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authorEdward Shishkin <>2013-03-13 21:56:46 +0100
committerAnand Avati <>2013-11-13 15:12:49 -0800
commit4efbff29e773a8c59605f87bc3939c9c71b9da16 (patch)
tree3f0ac8f9c628de459a6c1fdc4f00415e4f9d743e /
parent98e796e50198945adc660e42f3f5ab5b668f7bba (diff)
Transparent data encryption and metadata authentication
.. in the systems with non-trusted server This new functionality can be useful in various cloud technologies. It is implemented via a special encryption/crypt translator,which works on the client side and performs encryption and authentication; 1. Class of supported algorithms The crypt translator can support any atomic symmetric block cipher algorithms (which require to pad plain/cipher text before performing encryption/decryption transform (see glossary in atom.c for definitions). In particular, it can support algorithms with the EOF issue (which require to pad the end of file by extra-data). Crypt translator performs translations user -> (offset, size) -> (aligned-offset, padded-size) ->server (and backward), and resolves individual FOPs (write(), truncate(), etc) to read-modify-write sequences. A volume can contain files encrypted by different algorithms of the mentioned class. To change some option value just reconfigure the volume. Currently only one algorithm is supported: AES_XTS. Example of algorithms, which can not be supported by the crypt translator: 1. Asymmetric block cipher algorithms, which inflate data, e.g. RSA; 2. Symmetric block cipher algorithms with inline MACs for data authentication. 2. Implementation notes. a) Atomic algorithms Since any process in a stackable file system manipulates with local data (which can be obsoleted by local data of another process), any atomic cipher algorithm without proper support can lead to non-POSIX behavior. To resolve the "collisions" we introduce locks: before performing FOP->read(), FOP->write(), etc. the process should first lock the file. b) Algorithms with EOF issue Such algorithms require to pad the end of file with some extra-data. Without proper support this will result in losing information about real file size. Keeping a track of real file size is a responsibility of the crypt translator. A special extended attribute with the name "trusted.glusterfs.crypt.att.size" is used for this purpose. All files contained in bricks of encrypted volume do have "padded" sizes. 3. Non-trusted servers and Metadata authentication We assume that server, where user's data is stored on is non-trusted. It means that the server can be subjected to various attacks directed to reveal user's encrypted personal data. We provide protection against such attacks. Every encrypted file has specific private attributes (cipher algorithm id, atom size, etc), which are packed to a string (so-called "format string") and stored as a special extended attribute with the name "trusted.glusterfs.crypt.att.cfmt". We protect the string from tampering. This protection is mandatory, hardcoded and is always on. Without such protection various attacks (based on extending the scope of per-file secret keys) are possible. Our authentication method has been developed in tight collaboration with Red Hat security team and is implemented as "metadata loader of version 1" (see file metadata.c). This method is NIST-compliant and is based on checking 8-byte per-hardlink MACs created(updated) by FOP->create(), FOP->link(), FOP->unlink(), FOP->rename() by the following unique entities: . file (hardlink) name; . verified file's object id (gfid). Every time, before manipulating with a file, we check it's MACs at FOP->open() time. Some FOPs don't require a file to be opened (e.g. FOP->truncate()). In such cases the crypt translator opens the file mandatory. 4. Generating keys Unique per-file keys are derived by NIST-compliant methods from the a) parent key; b) unique verified object-id of the file (gfid); Per-volume master key, provided by user at mount time is in the root of this "tree of keys". Those keys are used to: 1) encrypt/decrypt file data; 2) encrypt/decrypt file metadata; 3) create per-file and per-link MACs for metadata authentication. 5. Instructions Getting started with crypt translator Example: 1) Create a volume "myvol" and enable encryption: # gluster volume create myvol pepelac:/vols/xvol # gluster volume set myvol encryption on 2) Set location (absolute pathname) of your master key: # gluster volume set myvol encryption.master-key /home/me/mykey 3) Set other options to override default options, if needed. Start the volume. 4) On the client side make sure that the file /home/me/mykey exists and contains proper per-volume master key (that is 256-bit AES key). This key has to be in hex form, i.e. should be represented by 64 symbols from the set {'0', ..., '9', 'a', ..., 'f'}. The key should start at the beginning of the file. All symbols at offsets >= 64 are ignored. 5) Mount the volume "myvol" on the client side: # glusterfs --volfile-server=pepelac --volfile-id=myvol /mnt After successful mount the file which contains master key may be removed. NOTE: Keeping the master key between mount sessions is in user's competence. ********************************************************************** WARNING! Losing the master key will make content of all regular files inaccessible. Mount with improper master key allows to access content of directories: file names are not encrypted. ********************************************************************** 6. Options of crypt translator 1) "master-key": specifies location (absolute pathname) of the file which contains per-volume master key. There is no default location for master key. 2) "data-key-size": specifies size of per-file key for data encryption Possible values: . "256" default value . "512" 3) "block-size": specifies atom size. Possible values: . "512" . "1024" . "2048" . "4096" default value; 7. Test cases Any workload, which involves the following file operations: ->create(); ->open(); ->readv(); ->writev(); ->truncate(); ->ftruncate(); ->link(); ->unlink(); ->rename(); ->readdirp(). 8. TODOs: 1) Currently size of IOs issued by crypt translator is restricted by block_size (4K by default). We can use larger IOs to improve performance. Change-Id: I2601fe95c5c4dc5b22308a53d0cbdc071d5e5cee BUG: 1030058 Signed-off-by: Edward Shishkin <> Signed-off-by: Anand Avati <> Reviewed-on: Tested-by: Gluster Build System <>
Diffstat (limited to '')
1 files changed, 23 insertions, 0 deletions
diff --git a/ b/
index 0cecafb..b3d1ed1 100644
--- a/
+++ b/
@@ -131,6 +131,8 @@ AC_CONFIG_FILES([Makefile
+ xlators/encryption/crypt/Makefile
+ xlators/encryption/crypt/src/Makefile
@@ -340,6 +342,26 @@ fi
+# start encryption/crypt section
+AC_CHECK_HEADERS([openssl/cmac.h], [have_cmac_h=yes], [have_cmac_h=no])
+ AC_HELP_STRING([--enable-crypt-xlator], [Build crypt encryption xlator]))
+if test "x$enable_crypt_xlator" = "xyes" -a "x$have_cmac_h" = "xno"; then
+ echo "Encryption xlator requires OpenSSL with cmac.h"
+ exit 1
+if test "x$enable_crypt_xlator" != "xno" -a "x$have_cmac_h" = "xyes"; then
+ AC_DEFINE(HAVE_CRYPT_XLATOR, 1, [enable building crypt encryption xlator])
# end FUSE section
@@ -865,4 +887,5 @@ echo "glupy : $BUILD_GLUPY"
echo "Use syslog : $USE_SYSLOG"
echo "XML output : $BUILD_XML_OUTPUT"
echo "QEMU Block formats : $BUILD_QEMU_BLOCK"
+echo "Encryption xlator : $BUILD_CRYPT_XLATOR"