70 lines
2.1 KiB
Go
70 lines
2.1 KiB
Go
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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