/usr/share/gromacs/top/charmm27.ff/rna.c.tdb is in gromacs-data 2018.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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[ 3' ]
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C3' C3' CN7 12.011 0.14
H3' H3' HN7 1.008 0.09
O3' O3' ON5 15.9994 -0.66
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1 2 H3T O3' C3' C4'
HN5 1.008 0.43 -1
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