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69 lines
2.1 KiB
69 lines
2.1 KiB
package app |
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import ( |
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"net/http" |
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"strings" |
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) |
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// GetRemoteFromReq retrieves the originating IP address of the client from |
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// an HTTP request, considering standard and non-standard proxy headers. |
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// |
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// # Parameters |
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// |
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// - r: The HTTP request object containing details of the client and |
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// routing information. |
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// |
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// # Return Values |
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// |
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// - rr: A string value representing the IP address of the originating |
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// remote client. |
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// |
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// # Expected behaviour |
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// |
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// The function first checks for the standardized "Forwarded" header (RFC 7239) |
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// to identify the original client IP. If that isn't available, it falls back to |
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// the "X-Forwarded-For" header. If both headers are absent, it defaults to |
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// using the request's RemoteAddr. |
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// |
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// For the "Forwarded" header, it extracts the client IP from the "for" |
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// parameter. For the "X-Forwarded-For" header, if it contains one IP, it |
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// returns that. If it contains two IPs, it returns the second. |
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func GetRemoteFromReq(r *http.Request) (rr string) { |
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// First check for the standardized Forwarded header (RFC 7239) |
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forwarded := r.Header.Get("Forwarded") |
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if forwarded != "" { |
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// Parse the Forwarded header which can contain multiple parameters |
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// |
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// Format: |
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// |
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// Forwarded: by=<identifier>;for=<identifier>;host=<host>;proto=<http|https> |
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parts := strings.Split(forwarded, ";") |
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for _, part := range parts { |
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part = strings.TrimSpace(part) |
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if strings.HasPrefix(part, "for=") { |
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// Extract the client IP from the "for" parameter |
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forValue := strings.TrimPrefix(part, "for=") |
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// Remove quotes if present |
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forValue = strings.Trim(forValue, "\"") |
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// Handle IPv6 addresses which are enclosed in square brackets |
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forValue = strings.Trim(forValue, "[]") |
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return forValue |
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} |
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} |
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} |
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// If the Forwarded header is not available or doesn't contain "for" |
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// parameter, fall back to X-Forwarded-For |
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rem := r.Header.Get("X-Forwarded-For") |
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if rem == "" { |
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rr = r.RemoteAddr |
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} else { |
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splitted := strings.Split(rem, " ") |
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if len(splitted) == 1 { |
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rr = splitted[0] |
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} |
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if len(splitted) == 2 { |
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rr = splitted[1] |
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} |
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} |
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return |
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}
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