Problem - Kevin Tafuro

int bogus_routine(void) {
int x, y;
for (x = 0; x < y; x++) {
y = x + 256;
y /= 32;
x = y * 2 / 24;
}
return 1;
}
SPC_SMC_END_KEY(test)
int main(int argc, char *argv[ ]) {
spc_smc_decrypt(SPC_SMC_BLOCK_ADDR(test), SPC_SMC_BLOCK_LEN(test),
SPC_SMC_KEY_ADDR(test), SPC_SMC_KEY_LEN(test));
#ifdef UNENCRYPTED_BUILD
/* This printf( ) displays the parameters to pass to the smc_encrypt utility on
* stdout. The printf( ) must be removed, and the program recompiled before
* running smc_encrypt. Having the printf( ) at the end of the file prevents
* the offsets from changing after recompilation.
*/
printf("(offsets from _start)offset: 0x%X len 0x%X key 0x%X len 0x%X\n",
SPC_SMC_OFFSET(SPC_SMC_BLOCK_ADDR(test)), SPC_SMC_BLOCK_LEN(test),
SPC_SMC_OFFSET(SPC_SMC_KEY_ADDR(test)), SPC_SMC_KEY_LEN(test));
exit(0);
#endif
test_routine( );
return 0;
}
As mentioned in the comment just prior to the printf( ) call in main( ), this program
should be compiled with UNENCRYPTED_BUILD defined, then executed to obtain the
parameters to the smc_encrypt utility:
/bin/sh>cc -I. smc.c smc_test.c -D UNENCRYPTED_BUILD
/bin/sh>./a.out
(offsets from _start)offset: 0xB0 len 0x36 key 0xEB len 0x66
The program is then recompiled, with UNENCRYPTED_BUILD not defined in order to
remove the printf( ) and exit( ) statements. The smc_encrypt utility is then run on
the resulting binary to produce a working program:
/bin/sh>cc -I. smc.c smc_test.c
/bin/sh>smc_encrypt a.out 0xB0 0x36 0xEB 0x66
Self-modifying code is one of the most potent techniques available for protecting
binary code; however, it makes the build process more complex, as you can see in
the above example. In addition, some processor architectures (such as the x86 line
before the Pentium II) cache instructions and do not invalidate this cache when the
code segment is written to. To be compatible with these older architectures, you will
698 | Chapter 12: Anti-Tampering
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