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# https://tools.ietf.org/html/draft-cavage-http-signatures-08
defmodule Pleroma.Web.HTTPSignatures do
alias Pleroma.User
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"])
{:ok, sig} = Base.decode64(signature["signature"])
:public_key.verify(sigstring, :sha256, sig, public_key)
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} <- User.get_public_key_for_ap_id(actor_id) do
validate_conn(conn, public_key)
else
_ -> 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
end
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