Fix bug in wnaf_fixed where the wnaf array is not completely zeroed when given a 0 scalar.

jonasnick · jonasnick · commit 9e36d1bfe239 · 2018-03-23T14:52:02.000Z
diff --git a/src/ecmult_impl.h b/src/ecmult_impl.h
@@ -571,9 +571,8 @@ static int secp256k1_wnaf_fixed(int *wnaf, const secp256k1_scalar *s, int w) {
     const secp256k1_scalar *work = s;
 
     if (secp256k1_scalar_is_zero(s)) {
-        while (pos * w < WNAF_BITS) {
+        for (pos = 0; pos < WNAF_SIZE(w); pos++) {
             wnaf[pos] = 0;
-            ++pos;
         }
         return 0;
     }

Original file line number	Diff line number	Diff line change
`@@ -571,9 +571,8 @@ static int secp256k1_wnaf_fixed(int wnaf, const secp256k1_scalar s, int w) {`
`571`	`571`	`const secp256k1_scalar *work = s;`
`572`	`572`
`573`	`573`	`if (secp256k1_scalar_is_zero(s)) {`
`574`		`- while (pos * w < WNAF_BITS) {`
	`574`	`+ for (pos = 0; pos < WNAF_SIZE(w); pos++) {`
`575`	`575`	`wnaf[pos] = 0;`
`576`		`- ++pos;`
`577`	`576`	`}`
`578`	`577`	`return 0;`
`579`	`578`	`}`