msva-perl(1) Perl implementation of a Monkeysphere Validation Agent


msva-perl [ COMMAND [ ARGS ... ] ]


msva-perl provides a Perl implementation of the Monkeysphere Validation Agent, a certificate validation service.


The Monkeysphere Validation Agent offers a local service for tools to validate certificates (both X.509 and OpenPGP) and other public keys.

Clients of the validation agent query it with a public key carrier (a raw public key, or some flavor of certificate), the supposed name of the remote peer offering the pubkey, and the context in which the validation check is relevant (e.g. ssh, https, etc).

The validation agent then tells the client whether it was able to successfully validate the peer's use of the public key in the given context.


Launched with no arguments, msva-perl simply runs and listens forever.

Launched with arguments, it sets up a listener, spawns a subprocess using the supplied command and arguments, but with the MONKEYSPHERE_VALIDATION_AGENT_SOCKET environment variable set to refer to its listener. When the subprocess terminates, msva-perl tears down the listener and exits as well, returning the same value as the subprocess.

This is a similar invocation pattern to that of ssh-agent(1).


msva-perl is configured by means of environment variables.
msva-perl logs messages about its operation to stderr. MSVA_LOG_LEVEL controls its verbosity, and should be one of (in increasing verbosity): silent, quiet, fatal, error, info, verbose, debug, debug1, debug2, debug3. Default is 'error'.
If your system is capable of it, msva-perl tries to figure out the owner of the connecting client. If MSVA_ALLOWED_USERS is unset, msva-perl will only permit connections from the user msva is running as. If you set MSVA_ALLOWED_USERS, msva-perl will treat it as a list of local users (by name or user ID) who are allowed to connect.
msva-perl listens on a local TCP socket to facilitate access. You can choose what port to bind to by setting MSVA_PORT. Default is to bind on an arbitrary open port.
msva-perl will request information from OpenPGP keyservers. Set MSVA_KEYSERVER to declare the keyserver you want it to check with. If this variable is blank or unset, and your gpg.conf contains a keyserver declaration, it will use the GnuPG configuration. Failing that, the default is 'hkp://'.
msva-perl must decide when to check with keyservers (for new keys, revocation certificates, new certifications, etc). There are three possible options: 'always' means to check with the keyserver on every query it receives. 'never' means to never check with a keyserver. 'unlessvalid' will only check with the keyserver on a specific query if no keys are already locally known to be valid for the requested peer. Default is 'unlessvalid'.
Under graphical environments such as X11, msva-perl is capable of monitoring for changes in its underlying code and can prompt the user to restart the daemon when some of the underlying code changes. Setting this environmnt variable to 'true' enables this monitoring and prompting behavior. Default is 'false'.


Communications with the Monkeysphere Validation Agent are in the form of JSON requests over plain HTTP. Responses from the agent are also JSON objects. For details on the structure of the requests and responses, please see


msva-perl deliberately binds to the IPv4 loopback (on so that remote users do not get access to the daemon. On systems (like Linux) which report ownership of TCP sockets in /proc/net/tcp, msva-perl will refuse access from random users (see MSVA_ALLOWED_USERS above).


Bugs or feature requests for msva-perl should be filed with the Monkeysphere project's bug tracker at


Daniel Kahn Gillmor <[email protected]<gt>

The Monkeysphere Team


Copyright X Daniel Kahn Gillmor and others from the Monkeysphere team. msva-perl is free software, distributed under the GNU Public License, version 3 or later.