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Reject non-FQDN SNI values #129

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merged 1 commit into from
Sep 18, 2024
Merged

Reject non-FQDN SNI values #129

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5 changes: 5 additions & 0 deletions pkg/https.go
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,11 @@ func handleTLS(c *Config, conn net.Conn, httpslog zerolog.Logger) error {
httpslog.Err(err)
return err
}
if !isValidFQDN(sni) {
httpslog.Warn().Msgf("Invalid SNI: %s", sni)
conn.Close()
return nil
}
connInfo := acl.ConnInfo{
SrcIP: conn.RemoteAddr(),
Domain: sni,
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12 changes: 11 additions & 1 deletion pkg/https_sni.go
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,10 @@

package sniproxy

import "fmt"
import (
"fmt"
"regexp"
)

var tlsHeaderLength = 5

Expand Down Expand Up @@ -147,4 +150,11 @@ func getExtensionBlock(data []byte) ([]byte, error) {
return data[index:], nil
}

// isValidFQDN validates if the given hostname is a valid FQDN
func isValidFQDN(hostname string) bool {
// Regular expression to match a valid FQDN
var fqdnRegex = regexp.MustCompile(`^(?i:[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?\.)+(?:[a-z]{2,})$`)
return fqdnRegex.MatchString(hostname)
}

// vim: foldmethod=marker