It is possible to set the instruction pointer to undefined values by
using an operator larger than ':' in ASCII.
Since the personality function array does not have 256 entries, an
invalid operator can overflow the array.
Proof of concept:
$ echo "a _ b" > poc
$ ln -s $(which pkgconf) poc-pkgconf
$ ./poc-pkgconf
On Debian/Ubuntu I get:
CC libpkgconf/personality.lo
libpkgconf/personality.c: In function ‘load_personality_with_path’:
libpkgconf/personality.c:195:3: warning: implicit declaration of function ‘strlcpy’ [-Wimplicit-function-declaration]
strlcpy(pathbuf, path, sizeof pathbuf);
^~~~~~~
CC libpkgconf/parser.lo
CCLD libpkgconf.la
ar: `u' modifier ignored since `D' is the default (see `U')
CC cli/pkgconf-main.o
CC cli/pkgconf-getopt_long.o
CC cli/pkgconf-renderer-msvc.o
CCLD pkgconf
./.libs/libpkgconf.so: undefined reference to `strlcpy'
Tobias Stoeckmann
Ariadne Conill