What's Changed

• Block AF_ALG sockets in the default seccomp profile

  AF_ALG (address family 38) exposes the Linux kernel crypto API to userspace
  via socket(2). Containers have no legitimate need for this interface under
  the default profile, and leaving it accessible widens the kernel attack surface
  unnecessarily. See copy.fail for a practical demonstration of AF_ALG
  exploitation to achieve container escape.

  The previous socket rule used a single arg0 != AF_VSOCK condition. Adding a
  second OpNotEqual for AF_ALG does not work because seccomp evaluates multiple
  argument conditions within a single rule as a logical AND against the same
  argument index. Instead, the socket allowlist is restructured into three
  range-based rules that cover every domain except AF_ALG (38) and AF_VSOCK (40):

  1. Allow socket when arg0 < 38 (all families below AF_ALG)
  2. Allow socket when arg0 == 39 (the single family between them)
  3. Allow socket when arg0 > 40 (all families above AF_VSOCK)

  Domains 38 and 40 match none of the three rules and fall through to the
  profile's default SCMP_ACT_ERRNO action.

Full Changelog: seccomp/v0.2.0...seccomp/v0.2.1