use md5

app/apis/wx_pay/api/mch.rb

@@ -81,7 +81,7 @@ def pay_micropay(out_trade_no:, auth_code:, body:, total_fee:, spbill_create_ip:
       opts.merge! sign: WxPay::Sign::Hmac.generate(opts, key: @mch.key)
 
       r = @client.with_options(origin: BASE, debug: Rails.logger.broadcasts[0].instance_values['logdev'].dev, debug_level: 2)
-          .post('pay/micropay', body: opts.to_xml(root: 'xml', skip_types: true, skip_instruct: true, dasherize: false))
+          .post('/pay/micropay', body: opts.to_xml(root: 'xml', skip_types: true, skip_instruct: true, dasherize: false))
       Hash.from_xml(r.to_s)['xml']
     end
 

app/apis/wx_pay/api/partner.rb

@@ -79,10 +79,10 @@ def pay_micropay(out_trade_no:, auth_code:, body:, total_fee:, spbill_create_ip:
         auth_code: auth_code,
         **v2_common_payee_params
       }
-      opts.merge! sign: WxPay::Sign::Hmac.generate(opts, key: @mch.key)
+      opts.merge! sign: WxPay::Sign::Hmac.generate_md5(opts, key: @mch.key)
 
       r = @client.with_options(origin: BASE, debug: Rails.logger.broadcasts[0].instance_values['logdev'].dev, debug_level: 2)
-          .post('pay/micropay', body: opts.to_xml(root: 'xml', skip_types: true, skip_instruct: true, dasherize: false))
+          .post('/pay/micropay', body: opts.to_xml(root: 'xml', skip_types: true, skip_instruct: true, dasherize: false))
       Hash.from_xml(r.to_s)['xml']
     end
 

app/apis/wx_pay/sign/hmac.rb

@@ -13,5 +13,14 @@ def generate(params, key:)
       OpenSSL::HMAC.hexdigest(OpenSSL::Digest.new('sha256'), key, string_sign_temp).upcase
     end
 
+    def generate_md5(params, key:)
+      query = params.compact_blank.sort.map.each do |k, v|
+        "#{k}=#{v}"
+      end.join('&')
+      string_sign_temp = "#{query}&key=#{key}"
+
+      Digest::MD5.hexdigest(string_sign_temp).upcase
+    end
+
   end
 end