/usr/include/shibsp/attribute/ is in libshibsp-dev 2.6.0+dfsg1-4+deb9u1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/shibsp/attribute/Attribute.h
/usr/include/shibsp/attribute/AttributeDecoder.h
/usr/include/shibsp/attribute/BinaryAttribute.h
/usr/include/shibsp/attribute/ExtensibleAttribute.h
/usr/include/shibsp/attribute/NameIDAttribute.h
/usr/include/shibsp/attribute/ScopedAttribute.h
/usr/include/shibsp/attribute/SimpleAttribute.h
/usr/include/shibsp/attribute/XMLAttribute.h
/usr/include/shibsp/attribute/filtering/
/usr/include/shibsp/attribute/filtering/AttributeFilter.h
/usr/include/shibsp/attribute/filtering/BasicFilteringContext.h
/usr/include/shibsp/attribute/filtering/FilterPolicyContext.h
/usr/include/shibsp/attribute/filtering/FilteringContext.h
/usr/include/shibsp/attribute/filtering/MatchFunctor.h
/usr/include/shibsp/attribute/resolver/
/usr/include/shibsp/attribute/resolver/AttributeExtractor.h
/usr/include/shibsp/attribute/resolver/AttributeResolver.h
/usr/include/shibsp/attribute/resolver/ResolutionContext.h