ErlHive is a system for safe community web application development in Erlang that allows users to store and execute code and data in a tuple store database accessed through a web interface. It provides building blocks like blogs and wikis and allows users to safely extend functionality through modules while enforcing access controls and restricting operations for security. The document describes the concepts, execution model, and status of the ErlHive system.

1. ErlHive Safe Erlang Reloaded An angle on community web development Ulf Wiger, Ericsson AB

5. Stored modules extend the vision Authentication, etc. erlhive DB Public code and data Private code and data Safe, web-based community web application development User A User E

10. Code example -module(ex3_joe). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, ..., {ex3_pub, erlhive.ulf.ex3_pub:f() }]. -module(ex3_pub). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, {time, calendar:universal_time()}, {caller, erlhive.user:caller() }, {from_module, erlhive.user:from_module() }, {owner, erlhive.user:owner() }, {ex3_priv, ex3_priv:f() }]. -module(ex3_priv). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, ...]. Owned by user <<”ulf”>> Owned by user <<”joe”>> 1> erlhive:with_user( <<”ulf”>>, fun(M) -> M:set_variable(ex3_pub, [{class, module},{area, public}]), M:store_module(ex3_pub, ”-module(ex3_pub)....”) end).

11. Code example -module(ex3_joe). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, ..., {ex3_pub, erlhive.ulf.ex3_pub:f() }]. -module(ex3_pub). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, {time, calendar:universal_time()}, {caller, erlhive.user:caller() }, {from_module, erlhive.user:from_module() }, {owner, erlhive.user:owner() }, {ex3_priv, ex3_priv:f() }]. -module(ex3_priv). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, ...]. Package syntax for calling other users’ modules ” Meta functions” for introspection

12. Execution -module(ex3_joe). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, ..., {ex3_pub, erlhive.ulf.ex3_pub:f() }]. -module(ex3_pub). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, {time, calendar:universal_time()}, {caller, erlhive.user:caller() }, {from_module, erlhive.user:from_module() }, {owner, erlhive.user:owner() }, {ex3_priv, ex3_priv:f() }]. -module(ex3_priv). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, ...]. 2> erlhive:with_user( <<”joe”>>, fun(M) -> M:apply(erlhive.joe.ex3_joe, f, []) end). [{’?MODULE’, ’erlhive.joe.ex3_joe’}, {caller, <<”joe”>>}, {from_module, ’erlhive.user’}, {owner, <<”joe”>>}, {ex3_pub, [{’?MODULE’, ’erlhive.ulf.ex3_pub’}, {time, {{2006,11,9},{16,53,17}}, {caller, <<”joe”>>}, {owner, <<”ulf”>>}, {ex3_priv, [{’?MODULE’, ’erlhive.ulf.ex3_priv’}, {caller, <<”ulf”>>}, {from_module, ’erlhive.ulf.ex3_pub’}, {owner, <<”ulf”>>}]}]}]

13. Execution -module(ex3_joe). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, ..., {ex3_pub, erlhive.ulf.ex3_pub:f() }]. -module(ex3_pub). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, {caller, erlhive.user:caller() }, {from_module, erlhive.user:from_module() }, {owner, erlhive.user:owner() }, {ex3_priv, ex3_priv:f() }]. -module(ex3_priv). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, ...]. 2> erlhive:with_user( <<”joe”>>, fun(M) -> M:apply(erlhive.ulf.ex3_priv, f, []) end). ** exited: {aborted, {{undef,[{{’erlhive.ulf.ex3_priv’, <<”joe”>>, ’erlhive.user’}, f, 0}, {erlhive,with_watchdog,1}, ...]}, ...} Cannot call another user’s private modules. Restricted calls appear as undefs.

14. Profiling -module(ex3_joe). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, ..., {ex3_pub, erlhive.ulf.ex3_pub:f() }]. -module(ex3_pub). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, {caller, erlhive.user:caller() }, {from_module, erlhive.user:from_module() }, {owner, erlhive.user:owner() }, {ex3_priv, ex3_priv:f() }]. -module(ex3_priv). -export([f/0]). f() -> [{’?MODULE’, ?MODULE}, ...]. 2> erlhive:profile( <<”joe”>>, fun(M) -> M:apply(ex3_joe, f, []) end). { [{’?MODULE’,’erlhive.joe.ex3_joe’}, ...], [{trace,<0.403.0>,call,{erlhive_user,apply,4}}, {trace,<0.403.0>,call,{’erlhive.joe.ex3_joe’,f,1}}, {trace,<0.403.0>,call,{’erlhive.ulf.ex3_pub’,f,1}}, {trace,<0.403.0>,return_to,{’erlhive.ulf.ex3_pub’,f,1}}, {trace ,<0.403.0>,return_to,{’erlhive.ulf.ex3_pub’,f,1}}]} A censored call trace. Can be followed by a specific trace on ’visible’ modules. (work in progress...)

16. Questions?