/*
 * 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

int ima_hash_algo = HASH_ALGO_SHA1;
static int hash_setup_done;

static int __init hash_setup(char *str)
{
        struct ima_template_desc *template_desc = ima_template_desc_current();
        int i;

        if (hash_setup_done)
                return 1;

        if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
                if (strncmp(str, "sha1", 4) == 0)
                        ima_hash_algo = HASH_ALGO_SHA1;
                else if (strncmp(str, "md5", 3) == 0)
                        ima_hash_algo = HASH_ALGO_MD5;
                goto out;
        }

        for (i = 0; i < HASH_ALGO__LAST; i++) {
                if (strcmp(str, hash_algo_name[i]) == 0) {
                        ima_hash_algo = i;
                        break;
                }
        }
out:
        hash_setup_done = 1;
        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 integrity_iint_cache *iint,
                                     int must_measure,
                                     char **pathbuf,
                                     const char **pathname)
{
        struct inode *inode = file_inode(file);
        fmode_t mode = file->f_mode;
        bool send_tomtou = false, send_writers = false;

        if (mode & FMODE_WRITE) {
                if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
                        if (!iint)
                                iint = integrity_iint_find(inode);
                        /* IMA_MEASURE is set from reader side */
                        if (iint && (iint->flags & IMA_MEASURE))
                                send_tomtou = true;
                }
        } else {
                if ((atomic_read(&inode->i_writecount) > 0) && must_measure)
                        send_writers = true;
        }

        if (!send_tomtou && !send_writers)
                return;

        *pathname = ima_d_path(&file->f_path, pathbuf);

        if (send_tomtou)
                ima_add_violation(file, *pathname, iint,
                                  "invalid_pcr", "ToMToU");
        if (send_writers)
                ima_add_violation(file, *pathname, iint,
                                  "invalid_pcr", "open_writers");
}

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;

        inode_lock(inode);
        if (atomic_read(&inode->i_writecount) == 1) {
                if ((iint->version != inode->i_version) ||
                    (iint->flags & IMA_NEW_FILE)) {
                        iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
                        if (iint->flags & IMA_APPRAISE)
                                ima_update_xattr(iint, file);
                }
        }
        inode_unlock(inode);
}

/**
 * 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 (!ima_policy_flag || !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, char *buf, loff_t size,
                               int mask, enum ima_hooks func, int opened)
{
        struct inode *inode = file_inode(file);
        struct integrity_iint_cache *iint = NULL;
        struct ima_template_desc *template_desc;
        char *pathbuf = NULL;
        const char *pathname = NULL;
        int rc = -ENOMEM, action, must_appraise;
        struct evm_ima_xattr_data *xattr_value = NULL;
        int xattr_len = 0;
        bool violation_check;
        enum hash_algo hash_algo;

        if (!ima_policy_flag || !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, func);
        violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) &&
                           (ima_policy_flag & IMA_MEASURE));
        if (!action && !violation_check)
                return 0;

        must_appraise = action & IMA_APPRAISE;

        /*  Is the appraise rule hook specific?  */
        if (action & IMA_FILE_APPRAISE)
                func = FILE_CHECK;

        inode_lock(inode);

        if (action) {
                iint = integrity_inode_get(inode);
                if (!iint)
                        goto out;
        }

        if (violation_check) {
                ima_rdwr_violation_check(file, iint, action & IMA_MEASURE,
                                         &pathbuf, &pathname);
                if (!action) {
                        rc = 0;
                        goto out_free;
                }
        }

        /* 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;
        }

        template_desc = ima_template_desc_current();
        if ((action & IMA_APPRAISE_SUBMASK) ||
                    strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0)
                /* read 'security.ima' */
                xattr_len = ima_read_xattr(file->f_path.dentry, &xattr_value);

        hash_algo = ima_get_hash_algo(xattr_value, xattr_len);

        rc = ima_collect_measurement(iint, file, buf, size, hash_algo);
        if (rc != 0) {
                if (file->f_flags & O_DIRECT)
                        rc = (iint->flags & IMA_PERMIT_DIRECTIO) ? 0 : -EACCES;
                goto out_digsig;
        }

        if (!pathname)  /* ima_rdwr_violation possibly pre-fetched */
                pathname = ima_d_path(&file->f_path, &pathbuf);

        if (action & IMA_MEASURE)
                ima_store_measurement(iint, file, pathname,
                                      xattr_value, xattr_len);
        if (action & IMA_APPRAISE_SUBMASK)
                rc = ima_appraise_measurement(func, iint, file, pathname,
                                              xattr_value, xattr_len, opened);
        if (action & IMA_AUDIT)
                ima_audit_measurement(iint, pathname);

out_digsig:
        if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG))
                rc = -EACCES;
        kfree(xattr_value);
out_free:
        if (pathbuf)
                __putname(pathbuf);
out:
        inode_unlock(inode);
        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, 0, MAY_EXEC,
                                           MMAP_CHECK, 0);
        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, NULL, 0, MAY_EXEC,
                                   BPRM_CHECK, 0);
}

/**
 * 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, int opened)
{
        return process_measurement(file, NULL, 0,
                                   mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
                                   FILE_CHECK, opened);
}
EXPORT_SYMBOL_GPL(ima_file_check);

/**
 * ima_read_file - pre-measure/appraise hook decision based on policy
 * @file: pointer to the file to be measured/appraised/audit
 * @read_id: caller identifier
 *
 * Permit reading a file based on policy. The policy rules are written
 * in terms of the policy identifier.  Appraising the integrity of
 * a file requires a file descriptor.
 *
 * For permission return 0, otherwise return -EACCES.
 */
int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
{
        if (!file && read_id == READING_MODULE) {
#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 0;
}

static int read_idmap[READING_MAX_ID] = {
        [READING_FIRMWARE] = FIRMWARE_CHECK,
        [READING_MODULE] = MODULE_CHECK,
        [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
        [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK,
        [READING_POLICY] = POLICY_CHECK
};

/**
 * ima_post_read_file - in memory collect/appraise/audit measurement
 * @file: pointer to the file to be measured/appraised/audit
 * @buf: pointer to in memory file contents
 * @size: size of in memory file contents
 * @read_id: caller identifier
 *
 * Measure/appraise/audit in memory file based on policy.  Policy rules
 * are written in terms of a policy identifier.
 *
 * 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_post_read_file(struct file *file, void *buf, loff_t size,
                       enum kernel_read_file_id read_id)
{
        enum ima_hooks func;

        if (!file && read_id == READING_FIRMWARE) {
                if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
                    (ima_appraise & IMA_APPRAISE_ENFORCE))
                        return -EACCES; /* INTEGRITY_UNKNOWN */
                return 0;
        }

        if (!file && read_id == READING_MODULE) /* MODULE_SIG_FORCE enabled */
                return 0;

        if (!file || !buf || size == 0) { /* should never happen */
                if (ima_appraise & IMA_APPRAISE_ENFORCE)
                        return -EACCES;
                return 0;
        }

        func = read_idmap[read_id] ?: FILE_CHECK;
        return process_measurement(file, buf, size, MAY_READ, func, 0);
}

static int __init init_ima(void)
{
        int error;

        hash_setup(CONFIG_IMA_DEFAULT_HASH);
        error = ima_init();
        if (!error) {
                ima_initialized = 1;
                ima_update_policy_flag();
        }
        return error;
}

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

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