posix1e(3) on FreeBSD
The text 24ad16c0f466, as FreeBSD 6.3-RELEASE, FreeBSD 6.2-RELEASE, FreeBSD 6.1-RELEASE, FreeBSD 6.0-RELEASE, FreeBSD 5.5-RELEASE, FreeBSD 5.4-RELEASE, FreeBSD 5.3-RELEASE, FreeBSD 5.2.1-RELEASE, FreeBSD 5.2-RELEASE, FreeBSD 5.1-RELEASE shipped it.
introduction to the POSIX.1e security API