libsec: move zero check to curve25519_dh_finish()

[plan9front.git] / sys / src / libsec / port / curve25519_dh.c

diff --git a/sys/src/libsec/port/curve25519_dh.c b/sys/src/libsec/port/curve25519_dh.c
index efc16ac8d5fd9a3ce6075cb341a1893e16365e4c..4d1c1a7072eb869e46a642ae6f5869b7a23346c6 100644 (file)
--- a/sys/src/libsec/port/curve25519_dh.c
+++ b/sys/src/libsec/port/curve25519_dh.c
@@ -3,6 +3,7 @@
 #include <libsec.h>
 
 static uchar nine[32] = {9};
+static uchar zero[32] = {0};
 
 void
 curve25519_dh_new(uchar x[32], uchar y[32])
@@ -20,7 +21,7 @@ curve25519_dh_new(uchar x[32], uchar y[32])
        y[31] |= b & 0x80;
 }
 
-void
+int
 curve25519_dh_finish(uchar x[32], uchar y[32], uchar z[32])
 {
        /* remove the random bit */
@@ -31,4 +32,6 @@ curve25519_dh_finish(uchar x[32], uchar y[32], uchar z[32])
 
        memset(x, 0, 32);
        memset(y, 0, 32);
+
+       return tsmemcmp(z, zero, 32) != 0;
 }