/*
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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 <linux/iversion.h>
#include <linux/fs.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;
                else
                        return 1;
                goto out;
        }

        for (i = 0; i < HASH_ALGO__LAST; i++) {
                if (strcmp(str, hash_algo_name[i]) == 0) {
                        ima_hash_algo = i;
                        break;
                }
        }
        if (i == HASH_ALGO__LAST)
                return 1;
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,
                                     char *filename)
{
        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 && test_bit(IMA_MUST_MEASURE,
                                                &iint->atomic_flags))
                                send_tomtou = true;
                }
        } else {
                if (must_measure)
                        set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
                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, filename);

        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;
        bool update;

        if (!(mode & FMODE_WRITE))
                return;

        mutex_lock(&iint->mutex);
        if (atomic_read(&inode->i_writecount) == 1) {
                update = test_and_clear_bit(IMA_UPDATE_XATTR,
                                            &iint->atomic_flags);
                if (!IS_I_VERSION(inode) ||
                    !inode_eq_iversion(inode, iint->version) ||
                    (iint->flags & IMA_NEW_FILE)) {
                        iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
                        iint->measured_pcrs = 0;
                        if (update)
                                ima_update_xattr(iint, file);
                }
        }
        mutex_unlock(&iint->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 (!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, const struct cred *cred,
                               u32 secid, 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;
        char filename[NAME_MAX];
        const char *pathname = NULL;
        int rc = 0, action, must_appraise = 0;
        int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
        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, cred, secid, mask, func, &pcr);
        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)
                        rc = -ENOMEM;
        }

        if (!rc && violation_check)
                ima_rdwr_violation_check(file, iint, action & IMA_MEASURE,
                                         &pathbuf, &pathname, filename);

        inode_unlock(inode);

        if (rc)
                goto out;
        if (!action)
                goto out;

        mutex_lock(&iint->mutex);

        if (test_and_clear_bit(IMA_CHANGE_ATTR, &iint->atomic_flags))
                /* reset appraisal flags if ima_inode_post_setattr was called */
                iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
                                 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
                                 IMA_ACTION_FLAGS);

        /*
         * Re-evaulate the file if either the xattr has changed or the
         * kernel has no way of detecting file change on the filesystem.
         * (Limited to privileged mounted filesystems.)
         */
        if (test_and_clear_bit(IMA_CHANGE_XATTR, &iint->atomic_flags) ||
            ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
             !(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) &&
             !(action & IMA_FAIL_UNVERIFIABLE_SIGS))) {
                iint->flags &= ~IMA_DONE_MASK;
                iint->measured_pcrs = 0;
        }

        /* 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 ^ IMA_MEASURED)) >> 1);

        /* If target pcr is already measured, unset IMA_MEASURE action */
        if ((action & IMA_MEASURE) && (iint->measured_pcrs & (0x1 << pcr)))
                action ^= IMA_MEASURE;

        /* HASH sets the digital signature and update flags, nothing else */
        if ((action & IMA_HASH) &&
            !(test_bit(IMA_DIGSIG, &iint->atomic_flags))) {
                xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
                if ((xattr_value && xattr_len > 2) &&
                    (xattr_value->type == EVM_IMA_XATTR_DIGSIG))
                        set_bit(IMA_DIGSIG, &iint->atomic_flags);
                iint->flags |= IMA_HASHED;
                action ^= IMA_HASH;
                set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
        }

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

        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_dentry(file), &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 && rc != -EBADF && rc != -EINVAL)
                goto out_locked;

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

        if (action & IMA_MEASURE)
                ima_store_measurement(iint, file, pathname,
                                      xattr_value, xattr_len, pcr);
        if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
                inode_lock(inode);
                rc = ima_appraise_measurement(func, iint, file, pathname,
                                              xattr_value, xattr_len, opened);
                inode_unlock(inode);
        }
        if (action & IMA_AUDIT)
                ima_audit_measurement(iint, pathname);

        if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO))
                rc = 0;
out_locked:
        if ((mask & MAY_WRITE) && test_bit(IMA_DIGSIG, &iint->atomic_flags) &&
             !(iint->flags & IMA_NEW_FILE))
                rc = -EACCES;
        mutex_unlock(&iint->mutex);
        kfree(xattr_value);
out:
        if (pathbuf)
                __putname(pathbuf);
        if (must_appraise) {
                if (rc && (ima_appraise & IMA_APPRAISE_ENFORCE))
                        return -EACCES;
                if (file->f_mode & FMODE_WRITE)
                        set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
        }
        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)
{
        u32 secid;

        if (file && (prot & PROT_EXEC)) {
                security_task_getsecid(current, &secid);
                return process_measurement(file, current_cred(), secid, 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)
{
        int ret;
        u32 secid;

        security_task_getsecid(current, &secid);
        ret = process_measurement(bprm->file, current_cred(), secid, NULL, 0,
                                  MAY_EXEC, BPRM_CHECK, 0);
        if (ret)
                return ret;

        security_cred_getsecid(bprm->cred, &secid);
        return process_measurement(bprm->file, bprm->cred, secid, NULL, 0,
                                   MAY_EXEC, CREDS_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, MAY_EXEC or MAY_APPEND
 *
 * 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)
{
        u32 secid;

        security_task_getsecid(current, &secid);
        return process_measurement(file, current_cred(), secid, NULL, 0,
                                   mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
                                           MAY_APPEND), FILE_CHECK, opened);
}
EXPORT_SYMBOL_GPL(ima_file_check);

/**
 * ima_post_path_mknod - mark as a new inode
 * @dentry: newly created dentry
 *
 * Mark files created via the mknodat syscall as new, so that the
 * file data can be written later.
 */
void ima_post_path_mknod(struct dentry *dentry)
{
        struct integrity_iint_cache *iint;
        struct inode *inode = dentry->d_inode;
        int must_appraise;

        must_appraise = ima_must_appraise(inode, MAY_ACCESS, FILE_CHECK);
        if (!must_appraise)
                return;

        iint = integrity_inode_get(inode);
        if (iint)
                iint->flags |= IMA_NEW_FILE;
}

/**
 * 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)
{
        bool sig_enforce = is_module_sig_enforced();

        if (!file && read_id == READING_MODULE) {
                if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES) &&
                    (ima_appraise & IMA_APPRAISE_ENFORCE)) {
                        pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
                        return -EACCES; /* INTEGRITY_UNKNOWN */
                }
                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;
        u32 secid;

        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;

        /* permit signed certs */
        if (!file && read_id == READING_X509_CERTIFICATE)
                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;
        security_task_getsecid(current, &secid);
        return process_measurement(file, current_cred(), secid, buf, size,
                                   MAY_READ, func, 0);
}

static int __init init_ima(void)
{
        int error;

        ima_init_template_list();
        hash_setup(CONFIG_IMA_DEFAULT_HASH);
        error = ima_init();

        if (error && strcmp(hash_algo_name[ima_hash_algo],
                            CONFIG_IMA_DEFAULT_HASH) != 0) {
                pr_info("Allocating %s failed, going to use default hash algorithm %s\n",
                        hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH);
                hash_setup_done = 0;
                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");