SETU: avoid 64-bit shift on 64-bit value.

Shifting a 64-bit value by any more than 63 bits is undefined behavior,
apparently - at least, the sanitizers complain about it. The intuitive,
obvious result, of course, is for the result to be 0. In this case, when s ==
0, x << (64 - s) should result in 0, and (x >> s) should result in x, and the
bitwise-or of those two should be x. Which x already was.

Perhaps it should be investigated whether (x >> (64 - s)) should actually
be (x >> (63 - s)), since 0 <= s < 64.

Signed-off-by: Martin Schanzenbach <schanzen@gnunet.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/setu/gnunet-service-setu_strata_estimator.c b/src/setu/gnunet-service-setu_strata_estimator.c
index 7981cc847..43ccf3afd 100644
--- a/src/setu/gnunet-service-setu_strata_estimator.c
+++ b/src/setu/gnunet-service-setu_strata_estimator.c
@@ -85,7 +85,8 @@ salt_key (const struct IBF_Key *k_in,
   uint64_t x = k_in->key_val;
 
   /* rotate ibf key */
-  x = (x >> s) | (x << (64 - s));
+  if (s > 0)
+    x = (x >> s) | (x << (64 - s));
   k_out->key_val = x;
 }