Revert drop 2.5, 2.6 support

Author: ydah

.github/workflows/test.yml

@@ -46,6 +46,10 @@ jobs:
           - gemfiles/standalone.gemfile
         experimental: [false]
         include:
+          - os: ubuntu-latest
+            ruby: "2.5"
+            gemfile: gemfiles/openssl.gemfile
+            experimental: false
           - os: ubuntu-latest
             ruby: "truffleruby-head"
             gemfile: "gemfiles/standalone.gemfile"

lib/jwt/jwa/ecdsa.rb

@@ -98,7 +98,7 @@ def curve_by_name(name)
       def raw_to_asn1(signature, private_key)
         byte_size = (private_key.group.degree + 7) / 8
         sig_bytes = signature[0..(byte_size - 1)]
-        sig_char = signature[byte_size..] || ''
+        sig_char = signature[byte_size..-1] || ''
         OpenSSL::ASN1::Sequence.new([sig_bytes, sig_char].map { |int| OpenSSL::ASN1::Integer.new(OpenSSL::BN.new(int, 2)) }).to_der
       end