table of contents
|CAP_ENTER(2)||System Calls Manual||CAP_ENTER(2)|
cap_getmode — Capability
mode system calls
Standard C Library (libc, -lc)
places the current process into capability mode, a mode of execution in
which processes may only issue system calls operating on file descriptors or
reading limited global system state. Access to global name spaces, such as
file system or IPC name spaces, is prevented. If the process is already in a
capability mode sandbox, the system call is a no-op. Future process
descendants created with fork(2) or
pdfork(2) will be placed in capability mode from
When combined with
may be used to create kernel-enforced sandboxes in which
appropriately-crafted applications or application components may be run.
returns a flag indicating whether or not the process is in a capability mode
Creating effective process sandboxes is a tricky process that
involves identifying the least possible rights required by the process and
then passing those rights into the process in a safe manner. Consumers of
cap_enter() should also be aware of other inherited
rights, such as access to VM resources, memory contents, and other process
properties that should be considered. It is advisable to use
fexecve(2) to create a runtime environment inside the
sandbox that has as few implicitly acquired rights as possible.
cap_getmode() functions return the value 0 if
successful; otherwise the value -1 is returned and the global
variable errno is set to indicate the error.
cap_getmode() system calls will fail if:
- The kernel is compiled without:
cap_getmode() system call may also
return the following error:
- Pointer modep points outside the process's allocated address space.
cap_fcntls_limit(2), cap_ioctls_limit(2), cap_rights_limit(2), fexecve(2), cap_sandboxed(3), capsicum(4)
Support for capabilities and capabilities mode was developed as part of the TrustedBSD Project.
These functions and the capability facility were created by Robert N. M. Watson at the University of Cambridge Computer Laboratory with support from a grant from Google, Inc.
|March 27, 2014||Debian|