Pleroma/lib/pleroma/web/media_proxy/media_proxy.ex

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# Pleroma: A lightweight social networking server
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# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
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defmodule Pleroma.Web.MediaProxy do
@base64_opts [padding: false]
def url(nil), do: nil
def url(""), do: nil
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def url("/" <> _ = url), do: url
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def url(url) do
config = Application.get_env(:pleroma, :media_proxy, [])
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if !Keyword.get(config, :enabled, false) or String.starts_with?(url, Pleroma.Web.base_url()) do
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url
else
secret = Application.get_env(:pleroma, Pleroma.Web.Endpoint)[:secret_key_base]
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# Must preserve `%2F` for compatibility with S3 (https://git.pleroma.social/pleroma/pleroma/issues/580)
replacement = get_replacement(url, ":2F:")
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# The URL is url-decoded and encoded again to ensure it is correctly encoded and not twice.
base64 =
url
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|> String.replace("%2F", replacement)
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|> URI.decode()
|> URI.encode()
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|> String.replace(replacement, "%2F")
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|> Base.url_encode64(@base64_opts)
sig = :crypto.hmac(:sha, secret, base64)
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sig64 = sig |> Base.url_encode64(@base64_opts)
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build_url(sig64, base64, filename(url))
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end
end
def decode_url(sig, url) do
secret = Application.get_env(:pleroma, Pleroma.Web.Endpoint)[:secret_key_base]
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sig = Base.url_decode64!(sig, @base64_opts)
local_sig = :crypto.hmac(:sha, secret, url)
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if local_sig == sig do
{:ok, Base.url_decode64!(url, @base64_opts)}
else
{:error, :invalid_signature}
end
end
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def filename(url_or_path) do
if path = URI.parse(url_or_path).path, do: Path.basename(path)
end
def build_url(sig_base64, url_base64, filename \\ nil) do
[
Pleroma.Config.get([:media_proxy, :base_url], Pleroma.Web.base_url()),
"proxy",
sig_base64,
url_base64,
filename
]
|> Enum.filter(fn value -> value end)
|> Path.join()
end
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defp get_replacement(url, replacement) do
if String.contains?(url, replacement) do
get_replacement(url, replacement <> replacement)
else
replacement
end
end
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end