+++ /dev/null
-/*
- * Plan 9 style capability device implementation for the Linux Kernel
- *
- * Copyright 2008, 2009 Ashwin Ganti <ashwin.ganti@gmail.com>
- *
- * Released under the GPLv2
- *
- */
-#include <linux/init.h>
-#include <linux/kernel.h>
-#include <linux/moduleparam.h>
-#include <linux/slab.h>
-#include <linux/fs.h>
-#include <linux/errno.h>
-#include <linux/fcntl.h>
-#include <linux/cdev.h>
-#include <linux/uaccess.h>
-#include <linux/list.h>
-#include <linux/mm.h>
-#include <linux/string.h>
-#include <linux/crypto.h>
-#include <linux/highmem.h>
-#include <linux/scatterlist.h>
-#include <linux/sched.h>
-#include <linux/cred.h>
-
-#ifndef CAP_MAJOR
-#define CAP_MAJOR 0
-#endif
-
-#ifndef CAP_NR_DEVS
-#define CAP_NR_DEVS 2 /* caphash and capuse */
-#endif
-
-#ifndef CAP_NODE_SIZE
-#define CAP_NODE_SIZE 20
-#endif
-
-#define MAX_DIGEST_SIZE 20
-
-struct cap_node {
- char data[CAP_NODE_SIZE];
- struct list_head list;
-};
-
-struct cap_dev {
- struct cap_node *head;
- int node_size;
- unsigned long size;
- struct semaphore sem;
- struct cdev cdev;
-};
-
-static int cap_major = CAP_MAJOR;
-static int cap_minor;
-static int cap_nr_devs = CAP_NR_DEVS;
-static int cap_node_size = CAP_NODE_SIZE;
-
-module_param(cap_major, int, S_IRUGO);
-module_param(cap_minor, int, S_IRUGO);
-module_param(cap_nr_devs, int, S_IRUGO);
-
-MODULE_AUTHOR("Ashwin Ganti");
-MODULE_LICENSE("GPL");
-
-static struct cap_dev *cap_devices;
-
-static void hexdump(unsigned char *buf, unsigned int len)
-{
- while (len--)
- printk("%02x", *buf++);
- printk("\n");
-}
-
-static char *cap_hash(char *plain_text, unsigned int plain_text_size,
- char *key, unsigned int key_size)
-{
- struct scatterlist sg;
- char *result;
- struct crypto_hash *tfm;
- struct hash_desc desc;
- int ret;
-
- tfm = crypto_alloc_hash("hmac(sha1)", 0, CRYPTO_ALG_ASYNC);
- if (IS_ERR(tfm)) {
- printk(KERN_ERR
- "failed to load transform for hmac(sha1): %ld\n",
- PTR_ERR(tfm));
- return NULL;
- }
-
- desc.tfm = tfm;
- desc.flags = 0;
-
- result = kzalloc(MAX_DIGEST_SIZE, GFP_KERNEL);
- if (!result) {
- printk(KERN_ERR "out of memory!\n");
- goto out;
- }
-
- sg_set_buf(&sg, plain_text, plain_text_size);
-
- ret = crypto_hash_setkey(tfm, key, key_size);
- if (ret) {
- printk(KERN_ERR "setkey() failed ret=%d\n", ret);
- kfree(result);
- result = NULL;
- goto out;
- }
-
- ret = crypto_hash_digest(&desc, &sg, plain_text_size, result);
- if (ret) {
- printk(KERN_ERR "digest () failed ret=%d\n", ret);
- kfree(result);
- result = NULL;
- goto out;
- }
-
- printk(KERN_DEBUG "crypto hash digest size %d\n",
- crypto_hash_digestsize(tfm));
- hexdump(result, MAX_DIGEST_SIZE);
-
-out:
- crypto_free_hash(tfm);
- return result;
-}
-
-static int cap_trim(struct cap_dev *dev)
-{
- struct cap_node *tmp;
- struct list_head *pos, *q;
- if (dev->head != NULL) {
- list_for_each_safe(pos, q, &(dev->head->list)) {
- tmp = list_entry(pos, struct cap_node, list);
- list_del(pos);
- kfree(tmp);
- }
- }
- return 0;
-}
-
-static int cap_open(struct inode *inode, struct file *filp)
-{
- struct cap_dev *dev;
- dev = container_of(inode->i_cdev, struct cap_dev, cdev);
- filp->private_data = dev;
-
- /* trim to 0 the length of the device if open was write-only */
- if ((filp->f_flags & O_ACCMODE) == O_WRONLY) {
- if (down_interruptible(&dev->sem))
- return -ERESTARTSYS;
- cap_trim(dev);
- up(&dev->sem);
- }
- /* initialise the head if it is NULL */
- if (dev->head == NULL) {
- dev->head = kmalloc(sizeof(struct cap_node), GFP_KERNEL);
- INIT_LIST_HEAD(&(dev->head->list));
- }
- return 0;
-}
-
-static int cap_release(struct inode *inode, struct file *filp)
-{
- return 0;
-}
-
-static ssize_t cap_write(struct file *filp, const char __user *buf,
- size_t count, loff_t *f_pos)
-{
- struct cap_node *node_ptr, *tmp;
- struct list_head *pos;
- struct cap_dev *dev = filp->private_data;
- ssize_t retval = -ENOMEM;
- struct cred *new;
- int len, target_int, source_int, flag = 0;
- char *user_buf, *user_buf_running, *source_user, *target_user,
- *rand_str, *hash_str, *result;
-
- if (down_interruptible(&dev->sem))
- return -ERESTARTSYS;
-
- user_buf_running = NULL;
- hash_str = NULL;
- node_ptr = kmalloc(sizeof(struct cap_node), GFP_KERNEL);
- user_buf = kzalloc(count+1, GFP_KERNEL);
- if (!node_ptr || !user_buf)
- goto out;
-
- if (copy_from_user(user_buf, buf, count)) {
- retval = -EFAULT;
- goto out;
- }
-
- /*
- * If the minor number is 0 ( /dev/caphash ) then simply add the
- * hashed capability supplied by the user to the list of hashes
- */
- if (0 == iminor(filp->f_dentry->d_inode)) {
- if (count > CAP_NODE_SIZE) {
- retval = -EINVAL;
- goto out;
- }
- printk(KERN_INFO "Capability being written to /dev/caphash : \n");
- hexdump(user_buf, count);
- memcpy(node_ptr->data, user_buf, count);
- list_add(&(node_ptr->list), &(dev->head->list));
- node_ptr = NULL;
- } else {
- char *tmpu;
- if (!cap_devices[0].head ||
- list_empty(&(cap_devices[0].head->list))) {
- retval = -EINVAL;
- goto out;
- }
- /*
- * break the supplied string into tokens with @ as the
- * delimiter If the string is "user1@user2@randomstring" we
- * need to split it and hash 'user1@user2' using 'randomstring'
- * as the key.
- */
- tmpu = user_buf_running = kstrdup(user_buf, GFP_KERNEL);
- source_user = strsep(&tmpu, "@");
- target_user = strsep(&tmpu, "@");
- rand_str = tmpu;
- if (!source_user || !target_user || !rand_str) {
- retval = -EINVAL;
- goto out;
- }
-
- /* hash the string user1@user2 with rand_str as the key */
- len = strlen(source_user) + strlen(target_user) + 1;
- /* src, @, len, \0 */
- hash_str = kzalloc(len+1, GFP_KERNEL);
- strcat(hash_str, source_user);
- strcat(hash_str, "@");
- strcat(hash_str, target_user);
-
- printk(KERN_ALERT "the source user is %s \n", source_user);
- printk(KERN_ALERT "the target user is %s \n", target_user);
-
- result = cap_hash(hash_str, len, rand_str, strlen(rand_str));
- if (NULL == result) {
- retval = -EFAULT;
- goto out;
- }
- memcpy(node_ptr->data, result, CAP_NODE_SIZE); /* why? */
- /* Change the process's uid if the hash is present in the
- * list of hashes
- */
- list_for_each(pos, &(cap_devices->head->list)) {
- /*
- * Change the user id of the process if the hashes
- * match
- */
- if (0 ==
- memcmp(result,
- list_entry(pos, struct cap_node,
- list)->data,
- CAP_NODE_SIZE)) {
- target_int = (unsigned int)
- simple_strtol(target_user, NULL, 0);
- source_int = (unsigned int)
- simple_strtol(source_user, NULL, 0);
- flag = 1;
-
- /*
- * Check whether the process writing to capuse
- * is actually owned by the source owner
- */
- if (source_int != current_uid()) {
- printk(KERN_ALERT
- "Process is not owned by the source user of the capability.\n");
- retval = -EFAULT;
- goto out;
- }
- /*
- * What all id's need to be changed here? uid,
- * euid, fsid, savedids ?? Currently I am
- * changing the effective user id since most of
- * the authorisation decisions are based on it
- */
- new = prepare_creds();
- if (!new) {
- retval = -ENOMEM;
- goto out;
- }
- new->uid = (uid_t) target_int;
- new->euid = (uid_t) target_int;
- retval = commit_creds(new);
- if (retval)
- goto out;
-
- /*
- * Remove the capability from the list and
- * break
- */
- tmp = list_entry(pos, struct cap_node, list);
- list_del(pos);
- kfree(tmp);
- break;
- }
- }
- if (0 == flag) {
- /*
- * The capability is not present in the list of the
- * hashes stored, hence return failure
- */
- printk(KERN_ALERT
- "Invalid capabiliy written to /dev/capuse \n");
- retval = -EFAULT;
- goto out;
- }
- }
- *f_pos += count;
- retval = count;
- /* update the size */
- if (dev->size < *f_pos)
- dev->size = *f_pos;
-
-out:
- kfree(node_ptr);
- kfree(user_buf);
- kfree(user_buf_running);
- kfree(hash_str);
- up(&dev->sem);
- return retval;
-}
-
-static const struct file_operations cap_fops = {
- .owner = THIS_MODULE,
- .write = cap_write,
- .open = cap_open,
- .release = cap_release,
-};
-
-/* no __exit here because it can be called by the init function */
-static void cap_cleanup_module(void)
-{
- int i;
- dev_t devno = MKDEV(cap_major, cap_minor);
- if (cap_devices) {
- for (i = 0; i < cap_nr_devs; i++) {
- cap_trim(cap_devices + i);
- cdev_del(&cap_devices[i].cdev);
- }
- kfree(cap_devices);
- }
- unregister_chrdev_region(devno, cap_nr_devs);
-
-}
-
-static void cap_setup_cdev(struct cap_dev *dev, int index)
-{
- int err, devno = MKDEV(cap_major, cap_minor + index);
- cdev_init(&dev->cdev, &cap_fops);
- dev->cdev.owner = THIS_MODULE;
- dev->cdev.ops = &cap_fops;
- err = cdev_add(&dev->cdev, devno, 1);
- if (err)
- printk(KERN_NOTICE "Error %d adding cap%d", err, index);
-}
-
-static int __init cap_init_module(void)
-{
- int result, i;
- dev_t dev = 0;
-
- if (cap_major) {
- dev = MKDEV(cap_major, cap_minor);
- result = register_chrdev_region(dev, cap_nr_devs, "cap");
- } else {
- result = alloc_chrdev_region(&dev, cap_minor, cap_nr_devs,
- "cap");
- cap_major = MAJOR(dev);
- }
-
- if (result < 0) {
- printk(KERN_WARNING "cap: can't get major %d\n",
- cap_major);
- return result;
- }
-
- cap_devices = kzalloc(cap_nr_devs * sizeof(struct cap_dev),
- GFP_KERNEL);
- if (!cap_devices) {
- result = -ENOMEM;
- goto fail;
- }
-
- /* Initialize each device. */
- for (i = 0; i < cap_nr_devs; i++) {
- cap_devices[i].node_size = cap_node_size;
- init_MUTEX(&cap_devices[i].sem);
- cap_setup_cdev(&cap_devices[i], i);
- }
-
- return 0;
-
-fail:
- cap_cleanup_module();
- return result;
-}
-
-module_init(cap_init_module);
-module_exit(cap_cleanup_module);
-
-
projects / linux-2.6-block.git / commitdiff