_cred(), secid,
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func, mask, IMA_APPRAISE | IMA_HASH, NULL,
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NULL, NULL, NULL);
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}
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static int ima_fix_xattr(struct dentry *dentry,
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struct integrity_iint_cache *iint)
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{
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int rc, offset;
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u8 algo = iint->ima_hash->algo;
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if (algo <= HASH_ALGO_SHA1) {
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offset = 1;
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iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST;
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} else {
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offset = 0;
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iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG;
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iint->ima_hash->xattr.ng.algo = algo;
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}
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rc = __vfs_setxattr_noperm(&init_user_ns, dentry, XATTR_NAME_IMA,
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&iint->ima_hash->xattr.data[offset],
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(sizeof(iint->ima_hash->xattr) - offset) +
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iint->ima_hash->length, 0);
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return rc;
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}
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/* Return specific func appraised cached result */
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enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
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enum ima_hooks func)
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{
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switch (func) {
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case MMAP_CHECK:
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return iint->ima_mmap_status;
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case BPRM_CHECK:
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return iint->ima_bprm_status;
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case CREDS_CHECK:
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return iint->ima_creds_status;
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case FILE_CHECK:
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case POST_SETATTR:
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return iint->ima_file_status;
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case MODULE_CHECK ... MAX_CHECK - 1:
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default:
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return iint->ima_read_status;
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}
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}
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static void ima_set_cache_status(struct integrity_iint_cache *iint,
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enum ima_hooks func,
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enum integrity_status status)
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{
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switch (func) {
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case MMAP_CHECK:
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iint->ima_mmap_status = status;
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break;
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case BPRM_CHECK:
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iint->ima_bprm_status = status;
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break;
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case CREDS_CHECK:
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iint->ima_creds_status = status;
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break;
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case FILE_CHECK:
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case POST_SETATTR:
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iint->ima_file_status = status;
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break;
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case MODULE_CHECK ... MAX_CHECK - 1:
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default:
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iint->ima_read_status = status;
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break;
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}
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}
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static void ima_cache_flags(struct integrity_iint_cache *iint,
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enum ima_hooks func)
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{
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switch (func) {
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case MMAP_CHECK:
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iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
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break;
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case BPRM_CHECK:
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iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
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break;
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case CREDS_CHECK:
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iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED);
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break;
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case FILE_CHECK:
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case POST_SETATTR:
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iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
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break;
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case MODULE_CHECK ... MAX_CHECK - 1:
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default:
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iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED);
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break;
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}
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}
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enum hash_algo ima_get_hash_algo(const struct evm_ima_xattr_data *xattr_value,
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int xattr_len)
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{
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struct signature_v2_hdr *sig;
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enum hash_algo ret;
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if (!xattr_value || xattr_len < 2)
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/* return default hash algo */
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return ima_hash_algo;
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switch (xattr_value->type) {
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case IMA_VERITY_DIGSIG:
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sig = (typeof(sig))xattr_value;
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if (sig->version != 3 || xattr_len <= sizeof(*sig) ||
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sig->hash_algo >= HASH_ALGO__LAST)
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return ima_hash_algo;
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return sig->hash_algo;
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case EVM_IMA_XATTR_DIGSIG:
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sig = (typeof(sig))xattr_value;
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if (sig->version != 2 || xattr_len <= sizeof(*sig)
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|| sig->hash_algo >= HASH_ALGO__LAST)
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return ima_hash_algo;
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return sig->hash_algo;
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case IMA_XATTR_DIGEST_NG:
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/* first byte contains algorithm id */
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ret = xattr_value->data[0];
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if (ret < HASH_ALGO__LAST)
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return ret;
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break;
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case IMA_XATTR_DIGEST:
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/* this is for backward compatibility */
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if (xattr_len == 21) {
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unsigned int zero = 0;
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if (!memcmp(&xattr_value->data[16], &zero, 4))
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return HASH_ALGO_MD5;
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else
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return HASH_ALGO_SHA1;
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} else if (xattr_len == 17)
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return HASH_ALGO_MD5;
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break;
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}
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/* return default hash algo */
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return ima_hash_algo;
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}
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int ima_read_xattr(struct dentry *dentry,
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struct evm_ima_xattr_data **xattr_value)
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{
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ssize_t ret;
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ret = vfs_getxattr_alloc(&init_user_ns, dentry, XATTR_NAME_IMA,
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(char **)xattr_value, 0, GFP_NOFS);
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if (ret == -EOPNOTSUPP)
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ret = 0;
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return ret;
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}
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/*
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* calc_file_id_hash - calculate the hash of the ima_file_id struct data
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* @type: xattr type [enum evm_ima_xattr_type]
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* @algo: hash algorithm [enum hash_algo]
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* @digest: pointer to the digest to be hashed
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* @hash: (out) pointer to the hash
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*
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* IMA signature version 3 disambiguates the data that is signed by
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* indirectly signing the hash of the ima_file_id structure data.
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*
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* Signing the ima_file_id struct is currently only supported for
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* IMA_VERITY_DIGSIG type xattrs.
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*
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* Return 0 on success, error code otherwise.
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*/
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static int calc_file_id_hash(enum evm_ima_xattr_type type,
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enum hash_algo algo, const u8 *digest,
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struct ima_digest_data *hash)
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{
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struct ima_file_id file_id = {
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.hash_type = IMA_VERITY_DIGSIG, .hash_algorithm = algo};
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unsigned int unused = HASH_MAX_DIGESTSIZE - hash_digest_size[algo];
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if (type != IMA_VERITY_DIGSIG)
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return -EINVAL;
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memcpy(file_id.hash, digest, hash_digest_size[algo]);
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hash->algo = algo;
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hash->length = hash_digest_size[algo];
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return ima_calc_buffer_hash(&file_id, sizeof(file_id) - unused, hash);
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}
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/*
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* xattr_verify - verify xattr digest or signature
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*
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* Verify whether the hash or signature matches the file contents.
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*
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* Return 0 on success, error code otherwise.
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*/
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static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
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struct evm_ima_xattr_data *xattr_value, int xattr_len,
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enum integrity_status *status, const char **cause)
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{
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struct ima_max_digest_data hash;
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struct signature_v2_hdr *sig;
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int rc = -EINVAL, hash_start = 0;
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int mask;
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switch (xattr_value->type) {
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case IMA_XATTR_DIGEST_NG:
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/* first byte contains algorithm id */
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hash_start = 1;
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fallthrough;
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case IMA_XATTR_DIGEST:
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if (*status != INTEGRITY_PASS_IMMUTABLE) {
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if (iint->flags & IMA_DIGSIG_REQUIRED) {
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if (iint->flags & IMA_VERITY_REQUIRED)
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*cause = "verity-signature-required";
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else
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*cause = "IMA-signature-required";
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*status = INTEGRITY_FAIL;
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break;
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}
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clear_bit(IMA_DIGSIG, &iint->atomic_flags);
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} else {
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set_bit(IMA_DIGSIG, &iint->atomic_flags);
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}
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if (xattr_len - sizeof(xattr_value->type) - hash_start >=
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iint->ima_hash->length)
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/*
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* xattr length may be longer. md5 hash in previous
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* version occupied 20 bytes in xattr, instead of 16
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*/
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rc = memcmp(&xattr_value->data[hash_start],
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iint->ima_hash->digest,
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iint->ima_hash->length);
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else
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rc = -EINVAL;
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if (rc) {
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*cause = "invalid-hash";
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*status = INTEGRITY_FAIL;
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break;
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}
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*status = INTEGRITY_PASS;
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break;
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case EVM_IMA_XATTR_DIGSIG:
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set_bit(IMA_DIGSIG, &iint->atomic_flags);
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mask = IMA_DIGSIG_REQUIRED | IMA_VERITY_REQUIRED;
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if ((iint->flags & mask) == mask) {
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*cause = "verity-signature-required";
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*status = INTEGRITY_FAIL;
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break;
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}
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sig = (typeof(sig))xattr_value;
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if (sig->version >= 3) {
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*cause = "invalid-signature-version";
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*status = INTEGRITY_FAIL;
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break;
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}
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rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
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(const char *)xattr_value,
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xattr_len,
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iint->ima_hash->digest,
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iint->ima_hash->length);
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if (rc == -EOPNOTSUPP) {
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*status = INTEGRITY_UNKNOWN;
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break;
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}
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if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
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func == KEXEC_KERNEL_CHECK)
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rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
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(const char *)xattr_value,
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xattr_len,
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iint->ima_hash->digest,
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iint->ima_hash->length);
|
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if (rc) {
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*cause = "invalid-signature";
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*status = INTEGRITY_FAIL;
|
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} else {
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*status = INTEGRITY_PASS;
|
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}
|
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break;
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case IMA_VERITY_DIGSIG:
|
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set_bit(IMA_DIGSIG, &iint->atomic_flags);
|
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|
|
||
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if (iint->flags & IMA_DIGSIG_REQUIRED) {
|
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if (!(iint->flags & IMA_VERITY_REQUIRED)) {
|
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*cause = "IMA-signature-required";
|
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*status = INTEGRITY_FAIL;
|
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|
break;
|
||
|
}
|
||
|
}
|
||
|
|
||
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sig = (typeof(sig))xattr_value;
|
||
|
if (sig->version != 3) {
|
||
|
*cause = "invalid-signature-version";
|
||
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*status = INTEGRITY_FAIL;
|
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|
break;
|
||
|
}
|
||
|
|
||
|
rc = calc_file_id_hash(IMA_VERITY_DIGSIG, iint->ima_hash->algo,
|
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iint->ima_hash->digest, &hash.hdr);
|
||
|
if (rc) {
|
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|
*cause = "sigv3-hashing-error";
|
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|
*status = INTEGRITY_FAIL;
|
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|
break;
|
||
|
}
|
||
|
|
||
|
rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
|
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|
(const char *)xattr_value,
|
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|
xattr_len, hash.digest,
|
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|
hash.hdr.length);
|
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|
if (rc) {
|
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*cause = "invalid-verity-signature";
|
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*status = INTEGRITY_FAIL;
|
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|
} else {
|
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|
*status = INTEGRITY_PASS;
|
||
|
}
|
||
|
|
||
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break;
|
||
|
default:
|
||
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*status = INTEGRITY_UNKNOWN;
|
||
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*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 integrity_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);
|
||
|
if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
|
||
|
process_buffer_measurement(&init_user_ns, 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 integrity_iint_cache *iint,
|
||
|
struct file *file, const unsigned char *filename,
|
||
|
struct evm_ima_xattr_data *xattr_value,
|
||
|
int xattr_len, const struct modsig *modsig)
|
||
|
{
|
||
|
static const char op[] = "appraise_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;
|
||
|
|
||
|
/* 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, iint);
|
||
|
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_INTEGRITY_DATA, 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_INTEGRITY_DATA, 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 integrity_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
|
||
|
* @mnt_userns: user namespace of the mount the inode was found from
|
||
|
* @dentry: pointer to the affected dentry
|
||
|
*
|
||
|
* 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.
|
||
|
*/
|
||
|
void ima_inode_post_setattr(struct user_namespace *mnt_userns,
|
||
|
struct dentry *dentry)
|
||
|
{
|
||
|
struct inode *inode = d_backing_inode(dentry);
|
||
|
struct integrity_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(mnt_userns, inode, MAY_ACCESS, POST_SETATTR);
|
||
|
iint = integrity_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;
|
||
|
}
|
||
|
|
||
|
static void ima_reset_appraise_flags(struct inode *inode, int digsig)
|
||
|
{
|
||
|
struct integrity_iint_cache *iint;
|
||
|
|
||
|
if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode))
|
||
|
return;
|
||
|
|
||
|
iint = integrity_iint_find(inode);
|
||
|
if (!iint)
|
||
|
return;
|
||
|
iint->measured_pcrs = 0;
|
||
|
set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags);
|
||
|
if (digsig)
|
||
|
set_bit(IMA_DIGSIG, &iint->atomic_flags);
|
||
|
else
|
||
|
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;
|
||
|
}
|
||
|
|
||
|
int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
|
||
|
const void *xattr_value, size_t xattr_value_len)
|
||
|
{
|
||
|
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);
|
||
|
}
|
||
|
if (result == 1 || evm_revalidate_status(xattr_name)) {
|
||
|
ima_reset_appraise_flags(d_backing_inode(dentry), digsig);
|
||
|
if (result == 1)
|
||
|
result = 0;
|
||
|
}
|
||
|
return result;
|
||
|
}
|
||
|
|
||
|
int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
|
||
|
{
|
||
|
int result;
|
||
|
|
||
|
result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
|
||
|
if (result == 1 || evm_revalidate_status(xattr_name)) {
|
||
|
ima_reset_appraise_flags(d_backing_inode(dentry), 0);
|
||
|
if (result == 1)
|
||
|
result = 0;
|
||
|
}
|
||
|
return result;
|
||
|
}
|