mirror of
https://github.com/DNSCrypt/dnscrypt-proxy.git
synced 2025-04-05 14:17:36 +03:00
297 lines
8.6 KiB
Go
297 lines
8.6 KiB
Go
package main
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import (
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"bytes"
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"fmt"
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"io/ioutil"
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"net/url"
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"os"
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"path/filepath"
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"strings"
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"time"
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"unicode"
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"github.com/dchest/safefile"
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"github.com/jedisct1/dlog"
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stamps "github.com/jedisct1/go-dnsstamps"
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"github.com/jedisct1/go-minisign"
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)
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type SourceFormat int
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const (
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SourceFormatV2 = iota
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)
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const (
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DefaultPrefetchDelay time.Duration = 24 * time.Hour
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MinimumPrefetchInterval time.Duration = 10 * time.Minute
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)
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type Source struct {
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name string
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urls []*url.URL
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format SourceFormat
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in []byte
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minisignKey *minisign.PublicKey
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cacheFile string
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cacheTTL, prefetchDelay time.Duration
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refresh time.Time
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}
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func (source *Source) checkSignature(bin, sig []byte) (err error) {
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var signature minisign.Signature
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if signature, err = minisign.DecodeSignature(string(sig)); err == nil {
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_, err = source.minisignKey.Verify(bin, signature)
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}
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return
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}
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// timeNow can be replaced by tests to provide a static value
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var timeNow = time.Now
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func (source *Source) fetchFromCache(now time.Time) (delay time.Duration, err error) {
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var bin, sig []byte
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if bin, err = ioutil.ReadFile(source.cacheFile); err != nil {
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return
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}
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if sig, err = ioutil.ReadFile(source.cacheFile + ".minisig"); err != nil {
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return
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}
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if err = source.checkSignature(bin, sig); err != nil {
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return
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}
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source.in = bin
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var fi os.FileInfo
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if fi, err = os.Stat(source.cacheFile); err != nil {
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return
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}
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if elapsed := now.Sub(fi.ModTime()); elapsed < source.cacheTTL {
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delay = source.prefetchDelay - elapsed
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dlog.Debugf("Source [%s] cache file [%s] is still fresh, next update: %v", source.name, source.cacheFile, delay)
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} else {
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dlog.Debugf("Source [%s] cache file [%s] needs to be refreshed", source.name, source.cacheFile)
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}
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return
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}
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func writeSource(f string, bin, sig []byte) (err error) {
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var fSrc, fSig *safefile.File
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if fSrc, err = safefile.Create(f, 0644); err != nil {
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return
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}
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defer fSrc.Close()
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if fSig, err = safefile.Create(f+".minisig", 0644); err != nil {
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return
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}
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defer fSig.Close()
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if _, err = fSrc.Write(bin); err != nil {
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return
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}
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if _, err = fSig.Write(sig); err != nil {
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return
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}
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if err = fSrc.Commit(); err != nil {
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return
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}
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return fSig.Commit()
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}
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func (source *Source) writeToCache(bin, sig []byte, now time.Time) {
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f := source.cacheFile
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var writeErr error // an error writing cache isn't fatal
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defer func() {
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source.in = bin
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if writeErr == nil {
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return
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}
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if absPath, absErr := filepath.Abs(f); absErr == nil {
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f = absPath
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}
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dlog.Warnf("%s: %s", f, writeErr)
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}()
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if !bytes.Equal(source.in, bin) {
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if writeErr = writeSource(f, bin, sig); writeErr != nil {
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return
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}
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}
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writeErr = os.Chtimes(f, now, now)
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}
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func (source *Source) parseURLs(urls []string) {
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for _, urlStr := range urls {
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if srcURL, err := url.Parse(urlStr); err != nil {
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dlog.Warnf("Source [%s] failed to parse URL [%s]", source.name, urlStr)
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} else {
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source.urls = append(source.urls, srcURL)
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}
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}
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}
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func fetchFromURL(xTransport *XTransport, u *url.URL) (bin []byte, err error) {
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bin, _, _, err = xTransport.Get(u, "", DefaultTimeout)
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return bin, err
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}
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func (source *Source) fetchWithCache(xTransport *XTransport, now time.Time) (delay time.Duration, err error) {
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if delay, err = source.fetchFromCache(now); err != nil {
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if len(source.urls) == 0 {
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dlog.Errorf("Source [%s] cache file [%s] not present and no valid URL", source.name, source.cacheFile)
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return
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}
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dlog.Debugf("Source [%s] cache file [%s] not present", source.name, source.cacheFile)
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}
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if len(source.urls) > 0 {
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defer func() {
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source.refresh = now.Add(delay)
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}()
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}
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if len(source.urls) == 0 || delay > 0 {
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return
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}
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delay = MinimumPrefetchInterval
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var bin, sig []byte
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for _, srcURL := range source.urls {
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dlog.Infof("Source [%s] loading from URL [%s]", source.name, srcURL)
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sigURL := &url.URL{}
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*sigURL = *srcURL // deep copy to avoid parsing twice
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sigURL.Path += ".minisig"
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if bin, err = fetchFromURL(xTransport, srcURL); err != nil {
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dlog.Debugf("Source [%s] failed to download from URL [%s]", source.name, srcURL)
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continue
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}
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if sig, err = fetchFromURL(xTransport, sigURL); err != nil {
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dlog.Debugf("Source [%s] failed to download signature from URL [%s]", source.name, sigURL)
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continue
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}
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if err = source.checkSignature(bin, sig); err == nil {
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break // valid signature
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} // above err check inverted to make use of implicit continue
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dlog.Debugf("Source [%s] failed signature check using URL [%s]", source.name, srcURL)
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}
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if err != nil {
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return
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}
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source.writeToCache(bin, sig, now)
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delay = source.prefetchDelay
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return
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}
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// NewSource loads a new source using the given cacheFile and urls, ensuring it has a valid signature
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func NewSource(name string, xTransport *XTransport, urls []string, minisignKeyStr string, cacheFile string, formatStr string, refreshDelay time.Duration) (source *Source, err error) {
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if refreshDelay < DefaultPrefetchDelay {
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refreshDelay = DefaultPrefetchDelay
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}
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source = &Source{name: name, urls: []*url.URL{}, cacheFile: cacheFile, cacheTTL: refreshDelay, prefetchDelay: DefaultPrefetchDelay}
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if formatStr == "v2" {
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source.format = SourceFormatV2
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} else {
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return source, fmt.Errorf("Unsupported source format: [%s]", formatStr)
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}
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if minisignKey, err := minisign.NewPublicKey(minisignKeyStr); err == nil {
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source.minisignKey = &minisignKey
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} else {
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return source, err
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}
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source.parseURLs(urls)
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if _, err = source.fetchWithCache(xTransport, timeNow()); err == nil {
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dlog.Noticef("Source [%s] loaded", name)
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}
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return
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}
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// PrefetchSources downloads latest versions of given sources, ensuring they have a valid signature before caching
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func PrefetchSources(xTransport *XTransport, sources []*Source) time.Duration {
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now := timeNow()
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interval := MinimumPrefetchInterval
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for _, source := range sources {
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if source.refresh.IsZero() || source.refresh.After(now) {
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continue
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}
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dlog.Debugf("Prefetching [%s]", source.name)
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if delay, err := source.fetchWithCache(xTransport, now); err != nil {
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dlog.Infof("Prefetching [%s] failed: %v", source.name, err)
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} else {
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dlog.Debugf("Prefetching [%s] succeeded, next update: %v", source.name, delay)
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if delay >= MinimumPrefetchInterval && (interval == MinimumPrefetchInterval || interval > delay) {
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interval = delay
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}
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}
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}
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return interval
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}
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func (source *Source) Parse(prefix string) ([]RegisteredServer, error) {
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if source.format == SourceFormatV2 {
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return source.parseV2(prefix)
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}
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dlog.Fatal("Unexpected source format")
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return []RegisteredServer{}, nil
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}
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func (source *Source) parseV2(prefix string) ([]RegisteredServer, error) {
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var registeredServers []RegisteredServer
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var stampErrs []string
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appendStampErr := func(format string, a ...interface{}) {
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stampErr := fmt.Sprintf(format, a...)
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stampErrs = append(stampErrs, stampErr)
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dlog.Warn(stampErr)
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}
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in := string(source.in)
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parts := strings.Split(in, "## ")
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if len(parts) < 2 {
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return registeredServers, fmt.Errorf("Invalid format for source at [%v]", source.urls)
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}
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parts = parts[1:]
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PartsLoop:
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for _, part := range parts {
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part = strings.TrimFunc(part, unicode.IsSpace)
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subparts := strings.Split(part, "\n")
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if len(subparts) < 2 {
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return registeredServers, fmt.Errorf("Invalid format for source at [%v]", source.urls)
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}
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name := strings.TrimFunc(subparts[0], unicode.IsSpace)
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if len(name) == 0 {
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return registeredServers, fmt.Errorf("Invalid format for source at [%v]", source.urls)
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}
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subparts = subparts[1:]
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name = prefix + name
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var stampStr, description string
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for _, subpart := range subparts {
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subpart = strings.TrimFunc(subpart, unicode.IsSpace)
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if strings.HasPrefix(subpart, "sdns:") {
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if len(stampStr) > 0 {
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appendStampErr("Multiple stamps for server [%s]", name)
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continue PartsLoop
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}
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stampStr = subpart
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continue
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} else if len(subpart) == 0 || strings.HasPrefix(subpart, "//") {
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continue
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}
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if len(description) > 0 {
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description += "\n"
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}
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description += subpart
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}
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if len(stampStr) < 6 {
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appendStampErr("Missing stamp for server [%s]", name)
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continue
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}
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stamp, err := stamps.NewServerStampFromString(stampStr)
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if err != nil {
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appendStampErr("Invalid or unsupported stamp [%v]: %s", stampStr, err.Error())
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continue
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}
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registeredServer := RegisteredServer{
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name: name, stamp: stamp, description: description,
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}
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dlog.Debugf("Registered [%s] with stamp [%s]", name, stamp.String())
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registeredServers = append(registeredServers, registeredServer)
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}
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if len(stampErrs) > 0 {
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return registeredServers, fmt.Errorf("%s", strings.Join(stampErrs, ", "))
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}
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return registeredServers, nil
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}
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