From: Jason A. Donenfeld <Jason@zx2c4.com>
Date: Thu, 19 Jul 2018 17:15:15 +0000 (+0200)
Subject: embeddable-wg-library: do not left shift negative numbers
X-Git-Tag: v1.0.20191226~85
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c61c5a03ee2e3186eae57c3f7934f270df7045a7;p=thirdparty%2Fwireguard-tools.git

embeddable-wg-library: do not left shift negative numbers

Otherwise we incur undefined behavior.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---

diff --git a/contrib/embeddable-wg-library/wireguard.c b/contrib/embeddable-wg-library/wireguard.c
index c052355..a65dbce 100644
--- a/contrib/embeddable-wg-library/wireguard.c
+++ b/contrib/embeddable-wg-library/wireguard.c
@@ -1593,16 +1593,11 @@ static __attribute__((noinline)) void memzero_explicit(void *s, size_t count)
 static void carry(fe o)
 {
 	int i;
-	int64_t c;
 
 	for (i = 0; i < 16; ++i) {
-		o[i] += (1LL << 16);
-		c = o[i] >> 16;
-		o[(i + 1) * (i < 15)] += c - 1 + 37 * (c - 1) * (i == 15);
-		o[i] -= c << 16;
+		o[(i + 1) % 16] += (i == 15 ? 38 : 1) * (o[i] >> 16);
+		o[i] &= 0xffff;
 	}
-
-	memzero_explicit(&c, sizeof(c));
 }
 
 static void cswap(fe p, fe q, int b)