ima_main.c

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/*
 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
 *
 * Authors:
 * Reiner Sailer <[email protected]>
 * Serge Hallyn <[email protected]>
 * Kylene Hall <[email protected]>
 * Mimi Zohar <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, version 2 of the
 * License.
 *
 * File: ima_main.c
 *  implements the IMA hooks: ima_bprm_check, ima_file_mmap,
 *  and ima_file_check.
 */
#include <linux/module.h>
#include <linux/file.h>
#include <linux/binfmts.h>
#include <linux/mount.h>
#include <linux/mman.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include <linux/ima.h>

#include "ima.h"

int ima_initialized;

#ifdef CONFIG_IMA_APPRAISE
int ima_appraise = IMA_APPRAISE_ENFORCE;
#else
int ima_appraise;
#endif

char *ima_hash = "sha1";
static int __init hash_setup(char *str)
{
    if (strncmp(str, "md5", 3) == 0)
        ima_hash = "md5";
    return 1;
}
__setup("ima_hash=", hash_setup);

/*
 * ima_rdwr_violation_check
 *
 * Only invalidate the PCR for measured files:
 *  - Opening a file for write when already open for read,
 *    results in a time of measure, time of use (ToMToU) error.
 *  - Opening a file for read when already open for write,
 *    could result in a file measurement error.
 *
 */
static void ima_rdwr_violation_check(struct file *file)
{
    struct dentry *dentry = file->f_path.dentry;
    struct inode *inode = dentry->d_inode;
    fmode_t mode = file->f_mode;
    int must_measure;
    bool send_tomtou = false, send_writers = false;
    unsigned char *pathname = NULL, *pathbuf = NULL;

    if (!S_ISREG(inode->i_mode) || !ima_initialized)
        return;

    mutex_lock(&inode->i_mutex);    /* file metadata: permissions, xattr */

    if (mode & FMODE_WRITE) {
        if (atomic_read(&inode->i_readcount) && IS_IMA(inode))
            send_tomtou = true;
        goto out;
    }

    must_measure = ima_must_measure(inode, MAY_READ, FILE_CHECK);
    if (!must_measure)
        goto out;

    if (atomic_read(&inode->i_writecount) > 0)
        send_writers = true;
out:
    mutex_unlock(&inode->i_mutex);

    if (!send_tomtou && !send_writers)
        return;

    /* We will allow 11 spaces for ' (deleted)' to be appended */
    pathbuf = kmalloc(PATH_MAX + 11, GFP_KERNEL);
    if (pathbuf) {
        pathname = d_path(&file->f_path, pathbuf, PATH_MAX + 11);
        if (IS_ERR(pathname))
            pathname = NULL;
        else if (strlen(pathname) > IMA_EVENT_NAME_LEN_MAX)
            pathname = NULL;
    }
    if (send_tomtou)
        ima_add_violation(inode,
                  !pathname ? dentry->d_name.name : pathname,
                  "invalid_pcr", "ToMToU");
    if (send_writers)
        ima_add_violation(inode,
                  !pathname ? dentry->d_name.name : pathname,
                  "invalid_pcr", "open_writers");
    kfree(pathbuf);
}

static void ima_check_last_writer(struct integrity_iint_cache *iint,
                  struct inode *inode, struct file *file)
{
    fmode_t mode = file->f_mode;

    if (!(mode & FMODE_WRITE))
        return;

    mutex_lock(&inode->i_mutex);
    if (atomic_read(&inode->i_writecount) == 1 &&
        iint->version != inode->i_version) {
        iint->flags &= ~IMA_DONE_MASK;
        if (iint->flags & IMA_APPRAISE)
            ima_update_xattr(iint, file);
    }
    mutex_unlock(&inode->i_mutex);
}

void ima_file_free(struct file *file)
{
    struct inode *inode = file->f_dentry->d_inode;
    struct integrity_iint_cache *iint;

    if (!iint_initialized || !S_ISREG(inode->i_mode))
        return;

    iint = integrity_iint_find(inode);
    if (!iint)
        return;

    ima_check_last_writer(iint, inode, file);
}

static int process_measurement(struct file *file, const unsigned char *filename,
                   int mask, int function)
{
    struct inode *inode = file->f_dentry->d_inode;
    struct integrity_iint_cache *iint;
    unsigned char *pathname = NULL, *pathbuf = NULL;
    int rc = -ENOMEM, action, must_appraise;

    if (!ima_initialized || !S_ISREG(inode->i_mode))
        return 0;

    /* Determine if in appraise/audit/measurement policy,
     * returns IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT bitmask.  */
    action = ima_get_action(inode, mask, function);
    if (!action)
        return 0;

    must_appraise = action & IMA_APPRAISE;

    mutex_lock(&inode->i_mutex);

    iint = integrity_inode_get(inode);
    if (!iint)
        goto out;

    /* Determine if already appraised/measured based on bitmask
     * (IMA_MEASURE, IMA_MEASURED, IMA_APPRAISE, IMA_APPRAISED,
     *  IMA_AUDIT, IMA_AUDITED) */
    iint->flags |= action;
    action &= ~((iint->flags & IMA_DONE_MASK) >> 1);

    /* Nothing to do, just return existing appraised status */
    if (!action) {
        if (iint->flags & IMA_APPRAISED)
            rc = iint->ima_status;
        goto out;
    }

    rc = ima_collect_measurement(iint, file);
    if (rc != 0)
        goto out;

    if (function != BPRM_CHECK) {
        /* We will allow 11 spaces for ' (deleted)' to be appended */
        pathbuf = kmalloc(PATH_MAX + 11, GFP_KERNEL);
        if (pathbuf) {
            pathname =
                d_path(&file->f_path, pathbuf, PATH_MAX + 11);
            if (IS_ERR(pathname))
                pathname = NULL;
        }
    }
    if (action & IMA_MEASURE)
        ima_store_measurement(iint, file,
                      !pathname ? filename : pathname);
    if (action & IMA_APPRAISE)
        rc = ima_appraise_measurement(iint, file,
                          !pathname ? filename : pathname);
    if (action & IMA_AUDIT)
        ima_audit_measurement(iint, !pathname ? filename : pathname);
    kfree(pathbuf);
out:
    mutex_unlock(&inode->i_mutex);
    return (rc && must_appraise) ? -EACCES : 0;
}

int ima_file_mmap(struct file *file, unsigned long prot)
{
    int rc = 0;

    if (!file)
        return 0;
    if (prot & PROT_EXEC)
        rc = process_measurement(file, file->f_dentry->d_name.name,
                     MAY_EXEC, FILE_MMAP);
    return (ima_appraise & IMA_APPRAISE_ENFORCE) ? rc : 0;
}

int ima_bprm_check(struct linux_binprm *bprm)
{
    int rc;

    rc = process_measurement(bprm->file,
                 (strcmp(bprm->filename, bprm->interp) == 0) ?
                 bprm->filename : bprm->interp,
                 MAY_EXEC, BPRM_CHECK);
    return (ima_appraise & IMA_APPRAISE_ENFORCE) ? rc : 0;
}

int ima_file_check(struct file *file, int mask)
{
    int rc;

    ima_rdwr_violation_check(file);
    rc = process_measurement(file, file->f_dentry->d_name.name,
                 mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
                 FILE_CHECK);
    return (ima_appraise & IMA_APPRAISE_ENFORCE) ? rc : 0;
}
EXPORT_SYMBOL_GPL(ima_file_check);

static int __init init_ima(void)
{
    int error;

    error = ima_init();
    if (!error)
        ima_initialized = 1;
    return error;
}

late_initcall(init_ima);    /* Start IMA after the TPM is available */

MODULE_DESCRIPTION("Integrity Measurement Architecture");
MODULE_LICENSE("GPL");