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| author | Theodore Ts'o <tytso@mit.edu> | 2015-05-01 23:56:50 +0300 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2015-05-01 23:56:50 +0300 |
| commit | a44cd7a05496d60fd2ba8cca080e3db8f481549b (patch) | |
| tree | dd8d05d845817e4a429804d8ffe09dd68b6881e6 /fs/ext4/crypto_fname.c | |
| parent | 5de0b4d0cd153c471640b13aae6ae6d18d0a4603 (diff) | |
| download | linux-a44cd7a05496d60fd2ba8cca080e3db8f481549b.tar.xz | |
ext4 crypto: add padding to filenames before encrypting
This obscures the length of the filenames, to decrease the amount of
information leakage. By default, we pad the filenames to the next 4
byte boundaries. This costs nothing, since the directory entries are
aligned to 4 byte boundaries anyway. Filenames can also be padded to
8, 16, or 32 bytes, which will consume more directory space.
Change-Id: Ibb7a0fb76d2c48e2061240a709358ff40b14f322
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/crypto_fname.c')
| -rw-r--r-- | fs/ext4/crypto_fname.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/fs/ext4/crypto_fname.c b/fs/ext4/crypto_fname.c index 7a877e609e5f..fded02f72299 100644 --- a/fs/ext4/crypto_fname.c +++ b/fs/ext4/crypto_fname.c @@ -66,6 +66,7 @@ static int ext4_fname_encrypt(struct ext4_fname_crypto_ctx *ctx, int res = 0; char iv[EXT4_CRYPTO_BLOCK_SIZE]; struct scatterlist sg[1]; + int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK); char *workbuf; if (iname->len <= 0 || iname->len > ctx->lim) @@ -73,6 +74,7 @@ static int ext4_fname_encrypt(struct ext4_fname_crypto_ctx *ctx, ciphertext_len = (iname->len < EXT4_CRYPTO_BLOCK_SIZE) ? EXT4_CRYPTO_BLOCK_SIZE : iname->len; + ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding); ciphertext_len = (ciphertext_len > ctx->lim) ? ctx->lim : ciphertext_len; @@ -101,7 +103,7 @@ static int ext4_fname_encrypt(struct ext4_fname_crypto_ctx *ctx, /* Create encryption request */ sg_init_table(sg, 1); sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0); - ablkcipher_request_set_crypt(req, sg, sg, iname->len, iv); + ablkcipher_request_set_crypt(req, sg, sg, ciphertext_len, iv); res = crypto_ablkcipher_encrypt(req); if (res == -EINPROGRESS || res == -EBUSY) { BUG_ON(req->base.data != &ecr); @@ -356,6 +358,7 @@ struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx( if (IS_ERR(ctx)) return ctx; + ctx->flags = ei->i_crypt_policy_flags; if (ctx->has_valid_key) { if (ctx->key.mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) { printk_once(KERN_WARNING @@ -468,6 +471,7 @@ int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx, u32 namelen) { u32 ciphertext_len; + int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK); if (ctx == NULL) return -EIO; @@ -475,6 +479,7 @@ int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx, return -EACCES; ciphertext_len = (namelen < EXT4_CRYPTO_BLOCK_SIZE) ? EXT4_CRYPTO_BLOCK_SIZE : namelen; + ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding); ciphertext_len = (ciphertext_len > ctx->lim) ? ctx->lim : ciphertext_len; return (int) ciphertext_len; @@ -490,10 +495,13 @@ int ext4_fname_crypto_alloc_buffer(struct ext4_fname_crypto_ctx *ctx, u32 ilen, struct ext4_str *crypto_str) { unsigned int olen; + int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK); if (!ctx) return -EIO; - olen = ext4_fname_crypto_round_up(ilen, EXT4_CRYPTO_BLOCK_SIZE); + if (padding < EXT4_CRYPTO_BLOCK_SIZE) + padding = EXT4_CRYPTO_BLOCK_SIZE; + olen = ext4_fname_crypto_round_up(ilen, padding); crypto_str->len = olen; if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2) olen = EXT4_FNAME_CRYPTO_DIGEST_SIZE*2; |