2 * linux/fs/ext4/crypto_fname.c
4 * Copyright (C) 2015, Google, Inc.
6 * This contains functions for filename crypto management in ext4
8 * Written by Uday Savagaonkar, 2014.
10 * This has not yet undergone a rigorous security audit.
14 #include <crypto/hash.h>
15 #include <crypto/sha.h>
16 #include <keys/encrypted-type.h>
17 #include <keys/user-type.h>
18 #include <linux/crypto.h>
19 #include <linux/gfp.h>
20 #include <linux/kernel.h>
21 #include <linux/key.h>
22 #include <linux/key.h>
23 #include <linux/list.h>
24 #include <linux/mempool.h>
25 #include <linux/random.h>
26 #include <linux/scatterlist.h>
27 #include <linux/spinlock_types.h>
30 #include "ext4_crypto.h"
34 * ext4_dir_crypt_complete() -
36 static void ext4_dir_crypt_complete(struct crypto_async_request *req, int res)
38 struct ext4_completion_result *ecr = req->data;
40 if (res == -EINPROGRESS)
43 complete(&ecr->completion);
46 bool ext4_valid_filenames_enc_mode(uint32_t mode)
48 return (mode == EXT4_ENCRYPTION_MODE_AES_256_CTS);
52 * ext4_fname_encrypt() -
54 * This function encrypts the input filename, and returns the length of the
55 * ciphertext. Errors are returned as negative numbers. We trust the caller to
56 * allocate sufficient memory to oname string.
58 static int ext4_fname_encrypt(struct ext4_fname_crypto_ctx *ctx,
59 const struct qstr *iname,
60 struct ext4_str *oname)
63 struct ablkcipher_request *req = NULL;
64 DECLARE_EXT4_COMPLETION_RESULT(ecr);
65 struct crypto_ablkcipher *tfm = ctx->ctfm;
67 char iv[EXT4_CRYPTO_BLOCK_SIZE];
68 struct scatterlist sg[1];
71 if (iname->len <= 0 || iname->len > ctx->lim)
74 ciphertext_len = (iname->len < EXT4_CRYPTO_BLOCK_SIZE) ?
75 EXT4_CRYPTO_BLOCK_SIZE : iname->len;
76 ciphertext_len = (ciphertext_len > ctx->lim)
77 ? ctx->lim : ciphertext_len;
79 /* Allocate request */
80 req = ablkcipher_request_alloc(tfm, GFP_NOFS);
83 KERN_ERR "%s: crypto_request_alloc() failed\n", __func__);
86 ablkcipher_request_set_callback(req,
87 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
88 ext4_dir_crypt_complete, &ecr);
90 /* Map the workpage */
91 workbuf = kmap(ctx->workpage);
94 memcpy(workbuf, iname->name, iname->len);
95 if (iname->len < ciphertext_len)
96 memset(workbuf + iname->len, 0, ciphertext_len - iname->len);
99 memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
101 /* Create encryption request */
102 sg_init_table(sg, 1);
103 sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
104 ablkcipher_request_set_crypt(req, sg, sg, iname->len, iv);
105 res = crypto_ablkcipher_encrypt(req);
106 if (res == -EINPROGRESS || res == -EBUSY) {
107 BUG_ON(req->base.data != &ecr);
108 wait_for_completion(&ecr.completion);
112 /* Copy the result to output */
113 memcpy(oname->name, workbuf, ciphertext_len);
114 res = ciphertext_len;
116 kunmap(ctx->workpage);
117 ablkcipher_request_free(req);
120 KERN_ERR "%s: Error (error code %d)\n", __func__, res);
122 oname->len = ciphertext_len;
127 * ext4_fname_decrypt()
128 * This function decrypts the input filename, and returns
129 * the length of the plaintext.
130 * Errors are returned as negative numbers.
131 * We trust the caller to allocate sufficient memory to oname string.
133 static int ext4_fname_decrypt(struct ext4_fname_crypto_ctx *ctx,
134 const struct ext4_str *iname,
135 struct ext4_str *oname)
137 struct ext4_str tmp_in[2], tmp_out[1];
138 struct ablkcipher_request *req = NULL;
139 DECLARE_EXT4_COMPLETION_RESULT(ecr);
140 struct scatterlist sg[1];
141 struct crypto_ablkcipher *tfm = ctx->ctfm;
143 char iv[EXT4_CRYPTO_BLOCK_SIZE];
146 if (iname->len <= 0 || iname->len > ctx->lim)
149 tmp_in[0].name = iname->name;
150 tmp_in[0].len = iname->len;
151 tmp_out[0].name = oname->name;
153 /* Allocate request */
154 req = ablkcipher_request_alloc(tfm, GFP_NOFS);
157 KERN_ERR "%s: crypto_request_alloc() failed\n", __func__);
160 ablkcipher_request_set_callback(req,
161 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
162 ext4_dir_crypt_complete, &ecr);
164 /* Map the workpage */
165 workbuf = kmap(ctx->workpage);
168 memcpy(workbuf, iname->name, iname->len);
171 memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
173 /* Create encryption request */
174 sg_init_table(sg, 1);
175 sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
176 ablkcipher_request_set_crypt(req, sg, sg, iname->len, iv);
177 res = crypto_ablkcipher_decrypt(req);
178 if (res == -EINPROGRESS || res == -EBUSY) {
179 BUG_ON(req->base.data != &ecr);
180 wait_for_completion(&ecr.completion);
184 /* Copy the result to output */
185 memcpy(oname->name, workbuf, iname->len);
188 kunmap(ctx->workpage);
189 ablkcipher_request_free(req);
192 KERN_ERR "%s: Error in ext4_fname_encrypt (error code %d)\n",
197 oname->len = strnlen(oname->name, iname->len);
202 * ext4_fname_encode_digest() -
204 * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
205 * The encoded string is roughly 4/3 times the size of the input string.
207 int ext4_fname_encode_digest(char *dst, char *src, u32 len)
209 static const char *lookup_table =
210 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_+";
211 u32 current_chunk, num_chunks, i;
217 for (i = 0; i < num_chunks; i++) {
218 c0 = src[3*i] & 0x3f;
219 c1 = (((src[3*i]>>6)&0x3) | ((src[3*i+1] & 0xf)<<2)) & 0x3f;
220 c2 = (((src[3*i+1]>>4)&0xf) | ((src[3*i+2] & 0x3)<<4)) & 0x3f;
221 c3 = (src[3*i+2]>>2) & 0x3f;
222 dst[4*i] = lookup_table[c0];
223 dst[4*i+1] = lookup_table[c1];
224 dst[4*i+2] = lookup_table[c2];
225 dst[4*i+3] = lookup_table[c3];
228 memset(tmp_buf, 0, 3);
229 memcpy(tmp_buf, &src[3*i], len-3*i);
230 c0 = tmp_buf[0] & 0x3f;
231 c1 = (((tmp_buf[0]>>6)&0x3) | ((tmp_buf[1] & 0xf)<<2)) & 0x3f;
232 c2 = (((tmp_buf[1]>>4)&0xf) | ((tmp_buf[2] & 0x3)<<4)) & 0x3f;
233 c3 = (tmp_buf[2]>>2) & 0x3f;
234 dst[4*i] = lookup_table[c0];
235 dst[4*i+1] = lookup_table[c1];
236 dst[4*i+2] = lookup_table[c2];
237 dst[4*i+3] = lookup_table[c3];
244 * ext4_fname_hash() -
246 * This function computes the hash of the input filename, and sets the output
247 * buffer to the *encoded* digest. It returns the length of the digest as its
248 * return value. Errors are returned as negative numbers. We trust the caller
249 * to allocate sufficient memory to oname string.
251 static int ext4_fname_hash(struct ext4_fname_crypto_ctx *ctx,
252 const struct ext4_str *iname,
253 struct ext4_str *oname)
255 struct scatterlist sg;
256 struct hash_desc desc = {
257 .tfm = (struct crypto_hash *)ctx->htfm,
258 .flags = CRYPTO_TFM_REQ_MAY_SLEEP
262 if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) {
263 res = ext4_fname_encode_digest(oname->name, iname->name,
269 sg_init_one(&sg, iname->name, iname->len);
270 res = crypto_hash_init(&desc);
273 "%s: Error initializing crypto hash; res = [%d]\n",
277 res = crypto_hash_update(&desc, &sg, iname->len);
280 "%s: Error updating crypto hash; res = [%d]\n",
284 res = crypto_hash_final(&desc,
285 &oname->name[EXT4_FNAME_CRYPTO_DIGEST_SIZE]);
288 "%s: Error finalizing crypto hash; res = [%d]\n",
292 /* Encode the digest as a printable string--this will increase the
293 * size of the digest */
294 oname->name[0] = 'I';
295 res = ext4_fname_encode_digest(oname->name+1,
296 &oname->name[EXT4_FNAME_CRYPTO_DIGEST_SIZE],
297 EXT4_FNAME_CRYPTO_DIGEST_SIZE) + 1;
304 * ext4_free_fname_crypto_ctx() -
306 * Frees up a crypto context.
308 void ext4_free_fname_crypto_ctx(struct ext4_fname_crypto_ctx *ctx)
310 if (ctx == NULL || IS_ERR(ctx))
313 if (ctx->ctfm && !IS_ERR(ctx->ctfm))
314 crypto_free_ablkcipher(ctx->ctfm);
315 if (ctx->htfm && !IS_ERR(ctx->htfm))
316 crypto_free_hash(ctx->htfm);
317 if (ctx->workpage && !IS_ERR(ctx->workpage))
318 __free_page(ctx->workpage);
323 * ext4_put_fname_crypto_ctx() -
325 * Return: The crypto context onto free list. If the free list is above a
326 * threshold, completely frees up the context, and returns the memory.
328 * TODO: Currently we directly free the crypto context. Eventually we should
329 * add code it to return to free list. Such an approach will increase
330 * efficiency of directory lookup.
332 void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx)
334 if (*ctx == NULL || IS_ERR(*ctx))
336 ext4_free_fname_crypto_ctx(*ctx);
341 * ext4_search_fname_crypto_ctx() -
343 static struct ext4_fname_crypto_ctx *ext4_search_fname_crypto_ctx(
344 const struct ext4_encryption_key *key)
350 * ext4_alloc_fname_crypto_ctx() -
352 struct ext4_fname_crypto_ctx *ext4_alloc_fname_crypto_ctx(
353 const struct ext4_encryption_key *key)
355 struct ext4_fname_crypto_ctx *ctx;
357 ctx = kmalloc(sizeof(struct ext4_fname_crypto_ctx), GFP_NOFS);
359 return ERR_PTR(-ENOMEM);
360 if (key->mode == EXT4_ENCRYPTION_MODE_INVALID) {
361 /* This will automatically set key mode to invalid
362 * As enum for ENCRYPTION_MODE_INVALID is zero */
363 memset(&ctx->key, 0, sizeof(ctx->key));
365 memcpy(&ctx->key, key, sizeof(struct ext4_encryption_key));
367 ctx->has_valid_key = (EXT4_ENCRYPTION_MODE_INVALID == key->mode)
369 ctx->ctfm_key_is_ready = 0;
372 ctx->workpage = NULL;
377 * ext4_get_fname_crypto_ctx() -
379 * Allocates a free crypto context and initializes it to hold
380 * the crypto material for the inode.
382 * Return: NULL if not encrypted. Error value on error. Valid pointer otherwise.
384 struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(
385 struct inode *inode, u32 max_ciphertext_len)
387 struct ext4_fname_crypto_ctx *ctx;
388 struct ext4_inode_info *ei = EXT4_I(inode);
391 /* Check if the crypto policy is set on the inode */
392 res = ext4_encrypted_inode(inode);
396 if (!ext4_has_encryption_key(inode))
397 ext4_generate_encryption_key(inode);
399 /* Get a crypto context based on the key.
400 * A new context is allocated if no context matches the requested key.
402 ctx = ext4_search_fname_crypto_ctx(&(ei->i_encryption_key));
404 ctx = ext4_alloc_fname_crypto_ctx(&(ei->i_encryption_key));
408 if (ctx->has_valid_key) {
409 if (ctx->key.mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
410 printk_once(KERN_WARNING
411 "ext4: unsupported key mode %d\n",
413 return ERR_PTR(-ENOKEY);
416 /* As a first cut, we will allocate new tfm in every call.
417 * later, we will keep the tfm around, in case the key gets
419 if (ctx->ctfm == NULL) {
420 ctx->ctfm = crypto_alloc_ablkcipher("cts(cbc(aes))",
423 if (IS_ERR(ctx->ctfm)) {
424 res = PTR_ERR(ctx->ctfm);
426 KERN_DEBUG "%s: error (%d) allocating crypto tfm\n",
429 ext4_put_fname_crypto_ctx(&ctx);
432 if (ctx->ctfm == NULL) {
434 KERN_DEBUG "%s: could not allocate crypto tfm\n",
436 ext4_put_fname_crypto_ctx(&ctx);
437 return ERR_PTR(-ENOMEM);
439 if (ctx->workpage == NULL)
440 ctx->workpage = alloc_page(GFP_NOFS);
441 if (IS_ERR(ctx->workpage)) {
442 res = PTR_ERR(ctx->workpage);
444 KERN_DEBUG "%s: error (%d) allocating work page\n",
446 ctx->workpage = NULL;
447 ext4_put_fname_crypto_ctx(&ctx);
450 if (ctx->workpage == NULL) {
452 KERN_DEBUG "%s: could not allocate work page\n",
454 ext4_put_fname_crypto_ctx(&ctx);
455 return ERR_PTR(-ENOMEM);
457 ctx->lim = max_ciphertext_len;
458 crypto_ablkcipher_clear_flags(ctx->ctfm, ~0);
459 crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctx->ctfm),
460 CRYPTO_TFM_REQ_WEAK_KEY);
462 /* If we are lucky, we will get a context that is already
463 * set up with the right key. Else, we will have to
465 if (!ctx->ctfm_key_is_ready) {
466 /* Since our crypto objectives for filename encryption
468 * we directly use the inode master key */
469 res = crypto_ablkcipher_setkey(ctx->ctfm,
470 ctx->key.raw, ctx->key.size);
472 ext4_put_fname_crypto_ctx(&ctx);
473 return ERR_PTR(-EIO);
475 ctx->ctfm_key_is_ready = 1;
477 /* In the current implementation, key should never be
478 * marked "ready" for a context that has just been
479 * allocated. So we should never reach here */
483 if (ctx->htfm == NULL)
484 ctx->htfm = crypto_alloc_hash("sha256", 0, CRYPTO_ALG_ASYNC);
485 if (IS_ERR(ctx->htfm)) {
486 res = PTR_ERR(ctx->htfm);
487 printk(KERN_DEBUG "%s: error (%d) allocating hash tfm\n",
490 ext4_put_fname_crypto_ctx(&ctx);
493 if (ctx->htfm == NULL) {
494 printk(KERN_DEBUG "%s: could not allocate hash tfm\n",
496 ext4_put_fname_crypto_ctx(&ctx);
497 return ERR_PTR(-ENOMEM);
504 * ext4_fname_crypto_round_up() -
506 * Return: The next multiple of block size
508 u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
510 return ((size+blksize-1)/blksize)*blksize;
514 * ext4_fname_crypto_namelen_on_disk() -
516 int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx,
523 if (!(ctx->has_valid_key))
525 ciphertext_len = (namelen < EXT4_CRYPTO_BLOCK_SIZE) ?
526 EXT4_CRYPTO_BLOCK_SIZE : namelen;
527 ciphertext_len = (ciphertext_len > ctx->lim)
528 ? ctx->lim : ciphertext_len;
529 return (int) ciphertext_len;
533 * ext4_fname_crypto_alloc_obuff() -
535 * Allocates an output buffer that is sufficient for the crypto operation
536 * specified by the context and the direction.
538 int ext4_fname_crypto_alloc_buffer(struct ext4_fname_crypto_ctx *ctx,
539 u32 ilen, struct ext4_str *crypto_str)
545 olen = ext4_fname_crypto_round_up(ilen, EXT4_CRYPTO_BLOCK_SIZE);
546 crypto_str->len = olen;
547 if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2)
548 olen = EXT4_FNAME_CRYPTO_DIGEST_SIZE*2;
549 /* Allocated buffer can hold one more character to null-terminate the
551 crypto_str->name = kmalloc(olen+1, GFP_NOFS);
552 if (!(crypto_str->name))
558 * ext4_fname_crypto_free_buffer() -
560 * Frees the buffer allocated for crypto operation.
562 void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str)
566 kfree(crypto_str->name);
567 crypto_str->name = NULL;
571 * ext4_fname_disk_to_usr() - converts a filename from disk space to user space
573 int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
574 const struct ext4_str *iname,
575 struct ext4_str *oname)
579 if (iname->len < 3) {
580 /*Check for . and .. */
581 if (iname->name[0] == '.' && iname->name[iname->len-1] == '.') {
582 oname->name[0] = '.';
583 oname->name[iname->len-1] = '.';
584 oname->len = iname->len;
588 if (ctx->has_valid_key)
589 return ext4_fname_decrypt(ctx, iname, oname);
591 return ext4_fname_hash(ctx, iname, oname);
594 int ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
595 const struct ext4_dir_entry_2 *de,
596 struct ext4_str *oname)
598 struct ext4_str iname = {.name = (unsigned char *) de->name,
599 .len = de->name_len };
601 return _ext4_fname_disk_to_usr(ctx, &iname, oname);
606 * ext4_fname_usr_to_disk() - converts a filename from user space to disk space
608 int ext4_fname_usr_to_disk(struct ext4_fname_crypto_ctx *ctx,
609 const struct qstr *iname,
610 struct ext4_str *oname)
616 if (iname->len < 3) {
617 /*Check for . and .. */
618 if (iname->name[0] == '.' &&
619 iname->name[iname->len-1] == '.') {
620 oname->name[0] = '.';
621 oname->name[iname->len-1] = '.';
622 oname->len = iname->len;
626 if (ctx->has_valid_key) {
627 res = ext4_fname_encrypt(ctx, iname, oname);
630 /* Without a proper key, a user is not allowed to modify the filenames
631 * in a directory. Consequently, a user space name cannot be mapped to
632 * a disk-space name */
637 * Calculate the htree hash from a filename from user space
639 int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx,
640 const struct qstr *iname,
641 struct dx_hash_info *hinfo)
643 struct ext4_str tmp, tmp2;
646 if (!ctx || !ctx->has_valid_key ||
647 ((iname->name[0] == '.') &&
648 ((iname->len == 1) ||
649 ((iname->name[1] == '.') && (iname->len == 2))))) {
650 ext4fs_dirhash(iname->name, iname->len, hinfo);
654 /* First encrypt the plaintext name */
655 ret = ext4_fname_crypto_alloc_buffer(ctx, iname->len, &tmp);
659 ret = ext4_fname_encrypt(ctx, iname, &tmp);
663 tmp2.len = (4 * ((EXT4_FNAME_CRYPTO_DIGEST_SIZE + 2) / 3)) + 1;
664 tmp2.name = kmalloc(tmp2.len + 1, GFP_KERNEL);
665 if (tmp2.name == NULL) {
670 ret = ext4_fname_hash(ctx, &tmp, &tmp2);
672 ext4fs_dirhash(tmp2.name, tmp2.len, hinfo);
673 ext4_fname_crypto_free_buffer(&tmp2);
675 ext4_fname_crypto_free_buffer(&tmp);
680 * ext4_fname_disk_to_htree() - converts a filename from disk space to htree-access string
682 int ext4_fname_disk_to_hash(struct ext4_fname_crypto_ctx *ctx,
683 const struct ext4_dir_entry_2 *de,
684 struct dx_hash_info *hinfo)
686 struct ext4_str iname = {.name = (unsigned char *) de->name,
687 .len = de->name_len};
692 ((iname.name[0] == '.') &&
694 ((iname.name[1] == '.') && (iname.len == 2))))) {
695 ext4fs_dirhash(iname.name, iname.len, hinfo);
699 tmp.len = (4 * ((EXT4_FNAME_CRYPTO_DIGEST_SIZE + 2) / 3)) + 1;
700 tmp.name = kmalloc(tmp.len + 1, GFP_KERNEL);
701 if (tmp.name == NULL)
704 ret = ext4_fname_hash(ctx, &iname, &tmp);
706 ext4fs_dirhash(tmp.name, tmp.len, hinfo);
707 ext4_fname_crypto_free_buffer(&tmp);