/*
 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
 *
 * Authors:
 * Kylene Hall <kjhall@us.ibm.com>
 * Reiner Sailer <sailer@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_fs.c
 *      implemenents security file system for reporting
 *      current measurement list and IMA statistics
 */
#include <linux/fcntl.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/rculist.h>
#include <linux/rcupdate.h>
#include <linux/parser.h>

#include "ima.h"

static int valid_policy = 1;
#define TMPBUFLEN 12
static ssize_t ima_show_htable_value(char __user *buf, size_t count,
                                     loff_t *ppos, atomic_long_t *val)
{
        char tmpbuf[TMPBUFLEN];
        ssize_t len;

        len = scnprintf(tmpbuf, TMPBUFLEN, "%li\n", atomic_long_read(val));
        return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
}

static ssize_t ima_show_htable_violations(struct file *filp,
                                          char __user *buf,
                                          size_t count, loff_t *ppos)
{
        return ima_show_htable_value(buf, count, ppos, &ima_htable.violations);
}

static const struct file_operations ima_htable_violations_ops = {
        .read = ima_show_htable_violations
};

static ssize_t ima_show_measurements_count(struct file *filp,
                                           char __user *buf,
                                           size_t count, loff_t *ppos)
{
        return ima_show_htable_value(buf, count, ppos, &ima_htable.len);

}

static const struct file_operations ima_measurements_count_ops = {
        .read = ima_show_measurements_count
};

/* returns pointer to hlist_node */
static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
{
        loff_t l = *pos;
        struct ima_queue_entry *qe;

        /* we need a lock since pos could point beyond last element */
        rcu_read_lock();
        list_for_each_entry_rcu(qe, &ima_measurements, later) {
                if (!l--) {
                        rcu_read_unlock();
                        return qe;
                }
        }
        rcu_read_unlock();
        return NULL;
}

static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
{
        struct ima_queue_entry *qe = v;

        /* lock protects when reading beyond last element
         * against concurrent list-extension
         */
        rcu_read_lock();
        qe = list_entry_rcu(qe->later.next,
                            struct ima_queue_entry, later);
        rcu_read_unlock();
        (*pos)++;

        return (&qe->later == &ima_measurements) ? NULL : qe;
}

static void ima_measurements_stop(struct seq_file *m, void *v)
{
}

static void ima_putc(struct seq_file *m, void *data, int datalen)
{
        while (datalen--)
                seq_putc(m, *(char *)data++);
}

/* print format:
 *       32bit-le=pcr#
 *       char[20]=template digest
 *       32bit-le=template name size
 *       char[n]=template name
 *       eventdata[n]=template specific data
 */
static int ima_measurements_show(struct seq_file *m, void *v)
{
        /* the list never shrinks, so we don't need a lock here */
        struct ima_queue_entry *qe = v;
        struct ima_template_entry *e;
        int namelen;
        u32 pcr = CONFIG_IMA_MEASURE_PCR_IDX;

        /* get entry */
        e = qe->entry;
        if (e == NULL)
                return -1;

        /*
         * 1st: PCRIndex
         * PCR used is always the same (config option) in
         * little-endian format
         */
        ima_putc(m, &pcr, sizeof pcr);

        /* 2nd: template digest */
        ima_putc(m, e->digest, IMA_DIGEST_SIZE);

        /* 3rd: template name size */
        namelen = strlen(e->template_name);
        ima_putc(m, &namelen, sizeof namelen);

        /* 4th:  template name */
        ima_putc(m, (void *)e->template_name, namelen);

        /* 5th:  template specific data */
        ima_template_show(m, (struct ima_template_data *)&e->template,
                          IMA_SHOW_BINARY);
        return 0;
}

static const struct seq_operations ima_measurments_seqops = {
        .start = ima_measurements_start,
        .next = ima_measurements_next,
        .stop = ima_measurements_stop,
        .show = ima_measurements_show
};

static int ima_measurements_open(struct inode *inode, struct file *file)
{
        return seq_open(file, &ima_measurments_seqops);
}

static const struct file_operations ima_measurements_ops = {
        .open = ima_measurements_open,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = seq_release,
};

static void ima_print_digest(struct seq_file *m, u8 *digest)
{
        int i;

        for (i = 0; i < IMA_DIGEST_SIZE; i++)
                seq_printf(m, "%02x", *(digest + i));
}

void ima_template_show(struct seq_file *m, void *e, enum ima_show_type show)
{
        struct ima_template_data *entry = e;
        int namelen;

        switch (show) {
        case IMA_SHOW_ASCII:
                ima_print_digest(m, entry->digest);
                seq_printf(m, " %s\n", entry->file_name);
                break;
        case IMA_SHOW_BINARY:
                ima_putc(m, entry->digest, IMA_DIGEST_SIZE);

                namelen = strlen(entry->file_name);
                ima_putc(m, &namelen, sizeof namelen);
                ima_putc(m, entry->file_name, namelen);
        default:
                break;
        }
}

/* print in ascii */
static int ima_ascii_measurements_show(struct seq_file *m, void *v)
{
        /* the list never shrinks, so we don't need a lock here */
        struct ima_queue_entry *qe = v;
        struct ima_template_entry *e;

        /* get entry */
        e = qe->entry;
        if (e == NULL)
                return -1;

        /* 1st: PCR used (config option) */
        seq_printf(m, "%2d ", CONFIG_IMA_MEASURE_PCR_IDX);

        /* 2nd: SHA1 template hash */
        ima_print_digest(m, e->digest);

        /* 3th:  template name */
        seq_printf(m, " %s ", e->template_name);

        /* 4th:  template specific data */
        ima_template_show(m, (struct ima_template_data *)&e->template,
                          IMA_SHOW_ASCII);
        return 0;
}

static const struct seq_operations ima_ascii_measurements_seqops = {
        .start = ima_measurements_start,
        .next = ima_measurements_next,
        .stop = ima_measurements_stop,
        .show = ima_ascii_measurements_show
};

static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
{
        return seq_open(file, &ima_ascii_measurements_seqops);
}

static const struct file_operations ima_ascii_measurements_ops = {
        .open = ima_ascii_measurements_open,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = seq_release,
};

static ssize_t ima_write_policy(struct file *file, const char __user *buf,
                                size_t datalen, loff_t *ppos)
{
        char *data;
        int rc;

        if (datalen >= PAGE_SIZE)
                return -ENOMEM;
        if (*ppos != 0) {
                /* No partial writes. */
                return -EINVAL;
        }
        data = kmalloc(datalen + 1, GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        if (copy_from_user(data, buf, datalen)) {
                kfree(data);
                return -EFAULT;
        }
        *(data + datalen) = '\0';
        rc = ima_parse_add_rule(data);
        if (rc < 0) {
                datalen = -EINVAL;
                valid_policy = 0;
        }

        kfree(data);
        return datalen;
}

static struct dentry *ima_dir;
static struct dentry *binary_runtime_measurements;
static struct dentry *ascii_runtime_measurements;
static struct dentry *runtime_measurements_count;
static struct dentry *violations;
static struct dentry *ima_policy;

static atomic_t policy_opencount = ATOMIC_INIT(1);
/*
 * ima_open_policy: sequentialize access to the policy file
 */
int ima_open_policy(struct inode * inode, struct file * filp)
{
        /* No point in being allowed to open it if you aren't going to write */
        if (!(filp->f_flags & O_WRONLY))
                return -EACCES;
        if (atomic_dec_and_test(&policy_opencount))
                return 0;
        return -EBUSY;
}

/*
 * ima_release_policy - start using the new measure policy rules.
 *
 * Initially, ima_measure points to the default policy rules, now
 * point to the new policy rules, and remove the securityfs policy file,
 * assuming a valid policy.
 */
static int ima_release_policy(struct inode *inode, struct file *file)
{
        if (!valid_policy) {
                ima_delete_rules();
                valid_policy = 1;
                atomic_set(&policy_opencount, 1);
                return 0;
        }
        ima_update_policy();
        securityfs_remove(ima_policy);
        ima_policy = NULL;
        return 0;
}

static const struct file_operations ima_measure_policy_ops = {
        .open = ima_open_policy,
        .write = ima_write_policy,
        .release = ima_release_policy
};

int __init ima_fs_init(void)
{
        ima_dir = securityfs_create_dir("ima", NULL);
        if (IS_ERR(ima_dir))
                return -1;

        binary_runtime_measurements =
            securityfs_create_file("binary_runtime_measurements",
                                   S_IRUSR | S_IRGRP, ima_dir, NULL,
                                   &ima_measurements_ops);
        if (IS_ERR(binary_runtime_measurements))
                goto out;

        ascii_runtime_measurements =
            securityfs_create_file("ascii_runtime_measurements",
                                   S_IRUSR | S_IRGRP, ima_dir, NULL,
                                   &ima_ascii_measurements_ops);
        if (IS_ERR(ascii_runtime_measurements))
                goto out;

        runtime_measurements_count =
            securityfs_create_file("runtime_measurements_count",
                                   S_IRUSR | S_IRGRP, ima_dir, NULL,
                                   &ima_measurements_count_ops);
        if (IS_ERR(runtime_measurements_count))
                goto out;

        violations =
            securityfs_create_file("violations", S_IRUSR | S_IRGRP,
                                   ima_dir, NULL, &ima_htable_violations_ops);
        if (IS_ERR(violations))
                goto out;

        ima_policy = securityfs_create_file("policy",
                                            S_IWUSR,
                                            ima_dir, NULL,
                                            &ima_measure_policy_ops);
        if (IS_ERR(ima_policy))
                goto out;

        return 0;
out:
        securityfs_remove(runtime_measurements_count);
        securityfs_remove(ascii_runtime_measurements);
        securityfs_remove(binary_runtime_measurements);
        securityfs_remove(ima_dir);
        securityfs_remove(ima_policy);
        return -1;
}

void __exit ima_fs_cleanup(void)
{
        securityfs_remove(violations);
        securityfs_remove(runtime_measurements_count);
        securityfs_remove(ascii_runtime_measurements);
        securityfs_remove(binary_runtime_measurements);
        securityfs_remove(ima_dir);
        securityfs_remove(ima_policy);
}