On 12/16/2011 11:37 AM, Bob Proulx wrote: > Eric Blake wrote: >> Bob Proulx wrote: >>> * The mode bits of a symlink are not used. The original Unix authors >>> ignored them and did not provide any way to change them. >> >> That's true for Linux, but false for BSD (where the mode bits of a >> symlink can allow restriction on dereferencing through the symlink). > > What?! I was not aware of this. I have been too SysV centric for too > many years. And I do not have access to a BSD system in which to > learn about it. > > It would be informative to myself and I expect others if you could > post an example of the behavior from a BSD system showing the > restriction through a symlink's permissions.
Right now, I only had easy access to 64-bit FreeBSD 8.2-RELEASE, and there, the system call lchmod(2) exists, but 'man 7 symlink' states that access permissions are ignored. But I still remember reading about permissions affecting symlinks on at least one BSD variant (I'm still trying to find where I remember that from); something like 'w' permissions were required for readlink(2) to succeed, and 'x' permissions required for open(2) and friends to successfully follow the symlink. I'll post back if I can find more evidence. -- Eric Blake [email protected] +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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