Skip to content

Fallback when hash_equals fails for missing openssl support #45

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
josevalim merged 2 commits into from
Apr 2, 2025
Merged

Fallback when hash_equals fails for missing openssl support #45

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
a634c97
Fallback if native hash_equals is not available.
dominicletz Feb 20, 2025
3f964c2
Readd comment
dominicletz Apr 2, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
26 changes: 17 additions & 9 deletions lib/plug/crypto.ex
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -133,22 +133,30 @@ defmodule Plug.Crypto do
# TODO: remove when we require OTP 25.0
if Code.ensure_loaded?(:crypto) and function_exported?(:crypto, :hash_equals, 2) do
defp crypto_hash_equals(x, y) do
:crypto.hash_equals(x, y)
# Depending on the linked OpenSSL library hash_equals is available.
# If not, we fall back to the legacy implementation.
try do
:crypto.hash_equals(x, y)
rescue
# Still can throw "Unsupported CRYPTO_memcmp"
ErlangError ->
legacy_secure_compare(x, y, 0)
end
end
else
defp crypto_hash_equals(x, y) do
legacy_secure_compare(x, y, 0)
end
end

defp legacy_secure_compare(<<x, left::binary>>, <<y, right::binary>>, acc) do
import Bitwise
xorred = bxor(x, y)
legacy_secure_compare(left, right, acc ||| xorred)
end
defp legacy_secure_compare(<<x, left::binary>>, <<y, right::binary>>, acc) do
import Bitwise
xorred = bxor(x, y)
legacy_secure_compare(left, right, acc ||| xorred)
end

defp legacy_secure_compare(<<>>, <<>>, acc) do
acc === 0
end
defp legacy_secure_compare(<<>>, <<>>, acc) do
acc === 0
end

@doc """
Expand Down