/*
 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
 *
 * Authors:
 * Reiner Sailer <sailer@watson.ibm.com>
 * Serge Hallyn <serue@us.ibm.com>
 * Kylene Hall <kylene@us.ibm.com>
 * Mimi Zohar <zohar@us.ibm.com>
 *
 * 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 = file_inode(file);
        fmode_t mode = file->f_mode;
        int must_measure;
        bool send_tomtou = false, send_writers = false;
        char *pathbuf = NULL;
        const char *pathname;

        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;

        pathname = ima_d_path(&file->f_path, &pathbuf);
        if (!pathname || strlen(pathname) > IMA_EVENT_NAME_LEN_MAX)
                pathname = dentry->d_name.name;

        if (send_tomtou)
                ima_add_violation(inode, pathname,
                                  "invalid_pcr", "ToMToU");
        if (send_writers)
                ima_add_violation(inode, 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);
}

/**
 * ima_file_free - called on __fput()
 * @file: pointer to file structure being freed
 *
 * Flag files that changed, based on i_version
 */
void ima_file_free(struct file *file)
{
        struct inode *inode = file_inode(file);
        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 char *filename,
                               int mask, int function)
{
        struct inode *inode = file_inode(file);
        struct integrity_iint_cache *iint;
        char *pathbuf = NULL;
        const char *pathname = NULL;
        int rc = -ENOMEM, action, must_appraise, _func;

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

        /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
         * bitmask based on the appraise/audit/measurement policy.
         * Included is the appraise submask.
         */
        action = ima_get_action(inode, mask, function);
        if (!action)
                return 0;

        must_appraise = action & IMA_APPRAISE;

        /*  Is the appraise rule hook specific?  */
        _func = (action & IMA_FILE_APPRAISE) ? FILE_CHECK : function;

        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_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
         *  IMA_AUDIT, IMA_AUDITED)
         */
        iint->flags |= action;
        action &= IMA_DO_MASK;
        action &= ~((iint->flags & IMA_DONE_MASK) >> 1);

        /* Nothing to do, just return existing appraised status */
        if (!action) {
                if (must_appraise)
                        rc = ima_get_cache_status(iint, _func);
                goto out_digsig;
        }

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

        pathname = !filename ? ima_d_path(&file->f_path, &pathbuf) : filename;
        if (!pathname)
                pathname = (const char *)file->f_dentry->d_name.name;

        if (action & IMA_MEASURE)
                ima_store_measurement(iint, file, pathname);
        if (action & IMA_APPRAISE_SUBMASK)
                rc = ima_appraise_measurement(_func, iint, file, pathname);
        if (action & IMA_AUDIT)
                ima_audit_measurement(iint, pathname);
        kfree(pathbuf);
out_digsig:
        if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG))
                rc = -EACCES;
out:
        mutex_unlock(&inode->i_mutex);
        if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE))
                return -EACCES;
        return 0;
}

/**
 * ima_file_mmap - based on policy, collect/store measurement.
 * @file: pointer to the file to be measured (May be NULL)
 * @prot: contains the protection that will be applied by the kernel.
 *
 * Measure files being mmapped executable based on the ima_must_measure()
 * policy decision.
 *
 * On success return 0.  On integrity appraisal error, assuming the file
 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 */
int ima_file_mmap(struct file *file, unsigned long prot)
{
        if (file && (prot & PROT_EXEC))
                return process_measurement(file, NULL, MAY_EXEC, MMAP_CHECK);
        return 0;
}

/**
 * ima_bprm_check - based on policy, collect/store measurement.
 * @bprm: contains the linux_binprm structure
 *
 * The OS protects against an executable file, already open for write,
 * from being executed in deny_write_access() and an executable file,
 * already open for execute, from being modified in get_write_access().
 * So we can be certain that what we verify and measure here is actually
 * what is being executed.
 *
 * On success return 0.  On integrity appraisal error, assuming the file
 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 */
int ima_bprm_check(struct linux_binprm *bprm)
{
        return process_measurement(bprm->file,
                                 (strcmp(bprm->filename, bprm->interp) == 0) ?
                                 bprm->filename : bprm->interp,
                                 MAY_EXEC, BPRM_CHECK);
}

/**
 * ima_path_check - based on policy, collect/store measurement.
 * @file: pointer to the file to be measured
 * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
 *
 * Measure files based on the ima_must_measure() policy decision.
 *
 * On success return 0.  On integrity appraisal error, assuming the file
 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 */
int ima_file_check(struct file *file, int mask)
{
        ima_rdwr_violation_check(file);
        return process_measurement(file, NULL,
                                 mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
                                 FILE_CHECK);
}
EXPORT_SYMBOL_GPL(ima_file_check);

/**
 * ima_module_check - based on policy, collect/store/appraise measurement.
 * @file: pointer to the file to be measured/appraised
 *
 * Measure/appraise kernel modules based on policy.
 *
 * On success return 0.  On integrity appraisal error, assuming the file
 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 */
int ima_module_check(struct file *file)
{
        if (!file) {
#ifndef CONFIG_MODULE_SIG_FORCE
                if ((ima_appraise & IMA_APPRAISE_MODULES) &&
                    (ima_appraise & IMA_APPRAISE_ENFORCE))
                        return -EACCES; /* INTEGRITY_UNKNOWN */
#endif
                return 0;       /* We rely on module signature checking */
        }
        return process_measurement(file, NULL, MAY_EXEC, MODULE_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");