proxy: update vendor

Signed-off-by: Evan Hazlett <ejhazlett@gmail.com>

vendor/github.com/jimstudt/http-authentication/basic/util.go

@@ -0,0 +1,18 @@
+package basic
+
+import (
+	"crypto/sha1"
+	"crypto/subtle"
+)
+
+func constantTimeEquals(a string, b string) bool {
+	// compare SHA-1 as a gatekeeper in constant time
+	// then check that we didn't get by because of a collision
+	aSha := sha1.Sum([]byte(a))
+	bSha := sha1.Sum([]byte(b))
+	if subtle.ConstantTimeCompare(aSha[:], bSha[:]) == 1 {
+		// yes, this bit isn't constant, but you had to make a Sha1 collision to get here
+		return a == b
+	}
+	return false
+}