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# actually-proxed
### Challenge Description
### Challenge Attachment
{% file src="/files/ozefl3XfYXO8PvdXLUav" %}
let's send the request to burp repeater
let's view the source code
the secret server code is the same as the code in the previous challenge **proxed**
which untrusts all IP values except **`31.33.33.7`**
let's try to modify the originating IP to 31.33.33.7 using X-Forwarded-For Header
but it didn't work
and this is because of the reverse proxy implemented which overwrites the value of the X-Forwarded-For header to the value of the clientIp
the code between the red rectangle its purpose is to modify the `X-Forwarded-For` header in the HTTP request to include the client's IP address.
Here's what it does:
1. It loops through the `headers` slice, which contains pairs of HTTP header names and values.
2. For each header, it checks if the header name, when converted to lowercase with `strings.ToLower(v[0])`, matches the string `"x-forwarded-for"` in a case-insensitive manner.
3. If it finds a match, it modifies the header value by appending the client's IP address to it. It uses `fmt.Sprintf` to format the new header value as a comma-separated list of IP addresses, with the client's IP followed by any existing values.
4. The loop terminates as soon as it finds and modifies the `X-Forwarded-For` header.
since The loop terminates as soon as it finds and modifies the `X-Forwarded-For` header if we add `X-Forwarded-For` header multiple times, only the first occurrence will be processed, and subsequent occurrences will not be checked or modified by the proxy server.
this way we can make the originating IP value 31.33.33.7 and as a result we will not be blocked and we will eventually get the flag
### Flag
```
DUCTF{y0ur_c0d3_15_n07_b3773r_7h4n_7h3_574nd4rd_l1b}
```