Date: Sat, 14 Feb 2004 11:03:37 +0900 From: Kimura Fuyuki <fuyuki@nigredo.org> To: freebsd-current@freebsd.org Cc: jdp@polstra.com Subject: dynamic linker problem Message-ID: <86isiaa03q.wl%fuyuki@nigredo.org> In-Reply-To: <86n07oa7sa.wl%fuyuki@nigredo.org> References: <86n07oa7sa.wl%fuyuki@nigredo.org>
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OK, I more clearly point out the problem; run the following test and
think that behavior is secure/modular/comfortable or not.
BEGIN--cut here--cut here
#!/bin/sh
cat <<'[EOF]' >crypt.c
/* Define this function since I want to do so! */
char *crypt_md5(const char *pw, const char *salt)
{
return "imbogus";
}
[EOF]
cat <<'[EOF]' >dltest.c
#include <stdio.h>
#include <dlfcn.h>
int main(void)
{
void *h;
char *(*crypt)(const char *, const char *);
h = dlopen("/lib/libcrypt.so", 0);
crypt = dlsym(h, "crypt");
printf("%s\n", crypt("imthekey", "$1$salt"));
}
[EOF]
cc -shared -o crypt.so crypt.c
# Link against crypt.so since I want to do so!
cc dltest.c -o dltest ./crypt.so
./dltest
END--cut here--cut here
At Thu, 12 Feb 2004 19:53:09 +0900,
Kimura Fuyuki <fuyuki@nigredo.org> wrote:
>
> Someone please run the test below and tell me why dltest[12] show the
> different results on my 5.2.1-RC2 box. At least NetBSD 1.5.2 and some
> sort of Linux pass the test.
>
> #!/bin/sh
>
> cat <<[EOF] >shared.c
> double sin(double d) {return 9;}
> double faked_sin(double d) {return sin(d);}
> [EOF]
>
> cat <<[EOF] >dltest.c
> #include <stdio.h>
> #include <dlfcn.h>
>
> int main(void)
> {
> void *h;
> double (*faked_sin)(double);
>
> h = dlopen("./shared.so", RTLD_LAZY);
> faked_sin = dlsym(h, "faked_sin");
> printf("%f\n", faked_sin(0));
> }
> [EOF]
>
> cc -shared -o shared.so shared.c
>
> cc dltest.c -o dltest1
> ./dltest1 >result1
>
> cc dltest.c -o dltest2 -lm
> ./dltest2 >result2
>
> if diff result1 result2 >/dev/null; then
> echo "You are very talented."
> else
> echo "Please tell me what's happening!"
> fi
-- fuyuki
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