fs/f2fs/crypto_fname.c

   1 /*
   2  * linux/fs/f2fs/crypto_fname.c
   3  *
   4  * Copied from linux/fs/ext4/crypto.c
   5  *
   6  * Copyright (C) 2015, Google, Inc.
   7  * Copyright (C) 2015, Motorola Mobility
   8  *
   9  * This contains functions for filename crypto management in f2fs
  10  *
  11  * Written by Uday Savagaonkar, 2014.
  12  *
  13  * Adjust f2fs dentry structure
  14  *      Jaegeuk Kim, 2015.
  15  *
  16  * This has not yet undergone a rigorous security audit.
  17  */
  18 #include <crypto/hash.h>
  19 #include <crypto/sha.h>
  20 #include <keys/encrypted-type.h>
  21 #include <keys/user-type.h>
  22 #include <linux/crypto.h>
  23 #include <linux/gfp.h>
  24 #include <linux/kernel.h>
  25 #include <linux/key.h>
  26 #include <linux/list.h>
  27 #include <linux/mempool.h>
  28 #include <linux/random.h>
  29 #include <linux/scatterlist.h>
  30 #include <linux/spinlock_types.h>
  31 #include <linux/f2fs_fs.h>
  32 #include <linux/ratelimit.h>
  33
  34 #include "f2fs.h"
  35 #include "f2fs_crypto.h"
  36 #include "xattr.h"
  37
  38 /**
  39  * f2fs_dir_crypt_complete() -
  40  */
  41 static void f2fs_dir_crypt_complete(struct crypto_async_request *req, int res)
  42 {
  43         struct f2fs_completion_result *ecr = req->data;
  44
  45         if (res == -EINPROGRESS)
  46                 return;
  47         ecr->res = res;
  48         complete(&ecr->completion);
  49 }
  50
  51 bool f2fs_valid_filenames_enc_mode(uint32_t mode)
  52 {
  53         return (mode == F2FS_ENCRYPTION_MODE_AES_256_CTS);
  54 }
  55
  56 static unsigned max_name_len(struct inode *inode)
  57 {
  58         return S_ISLNK(inode->i_mode) ? inode->i_sb->s_blocksize :
  59                                         F2FS_NAME_LEN;
  60 }
  61
  62 /**
  63  * f2fs_fname_encrypt() -
  64  *
  65  * This function encrypts the input filename, and returns the length of the
  66  * ciphertext. Errors are returned as negative numbers.  We trust the caller to
  67  * allocate sufficient memory to oname string.
  68  */
  69 static int f2fs_fname_encrypt(struct inode *inode,
  70                         const struct qstr *iname, struct f2fs_str *oname)
  71 {
  72         u32 ciphertext_len;
  73         struct ablkcipher_request *req = NULL;
  74         DECLARE_F2FS_COMPLETION_RESULT(ecr);
  75         struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
  76         struct crypto_ablkcipher *tfm = ci->ci_ctfm;
  77         int res = 0;
  78         char iv[F2FS_CRYPTO_BLOCK_SIZE];
  79         struct scatterlist src_sg, dst_sg;
  80         int padding = 4 << (ci->ci_flags & F2FS_POLICY_FLAGS_PAD_MASK);
  81         char *workbuf, buf[32], *alloc_buf = NULL;
  82         unsigned lim = max_name_len(inode);
  83
  84         if (iname->len <= 0 || iname->len > lim)
  85                 return -EIO;
  86
  87         ciphertext_len = (iname->len < F2FS_CRYPTO_BLOCK_SIZE) ?
  88                 F2FS_CRYPTO_BLOCK_SIZE : iname->len;
  89         ciphertext_len = f2fs_fname_crypto_round_up(ciphertext_len, padding);
  90         ciphertext_len = (ciphertext_len > lim) ? lim : ciphertext_len;
  91
  92         if (ciphertext_len <= sizeof(buf)) {
  93                 workbuf = buf;
  94         } else {
  95                 alloc_buf = kmalloc(ciphertext_len, GFP_NOFS);
  96                 if (!alloc_buf)
  97                         return -ENOMEM;
  98                 workbuf = alloc_buf;
  99         }
 100
 101         /* Allocate request */
 102         req = ablkcipher_request_alloc(tfm, GFP_NOFS);
 103         if (!req) {
 104                 printk_ratelimited(KERN_ERR
 105                         "%s: crypto_request_alloc() failed\n", __func__);
 106                 kfree(alloc_buf);
 107                 return -ENOMEM;
 108         }
 109         ablkcipher_request_set_callback(req,
 110                         CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 111                         f2fs_dir_crypt_complete, &ecr);
 112
 113         /* Copy the input */
 114         memcpy(workbuf, iname->name, iname->len);
 115         if (iname->len < ciphertext_len)
 116                 memset(workbuf + iname->len, 0, ciphertext_len - iname->len);
 117
 118         /* Initialize IV */
 119         memset(iv, 0, F2FS_CRYPTO_BLOCK_SIZE);
 120
 121         /* Create encryption request */
 122         sg_init_one(&src_sg, workbuf, ciphertext_len);
 123         sg_init_one(&dst_sg, oname->name, ciphertext_len);
 124         ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, ciphertext_len, iv);
 125         res = crypto_ablkcipher_encrypt(req);
 126         if (res == -EINPROGRESS || res == -EBUSY) {
 127                 BUG_ON(req->base.data != &ecr);
 128                 wait_for_completion(&ecr.completion);
 129                 res = ecr.res;
 130         }
 131         kfree(alloc_buf);
 132         ablkcipher_request_free(req);
 133         if (res < 0) {
 134                 printk_ratelimited(KERN_ERR
 135                                 "%s: Error (error code %d)\n", __func__, res);
 136         }
 137         oname->len = ciphertext_len;
 138         return res;
 139 }
 140
 141 /*
 142  * f2fs_fname_decrypt()
 143  *      This function decrypts the input filename, and returns
 144  *      the length of the plaintext.
 145  *      Errors are returned as negative numbers.
 146  *      We trust the caller to allocate sufficient memory to oname string.
 147  */
 148 static int f2fs_fname_decrypt(struct inode *inode,
 149                         const struct f2fs_str *iname, struct f2fs_str *oname)
 150 {
 151         struct ablkcipher_request *req = NULL;
 152         DECLARE_F2FS_COMPLETION_RESULT(ecr);
 153         struct scatterlist src_sg, dst_sg;
 154         struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
 155         struct crypto_ablkcipher *tfm = ci->ci_ctfm;
 156         int res = 0;
 157         char iv[F2FS_CRYPTO_BLOCK_SIZE];
 158         unsigned lim = max_name_len(inode);
 159
 160         if (iname->len <= 0 || iname->len > lim)
 161                 return -EIO;
 162
 163         /* Allocate request */
 164         req = ablkcipher_request_alloc(tfm, GFP_NOFS);
 165         if (!req) {
 166                 printk_ratelimited(KERN_ERR
 167                         "%s: crypto_request_alloc() failed\n",  __func__);
 168                 return -ENOMEM;
 169         }
 170         ablkcipher_request_set_callback(req,
 171                 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 172                 f2fs_dir_crypt_complete, &ecr);
 173
 174         /* Initialize IV */
 175         memset(iv, 0, F2FS_CRYPTO_BLOCK_SIZE);
 176
 177         /* Create decryption request */
 178         sg_init_one(&src_sg, iname->name, iname->len);
 179         sg_init_one(&dst_sg, oname->name, oname->len);
 180         ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv);
 181         res = crypto_ablkcipher_decrypt(req);
 182         if (res == -EINPROGRESS || res == -EBUSY) {
 183                 BUG_ON(req->base.data != &ecr);
 184                 wait_for_completion(&ecr.completion);
 185                 res = ecr.res;
 186         }
 187         ablkcipher_request_free(req);
 188         if (res < 0) {
 189                 printk_ratelimited(KERN_ERR
 190                         "%s: Error in f2fs_fname_decrypt (error code %d)\n",
 191                         __func__, res);
 192                 return res;
 193         }
 194
 195         oname->len = strnlen(oname->name, iname->len);
 196         return oname->len;
 197 }
 198
 199 static const char *lookup_table =
 200         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
 201
 202 /**
 203  * f2fs_fname_encode_digest() -
 204  *
 205  * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
 206  * The encoded string is roughly 4/3 times the size of the input string.
 207  */
 208 static int digest_encode(const char *src, int len, char *dst)
 209 {
 210         int i = 0, bits = 0, ac = 0;
 211         char *cp = dst;
 212
 213         while (i < len) {
 214                 ac += (((unsigned char) src[i]) << bits);
 215                 bits += 8;
 216                 do {
 217                         *cp++ = lookup_table[ac & 0x3f];
 218                         ac >>= 6;
 219                         bits -= 6;
 220                 } while (bits >= 6);
 221                 i++;
 222         }
 223         if (bits)
 224                 *cp++ = lookup_table[ac & 0x3f];
 225         return cp - dst;
 226 }
 227
 228 static int digest_decode(const char *src, int len, char *dst)
 229 {
 230         int i = 0, bits = 0, ac = 0;
 231         const char *p;
 232         char *cp = dst;
 233
 234         while (i < len) {
 235                 p = strchr(lookup_table, src[i]);
 236                 if (p == NULL || src[i] == 0)
 237                         return -2;
 238                 ac += (p - lookup_table) << bits;
 239                 bits += 6;
 240                 if (bits >= 8) {
 241                         *cp++ = ac & 0xff;
 242                         ac >>= 8;
 243                         bits -= 8;
 244                 }
 245                 i++;
 246         }
 247         if (ac)
 248                 return -1;
 249         return cp - dst;
 250 }
 251
 252 /**
 253  * f2fs_fname_crypto_round_up() -
 254  *
 255  * Return: The next multiple of block size
 256  */
 257 u32 f2fs_fname_crypto_round_up(u32 size, u32 blksize)
 258 {
 259         return ((size + blksize - 1) / blksize) * blksize;
 260 }
 261
 262 /**
 263  * f2fs_fname_crypto_alloc_obuff() -
 264  *
 265  * Allocates an output buffer that is sufficient for the crypto operation
 266  * specified by the context and the direction.
 267  */
 268 int f2fs_fname_crypto_alloc_buffer(struct inode *inode,
 269                                    u32 ilen, struct f2fs_str *crypto_str)
 270 {
 271         unsigned int olen;
 272         int padding = 16;
 273         struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
 274
 275         if (ci)
 276                 padding = 4 << (ci->ci_flags & F2FS_POLICY_FLAGS_PAD_MASK);
 277         if (padding < F2FS_CRYPTO_BLOCK_SIZE)
 278                 padding = F2FS_CRYPTO_BLOCK_SIZE;
 279         olen = f2fs_fname_crypto_round_up(ilen, padding);
 280         crypto_str->len = olen;
 281         if (olen < F2FS_FNAME_CRYPTO_DIGEST_SIZE * 2)
 282                 olen = F2FS_FNAME_CRYPTO_DIGEST_SIZE * 2;
 283         /* Allocated buffer can hold one more character to null-terminate the
 284          * string */
 285         crypto_str->name = kmalloc(olen + 1, GFP_NOFS);
 286         if (!(crypto_str->name))
 287                 return -ENOMEM;
 288         return 0;
 289 }
 290
 291 /**
 292  * f2fs_fname_crypto_free_buffer() -
 293  *
 294  * Frees the buffer allocated for crypto operation.
 295  */
 296 void f2fs_fname_crypto_free_buffer(struct f2fs_str *crypto_str)
 297 {
 298         if (!crypto_str)
 299                 return;
 300         kfree(crypto_str->name);
 301         crypto_str->name = NULL;
 302 }
 303
 304 /**
 305  * f2fs_fname_disk_to_usr() - converts a filename from disk space to user space
 306  */
 307 int f2fs_fname_disk_to_usr(struct inode *inode,
 308                         f2fs_hash_t *hash,
 309                         const struct f2fs_str *iname,
 310                         struct f2fs_str *oname)
 311 {
 312         const struct qstr qname = FSTR_TO_QSTR(iname);
 313         char buf[24];
 314         int ret;
 315
 316         if (is_dot_dotdot(&qname)) {
 317                 oname->name[0] = '.';
 318                 oname->name[iname->len - 1] = '.';
 319                 oname->len = iname->len;
 320                 return oname->len;
 321         }
 322
 323         if (F2FS_I(inode)->i_crypt_info)
 324                 return f2fs_fname_decrypt(inode, iname, oname);
 325
 326         if (iname->len <= F2FS_FNAME_CRYPTO_DIGEST_SIZE) {
 327                 ret = digest_encode(iname->name, iname->len, oname->name);
 328                 oname->len = ret;
 329                 return ret;
 330         }
 331         if (hash) {
 332                 memcpy(buf, hash, 4);
 333                 memset(buf + 4, 0, 4);
 334         } else
 335                 memset(buf, 0, 8);
 336         memcpy(buf + 8, iname->name + iname->len - 16, 16);
 337         oname->name[0] = '_';
 338         ret = digest_encode(buf, 24, oname->name + 1);
 339         oname->len = ret + 1;
 340         return ret + 1;
 341 }
 342
 343 /**
 344  * f2fs_fname_usr_to_disk() - converts a filename from user space to disk space
 345  */
 346 int f2fs_fname_usr_to_disk(struct inode *inode,
 347                         const struct qstr *iname,
 348                         struct f2fs_str *oname)
 349 {
 350         int res;
 351         struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
 352
 353         if (is_dot_dotdot(iname)) {
 354                 oname->name[0] = '.';
 355                 oname->name[iname->len - 1] = '.';
 356                 oname->len = iname->len;
 357                 return oname->len;
 358         }
 359
 360         if (ci) {
 361                 res = f2fs_fname_encrypt(inode, iname, oname);
 362                 return res;
 363         }
 364         /* Without a proper key, a user is not allowed to modify the filenames
 365          * in a directory. Consequently, a user space name cannot be mapped to
 366          * a disk-space name */
 367         return -EACCES;
 368 }
 369
 370 int f2fs_fname_setup_filename(struct inode *dir, const struct qstr *iname,
 371                               int lookup, struct f2fs_filename *fname)
 372 {
 373         struct f2fs_crypt_info *ci;
 374         int ret = 0, bigname = 0;
 375
 376         memset(fname, 0, sizeof(struct f2fs_filename));
 377         fname->usr_fname = iname;
 378
 379         if (!f2fs_encrypted_inode(dir) || is_dot_dotdot(iname)) {
 380                 fname->disk_name.name = (unsigned char *)iname->name;
 381                 fname->disk_name.len = iname->len;
 382                 return 0;
 383         }
 384         ret = f2fs_get_encryption_info(dir);
 385         if (ret)
 386                 return ret;
 387         ci = F2FS_I(dir)->i_crypt_info;
 388         if (ci) {
 389                 ret = f2fs_fname_crypto_alloc_buffer(dir, iname->len,
 390                                                      &fname->crypto_buf);
 391                 if (ret < 0)
 392                         return ret;
 393                 ret = f2fs_fname_encrypt(dir, iname, &fname->crypto_buf);
 394                 if (ret < 0)
 395                         goto errout;
 396                 fname->disk_name.name = fname->crypto_buf.name;
 397                 fname->disk_name.len = fname->crypto_buf.len;
 398                 return 0;
 399         }
 400         if (!lookup)
 401                 return -EACCES;
 402
 403         /* We don't have the key and we are doing a lookup; decode the
 404          * user-supplied name
 405          */
 406         if (iname->name[0] == '_')
 407                 bigname = 1;
 408         if ((bigname && (iname->len != 33)) ||
 409             (!bigname && (iname->len > 43)))
 410                 return -ENOENT;
 411
 412         fname->crypto_buf.name = kmalloc(32, GFP_KERNEL);
 413         if (fname->crypto_buf.name == NULL)
 414                 return -ENOMEM;
 415         ret = digest_decode(iname->name + bigname, iname->len - bigname,
 416                                 fname->crypto_buf.name);
 417         if (ret < 0) {
 418                 ret = -ENOENT;
 419                 goto errout;
 420         }
 421         fname->crypto_buf.len = ret;
 422         if (bigname) {
 423                 memcpy(&fname->hash, fname->crypto_buf.name, 4);
 424         } else {
 425                 fname->disk_name.name = fname->crypto_buf.name;
 426                 fname->disk_name.len = fname->crypto_buf.len;
 427         }
 428         return 0;
 429 errout:
 430         f2fs_fname_crypto_free_buffer(&fname->crypto_buf);
 431         return ret;
 432 }
 433
 434 void f2fs_fname_free_filename(struct f2fs_filename *fname)
 435 {
 436         kfree(fname->crypto_buf.name);
 437         fname->crypto_buf.name = NULL;
 438         fname->usr_fname = NULL;
 439         fname->disk_name.name = NULL;
 440 }