/usr/include/SFCGAL/detail/ is in libsfcgal-dev 1.3.0-4+b2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/SFCGAL/detail/ComplexComparator.h
/usr/include/SFCGAL/detail/EnvelopeVisitor.h
/usr/include/SFCGAL/detail/ForceValidityVisitor.h
/usr/include/SFCGAL/detail/GeometrySet.h
/usr/include/SFCGAL/detail/GetPointsVisitor.h
/usr/include/SFCGAL/detail/Interval.h
/usr/include/SFCGAL/detail/Point_inside_polyhedron.h
/usr/include/SFCGAL/detail/TestGeometry.h
/usr/include/SFCGAL/detail/TypeForDimension.h
/usr/include/SFCGAL/detail/algorithm/
/usr/include/SFCGAL/detail/algorithm/coversPoints.h
/usr/include/SFCGAL/detail/generator/
/usr/include/SFCGAL/detail/generator/building.h
/usr/include/SFCGAL/detail/generator/disc.h
/usr/include/SFCGAL/detail/generator/hoch.h
/usr/include/SFCGAL/detail/generator/sierpinski.h
/usr/include/SFCGAL/detail/graph/
/usr/include/SFCGAL/detail/graph/Edge.h
/usr/include/SFCGAL/detail/graph/GeometryGraph.h
/usr/include/SFCGAL/detail/graph/GeometryGraphBuilder.h
/usr/include/SFCGAL/detail/graph/Vertex.h
/usr/include/SFCGAL/detail/graph/algorithm/
/usr/include/SFCGAL/detail/graph/algorithm/isHalfEdge.h
/usr/include/SFCGAL/detail/graph/algorithm/orientation.h
/usr/include/SFCGAL/detail/io/
/usr/include/SFCGAL/detail/io/OsgFactory.h
/usr/include/SFCGAL/detail/io/Serialization.h
/usr/include/SFCGAL/detail/io/WktReader.h
/usr/include/SFCGAL/detail/io/WktWriter.h
/usr/include/SFCGAL/detail/polygonSetToMultiPolygon.h
/usr/include/SFCGAL/detail/tools/
/usr/include/SFCGAL/detail/tools/CharArrayBuffer.h
/usr/include/SFCGAL/detail/tools/InputStreamReader.h
/usr/include/SFCGAL/detail/tools/Log.h
/usr/include/SFCGAL/detail/tools/Registry.h
/usr/include/SFCGAL/detail/transform/
/usr/include/SFCGAL/detail/transform/AffineTransform2.h
/usr/include/SFCGAL/detail/transform/AffineTransform3.h
/usr/include/SFCGAL/detail/transform/Force2D.h
/usr/include/SFCGAL/detail/transform/ForceOrderPoints.h
/usr/include/SFCGAL/detail/transform/ForceZ.h
/usr/include/SFCGAL/detail/transform/ForceZOrderPoints.h
/usr/include/SFCGAL/detail/transform/RoundTransform.h
/usr/include/SFCGAL/detail/triangulate/
/usr/include/SFCGAL/detail/triangulate/ConstraintDelaunayTriangulation.h
/usr/include/SFCGAL/detail/triangulate/markDomains.h
/usr/include/SFCGAL/detail/triangulate/triangulateInGeometrySet.h
/usr/include/SFCGAL/detail/ublas.h