AdGuardHome/internal/dnsforward/http.go

714 lines
20 KiB
Go

package dnsforward
import (
"encoding/json"
"fmt"
"net"
"net/http"
"strings"
"time"
"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
"github.com/AdguardTeam/dnsproxy/proxy"
"github.com/AdguardTeam/dnsproxy/upstream"
"github.com/AdguardTeam/golibs/errors"
"github.com/AdguardTeam/golibs/log"
"github.com/AdguardTeam/golibs/netutil"
"github.com/AdguardTeam/golibs/stringutil"
"github.com/miekg/dns"
"golang.org/x/exp/maps"
"golang.org/x/exp/slices"
)
// jsonDNSConfig is the JSON representation of the DNS server configuration.
type jsonDNSConfig struct {
Upstreams *[]string `json:"upstream_dns"`
UpstreamsFile *string `json:"upstream_dns_file"`
Bootstraps *[]string `json:"bootstrap_dns"`
ProtectionEnabled *bool `json:"protection_enabled"`
RateLimit *uint32 `json:"ratelimit"`
BlockingMode *BlockingMode `json:"blocking_mode"`
EDNSCSEnabled *bool `json:"edns_cs_enabled"`
DNSSECEnabled *bool `json:"dnssec_enabled"`
DisableIPv6 *bool `json:"disable_ipv6"`
UpstreamMode *string `json:"upstream_mode"`
CacheSize *uint32 `json:"cache_size"`
CacheMinTTL *uint32 `json:"cache_ttl_min"`
CacheMaxTTL *uint32 `json:"cache_ttl_max"`
CacheOptimistic *bool `json:"cache_optimistic"`
ResolveClients *bool `json:"resolve_clients"`
UsePrivateRDNS *bool `json:"use_private_ptr_resolvers"`
LocalPTRUpstreams *[]string `json:"local_ptr_upstreams"`
BlockingIPv4 net.IP `json:"blocking_ipv4"`
BlockingIPv6 net.IP `json:"blocking_ipv6"`
}
func (s *Server) getDNSConfig() (c *jsonDNSConfig) {
s.serverLock.RLock()
defer s.serverLock.RUnlock()
upstreams := stringutil.CloneSliceOrEmpty(s.conf.UpstreamDNS)
upstreamFile := s.conf.UpstreamDNSFileName
bootstraps := stringutil.CloneSliceOrEmpty(s.conf.BootstrapDNS)
protectionEnabled := s.conf.ProtectionEnabled
blockingMode := s.conf.BlockingMode
blockingIPv4 := s.conf.BlockingIPv4
blockingIPv6 := s.conf.BlockingIPv6
ratelimit := s.conf.Ratelimit
enableEDNSClientSubnet := s.conf.EnableEDNSClientSubnet
enableDNSSEC := s.conf.EnableDNSSEC
aaaaDisabled := s.conf.AAAADisabled
cacheSize := s.conf.CacheSize
cacheMinTTL := s.conf.CacheMinTTL
cacheMaxTTL := s.conf.CacheMaxTTL
cacheOptimistic := s.conf.CacheOptimistic
resolveClients := s.conf.ResolveClients
usePrivateRDNS := s.conf.UsePrivateRDNS
localPTRUpstreams := stringutil.CloneSliceOrEmpty(s.conf.LocalPTRResolvers)
var upstreamMode string
if s.conf.FastestAddr {
upstreamMode = "fastest_addr"
} else if s.conf.AllServers {
upstreamMode = "parallel"
}
return &jsonDNSConfig{
Upstreams: &upstreams,
UpstreamsFile: &upstreamFile,
Bootstraps: &bootstraps,
ProtectionEnabled: &protectionEnabled,
BlockingMode: &blockingMode,
BlockingIPv4: blockingIPv4,
BlockingIPv6: blockingIPv6,
RateLimit: &ratelimit,
EDNSCSEnabled: &enableEDNSClientSubnet,
DNSSECEnabled: &enableDNSSEC,
DisableIPv6: &aaaaDisabled,
CacheSize: &cacheSize,
CacheMinTTL: &cacheMinTTL,
CacheMaxTTL: &cacheMaxTTL,
CacheOptimistic: &cacheOptimistic,
UpstreamMode: &upstreamMode,
ResolveClients: &resolveClients,
UsePrivateRDNS: &usePrivateRDNS,
LocalPTRUpstreams: &localPTRUpstreams,
}
}
func (s *Server) handleGetConfig(w http.ResponseWriter, r *http.Request) {
defLocalPTRUps, err := s.filterOurDNSAddrs(s.sysResolvers.Get())
if err != nil {
log.Debug("getting dns configuration: %s", err)
}
resp := struct {
jsonDNSConfig
// DefautLocalPTRUpstreams is used to pass the addresses from
// systemResolvers to the front-end. It's not a pointer to the slice
// since there is no need to omit it while decoding from JSON.
DefautLocalPTRUpstreams []string `json:"default_local_ptr_upstreams,omitempty"`
}{
jsonDNSConfig: *s.getDNSConfig(),
DefautLocalPTRUpstreams: defLocalPTRUps,
}
_ = aghhttp.WriteJSONResponse(w, r, resp)
}
func (req *jsonDNSConfig) checkBlockingMode() (err error) {
if req.BlockingMode == nil {
return nil
}
return validateBlockingMode(*req.BlockingMode, req.BlockingIPv4, req.BlockingIPv6)
}
func (req *jsonDNSConfig) checkUpstreamsMode() bool {
valid := []string{"", "fastest_addr", "parallel"}
return req.UpstreamMode == nil || stringutil.InSlice(valid, *req.UpstreamMode)
}
func (req *jsonDNSConfig) checkBootstrap() (err error) {
if req.Bootstraps == nil {
return nil
}
var b string
defer func() { err = errors.Annotate(err, "checking bootstrap %s: invalid address: %w", b) }()
for _, b = range *req.Bootstraps {
if b == "" {
return errors.Error("empty")
}
if _, err = upstream.NewResolver(b, nil); err != nil {
return err
}
}
return nil
}
// validate returns an error if any field of req is invalid.
func (req *jsonDNSConfig) validate(privateNets netutil.SubnetSet) (err error) {
if req.Upstreams != nil {
err = ValidateUpstreams(*req.Upstreams)
if err != nil {
return fmt.Errorf("validating upstream servers: %w", err)
}
}
if req.LocalPTRUpstreams != nil {
err = ValidateUpstreamsPrivate(*req.LocalPTRUpstreams, privateNets)
if err != nil {
return fmt.Errorf("validating private upstream servers: %w", err)
}
}
err = req.checkBootstrap()
if err != nil {
return err
}
err = req.checkBlockingMode()
if err != nil {
return err
}
switch {
case !req.checkUpstreamsMode():
return errors.Error("upstream_mode: incorrect value")
case !req.checkCacheTTL():
return errors.Error("cache_ttl_min must be less or equal than cache_ttl_max")
default:
return nil
}
}
func (req *jsonDNSConfig) checkCacheTTL() bool {
if req.CacheMinTTL == nil && req.CacheMaxTTL == nil {
return true
}
var min, max uint32
if req.CacheMinTTL != nil {
min = *req.CacheMinTTL
}
if req.CacheMaxTTL != nil {
max = *req.CacheMaxTTL
}
return min <= max
}
func (s *Server) handleSetConfig(w http.ResponseWriter, r *http.Request) {
req := &jsonDNSConfig{}
err := json.NewDecoder(r.Body).Decode(req)
if err != nil {
aghhttp.Error(r, w, http.StatusBadRequest, "decoding request: %s", err)
return
}
err = req.validate(s.privateNets)
if err != nil {
aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
return
}
restart := s.setConfig(req)
s.conf.ConfigModified()
if restart {
err = s.Reconfigure(nil)
if err != nil {
aghhttp.Error(r, w, http.StatusInternalServerError, "%s", err)
}
}
}
// setConfigRestartable sets the server parameters. shouldRestart is true if
// the server should be restarted to apply changes.
func (s *Server) setConfig(dc *jsonDNSConfig) (shouldRestart bool) {
s.serverLock.Lock()
defer s.serverLock.Unlock()
if dc.BlockingMode != nil {
s.conf.BlockingMode = *dc.BlockingMode
if *dc.BlockingMode == BlockingModeCustomIP {
s.conf.BlockingIPv4 = dc.BlockingIPv4.To4()
s.conf.BlockingIPv6 = dc.BlockingIPv6.To16()
}
}
if dc.UpstreamMode != nil {
s.conf.AllServers = *dc.UpstreamMode == "parallel"
s.conf.FastestAddr = *dc.UpstreamMode == "fastest_addr"
}
setIfNotNil(&s.conf.ProtectionEnabled, dc.ProtectionEnabled)
setIfNotNil(&s.conf.EnableDNSSEC, dc.DNSSECEnabled)
setIfNotNil(&s.conf.AAAADisabled, dc.DisableIPv6)
setIfNotNil(&s.conf.ResolveClients, dc.ResolveClients)
setIfNotNil(&s.conf.UsePrivateRDNS, dc.UsePrivateRDNS)
return s.setConfigRestartable(dc)
}
// setIfNotNil sets the value pointed at by currentPtr to the value pointed at
// by newPtr if newPtr is not nil. currentPtr must not be nil.
func setIfNotNil[T any](currentPtr, newPtr *T) (hasSet bool) {
if newPtr == nil {
return false
}
*currentPtr = *newPtr
return true
}
// setConfigRestartable sets the parameters which trigger a restart.
// shouldRestart is true if the server should be restarted to apply changes.
// s.serverLock is expected to be locked.
func (s *Server) setConfigRestartable(dc *jsonDNSConfig) (shouldRestart bool) {
for _, hasSet := range []bool{
setIfNotNil(&s.conf.UpstreamDNS, dc.Upstreams),
setIfNotNil(&s.conf.LocalPTRResolvers, dc.LocalPTRUpstreams),
setIfNotNil(&s.conf.UpstreamDNSFileName, dc.UpstreamsFile),
setIfNotNil(&s.conf.BootstrapDNS, dc.Bootstraps),
setIfNotNil(&s.conf.EnableEDNSClientSubnet, dc.EDNSCSEnabled),
setIfNotNil(&s.conf.CacheSize, dc.CacheSize),
setIfNotNil(&s.conf.CacheMinTTL, dc.CacheMinTTL),
setIfNotNil(&s.conf.CacheMaxTTL, dc.CacheMaxTTL),
setIfNotNil(&s.conf.CacheOptimistic, dc.CacheOptimistic),
} {
shouldRestart = shouldRestart || hasSet
if shouldRestart {
break
}
}
if dc.RateLimit != nil && s.conf.Ratelimit != *dc.RateLimit {
s.conf.Ratelimit = *dc.RateLimit
shouldRestart = true
}
return shouldRestart
}
// upstreamJSON is a request body for handleTestUpstreamDNS endpoint.
type upstreamJSON struct {
Upstreams []string `json:"upstream_dns"`
BootstrapDNS []string `json:"bootstrap_dns"`
PrivateUpstreams []string `json:"private_upstream"`
}
// IsCommentOrEmpty returns true if s starts with a "#" character or is empty.
// This function is useful for filtering out non-upstream lines from upstream
// configs.
func IsCommentOrEmpty(s string) (ok bool) {
return len(s) == 0 || s[0] == '#'
}
// newUpstreamConfig validates upstreams and returns an appropriate upstream
// configuration or nil if it can't be built.
//
// TODO(e.burkov): Perhaps proxy.ParseUpstreamsConfig should validate upstreams
// slice already so that this function may be considered useless.
func newUpstreamConfig(upstreams []string) (conf *proxy.UpstreamConfig, err error) {
// No need to validate comments and empty lines.
upstreams = stringutil.FilterOut(upstreams, IsCommentOrEmpty)
if len(upstreams) == 0 {
// Consider this case valid since it means the default server should be
// used.
return nil, nil
}
for _, u := range upstreams {
var ups string
var domains []string
ups, domains, err = separateUpstream(u)
if err != nil {
// Don't wrap the error since it's informative enough as is.
return nil, err
}
_, err = validateUpstream(ups, domains)
if err != nil {
return nil, fmt.Errorf("validating upstream %q: %w", u, err)
}
}
conf, err = proxy.ParseUpstreamsConfig(
upstreams,
&upstream.Options{
Bootstrap: []string{},
Timeout: DefaultTimeout,
},
)
if err != nil {
return nil, err
} else if len(conf.Upstreams) == 0 {
return nil, errors.Error("no default upstreams specified")
}
return conf, nil
}
// ValidateUpstreams validates each upstream and returns an error if any
// upstream is invalid or if there are no default upstreams specified.
//
// TODO(e.burkov): Move into aghnet or even into dnsproxy.
func ValidateUpstreams(upstreams []string) (err error) {
_, err = newUpstreamConfig(upstreams)
return err
}
// ValidateUpstreamsPrivate validates each upstream and returns an error if any
// upstream is invalid or if there are no default upstreams specified. It also
// checks each domain of domain-specific upstreams for being ARPA pointing to
// a locally-served network. privateNets must not be nil.
func ValidateUpstreamsPrivate(upstreams []string, privateNets netutil.SubnetSet) (err error) {
conf, err := newUpstreamConfig(upstreams)
if err != nil {
return err
}
if conf == nil {
return nil
}
keys := maps.Keys(conf.DomainReservedUpstreams)
slices.Sort(keys)
var errs []error
for _, domain := range keys {
var subnet *net.IPNet
subnet, err = netutil.SubnetFromReversedAddr(domain)
if err != nil {
errs = append(errs, err)
continue
}
if !privateNets.Contains(subnet.IP) {
errs = append(
errs,
fmt.Errorf("arpa domain %q should point to a locally-served network", domain),
)
}
}
if len(errs) > 0 {
return errors.List("checking domain-specific upstreams", errs...)
}
return nil
}
var protocols = []string{
"h3://",
"https://",
"quic://",
"sdns://",
"tcp://",
"tls://",
"udp://",
}
// validateUpstream returns an error if u alongside with domains is not a valid
// upstream configuration. useDefault is true if the upstream is
// domain-specific and is configured to point at the default upstream server
// which is validated separately. The upstream is considered domain-specific
// only if domains is at least not nil.
func validateUpstream(u string, domains []string) (useDefault bool, err error) {
// The special server address '#' means that default server must be used.
if useDefault = u == "#" && domains != nil; useDefault {
return useDefault, nil
}
// Check if the upstream has a valid protocol prefix.
//
// TODO(e.burkov): Validate the domain name.
for _, proto := range protocols {
if strings.HasPrefix(u, proto) {
return useDefault, nil
}
}
if strings.Contains(u, "://") {
return useDefault, errors.Error("wrong protocol")
}
// Check if upstream is either an IP or IP with port.
if net.ParseIP(u) != nil {
return useDefault, nil
} else if _, err = netutil.ParseIPPort(u); err != nil {
return useDefault, err
}
return useDefault, nil
}
// separateUpstream returns the upstream and the specified domains. domains is
// nil when the upstream is not domains-specific. Otherwise it may also be
// empty.
func separateUpstream(upstreamStr string) (ups string, domains []string, err error) {
if !strings.HasPrefix(upstreamStr, "[/") {
return upstreamStr, nil, nil
}
defer func() { err = errors.Annotate(err, "bad upstream for domain %q: %w", upstreamStr) }()
parts := strings.Split(upstreamStr[2:], "/]")
switch len(parts) {
case 2:
// Go on.
case 1:
return "", nil, errors.Error("missing separator")
default:
return "", []string{}, errors.Error("duplicated separator")
}
for i, host := range strings.Split(parts[0], "/") {
if host == "" {
continue
}
err = netutil.ValidateDomainName(strings.TrimPrefix(host, "*."))
if err != nil {
return "", domains, fmt.Errorf("domain at index %d: %w", i, err)
}
domains = append(domains, host)
}
return parts[1], domains, nil
}
// healthCheckFunc is a signature of function to check if upstream exchanges
// properly.
type healthCheckFunc func(u upstream.Upstream) (err error)
// checkDNSUpstreamExc checks if the DNS upstream exchanges correctly.
func checkDNSUpstreamExc(u upstream.Upstream) (err error) {
// testTLD is the special-use fully-qualified domain name for testing the
// DNS server reachability.
//
// See https://datatracker.ietf.org/doc/html/rfc6761#section-6.2.
const testTLD = "test."
req := &dns.Msg{
MsgHdr: dns.MsgHdr{
Id: dns.Id(),
RecursionDesired: true,
},
Question: []dns.Question{{
Name: testTLD,
Qtype: dns.TypeA,
Qclass: dns.ClassINET,
}},
}
var reply *dns.Msg
reply, err = u.Exchange(req)
if err != nil {
return fmt.Errorf("couldn't communicate with upstream: %w", err)
} else if len(reply.Answer) != 0 {
return errors.Error("wrong response")
}
return nil
}
// checkPrivateUpstreamExc checks if the upstream for resolving private
// addresses exchanges correctly.
//
// TODO(e.burkov): Think about testing the ip6.arpa. as well.
func checkPrivateUpstreamExc(u upstream.Upstream) (err error) {
// inAddrArpaTLD is the special-use fully-qualified domain name for PTR IP
// address resolution.
//
// See https://datatracker.ietf.org/doc/html/rfc1035#section-3.5.
const inAddrArpaTLD = "in-addr.arpa."
req := &dns.Msg{
MsgHdr: dns.MsgHdr{
Id: dns.Id(),
RecursionDesired: true,
},
Question: []dns.Question{{
Name: inAddrArpaTLD,
Qtype: dns.TypePTR,
Qclass: dns.ClassINET,
}},
}
if _, err = u.Exchange(req); err != nil {
return fmt.Errorf("couldn't communicate with upstream: %w", err)
}
return nil
}
// domainSpecificTestError is a wrapper for errors returned by checkDNS to mark
// the tested upstream domain-specific and therefore consider its errors
// non-critical.
//
// TODO(a.garipov): Some common mechanism of distinguishing between errors and
// warnings (non-critical errors) is desired.
type domainSpecificTestError struct {
error
}
// checkDNS checks the upstream server defined by upstreamConfigStr using
// healthCheck for actually exchange messages. It uses bootstrap to resolve the
// upstream's address.
func checkDNS(
upstreamConfigStr string,
bootstrap []string,
timeout time.Duration,
healthCheck healthCheckFunc,
) (err error) {
if IsCommentOrEmpty(upstreamConfigStr) {
return nil
}
// Separate upstream from domains list.
upstreamAddr, domains, err := separateUpstream(upstreamConfigStr)
if err != nil {
return fmt.Errorf("wrong upstream format: %w", err)
}
useDefault, err := validateUpstream(upstreamAddr, domains)
if err != nil {
return fmt.Errorf("wrong upstream format: %w", err)
} else if useDefault {
return nil
}
if len(bootstrap) == 0 {
bootstrap = defaultBootstrap
}
log.Debug("dnsforward: checking if upstream %q works", upstreamAddr)
u, err := upstream.AddressToUpstream(upstreamAddr, &upstream.Options{
Bootstrap: bootstrap,
Timeout: timeout,
})
if err != nil {
return fmt.Errorf("failed to choose upstream for %q: %w", upstreamAddr, err)
}
if err = healthCheck(u); err != nil {
err = fmt.Errorf("upstream %q fails to exchange: %w", upstreamAddr, err)
if domains != nil {
return domainSpecificTestError{error: err}
}
return err
}
log.Debug("dnsforward: upstream %q is ok", upstreamAddr)
return nil
}
func (s *Server) handleTestUpstreamDNS(w http.ResponseWriter, r *http.Request) {
req := &upstreamJSON{}
err := json.NewDecoder(r.Body).Decode(req)
if err != nil {
aghhttp.Error(r, w, http.StatusBadRequest, "Failed to read request body: %s", err)
return
}
result := map[string]string{}
bootstraps := req.BootstrapDNS
timeout := s.conf.UpstreamTimeout
for _, host := range req.Upstreams {
err = checkDNS(host, bootstraps, timeout, checkDNSUpstreamExc)
if err != nil {
log.Info("%v", err)
result[host] = err.Error()
if _, ok := err.(domainSpecificTestError); ok {
result[host] = fmt.Sprintf("WARNING: %s", result[host])
}
continue
}
result[host] = "OK"
}
for _, host := range req.PrivateUpstreams {
err = checkDNS(host, bootstraps, timeout, checkPrivateUpstreamExc)
if err != nil {
log.Info("%v", err)
// TODO(e.burkov): If passed upstream have already written an error
// above, we rewriting the error for it. These cases should be
// handled properly instead.
result[host] = err.Error()
if _, ok := err.(domainSpecificTestError); ok {
result[host] = fmt.Sprintf("WARNING: %s", result[host])
}
continue
}
result[host] = "OK"
}
_ = aghhttp.WriteJSONResponse(w, r, result)
}
// handleDoH is the DNS-over-HTTPs handler.
//
// Control flow:
//
// HTTP server
// -> dnsforward.handleDoH
// -> dnsforward.ServeHTTP
// -> proxy.ServeHTTP
// -> proxy.handleDNSRequest
// -> dnsforward.handleDNSRequest
func (s *Server) handleDoH(w http.ResponseWriter, r *http.Request) {
if !s.conf.TLSAllowUnencryptedDoH && r.TLS == nil {
aghhttp.Error(r, w, http.StatusNotFound, "Not Found")
return
}
if !s.IsRunning() {
aghhttp.Error(r, w, http.StatusInternalServerError, "dns server is not running")
return
}
s.ServeHTTP(w, r)
}
func (s *Server) registerHandlers() {
s.conf.HTTPRegister(http.MethodGet, "/control/dns_info", s.handleGetConfig)
s.conf.HTTPRegister(http.MethodPost, "/control/dns_config", s.handleSetConfig)
s.conf.HTTPRegister(http.MethodPost, "/control/test_upstream_dns", s.handleTestUpstreamDNS)
s.conf.HTTPRegister(http.MethodGet, "/control/access/list", s.handleAccessList)
s.conf.HTTPRegister(http.MethodPost, "/control/access/set", s.handleAccessSet)
// Register both versions, with and without the trailing slash, to
// prevent a 301 Moved Permanently redirect when clients request the
// path without the trailing slash. Those redirects break some clients.
//
// See go doc net/http.ServeMux.
//
// See also https://github.com/AdguardTeam/AdGuardHome/issues/2628.
s.conf.HTTPRegister("", "/dns-query", s.handleDoH)
s.conf.HTTPRegister("", "/dns-query/", s.handleDoH)
}