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I have implemented portmap spoofing in klibc nfsmount (released as
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klibc-0.144) This is basically a vestigial portmap daemon which gets
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launched before the mount() call and then just records any
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transactions it gets to a file and sends back an affirmative reply.
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There are two ways to use it (this belongs in a README file, but it's
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too late at night right now):
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a) Set a fixed portnumber in /proc/sys/nfs/nlm_tcpport and
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/proc/sys/nfs/nlm_udpport before calling nfsmount; once the portmapper
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starts feed that fixed portnumber to pmap_set(8). In this case the
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pmap_file can be /dev/null.
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b) Allow the kernel to bind to any port and use the file produced by
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nfsroot to feed to pmap_set (it should be directly compatible); this
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means the file needs to be transferred to a place where the "real
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root" can find it before run-init.
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In either case, it is imperative that the real portmapper is launched
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before any program actually tries to create locks!
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# We need the loopback device to be up before we do this!
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ipconfig 127.0.0.1:::::lo:none
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nfsroot -p pmap_file -o lock server:/pathname /realpath
added
removed
usr/kinit/nfsmount/README.locking
