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fix: avoid a panic on a multi-byte UTF-8 SMTP reply line (remote DoS) #101

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Merged
evilsocket merged 1 commit into from
Jul 6, 2026
Merged

fix: avoid a panic on a multi-byte UTF-8 SMTP reply line (remote DoS) #101

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7 changes: 6 additions & 1 deletion src/plugins/smtp/ntlm.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,12 @@ async fn read_reply(channel: &mut Channel) -> Result<(u16, String), Error> {
if trimmed.len() < 3 {
return Err(format!("smtp: malformed reply line {:?}", trimmed));
}
let code: u16 = trimmed[..3]
// trimmed.len() >= 3 is a BYTE length, but trimmed[..3] is a byte-index slice that
// panics if byte 3 is not a UTF-8 char boundary (a multi-byte reply line from a
// malicious server). Use get(..3) so a bad boundary is a returned error, not a panic.
let code: u16 = trimmed
.get(..3)
.ok_or_else(|| format!("smtp: malformed reply line {:?}", trimmed))?
.parse()
.map_err(|e: std::num::ParseIntError| format!("smtp: bad reply code: {}", e))?;
// RFC 5321 §4.2: a continuation line uses '-' as the fourth char, the
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