security/tomoyo/realpath.c

   1 /*
   2  * security/tomoyo/realpath.c
   3  *
   4  * Get the canonicalized absolute pathnames. The basis for TOMOYO.
   5  *
   6  * Copyright (C) 2005-2009  NTT DATA CORPORATION
   7  *
   8  * Version: 2.2.0   2009/04/01
   9  *
  10  */
  11
  12 #include <linux/types.h>
  13 #include <linux/mount.h>
  14 #include <linux/mnt_namespace.h>
  15 #include <linux/fs_struct.h>
  16 #include <linux/hash.h>
  17 #include <linux/magic.h>
  18 #include <linux/slab.h>
  19 #include "common.h"
  20
  21 /**
  22  * tomoyo_encode: Convert binary string to ascii string.
  23  *
  24  * @buffer:  Buffer for ASCII string.
  25  * @buflen:  Size of @buffer.
  26  * @str:     Binary string.
  27  *
  28  * Returns 0 on success, -ENOMEM otherwise.
  29  */
  30 int tomoyo_encode(char *buffer, int buflen, const char *str)
  31 {
  32         while (1) {
  33                 const unsigned char c = *(unsigned char *) str++;
  34
  35                 if (tomoyo_is_valid(c)) {
  36                         if (--buflen <= 0)
  37                                 break;
  38                         *buffer++ = (char) c;
  39                         if (c != '\\')
  40                                 continue;
  41                         if (--buflen <= 0)
  42                                 break;
  43                         *buffer++ = (char) c;
  44                         continue;
  45                 }
  46                 if (!c) {
  47                         if (--buflen <= 0)
  48                                 break;
  49                         *buffer = '\0';
  50                         return 0;
  51                 }
  52                 buflen -= 4;
  53                 if (buflen <= 0)
  54                         break;
  55                 *buffer++ = '\\';
  56                 *buffer++ = (c >> 6) + '0';
  57                 *buffer++ = ((c >> 3) & 7) + '0';
  58                 *buffer++ = (c & 7) + '0';
  59         }
  60         return -ENOMEM;
  61 }
  62
  63 /**
  64  * tomoyo_realpath_from_path2 - Returns realpath(3) of the given dentry but ignores chroot'ed root.
  65  *
  66  * @path:        Pointer to "struct path".
  67  * @newname:     Pointer to buffer to return value in.
  68  * @newname_len: Size of @newname.
  69  *
  70  * Returns 0 on success, negative value otherwise.
  71  *
  72  * If dentry is a directory, trailing '/' is appended.
  73  * Characters out of 0x20 < c < 0x7F range are converted to
  74  * \ooo style octal string.
  75  * Character \ is converted to \\ string.
  76  */
  77 int tomoyo_realpath_from_path2(struct path *path, char *newname,
  78                                int newname_len)
  79 {
  80         int error = -ENOMEM;
  81         struct dentry *dentry = path->dentry;
  82         char *sp;
  83
  84         if (!dentry || !path->mnt || !newname || newname_len <= 2048)
  85                 return -EINVAL;
  86         if (dentry->d_op && dentry->d_op->d_dname) {
  87                 /* For "socket:[\$]" and "pipe:[\$]". */
  88                 static const int offset = 1536;
  89                 sp = dentry->d_op->d_dname(dentry, newname + offset,
  90                                            newname_len - offset);
  91         } else {
  92                 struct path ns_root = {.mnt = NULL, .dentry = NULL};
  93
  94                 spin_lock(&dcache_lock);
  95                 /* go to whatever namespace root we are under */
  96                 sp = __d_path(path, &ns_root, newname, newname_len);
  97                 spin_unlock(&dcache_lock);
  98                 /* Prepend "/proc" prefix if using internal proc vfs mount. */
  99                 if (!IS_ERR(sp) && (path->mnt->mnt_flags & MNT_INTERNAL) &&
 100                     (path->mnt->mnt_sb->s_magic == PROC_SUPER_MAGIC)) {
 101                         sp -= 5;
 102                         if (sp >= newname)
 103                                 memcpy(sp, "/proc", 5);
 104                         else
 105                                 sp = ERR_PTR(-ENOMEM);
 106                 }
 107         }
 108         if (IS_ERR(sp))
 109                 error = PTR_ERR(sp);
 110         else
 111                 error = tomoyo_encode(newname, sp - newname, sp);
 112         /* Append trailing '/' if dentry is a directory. */
 113         if (!error && dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)
 114             && *newname) {
 115                 sp = newname + strlen(newname);
 116                 if (*(sp - 1) != '/') {
 117                         if (sp < newname + newname_len - 4) {
 118                                 *sp++ = '/';
 119                                 *sp = '\0';
 120                         } else {
 121                                 error = -ENOMEM;
 122                         }
 123                 }
 124         }
 125         if (error)
 126                 printk(KERN_WARNING "tomoyo_realpath: Pathname too long.\n");
 127         return error;
 128 }
 129
 130 /**
 131  * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
 132  *
 133  * @path: Pointer to "struct path".
 134  *
 135  * Returns the realpath of the given @path on success, NULL otherwise.
 136  *
 137  * These functions use kzalloc(), so the caller must call kfree()
 138  * if these functions didn't return NULL.
 139  */
 140 char *tomoyo_realpath_from_path(struct path *path)
 141 {
 142         char *buf = kzalloc(sizeof(struct tomoyo_page_buffer), GFP_KERNEL);
 143
 144         BUILD_BUG_ON(sizeof(struct tomoyo_page_buffer)
 145                      <= TOMOYO_MAX_PATHNAME_LEN - 1);
 146         if (!buf)
 147                 return NULL;
 148         if (tomoyo_realpath_from_path2(path, buf,
 149                                        TOMOYO_MAX_PATHNAME_LEN - 1) == 0)
 150                 return buf;
 151         kfree(buf);
 152         return NULL;
 153 }
 154
 155 /**
 156  * tomoyo_realpath - Get realpath of a pathname.
 157  *
 158  * @pathname: The pathname to solve.
 159  *
 160  * Returns the realpath of @pathname on success, NULL otherwise.
 161  */
 162 char *tomoyo_realpath(const char *pathname)
 163 {
 164         struct path path;
 165
 166         if (pathname && kern_path(pathname, LOOKUP_FOLLOW, &path) == 0) {
 167                 char *buf = tomoyo_realpath_from_path(&path);
 168                 path_put(&path);
 169                 return buf;
 170         }
 171         return NULL;
 172 }
 173
 174 /**
 175  * tomoyo_realpath_nofollow - Get realpath of a pathname.
 176  *
 177  * @pathname: The pathname to solve.
 178  *
 179  * Returns the realpath of @pathname on success, NULL otherwise.
 180  */
 181 char *tomoyo_realpath_nofollow(const char *pathname)
 182 {
 183         struct path path;
 184
 185         if (pathname && kern_path(pathname, 0, &path) == 0) {
 186                 char *buf = tomoyo_realpath_from_path(&path);
 187                 path_put(&path);
 188                 return buf;
 189         }
 190         return NULL;
 191 }
 192
 193 /* Memory allocated for non-string data. */
 194 static atomic_t tomoyo_policy_memory_size;
 195 /* Quota for holding policy. */
 196 static unsigned int tomoyo_quota_for_policy;
 197
 198 /**
 199  * tomoyo_memory_ok - Check memory quota.
 200  *
 201  * @ptr: Pointer to allocated memory.
 202  *
 203  * Returns true on success, false otherwise.
 204  *
 205  * Caller holds tomoyo_policy_lock.
 206  * Memory pointed by @ptr will be zeroed on success.
 207  */
 208 bool tomoyo_memory_ok(void *ptr)
 209 {
 210         int allocated_len = ptr ? ksize(ptr) : 0;
 211         atomic_add(allocated_len, &tomoyo_policy_memory_size);
 212         if (ptr && (!tomoyo_quota_for_policy ||
 213                     atomic_read(&tomoyo_policy_memory_size)
 214                     <= tomoyo_quota_for_policy)) {
 215                 memset(ptr, 0, allocated_len);
 216                 return true;
 217         }
 218         printk(KERN_WARNING "ERROR: Out of memory "
 219                "for tomoyo_alloc_element().\n");
 220         if (!tomoyo_policy_loaded)
 221                 panic("MAC Initialization failed.\n");
 222         return false;
 223 }
 224
 225 /**
 226  * tomoyo_memory_free - Free memory for elements.
 227  *
 228  * @ptr:  Pointer to allocated memory.
 229  */
 230 void tomoyo_memory_free(void *ptr)
 231 {
 232         atomic_sub(ksize(ptr), &tomoyo_policy_memory_size);
 233         kfree(ptr);
 234 }
 235
 236 /*
 237  * tomoyo_name_list is used for holding string data used by TOMOYO.
 238  * Since same string data is likely used for multiple times (e.g.
 239  * "/lib/libc-2.5.so"), TOMOYO shares string data in the form of
 240  * "const struct tomoyo_path_info *".
 241  */
 242 struct list_head tomoyo_name_list[TOMOYO_MAX_HASH];
 243 /* Lock for protecting tomoyo_name_list . */
 244 DEFINE_MUTEX(tomoyo_name_list_lock);
 245
 246 /**
 247  * tomoyo_get_name - Allocate permanent memory for string data.
 248  *
 249  * @name: The string to store into the permernent memory.
 250  *
 251  * Returns pointer to "struct tomoyo_path_info" on success, NULL otherwise.
 252  */
 253 const struct tomoyo_path_info *tomoyo_get_name(const char *name)
 254 {
 255         struct tomoyo_name_entry *ptr;
 256         unsigned int hash;
 257         int len;
 258         int allocated_len;
 259         struct list_head *head;
 260
 261         if (!name)
 262                 return NULL;
 263         len = strlen(name) + 1;
 264         hash = full_name_hash((const unsigned char *) name, len - 1);
 265         head = &tomoyo_name_list[hash_long(hash, TOMOYO_HASH_BITS)];
 266         mutex_lock(&tomoyo_name_list_lock);
 267         list_for_each_entry(ptr, head, list) {
 268                 if (hash != ptr->entry.hash || strcmp(name, ptr->entry.name))
 269                         continue;
 270                 atomic_inc(&ptr->users);
 271                 goto out;
 272         }
 273         ptr = kzalloc(sizeof(*ptr) + len, GFP_KERNEL);
 274         allocated_len = ptr ? ksize(ptr) : 0;
 275         if (!ptr || (tomoyo_quota_for_policy &&
 276                      atomic_read(&tomoyo_policy_memory_size) + allocated_len
 277                      > tomoyo_quota_for_policy)) {
 278                 kfree(ptr);
 279                 printk(KERN_WARNING "ERROR: Out of memory "
 280                        "for tomoyo_get_name().\n");
 281                 if (!tomoyo_policy_loaded)
 282                         panic("MAC Initialization failed.\n");
 283                 ptr = NULL;
 284                 goto out;
 285         }
 286         atomic_add(allocated_len, &tomoyo_policy_memory_size);
 287         ptr->entry.name = ((char *) ptr) + sizeof(*ptr);
 288         memmove((char *) ptr->entry.name, name, len);
 289         atomic_set(&ptr->users, 1);
 290         tomoyo_fill_path_info(&ptr->entry);
 291         list_add_tail(&ptr->list, head);
 292  out:
 293         mutex_unlock(&tomoyo_name_list_lock);
 294         return ptr ? &ptr->entry : NULL;
 295 }
 296
 297 /**
 298  * tomoyo_realpath_init - Initialize realpath related code.
 299  */
 300 void __init tomoyo_realpath_init(void)
 301 {
 302         int i;
 303
 304         BUILD_BUG_ON(TOMOYO_MAX_PATHNAME_LEN > PATH_MAX);
 305         for (i = 0; i < TOMOYO_MAX_HASH; i++)
 306                 INIT_LIST_HEAD(&tomoyo_name_list[i]);
 307         INIT_LIST_HEAD(&tomoyo_kernel_domain.acl_info_list);
 308         tomoyo_kernel_domain.domainname = tomoyo_get_name(TOMOYO_ROOT_NAME);
 309         /*
 310          * tomoyo_read_lock() is not needed because this function is
 311          * called before the first "delete" request.
 312          */
 313         list_add_tail_rcu(&tomoyo_kernel_domain.list, &tomoyo_domain_list);
 314         if (tomoyo_find_domain(TOMOYO_ROOT_NAME) != &tomoyo_kernel_domain)
 315                 panic("Can't register tomoyo_kernel_domain");
 316 }
 317
 318 /**
 319  * tomoyo_read_memory_counter - Check for memory usage in bytes.
 320  *
 321  * @head: Pointer to "struct tomoyo_io_buffer".
 322  *
 323  * Returns memory usage.
 324  */
 325 int tomoyo_read_memory_counter(struct tomoyo_io_buffer *head)
 326 {
 327         if (!head->read_eof) {
 328                 const unsigned int policy
 329                         = atomic_read(&tomoyo_policy_memory_size);
 330                 char buffer[64];
 331
 332                 memset(buffer, 0, sizeof(buffer));
 333                 if (tomoyo_quota_for_policy)
 334                         snprintf(buffer, sizeof(buffer) - 1,
 335                                  "   (Quota: %10u)",
 336                                  tomoyo_quota_for_policy);
 337                 else
 338                         buffer[0] = '\0';
 339                 tomoyo_io_printf(head, "Policy:  %10u%s\n", policy, buffer);
 340                 tomoyo_io_printf(head, "Total:   %10u\n", policy);
 341                 head->read_eof = true;
 342         }
 343         return 0;
 344 }
 345
 346 /**
 347  * tomoyo_write_memory_quota - Set memory quota.
 348  *
 349  * @head: Pointer to "struct tomoyo_io_buffer".
 350  *
 351  * Returns 0.
 352  */
 353 int tomoyo_write_memory_quota(struct tomoyo_io_buffer *head)
 354 {
 355         char *data = head->write_buf;
 356         unsigned int size;
 357
 358         if (sscanf(data, "Policy: %u", &size) == 1)
 359                 tomoyo_quota_for_policy = size;
 360         return 0;
 361 }