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Message-ID: <20121002054655.GA17360@boyd>
Date: Mon, 1 Oct 2012 22:46:56 -0700
From: Tyler Hicks <tyhicks@...onical.com>
To: Willy Tarreau <w@....eu>
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
Colin Ian King <colin.king@...onical.com>,
Stefan Bader <stefan.bader@...onical.com>,
Tim Gardner <tim.gardner@...onical.com>
Subject: Re: [ 026/180] eCryptfs: Improve statfs reporting
On 2012-10-02 00:52:23, Willy Tarreau wrote:
> 2.6.32-longterm review patch. If anyone has any objections, please let me know.
Hi - Please drop this patch. It incorrectly calculates f_namelen and I
haven't had a chance to fix it yet. When I get a fix ready, I'll forward
the corrected patch to stable@....o. Thanks!
Tyler
>
> ------------------
>
> From: Tyler Hicks <tyhicks@...onical.com>
>
> commit 4a26620df451ad46151ad21d711ed43e963c004e upstream.
>
> BugLink: http://bugs.launchpad.net/bugs/885744
>
> statfs() calls on eCryptfs files returned the wrong filesystem type and,
> when using filename encryption, the wrong maximum filename length.
>
> If mount-wide filename encryption is enabled, the cipher block size and
> the lower filesystem's max filename length will determine the max
> eCryptfs filename length. Pre-tested, known good lengths are used when
> the lower filesystem's namelen is 255 and a cipher with 8 or 16 byte
> block sizes is used. In other, less common cases, we fall back to a safe
> rounded-down estimate when determining the eCryptfs namelen.
>
> https://launchpad.net/bugs/885744
>
> Signed-off-by: Tyler Hicks <tyhicks@...onical.com>
> Reported-by: Kees Cook <keescook@...omium.org>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> Reviewed-by: John Johansen <john.johansen@...onical.com>
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> Acked-by: Stefan Bader <stefan.bader@...onical.com>
> Signed-off-by: Tim Gardner <tim.gardner@...onical.com>
> Signed-off-by: Willy Tarreau <w@....eu>
> ---
> fs/ecryptfs/crypto.c | 68 ++++++++++++++++++++++++++++++++++++----
> fs/ecryptfs/ecryptfs_kernel.h | 11 ++++++
> fs/ecryptfs/keystore.c | 9 ++---
> fs/ecryptfs/super.c | 18 ++++++++++-
> 4 files changed, 92 insertions(+), 14 deletions(-)
>
> diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
> index 7e164bb..7786bf6 100644
> --- a/fs/ecryptfs/crypto.c
> +++ b/fs/ecryptfs/crypto.c
> @@ -2039,6 +2039,17 @@ out:
> return;
> }
>
> +static size_t ecryptfs_max_decoded_size(size_t encoded_size)
> +{
> + /* Not exact; conservatively long. Every block of 4
> + * encoded characters decodes into a block of 3
> + * decoded characters. This segment of code provides
> + * the caller with the maximum amount of allocated
> + * space that @dst will need to point to in a
> + * subsequent call. */
> + return ((encoded_size + 1) * 3) / 4;
> +}
> +
> /**
> * ecryptfs_decode_from_filename
> * @dst: If NULL, this function only sets @dst_size and returns. If
> @@ -2057,13 +2068,7 @@ ecryptfs_decode_from_filename(unsigned char *dst, size_t *dst_size,
> size_t dst_byte_offset = 0;
>
> if (dst == NULL) {
> - /* Not exact; conservatively long. Every block of 4
> - * encoded characters decodes into a block of 3
> - * decoded characters. This segment of code provides
> - * the caller with the maximum amount of allocated
> - * space that @dst will need to point to in a
> - * subsequent call. */
> - (*dst_size) = (((src_size + 1) * 3) / 4);
> + (*dst_size) = ecryptfs_max_decoded_size(src_size);
> goto out;
> }
> while (src_byte_offset < src_size) {
> @@ -2289,3 +2294,52 @@ out_free:
> out:
> return rc;
> }
> +
> +#define ENC_NAME_MAX_BLOCKLEN_8_OR_16 143
> +
> +int ecryptfs_set_f_namelen(long *namelen, long lower_namelen,
> + struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
> +{
> + struct blkcipher_desc desc;
> + struct mutex *tfm_mutex;
> + size_t cipher_blocksize;
> + int rc;
> +
> + if (!(mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
> + (*namelen) = lower_namelen;
> + return 0;
> + }
> +
> + rc = ecryptfs_get_tfm_and_mutex_for_cipher_name(&desc.tfm, &tfm_mutex,
> + mount_crypt_stat->global_default_fn_cipher_name);
> + if (unlikely(rc)) {
> + (*namelen) = 0;
> + return rc;
> + }
> +
> + mutex_lock(tfm_mutex);
> + cipher_blocksize = crypto_blkcipher_blocksize(desc.tfm);
> + mutex_unlock(tfm_mutex);
> +
> + /* Return an exact amount for the common cases */
> + if (lower_namelen == NAME_MAX
> + && (cipher_blocksize == 8 || cipher_blocksize == 16)) {
> + (*namelen) = ENC_NAME_MAX_BLOCKLEN_8_OR_16;
> + return 0;
> + }
> +
> + /* Return a safe estimate for the uncommon cases */
> + (*namelen) = lower_namelen;
> + (*namelen) -= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
> + /* Since this is the max decoded size, subtract 1 "decoded block" len */
> + (*namelen) = ecryptfs_max_decoded_size(*namelen) - 3;
> + (*namelen) -= ECRYPTFS_TAG_70_MAX_METADATA_SIZE;
> + (*namelen) -= ECRYPTFS_FILENAME_MIN_RANDOM_PREPEND_BYTES;
> + /* Worst case is that the filename is padded nearly a full block size */
> + (*namelen) -= cipher_blocksize - 1;
> +
> + if ((*namelen) < 0)
> + (*namelen) = 0;
> +
> + return 0;
> +}
> diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
> index 9685315..4181136 100644
> --- a/fs/ecryptfs/ecryptfs_kernel.h
> +++ b/fs/ecryptfs/ecryptfs_kernel.h
> @@ -219,12 +219,21 @@ ecryptfs_get_key_payload_data(struct key *key)
> * dentry name */
> #define ECRYPTFS_TAG_73_PACKET_TYPE 0x49 /* FEK-encrypted filename as
> * metadata */
> +#define ECRYPTFS_MIN_PKT_LEN_SIZE 1 /* Min size to specify packet length */
> +#define ECRYPTFS_MAX_PKT_LEN_SIZE 2 /* Pass at least this many bytes to
> + * ecryptfs_parse_packet_length() and
> + * ecryptfs_write_packet_length()
> + */
> /* Constraint: ECRYPTFS_FILENAME_MIN_RANDOM_PREPEND_BYTES >=
> * ECRYPTFS_MAX_IV_BYTES */
> #define ECRYPTFS_FILENAME_MIN_RANDOM_PREPEND_BYTES 16
> #define ECRYPTFS_NON_NULL 0x42 /* A reasonable substitute for NULL */
> #define MD5_DIGEST_SIZE 16
> #define ECRYPTFS_TAG_70_DIGEST_SIZE MD5_DIGEST_SIZE
> +#define ECRYPTFS_TAG_70_MIN_METADATA_SIZE (1 + ECRYPTFS_MIN_PKT_LEN_SIZE \
> + + ECRYPTFS_SIG_SIZE + 1 + 1)
> +#define ECRYPTFS_TAG_70_MAX_METADATA_SIZE (1 + ECRYPTFS_MAX_PKT_LEN_SIZE \
> + + ECRYPTFS_SIG_SIZE + 1 + 1)
> #define ECRYPTFS_FEK_ENCRYPTED_FILENAME_PREFIX "ECRYPTFS_FEK_ENCRYPTED."
> #define ECRYPTFS_FEK_ENCRYPTED_FILENAME_PREFIX_SIZE 23
> #define ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX "ECRYPTFS_FNEK_ENCRYPTED."
> @@ -762,6 +771,8 @@ ecryptfs_parse_tag_70_packet(char **filename, size_t *filename_size,
> size_t *packet_size,
> struct ecryptfs_mount_crypt_stat *mount_crypt_stat,
> char *data, size_t max_packet_size);
> +int ecryptfs_set_f_namelen(long *namelen, long lower_namelen,
> + struct ecryptfs_mount_crypt_stat *mount_crypt_stat);
> int ecryptfs_derive_iv(char *iv, struct ecryptfs_crypt_stat *crypt_stat,
> loff_t offset);
>
> diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
> index 8f1a525..4f1feeb 100644
> --- a/fs/ecryptfs/keystore.c
> +++ b/fs/ecryptfs/keystore.c
> @@ -548,10 +548,7 @@ ecryptfs_write_tag_70_packet(char *dest, size_t *remaining_bytes,
> * Octets N3-N4: Block-aligned encrypted filename
> * - Consists of a minimum number of random characters, a \0
> * separator, and then the filename */
> - s->max_packet_size = (1 /* Tag 70 identifier */
> - + 3 /* Max Tag 70 packet size */
> - + ECRYPTFS_SIG_SIZE /* FNEK sig */
> - + 1 /* Cipher identifier */
> + s->max_packet_size = (ECRYPTFS_TAG_70_MAX_METADATA_SIZE
> + s->block_aligned_filename_size);
> if (dest == NULL) {
> (*packet_size) = s->max_packet_size;
> @@ -806,10 +803,10 @@ ecryptfs_parse_tag_70_packet(char **filename, size_t *filename_size,
> goto out;
> }
> s->desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;
> - if (max_packet_size < (1 + 1 + ECRYPTFS_SIG_SIZE + 1 + 1)) {
> + if (max_packet_size < ECRYPTFS_TAG_70_MIN_METADATA_SIZE) {
> printk(KERN_WARNING "%s: max_packet_size is [%zd]; it must be "
> "at least [%d]\n", __func__, max_packet_size,
> - (1 + 1 + ECRYPTFS_SIG_SIZE + 1 + 1));
> + ECRYPTFS_TAG_70_MIN_METADATA_SIZE);
> rc = -EINVAL;
> goto out;
> }
> diff --git a/fs/ecryptfs/super.c b/fs/ecryptfs/super.c
> index 1a037f7..557469a 100644
> --- a/fs/ecryptfs/super.c
> +++ b/fs/ecryptfs/super.c
> @@ -30,6 +30,8 @@
> #include <linux/smp_lock.h>
> #include <linux/file.h>
> #include <linux/crypto.h>
> +#include <linux/statfs.h>
> +#include <linux/magic.h>
> #include "ecryptfs_kernel.h"
>
> struct kmem_cache *ecryptfs_inode_info_cache;
> @@ -137,7 +139,21 @@ static void ecryptfs_put_super(struct super_block *sb)
> */
> static int ecryptfs_statfs(struct dentry *dentry, struct kstatfs *buf)
> {
> - return vfs_statfs(ecryptfs_dentry_to_lower(dentry), buf);
> + struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
> + int rc;
> +
> + if (!lower_dentry->d_sb->s_op->statfs)
> + return -ENOSYS;
> +
> + rc = lower_dentry->d_sb->s_op->statfs(lower_dentry, buf);
> + if (rc)
> + return rc;
> +
> + buf->f_type = ECRYPTFS_SUPER_MAGIC;
> + rc = ecryptfs_set_f_namelen(&buf->f_namelen, buf->f_namelen,
> + &ecryptfs_superblock_to_private(dentry->d_sb)->mount_crypt_stat);
> +
> + return rc;
> }
>
> /**
> --
> 1.7.2.1.45.g54fbc
>
>
>
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