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| author | Theodore Ts'o <tytso@mit.edu> | 2015-05-01 16:56:50 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2015-05-01 16:56:50 -0400 |
| commit | a44cd7a05496d60fd2ba8cca080e3db8f481549b (patch) | |
| tree | dd8d05d845817e4a429804d8ffe09dd68b6881e6 /fs/ext4/crypto_policy.c | |
| parent | 5de0b4d0cd153c471640b13aae6ae6d18d0a4603 (diff) | |
| download | linux-a44cd7a05496d60fd2ba8cca080e3db8f481549b.tar.bz2 | |
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_policy.c')
| -rw-r--r-- | fs/ext4/crypto_policy.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/fs/ext4/crypto_policy.c b/fs/ext4/crypto_policy.c index 30eaf9e9864a..a6d6291aea16 100644 --- a/fs/ext4/crypto_policy.c +++ b/fs/ext4/crypto_policy.c @@ -37,6 +37,8 @@ static int ext4_is_encryption_context_consistent_with_policy( return 0; return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor, EXT4_KEY_DESCRIPTOR_SIZE) == 0 && + (ctx.flags == + policy->flags) && (ctx.contents_encryption_mode == policy->contents_encryption_mode) && (ctx.filenames_encryption_mode == @@ -56,25 +58,25 @@ static int ext4_create_encryption_context_from_policy( printk(KERN_WARNING "%s: Invalid contents encryption mode %d\n", __func__, policy->contents_encryption_mode); - res = -EINVAL; - goto out; + return -EINVAL; } if (!ext4_valid_filenames_enc_mode(policy->filenames_encryption_mode)) { printk(KERN_WARNING "%s: Invalid filenames encryption mode %d\n", __func__, policy->filenames_encryption_mode); - res = -EINVAL; - goto out; + return -EINVAL; } + if (policy->flags & ~EXT4_POLICY_FLAGS_VALID) + return -EINVAL; ctx.contents_encryption_mode = policy->contents_encryption_mode; ctx.filenames_encryption_mode = policy->filenames_encryption_mode; + ctx.flags = policy->flags; BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE); get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE); res = ext4_xattr_set(inode, EXT4_XATTR_INDEX_ENCRYPTION, EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx, sizeof(ctx), 0); -out: if (!res) ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT); return res; @@ -115,6 +117,7 @@ int ext4_get_policy(struct inode *inode, struct ext4_encryption_policy *policy) policy->version = 0; policy->contents_encryption_mode = ctx.contents_encryption_mode; policy->filenames_encryption_mode = ctx.filenames_encryption_mode; + policy->flags = ctx.flags; memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor, EXT4_KEY_DESCRIPTOR_SIZE); return 0; @@ -176,6 +179,7 @@ int ext4_inherit_context(struct inode *parent, struct inode *child) EXT4_ENCRYPTION_MODE_AES_256_XTS; ctx.filenames_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_CTS; + ctx.flags = 0; memset(ctx.master_key_descriptor, 0x42, EXT4_KEY_DESCRIPTOR_SIZE); res = 0; |