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