467 lines
12 KiB
C
467 lines
12 KiB
C
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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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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 2 of the License.
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*/
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#include <linux/module.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 "ima.h"
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static int __init default_appraise_setup(char *str)
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{
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#ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
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if (strncmp(str, "off", 3) == 0)
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ima_appraise = 0;
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else if (strncmp(str, "log", 3) == 0)
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ima_appraise = IMA_APPRAISE_LOG;
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else if (strncmp(str, "fix", 3) == 0)
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ima_appraise = IMA_APPRAISE_FIX;
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#endif
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return 1;
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}
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__setup("ima_appraise=", default_appraise_setup);
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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 inode *inode, 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_task_getsecid(current, &secid);
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return ima_match_policy(inode, current_cred(), secid, func, mask,
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IMA_APPRAISE | IMA_HASH, 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(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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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(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 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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return ima_hash_algo;
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return sig->hash_algo;
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break;
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case IMA_XATTR_DIGEST_NG:
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ret = xattr_value->digest[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->digest[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(dentry, XATTR_NAME_IMA, (char **)xattr_value,
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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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* ima_appraise_measurement - appraise file measurement
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*
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* Call evm_verifyxattr() to verify the integrity of 'security.ima'.
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* Assuming success, compare the xattr hash with the collected measurement.
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*
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* Return 0 on success, error code otherwise
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*/
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int ima_appraise_measurement(enum ima_hooks func,
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struct integrity_iint_cache *iint,
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struct file *file, const unsigned char *filename,
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struct evm_ima_xattr_data *xattr_value,
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int xattr_len)
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{
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static const char op[] = "appraise_data";
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const char *cause = "unknown";
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struct dentry *dentry = file_dentry(file);
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struct inode *inode = d_backing_inode(dentry);
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enum integrity_status status = INTEGRITY_UNKNOWN;
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int rc = xattr_len, hash_start = 0;
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if (!(inode->i_opflags & IOP_XATTR))
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return INTEGRITY_UNKNOWN;
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if (rc <= 0) {
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if (rc && rc != -ENODATA)
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goto out;
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cause = iint->flags & IMA_DIGSIG_REQUIRED ?
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"IMA-signature-required" : "missing-hash";
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status = INTEGRITY_NOLABEL;
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if (file->f_mode & FMODE_CREATED)
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iint->flags |= IMA_NEW_FILE;
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if ((iint->flags & IMA_NEW_FILE) &&
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(!(iint->flags & IMA_DIGSIG_REQUIRED) ||
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(inode->i_size == 0)))
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status = INTEGRITY_PASS;
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goto out;
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}
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status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
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switch (status) {
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case INTEGRITY_PASS:
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case INTEGRITY_PASS_IMMUTABLE:
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case INTEGRITY_UNKNOWN:
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break;
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case INTEGRITY_NOXATTRS: /* No EVM protected xattrs. */
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case INTEGRITY_NOLABEL: /* No security.evm xattr. */
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cause = "missing-HMAC";
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goto out;
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case INTEGRITY_FAIL: /* Invalid HMAC/signature. */
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cause = "invalid-HMAC";
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goto out;
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default:
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WARN_ONCE(true, "Unexpected integrity status %d\n", status);
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}
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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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/* fall through */
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case IMA_XATTR_DIGEST:
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if (iint->flags & IMA_DIGSIG_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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}
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clear_bit(IMA_DIGSIG, &iint->atomic_flags);
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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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/* 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->digest[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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rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
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(const char *)xattr_value, rc,
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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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} else 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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default:
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status = INTEGRITY_UNKNOWN;
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cause = "unknown-ima-data";
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break;
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}
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out:
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/*
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* File signatures on some filesystems can not be properly verified.
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* When such filesystems are mounted by an untrusted mounter or on a
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* system not willing to accept such a risk, fail the file signature
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* verification.
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*/
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if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
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((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) ||
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(iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) {
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status = INTEGRITY_FAIL;
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cause = "unverifiable-signature";
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integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
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op, cause, rc, 0);
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} else if (status != INTEGRITY_PASS) {
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/* Fix mode, but don't replace file signatures. */
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if ((ima_appraise & IMA_APPRAISE_FIX) &&
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(!xattr_value ||
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xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
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if (!ima_fix_xattr(dentry, iint))
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status = INTEGRITY_PASS;
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}
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/* Permit new files with file signatures, but without data. */
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if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE &&
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xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) {
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status = INTEGRITY_PASS;
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}
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integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
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op, cause, rc, 0);
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} else {
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ima_cache_flags(iint, func);
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}
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ima_set_cache_status(iint, func, status);
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return status;
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}
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/*
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* ima_update_xattr - update 'security.ima' hash value
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*/
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void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
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{
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struct dentry *dentry = file_dentry(file);
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int rc = 0;
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/* do not collect and update hash for digital signatures */
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if (test_bit(IMA_DIGSIG, &iint->atomic_flags))
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return;
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if ((iint->ima_file_status != INTEGRITY_PASS) &&
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!(iint->flags & IMA_HASH))
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return;
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rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo);
|
||
|
|
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
|
||
|
|
* @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 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(inode, MAY_ACCESS, POST_SETATTR);
|
||
|
|
if (!action)
|
||
|
|
__vfs_removexattr(dentry, XATTR_NAME_IMA);
|
||
|
|
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);
|
||
|
|
}
|
||
|
|
|
||
|
|
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 result;
|
||
|
|
|
||
|
|
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;
|
||
|
|
ima_reset_appraise_flags(d_backing_inode(dentry),
|
||
|
|
xvalue->type == EVM_IMA_XATTR_DIGSIG);
|
||
|
|
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) {
|
||
|
|
ima_reset_appraise_flags(d_backing_inode(dentry), 0);
|
||
|
|
result = 0;
|
||
|
|
}
|
||
|
|
return result;
|
||
|
|
}
|