WIP

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/service/http_signatures/http_signatures.ex

@@ -0,0 +1,112 @@
+# https://tools.ietf.org/html/draft-cavage-http-signatures-08
+defmodule Eventos.Service.HTTPSignatures do
+  alias Eventos.Accounts.Account
+  alias Eventos.Service.ActivityPub
+  require Logger
+
+  def split_signature(sig) do
+    default = %{"headers" => "date"}
+
+    sig =
+      sig
+      |> String.trim()
+      |> String.split(",")
+      |> Enum.reduce(default, fn part, acc ->
+        [key | rest] = String.split(part, "=")
+        value = Enum.join(rest, "=")
+        Map.put(acc, key, String.trim(value, "\""))
+      end)
+
+    Map.put(sig, "headers", String.split(sig["headers"], ~r/\s/))
+  end
+
+  def validate(headers, signature, public_key) do
+    sigstring = build_signing_string(headers, signature["headers"])
+    Logger.debug("Signature: #{signature["signature"]}")
+    Logger.debug("Sigstring: #{sigstring}")
+    {:ok, sig} = Base.decode64(signature["signature"])
+    Logger.debug(inspect sig)
+    Logger.debug(inspect public_key)
+    case ExPublicKey.verify(sigstring, sig, public_key) do
+      {:ok, sig_valid} ->
+        sig_valid
+      {:error, err} ->
+        Logger.error(err)
+        false
+    end
+  end
+
+  def validate_conn(conn) do
+    # TODO: How to get the right key and see if it is actually valid for that request.
+    # For now, fetch the key for the actor.
+    with actor_id <- conn.params["actor"],
+         {:ok, public_key} <- Account.get_public_key_for_url(actor_id) do
+      case HTTPSign.verify(conn, public_key) do
+        {:ok, conn} ->
+          true
+        _ ->
+        Logger.debug("Could not validate, re-fetching user and trying one more time")
+        # Fetch user anew and try one more time
+        with actor_id <- conn.params["actor"],
+             {:ok, _user} <- ActivityPub.make_account_from_url(actor_id),
+             {:ok, public_key} <- Account.get_public_key_for_url(actor_id) do
+          case HTTPSign.verify(conn, public_key) do
+            {:ok, conn} ->
+              true
+            {:error, :forbidden} ->
+              false
+          end
+        end
+      end
+    else
+      e ->
+        Logger.debug("Could not public key!")
+        Logger.debug(inspect e)
+        false
+    end
+  end
+
+#  def validate_conn(conn, public_key) do
+#    headers = Enum.into(conn.req_headers, %{})
+#    signature = split_signature(headers["signature"])
+#    validate(headers, signature, public_key)
+#  end
+
+  def build_signing_string(headers, used_headers) do
+    used_headers
+    |> Enum.map(fn header -> "#{header}: #{headers[header]}" end)
+    |> Enum.join("\n")
+  end
+
+  def sign(account, headers) do
+    sigstring = build_signing_string(headers, Map.keys(headers))
+
+    {:ok, private_key} = Account.get_private_key_for_account(account)
+
+    Logger.debug("private_key")
+    Logger.debug(inspect private_key)
+    Logger.debug("sigstring")
+    Logger.debug(inspect sigstring)
+    {:ok, signature} = HTTPSign.Crypto.sign(:rsa, sigstring, private_key)
+    Logger.debug(inspect signature)
+
+    signature = Base.encode64(signature)
+
+    sign = [
+      keyId: account.url <> "#main-key",
+      algorithm: "rsa-sha256",
+      headers: Map.keys(headers) |> Enum.join(" "),
+      signature: signature
+    ]
+    |> Enum.map(fn {k, v} -> "#{k}=\"#{v}\"" end)
+    |> Enum.join(",")
+
+    Logger.debug("sign")
+    Logger.debug(inspect sign)
+    {:ok, public_key} = Account.get_public_key_for_account(account)
+    Logger.debug("inspect split signature inside sign")
+    Logger.debug(inspect split_signature(sign))
+    Logger.debug(inspect validate(headers, split_signature(sign), public_key))
+    sign
+  end
+end