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

1 files changed, 14 insertions, 0 deletions

diff --git a/src/plugins/dhcp/dhcp_api.c b/src/plugins/dhcp/dhcp_api.c
index a5163ca2e95..d2e423572fb 100644
--- a/src/plugins/dhcp/dhcp_api.c
+++ b/src/plugins/dhcp/dhcp_api.c
@@ -549,6 +549,12 @@ void
   params.T1 = ntohl (mp->T1);
   params.T2 = ntohl (mp->T2);
   n_addresses = ntohl (mp->n_addresses);
+  /* Make sure that the number of addresses is sane */
+  if (n_addresses * sizeof (params.addresses) > vl_msg_api_max_length (mp))
+    {
+      rv = VNET_API_ERROR_INVALID_VALUE;
+      goto bad_sw_if_index;
+    }
   params.addresses = 0;
   if (n_addresses > 0)
     vec_validate (params.addresses, n_addresses - 1);
@@ -593,6 +599,14 @@ void
   params.T1 = ntohl (mp->T1);
   params.T2 = ntohl (mp->T2);
   n_prefixes = ntohl (mp->n_prefixes);
+
+  /* Minimal check to see that the number of prefixes is sane */
+  if (n_prefixes * sizeof (params.prefixes) > vl_msg_api_max_length (mp))
+    {
+      rv = VNET_API_ERROR_INVALID_VALUE;
+      goto bad_sw_if_index;
+    }
+
   params.prefixes = 0;
   if (n_prefixes > 0)
     vec_validate (params.prefixes, n_prefixes - 1);