Commits on Nov 19, 2020

1. capng_apply: apply CAPNG_SELECT_CAPS before CAPNG_SELECT_BOUNDS …

   When using capng_apply(CAPNG_SELECT_BOTH), libcap-ng before version 0.8.1
   silently skipped applying bounding capabilities if CAP_SETPCAP was not given
   and continued to apply CAPNG_SELECT_CAPS.
   
   libcap-ng 0.8.1 changed this behaviour in commits
   6a24a9c and
   2ab6a03 to return with an error when trying to
   set bounding capabilities without having CAP_SETPCAP. While this change
   generally is useful to be able to detect more errors, it means that
   capng_apply(CAPNG_SELECT_BOTH) now does not even apply CAPNG_SELECT_CAPS any
   more since the function returns early after failing to apply the bounding
   capabilities.
   
   This change in behaviour might be surprising for legacy code that simply copied
   capng_apply(CAPNG_SELECT_BOTH) from the example code in the README and does not
   check the return value to see whether something went wrong. In this case, no
   capabilities are applied at all any more, which is a breaking change.
   
   Applying CAPNG_SELECT_CAPS before CAPNG_SELECT_BOUNDS means that at least the
   CAPNG_SELECT_CAPS are applied, while still failing with an error of -4 when
   CAPNG_SELECT_BOTH is used without CAP_SETPCAP.
   
   I hope this strikes a balance between the need for better error checking and
   backwards compatibility with legacy code that does not perform any error
   checking on capng_apply, thus silently failing to apply any capabilities at
   all.

   

   diabonas committed Nov 19, 2020
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