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sign - control use of signed modules


bind -a #Σ /dev



Sign is a device, still experimental, to control the use of signed Dis modules. After system initialisation, any process can load any module. Using sign, load operations can subsequently be restricted for a process and its descendents.

Signerkey is a file that can be opened for writing only by the host owner (see eve(10.2)) (but any process holding the file descriptor can write to it). The data written must be the textual representation of a public key in the form produced by Keyring->pktostr (see keyring-certtostr(2)). After a successful write, subsequent load operations will be limited to Dis modules in any of the following sets:

built-in modules

unsigned modules found in the kernel's root(3) file system

currently loaded unsigned modules

acceptable signed modules

A signed Dis module contains a signature in its header, as specified by dis(6). The signature contains the result of signing the remaining data in the file (or more precisely, a cryptographically secure hash of it), using a configured public key algorithm and the signer's secret key (for instance using Keyring->sign, see keyring-sha1(2)).

A signed module is `acceptable' if it was signed by the secret key corresponding to one of the public keys written to signerkey. There can be up to 8 such keys. The set of keys and the secured status is shared across spawn.

Signerkey is generally readable, and when read yields a list of the keys installed, one per line, showing owner, alg, and other attributes in attr=value format, space separated. The actual key value is not currently shown.

Signctl can be read or written only by the host owner. Each write contains a textual control request. (Currently there are none such.) If security is not enabled, it is empty when read. Otherwise, it contains the number of keys loaded, as a decimal integer.




wm/rt in wm-misc(2), sys-pctl(2), dis(6), createsignerkey(8), eve(10.2)


If the text is not a valid public key or uses an algorithm that is not configured, a write to signer fails and sets the error string.

SIGN(3 ) Rev:  Thu Feb 15 14:43:36 GMT 2007