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🛡️ Sentinel: [HIGH] Fix Header Injection #14

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🛡️ Sentinel: [HIGH] Fix Header Injection #14

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4 changes: 4 additions & 0 deletions .jules/sentinel.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
## 2023-10-12 - Header Injection via Environment Variables
**Vulnerability:** HTTP Response Splitting / Header Injection
**Learning:** `responder.Spec.Validate()` correctly prevents control characters in header values designed by the user. However, when these headers contain environment variable placeholders (`${VAR}`), `responder.Render()` expanded them *after* validation. An attacker could potentially inject arbitrary headers or split the response by manipulating an allowed environment variable to contain `\r\n`.
**Prevention:** Sanitized the expanded environment variable values in `Render()` by stripping `\r` and `\n` characters before adding them to the final response headers.
5 changes: 4 additions & 1 deletion internal/responder/responder.go
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Expand Up @@ -172,7 +172,10 @@ func (r *Responder) Render() events.Response {
s := r.Get()
headers := make([]events.Header, len(s.Headers))
for i, h := range s.Headers {
headers[i] = events.Header{Name: h.Name, Value: r.env.Expand(h.Value)}
val := r.env.Expand(h.Value)
val = strings.ReplaceAll(val, "\r", "")
val = strings.ReplaceAll(val, "\n", "")
headers[i] = events.Header{Name: h.Name, Value: val}
}
return events.Response{
Status: s.Status,
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