bool drakvuf_get_thread_previous_mode( drakvuf_t drakvuf, addr_t kthread, privilege_mode_t *previous_mode ) { if ( kthread ) { *previous_mode = 0 ; if ( vmi_read_8_va( drakvuf->vmi, kthread + drakvuf->offsets[ KTHREAD_PREVIOUSMODE ], 0, (uint8_t *)previous_mode ) == VMI_SUCCESS ) { if ( ( *previous_mode == KERNEL_MODE ) || ( *previous_mode == USER_MODE ) ) return true ; } } return false ; }
int main (int argc, char **argv) { // local variables vmi_instance_t vmi; int ret_val = 0; // return code for after goto struct sigaction signal_action; // process list vars vmi_pid_t pid = 0; char *procname = NULL; addr_t list_head = 0; addr_t next_list_entry = 0; addr_t current_process = 0; addr_t tmp_next = 0; status_t status; // breakpoint vars char* *sym; uint16_t *off; vmi_pid_t *bpid; addr_t *add; uint8_t *byt; addr_t lib_map_addr = 0; addr_t BN_rand_addr = 0; int bnrand_jump_offset = 0; addr_t bnrand_addr = 0; // this is the VM or file that we are looking at if (argc < 2) { printf("Usage: %s <vmname>\n", argv[0]); return 1; } char *name = argv[1]; //////////////////// // Initialization // //////////////////// // initialize the libvmi library printf("Initializing libvmi for VM \"%s\"\n", name); if (vmi_init(&vmi, VMI_XEN|VMI_INIT_COMPLETE|VMI_INIT_EVENTS, name) == VMI_FAILURE) { printf("Failed to init LibVMI library.\n"); ret_val = 2; goto error_exit; } // verify OS is Linux printf("Verifying the VM is running Linux..."); // TODO: verify that the VM is running a *supported* Linux kernel // if kernel is not one we recognize, don't run because we'll be mucking around in memory we don't understand if (VMI_OS_LINUX != vmi_get_ostype(vmi)) { // this only checks if /etc/libvmi.conf says it's "Linux" printf("\nVM is running %s, exiting...\n", vmi_get_ostype(vmi)); ret_val = 3; goto error_exit; } printf(" Yup. Good to go.\n"); // pause the vm for consistent memory access printf("Pausing the VM\n"); if (vmi_pause_vm(vmi) != VMI_SUCCESS) { printf("Failed to pause VM\n"); ret_val = 4; goto error_exit; // don't return directly, do cleanup first } tasks_offset = vmi_get_offset(vmi, "linux_tasks"); name_offset = vmi_get_offset(vmi, "linux_name"); pid_offset = vmi_get_offset(vmi, "linux_pid"); mm_offset = vmi_get_offset(vmi, "linux_mm"); // hardcoded because config_parser doesn't support dynamic config vars mmap_offset = 0x0; vm_area_file_offset = 0xa0; vm_area_next_offset = 0x10; vm_area_start_offset = 0x0; file_path_offset = 0x10; dentry_offset = 0x8; iname_offset = 0x38; //mmap_offset = vmi_get_offset(vmi, "linux_mmap"); //vm_area_file_offset = vmi_get_offset(vmi, "linux_vm_file"); //vm_area_next_offset = vmi_get_offset(vmi, "linux_vm_next"); //vm_area_start_offset = vmi_get_offset(vmi, "linux_vm_start"); //file_path_offset = vmi_get_offset(vmi, "linux_f_path"); //dentry_offset = vmi_get_offset(vmi, "linux_dentry"); //iname_offset = vmi_get_offset(vmi, "linux_d_iname"); if (0 == tasks_offset) { printf("Failed to find tasks_offset\n"); goto error_exit; } if (0 == pid_offset) { printf("Failed to find pid_offset\n"); goto error_exit; } if (0 == name_offset) { printf("Failed to find name_offset\n"); goto error_exit; } if (0 == mm_offset) { printf("Failed to find mm_offset\n"); goto error_exit; } //if (0 == mmap_offset) { // printf("Failed to find mmap_offset\n"); // goto error_exit; //} //if (0 == vm_area_file_offset) { // printf("Failed to find vm_area_file_offset\n"); // goto error_exit; //} //if (0 == vm_area_next_offset) { // printf("Failed to find vm_area_next_offset\n"); // goto error_exit; //} //if (0 == vm_area_start_offset) { // printf("Failed to find vm_area_start_offset\n"); // goto error_exit; //} //if (0 == file_path_offset) { // printf("Failed to find file_path_offset\n"); // goto error_exit; //} //if (0 == dentry_offset) { // printf("Failed to find dentry_offset\n"); // goto error_exit; //} //if (0 == iname_offset) { // printf("Failed to find iname_offset\n"); // goto error_exit; //} // Set up breakpoints breakpoints = (breakpoint_t*)calloc(MAX_BREAKPOINTS, sizeof(breakpoint_t)); // allocate space for each breakpoint, zero memory //add_breakpoint("extract_entropy_user", 155, 0, 0xe8, before_extract_buf); //add_breakpoint("extract_entropy_user", 160, 0, 0x83, after_extract_buf); // new breakpoints created below ////////////////////////// // Find apache2 process // ////////////////////////// // find pid of apache2 processes // for each process, read symbol table and find BN_rand function // at offset +13 bytes from BN_rand, we find an offset from the instruction at BN_rand+17 (probably around -700 bytes) // +570 bytes from the offset above, we find the instruction at which we want a breakpoint // so, breakpoint at BN_rand+17+[BN_rand+13]+570 // then, at callback, read r13 for address of buffer, overwrite with TODO bytes // find pid of apache2 processes list_head = vmi_translate_ksym2v(vmi, "init_task") + tasks_offset; // find init_task struct and move to first linked list entry next_list_entry = list_head; // iterator do { current_process = next_list_entry - tasks_offset; // subtract tasks_offset back off to get to head of struct vmi_read_32_va(vmi, current_process + pid_offset, 0, (uint32_t*)&pid); // get pid of this process procname = vmi_read_str_va(vmi, current_process + name_offset, 0); // get process name of this process if (strncmp(procname,"apache2",sizeof("apache2")) == 0) { printf("Finding library address in %s [pid %d]\n",procname,pid); lib_map_addr = walk_vmmap_for_lib(vmi, current_process, "libcrypto.so.1.0.2"); if (lib_map_addr == 0) { // if failed to find lib printf("Failed to find library in %s\n",procname); ret_val = 9; goto error_exit; } printf("Found library address: 0x%llx\n", lib_map_addr); // for each process, read symbol table and find BN_rand function BN_rand_addr = lib_map_addr + 0xd5a50; // static offset for BN_rand function // at offset +13 bytes from BN_rand, we find an offset from the instruction at BN_rand+17 (probably around -700 bytes) vmi_read_32_va(vmi, BN_rand_addr+13, pid, &bnrand_jump_offset); // get jump offset to bnrand function //printf("jump offset: %d\n",bnrand_jump_offset); bnrand_addr = BN_rand_addr+17+bnrand_jump_offset; // get address of bnrand function //printf("bnrand: 0x%llx\n", bnrand_addr); // +570 bytes from the offset above, we find the instruction at which we want a breakpoint add_breakpoint_addr(bnrand_addr + 570, pid, 0x31, bnrand_callback); //printf("Added breakpoint at 0x%llx\n",bnrand_addr+570); } status = vmi_read_addr_va(vmi, next_list_entry, 0, &next_list_entry); // follow linked-list->next to next element if (status == VMI_FAILURE) { printf("Failed to read next pointer in loop at %"PRIx64"\n", next_list_entry); goto error_exit; } } while(next_list_entry != list_head); for (int i = 0; i < num_breakpoints; i++) { // iterate over breakpoints and find the right addresses for them //////////////////////////////////////////// // Find memory location to put breakpoint // //////////////////////////////////////////// // assign short names (note: modifying these modifies the breakpoint struct) sym = &breakpoints[i].symbol; off = &breakpoints[i].offset; bpid = &breakpoints[i].pid; add = &breakpoints[i].addr; byt = &breakpoints[i].inst_byte; // remember that if this is not set above, it should be zeroed from calloc if (breakpoints[i].addr == 0) { // if don't have address, find symbol // find address to break on printf("Accessing System Map for %s symbol\n", *sym); *add = vmi_translate_ksym2v(vmi, *sym) + *off; printf("%s + %u is at 0x%llx\n", *sym, *off, *add); } // either verify the byte there is correct, or record which byte is there for later replacing if (*byt == 0) { // if this byte was not set, we need to get it vmi_read_8_va(vmi, *add, *bpid, byt); // read it directly into byt printf("[pid %d] Saving byte at address 0x%llx: %x\n", *bpid, *add, *byt); } else { // if the byte was set, verify that it's currently set to that value uint8_t temp_byte = 0; vmi_read_8_va(vmi, *add, *bpid, &temp_byte); // read it temporarily printf("[pid %d] Checking byte at address 0x%llx is set to %x: %x\n", *bpid, *add, *byt, temp_byte); if (*byt != temp_byte) { // uh oh, we have an error ret_val = 8; goto error_exit; } } } // end first for loop after breakpoints are constructed properly /////////////////// // Main gameplan // // // // https://groups.google.com/forum/#!topic/vmitools/jNGxM0LBEDM // Based on the google groups discussion above (which I wish I found earlier, meh), it looks like the way people trap on instructions is to: // 1) actually *modify* the memory to have the 0xcc (interrupt 3, aka breakpoint) instruction in place of the instruction it would have executed // 2) register an event on receiving the INT3 signal and receive the callback // 3) at the end of the callback, fix the memory to its original instruction, // 4) single-step one instruction forward, executing the one instruction, then getting another callback // 5) replace the previous instruction with to 0xcc, "resetting" the breakpoint, then clearing the event and continuing // // /////////////////// for (int i = 0; i < num_breakpoints; i++) { // iterate over breakpoints and insert them all // assign short names (note: modifying these modifies the breakpoint struct) add = &breakpoints[i].addr; bpid = &breakpoints[i].pid; byt = &breakpoints[i].inst_byte; // Step 1: modify memory in the VM with an INT3 instruction (0xcc) printf("[pid %d] Setting breakpoint at address 0x%llx.\n", *bpid, *add); uint8_t int3 = INT3_INST; // create temporary variable because we can't use an address to a static #defined int if (VMI_SUCCESS != vmi_write_8_va(vmi, *add, *bpid, &int3)) { printf("[pid %d] Couldn't write INT3 instruction to memory... exiting.\n", *bpid); ret_val = 5; goto error_exit; } // debug: check memory is now an INT3 instruction uint8_t temp_byte = 0; vmi_read_8_va(vmi, *add, 0, &temp_byte); printf("[pid %d] This should be an INT3 instruction (0xcc): 0x%x\n", *bpid, temp_byte); } // end second for loop after breakpoints are all inserted and callback is registered // Step 2: register an event on receiving INT3 signal printf("Creating event for callback when breakpoint is reached.\n"); memset(&rng_event, 0, sizeof(vmi_event_t)); // clear rng_event so we can set everything fresh rng_event.type = VMI_EVENT_INTERRUPT; // interrupt event -- trigger when interrupt occurs rng_event.interrupt_event.intr = INT3; // trigger on INT3 instruction rng_event.interrupt_event.reinject = 0; // swallow interrupt silently without passing it on to guest rng_event.callback = rng_int3_event_callback; // reference to our callback function printf("Registering event...\n"); if (VMI_SUCCESS == vmi_register_event(vmi, &rng_event)) {; // register the event! printf("Event Registered!\n"); } else { // uh oh, event failed printf("Problem registering event... exiting.\n"); ret_val = 6; goto error_exit; // don't return directly, do cleanup first } // resume the VM printf("Resuming the VM\n"); vmi_resume_vm(vmi); ////////////////////////////////////// // Spin and wait for event callback // ////////////////////////////////////// // for a clean exit, catch signals (from host, not VM), set "interrupted" to non-zero, exit while loop at end of main() signal_action.sa_handler = close_handler; signal_action.sa_flags = 0; sigemptyset(&signal_action.sa_mask); sigaction(SIGHUP, &signal_action, NULL); sigaction(SIGTERM, &signal_action, NULL); sigaction(SIGINT, &signal_action, NULL); sigaction(SIGALRM, &signal_action, NULL); while(!interrupted) { // until an interrupt happens printf("Waiting for events...\n"); if (VMI_SUCCESS != vmi_events_listen(vmi, 500)) { // listen for events for 500ms (no event = VMI_SUCCESS) printf("Error waiting for events... exiting.\n"); interrupted = -1; } } printf("Finished with test.\n"); ////////////////// // Exit cleanly // ////////////////// error_exit: // attempt to remove breakpoints for (int i = 0; i < num_breakpoints; i++) { // iterate over breakpoints and insert them all // assign short names (note: modifying these modifies the breakpoint struct) add = &breakpoints[i].addr; bpid = &breakpoints[i].pid; byt = &breakpoints[i].inst_byte; printf("[pid %d] Removing breakpoint %d at 0x%llx.\n", *bpid, i, *add); if (VMI_SUCCESS != vmi_write_8_va(vmi, *add, *bpid, byt)) { printf("Couldn't write to memory... exiting.\n"); ret_val = 7; } } // resume the vm printf("Resuming the VM\n"); vmi_resume_vm(vmi); // cleanup any memory associated with the LibVMI instance printf("Cleaning up\n"); vmi_destroy(vmi); return ret_val; }