Clear Coverity finding CID 186949

The finding is "Overflowed return value", and it is rooted in the constant time code bit manipulations

1 files changed, 4 insertions, 2 deletions

diff --git a/tweetnacl.cpp b/tweetnacl.cpp
index 8348c3ed..9114ef8c 100644
--- a/tweetnacl.cpp
+++ b/tweetnacl.cpp
@@ -72,11 +72,13 @@ static void ts64(uint8_t *x,uint64_t u)
   for (i = 7;i >= 0;--i) { x[i] = u; u >>= 8; }

 }

 

+// Extra cast due to Coverity CID 186949

 static int verify_n(const uint8_t *x,const uint8_t *y,uint32_t n)

 {

   uint32_t i,d = 0;

   for(i=0; i<n; ++i) d |= x[i]^y[i];

-  return (1 & ((d - 1) >> 8)) - 1;

+  const int32_t v = (int32_t) d;

+  return (1 & ((uint32_t)(v - 1) >> 8)) - 1;

 }

 

 int crypto_verify_16(const uint8_t *x,const uint8_t *y)

@@ -892,4 +894,4 @@ int crypto_sign_open(uint8_t *m,uint64_t *mlen,const uint8_t *sm,uint64_t n,cons
 NAMESPACE_END  // CryptoPP

 NAMESPACE_END  // NaCl

 

-#endif  // NO_OS_DEPENDENCE
\ No newline at end of file
+#endif  // NO_OS_DEPENDENCE