.TH SIGN 3 .SH NAME sign \- control use of signed modules .SH SYNOPSIS .B "bind -a #Σ /dev" .PP .B /dev/signerkey .br .B /dev/signctl .SH DESCRIPTION .I Sign is a device, still experimental, to control the use of signed Dis modules. After system initialisation, any process can load any module. Using .IR sign , .B load operations can subsequently be restricted for a process and its descendents. .PP .B Signerkey is a file that can be opened for writing only by the host owner (see .IR 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 .B Keyring->pktostr (see .IR keyring-certtostr (2)). After a successful write, subsequent .B load operations will be limited to Dis modules in any of the following sets: .IP • built-in modules .IP • unsigned modules found in the kernel's .IR root (3) file system .IP • currently loaded unsigned modules .IP • acceptable signed modules .PP A signed Dis module contains a signature in its header, as specified by .IR 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 .BR Keyring->sign , see .IR keyring-sha1 (2)). .PP A signed module is `acceptable' if it was signed by the secret key corresponding to one of the public keys written to .BR signerkey . There can be up to 8 such keys. The set of keys and the secured status is shared across .BR spawn . .PP .B Signerkey is generally readable, and when read yields a list of the keys installed, one per line, showing .BR owner , .BR alg , and other attributes in .IB attr = value format, space separated. The actual key value is not currently shown. .PP .B 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. .SH SOURCE .B /emu/port/devsign.c .br .B /os/port/devsign.c .SH SEE ALSO .B wm/rt in .IR wm-misc (2), .IR sys-pctl (2), .IR dis (6), .IR createsignerkey (8), .IR eve (10.2) .SH DIAGNOSTICS If the text is not a valid public key or uses an algorithm that is not configured, a write to .B signer fails and sets the error string.