# HG changeset patch # User Matthew Wild # Date 1664566711 -3600 # Node ID 62100f31eb8a25dab0f638f80ea0561568b253a9 # Parent 924bc1c8d0d9ec3c90b28a4d97008d62813ccd38 util.jwt: More robust ECDSA signature parsing, fail early on unexpected length diff -r 924bc1c8d0d9 -r 62100f31eb8a util/jwt.lua --- a/util/jwt.lua Fri Sep 30 00:27:10 2022 +0200 +++ b/util/jwt.lua Fri Sep 30 20:38:31 2022 +0100 @@ -141,8 +141,12 @@ return r..s; end + local expected_sig_length = sig_bytes*2; local function decode_ecdsa_sig(jwk_sig) - return crypto.build_ecdsa_signature(jwk_sig:sub(1, sig_bytes), jwk_sig:sub(sig_bytes+1, sig_bytes*2)); + if #jwk_sig ~= expected_sig_length then + return nil; + end + return crypto.build_ecdsa_signature(jwk_sig:sub(1, sig_bytes), jwk_sig:sub(sig_bytes+1)); end return new_crypto_algorithm(name, "id-ecPublicKey", c_sign, c_verify, encode_ecdsa_sig, decode_ecdsa_sig); end