NAME

seccomp_attr_set, seccomp_attr_get - Manage the seccomp filter attributes

SYNOPSIS

#include <seccomp.h>

typedef void * scmp_filter_ctx;
enum scmp_filter_attr;

int seccomp_attr_set(scmp_filter_ctx ctx,
                     enum scmp_filter_attr attr, uint32_t value);
int seccomp_attr_get(scmp_filter_ctx ctx,
                     enum scmp_filter_attr attr, uint32_t *value);

Link with -lseccomp.

DESCRIPTION

The seccomp_attr_set() function sets the different seccomp filter attributes while the seccomp_attr_get() function fetches the filter attributes. The seccomp filter attributes are tunable values that affect how the library behaves when generating and loading the seccomp filter into the kernel. The attributes are reset to their default values whenever the filter is initialized or reset via seccomp_filter_init(3) or seccomp_filter_reset(3).

The filter context ctx is the value returned by the call to seccomp_init(3).

Valid attr values are as follows:

SCMP_FLTATR_ACT_DEFAULT: The default filter action as specified in the call to seccomp_filter_init(3) or seccomp_filter_reset(3). This attribute is read-only.
SCMP_FLTATR_ACT_BADARCH: The filter action taken when the loaded filter does not match the architecture of the executing application. Defaults to the SCMP_ACT_KILL action.
SCMP_FLTATR_CTL_NNP: A flag to specify if the NO_NEW_PRIVS functionality should be enabled before loading the seccomp filter into the kernel. If set to off ( value == 0) then loading the seccomp filter into the kernel will fail if CAP_SYS_ADMIN is not set. Defaults to on ( value == 1).
SCMP_FLTATR_CTL_TSYNC: A flag to specify if the kernel should attempt to synchronize the filters across all threads on seccomp_load(3). If the kernel is unable to synchronize all of the thread then the load operation will fail. This flag is only available on Linux Kernel 3.17 or greater; attempting to enable this flag on earlier kernels will result in an error being returned. Defaults to off ( value == 0).
SCMP_FLTATR_ATL_TSKIP: A flag to specify if libseccomp should allow filter rules to be created for the -1 syscall. The -1 syscall value can be used by tracer programs to skip specific syscall invocations, see seccomp(2) for more information. Defaults to off ( value == 0).

RETURN VALUE

Returns zero on success, negative errno values on failure.

EXAMPLES

#include <seccomp.h>
int main(int argc, char *argv[])
{
	int rc = -1;
	scmp_filter_ctx ctx;
	ctx = seccomp_init(SCMP_ACT_ALLOW);
	if (ctx == NULL)
		goto out;
	/* ... */
	rc = seccomp_attr_set(ctx, SCMP_FLTATR_ACT_BADARCH, SCMP_ACT_TRAP);
	if (rc < 0)
		goto out;
	/* ... */
out:
	seccomp_release(ctx);
	return -rc;
}

NOTES

While the seccomp filter can be generated independent of the kernel, kernel support is required to load and enforce the seccomp filter generated by libseccomp.

The libseccomp project site, with more information and the source code repository, can be found at https://github.com/seccomp/libseccomp. This tool, as well as the libseccomp library, is currently under development, please report any bugs at the project site or directly to the author.

AUTHOR

Paul Moore <paul@paul-moore.com>