auth-filters: do not use HMAC-SHA1

Though SHA1 is broken, HMAC-SHA1 is still fine. But let's not push our
luck; SHA256 is more sensible anyway.

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

filters/gentoo-ldap-authentication.lua

@@ -271,7 +271,7 @@ function validate_value(expected_field, cookie)
 	end
 
 	-- Lua hashes strings, so these comparisons are time invariant.
-	if hmac ~= crypto.hmac.digest("sha1", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, secret) then
+	if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, secret) then
 		return nil
 	end
 
@@ -296,7 +296,7 @@ function secure_value(field, value, expiration)
 	value = url_encode(value)
 	field = url_encode(field)
 	authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
-	authstr = authstr .. "|" .. crypto.hmac.digest("sha1", authstr, secret)
+	authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, secret)
 	return authstr
 end
 

filters/simple-authentication.lua

@@ -231,7 +231,7 @@ function validate_value(expected_field, cookie)
 	end
 
 	-- Lua hashes strings, so these comparisons are time invariant.
-	if hmac ~= crypto.hmac.digest("sha1", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, secret) then
+	if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, secret) then
 		return nil
 	end
 
@@ -256,7 +256,7 @@ function secure_value(field, value, expiration)
 	value = url_encode(value)
 	field = url_encode(field)
 	authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
-	authstr = authstr .. "|" .. crypto.hmac.digest("sha1", authstr, secret)
+	authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, secret)
 	return authstr
 end