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1adace9bb0
The original ima_must_measure() function based its results on cached iint information, which required an iint be allocated for all files. Currently, an iint is allocated only for files in policy. As a result, for those files in policy, ima_must_measure() is now called twice: once to determine if the inode is in the measurement policy and, the second time, to determine if it needs to be measured/re-measured. The second call to ima_must_measure() unnecessarily checks to see if the file is in policy. As we already know the file is in policy, this patch removes the second unnecessary call to ima_must_measure(), removes the vestige iint parameter, and just checks the iint directly to determine if the inode has been measured or needs to be measured/re-measured. Signed-off-by: Mimi Zohar <zohar@us.ibm.com> Acked-by: Eric Paris <eparis@redhat.com>
185 lines
5.4 KiB
C
185 lines
5.4 KiB
C
/*
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* Copyright (C) 2008 IBM Corporation
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*
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* Author: 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
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*
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* File: ima_api.c
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* Implements must_measure, collect_measurement, store_measurement,
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* and store_template.
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*/
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#include <linux/module.h>
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#include <linux/slab.h>
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#include "ima.h"
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static const char *IMA_TEMPLATE_NAME = "ima";
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/*
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* ima_store_template - store ima template measurements
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*
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* Calculate the hash of a template entry, add the template entry
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* to an ordered list of measurement entries maintained inside the kernel,
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* and also update the aggregate integrity value (maintained inside the
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* configured TPM PCR) over the hashes of the current list of measurement
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* entries.
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*
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* Applications retrieve the current kernel-held measurement list through
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* the securityfs entries in /sys/kernel/security/ima. The signed aggregate
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* TPM PCR (called quote) can be retrieved using a TPM user space library
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* and is used to validate the measurement list.
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*
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* Returns 0 on success, error code otherwise
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*/
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int ima_store_template(struct ima_template_entry *entry,
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int violation, struct inode *inode)
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{
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const char *op = "add_template_measure";
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const char *audit_cause = "hashing_error";
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int result;
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memset(entry->digest, 0, sizeof(entry->digest));
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entry->template_name = IMA_TEMPLATE_NAME;
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entry->template_len = sizeof(entry->template);
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if (!violation) {
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result = ima_calc_template_hash(entry->template_len,
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&entry->template,
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entry->digest);
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if (result < 0) {
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integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
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entry->template_name, op,
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audit_cause, result, 0);
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return result;
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}
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}
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result = ima_add_template_entry(entry, violation, op, inode);
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return result;
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}
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/*
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* ima_add_violation - add violation to measurement list.
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*
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* Violations are flagged in the measurement list with zero hash values.
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* By extending the PCR with 0xFF's instead of with zeroes, the PCR
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* value is invalidated.
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*/
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void ima_add_violation(struct inode *inode, const unsigned char *filename,
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const char *op, const char *cause)
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{
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struct ima_template_entry *entry;
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int violation = 1;
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int result;
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/* can overflow, only indicator */
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atomic_long_inc(&ima_htable.violations);
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entry = kmalloc(sizeof(*entry), GFP_KERNEL);
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if (!entry) {
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result = -ENOMEM;
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goto err_out;
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}
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memset(&entry->template, 0, sizeof(entry->template));
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strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX);
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result = ima_store_template(entry, violation, inode);
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if (result < 0)
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kfree(entry);
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err_out:
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integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
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op, cause, result, 0);
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}
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/**
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* ima_must_measure - measure decision based on policy.
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* @inode: pointer to inode to measure
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* @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXECUTE)
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* @function: calling function (FILE_CHECK, BPRM_CHECK, FILE_MMAP)
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*
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* The policy is defined in terms of keypairs:
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* subj=, obj=, type=, func=, mask=, fsmagic=
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* subj,obj, and type: are LSM specific.
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* func: FILE_CHECK | BPRM_CHECK | FILE_MMAP
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* mask: contains the permission mask
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* fsmagic: hex value
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*
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* Return 0 to measure. For matching a DONT_MEASURE policy, no policy,
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* or other error, return an error code.
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*/
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int ima_must_measure(struct inode *inode, int mask, int function)
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{
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int must_measure;
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must_measure = ima_match_policy(inode, function, mask);
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return must_measure ? 0 : -EACCES;
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}
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/*
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* ima_collect_measurement - collect file measurement
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*
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* Calculate the file hash, if it doesn't already exist,
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* storing the measurement and i_version in the iint.
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*
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* Must be called with iint->mutex held.
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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_collect_measurement(struct ima_iint_cache *iint, struct file *file)
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{
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int result = -EEXIST;
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if (!(iint->flags & IMA_MEASURED)) {
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u64 i_version = file->f_dentry->d_inode->i_version;
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memset(iint->digest, 0, IMA_DIGEST_SIZE);
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result = ima_calc_hash(file, iint->digest);
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if (!result)
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iint->version = i_version;
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}
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return result;
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}
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/*
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* ima_store_measurement - store file measurement
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*
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* Create an "ima" template and then store the template by calling
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* ima_store_template.
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*
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* We only get here if the inode has not already been measured,
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* but the measurement could already exist:
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* - multiple copies of the same file on either the same or
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* different filesystems.
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* - the inode was previously flushed as well as the iint info,
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* containing the hashing info.
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*
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* Must be called with iint->mutex held.
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*/
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void ima_store_measurement(struct ima_iint_cache *iint, struct file *file,
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const unsigned char *filename)
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{
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const char *op = "add_template_measure";
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const char *audit_cause = "ENOMEM";
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int result = -ENOMEM;
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struct inode *inode = file->f_dentry->d_inode;
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struct ima_template_entry *entry;
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int violation = 0;
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entry = kmalloc(sizeof(*entry), GFP_KERNEL);
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if (!entry) {
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integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
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op, audit_cause, result, 0);
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return;
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}
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memset(&entry->template, 0, sizeof(entry->template));
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memcpy(entry->template.digest, iint->digest, IMA_DIGEST_SIZE);
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strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX);
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result = ima_store_template(entry, violation, inode);
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if (!result)
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iint->flags |= IMA_MEASURED;
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else
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kfree(entry);
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}
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