ipsec: fix trailing data overflow

IPsec writes trailing data at the end of the buffer without checking
if there is enough space. If the packet length equals buffer size this
leads to rewiting of the next buffer header in the pool.

Type: fix

Change-Id: Iceb27bb724c7243863a4b532aad0808051b7d74c
Signed-off-by: Filip Tehlar <ftehlar@cisco.com>

1 files changed, 21 insertions, 23 deletions

diff --git a/src/vnet/ipsec/esp_encrypt.c b/src/vnet/ipsec/esp_encrypt.c
index 730a2b83c11..186e122793d 100644
--- a/src/vnet/ipsec/esp_encrypt.c
+++ b/src/vnet/ipsec/esp_encrypt.c
@@ -91,7 +91,9 @@ format_esp_encrypt_trace (u8 * s, va_list * args)
 
 /* pad packet in input buffer */
 static_always_inline u8 *
-esp_add_footer_and_icv (vlib_buffer_t * b, u8 block_size, u8 icv_sz)
+esp_add_footer_and_icv (vlib_buffer_t * b, u8 block_size, u8 icv_sz,
+			u16 * next, vlib_node_runtime_t * node,
+			u16 buffer_data_size)
 {
   static const u8 pad_data[ESP_MAX_BLOCK_SIZE] = {
     0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
@@ -104,8 +106,15 @@ esp_add_footer_and_icv (vlib_buffer_t * b, u8 block_size, u8 icv_sz)
   esp_footer_t *f = (esp_footer_t *) (vlib_buffer_get_current (b) +
 				      new_length - sizeof (esp_footer_t));
 
+  if (b->current_data + new_length + icv_sz > buffer_data_size)
+    {
+      b->error = node->errors[ESP_ENCRYPT_ERROR_NO_TRAILER_SPACE];
+      next[0] = ESP_ENCRYPT_NEXT_DROP;
+      return 0;
+    }
+
   if (pad_bytes)
-    clib_memcpy_fast ((u8 *) f - pad_bytes, pad_data, ESP_MAX_BLOCK_SIZE);
+    clib_memcpy_fast ((u8 *) f - pad_bytes, pad_data, pad_bytes);
 
   f->pad_length = pad_bytes;
   b->current_length = new_length + icv_sz;
@@ -188,19 +197,6 @@ esp_get_ip6_hdr_len (ip6_header_t * ip6)
   return len;
 }
 
-static_always_inline int
-esp_trailer_icv_overflow (vlib_node_runtime_t * node, vlib_buffer_t * b,
-			  u16 * next, u16 buffer_data_size)
-{
-  if (b->current_data + b->current_length <= buffer_data_size)
-    return 0;
-
-  b->current_length -= buffer_data_size - b->current_data;
-  b->error = node->errors[ESP_ENCRYPT_ERROR_NO_TRAILER_SPACE];
-  next[0] = ESP_ENCRYPT_NEXT_DROP;
-  return 1;
-}
-
 static_always_inline void
 esp_process_ops (vlib_main_t * vm, vlib_node_runtime_t * node,
 		 vnet_crypto_op_t * ops, vlib_buffer_t * b[], u16 * nexts)
@@ -326,11 +322,12 @@ esp_encrypt_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
       if (ipsec_sa_is_set_IS_TUNNEL (sa0))
 	{
 	  payload = vlib_buffer_get_current (b[0]);
-	  next_hdr_ptr = esp_add_footer_and_icv (b[0], block_sz, icv_sz);
-	  payload_len = b[0]->current_length;
-
-	  if (esp_trailer_icv_overflow (node, b[0], next, buffer_data_size))
+	  next_hdr_ptr = esp_add_footer_and_icv (b[0], block_sz, icv_sz,
+						 next, node,
+						 buffer_data_size);
+	  if (!next_hdr_ptr)
 	    goto trace;
+	  payload_len = b[0]->current_length;
 
 	  /* ESP header */
 	  hdr_len += sizeof (*esp);
@@ -389,11 +386,12 @@ esp_encrypt_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 
 	  vlib_buffer_advance (b[0], ip_len);
 	  payload = vlib_buffer_get_current (b[0]);
-	  next_hdr_ptr = esp_add_footer_and_icv (b[0], block_sz, icv_sz);
-	  payload_len = b[0]->current_length;
-
-	  if (esp_trailer_icv_overflow (node, b[0], next, buffer_data_size))
+	  next_hdr_ptr = esp_add_footer_and_icv (b[0], block_sz, icv_sz,
+						 next, node,
+						 buffer_data_size);
+	  if (!next_hdr_ptr)
 	    goto trace;
+	  payload_len = b[0]->current_length;
 
 	  /* ESP header */
 	  hdr_len += sizeof (*esp);