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    Subject[PATCH] 2.5.42: accessfs 3/3: access permission filesystem
    From
    Date
    This patch adds a new permission managing file system. Furthermore, it
    adds two modules, which make use of this file system.

    One module allows granting capabilities based on user-/groupid. The
    second module allows to grant access to lower numbered ports based on
    user-/groupid, too.

    Changes:
    - fixed module reference counting
    - fixed oops, when init_capabilities() failed
    - my first try at locking. It seems to work here, but I do have UP
    only. So SMP might do nasty things, I just don't know.

    Regards, Olaf.

    diff -urN a/MAINTAINERS b/MAINTAINERS
    --- a/MAINTAINERS Sat Oct 12 14:24:11 2002
    +++ b/MAINTAINERS Sat Oct 12 17:38:40 2002
    @@ -138,6 +138,12 @@
    L: linux-aio@kvack.org
    S: Supported

    +ACCESS FILE SYSTEM
    +P: Olaf Dietsche
    +M: olaf.dietsche@t-online.de
    +M: olaf.dietsche@gmx.net
    +S: Maintained
    +
    ACENIC DRIVER
    P: Jes Sorensen
    M: jes@trained-monkey.org
    diff -urN a/fs/Config.in b/fs/Config.in
    --- a/fs/Config.in Sat Oct 12 14:24:17 2002
    +++ b/fs/Config.in Sat Oct 12 17:38:40 2002
    @@ -108,6 +108,9 @@
    define_bool CONFIG_QUOTACTL y
    fi

    +dep_tristate 'Accessfs support (EXPERIMENTAL)' CONFIG_ACCESS_FS $CONFIG_EXPERIMENTAL
    +source fs/accessfs/Config.in
    +
    if [ "$CONFIG_NET" = "y" ]; then

    mainmenu_option next_comment
    diff -urN a/fs/Makefile b/fs/Makefile
    --- a/fs/Makefile Sat Oct 12 14:24:17 2002
    +++ b/fs/Makefile Sat Oct 12 17:38:40 2002
    @@ -84,5 +84,6 @@
    obj-$(CONFIG_SUN_OPENPROMFS) += openpromfs/
    obj-$(CONFIG_JFS_FS) += jfs/
    obj-$(CONFIG_XFS_FS) += xfs/
    +obj-$(CONFIG_ACCESS_FS) += accessfs/

    include $(TOPDIR)/Rules.make
    diff -urN a/fs/accessfs/Config.help b/fs/accessfs/Config.help
    --- a/fs/accessfs/Config.help Thu Jan 1 01:00:00 1970
    +++ b/fs/accessfs/Config.help Sat Oct 12 17:38:40 2002
    @@ -0,0 +1,68 @@
    +Accessfs support (EXPERIMENTAL)
    +CONFIG_ACCESS_FS
    + This is a new file system to manage permissions. It is not very
    + useful on its own. You need to enable other options below.
    +
    + The recommended mount point for this file-system is /proc/access,
    + which will appear automatically in the /proc filesystem.
    +
    + If you're unsure, say N.
    +
    +User permission based IP ports
    +CONFIG_ACCESSFS_USER_PORTS
    + If you say Y here, you will be able to control access to IP ports
    + based on user-/groupid. For this to work, you must say Y
    + to CONFIG_NET_HOOKS.
    +
    + With this option, there's no need anymore to run internet daemons
    + as root. You can individually configure which user/program can bind to
    + protected ports (by default, below 1024).
    +
    + For example, you can say, user www is allowed to bind to port 80 or
    + user mail is allowed to bind to port 25. Then, you can run apache as
    + user www and sendmail as user mail. Now, you don't have to rely on
    + apache or sendmail giving up superuser rights to enhance security.
    +
    + To use this option, you need to mount the access file system
    + and do a chown on the appropriate ports:
    +
    + # mount -t accessfs none /proc/access
    + # chown www /proc/access/net/ip/bind/80
    + # chown mail /proc/access/net/ip/bind/25
    +
    + You can grant access to a group for individual ports as well. Just say:
    +
    + # chgrp lp /proc/access/net/ip/bind/515
    + # chown g+x /proc/access/net/ip/bind/515
    +
    + If you're unsure, say N.
    +
    +Range of protected ports
    +CONFIG_ACCESSFS_PROT_SOCK
    + Here you can extend the range of protected ports. This is
    + from 1-1023 inclusive on normal unix systems. One use for this
    + could be to reserve ports for X11 (port 6000) or database
    + servers (port 3306 for mysql), so nobody else could grab this port.
    + The default permission for extended ports is --x--x--x.
    +
    + If you build this as a module, you can specify the range of
    + protected ports at module load time (max_prot_sock).
    +
    + If you're unsure, say 1024.
    +
    +User permission based capabilities
    +CONFIG_ACCESSFS_USER_CAPABILITIES
    + If you say Y here, you will be able to grant capabilities based on
    + user-/groupid (root by default). For this to work, you must say M or
    + N to CONFIG_SECURITY_CAPABILITIES.
    +
    + For example you can create a group raw and change the capability
    + net_raw to this group:
    +
    + # chgrp raw /proc/access/capabilities/net_raw
    + # chmod ug+x /proc/access/capabilities/net_raw
    + # chgrp raw /sbin/ping
    + # chmod u-s /sbin/ping; chmod g+s /sbin/ping
    +
    + If you're unsure, say N.
    +
    diff -urN a/fs/accessfs/Config.in b/fs/accessfs/Config.in
    --- a/fs/accessfs/Config.in Thu Jan 1 01:00:00 1970
    +++ b/fs/accessfs/Config.in Sat Oct 12 17:38:40 2002
    @@ -0,0 +1,11 @@
    +#
    +# Accessfs configuration
    +#
    +
    +if [ "$CONFIG_ACCESS_FS" != "n" ]; then
    + dep_tristate ' User permission based capabilities' CONFIG_ACCESSFS_USER_CAPABILITIES $CONFIG_ACCESS_FS
    + dep_tristate ' User permission based IP ports' CONFIG_ACCESSFS_USER_PORTS $CONFIG_ACCESS_FS
    + if [ "$CONFIG_ACCESSFS_USER_PORTS" != "n" ]; then
    + int ' Range of protected ports (1024-65536)' CONFIG_ACCESSFS_PROT_SOCK 1024
    + fi
    +fi
    diff -urN a/fs/accessfs/Makefile b/fs/accessfs/Makefile
    --- a/fs/accessfs/Makefile Thu Jan 1 01:00:00 1970
    +++ b/fs/accessfs/Makefile Sun Oct 13 16:44:35 2002
    @@ -0,0 +1,13 @@
    +#
    +# Makefile for the linux accessfs routines.
    +#
    +
    +obj-$(CONFIG_ACCESS_FS) += accessfs.o
    +obj-$(CONFIG_ACCESSFS_USER_CAPABILITIES) += usercaps.o
    +obj-$(CONFIG_ACCESSFS_USER_PORTS) += userports.o
    +export-objs := inode.o
    +accessfs-objs := inode.o
    +usercaps-objs := capabilities.o
    +userports-objs := ip.o
    +
    +include $(TOPDIR)/Rules.make
    diff -urN a/fs/accessfs/capabilities.c b/fs/accessfs/capabilities.c
    --- a/fs/accessfs/capabilities.c Thu Jan 1 01:00:00 1970
    +++ b/fs/accessfs/capabilities.c Sun Oct 13 18:50:48 2002
    @@ -0,0 +1,120 @@
    +/* Copyright (c) 2002 Olaf Dietsche
    + *
    + * User based capabilities for Linux.
    + */
    +
    +#include <linux/accessfs_fs.h>
    +#include <linux/init.h>
    +#include <linux/module.h>
    +#include <linux/security.h>
    +
    +static struct access_attr caps[29];
    +static const char *names[] = {
    + "chown",
    + "dac_override",
    + "dac_read_search",
    + "fowner",
    + "fsetid",
    + "kill",
    + "setgid",
    + "setuid",
    + "setpcap",
    + "linux_immutable",
    + "net_bind_service",
    + "net_broadcast",
    + "net_admin",
    + "net_raw",
    + "ipc_lock",
    + "ipc_owner",
    + "sys_module",
    + "sys_rawio",
    + "sys_chroot",
    + "sys_ptrace",
    + "sys_pacct",
    + "sys_admin",
    + "sys_boot",
    + "sys_nice",
    + "sys_resource",
    + "sys_time",
    + "sys_tty_config",
    + "mknod",
    + "lease"
    +};
    +
    +static int accessfs_capable(struct task_struct *tsk, int cap)
    +{
    + if (accessfs_permitted(&caps[cap], MAY_EXEC)) {
    + /* capability granted */
    + tsk->flags |= PF_SUPERPRIV;
    + return 0;
    + }
    +
    + /* capability denied */
    + return -EPERM;
    +}
    +
    +static struct security_operations accessfs_security_ops = {
    + .capable = accessfs_capable,
    +};
    +
    +static void __init fill_empty_from(struct security_operations *to, const struct security_operations *from)
    +{
    + unsigned long *__from = (unsigned long *) from;
    + unsigned long *__to = (unsigned long *) to;
    + unsigned long *__end = __to + sizeof(*to) / sizeof(unsigned long *);
    + while (__to != __end) {
    + if (*__to == 0)
    + *__to = *__from;
    +
    + ++__to;
    + ++__from;
    + }
    +}
    +
    +static void unregister_capabilities(struct accessfs_direntry *dir, int n)
    +{
    + int i;
    + for (i = 0; i < n; ++i) {
    + accessfs_unregister(dir, names[i]);
    + }
    +}
    +
    +static int __init init_capabilities(void)
    +{
    + struct accessfs_direntry *dir = accessfs_make_dirpath("capabilities");
    + int i, rc;
    + if (dir == 0)
    + return -ENOTDIR;
    +
    + for (i = 0; i < sizeof(caps) / sizeof(caps[0]); ++i) {
    + caps[i].uid = 0;
    + caps[i].gid = 0;
    + caps[i].mode = S_IXUSR;
    + rc = accessfs_register(dir, names[i], &caps[i]);
    + if (rc != 0) {
    + unregister_capabilities(dir, i);
    + return rc;
    + }
    + }
    +
    + fill_empty_from(&accessfs_security_ops, security_ops);
    + rc = register_security(&accessfs_security_ops);
    + if (rc != 0)
    + unregister_capabilities(dir, sizeof(names) / sizeof(names[0]));
    +
    + return rc;
    +}
    +
    +static void __exit exit_capabilities(void)
    +{
    + struct accessfs_direntry *dir = accessfs_make_dirpath("capabilities");
    + unregister_security(&accessfs_security_ops);
    + unregister_capabilities(dir, sizeof(names) / sizeof(names[0]));
    +}
    +
    +module_init(init_capabilities)
    +module_exit(exit_capabilities)
    +
    +MODULE_AUTHOR("Olaf Dietsche");
    +MODULE_DESCRIPTION("User based capabilities");
    +MODULE_LICENSE("GPL");
    diff -urN a/fs/accessfs/inode.c b/fs/accessfs/inode.c
    --- a/fs/accessfs/inode.c Thu Jan 1 01:00:00 1970
    +++ b/fs/accessfs/inode.c Sun Oct 13 19:17:39 2002
    @@ -0,0 +1,429 @@
    +/* Copyright (c) 2001 Olaf Dietsche
    + *
    + * Access permission filesystem for Linux.
    + *
    + * 2002 Ben Clifford, create mount point at /proc/access
    + * 2002 Ben Clifford, trying to make it work under 2.5.5-dj2
    + * (see comments: BENC255 for reminders and todos)
    + *
    + *
    + * BENC255: the kernel doesn't lock BKL for us when entering methods
    + * (see Documentation/fs/porting.txt)
    + * Need to look at code here and see if we need either the BKL
    + * or our own lock - I think probably not.
    + *
    + */
    +
    +#include <linux/accessfs_fs.h>
    +#include <linux/module.h>
    +#include <linux/fs.h>
    +#include <linux/pagemap.h>
    +#include <linux/init.h>
    +#include <linux/slab.h>
    +#include <linux/string.h>
    +#include <linux/proc_fs.h>
    +
    +#include <asm/uaccess.h>
    +
    +#define ACCESSFS_MAGIC 0x3c1d36e7
    +
    +#ifdef CONFIG_PROC_FS
    +static struct proc_dir_entry *mountdir = NULL;
    +#endif
    +
    +spinlock_t accessfs_lock = SPIN_LOCK_UNLOCKED;
    +
    +static struct inode_operations accessfs_inode_operations;
    +static struct file_operations accessfs_dir_file_operations;
    +static struct inode_operations accessfs_dir_inode_operations;
    +
    +static int accessfs_statfs(struct super_block *sb, struct statfs *buf)
    +{
    + buf->f_type = ACCESSFS_MAGIC;
    + buf->f_bsize = PAGE_CACHE_SIZE;
    + buf->f_namelen = 255;
    + return 0;
    +}
    +
    +static inline void accessfs_readdir_aux(struct file *filp, struct accessfs_direntry *dir, int start, void *dirent, filldir_t filldir)
    +{
    + struct list_head *list;
    + int i;
    +
    + list = dir->children.next;
    + for (i = 2; i < start && list != &dir->children; ++i)
    + list = list->next;
    +
    + while (list != &dir->children) {
    + struct accessfs_entry *de;
    + de = list_entry(list, struct accessfs_entry, siblings);
    + if (filldir(dirent, de->name, strlen(de->name), filp->f_pos, de->ino, DT_UNKNOWN) < 0)
    + break;
    +
    + ++filp->f_pos;
    + list = list->next;
    + }
    +}
    +
    +static int accessfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
    +{
    + int i;
    + struct dentry *dentry = filp->f_dentry;
    + struct accessfs_direntry *dir;
    +
    + i = filp->f_pos;
    + switch (i) {
    + case 0:
    + if (filldir(dirent, ".", 1, i, dentry->d_inode->i_ino, DT_DIR) < 0)
    + break;
    +
    + ++i;
    + ++filp->f_pos;
    + /* NO break; */
    + case 1:
    + if (filldir(dirent, "..", 2, i, dentry->d_parent->d_inode->i_ino, DT_DIR) < 0)
    + break;
    +
    + ++i;
    + ++filp->f_pos;
    + /* NO break; */
    + default:
    + spin_lock(&accessfs_lock);
    + dir = (struct accessfs_direntry *) dentry->d_inode->u.generic_ip;
    + accessfs_readdir_aux(filp, dir, i, dirent, filldir);
    + spin_unlock(&accessfs_lock);
    + break;
    + }
    +
    + return 0;
    +}
    +
    +static struct accessfs_entry *accessfs_lookup_entry(struct accessfs_entry *pe, const char *name, int len)
    +{
    + if (S_ISDIR(pe->attr->mode)) {
    + struct list_head *list;
    + struct accessfs_direntry *dir;
    + dir = (struct accessfs_direntry *) pe;
    + list_for_each(list, &dir->children) {
    + struct accessfs_entry *de;
    + de = list_entry(list, struct accessfs_entry, siblings);
    + if (strncmp(de->name, name, len) == 0 && de->name[len] == 0)
    + return de;
    + }
    + }
    +
    + return NULL;
    +}
    +
    +static struct dentry *accessfs_lookup(struct inode *dir, struct dentry *dentry)
    +{
    + struct inode *inode = NULL;
    + struct accessfs_entry *pe;
    + spin_lock(&accessfs_lock);
    + pe = accessfs_lookup_entry(dir->u.generic_ip, dentry->d_name.name, dentry->d_name.len);
    + if (pe)
    + inode = iget(dir->i_sb, pe->ino);
    +
    + d_add(dentry, inode);
    + spin_unlock(&accessfs_lock);
    + return NULL;
    +}
    +
    +static struct accessfs_direntry accessfs_rootdir = {
    + { "/",
    + LIST_HEAD_INIT(accessfs_rootdir.node.hash),
    + LIST_HEAD_INIT(accessfs_rootdir.node.siblings),
    + 1, &accessfs_rootdir.attr },
    + NULL, LIST_HEAD_INIT(accessfs_rootdir.children),
    + { 0, 0, S_IFDIR | 0755 }
    +};
    +
    +static void accessfs_init_inode(struct inode *inode, struct accessfs_entry *pe)
    +{
    + inode->u.generic_ip = pe;
    + inode->i_uid = pe->attr->uid;
    + inode->i_gid = pe->attr->gid;
    + inode->i_mode = pe->attr->mode;
    +/*
    + inode->i_blksize = PAGE_CACHE_SIZE;
    + inode->i_blocks = 0;
    + inode->i_rdev = NODEV;
    +*/
    + inode->i_atime = inode->i_mtime = inode->i_ctime = 0;
    + switch (inode->i_mode & S_IFMT) {
    + case S_IFREG:
    + inode->i_op = &accessfs_inode_operations;
    + break;
    + case S_IFDIR:
    + inode->i_op = &accessfs_dir_inode_operations;
    + inode->i_fop = &accessfs_dir_file_operations;
    + break;
    + default:
    + printk(KERN_ERR "accessfs_init_inode(): '%s' unhandled mode=%d\n", pe->name, inode->i_mode);
    + BUG();
    + break;
    + }
    +}
    +
    +static struct inode *accessfs_get_root_inode(struct super_block *sb)
    +{
    + struct inode *inode = new_inode(sb);
    + if (inode) {
    + spin_lock(&accessfs_lock);
    +/* inode->i_ino = accessfs_rootdir.node.ino; */
    + accessfs_init_inode(inode, &accessfs_rootdir.node);
    + accessfs_rootdir.node.ino = inode->i_ino;
    + spin_unlock(&accessfs_lock);
    + }
    +
    + return inode;
    +}
    +
    +static LIST_HEAD(hash);
    +
    +static int accessfs_node_init(struct accessfs_direntry *parent, struct accessfs_entry *de, const char *name, size_t len, struct access_attr *attr, mode_t mode)
    +{
    + static unsigned long ino = 1;
    + de->name = kmalloc(len + 1, GFP_KERNEL);
    + if (de->name == NULL)
    + return -ENOMEM;
    +
    + strncpy(de->name, name, len);
    + de->name[len] = 0;
    + de->ino = ++ino;
    + de->attr = attr;
    + de->attr->uid = 0;
    + de->attr->gid = 0;
    + de->attr->mode = mode;
    + list_add_tail(&de->hash, &hash);
    + list_add_tail(&de->siblings, &parent->children);
    + return 0;
    +}
    +
    +static int accessfs_mknod(struct accessfs_direntry *dir, const char *name, struct access_attr *attr)
    +{
    + struct accessfs_entry *pe;
    + pe = kmalloc(sizeof(struct accessfs_entry), GFP_KERNEL);
    + if (pe == NULL)
    + return -ENOMEM;
    +
    + spin_lock(&accessfs_lock);
    + accessfs_node_init(dir, pe, name, strlen(name), attr, S_IFREG | attr->mode);
    + spin_unlock(&accessfs_lock);
    + return 0;
    +}
    +
    +static struct accessfs_direntry *accessfs_mkdir(struct accessfs_direntry *parent, const char *name, size_t len)
    +{
    + int error;
    + struct accessfs_direntry *dir;
    + dir = kmalloc(sizeof(struct accessfs_direntry), GFP_KERNEL);
    + if (dir == NULL)
    + return NULL;
    +
    + spin_lock(&accessfs_lock);
    + error = accessfs_node_init(parent, &dir->node, name, len, &dir->attr, S_IFDIR | 0755);
    + if (error) {
    + kfree(dir);
    + dir = 0;
    + } else {
    + dir->parent = parent;
    + INIT_LIST_HEAD(&dir->children);
    + }
    +
    + spin_unlock(&accessfs_lock);
    + return dir;
    +}
    +
    +struct accessfs_direntry *accessfs_make_dirpath(const char *name)
    +{
    + struct accessfs_direntry *dir = &accessfs_rootdir;
    + const char *slash;
    + do {
    + struct accessfs_entry *de;
    + size_t len;
    + while (*name == '/')
    + ++name;
    +
    + slash = strchr(name, '/');
    + len = slash ? slash - name : strlen(name);
    + de = accessfs_lookup_entry(&dir->node, name, len);
    + if (de == NULL) {
    + dir = accessfs_mkdir(dir, name, len);
    + } else if (S_ISDIR(de->attr->mode)) {
    + dir = (struct accessfs_direntry *) de;
    + } else {
    + return NULL;
    + }
    +
    + if (dir == NULL)
    + return NULL;
    +
    + name = slash + 1;
    + } while (slash != NULL);
    +
    + return dir;
    +}
    +
    +static void accessfs_unlink(struct accessfs_entry *pe)
    +{
    + spin_lock(&accessfs_lock);
    + list_del(&pe->hash);
    + list_del(&pe->siblings);
    + kfree(pe->name);
    + kfree(pe);
    + spin_unlock(&accessfs_lock);
    +}
    +
    +static int accessfs_notify_change(struct dentry *dentry, struct iattr *iattr)
    +{
    + struct inode *i = dentry->d_inode;
    + int error = inode_setattr(i, iattr);
    + if (!error) {
    + struct accessfs_entry *pe;
    + pe = (struct accessfs_entry *) i->u.generic_ip;
    + pe->attr->uid = i->i_uid;
    + pe->attr->gid = i->i_gid;
    + pe->attr->mode = i->i_mode;
    + }
    +
    + return error;
    +}
    +
    +static void accessfs_read_inode(struct inode *inode)
    +{
    + ino_t ino = inode->i_ino;
    + struct list_head *list;
    + spin_lock(&accessfs_lock);
    + list_for_each(list, &hash) {
    + struct accessfs_entry *pe;
    + pe = list_entry(list, struct accessfs_entry, hash);
    + if (pe->ino == ino) {
    + accessfs_init_inode(inode, pe);
    + break;
    + }
    + }
    +
    + spin_unlock(&accessfs_lock);
    +}
    +
    +static struct inode_operations accessfs_inode_operations = {
    + .setattr = accessfs_notify_change,
    +};
    +
    +static struct inode_operations accessfs_dir_inode_operations = {
    + .lookup = accessfs_lookup,
    + .setattr = accessfs_notify_change,
    +};
    +
    +static struct file_operations accessfs_dir_file_operations = {
    + .readdir = accessfs_readdir,
    +};
    +
    +static struct super_operations accessfs_ops = {
    + .read_inode = accessfs_read_inode,
    + .statfs = accessfs_statfs,
    +};
    +
    +static int accessfs_fill_super(struct super_block *sb, void *data, int silent)
    +{
    + struct inode *inode;
    + struct dentry *root;
    +
    + sb->s_blocksize = PAGE_CACHE_SIZE;
    + sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
    + sb->s_magic = ACCESSFS_MAGIC;
    + sb->s_op = &accessfs_ops;
    + inode = accessfs_get_root_inode(sb);
    + if (!inode)
    + return -ENOMEM;
    +
    + root = d_alloc_root(inode);
    + if (!root) {
    + iput(inode);
    + return -ENOMEM;
    + }
    +
    + sb->s_root = root;
    + MOD_INC_USE_COUNT;
    + return 0;
    +}
    +
    +static struct super_block *accessfs_get_sb(struct file_system_type *fs_type, int flags, char *dev_name, void *data)
    +{
    + return get_sb_single(fs_type, flags, data, accessfs_fill_super);
    +}
    +
    +static void accessfs_kill_sb(struct super_block *sb)
    +{
    + kill_anon_super(sb);
    + MOD_DEC_USE_COUNT;
    +}
    +
    +int accessfs_permitted(struct access_attr *p, int mask)
    +{
    + mode_t mode = p->mode;
    + if (current->fsuid == p->uid)
    + mode >>= 6;
    + else if (in_group_p(p->gid))
    + mode >>= 3;
    +
    + return (mode & mask) == mask;
    +}
    +
    +int accessfs_register(struct accessfs_direntry *dir, const char *name, struct access_attr *attr)
    +{
    + if (dir == 0)
    + return -EINVAL;
    +
    + return accessfs_mknod(dir, name, attr);
    +}
    +
    +void accessfs_unregister(struct accessfs_direntry *dir, const char *name)
    +{
    + struct accessfs_entry *pe;
    + spin_lock(&accessfs_lock);
    + pe = accessfs_lookup_entry(&dir->node, name, strlen(name));
    + if (pe) {
    + accessfs_unlink(pe);
    + }
    +
    + spin_unlock(&accessfs_lock);
    +}
    +
    +static struct file_system_type accessfs_fs_type = {
    + .name = "accessfs",
    + .get_sb = accessfs_get_sb,
    + .kill_sb = accessfs_kill_sb,
    +};
    +
    +static int __init init_accessfs_fs(void)
    +{
    +
    +#ifdef CONFIG_PROC_FS
    + /* create mount point for accessfs */
    + mountdir = proc_mkdir("access",&proc_root);
    +#endif
    + return register_filesystem(&accessfs_fs_type);
    +}
    +
    +static void __exit exit_accessfs_fs(void)
    +{
    + unregister_filesystem(&accessfs_fs_type);
    +
    +#ifdef CONFIG_PROC_FS
    + remove_proc_entry("access",&proc_root);
    +#endif
    +}
    +
    +module_init(init_accessfs_fs)
    +module_exit(exit_accessfs_fs)
    +
    +MODULE_AUTHOR("Olaf Dietsche");
    +MODULE_DESCRIPTION("Access Filesystem");
    +MODULE_LICENSE("GPL");
    +
    +EXPORT_SYMBOL(accessfs_permitted);
    +EXPORT_SYMBOL(accessfs_make_dirpath);
    +EXPORT_SYMBOL(accessfs_register);
    +EXPORT_SYMBOL(accessfs_unregister);
    diff -urN a/fs/accessfs/ip.c b/fs/accessfs/ip.c
    --- a/fs/accessfs/ip.c Thu Jan 1 01:00:00 1970
    +++ b/fs/accessfs/ip.c Sun Oct 13 16:56:30 2002
    @@ -0,0 +1,92 @@
    +/* Copyright (c) 2002 Olaf Dietsche
    + *
    + * User permission based port access for Linux.
    + */
    +
    +#include <linux/accessfs_fs.h>
    +#include <linux/init.h>
    +#include <linux/module.h>
    +#include <net/sock.h>
    +
    +static int max_prot_sock = CONFIG_ACCESSFS_PROT_SOCK;
    +static struct access_attr *bind_to_port;
    +
    +static int accessfs_ip_prot_sock(struct socket *sock,
    + struct sockaddr *uaddr, int addr_len)
    +{
    + struct sockaddr_in *addr = (struct sockaddr_in *) uaddr;
    + unsigned short snum = ntohs(addr->sin_port);
    + if (snum && snum < max_prot_sock
    + && !accessfs_permitted(&bind_to_port[snum], MAY_EXEC)
    + && !capable(CAP_NET_BIND_SERVICE))
    + return -EACCES;
    +
    + return 0;
    +}
    +
    +static int accessfs_ip6_prot_sock(struct socket *sock,
    + struct sockaddr *uaddr, int addr_len)
    +{
    +#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
    + struct sockaddr_in6 *addr = (struct sockaddr_in6 *) uaddr;
    + unsigned short snum = ntohs(addr->sin6_port);
    + if (snum && snum < max_prot_sock
    + && !accessfs_permitted(&bind_to_port[snum], MAY_EXEC)
    + && !capable(CAP_NET_BIND_SERVICE))
    + return -EACCES;
    +
    + return 0;
    +#else
    + return -EACCES;
    +#endif
    +}
    +
    +static struct net_hook_operations ip_net_ops = {
    + .ip_prot_sock = accessfs_ip_prot_sock,
    + .ip6_prot_sock = accessfs_ip6_prot_sock,
    +};
    +
    +static int __init init_ip(void)
    +{
    + struct accessfs_direntry *dir = accessfs_make_dirpath("net/ip/bind");
    + int i;
    + bind_to_port = kmalloc(max_prot_sock * sizeof(*bind_to_port), GFP_KERNEL);
    + if (bind_to_port == 0)
    + return -ENOMEM;
    +
    + for (i = 1; i < max_prot_sock; ++i) {
    + char buf[sizeof("65536")];
    + bind_to_port[i].uid = 0;
    + bind_to_port[i].gid = 0;
    + bind_to_port[i].mode = i < PROT_SOCK ? S_IXUSR : S_IXUGO;
    + sprintf(buf, "%d", i);
    + accessfs_register(dir, buf, &bind_to_port[i]);
    + }
    +
    + net_hooks_register(&ip_net_ops);
    + return 0;
    +}
    +
    +static void __exit exit_ip(void)
    +{
    + struct accessfs_direntry *dir = accessfs_make_dirpath("net/ip/bind");
    + int i;
    + net_hooks_unregister(&ip_net_ops);
    + for (i = 1; i < max_prot_sock; ++i) {
    + char buf[sizeof("65536")];
    + sprintf(buf, "%d", i);
    + accessfs_unregister(dir, buf);
    + }
    +
    + if (bind_to_port != 0)
    + kfree(bind_to_port);
    +}
    +
    +module_init(init_ip)
    +module_exit(exit_ip)
    +
    +MODULE_AUTHOR("Olaf Dietsche");
    +MODULE_DESCRIPTION("User based IP ports permission");
    +MODULE_LICENSE("GPL");
    +MODULE_PARM(max_prot_sock, "i");
    +MODULE_PARM_DESC(max_prot_sock, "Number of protected ports");
    diff -urN a/include/linux/accessfs_fs.h b/include/linux/accessfs_fs.h
    --- a/include/linux/accessfs_fs.h Thu Jan 1 01:00:00 1970
    +++ b/include/linux/accessfs_fs.h Sun Oct 13 17:11:15 2002
    @@ -0,0 +1,49 @@
    +/* -*- mode: c -*- */
    +#ifndef __accessfs_fs_h_included__
    +#define __accessfs_fs_h_included__ 1
    +
    +/* Copyright (c) 2001 Olaf Dietsche
    + *
    + * Access permission filesystem for Linux.
    + */
    +
    +#include <linux/config.h>
    +#include <linux/in.h>
    +#include <linux/in6.h>
    +#include <linux/fs.h>
    +#include <linux/init.h>
    +#include <net/sock.h>
    +
    +struct access_attr {
    + uid_t uid;
    + gid_t gid;
    + mode_t mode;
    +};
    +
    +struct accessfs_entry {
    + char *name;
    + struct list_head hash;
    + struct list_head siblings;
    + ino_t ino;
    + struct access_attr *attr;
    +};
    +
    +struct accessfs_direntry {
    + struct accessfs_entry node;
    + struct accessfs_direntry *parent;
    + struct list_head children;
    + struct access_attr attr;
    +};
    +
    +extern int accessfs_permitted(struct access_attr *p, int mask);
    +extern struct accessfs_direntry *accessfs_make_dirpath(const char *name);
    +extern int accessfs_register(struct accessfs_direntry *dir, const char *name, struct access_attr *attr);
    +extern void accessfs_unregister(struct accessfs_direntry *dir, const char *name);
    +
    +#if CONFIG_ACCESSFS_PROT_SOCK < PROT_SOCK
    +#define CONFIG_ACCESSFS_PROT_SOCK PROT_SOCK
    +#elseif CONFIG_ACCESSFS_PROT_SOCK > 65536
    +#define CONFIG_ACCESSFS_PROT_SOCK 65536
    +#endif
    +
    +#endif
    -
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