298 lines
13 KiB
OCaml
298 lines
13 KiB
OCaml
open Lwt.Infix
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let users : (string, string * (Mirage_crypto_ec.P256.Dsa.pub * string * X509.Certificate.t option) list) Hashtbl.t = Hashtbl.create 7
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let find_username username =
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Hashtbl.fold (fun id v r ->
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if String.equal (fst v) username then Some (id, v) else r)
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users None
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module KhPubHashtbl = Hashtbl.Make(struct
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type t = Webauthn.credential_id * Mirage_crypto_ec.P256.Dsa.pub
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let cs_of_pub = Mirage_crypto_ec.P256.Dsa.pub_to_cstruct
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let equal (kh, pub) (kh', pub') =
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String.equal kh kh' && Cstruct.equal (cs_of_pub pub) (cs_of_pub pub')
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let hash (kh, pub) = Hashtbl.hash (kh, Cstruct.to_string (cs_of_pub pub ))
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end)
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let counters = KhPubHashtbl.create 7
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let check_counter kh_pub counter =
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let r =
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match KhPubHashtbl.find_opt counters kh_pub with
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| Some counter' -> Int32.unsigned_compare counter counter' > 0
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| None -> true
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in
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if r
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then KhPubHashtbl.replace counters kh_pub counter;
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r
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let registration_challenges : (string, string * Webauthn.challenge list) Hashtbl.t = Hashtbl.create 7
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let remove_registration_challenge userid challenge =
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match Hashtbl.find_opt registration_challenges userid with
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| None -> ()
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| Some (username, challenges) ->
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let challenges = List.filter (fun c -> not (Webauthn.challenge_equal c challenge)) challenges in
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if challenges = [] then
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Hashtbl.remove registration_challenges userid
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else
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Hashtbl.replace registration_challenges userid (username, challenges)
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let authentication_challenges : (string, Webauthn.challenge list) Hashtbl.t = Hashtbl.create 7
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let remove_authentication_challenge userid challenge =
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match Hashtbl.find_opt authentication_challenges userid with
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| None -> ()
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| Some challenges ->
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let challenges = List.filter (fun c -> not (Webauthn.challenge_equal c challenge)) challenges in
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if challenges = [] then
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Hashtbl.remove authentication_challenges userid
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else
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Hashtbl.replace authentication_challenges userid challenges
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let to_string err = Format.asprintf "%a" Webauthn.pp_error err
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let gen_data ?(pad = false) ?alphabet length =
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Base64.encode_string ~pad ?alphabet
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(Cstruct.to_string (Mirage_crypto_rng.generate length))
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let add_routes t =
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let main req =
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let authenticated_as = Dream.session "authenticated_as" req in
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let flash = Flash_message.get_flash req |> List.map snd in
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Dream.html (Template.overview flash authenticated_as users)
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in
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let register req =
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let user =
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match Dream.session "authenticated_as" req with
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| None -> gen_data ~alphabet:Base64.uri_safe_alphabet 8
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| Some username -> username
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in
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Dream.html (Template.register_view (Webauthn.rpid t) user)
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in
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let registration_challenge req =
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let user = Dream.param req "user" in
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let challenge, challenge_b64 = Webauthn.generate_challenge () in
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let userid, credentials = match find_username user with
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| None -> gen_data ~alphabet:Base64.uri_safe_alphabet 8, []
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| Some (userid, (_, credentials)) -> userid, List.map (fun (_, cid, _) -> cid) credentials
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in
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let challenges =
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Option.map snd (Hashtbl.find_opt registration_challenges userid) |>
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Option.value ~default:[]
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in
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Hashtbl.replace registration_challenges userid (user, challenge :: challenges);
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let json = `Assoc [
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"challenge", `String challenge_b64 ;
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"user", `Assoc [
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"id", `String userid ;
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"name", `String user ;
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"displayName", `String user ;
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] ;
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"excludeCredentials", `List (List.map (fun s -> `String (Base64.encode_string s)) credentials) ;
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]
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in
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Logs.info (fun m -> m "produced challenge for user %s: %s" user challenge_b64);
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Dream.json (Yojson.Safe.to_string json)
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in
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let register_finish req =
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let userid = Dream.param req "userid" in
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Dream.body req >>= fun body ->
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Logs.debug (fun m -> m "received body: %s" body);
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match Hashtbl.find_opt registration_challenges userid with
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| None ->
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Logs.warn (fun m -> m "no challenge found");
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Dream.respond ~status:`Bad_Request "Bad request."
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| Some (username, challenges) ->
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match Webauthn.register_response_of_string body with
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| Error e ->
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Logs.warn (fun m -> m "error %a" Webauthn.pp_error e);
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let err = to_string e in
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Flash_message.put_flash "" ("Registration failed " ^ err) req;
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Dream.json "false"
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| Ok response ->
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match Webauthn.register t response with
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| Error e ->
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Logs.warn (fun m -> m "error %a" Webauthn.pp_error e);
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let err = to_string e in
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Flash_message.put_flash "" ("Registration failed " ^ err) req;
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Dream.json "false"
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| Ok (challenge, { user_present ; user_verified ; sign_count ; attested_credential_data ; certificate ; _ }) ->
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let { Webauthn.credential_id ; public_key ; _ } = attested_credential_data in
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if not (List.exists (Webauthn.challenge_equal challenge) challenges) then begin
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Logs.warn (fun m -> m "challenge invalid");
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Flash_message.put_flash "" "Registration failed: invalid challenge" req;
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Dream.json "false"
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end else begin
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remove_registration_challenge userid challenge;
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ignore (check_counter (credential_id, public_key) sign_count);
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Logs.info (fun m -> m "register %S user present %B user verified %B"
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username user_present user_verified);
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let registered other_keys =
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Logs.app (fun m -> m "registered %s: %S" username credential_id);
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Hashtbl.replace users userid (username, ((public_key, credential_id, certificate) :: other_keys)) ;
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Dream.invalidate_session req >>= fun () ->
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let cert_pem, cert_string, transports =
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Option.fold ~none:("No certificate", "No certificate", Ok [])
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~some:(fun c ->
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X509.Certificate.encode_pem c |> Cstruct.to_string,
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Fmt.to_to_string X509.Certificate.pp c,
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Webauthn.transports_of_cert c)
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certificate
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in
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let transports = match transports with
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| Error `Msg m -> "error " ^ m
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| Ok ts -> Fmt.str "%a" Fmt.(list ~sep:(any ", ") Webauthn.pp_transport) ts
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in
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Flash_message.put_flash ""
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(Printf.sprintf "Successfully registered as %s! <a href=\"/authenticate/%s\">[authenticate]</a><br/>Certificate transports: %s<br/>Certificate: %s<br/>PEM Certificate:<br/><pre>%s</pre>" username userid transports cert_string cert_pem)
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req;
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Dream.json "true"
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in
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match Dream.session "authenticated_as" req, Hashtbl.find_opt users userid with
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| _, None -> registered []
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| Some session_user, Some (username', keys) ->
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if String.equal username session_user && String.equal username username' then begin
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registered keys
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end else
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(Logs.info (fun m -> m "session_user %s, user %s (user in users table %s)" session_user username username');
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Dream.json ~status:`Forbidden "false")
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| None, Some _keys ->
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Logs.app (fun m -> m "no session user");
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Dream.json ~status:`Forbidden "false"
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end
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in
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let authenticate req =
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let userid = Dream.param req "userid" in
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match Hashtbl.find_opt users userid with
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| None ->
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Logs.warn (fun m -> m "no user found");
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Dream.respond ~status:`Bad_Request "Bad request."
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| Some (username, keys) ->
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let credentials = List.map (fun (_, c, _) -> Base64.encode_string c) keys in
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let challenge, challenge_b64 = Webauthn.generate_challenge () in
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let challenges = Option.value ~default:[] (Hashtbl.find_opt authentication_challenges userid) in
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Hashtbl.replace authentication_challenges userid (challenge :: challenges);
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Dream.html (Template.authenticate_view challenge_b64 credentials username)
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in
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let authenticate_finish req =
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let userid = Dream.param req "userid"
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and b64_credential_id = Dream.param req "credential_id"
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in
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match Base64.decode ~alphabet:Base64.uri_safe_alphabet ~pad:false b64_credential_id with
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| Error `Msg err ->
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Logs.err (fun m -> m "credential id (%S) is not base64 uri safe: %s" b64_credential_id err);
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Dream.json ~status:`Bad_Request "credential ID decoding error"
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| Ok credential_id ->
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Dream.body req >>= fun body ->
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Logs.debug (fun m -> m "received body: %s" body);
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match Hashtbl.find_opt authentication_challenges userid, Hashtbl.find_opt users userid with
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| None, _ -> Dream.respond ~status:`Internal_Server_Error "Internal server error."
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| _, None ->
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Logs.warn (fun m -> m "no user found with id %s" userid);
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Dream.respond ~status:`Bad_Request "Bad request."
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| Some challenges, Some (username, keys) ->
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match List.find_opt (fun (_, cid, _) -> String.equal cid credential_id) keys with
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| None ->
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Logs.warn (fun m -> m "no key found with credential id %s" b64_credential_id);
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Dream.respond ~status:`Bad_Request "Bad request."
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| Some (pubkey, _, _) ->
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match Webauthn.authenticate_response_of_string body with
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| Error e ->
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Logs.warn (fun m -> m "error %a" Webauthn.pp_error e);
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let err = to_string e in
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Flash_message.put_flash "" ("Authentication failure: " ^ err) req;
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Dream.json "false"
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| Ok authenticate_response ->
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match Webauthn.authenticate t pubkey authenticate_response with
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| Ok (challenge, { user_present ; user_verified ; sign_count ; _ }) ->
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Logs.info (fun m -> m "authenticate %S user present %B user verified %B"
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username user_present user_verified);
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if not (List.exists (Webauthn.challenge_equal challenge) challenges) then begin
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Logs.warn (fun m -> m "invalid challenge");
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Flash_message.put_flash "" "Authentication failure: invalid challenge" req;
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Dream.json "false"
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end else begin
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remove_authentication_challenge userid challenge;
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if check_counter (credential_id, pubkey) sign_count
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then begin
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Flash_message.put_flash "" "Successfully authenticated" req;
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Dream.put_session "authenticated_as" username req >>= fun () ->
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Dream.json "true"
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end else begin
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Logs.warn (fun m -> m "credential %S for user %S: counter not strictly increasing! \
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Got %ld, expected >%ld. webauthn device compromised?"
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b64_credential_id username sign_count (KhPubHashtbl.find counters (credential_id, pubkey)));
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Flash_message.put_flash "" "Authentication failure: key compromised?" req;
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Dream.json "false"
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end
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end
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| Error e ->
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Logs.warn (fun m -> m "error %a" Webauthn.pp_error e);
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let err = to_string e in
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Flash_message.put_flash "" ("Authentication failure: " ^ err) req;
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Dream.json "false"
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in
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let logout req =
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Dream.invalidate_session req >>= fun () ->
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Dream.redirect req "/"
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in
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let base64 _req =
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Dream.respond ~headers:[("Content-type", "application/javascript")]
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[%blob "base64.js"]
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in
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Dream.router [
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Dream.get "/" main;
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Dream.get "/register" register;
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Dream.get "/registration-challenge/:user" registration_challenge;
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Dream.post "/register_finish/:userid" register_finish;
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Dream.get "/authenticate/:userid" authenticate;
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Dream.post "/authenticate_finish/:credential_id/:userid" authenticate_finish;
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Dream.post "/logout" logout;
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Dream.get "/static/base64.js" base64;
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]
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let setup_app level port host origin tls =
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let level = match level with None -> None | Some Logs.Debug -> Some `Debug | Some Info -> Some `Info | Some Warning -> Some `Warning | Some Error -> Some `Error | Some App -> None in
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Dream.initialize_log ?level ();
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match Webauthn.create origin with
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| Error e -> Logs.err (fun m -> m "failed to create webauthn: %s" e); exit 1
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| Ok webauthn ->
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Dream.run ~port ~interface:host ~tls
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@@ Dream.logger
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@@ Dream.memory_sessions
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@@ Flash_message.flash_messages
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@@ add_routes webauthn
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open Cmdliner
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let port =
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let doc = "port" in
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Arg.(value & opt int 5000 & info [ "p"; "port" ] ~doc)
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let host =
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let doc = "host" in
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Arg.(value & opt string "0.0.0.0" & info [ "h"; "host" ] ~doc)
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let origin =
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let doc = "the webauthn relying party origin - usually protocol://host" in
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Arg.(value & opt string "https://webauthn-demo.robur.coop" & info [ "origin" ] ~doc)
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let tls =
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let doc = "tls" in
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Arg.(value & flag & info [ "tls" ] ~doc)
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let () =
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let term = Term.(const setup_app $ Logs_cli.level () $ port $ host $ origin $ tls) in
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let info = Cmd.info "Webauthn app" ~doc:"Webauthn app" ~man:[] in
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exit (Cmd.eval (Cmd.v info term))
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