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feat: Implemented support for X-Forwarded-For header created by jghaanstra and hajimAIM #9

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feat: Implemented support for X-Forwarded-For header created by jghaanstra and hajimAIM #9

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8123a2a
feat: Implemented support for X-Forwarded-For header created by jghaa…
Sep 20, 2025
86d7f6d
config: Make clientIPHeader optional with secure defaults
Sep 20, 2025
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70 changes: 64 additions & 6 deletions main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,14 +5,16 @@ import (
"context"
"encoding/json"
"fmt"
"net"
"net/http"
"strings"
)

type Config struct {
APIBaseUrl string `json:"apiBaseUrl"`
UserSessionCookieName string `json:"userSessionCookieName"`
ResourceSessionRequestParam string `json:"resourceSessionRequestParam"`
APIBaseUrl string `json:"apiBaseUrl"`
UserSessionCookieName string `json:"userSessionCookieName"`
ResourceSessionRequestParam string `json:"resourceSessionRequestParam"`
ClientIPHeader *string `json:"clientIpHeader,omitempty"`
}

type Badger struct {
Expand All @@ -21,6 +23,7 @@ type Badger struct {
apiBaseUrl string
userSessionCookieName string
resourceSessionRequestParam string
clientIPHeader *string
}

type VerifyBody struct {
Expand Down Expand Up @@ -72,19 +75,20 @@ func New(ctx context.Context, next http.Handler, config *Config, name string) (h
apiBaseUrl: config.APIBaseUrl,
userSessionCookieName: config.UserSessionCookieName,
resourceSessionRequestParam: config.ResourceSessionRequestParam,
clientIPHeader: config.ClientIPHeader,
}, nil
}

func (p *Badger) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
cookies := p.extractCookies(req)

clientIP := p.getClientIP(req)
queryValues := req.URL.Query()

if sessionRequestValue := queryValues.Get(p.resourceSessionRequestParam); sessionRequestValue != "" {
body := ExchangeSessionBody{
RequestToken: &sessionRequestValue,
RequestHost: &req.Host,
RequestIP: &req.RemoteAddr,
RequestIP: clientIP,
}

jsonData, err := json.Marshal(body)
Expand Down Expand Up @@ -160,7 +164,7 @@ func (p *Badger) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
RequestPath: &req.URL.Path,
RequestMethod: &req.Method,
TLS: req.TLS != nil,
RequestIP: &req.RemoteAddr,
RequestIP: clientIP,
Headers: headers,
Query: queryParams,
}
Expand Down Expand Up @@ -250,3 +254,57 @@ func (p *Badger) getScheme(req *http.Request) string {
}
return "http"
}

func (p *Badger) getClientIP(req *http.Request) *string {
// If no specific header is configured, use remote address (safe default)
if p.clientIPHeader == nil || *p.clientIPHeader == "" {
remoteIP, _, err := net.SplitHostPort(req.RemoteAddr)
if err != nil {
// If SplitHostPort fails, assume req.RemoteAddr is just an IP
remoteIP = req.RemoteAddr
}
return &remoteIP
}

// Get the specified header value
headerValue := req.Header.Get(*p.clientIPHeader)
if headerValue == "" {
// Header not found, fallback to remote address
remoteIP, _, err := net.SplitHostPort(req.RemoteAddr)
if err != nil {
remoteIP = req.RemoteAddr
}
return &remoteIP
}

// Special handling for X-Forwarded-For header (contains comma-separated IPs)
if strings.ToLower(*p.clientIPHeader) == "x-forwarded-for" {
// X-Forwarded-For can contain multiple IPs: "client, proxy1, proxy2"
// The first one should be the original client IP
ips := strings.Split(headerValue, ",")
for _, ip := range ips {
ip = strings.TrimSpace(ip)
if parsedIP := net.ParseIP(ip); parsedIP != nil {
return &ip
}
}
// If no valid IP found in X-Forwarded-For, fallback to remote address
remoteIP, _, err := net.SplitHostPort(req.RemoteAddr)
if err != nil {
remoteIP = req.RemoteAddr
}
return &remoteIP
}

// For any other header, validate it's a valid IP and return it
if parsedIP := net.ParseIP(headerValue); parsedIP != nil {
return &headerValue
}

// Invalid IP in header, fallback to remote address
remoteIP, _, err := net.SplitHostPort(req.RemoteAddr)
if err != nil {
remoteIP = req.RemoteAddr
}
return &remoteIP
}