Add an heuristic to detect fully encrypted flows (#2058)

A fully encrypted session is a flow where every bytes of the
payload is encrypted in an attempt to “look like nothing”.
The heuristic needs only the very first packet of the flow.
See: https://www.usenix.org/system/files/sec23fall-prepub-234-wu-mingshi.pdf

A basic, but generic, inplementation of the popcpunt alg has been added

1 files changed, 7 insertions, 0 deletions

diff --git a/src/include/ndpi_api.h b/src/include/ndpi_api.h
index 653510e82..121c3f7f8 100644
--- a/src/include/ndpi_api.h
+++ b/src/include/ndpi_api.h
@@ -1843,6 +1843,13 @@ extern "C" {
   
   /* ******************************* */
 
+  /* PopCount [count how many bits are set to 1] */
+
+  int ndpi_popcount_init(struct ndpi_popcount *h);
+  void ndpi_popcount_count(struct ndpi_popcount *h, const u_int8_t *buf, u_int32_t buf_len);
+
+  /* ******************************* */
+
   int  ndpi_init_bin(struct ndpi_bin *b, enum ndpi_bin_family f, u_int16_t num_bins);
   void ndpi_free_bin(struct ndpi_bin *b);
   struct ndpi_bin* ndpi_clone_bin(struct ndpi_bin *b);