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Original file line number | Diff line number | Diff line change |
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package dnsforward | ||
|
||
import ( | ||
"encoding/binary" | ||
"fmt" | ||
|
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"github.com/AdguardTeam/AdGuardHome/internal/aghnet" | ||
"github.com/AdguardTeam/dnsproxy/proxy" | ||
"github.com/AdguardTeam/golibs/errors" | ||
"github.com/AdguardTeam/golibs/log" | ||
"github.com/miekg/dns" | ||
) | ||
|
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// type check | ||
var _ proxy.BeforeRequestHandler = (*Server)(nil) | ||
|
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// HandleBefore is the handler that is called before any other processing, | ||
// including logs. It performs access checks and puts the client ID, if there | ||
// is one, into the server's cache. | ||
// | ||
// TODO(e.burkov): Write tests. | ||
func (s *Server) HandleBefore( | ||
_ *proxy.Proxy, | ||
pctx *proxy.DNSContext, | ||
) (err error) { | ||
clientID, err := s.clientIDFromDNSContext(pctx) | ||
if err != nil { | ||
return fmt.Errorf("getting clientid: %w", err) | ||
} | ||
|
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blocked, _ := s.IsBlockedClient(pctx.Addr.Addr(), clientID) | ||
if blocked { | ||
return s.preBlockedResponse(pctx) | ||
} | ||
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if len(pctx.Req.Question) == 1 { | ||
q := pctx.Req.Question[0] | ||
qt := q.Qtype | ||
host := aghnet.NormalizeDomain(q.Name) | ||
if s.access.isBlockedHost(host, qt) { | ||
log.Debug("access: request %s %s is in access blocklist", dns.Type(qt), host) | ||
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return s.preBlockedResponse(pctx) | ||
} | ||
} | ||
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if clientID != "" { | ||
key := [8]byte{} | ||
binary.BigEndian.PutUint64(key[:], pctx.RequestID) | ||
s.clientIDCache.Set(key[:], []byte(clientID)) | ||
} | ||
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return nil | ||
} | ||
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// clientIDFromDNSContext extracts the client's ID from the server name of the | ||
// client's DoT or DoQ request or the path of the client's DoH. If the protocol | ||
// is not one of these, clientID is an empty string and err is nil. | ||
func (s *Server) clientIDFromDNSContext(pctx *proxy.DNSContext) (clientID string, err error) { | ||
proto := pctx.Proto | ||
if proto == proxy.ProtoHTTPS { | ||
clientID, err = clientIDFromDNSContextHTTPS(pctx) | ||
if err != nil { | ||
return "", fmt.Errorf("checking url: %w", err) | ||
} else if clientID != "" { | ||
return clientID, nil | ||
} | ||
|
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// Go on and check the domain name as well. | ||
} else if proto != proxy.ProtoTLS && proto != proxy.ProtoQUIC { | ||
return "", nil | ||
} | ||
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hostSrvName := s.conf.ServerName | ||
if hostSrvName == "" { | ||
return "", nil | ||
} | ||
|
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cliSrvName, err := clientServerName(pctx, proto) | ||
if err != nil { | ||
return "", err | ||
} | ||
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clientID, err = clientIDFromClientServerName( | ||
hostSrvName, | ||
cliSrvName, | ||
s.conf.StrictSNICheck, | ||
) | ||
if err != nil { | ||
return "", fmt.Errorf("clientid check: %w", err) | ||
} | ||
|
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return clientID, nil | ||
} | ||
|
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// errAccessBlocked is a sentinel error returned when a request is blocked by | ||
// access settings. | ||
var errAccessBlocked errors.Error = "blocked by access settings" | ||
|
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// preBlockedResponse returns a protocol-appropriate response for a request that | ||
// was blocked by access settings. | ||
func (s *Server) preBlockedResponse(pctx *proxy.DNSContext) (err error) { | ||
if pctx.Proto == proxy.ProtoUDP || pctx.Proto == proxy.ProtoDNSCrypt { | ||
// Return nil so that dnsproxy drops the connection and thus | ||
// prevent DNS amplification attacks. | ||
return errAccessBlocked | ||
} | ||
|
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return &proxy.BeforeRequestError{ | ||
Err: errAccessBlocked, | ||
Response: s.makeResponseREFUSED(pctx.Req), | ||
} | ||
} |
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