> What is the proposed semantic of O_BENEATH with absolute paths -- I > believe you don't have an openat(2) on FreeBSD (but please feel free to > correct me)?
openat(2) is necessary for capability mode (since open(2) is not permitted), but it turns out it was actually added to FreeBSD earlier than that - the work was done by a student in the 2007 Google Summer of Code. >From the proposed man page change: | If the specified path is absolute, O_BENEATH | allows arbitrary prefix that ends up in the starting directory, | after which all further resolved components must be under it. For open, and openat(AT_FDCWD), cwd is used as the top / starting directory. Once the absolute path traverses the "top" directory in namei all components must remain within. The proposed patch allows paths that perhaps enter, exit, and re-enter the hierarchy -- for example, if /a/b is the top then /c/d/../../a/b/file would be allowed. (If you're interested in taking a look the proposed change is available at https://reviews.freebsd.org/D17714 ) In capability mode absolute paths will always be disallowed.
