VERIEXEC(8) | System Manager's Manual | VERIEXEC(8)

# NAME

`veriexec` — file integrity subsystem

# DESCRIPTION

Veriexec is an in-kernel, real-time, file-system independent, file integrity subsystem. It can be used for a variety of purposes, including defense against trojaned binaries, indirect attacks via third-party remote file-systems, and malicious configuration file corruption.

# CONFIGURATION

## Signatures Database

Veriexec requires a signatures database -- a list of monitored files, along with their digital fingerprint and (optionally) access modes. The format of this file is described by veriexec(5).

NetBSD provides a tool, veriexecgen(8), for generating the signatures database. Example usage:

    # veriexecgen

Although it should be loaded on system boot (see “RC Configuration” below), this list can be loaded manually using veriexecctl(8):

    # veriexecctl load

## Kernel Configuration

Veriexec requires a kernel with fileassoc(9) support and a pseudo-device to run:

    options FILEASSOC
    pseudo-device veriexec

Additionally, one or more options for digital fingerprint algorithm support:

    options VERIFIED_EXEC_FP_SHA256
    options VERIFIED_EXEC_FP_SHA384
    options VERIFIED_EXEC_FP_SHA512

Some kernels already enable Veriexec by default. See your kernel's config file for more information.

## RC Configuration

Veriexec also allows loading signatures and setting the strict level (see below) during the boot process using the following variables set in rc.conf(5):

    veriexec=YES
    veriexec_strict=1 # IDS mode

# STRICT LEVELS

Veriexec can operate in four modes, also referred to as strict levels:

Learning mode (strict level 0)
  The only level at which the fingerprint tables can be modified, this level is used to help fine-tune the signature database. No enforcement is made, and verbose information is provided (fingerprint matches and mismatches, file removals, incorrect access, etc.).
IDS mode (strict level 1)
  IDS (intrusion detection system) mode provides an adequate level of integrity for the files it monitors. Implications:

  - Monitored files cannot be removed
  - If raw disk access is granted to a disk with monitored files on it, all monitored files' fingerprints will be invalidated
  - Access to files with mismatched fingerprints is denied
  - Write access to monitored files is allowed
  - Access type is not enforced
IPS mode (strict level 2)
  IPS (intrusion prevention system) mode provides a high level of integrity for the files it monitors. Implications:

  - All implications of IDS mode
  - Write access to monitored files is denied
  - Access type is enforced
  - Raw disk access to disk devices with monitored files on them is denied
  - Execution of non-monitored files is denied
  - Write access to kernel memory via /dev/mem and /dev/kmem is denied
Lockdown mode (strict level 3)
  Lockdown mode provides high assurance integrity for the entire system. Implications:

  - All implications of IPS mode
  - Access to non-monitored files is denied
  - Write access to files is allowed only if the file was opened before the strict level was raised to this mode
  - Creation of new files is denied
  - Raw access to system disks is denied

# RUNTIME INFORMATION

Veriexec exports runtime information that may be useful for various purposes.

It reports the currently supported fingerprinting algorithms, for example:

    # /sbin/sysctl kern.veriexec.algorithms
    kern.veriexec.algorithms = SHA256 SHA384 SHA512

It reports the current verbosity and strict levels, for example:

    # /sbin/sysctl kern.veriexec.{verbose,strict}
    kern.veriexec.verbose = 0
    kern.veriexec.strict = 1

It reports a summary of currently loaded files and the mount-points they're on, for example:

    # /sbin/sysctl kern.veriexec.count
    kern.veriexec.count.table0.mntpt = /
    kern.veriexec.count.table0.fstype = ffs
    kern.veriexec.count.table0.nentries = 33

Other information may be retrieved using veriexecctl(8).

# SEE ALSO

options(4), veriexec(5), sysctl(7), sysctl(8), veriexecctl(8), veriexecgen(8)

# AUTHORS

Elad Efrat <elad@NetBSD.org>

September 13, 2017 | NetBSD 11.0