Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Plan 9 style capability device implementation for the Linux Kernel |
| 3 | * |
| 4 | * Copyright 2008, 2009 Ashwin Ganti <ashwin.ganti@gmail.com> |
| 5 | * |
| 6 | * Released under the GPLv2 |
| 7 | * |
| 8 | */ |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 9 | #include <linux/init.h> |
| 10 | #include <linux/kernel.h> |
Greg Kroah-Hartman | 2418a62 | 2009-02-24 20:37:55 -0800 | [diff] [blame^] | 11 | #include <linux/moduleparam.h> |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 12 | #include <linux/slab.h> |
| 13 | #include <linux/fs.h> |
| 14 | #include <linux/errno.h> |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 15 | #include <linux/fcntl.h> |
| 16 | #include <linux/cdev.h> |
Greg Kroah-Hartman | 77dc113 | 2009-02-24 20:21:55 -0800 | [diff] [blame] | 17 | #include <linux/uaccess.h> |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 18 | #include <linux/list.h> |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 19 | #include <linux/mm.h> |
| 20 | #include <linux/string.h> |
| 21 | #include <linux/crypto.h> |
| 22 | #include <linux/highmem.h> |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 23 | #include <linux/scatterlist.h> |
Greg Kroah-Hartman | 5dba082 | 2009-02-24 20:06:34 -0800 | [diff] [blame] | 24 | #include <linux/sched.h> |
| 25 | #include <linux/cred.h> |
Greg Kroah-Hartman | 4bf0438 | 2009-02-24 20:11:39 -0800 | [diff] [blame] | 26 | |
| 27 | #ifndef CAP_MAJOR |
| 28 | #define CAP_MAJOR 0 |
| 29 | #endif |
| 30 | |
| 31 | #ifndef CAP_NR_DEVS |
| 32 | #define CAP_NR_DEVS 2 /* caphash and capuse */ |
| 33 | #endif |
| 34 | |
| 35 | #ifndef CAP_NODE_SIZE |
| 36 | #define CAP_NODE_SIZE 20 |
| 37 | #endif |
| 38 | |
| 39 | #define MAX_DIGEST_SIZE 20 |
| 40 | |
| 41 | struct cap_node { |
| 42 | char data[CAP_NODE_SIZE]; |
| 43 | struct list_head list; |
| 44 | }; |
| 45 | |
| 46 | struct cap_dev { |
| 47 | struct cap_node *head; |
| 48 | int node_size; |
| 49 | unsigned long size; |
| 50 | struct semaphore sem; |
| 51 | struct cdev cdev; |
| 52 | }; |
| 53 | |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 54 | static int cap_major = CAP_MAJOR; |
| 55 | static int cap_minor; |
| 56 | static int cap_nr_devs = CAP_NR_DEVS; |
| 57 | static int cap_node_size = CAP_NODE_SIZE; |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 58 | |
| 59 | module_param(cap_major, int, S_IRUGO); |
| 60 | module_param(cap_minor, int, S_IRUGO); |
| 61 | module_param(cap_nr_devs, int, S_IRUGO); |
| 62 | |
| 63 | MODULE_AUTHOR("Ashwin Ganti"); |
| 64 | MODULE_LICENSE("GPL"); |
| 65 | |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 66 | static struct cap_dev *cap_devices; |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 67 | |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 68 | static void hexdump(unsigned char *buf, unsigned int len) |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 69 | { |
| 70 | while (len--) |
| 71 | printk("%02x", *buf++); |
| 72 | printk("\n"); |
| 73 | } |
| 74 | |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 75 | static char *cap_hash(char *plain_text, unsigned int plain_text_size, |
| 76 | char *key, unsigned int key_size) |
| 77 | { |
| 78 | struct scatterlist sg; |
Greg Kroah-Hartman | 6d0d63b | 2009-02-24 20:31:39 -0800 | [diff] [blame] | 79 | char *result; |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 80 | struct crypto_hash *tfm; |
| 81 | struct hash_desc desc; |
| 82 | int ret; |
| 83 | |
| 84 | tfm = crypto_alloc_hash("hmac(sha1)", 0, CRYPTO_ALG_ASYNC); |
| 85 | if (IS_ERR(tfm)) { |
| 86 | printk(KERN_ERR |
| 87 | "failed to load transform for hmac(sha1): %ld\n", |
| 88 | PTR_ERR(tfm)); |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 89 | return NULL; |
| 90 | } |
| 91 | |
| 92 | desc.tfm = tfm; |
| 93 | desc.flags = 0; |
| 94 | |
Greg Kroah-Hartman | 6d0d63b | 2009-02-24 20:31:39 -0800 | [diff] [blame] | 95 | result = kzalloc(MAX_DIGEST_SIZE, GFP_KERNEL); |
| 96 | if (!result) { |
| 97 | printk(KERN_ERR "out of memory!\n"); |
| 98 | goto out; |
| 99 | } |
| 100 | |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 101 | sg_set_buf(&sg, plain_text, plain_text_size); |
| 102 | |
| 103 | ret = crypto_hash_setkey(tfm, key, key_size); |
| 104 | if (ret) { |
| 105 | printk(KERN_ERR "setkey() failed ret=%d\n", ret); |
| 106 | kfree(result); |
| 107 | result = NULL; |
| 108 | goto out; |
| 109 | } |
| 110 | |
| 111 | ret = crypto_hash_digest(&desc, &sg, plain_text_size, result); |
| 112 | if (ret) { |
| 113 | printk(KERN_ERR "digest () failed ret=%d\n", ret); |
| 114 | kfree(result); |
| 115 | result = NULL; |
| 116 | goto out; |
| 117 | } |
| 118 | |
| 119 | printk(KERN_DEBUG "crypto hash digest size %d\n", |
| 120 | crypto_hash_digestsize(tfm)); |
| 121 | hexdump(result, MAX_DIGEST_SIZE); |
| 122 | |
| 123 | out: |
| 124 | crypto_free_hash(tfm); |
| 125 | return result; |
| 126 | } |
| 127 | |
| 128 | static int cap_trim(struct cap_dev *dev) |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 129 | { |
| 130 | struct cap_node *tmp; |
| 131 | struct list_head *pos, *q; |
| 132 | if (dev->head != NULL) { |
| 133 | list_for_each_safe(pos, q, &(dev->head->list)) { |
| 134 | tmp = list_entry(pos, struct cap_node, list); |
| 135 | list_del(pos); |
| 136 | kfree(tmp); |
| 137 | } |
| 138 | } |
| 139 | return 0; |
| 140 | } |
| 141 | |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 142 | static int cap_open(struct inode *inode, struct file *filp) |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 143 | { |
| 144 | struct cap_dev *dev; |
| 145 | dev = container_of(inode->i_cdev, struct cap_dev, cdev); |
| 146 | filp->private_data = dev; |
| 147 | |
| 148 | /* trim to 0 the length of the device if open was write-only */ |
| 149 | if ((filp->f_flags & O_ACCMODE) == O_WRONLY) { |
| 150 | if (down_interruptible(&dev->sem)) |
| 151 | return -ERESTARTSYS; |
| 152 | cap_trim(dev); |
| 153 | up(&dev->sem); |
| 154 | } |
| 155 | /* initialise the head if it is NULL */ |
| 156 | if (dev->head == NULL) { |
Greg Kroah-Hartman | 77dc113 | 2009-02-24 20:21:55 -0800 | [diff] [blame] | 157 | dev->head = kmalloc(sizeof(struct cap_node), GFP_KERNEL); |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 158 | INIT_LIST_HEAD(&(dev->head->list)); |
| 159 | } |
| 160 | return 0; |
| 161 | } |
| 162 | |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 163 | static int cap_release(struct inode *inode, struct file *filp) |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 164 | { |
| 165 | return 0; |
| 166 | } |
| 167 | |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 168 | static ssize_t cap_write(struct file *filp, const char __user *buf, |
| 169 | size_t count, loff_t *f_pos) |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 170 | { |
| 171 | struct cap_node *node_ptr, *tmp; |
| 172 | struct list_head *pos; |
| 173 | struct cap_dev *dev = filp->private_data; |
| 174 | ssize_t retval = -ENOMEM; |
Greg Kroah-Hartman | 5dba082 | 2009-02-24 20:06:34 -0800 | [diff] [blame] | 175 | struct cred *new; |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 176 | int len, target_int, source_int, flag = 0; |
| 177 | char *user_buf, *user_buf_running, *source_user, *target_user, |
| 178 | *rand_str, *hash_str, *result; |
| 179 | |
| 180 | if (down_interruptible(&dev->sem)) |
| 181 | return -ERESTARTSYS; |
| 182 | |
Greg Kroah-Hartman | 77dc113 | 2009-02-24 20:21:55 -0800 | [diff] [blame] | 183 | node_ptr = kmalloc(sizeof(struct cap_node), GFP_KERNEL); |
Greg Kroah-Hartman | 6d0d63b | 2009-02-24 20:31:39 -0800 | [diff] [blame] | 184 | user_buf = kzalloc(count, GFP_KERNEL); |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 185 | |
| 186 | if (copy_from_user(user_buf, buf, count)) { |
| 187 | retval = -EFAULT; |
| 188 | goto out; |
| 189 | } |
| 190 | |
Greg Kroah-Hartman | 77dc113 | 2009-02-24 20:21:55 -0800 | [diff] [blame] | 191 | /* |
| 192 | * If the minor number is 0 ( /dev/caphash ) then simply add the |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 193 | * hashed capability supplied by the user to the list of hashes |
| 194 | */ |
| 195 | if (0 == iminor(filp->f_dentry->d_inode)) { |
| 196 | printk(KERN_INFO "Capability being written to /dev/caphash : \n"); |
| 197 | hexdump(user_buf, count); |
| 198 | memcpy(node_ptr->data, user_buf, count); |
| 199 | list_add(&(node_ptr->list), &(dev->head->list)); |
| 200 | } else { |
Greg Kroah-Hartman | 77dc113 | 2009-02-24 20:21:55 -0800 | [diff] [blame] | 201 | /* |
| 202 | * break the supplied string into tokens with @ as the |
| 203 | * delimiter If the string is "user1@user2@randomstring" we |
| 204 | * need to split it and hash 'user1@user2' using 'randomstring' |
| 205 | * as the key. |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 206 | */ |
| 207 | user_buf_running = kstrdup(user_buf, GFP_KERNEL); |
| 208 | source_user = strsep(&user_buf_running, "@"); |
| 209 | target_user = strsep(&user_buf_running, "@"); |
| 210 | rand_str = strsep(&user_buf_running, "@"); |
| 211 | |
| 212 | /* hash the string user1@user2 with rand_str as the key */ |
| 213 | len = strlen(source_user) + strlen(target_user) + 1; |
Greg Kroah-Hartman | 6d0d63b | 2009-02-24 20:31:39 -0800 | [diff] [blame] | 214 | hash_str = kzalloc(len, GFP_KERNEL); |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 215 | strcat(hash_str, source_user); |
| 216 | strcat(hash_str, "@"); |
| 217 | strcat(hash_str, target_user); |
| 218 | |
| 219 | printk(KERN_ALERT "the source user is %s \n", source_user); |
| 220 | printk(KERN_ALERT "the target user is %s \n", target_user); |
| 221 | |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 222 | result = cap_hash(hash_str, len, rand_str, strlen(rand_str)); |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 223 | if (NULL == result) { |
| 224 | retval = -EFAULT; |
| 225 | goto out; |
| 226 | } |
| 227 | memcpy(node_ptr->data, result, CAP_NODE_SIZE); |
| 228 | /* Change the process's uid if the hash is present in the |
| 229 | * list of hashes |
| 230 | */ |
| 231 | list_for_each(pos, &(cap_devices->head->list)) { |
Greg Kroah-Hartman | 77dc113 | 2009-02-24 20:21:55 -0800 | [diff] [blame] | 232 | /* |
| 233 | * Change the user id of the process if the hashes |
| 234 | * match |
| 235 | */ |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 236 | if (0 == |
| 237 | memcmp(result, |
| 238 | list_entry(pos, struct cap_node, |
| 239 | list)->data, |
| 240 | CAP_NODE_SIZE)) { |
| 241 | target_int = (unsigned int) |
| 242 | simple_strtol(target_user, NULL, 0); |
| 243 | source_int = (unsigned int) |
| 244 | simple_strtol(source_user, NULL, 0); |
| 245 | flag = 1; |
| 246 | |
Greg Kroah-Hartman | 77dc113 | 2009-02-24 20:21:55 -0800 | [diff] [blame] | 247 | /* |
| 248 | * Check whether the process writing to capuse |
| 249 | * is actually owned by the source owner |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 250 | */ |
Greg Kroah-Hartman | 5dba082 | 2009-02-24 20:06:34 -0800 | [diff] [blame] | 251 | if (source_int != current_uid()) { |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 252 | printk(KERN_ALERT |
| 253 | "Process is not owned by the source user of the capability.\n"); |
| 254 | retval = -EFAULT; |
| 255 | goto out; |
| 256 | } |
Greg Kroah-Hartman | 77dc113 | 2009-02-24 20:21:55 -0800 | [diff] [blame] | 257 | /* |
| 258 | * What all id's need to be changed here? uid, |
| 259 | * euid, fsid, savedids ?? Currently I am |
| 260 | * changing the effective user id since most of |
| 261 | * the authorisation decisions are based on it |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 262 | */ |
Greg Kroah-Hartman | 5dba082 | 2009-02-24 20:06:34 -0800 | [diff] [blame] | 263 | new = prepare_creds(); |
| 264 | if (!new) { |
| 265 | retval = -ENOMEM; |
| 266 | goto out; |
| 267 | } |
| 268 | new->uid = (uid_t) target_int; |
| 269 | new->euid = (uid_t) target_int; |
| 270 | retval = commit_creds(new); |
| 271 | if (retval) |
| 272 | goto out; |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 273 | |
Greg Kroah-Hartman | 77dc113 | 2009-02-24 20:21:55 -0800 | [diff] [blame] | 274 | /* |
| 275 | * Remove the capability from the list and |
| 276 | * break |
| 277 | */ |
| 278 | tmp = list_entry(pos, struct cap_node, list); |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 279 | list_del(pos); |
| 280 | kfree(tmp); |
| 281 | break; |
| 282 | } |
| 283 | } |
| 284 | if (0 == flag) { |
Greg Kroah-Hartman | 77dc113 | 2009-02-24 20:21:55 -0800 | [diff] [blame] | 285 | /* |
| 286 | * The capability is not present in the list of the |
| 287 | * hashes stored, hence return failure |
| 288 | */ |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 289 | printk(KERN_ALERT |
| 290 | "Invalid capabiliy written to /dev/capuse \n"); |
| 291 | retval = -EFAULT; |
| 292 | goto out; |
| 293 | } |
| 294 | } |
| 295 | *f_pos += count; |
| 296 | retval = count; |
| 297 | /* update the size */ |
| 298 | if (dev->size < *f_pos) |
| 299 | dev->size = *f_pos; |
| 300 | |
Greg Kroah-Hartman | 77dc113 | 2009-02-24 20:21:55 -0800 | [diff] [blame] | 301 | out: |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 302 | up(&dev->sem); |
| 303 | return retval; |
| 304 | } |
| 305 | |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 306 | static const struct file_operations cap_fops = { |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 307 | .owner = THIS_MODULE, |
| 308 | .write = cap_write, |
| 309 | .open = cap_open, |
| 310 | .release = cap_release, |
| 311 | }; |
| 312 | |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 313 | static void cap_cleanup_module(void) |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 314 | { |
| 315 | int i; |
| 316 | dev_t devno = MKDEV(cap_major, cap_minor); |
| 317 | if (cap_devices) { |
| 318 | for (i = 0; i < cap_nr_devs; i++) { |
| 319 | cap_trim(cap_devices + i); |
| 320 | cdev_del(&cap_devices[i].cdev); |
| 321 | } |
| 322 | kfree(cap_devices); |
| 323 | } |
| 324 | unregister_chrdev_region(devno, cap_nr_devs); |
| 325 | |
| 326 | } |
| 327 | |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 328 | static void cap_setup_cdev(struct cap_dev *dev, int index) |
| 329 | { |
| 330 | int err, devno = MKDEV(cap_major, cap_minor + index); |
| 331 | cdev_init(&dev->cdev, &cap_fops); |
| 332 | dev->cdev.owner = THIS_MODULE; |
| 333 | dev->cdev.ops = &cap_fops; |
| 334 | err = cdev_add(&dev->cdev, devno, 1); |
| 335 | if (err) |
| 336 | printk(KERN_NOTICE "Error %d adding cap%d", err, index); |
| 337 | } |
| 338 | |
Greg Kroah-Hartman | 0f386e2 | 2009-02-24 20:25:02 -0800 | [diff] [blame] | 339 | static int cap_init_module(void) |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 340 | { |
| 341 | int result, i; |
| 342 | dev_t dev = 0; |
| 343 | |
| 344 | if (cap_major) { |
| 345 | dev = MKDEV(cap_major, cap_minor); |
| 346 | result = register_chrdev_region(dev, cap_nr_devs, "cap"); |
| 347 | } else { |
| 348 | result = alloc_chrdev_region(&dev, cap_minor, cap_nr_devs, |
| 349 | "cap"); |
| 350 | cap_major = MAJOR(dev); |
| 351 | } |
| 352 | |
| 353 | if (result < 0) { |
| 354 | printk(KERN_WARNING "cap: can't get major %d\n", |
| 355 | cap_major); |
| 356 | return result; |
| 357 | } |
| 358 | |
Greg Kroah-Hartman | 6d0d63b | 2009-02-24 20:31:39 -0800 | [diff] [blame] | 359 | cap_devices = kzalloc(cap_nr_devs * sizeof(struct cap_dev), |
| 360 | GFP_KERNEL); |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 361 | if (!cap_devices) { |
| 362 | result = -ENOMEM; |
| 363 | goto fail; |
| 364 | } |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 365 | |
| 366 | /* Initialize each device. */ |
| 367 | for (i = 0; i < cap_nr_devs; i++) { |
| 368 | cap_devices[i].node_size = cap_node_size; |
| 369 | init_MUTEX(&cap_devices[i].sem); |
| 370 | cap_setup_cdev(&cap_devices[i], i); |
| 371 | } |
| 372 | |
| 373 | return 0; |
| 374 | |
Greg Kroah-Hartman | 77dc113 | 2009-02-24 20:21:55 -0800 | [diff] [blame] | 375 | fail: |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 376 | cap_cleanup_module(); |
| 377 | return result; |
| 378 | } |
| 379 | |
| 380 | module_init(cap_init_module); |
| 381 | module_exit(cap_cleanup_module); |
| 382 | |
Ashwin Ganti | 5564317 | 2009-02-24 19:48:44 -0800 | [diff] [blame] | 383 | |