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Commit 5de0b4d0 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4 crypto: simplify and speed up filename encryption 



Avoid using SHA-1 when calculating the user-visible filename when the
encryption key is available, and avoid decrypting lots of filenames
when searching for a directory entry in a directory block.

Change-Id: If4655f144784978ba0305b597bfa1c8d7bb69e63
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 6ddb2447

fs/ext4/crypto_fname.c

+135 −133
Original line number Diff line number Diff line
@@ -198,106 +198,57 @@ static int ext4_fname_decrypt(struct ext4_fname_crypto_ctx *ctx, 
	return oname->len;

}



static const char *lookup_table =

	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";



/**

 * ext4_fname_encode_digest() -

 *

 * Encodes the input digest using characters from the set [a-zA-Z0-9_+].

 * The encoded string is roughly 4/3 times the size of the input string.

 */

int ext4_fname_encode_digest(char *dst, char *src, u32 len)

static int digest_encode(const char *src, int len, char *dst)

{

	static const char *lookup_table =

		"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_+";

	u32 current_chunk, num_chunks, i;

	char tmp_buf[3];

	u32 c0, c1, c2, c3;



	current_chunk = 0;

	num_chunks = len/3;

	for (i = 0; i < num_chunks; i++) {

		c0 = src[3*i] & 0x3f;

		c1 = (((src[3*i]>>6)&0x3) | ((src[3*i+1] & 0xf)<<2)) & 0x3f;

		c2 = (((src[3*i+1]>>4)&0xf) | ((src[3*i+2] & 0x3)<<4)) & 0x3f;

		c3 = (src[3*i+2]>>2) & 0x3f;

		dst[4*i] = lookup_table[c0];

		dst[4*i+1] = lookup_table[c1];

		dst[4*i+2] = lookup_table[c2];

		dst[4*i+3] = lookup_table[c3];

	}

	if (i*3 < len) {

		memset(tmp_buf, 0, 3);

		memcpy(tmp_buf, &src[3*i], len-3*i);

		c0 = tmp_buf[0] & 0x3f;

		c1 = (((tmp_buf[0]>>6)&0x3) | ((tmp_buf[1] & 0xf)<<2)) & 0x3f;

		c2 = (((tmp_buf[1]>>4)&0xf) | ((tmp_buf[2] & 0x3)<<4)) & 0x3f;

		c3 = (tmp_buf[2]>>2) & 0x3f;

		dst[4*i] = lookup_table[c0];

		dst[4*i+1] = lookup_table[c1];

		dst[4*i+2] = lookup_table[c2];

		dst[4*i+3] = lookup_table[c3];

	int i = 0, bits = 0, ac = 0;

	char *cp = dst;



	while (i < len) {

		ac += (((unsigned char) src[i]) << bits);

		bits += 8;

		do {

			*cp++ = lookup_table[ac & 0x3f];

			ac >>= 6;

			bits -= 6;

		} while (bits >= 6);

		i++;

	}

	return (i * 4);

	if (bits)

		*cp++ = lookup_table[ac & 0x3f];

	return cp - dst;

}



/**

 * ext4_fname_hash() -

 *

 * This function computes the hash of the input filename, and sets the output

 * buffer to the *encoded* digest.  It returns the length of the digest as its

 * return value.  Errors are returned as negative numbers.  We trust the caller

 * to allocate sufficient memory to oname string.

 */

static int ext4_fname_hash(struct ext4_fname_crypto_ctx *ctx,

			   const struct ext4_str *iname,

			   struct ext4_str *oname)

static int digest_decode(const char *src, int len, char *dst)

{

	struct scatterlist sg;

	struct hash_desc desc = {

		.tfm = (struct crypto_hash *)ctx->htfm,

		.flags = CRYPTO_TFM_REQ_MAY_SLEEP

	};

	int res = 0;



	if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) {

		res = ext4_fname_encode_digest(oname->name, iname->name,

					       iname->len);

		oname->len = res;

		return res;

	}



	sg_init_one(&sg, iname->name, iname->len);

	res = crypto_hash_init(&desc);

	if (res) {

		printk(KERN_ERR

		       "%s: Error initializing crypto hash; res = [%d]\n",

		       __func__, res);

		goto out;

	int i = 0, bits = 0, ac = 0;

	const char *p;

	char *cp = dst;



	while (i < len) {

		p = strchr(lookup_table, src[i]);

		if (p == NULL || src[i] == 0)

			return -2;

		ac += (p - lookup_table) << bits;

		bits += 6;

		if (bits >= 8) {

			*cp++ = ac & 0xff;

			ac >>= 8;

			bits -= 8;

		}

	res = crypto_hash_update(&desc, &sg, iname->len);

	if (res) {

		printk(KERN_ERR

		       "%s: Error updating crypto hash; res = [%d]\n",

		       __func__, res);

		goto out;

		i++;

	}

	res = crypto_hash_final(&desc,

		&oname->name[EXT4_FNAME_CRYPTO_DIGEST_SIZE]);

	if (res) {

		printk(KERN_ERR

		       "%s: Error finalizing crypto hash; res = [%d]\n",

		       __func__, res);

		goto out;

	}

	/* Encode the digest as a printable string--this will increase the

	 * size of the digest */

	oname->name[0] = 'I';

	res = ext4_fname_encode_digest(oname->name+1,

		&oname->name[EXT4_FNAME_CRYPTO_DIGEST_SIZE],

		EXT4_FNAME_CRYPTO_DIGEST_SIZE) + 1;

	oname->len = res;

out:

	return res;

	if (ac)

		return -1;

	return cp - dst;

}



/**
@@ -571,9 +522,13 @@ void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str) 
 * ext4_fname_disk_to_usr() - converts a filename from disk space to user space

 */

int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,

			    struct dx_hash_info *hinfo,

			    const struct ext4_str *iname,

			    struct ext4_str *oname)

{

	char buf[24];

	int ret;



	if (ctx == NULL)

		return -EIO;

	if (iname->len < 3) {
@@ -587,18 +542,33 @@ int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx, 
	}

	if (ctx->has_valid_key)

		return ext4_fname_decrypt(ctx, iname, oname);

	else

		return ext4_fname_hash(ctx, iname, oname);



	if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) {

		ret = digest_encode(iname->name, iname->len, oname->name);

		oname->len = ret;

		return ret;

	}

	if (hinfo) {

		memcpy(buf, &hinfo->hash, 4);

		memcpy(buf+4, &hinfo->minor_hash, 4);

	} else

		memset(buf, 0, 8);

	memcpy(buf + 8, iname->name + iname->len - 16, 16);

	oname->name[0] = '_';

	ret = digest_encode(buf, 24, oname->name+1);

	oname->len = ret + 1;

	return ret + 1;

}



int ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,

			   struct dx_hash_info *hinfo,

			   const struct ext4_dir_entry_2 *de,

			   struct ext4_str *oname)

{

	struct ext4_str iname = {.name = (unsigned char *) de->name,

				 .len = de->name_len };



	return _ext4_fname_disk_to_usr(ctx, &iname, oname);

	return _ext4_fname_disk_to_usr(ctx, hinfo, &iname, oname);

}
@@ -640,10 +610,11 @@ int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx, 
			    const struct qstr *iname,

			    struct dx_hash_info *hinfo)

{

	struct ext4_str tmp, tmp2;

	struct ext4_str tmp;

	int ret = 0;

	char buf[EXT4_FNAME_CRYPTO_DIGEST_SIZE+1];



	if (!ctx || !ctx->has_valid_key ||

	if (!ctx ||

	    ((iname->name[0] == '.') &&

	     ((iname->len == 1) ||

	      ((iname->name[1] == '.') && (iname->len == 2))))) {
@@ -651,59 +622,90 @@ int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx, 
		return 0;

	}



	if (!ctx->has_valid_key && iname->name[0] == '_') {

		if (iname->len != 33)

			return -ENOENT;

		ret = digest_decode(iname->name+1, iname->len, buf);

		if (ret != 24)

			return -ENOENT;

		memcpy(&hinfo->hash, buf, 4);

		memcpy(&hinfo->minor_hash, buf + 4, 4);

		return 0;

	}



	if (!ctx->has_valid_key && iname->name[0] != '_') {

		if (iname->len > 43)

			return -ENOENT;

		ret = digest_decode(iname->name, iname->len, buf);

		ext4fs_dirhash(buf, ret, hinfo);

		return 0;

	}



	/* First encrypt the plaintext name */

	ret = ext4_fname_crypto_alloc_buffer(ctx, iname->len, &tmp);

	if (ret < 0)

		return ret;



	ret = ext4_fname_encrypt(ctx, iname, &tmp);

	if (ret < 0)

		goto out;



	tmp2.len = (4 * ((EXT4_FNAME_CRYPTO_DIGEST_SIZE + 2) / 3)) + 1;

	tmp2.name = kmalloc(tmp2.len + 1, GFP_KERNEL);

	if (tmp2.name == NULL) {

		ret = -ENOMEM;

		goto out;

	if (ret >= 0) {

		ext4fs_dirhash(tmp.name, tmp.len, hinfo);

		ret = 0;

	}



	ret = ext4_fname_hash(ctx, &tmp, &tmp2);

	if (ret > 0)

		ext4fs_dirhash(tmp2.name, tmp2.len, hinfo);

	ext4_fname_crypto_free_buffer(&tmp2);

out:

	ext4_fname_crypto_free_buffer(&tmp);

	return ret;

}



/**

 * ext4_fname_disk_to_htree() - converts a filename from disk space to htree-access string

 */

int ext4_fname_disk_to_hash(struct ext4_fname_crypto_ctx *ctx,

			    const struct ext4_dir_entry_2 *de,

			    struct dx_hash_info *hinfo)

int ext4_fname_match(struct ext4_fname_crypto_ctx *ctx, struct ext4_str *cstr,

		     int len, const char * const name,

		     struct ext4_dir_entry_2 *de)

{

	struct ext4_str iname = {.name = (unsigned char *) de->name,

				 .len = de->name_len};

	struct ext4_str tmp;

	int ret;

	int ret = -ENOENT;

	int bigname = (*name == '_');



	if (!ctx ||

	    ((iname.name[0] == '.') &&

	     ((iname.len == 1) ||

	      ((iname.name[1] == '.') && (iname.len == 2))))) {

		ext4fs_dirhash(iname.name, iname.len, hinfo);

		return 0;

	}

	if (ctx->has_valid_key) {

		if (cstr->name == NULL) {

			struct qstr istr;



	tmp.len = (4 * ((EXT4_FNAME_CRYPTO_DIGEST_SIZE + 2) / 3)) + 1;

	tmp.name = kmalloc(tmp.len + 1, GFP_KERNEL);

	if (tmp.name == NULL)

			ret = ext4_fname_crypto_alloc_buffer(ctx, len, cstr);

			if (ret < 0)

				goto errout;

			istr.name = name;

			istr.len = len;

			ret = ext4_fname_encrypt(ctx, &istr, cstr);

			if (ret < 0)

				goto errout;

		}

	} else {

		if (cstr->name == NULL) {

			cstr->name = kmalloc(32, GFP_KERNEL);

			if (cstr->name == NULL)

				return -ENOMEM;



	ret = ext4_fname_hash(ctx, &iname, &tmp);

	if (ret > 0)

		ext4fs_dirhash(tmp.name, tmp.len, hinfo);

	ext4_fname_crypto_free_buffer(&tmp);

			if ((bigname && (len != 33)) ||

			    (!bigname && (len > 43)))

				goto errout;

			ret = digest_decode(name+bigname, len-bigname,

					    cstr->name);

			if (ret < 0) {

				ret = -ENOENT;

				goto errout;

			}

			cstr->len = ret;

		}

		if (bigname) {

			if (de->name_len < 16)

				return 0;

			ret = memcmp(de->name + de->name_len - 16,

				     cstr->name + 8, 16);

			return (ret == 0) ? 1 : 0;

		}

	}

	if (de->name_len != cstr->len)

		return 0;

	ret = memcmp(de->name, cstr->name, cstr->len);

	return (ret == 0) ? 1 : 0;

errout:

	kfree(cstr->name);

	cstr->name = NULL;

	return ret;

}

fs/ext4/dir.c

+1 −1
Original line number Diff line number Diff line
@@ -249,7 +249,7 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx) 
				} else {

					/* Directory is encrypted */

					err = ext4_fname_disk_to_usr(enc_ctx,

							de, &fname_crypto_str);

						NULL, de, &fname_crypto_str);

					if (err < 0)

						goto errout;

					if (!dir_emit(ctx,

fs/ext4/ext4.h

+6 −3
Original line number Diff line number Diff line
@@ -2093,9 +2093,11 @@ u32 ext4_fname_crypto_round_up(u32 size, u32 blksize); 
int ext4_fname_crypto_alloc_buffer(struct ext4_fname_crypto_ctx *ctx,

				   u32 ilen, struct ext4_str *crypto_str);

int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,

			    struct dx_hash_info *hinfo,

			    const struct ext4_str *iname,

			    struct ext4_str *oname);

int ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,

			   struct dx_hash_info *hinfo,

			   const struct ext4_dir_entry_2 *de,

			   struct ext4_str *oname);

int ext4_fname_usr_to_disk(struct ext4_fname_crypto_ctx *ctx,
@@ -2104,11 +2106,12 @@ int ext4_fname_usr_to_disk(struct ext4_fname_crypto_ctx *ctx, 
int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx,

			   const struct qstr *iname,

			   struct dx_hash_info *hinfo);

int ext4_fname_disk_to_hash(struct ext4_fname_crypto_ctx *ctx,

			    const struct ext4_dir_entry_2 *de,

			    struct dx_hash_info *hinfo);

int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx,

				      u32 namelen);

int ext4_fname_match(struct ext4_fname_crypto_ctx *ctx, struct ext4_str *cstr,

		     int len, const char * const name,

		     struct ext4_dir_entry_2 *de);





#ifdef CONFIG_EXT4_FS_ENCRYPTION

void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx);

fs/ext4/namei.c

+6 −66
Original line number Diff line number Diff line
@@ -640,7 +640,7 @@ static struct stats dx_show_leaf(struct inode *dir, 
						ext4_put_fname_crypto_ctx(&ctx);

						ctx = NULL;

					}

					res = ext4_fname_disk_to_usr(ctx, de,

					res = ext4_fname_disk_to_usr(ctx, NULL, de,

							&fname_crypto_str);

					if (res < 0) {

						printk(KERN_WARNING "Error "
@@ -653,15 +653,8 @@ static struct stats dx_show_leaf(struct inode *dir, 
						name = fname_crypto_str.name;

						len = fname_crypto_str.len;

					}

					res = ext4_fname_disk_to_hash(ctx, de,

					ext4fs_dirhash(de->name, de->name_len,

						       &h);

					if (res < 0) {

						printk(KERN_WARNING "Error "

							"converting filename "

							"from disk to htree"

							"\n");

						h.hash = 0xDEADBEEF;

					}

					printk("%*.s:(E)%x.%u ", len, name,

					       h.hash, (unsigned) ((char *) de

								   - base));
@@ -1008,15 +1001,7 @@ static int htree_dirblock_to_tree(struct file *dir_file, 
			/* silently ignore the rest of the block */

			break;

		}

#ifdef CONFIG_EXT4_FS_ENCRYPTION

		err = ext4_fname_disk_to_hash(ctx, de, hinfo);

		if (err < 0) {

			count = err;

			goto errout;

		}

#else

		ext4fs_dirhash(de->name, de->name_len, hinfo);

#endif

		if ((hinfo->hash < start_hash) ||

		    ((hinfo->hash == start_hash) &&

		     (hinfo->minor_hash < start_minor_hash)))
@@ -1032,7 +1017,7 @@ static int htree_dirblock_to_tree(struct file *dir_file, 
				   &tmp_str);

		} else {

			/* Directory is encrypted */

			err = ext4_fname_disk_to_usr(ctx, de,

			err = ext4_fname_disk_to_usr(ctx, hinfo, de,

						     &fname_crypto_str);

			if (err < 0) {

				count = err;
@@ -1193,26 +1178,10 @@ static int dx_make_map(struct inode *dir, struct ext4_dir_entry_2 *de, 
	int count = 0;

	char *base = (char *) de;

	struct dx_hash_info h = *hinfo;

#ifdef CONFIG_EXT4_FS_ENCRYPTION

	struct ext4_fname_crypto_ctx *ctx = NULL;

	int err;



	ctx = ext4_get_fname_crypto_ctx(dir, EXT4_NAME_LEN);

	if (IS_ERR(ctx))

		return PTR_ERR(ctx);

#endif



	while ((char *) de < base + blocksize) {

		if (de->name_len && de->inode) {

#ifdef CONFIG_EXT4_FS_ENCRYPTION

			err = ext4_fname_disk_to_hash(ctx, de, &h);

			if (err < 0) {

				ext4_put_fname_crypto_ctx(&ctx);

				return err;

			}

#else

			ext4fs_dirhash(de->name, de->name_len, &h);

#endif

			map_tail--;

			map_tail->hash = h.hash;

			map_tail->offs = ((char *) de - base)>>2;
@@ -1223,9 +1192,6 @@ static int dx_make_map(struct inode *dir, struct ext4_dir_entry_2 *de, 
		/* XXX: do we need to check rec_len == 0 case? -Chris */

		de = ext4_next_entry(de, blocksize);

	}

#ifdef CONFIG_EXT4_FS_ENCRYPTION

	ext4_put_fname_crypto_ctx(&ctx);

#endif

	return count;

}
@@ -1287,16 +1253,8 @@ static inline int ext4_match(struct ext4_fname_crypto_ctx *ctx, 
		return 0;



#ifdef CONFIG_EXT4_FS_ENCRYPTION

	if (ctx) {

		/* Directory is encrypted */

		res = ext4_fname_disk_to_usr(ctx, de, fname_crypto_str);

		if (res < 0)

			return res;

		if (len != res)

			return 0;

		res = memcmp(name, fname_crypto_str->name, len);

		return (res == 0) ? 1 : 0;

	}

	if (ctx)

		return ext4_fname_match(ctx, fname_crypto_str, len, name, de);

#endif

	if (len != de->name_len)

		return 0;
@@ -1324,16 +1282,6 @@ int search_dir(struct buffer_head *bh, char *search_buf, int buf_size, 
	if (IS_ERR(ctx))

		return -1;



	if (ctx != NULL) {

		/* Allocate buffer to hold maximum name length */

		res = ext4_fname_crypto_alloc_buffer(ctx, EXT4_NAME_LEN,

						     &fname_crypto_str);

		if (res < 0) {

			ext4_put_fname_crypto_ctx(&ctx);

			return -1;

		}

	}



	de = (struct ext4_dir_entry_2 *)search_buf;

	dlimit = search_buf + buf_size;

	while ((char *) de < dlimit) {
@@ -1872,14 +1820,6 @@ int ext4_find_dest_de(struct inode *dir, struct inode *inode, 
			return res;

		}

		reclen = EXT4_DIR_REC_LEN(res);



		/* Allocate buffer to hold maximum name length */

		res = ext4_fname_crypto_alloc_buffer(ctx, EXT4_NAME_LEN,

						     &fname_crypto_str);

		if (res < 0) {

			ext4_put_fname_crypto_ctx(&ctx);

			return -1;

		}

	}



	de = (struct ext4_dir_entry_2 *)buf;

fs/ext4/symlink.c

+1 −1
Original line number Diff line number Diff line
@@ -74,7 +74,7 @@ static void *ext4_follow_link(struct dentry *dentry, struct nameidata *nd) 
		goto errout;

	}

	pstr.name = paddr;

	res = _ext4_fname_disk_to_usr(ctx, &cstr, &pstr);

	res = _ext4_fname_disk_to_usr(ctx, NULL, &cstr, &pstr);

	if (res < 0)

		goto errout;

	/* Null-terminate the name */