cr50_fuzz: Add fuzzer for u2f commandsstabilize-ambassador-14268.43.B-cr50_stabstabilize-14268.67.B-cr50_stabstabilize-14268.52.B-cr50_stabstabilize-14268.51.B-cr50_stabrelease-R96-14268.B-cr50_stab

Currently there's only one fuzzer for Pinweaver and one for host
commands in cr50. Add a fuzzer for the u2f commands (generate, sign,
attest) used in the WebAuthn flow to ensure its security. Most regions
of the concerning functions are covered except for pure error code
returns and unreachable regions (currently auth secret is not used in
sign and attest command yet).

Rename old cr50_fuzz namings to pinweaver_fuzz, since they only cover
Pinweaver commands.

BUG=b:172367435
TEST=make buildall -j
TEST=make host-u2f_fuzz && \
     ./build/host/u2f_fuzz/u2f_fuzz.exe -timeout=10 \
     -ignore_ooms=false -ignore_timeouts=false -fork=71; \
     llvm-profdata merge -sparse default.profraw -o default.profdata; \
     llvm-cov show ./build/host/u2f_fuzz/u2f_fuzz.exe \
     -object ./build/host/u2f_fuzz/RO/board/cr50/dcrypto/u2f.o \
     --instr-profile default.profdata \
     board/cr50/dcrypto/u2f.c common/u2f.c > report

Cq-Depend: chromium:3162473
Change-Id: I02b820cf03f7b46ccad7c3bc7b82e73ff45217c6
Signed-off-by: Howard Yang <hcyang@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3162469
Reviewed-by: Andrey Pronin <apronin@chromium.org>
Reviewed-by: Vadim Sukhomlinov <sukhomlinov@chromium.org>
Reviewed-by: Leo Lai <cylai@google.com>

1 files changed, 148 insertions, 0 deletions

diff --git a/fuzz/pinweaver_fuzz.cc b/fuzz/pinweaver_fuzz.cc
new file mode 100644
index 0000000000..853c4341fc
--- /dev/null
+++ b/fuzz/pinweaver_fuzz.cc
@@ -0,0 +1,148 @@
+// Copyright 2018 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Fuzzer for the Cr50 commands related to Pinweaver.
+
+#include <unistd.h>
+
+#include <cassert>
+#include <cstdint>
+#include <cstring>
+#include <unordered_map>
+#include <vector>
+
+#include <src/libfuzzer/libfuzzer_macro.h>
+#include <src/mutator.h>
+
+#define HIDE_EC_STDLIB
+#include "chip/host/persistence.h"
+#include "fuzz/pinweaver_fuzz.pb.h"
+#include "fuzz/fuzz_config.h"
+#include "fuzz/pinweaver_model.h"
+#include "fuzz/span.h"
+#include "include/nvmem.h"
+#include "include/nvmem_vars.h"
+#include "include/pinweaver.h"
+
+using protobuf_mutator::libfuzzer::LoadProtoInput;
+
+namespace {
+constexpr size_t kBufferAlignment = alignof(pw_request_t) >
+                                            alignof(pw_response_t)
+                                        ? alignof(pw_request_t)
+                                        : alignof(pw_response_t);
+}  // namespace
+
+extern "C" uint32_t nvmem_user_sizes[NVMEM_NUM_USERS] = {NVMEM_TPM_SIZE,
+                                                         NVMEM_CR50_SIZE};
+
+extern "C" void rand_bytes(void* data, size_t len) {
+  size_t x = 0;
+
+  uint8_t* buffer = reinterpret_cast<uint8_t*>(data);
+  for (; x < len; ++x) {
+    buffer[x] = rand();
+  }
+}
+
+extern "C" void get_storage_seed(void* buf, size_t* len) {
+  memset(buf, 0x77, *len);
+}
+
+extern "C" uint8_t get_current_pcr_digest(const uint8_t bitmask[2],
+                                          uint8_t sha256_of_selected_pcr[32]) {
+  memset(sha256_of_selected_pcr, 0, 32);
+  return 0;
+}
+
+extern "C" int DCRYPTO_ladder_is_enabled(void) {
+  return 1;
+}
+
+extern "C" void nvmem_wipe_cache(void) {
+  // Nothing to do since there is no cache in this implementation.
+}
+
+// Needed for test targets to build.
+extern "C" void run_test(void) {}
+
+void InitializeFuzzerRun() {
+  memset(__host_flash, 0xff, sizeof(__host_flash));
+  nvmem_init();
+  nvmem_enable_commits();
+  srand(0);
+}
+
+// Used to verify the model hasn't become out of sync with the implementation.
+// The usefulness of this fuzzer comes from its ability to reach all the code
+// paths.
+bool SelfTest() {
+  InitializeFuzzerRun();
+
+  PinweaverModel pinweaver_model;
+  alignas(kBufferAlignment) uint8_t buffer[PW_MAX_MESSAGE_SIZE] = {};
+  fuzz::span<uint8_t> buffer_view(buffer, sizeof(buffer));
+  fuzz::pinweaver::Request request;
+
+  fuzz::pinweaver::ResetTree* reset_tree = request.mutable_reset_tree();
+  reset_tree->set_height(2);
+  reset_tree->set_bits_per_level(2);
+  assert(pinweaver_model.ApplyRequest(request, buffer_view) == EC_SUCCESS);
+
+  fuzz::pinweaver::InsertLeaf* insert_leaf = request.mutable_insert_leaf();
+  constexpr char delay_schedule[] = "\000\000\000\005\377\377\377\377";
+  insert_leaf->mutable_delay_schedule()->assign(
+      delay_schedule, delay_schedule + sizeof(delay_schedule));
+  assert(pinweaver_model.ApplyRequest(request, buffer_view) == EC_SUCCESS);
+
+  request.mutable_try_auth();
+  assert(pinweaver_model.ApplyRequest(request, buffer_view) == EC_SUCCESS);
+
+  request.mutable_get_log();
+  assert(pinweaver_model.ApplyRequest(request, buffer_view) == EC_SUCCESS);
+
+  request.mutable_log_replay();
+  assert(pinweaver_model.ApplyRequest(request, buffer_view) == EC_SUCCESS);
+
+  request.mutable_reset_auth();
+  assert(pinweaver_model.ApplyRequest(request, buffer_view) == EC_SUCCESS);
+
+  request.mutable_remove_leaf();
+  assert(pinweaver_model.ApplyRequest(request, buffer_view) == EC_SUCCESS);
+
+  return true;
+}
+
+DEFINE_CUSTOM_PROTO_MUTATOR_IMPL(false, fuzz::Cr50FuzzerInput)
+DEFINE_CUSTOM_PROTO_CROSSOVER_IMPL(false, fuzz::Cr50FuzzerInput)
+
+extern "C" int test_fuzz_one_input(const uint8_t* data, unsigned int size) {
+  static bool initialized = SelfTest();
+  assert(initialized);
+
+  fuzz::Cr50FuzzerInput input;
+  if (!LoadProtoInput(false, data, size, &input)) {
+    return 0;
+  }
+
+  InitializeFuzzerRun();
+
+  PinweaverModel pinweaver_model;
+  alignas(kBufferAlignment) uint8_t buffer[PW_MAX_MESSAGE_SIZE] = {};
+  fuzz::span<uint8_t> buffer_view(buffer, sizeof(buffer));
+  for (const fuzz::Cr50SubAction& action : input.sub_actions()) {
+    switch (action.sub_action_case()) {
+      case fuzz::Cr50SubAction::kRandomBytes:
+        fuzz::CopyWithPadding(action.random_bytes().value(), buffer_view, 0);
+        pinweaver_model.SendBuffer(buffer_view);
+        break;
+      case fuzz::Cr50SubAction::kPinweaver:
+        pinweaver_model.ApplyRequest(action.pinweaver(), buffer_view);
+        break;
+      case fuzz::Cr50SubAction::SUB_ACTION_NOT_SET:
+        break;
+    }
+  }
+  return 0;
+}