golang sumdb 代码
文件路径：/src/cmd/go/internal/modfetch/sumdb.go
/ 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
/go:build !cmd_go_bootstrap
package modfetch
import (
"bytes"
"errors"
"fmt"
"io"
"io/fs"
"net/url"
"os"
"path/filepath"
"strings"
"sync"
"time"
"cmd/go/internal/base"
"cmd/go/internal/cfg"
"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" && !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, fs.ErrNotExist) {
/ No proxies, or all proxies failed (with 404, 410, or 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, fmt.Errorf("could not locate sumdb file: missing $GOPATH: %s",
cfg.GoPathError)
}
targ := filepath.Join(cfg.SumdbDir, file)
data, err = lockedfile.Read(targ)
if errors.Is(err, fs.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 fmt.Errorf("could not locate sumdb file: missing $GOPATH: %s",
cfg.GoPathError)
}
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 := io.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 = &fs.PathError{Op: "read", Path: targ, Err: fs.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)
}