misc: binary api fuzz test fixes

Add a hook to src/vlibapi/api_shared.c to fuzz (screw up) binary API
messages, e.g. by xoring random data into them before processing. We
specifically exempt client connection messages, and inband debug CLI
messages. We step over msg_id, client index, client context, and
sw_if_index. Otherwise, "make test" vectors fail too rapidly to learn
anything.

The goal is to reduce the number of crashes caused to zero. We're
fairly close with this patch.

Add vl_msg_api_max_length(void *mp), which returns the maximum
plausible length for a binary API message.

Use it to hardern vl_api_from_api_to_new_vec(...) which takes an
additional argument - message pointer - so it can verify that
astr->length is sane. If it's not sane, return a u8 *vector of the
form "insane astr->length nnnn\0".

Verify array lengths in vl_api_dhcp6_send_client_message_t_handler(...)
and vl_api_dhcp6_pd_send_client_message_t_handler(...).

Add a fairly effective binary API fuzz hook to the unittest plugin,
and modify the "make test" framework.py to pass "api-fuzz { on|off }"
to enable API fuzzing: "make API_FUZZ=on TEST=xxx test-debug" or similar

Type: improvement

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: I0157267652a163c01553d5267620f719cc6c3bde

2 files changed, 188 insertions, 0 deletions

diff --git a/src/plugins/unittest/CMakeLists.txt b/src/plugins/unittest/CMakeLists.txt
index 7ab63dad6a4..3ea4752145b 100644
--- a/src/plugins/unittest/CMakeLists.txt
+++ b/src/plugins/unittest/CMakeLists.txt
@@ -13,6 +13,7 @@
 
 add_vpp_plugin(unittest
   SOURCES
+  api_fuzz_test.c
   bier_test.c
   bihash_test.c
   bitmap_test.c
diff --git a/src/plugins/unittest/api_fuzz_test.c b/src/plugins/unittest/api_fuzz_test.c
new file mode 100644
index 00000000000..113835300bb
--- /dev/null
+++ b/src/plugins/unittest/api_fuzz_test.c
@@ -0,0 +1,187 @@
+/*
+ *------------------------------------------------------------------
+ * api_fuzz_test.c - Binary API fuzz hook
+ *
+ * Copyright (c) 2020 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *------------------------------------------------------------------
+ */
+#include <vppinfra/format.h>
+#include <vppinfra/byte_order.h>
+#include <vppinfra/error.h>
+#include <vlib/vlib.h>
+#include <vlib/unix/unix.h>
+#include <vlibapi/api.h>
+
+static u32 fuzz_seed = 0xdeaddabe;
+static u16 fuzz_first;
+static u16 fuzz_cli_first, fuzz_cli_last;
+
+extern void (*vl_msg_api_fuzz_hook) (u16, void *);
+
+static void
+fuzz_hook (u16 id, void *the_msg)
+{
+  /*
+   * Fuzz (aka screw up) this message? Leave connection establishment
+   * messages alone as well as CLI messages.
+   */
+  if ((id > fuzz_first) && !(id >= fuzz_cli_first && id < fuzz_cli_last))
+    {
+      msgbuf_t *mb;
+      u8 *limit, *start;
+
+      mb = (msgbuf_t *) (((u8 *) the_msg) - offsetof (msgbuf_t, data));
+
+      limit = (u8 *) (mb->data + ntohl (mb->data_len));
+
+      /*
+       * Leave the first 14 octets alone, aka msg_id, client_index,
+       * context, sw_if_index
+       */
+
+      start = ((u8 *) the_msg) + 14;
+
+      for (; start < limit; start++)
+	*start ^= (random_u32 (&fuzz_seed) & 0xFF);
+    }
+}
+
+static void
+default_fuzz_config (void)
+{
+  fuzz_first = vl_msg_api_get_msg_index
+    ((u8 *) "memclnt_keepalive_reply_e8d4e804");
+  fuzz_cli_first = vl_msg_api_get_msg_index ((u8 *) "cli_23bfbfff");
+  fuzz_cli_last = vl_msg_api_get_msg_index
+    ((u8 *) "cli_inband_reply_05879051");
+}
+
+static clib_error_t *
+test_api_fuzz_command_fn (vlib_main_t * vm,
+			  unformat_input_t * input, vlib_cli_command_t * cmd)
+{
+  u32 tmp;
+
+  default_fuzz_config ();
+
+  if (fuzz_first == 0xFFFF)
+    {
+      vlib_cli_output (vm, "Couldn't find 'memclnt_keepalive_reply' ID");
+      vlib_cli_output
+	(vm, "Manual setting required, use 'show api message table'");
+    }
+
+  if (fuzz_cli_first == 0xFFFF)
+    {
+      vlib_cli_output (vm, "Couldn't find 'cli' ID");
+      vlib_cli_output
+	(vm, "Manual setting required, use 'show api message table'");
+    }
+
+  if (fuzz_cli_last == 0xFFFF)
+    {
+      vlib_cli_output (vm, "Couldn't find 'cli_inband_reply' ID");
+      vlib_cli_output
+	(vm, "Manual setting required, use 'show api message table'");
+    }
+
+  while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT)
+    {
+      if (unformat (input, "seed %d", &fuzz_seed))
+	;
+      else if (unformat (input, "disable") | unformat (input, "off"))
+	fuzz_first = ~0;
+      else if (unformat (input, "fuzz-first %d", &tmp))
+	fuzz_first = (u16) tmp;
+      else if (unformat (input, "fuzz-cli-first %d", &tmp))
+	fuzz_cli_first = (u16) tmp;
+      else if (unformat (input, "fuzz-cli-last %d", &tmp))
+	fuzz_cli_last = (u16) tmp;
+      else
+	break;
+    }
+
+  if (fuzz_first == 0xFFFF)
+    {
+      vl_msg_api_fuzz_hook = 0;
+      return clib_error_return (0, "fuzz_first is ~0, fuzzing disabled");
+    }
+  vl_msg_api_fuzz_hook = fuzz_hook;
+
+  vlib_cli_output (vm, "Fuzzing enabled: first %d, skip cli range %d - %d",
+		   (u32) fuzz_first, (u32) fuzz_cli_first,
+		   (u32) fuzz_cli_last);
+
+  return 0;
+}
+
+/* *INDENT-OFF* */
+VLIB_CLI_COMMAND (test_api_fuzz, static) = {
+   .path = "test api fuzz",
+   .short_help = "test api fuzz [disable][seed nnn]\n"
+   "           [fuzz-first nn][fuzz-cli-first nn][fuzz-cli-last nn]",
+   .function = test_api_fuzz_command_fn,
+  };
+/* *INDENT-ON* */
+
+static u8 main_loop_enter_enable_api_fuzz;
+
+static clib_error_t *
+api_fuzz_config (vlib_main_t * vm, unformat_input_t * input)
+{
+  while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT)
+    {
+      if (unformat (input, "off")
+	  || unformat (input, "disable") || unformat (input, "no"))
+	;			/* ok, no action */
+      else if (unformat (input, "on")
+	       || unformat (input, "enable") || unformat (input, "yes"))
+	main_loop_enter_enable_api_fuzz = 1;
+      else
+	return clib_error_return (0, "unknown input '%U'",
+				  format_unformat_error, input);
+    }
+  return 0;
+}
+
+VLIB_CONFIG_FUNCTION (api_fuzz_config, "api-fuzz");
+
+static clib_error_t *
+api_fuzz_api_init (vlib_main_t * vm)
+{
+  /* Are we supposed to fuzz API messages? */
+  if (main_loop_enter_enable_api_fuzz == 0)
+    return 0;
+
+  default_fuzz_config ();
+
+  if (fuzz_first == 0xFFFF)
+    {
+      return clib_error_return
+	(0, "Couldn't find 'memclnt_keepalive_reply' ID");
+    }
+  /* Turn on fuzzing */
+  vl_msg_api_fuzz_hook = fuzz_hook;
+  return 0;
+}
+
+VLIB_API_INIT_FUNCTION (api_fuzz_api_init);
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */