util.id: Adjust entropy levels, with rationales

Modules using ids for logging should not need the now pretty large
medium one.

4 files changed, 17 insertions, 6 deletions

diff --git a/net/server_epoll.lua b/net/server_epoll.lua
index f61c204c..faa6a1b5 100644
--- a/net/server_epoll.lua
+++ b/net/server_epoll.lua
@@ -26,7 +26,7 @@ local createtable = require "util.table".create;
 local inet = require "util.net";
 local inet_pton = inet.pton;
 local _SOCKETINVALID = socket._SOCKETINVALID or -1;
-local new_id = require "util.id".medium;
+local new_id = require "util.id".short;
 local xpcall = require "util.xpcall".xpcall;
 
 local poller = require "util.poll"
diff --git a/net/unbound.lua b/net/unbound.lua
index 22b0614b..4a6f0241 100644
--- a/net/unbound.lua
+++ b/net/unbound.lua
@@ -18,7 +18,7 @@ local log = logger.init("unbound");
 local net_server = require "net.server";
 local libunbound = require"lunbound";
 local promise = require"util.promise";
-local new_id = require "util.id".medium;
+local new_id = require "util.id".short;
 
 local gettime = require"socket".gettime;
 local dns_utils = require"util.dns";
diff --git a/plugins/mod_scansion_record.lua b/plugins/mod_scansion_record.lua
index 6d57c209..5fefd398 100644
--- a/plugins/mod_scansion_record.lua
+++ b/plugins/mod_scansion_record.lua
@@ -8,7 +8,7 @@ local dt = require "util.datetime";
 local dm = require "util.datamanager";
 local st = require "util.stanza";
 
-local record_id = id.medium():lower();
+local record_id = id.short():lower();
 local record_date = os.date("%Y%b%d"):lower();
 local header_file = dm.getpath(record_id, "scansion", record_date, "scs", true);
 local record_file = dm.getpath(record_id, "scansion", record_date, "log", true);
diff --git a/util/id.lua b/util/id.lua
index 731355fa..64b56662 100644
--- a/util/id.lua
+++ b/util/id.lua
@@ -17,9 +17,20 @@ local function b64url_random(len)
 end
 
 return {
-	short =  function () return b64url_random(6); end;
-	medium = function () return b64url_random(12); end;
-	long =   function () return b64url_random(24); end;
+	-- sizes divisible by 3 fit nicely into base64 without padding==
+
+	-- close to 8 bytes, should be good enough for relatively short lived or uses
+	-- scoped by host or users, half the size of an uuid
+	short = function() return b64url_random(9); end;
+
+	-- more entropy than uuid at 2/3 the size
+	-- should be okay for globally scoped ids or security token
+	medium = function() return b64url_random(18); end;
+
+	-- as long as an uuid but MOAR entropy
+	long = function() return b64url_random(27); end;
+
+	-- pick your own adventure
 	custom = function (size)
 		return function () return b64url_random(size); end;
 	end;