blob: 783c4a433b41c6b00faf7539e26d136f353827f6 [file] [log] [blame]
// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Go checksum database lookup
// +build !cmd_go_bootstrap
package modfetch
import (
"bytes"
"errors"
"fmt"
"io/ioutil"
"net/url"
"os"
"path/filepath"
"strings"
"sync"
"time"
"cmd/go/internal/base"
"cmd/go/internal/cfg"
"cmd/go/internal/get"
"cmd/go/internal/lockedfile"
"cmd/go/internal/web"
"golang.org/x/mod/module"
"golang.org/x/mod/sumdb"
"golang.org/x/mod/sumdb/note"
)
// useSumDB reports whether to use the Go checksum database for the given module.
func useSumDB(mod module.Version) bool {
return cfg.GOSUMDB != "off" && !get.Insecure && !module.MatchPrefixPatterns(cfg.GONOSUMDB, mod.Path)
}
// lookupSumDB returns the Go checksum database's go.sum lines for the given module,
// along with the name of the database.
func lookupSumDB(mod module.Version) (dbname string, lines []string, err error) {
dbOnce.Do(func() {
dbName, db, dbErr = dbDial()
})
if dbErr != nil {
return "", nil, dbErr
}
lines, err = db.Lookup(mod.Path, mod.Version)
return dbName, lines, err
}
var (
dbOnce sync.Once
dbName string
db *sumdb.Client
dbErr error
)
func dbDial() (dbName string, db *sumdb.Client, err error) {
// $GOSUMDB can be "key" or "key url",
// and the key can be a full verifier key
// or a host on our list of known keys.
// Special case: sum.golang.google.cn
// is an alias, reachable inside mainland China,
// for sum.golang.org. If there are more
// of these we should add a map like knownGOSUMDB.
gosumdb := cfg.GOSUMDB
if gosumdb == "sum.golang.google.cn" {
gosumdb = "sum.golang.org https://sum.golang.google.cn"
}
key := strings.Fields(gosumdb)
if len(key) >= 1 {
if k := knownGOSUMDB[key[0]]; k != "" {
key[0] = k
}
}
if len(key) == 0 {
return "", nil, fmt.Errorf("missing GOSUMDB")
}
if len(key) > 2 {
return "", nil, fmt.Errorf("invalid GOSUMDB: too many fields")
}
vkey, err := note.NewVerifier(key[0])
if err != nil {
return "", nil, fmt.Errorf("invalid GOSUMDB: %v", err)
}
name := vkey.Name()
// No funny business in the database name.
direct, err := url.Parse("https://" + name)
if err != nil || strings.HasSuffix(name, "/") || *direct != (url.URL{Scheme: "https", Host: direct.Host, Path: direct.Path, RawPath: direct.RawPath}) || direct.RawPath != "" || direct.Host == "" {
return "", nil, fmt.Errorf("invalid sumdb name (must be host[/path]): %s %+v", name, *direct)
}
// Determine how to get to database.
var base *url.URL
if len(key) >= 2 {
// Use explicit alternate URL listed in $GOSUMDB,
// bypassing both the default URL derivation and any proxies.
u, err := url.Parse(key[1])
if err != nil {
return "", nil, fmt.Errorf("invalid GOSUMDB URL: %v", err)
}
base = u
}
return name, sumdb.NewClient(&dbClient{key: key[0], name: name, direct: direct, base: base}), nil
}
type dbClient struct {
key string
name string
direct *url.URL
once sync.Once
base *url.URL
baseErr error
}
func (c *dbClient) ReadRemote(path string) ([]byte, error) {
c.once.Do(c.initBase)
if c.baseErr != nil {
return nil, c.baseErr
}
var data []byte
start := time.Now()
targ := web.Join(c.base, path)
data, err := web.GetBytes(targ)
if false {
fmt.Fprintf(os.Stderr, "%.3fs %s\n", time.Since(start).Seconds(), targ.Redacted())
}
return data, err
}
// initBase determines the base URL for connecting to the database.
// Determining the URL requires sending network traffic to proxies,
// so this work is delayed until we need to download something from
// the database. If everything we need is in the local cache and
// c.ReadRemote is never called, we will never do this work.
func (c *dbClient) initBase() {
if c.base != nil {
return
}
// Try proxies in turn until we find out how to connect to this database.
//
// Before accessing any checksum database URL using a proxy, the proxy
// client should first fetch <proxyURL>/sumdb/<sumdb-name>/supported.
//
// If that request returns a successful (HTTP 200) response, then the proxy
// supports proxying checksum database requests. In that case, the client
// should use the proxied access method only, never falling back to a direct
// connection to the database.
//
// If the /sumdb/<sumdb-name>/supported check fails with a “not found” (HTTP
// 404) or “gone” (HTTP 410) response, or if the proxy is configured to fall
// back on errors, the client will try the next proxy. If there are no
// proxies left or if the proxy is "direct" or "off", the client should
// connect directly to that database.
//
// Any other response is treated as the database being unavailable.
//
// See https://golang.org/design/25530-sumdb#proxying-a-checksum-database.
err := TryProxies(func(proxy string) error {
switch proxy {
case "noproxy":
return errUseProxy
case "direct", "off":
return errProxyOff
default:
proxyURL, err := url.Parse(proxy)
if err != nil {
return err
}
if _, err := web.GetBytes(web.Join(proxyURL, "sumdb/"+c.name+"/supported")); err != nil {
return err
}
// Success! This proxy will help us.
c.base = web.Join(proxyURL, "sumdb/"+c.name)
return nil
}
})
if errors.Is(err, os.ErrNotExist) {
// No proxies, or all proxies failed (with 404, 410, or were were allowed
// to fall back), or we reached an explicit "direct" or "off".
c.base = c.direct
} else if err != nil {
c.baseErr = err
}
}
// ReadConfig reads the key from c.key
// and otherwise reads the config (a latest tree head) from GOPATH/pkg/sumdb/<file>.
func (c *dbClient) ReadConfig(file string) (data []byte, err error) {
if file == "key" {
return []byte(c.key), nil
}
if cfg.SumdbDir == "" {
return nil, errors.New("could not locate sumdb file: missing $GOPATH")
}
targ := filepath.Join(cfg.SumdbDir, file)
data, err = lockedfile.Read(targ)
if errors.Is(err, os.ErrNotExist) {
// Treat non-existent as empty, to bootstrap the "latest" file
// the first time we connect to a given database.
return []byte{}, nil
}
return data, err
}
// WriteConfig rewrites the latest tree head.
func (*dbClient) WriteConfig(file string, old, new []byte) error {
if file == "key" {
// Should not happen.
return fmt.Errorf("cannot write key")
}
if cfg.SumdbDir == "" {
return errors.New("could not locate sumdb file: missing $GOPATH")
}
targ := filepath.Join(cfg.SumdbDir, file)
os.MkdirAll(filepath.Dir(targ), 0777)
f, err := lockedfile.Edit(targ)
if err != nil {
return err
}
defer f.Close()
data, err := ioutil.ReadAll(f)
if err != nil {
return err
}
if len(data) > 0 && !bytes.Equal(data, old) {
return sumdb.ErrWriteConflict
}
if _, err := f.Seek(0, 0); err != nil {
return err
}
if err := f.Truncate(0); err != nil {
return err
}
if _, err := f.Write(new); err != nil {
return err
}
return f.Close()
}
// ReadCache reads cached lookups or tiles from
// GOPATH/pkg/mod/cache/download/sumdb,
// which will be deleted by "go clean -modcache".
func (*dbClient) ReadCache(file string) ([]byte, error) {
targ := filepath.Join(cfg.GOMODCACHE, "cache/download/sumdb", file)
data, err := lockedfile.Read(targ)
// lockedfile.Write does not atomically create the file with contents.
// There is a moment between file creation and locking the file for writing,
// during which the empty file can be locked for reading.
// Treat observing an empty file as file not found.
if err == nil && len(data) == 0 {
err = &os.PathError{Op: "read", Path: targ, Err: os.ErrNotExist}
}
return data, err
}
// WriteCache updates cached lookups or tiles.
func (*dbClient) WriteCache(file string, data []byte) {
targ := filepath.Join(cfg.GOMODCACHE, "cache/download/sumdb", file)
os.MkdirAll(filepath.Dir(targ), 0777)
lockedfile.Write(targ, bytes.NewReader(data), 0666)
}
func (*dbClient) Log(msg string) {
// nothing for now
}
func (*dbClient) SecurityError(msg string) {
base.Fatalf("%s", msg)
}