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Upstream proxy server

Thomas | Last updated: Jul 15, 2022 12:11PM UTC

Hello, I setup an upstream proxy server "username:password@proxy:port" and when I run "curl --proxy username:password@proxy:port ifconfig.io" nothing is intercepted. Can you please help? Thank you.

Michelle, PortSwigger Agent | Last updated: Jul 15, 2022 01:25PM UTC

Thanks for your message. Can I confirm some details about your configuration, please? - Does the machine where Burp is running have direct access to the internet? If so are you trying to achieve the following flow for the request? Request sent via cURL -> Burp -> Internet - Or do you have to use a proxy server to be able to browse the internet normally? In which case would the flow of the traffic be as follows? Request sent via cURL -> Burp -> Proxy Server -> Internet

Thomas | Last updated: Jul 15, 2022 02:02PM UTC

Hello, Michelle, Yes the machine has a direct connection to the internet. I am trying to achieve the following flow: Request sent via cURL -> Burp -> Internet

Michelle, PortSwigger Agent | Last updated: Jul 15, 2022 03:25PM UTC

If you are trying to achieve the following flow: Request sent via cURL -> Burp -> Internet You will need to enter the details for Burp's Proxy Listener in the cURL command: curl --proxy <IP_of_Burp_Proxy_Listener>:<Port_forBurp_Proxy_Listener> <Target_site_URL> e.g. curl --proxy 127.0.0.1:8080 http://portswigger-labs.net I hope this helps.

Thomas | Last updated: Jul 15, 2022 03:31PM UTC

Thank you. That solve the issue. :) What if I'd like to achieve this flow: Request sent via cURL -> Burp -> Proxy Server -> Internet ?

Michelle, PortSwigger Agent | Last updated: Jul 15, 2022 03:39PM UTC

If you wanted to use the following flow: cURL -> Burp -> Proxy Server -> Internet Your cURL command would remain the same but in Burp you would need to go to the User Options -> Connections tab and fill in the details for the proxy server that you want BUrp to send connections to under the 'Upstream proxy servers' section.

Thomas | Last updated: Jul 15, 2022 03:55PM UTC

I tried it, but it doesn't work. Can you please help?

Thomas | Last updated: Jul 15, 2022 03:55PM UTC

Nothing is intercepted by burp.

Michelle, PortSwigger Agent | Last updated: Jul 18, 2022 07:50AM UTC

Can you confirm the command you used in cURL, please? The cURL setup would be the same as if you were using the flow cURL -> Burp -> Proxy Server -> Internet. Can you also please confirm the details you have added to User Options -> Connections -> Upstream Proxy Server? If you use those same settings directly in a browser, do your requests go via your proxy server?

Sargent | Last updated: Jul 20, 2022 04:31PM UTC

Hello, I am new to Burp and asking the same question. The upstream proxy doesn't work when I tried to run "curl --proxy ar12:lg34jv00@us-wa.proxymesh.com:31280 ifconfig.io". It is not intercepting any traffic and it returns a weird response on terminal. I have the same issue as Thomas.

Michelle, PortSwigger Agent | Last updated: Jul 21, 2022 08:23AM UTC

The cURL command you are using would send the request using the following flow: Request sent via cURL -> Proxy Server -> Internet If you wanted to send the request to Burp, so you had the following flow: Request sent via cURL -> Burp -> Internet You will need to enter the details for Burp's Proxy Listener in the cURL command: curl --proxy <IP_of_Burp_Proxy_Listener>:<Port_forBurp_Proxy_Listener> <Target_site_URL> If you wanted to send the request to Burp and then to the upstream proxy, so you had the following flow: Request sent via cURL Burp -> Proxy Server -> Internet You would still need to tell cURL to send the request to Burp, so your cURL command would remain the same: curl --proxy <IP_of_Burp_Proxy_Listener>:<Port_forBurp_Proxy_Listener> <Target_site_URL> You would need to set the details for the upstream proxy server in Burp under User Options -> Connections -> Upstream Proxy Server in Burp. I hope this helps.

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