Staging: add p9auth driver

This is a driver that adds Plan 9 style capability device
implementation.

From: Ashwin Ganti <ashwin.ganti@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/p9auth/p9auth.c

+/*
+ * 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/module.h>
+#include <linux/moduleparam.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <linux/proc_fs.h>
+#include <linux/fcntl.h>
+#include <linux/cdev.h>
+#include <linux/syscalls.h>
+#include <asm/system.h>
+#include <asm/uaccess.h>
+#include <linux/list.h>
+#include <linux/err.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/crypto.h>
+#include <linux/highmem.h>
+#include <linux/jiffies.h>
+#include <linux/timex.h>
+#include <linux/interrupt.h>
+#include <linux/scatterlist.h>
+#include <linux/crypto.h>
+#include "p9auth.h"
+
+int cap_major = CAP_MAJOR;
+int cap_minor = 0;
+int cap_nr_devs = CAP_NR_DEVS;
+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");
+
+struct cap_dev *cap_devices;
+
+void hexdump(unsigned char *buf, unsigned int len)
+{
+	while (len--)
+		printk("%02x", *buf++);
+	printk("\n");
+}
+
+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;
+}
+
+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 =
+		    (struct cap_node *) kmalloc(sizeof(struct cap_node),
+						GFP_KERNEL);
+		INIT_LIST_HEAD(&(dev->head->list));
+	}
+	return 0;
+}
+
+int cap_release(struct inode *inode, struct file *filp)
+{
+	return 0;
+}
+
+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;
+	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;
+
+	node_ptr =
+	    (struct cap_node *) kmalloc(sizeof(struct cap_node),
+					GFP_KERNEL);
+	user_buf = (char *) kmalloc(count, GFP_KERNEL);
+	memset(user_buf, 0, count);
+
+	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)) {
+		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));
+	} else {
+		/* 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
+		 */
+		user_buf_running = kstrdup(user_buf, GFP_KERNEL);
+		source_user = strsep(&user_buf_running, "@");
+		target_user = strsep(&user_buf_running, "@");
+		rand_str = strsep(&user_buf_running, "@");
+
+		/* hash the string user1@user2 with rand_str as the key */
+		len = strlen(source_user) + strlen(target_user) + 1;
+		hash_str = (char *) kmalloc(len, GFP_KERNEL);
+		memset(hash_str, 0, len);
+		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);
+		/* 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
+				 */
+				current->uid = (uid_t) target_int;
+				current->euid = (uid_t) target_int;
+
+				/* 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:
+	up(&dev->sem);
+	return retval;
+}
+
+struct file_operations cap_fops = {
+	.owner = THIS_MODULE,
+	.write = cap_write,
+	.open = cap_open,
+	.release = cap_release,
+};
+
+
+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);
+}
+
+
+int 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 =
+	    kmalloc(cap_nr_devs * sizeof(struct cap_dev), GFP_KERNEL);
+	if (!cap_devices) {
+		result = -ENOMEM;
+		goto fail;
+	}
+	memset(cap_devices, 0, cap_nr_devs * sizeof(struct cap_dev));
+
+	/* 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);
+
+char *cap_hash(char *plain_text, unsigned int plain_text_size,
+	       char *key, unsigned int key_size)
+{
+	struct scatterlist sg;
+	char *result = (char *) kmalloc(MAX_DIGEST_SIZE, GFP_KERNEL);
+	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("failed to load transform for hmac(sha1): %ld\n",
+		       PTR_ERR(tfm));
+		kfree(result);
+		return NULL;
+	}
+
+	desc.tfm = tfm;
+	desc.flags = 0;
+
+	memset(result, 0, MAX_DIGEST_SIZE);
+	sg_set_buf(&sg, plain_text, plain_text_size);
+
+	ret = crypto_hash_setkey(tfm, key, key_size);
+	if (ret) {
+		printk("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("digest () failed ret=%d\n", ret);
+		kfree(result);
+		result = NULL;
+		goto out;
+	}
+
+	printk("crypto hash digest size %d\n",
+	       crypto_hash_digestsize(tfm));
+	hexdump(result, MAX_DIGEST_SIZE);
+
+      out:
+	crypto_free_hash(tfm);
+	return result;
+}

drivers/staging/p9auth/p9auth.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;
+};
+
+extern int cap_major;
+extern int cap_nr_devs;
+extern int cap_node_size;
+
+int cap_trim(struct cap_dev *);
+ssize_t cap_write(struct file *, const char __user *, size_t, loff_t *);
+char *cap_hash(char *plain_text, unsigned int plain_text_size, char *key, unsigned int key_size);
+void hex_dump(unsigned char * buf, unsigned int len);