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From: Mimi Zohar <zohar <at> linux.vnet.ibm.com>
Subject: [PATCH v7 00/16] EVM
Newsgroups: gmane.linux.kernel.lsm
Date: Wednesday 29th June 2011 19:50:22 UTC (over 6 years ago)
Discretionary Access Control(DAC) and Mandatory Access Control(MAC) can
protect the integrity of a running system from unauthorized changes. When
these protections are not running, such as when booting a malicious OS,
mounting the disk under a different operating system, or physically moving
the disk to another system, an "offline" attack is free to read and write
file data/metadata.

Extended Verification Module(EVM) detects offline tampering of the security
extended attributes (e.g. security.selinux, security.SMACK64,
which is the basis for LSM permission decisions and, with the IMA-appraisal
patchset, integrity appraisal decisions. This patchset provides the
and an initial method to detect offline tampering of the security extended
attributes.  The initial method maintains an HMAC-sha1 across a set of
security extended attributes, storing the HMAC as the extended attribute
'security.evm'. To verify the integrity of an extended attribute, EVM
evm_verifyxattr(), which re-calculates the HMAC and compares it with the
version stored in 'security.evm'.  Other methods of validating the
of a file's metadata will be posted separately (eg.

Although an offline attack can bypass DAC/MAC protection mechanisms and
file data/metadata, if the disk, or VM, is subsequently remounted under the
EVM + DAC/MAC (+ IMA-appraisal) protected OS, then the TPM-calculated HMAC
the file's metadata won't be valid.  Therefore, IMA + MAC/DAC + EVM
(+ IMA-appraisal) can protect system integrity online, detect offline
and prevent tampered files from being accessed.

While this patchset does authenticate the security xattrs, and
cryptographically binds them to the inode, coming extensions will bind
directory and inode metadata for more complete protection.  To help
the review and upstreaming process, each extension will be posted
(eg. IMA-appraisal, IMA-digital-signatures (including module checking),
IMA-appraisal-directory).  For a general overview of the proposed Linux
integrity subsystem, refer to Dave Safford's whitepaper:

Much appreciation to Dave Hansen, Serge Hallyn, and Matt Helsley for
reviewing the original patches. 

Changes from v6:
- Changed the security_inode_init_security API to write the security xattr,
  by calling an fs specific callback.
- Moved the evm_inode_post_init() calls, which calculate the EVM xattr,
  each fs to security_inode_init_security.
- Renamed evm_inode_post_init_security() to evm_inode_init_security().
- Renamed the boot parameter evm_mode=' to 'evm='.

Changes from v5:
- defined 'struct evm_ima_xattr_data',
  removed MAX_DIGEST_SIZE and evm_hmac_size definitions
- check for key failures and errors earlier
- other minor changes enumerated in individual patch descriptions

Changes from v4:
- Added evm_inode_post_init calls for: btrfs, gfs2, jffs2, jfs, and xfs.
- Prevent an invalid security.evm xattr from being updated.
- evm_verifyxattr() performance improvement (Dmitry Kasatkin)
- Fixed evm_verify_hmac() to be fail safe (Dmitry Kasatkin)
- Additional naming change generalizations in preparation for other methods
  of integrity authentication. (Dmitry Kasatkin)

Mimi Zohar
David Safford

Dmitry Kasatkin (5):
  evm: add support for different security.evm data types
  evm: crypto hash replaced by shash
  evm: additional parameter to pass integrity cache entry 'iint'
  evm: evm_verify_hmac must not return INTEGRITY_UNKNOWN
  evm: replace hmac_status with evm_status

Mimi Zohar (11):
  security: new security_inode_init_security API adds function callback
  integrity: move ima inode integrity data management
  xattr: define vfs_getxattr_alloc and vfs_xattr_cmp
  evm: re-release
  security: imbed evm calls in security hooks
  evm: evm_inode_post_removexattr
  evm: imbed evm_inode_post_setattr
  evm: add evm_inode_init_security to initialize new files
  evm: call evm_inode_init_security from security_inode_init_security
  evm: permit only valid security.evm xattrs to be updated
  evm: add evm_inode_setattr to prevent updating an invalid

 Documentation/ABI/testing/evm       |   23 ++
 Documentation/kernel-parameters.txt |    6 +
 fs/attr.c                           |    5 +-
 fs/btrfs/xattr.c                    |   52 +++---
 fs/ext2/xattr_security.c            |   34 ++--
 fs/ext3/xattr_security.c            |   36 ++--
 fs/ext4/xattr_security.c            |   36 ++--
 fs/gfs2/inode.c                     |   38 ++--
 fs/jffs2/security.c                 |   37 ++--
 fs/jfs/xattr.c                      |   57 +++---
 fs/ocfs2/xattr.c                    |   38 +++--
 fs/reiserfs/xattr_security.c        |    4 +-
 fs/xattr.c                          |   63 ++++++-
 fs/xfs/linux-2.6/xfs_iops.c         |   39 ++--
 include/linux/evm.h                 |   92 +++++++++
 include/linux/ima.h                 |   13 --
 include/linux/integrity.h           |   38 ++++
 include/linux/security.h            |   17 +-
 include/linux/xattr.h               |   14 ++-
 mm/shmem.c                          |    4 +-
 security/Kconfig                    |    2 +-
 security/Makefile                   |    4 +-
 security/integrity/Kconfig          |    7 +
 security/integrity/Makefile         |   12 +
 security/integrity/evm/Kconfig      |   12 +
 security/integrity/evm/Makefile     |    6 +
 security/integrity/evm/evm.h        |   38 ++++
 security/integrity/evm/evm_crypto.c |  216 ++++++++++++++++++++
 security/integrity/evm/evm_main.c   |  384
 security/integrity/evm/evm_secfs.c  |  108 ++++++++++
 security/integrity/iint.c           |  171 ++++++++++++++++
 security/integrity/ima/Kconfig      |    1 +
 security/integrity/ima/Makefile     |    2 +-
 security/integrity/ima/ima.h        |   29 +--
 security/integrity/ima/ima_api.c    |    7 +-
 security/integrity/ima/ima_iint.c   |  169 ---------------
 security/integrity/ima/ima_main.c   |   12 +-
 security/integrity/integrity.h      |   47 +++++
 security/security.c                 |   71 ++++++-
 39 files changed, 1537 insertions(+), 407 deletions(-)
 create mode 100644 Documentation/ABI/testing/evm
 create mode 100644 include/linux/evm.h
 create mode 100644 include/linux/integrity.h
 create mode 100644 security/integrity/Kconfig
 create mode 100644 security/integrity/Makefile
 create mode 100644 security/integrity/evm/Kconfig
 create mode 100644 security/integrity/evm/Makefile
 create mode 100644 security/integrity/evm/evm.h
 create mode 100644 security/integrity/evm/evm_crypto.c
 create mode 100644 security/integrity/evm/evm_main.c
 create mode 100644 security/integrity/evm/evm_secfs.c
 create mode 100644 security/integrity/iint.c
 delete mode 100644 security/integrity/ima/ima_iint.c
 create mode 100644 security/integrity/integrity.h


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