Paul Payne
518cdbbce5
Adds Pi-hole-style DNS filtering using dnsmasq's native address=/ directives, which block domains and all subdomains. Users subscribe to blocklists by URL or upload files, with suggested lists from Hagezi, Steven Black, and OISD. Background runner refreshes lists on a configurable interval (default 24h).
90 lines
2.2 KiB
Go
90 lines
2.2 KiB
Go
package dnsfilter
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import (
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"bufio"
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"net"
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"os"
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"strings"
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)
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// ParseLine extracts a domain from a single blocklist line.
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// Handles hosts format (0.0.0.0 domain), dnsmasq format (address=/domain/...),
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// and plain domain lists. Returns empty string and false for unparseable lines.
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func ParseLine(line string) (string, bool) {
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line = strings.TrimSpace(line)
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if line == "" || line[0] == '#' || line[0] == '!' {
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return "", false
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}
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// dnsmasq format: address=/domain/0.0.0.0 or server=/domain/
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if strings.HasPrefix(line, "address=/") || strings.HasPrefix(line, "server=/") {
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parts := strings.SplitN(line, "/", 4)
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if len(parts) >= 3 && parts[1] != "" {
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return validateDomain(parts[1])
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}
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return "", false
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}
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// Hosts format: 0.0.0.0 domain or 127.0.0.1 domain
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fields := strings.Fields(line)
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if len(fields) >= 2 {
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ip := fields[0]
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if ip == "0.0.0.0" || ip == "127.0.0.1" || ip == "::1" || ip == "::0" {
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domain := fields[1]
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// Strip inline comments
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if i := strings.IndexByte(domain, '#'); i >= 0 {
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domain = domain[:i]
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}
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return validateDomain(domain)
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}
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}
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// Plain domain format: one domain per line
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if len(fields) == 1 {
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return validateDomain(fields[0])
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}
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return "", false
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}
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// validateDomain checks that a string looks like a valid domain for blocking.
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func validateDomain(d string) (string, bool) {
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d = strings.ToLower(strings.TrimSpace(d))
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if d == "" || !strings.Contains(d, ".") {
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return "", false
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}
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// Reject known non-domains
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switch d {
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case "localhost", "localhost.localdomain", "local", "broadcasthost",
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"ip6-localhost", "ip6-loopback", "ip6-localnet",
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"ip6-mcastprefix", "ip6-allnodes", "ip6-allrouters":
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return "", false
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}
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// Reject IP addresses
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if net.ParseIP(d) != nil {
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return "", false
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}
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return d, true
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}
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// ParseFile reads a cached blocklist file and returns all unique domains.
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func ParseFile(path string) (map[string]struct{}, error) {
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f, err := os.Open(path)
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if err != nil {
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return nil, err
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}
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defer f.Close()
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domains := make(map[string]struct{})
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scanner := bufio.NewScanner(f)
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for scanner.Scan() {
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if domain, ok := ParseLine(scanner.Text()); ok {
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domains[domain] = struct{}{}
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}
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}
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return domains, scanner.Err()
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}
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