ax25_uid.c

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/*
 * 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; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Copyright (C) Jonathan Naylor G4KLX ([email protected])
 */

#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <asm/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/notifier.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/netfilter.h>
#include <linux/sysctl.h>
#include <linux/export.h>
#include <net/ip.h>
#include <net/arp.h>

/*
 *  Callsign/UID mapper. This is in kernel space for security on multi-amateur machines.
 */

static HLIST_HEAD(ax25_uid_list);
static DEFINE_RWLOCK(ax25_uid_lock);

int ax25_uid_policy;

EXPORT_SYMBOL(ax25_uid_policy);

ax25_uid_assoc *ax25_findbyuid(kuid_t uid)
{
    ax25_uid_assoc *ax25_uid, *res = NULL;
    struct hlist_node *node;

    read_lock(&ax25_uid_lock);
    ax25_uid_for_each(ax25_uid, node, &ax25_uid_list) {
        if (uid_eq(ax25_uid->uid, uid)) {
            ax25_uid_hold(ax25_uid);
            res = ax25_uid;
            break;
        }
    }
    read_unlock(&ax25_uid_lock);

    return res;
}

EXPORT_SYMBOL(ax25_findbyuid);

int ax25_uid_ioctl(int cmd, struct sockaddr_ax25 *sax)
{
    ax25_uid_assoc *ax25_uid;
    struct hlist_node *node;
    ax25_uid_assoc *user;
    unsigned long res;

    switch (cmd) {
    case SIOCAX25GETUID:
        res = -ENOENT;
        read_lock(&ax25_uid_lock);
        ax25_uid_for_each(ax25_uid, node, &ax25_uid_list) {
            if (ax25cmp(&sax->sax25_call, &ax25_uid->call) == 0) {
                res = from_kuid_munged(current_user_ns(), ax25_uid->uid);
                break;
            }
        }
        read_unlock(&ax25_uid_lock);

        return res;

    case SIOCAX25ADDUID:
    {
        kuid_t sax25_kuid;
        if (!capable(CAP_NET_ADMIN))
            return -EPERM;
        sax25_kuid = make_kuid(current_user_ns(), sax->sax25_uid);
        if (!uid_valid(sax25_kuid))
            return -EINVAL;
        user = ax25_findbyuid(sax25_kuid);
        if (user) {
            ax25_uid_put(user);
            return -EEXIST;
        }
        if (sax->sax25_uid == 0)
            return -EINVAL;
        if ((ax25_uid = kmalloc(sizeof(*ax25_uid), GFP_KERNEL)) == NULL)
            return -ENOMEM;

        atomic_set(&ax25_uid->refcount, 1);
        ax25_uid->uid  = sax25_kuid;
        ax25_uid->call = sax->sax25_call;

        write_lock(&ax25_uid_lock);
        hlist_add_head(&ax25_uid->uid_node, &ax25_uid_list);
        write_unlock(&ax25_uid_lock);

        return 0;
    }
    case SIOCAX25DELUID:
        if (!capable(CAP_NET_ADMIN))
            return -EPERM;

        ax25_uid = NULL;
        write_lock(&ax25_uid_lock);
        ax25_uid_for_each(ax25_uid, node, &ax25_uid_list) {
            if (ax25cmp(&sax->sax25_call, &ax25_uid->call) == 0)
                break;
        }
        if (ax25_uid == NULL) {
            write_unlock(&ax25_uid_lock);
            return -ENOENT;
        }
        hlist_del_init(&ax25_uid->uid_node);
        ax25_uid_put(ax25_uid);
        write_unlock(&ax25_uid_lock);

        return 0;

    default:
        return -EINVAL;
    }

    return -EINVAL; /*NOTREACHED */
}

#ifdef CONFIG_PROC_FS

static void *ax25_uid_seq_start(struct seq_file *seq, loff_t *pos)
    __acquires(ax25_uid_lock)
{
    read_lock(&ax25_uid_lock);
    return seq_hlist_start_head(&ax25_uid_list, *pos);
}

static void *ax25_uid_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
    return seq_hlist_next(v, &ax25_uid_list, pos);
}

static void ax25_uid_seq_stop(struct seq_file *seq, void *v)
    __releases(ax25_uid_lock)
{
    read_unlock(&ax25_uid_lock);
}

static int ax25_uid_seq_show(struct seq_file *seq, void *v)
{
    char buf[11];

    if (v == SEQ_START_TOKEN)
        seq_printf(seq, "Policy: %d\n", ax25_uid_policy);
    else {
        struct ax25_uid_assoc *pt;

        pt = hlist_entry(v, struct ax25_uid_assoc, uid_node);
        seq_printf(seq, "%6d %s\n",
            from_kuid_munged(seq_user_ns(seq), pt->uid),
            ax2asc(buf, &pt->call));
    }
    return 0;
}

static const struct seq_operations ax25_uid_seqops = {
    .start = ax25_uid_seq_start,
    .next = ax25_uid_seq_next,
    .stop = ax25_uid_seq_stop,
    .show = ax25_uid_seq_show,
};

static int ax25_uid_info_open(struct inode *inode, struct file *file)
{
    return seq_open(file, &ax25_uid_seqops);
}

const struct file_operations ax25_uid_fops = {
    .owner = THIS_MODULE,
    .open = ax25_uid_info_open,
    .read = seq_read,
    .llseek = seq_lseek,
    .release = seq_release,
};

#endif

/*
 *  Free all memory associated with UID/Callsign structures.
 */
void __exit ax25_uid_free(void)
{
    ax25_uid_assoc *ax25_uid;
    struct hlist_node *node;

    write_lock(&ax25_uid_lock);
again:
    ax25_uid_for_each(ax25_uid, node, &ax25_uid_list) {
        hlist_del_init(&ax25_uid->uid_node);
        ax25_uid_put(ax25_uid);
        goto again;
    }
    write_unlock(&ax25_uid_lock);
}