172 lines
4.3 KiB
C
172 lines
4.3 KiB
C
/*
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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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if (strncmp(str, "off", 3) == 0)
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ima_appraise = 0;
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else if (strncmp(str, "fix", 3) == 0)
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ima_appraise = IMA_APPRAISE_FIX;
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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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* ima_must_appraise - set appraise flag
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*
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* Return 1 to appraise
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*/
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int ima_must_appraise(struct inode *inode, enum ima_hooks func, int mask)
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{
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if (!ima_appraise)
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return 0;
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return ima_match_policy(inode, func, mask, IMA_APPRAISE);
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}
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static void ima_fix_xattr(struct dentry *dentry,
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struct integrity_iint_cache *iint)
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{
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iint->digest[0] = IMA_XATTR_DIGEST;
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__vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
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iint->digest, IMA_DIGEST_SIZE + 1, 0);
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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(struct integrity_iint_cache *iint,
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struct file *file, const unsigned char *filename)
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{
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struct dentry *dentry = file->f_dentry;
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struct inode *inode = dentry->d_inode;
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u8 xattr_value[IMA_DIGEST_SIZE];
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enum integrity_status status = INTEGRITY_UNKNOWN;
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const char *op = "appraise_data";
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char *cause = "unknown";
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int rc;
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if (!ima_appraise)
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return 0;
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if (!inode->i_op->getxattr)
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return INTEGRITY_UNKNOWN;
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if (iint->flags & IMA_APPRAISED)
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return iint->ima_status;
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rc = inode->i_op->getxattr(dentry, XATTR_NAME_IMA, xattr_value,
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IMA_DIGEST_SIZE);
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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 = "missing-hash";
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status =
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(inode->i_size == 0) ? INTEGRITY_PASS : INTEGRITY_NOLABEL;
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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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if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) {
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if ((status == INTEGRITY_NOLABEL)
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|| (status == INTEGRITY_NOXATTRS))
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cause = "missing-HMAC";
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else if (status == INTEGRITY_FAIL)
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cause = "invalid-HMAC";
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goto out;
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}
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rc = memcmp(xattr_value, iint->digest, IMA_DIGEST_SIZE);
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if (rc) {
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status = INTEGRITY_FAIL;
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cause = "invalid-hash";
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print_hex_dump_bytes("security.ima: ", DUMP_PREFIX_NONE,
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xattr_value, IMA_DIGEST_SIZE);
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print_hex_dump_bytes("collected: ", DUMP_PREFIX_NONE,
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iint->digest, IMA_DIGEST_SIZE);
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goto out;
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}
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status = INTEGRITY_PASS;
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iint->flags |= IMA_APPRAISED;
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out:
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if (status != INTEGRITY_PASS) {
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if (ima_appraise & IMA_APPRAISE_FIX) {
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ima_fix_xattr(dentry, iint);
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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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}
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iint->ima_status = 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->f_dentry;
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int rc = 0;
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rc = ima_collect_measurement(iint, file);
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if (rc < 0)
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return;
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ima_fix_xattr(dentry, iint);
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}
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/**
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* ima_inode_post_setattr - reflect file metadata changes
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* @dentry: pointer to the affected dentry
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*
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* Changes to a dentry's metadata might result in needing to appraise.
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*
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* This function is called from notify_change(), which expects the caller
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* to lock the inode's i_mutex.
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*/
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void ima_inode_post_setattr(struct dentry *dentry)
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{
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struct inode *inode = dentry->d_inode;
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struct integrity_iint_cache *iint;
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int must_appraise, rc;
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if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode)
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|| !inode->i_op->removexattr)
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return;
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must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
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iint = integrity_iint_find(inode);
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if (iint) {
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if (must_appraise)
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iint->flags |= IMA_APPRAISE;
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else
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iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED);
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}
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if (!must_appraise)
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rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA);
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return;
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}
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