lighttpd fails to start for a non-root user with gid 0
Trying to start lighttpd as a non-root user in the wheel group fails with "Are you nuts ? Don't apply a SUID bit to this binary" despite the binary not being SUID.
The problem seems to be that on line 345 of server.c
i_am_root = (getuid() 0) and doesn't take into consideration gid. This means that on line 422 of that same file
(!i_am_root && (geteuid() 0 || getegid() == 0)) is true and it is assumed that we are setuid, when in fact the binary is not and it is simply the case that the user is in wheel group.
#1 Updated by Anonymous over 7 years ago
Under Solaris and the BSDs, the issetugid(2) system call can be used to check for setuid/setgid binaries.
There's a patch by Robert Connolly from Linux From Scratch written for glibc to add issetugid(2) which could be appropriated here.
At the very least, rather than
(!i_am_root && (geteuid() == 0 || getegid() == 0))
lighttpd could use
(!i_am_root && (geteuid() != getuid() || getegid() != getgid() ))
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