seccomp_export_bpf(3)

NAME
seccomp_export_bpf, seccomp_export_pfc - Export the seccomp filter

SYNOPSIS
#include <seccomp.h>

typedef void * scmp_filter_ctx;

int seccomp_export_bpf(const scmp_filter_ctx ctx, int fd);
int seccomp_export_pfc(const scmp_filter_ctx ctx, int fd);
int seccomp_export_bpf_mem(const scmp_filter_ctx ctx, void *buf, size_t *len);

Link with -lseccomp.

DESCRIPTION

The seccomp_export_bpf() and seccomp_export_pfc() functions generate and output the current seccomp filter in either BPF (Berkeley Packet Filter) or PFC (Pseudo Filter Code). The output of seccomp_export_bpf() is suitable for loading into the kernel, while the output of seccomp_export_pfc() is human readable and is intended primarily as a debugging tool for developers using libseccomp. Both functions write the filter to the fd file descriptor.

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

While the two output formats are guaranteed to be functionally equivalent for the given seccomp filter configuration, the filter instructions, and their ordering, are not guaranteed to be the same in both the BPF and PFC formats.

The seccomp_export_bpf_mem() function is largely the same as seccomp_export_bpf(), but instead of writing to a file descriptor, the program will be written to the buf pointer provided by the caller. The len argument must be initialized with the size of the buf buffer. If the program was valid, len will be updated with its size in bytes. If buf was too small to hold the program, len can be consulted to determine the required size. Passing a NULL buf may also be used to query the required size ahead of time.

RETURN VALUE
Return zero on success or one of the following error codes on failure:

-ECANCELED
    There was a system failure beyond the control of the library.

-EFAULT
    Internal libseccomp failure.

-EINVAL
    Invalid input, either the context or architecture token is invalid.

-ENOMEM
    The library was unable to allocate enough memory.

-ERANGE
    The provided buffer was too small.

If the SCMP_FLTATR_API_SYSRAWRC filter attribute is non-zero then additional error codes may be returned to the caller; these additional error codes are the negative errno values returned by the system. Unfortunately libseccomp can make no guarantees about these return values.

EXAMPLES
#include <seccomp.h>
int main(int argc, char *argv[])
{
	int rc = -1;
	scmp_filter_ctx ctx;
	int filter_fd;
	ctx = seccomp_init(SCMP_ACT_KILL);
	if (ctx == NULL)
		goto out;
	/* ... */
	filter_fd = open("/tmp/seccomp_filter.bpf", O_WRONLY);
	if (filter_fd == -1) {
		rc = -errno;
		goto out;
	}
	rc = seccomp_export_bpf(ctx, filter_fd);
	if (rc < 0) {
		close(filter_fd);
		goto out;
	}
	close(filter_fd);
	/* ... */
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>

SEE ALSO
seccomp_init(3), seccomp_release(3)