2.6.32-longterm review patch. If anyone has any objections, please let me know.
------------------ From: Tyler Hicks <tyhi...@canonical.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 <tyhi...@canonical.com> Reported-by: Kees Cook <keesc...@chromium.org> Reviewed-by: Kees Cook <keesc...@chromium.org> Reviewed-by: John Johansen <john.johan...@canonical.com> Signed-off-by: Colin Ian King <colin.k...@canonical.com> Acked-by: Stefan Bader <stefan.ba...@canonical.com> Signed-off-by: Tim Gardner <tim.gard...@canonical.com> Signed-off-by: Willy Tarreau <w...@1wt.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
