X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=secnet.git;a=blobdiff_plain;f=util.c;h=3d119874eb1c11c7d7b9e367a6bf1a2bef6c4b4b;hp=de91e1e205ad964dca0768b68b969b2a15bf8633;hb=5ad34db2ccbbfbc936cd16121bed2110b70594ba;hpb=28db900b071a43718c4227e759fa76cb8c6359af

diff --git a/util.c b/util.c
index de91e1e..3d11987 100644
--- a/util.c
+++ b/util.c
@@ -381,6 +381,22 @@ static list_t *buffer_apply(closure_t *self, struct cloc loc, dict_t *context,
     return new_closure(&st->cl);
 }
 
+int consttime_memeq(const void *s1in, const void *s2in, size_t n)
+{
+    const uint8_t *s1=s1in, *s2=s2in;
+    register volatile uint8_t accumulator=0;
+
+    while (n-- > 0) {
+	accumulator |= (*s1++ ^ *s2++);
+    }
+    accumulator |= accumulator >> 4; /* constant-time             */
+    accumulator |= accumulator >> 2; /*  boolean canonicalisation */
+    accumulator |= accumulator >> 1;
+    accumulator &= 1;
+    accumulator ^= 1;
+    return accumulator;
+}
+
 void util_module(dict_t *dict)
 {
     add_closure(dict,"sysbuffer",buffer_apply);