// Package proxy implements a programmable proxy for rclone servepackage proxy import (	"bytes"	"context"	"crypto/hmac"	"crypto/rand"	"crypto/sha256"	"crypto/subtle"	"encoding/hex"	"encoding/json"	"errors"	"fmt"	"net/netip"	"os/exec"	"strings"	"sync"	"sync/atomic"	"time" 	"github.com/rclone/rclone/fs"	"github.com/rclone/rclone/fs/cache"	"github.com/rclone/rclone/fs/config/configmap"	"github.com/rclone/rclone/fs/config/obscure"	libcache "github.com/rclone/rclone/lib/cache"	libhttp "github.com/rclone/rclone/lib/http"	"github.com/rclone/rclone/vfs"	"github.com/rclone/rclone/vfs/vfscommon") // Help contains text describing how to use the proxyvar Help = strings.ReplaceAll(`### Auth Proxy If you supply the parameter |--auth-proxy /path/to/program| thenrclone will use that program to generate backends on the fly whichthen are used to authenticate incoming requests.  This uses a simpleJSON based protocol with input on STDIN and output on STDOUT. **PLEASE NOTE:** |--auth-proxy| and |--authorized-keys| cannot be usedtogether, if |--auth-proxy| is set the authorized keys option will beignored. There is an example program[bin/test_proxy.py](https://github.com/rclone/rclone/blob/master/bin/test_proxy.py)in the rclone source code. The program's job is to take a |user| and |pass| on the input and turnthose into the config for a backend on STDOUT in JSON format.  Thisconfig will have any default parameters for the backend added, but itwon't use configuration from environment variables or command lineoptions - it is the job of the proxy program to make a completeconfig. This config generated must have this extra parameter - |_root| - root to use for the backend And it may have these parameters - |_obscure| - comma separated strings for parameters to obscure- |_secret_access_key| - the secret for S3 access key auth (see below) If password authentication was used by the client, input to the proxyprocess (on STDIN) would look similar to this: |||json{  "user": "me",  "pass": "mypassword",  "client_ip": "192.168.1.1"}||| If public-key authentication was used by the client, input to theproxy process (on STDIN) would look similar to this: |||json{  "user": "me",  "public_key": "AAAAB3NzaC1yc2EAAAADAQABAAABAQDuwESFdAe14hVS6omeyX7edc...JQdf",  "client_ip": "192.168.1.1"}||| If the client authenticated with an S3 access key (|rclone serve s3|),the client never sends its secret, only a signature made with it, sothe input contains just the access key ID as the |user| with no |pass|or |public_key|: |||json{  "user": "AKIAIOSFODNN7EXAMPLE",  "client_ip": "192.168.1.1"}||| In this case the program must look up the secret access key for thataccess key ID and return it in the |_secret_access_key| field of theoutput. Rclone then uses that secret to verify the signature on therequest, refusing the request if it does not match. This means theproxy program is the source of truth for both the credentials and thebackend they map to. If the program does not return|_secret_access_key| or returns it empty the request is refused. The program's answer for an access key ID is cached (see below) butis checked with the program again after 5 minutes even if the accesskey ID is in constant use, so revoking an access key ID in theprogram takes effect within 5 minutes. A rotated secret takes effecton the first request signed with it. The |client_ip| key holds the IP address the client connected from,without a port number.  It can be used to restrict logins to certainnetworks, or to log authentication attempts centrally.  It is omitted ifthe client has no IP address, for example when connecting over a unixsocket.  Note that if rclone is behind a reverse proxy this will be theaddress of the reverse proxy and not the original client. And as an example return this on STDOUT |||json{  "type": "sftp",  "_root": "",  "_obscure": "pass",  "user": "me",  "pass": "mypassword",  "host": "sftp.example.com"}||| This would mean that an SFTP backend would be created on the fly forthe |user| and |pass|/|public_key| returned in the output to the host given.  Notethat since |_obscure| is set to |pass|, rclone will obscure the |pass|parameter before creating the backend (which is required for sftpbackends). The program can manipulate the supplied |user| in any way, for exampleto make proxy to many different sftp backends, you could make the|user| be |user@example.com| and then set the |host| to |example.com|in the output and the user to |user|. For security you'd probably wantto restrict the |host| to a limited list. An internal cache of backends is keyed on the |user|, a hash of the|pass| or |public_key|, and the |client_ip|.  This means that if auser's password or public-key changes, the client connects from a new IPaddress, or the proxy returns different config parameters (eg a rotated|api_key|), a fresh backend will be created on the next request ratherthan the cached one being reused. This can be used to build general purpose proxies to any kind ofbackend that rclone supports. `, "|", "`") // OptionsInfo descripts the Options in usevar OptionsInfo = fs.Options{{	Name:    "auth_proxy",	Default: "",	Help:    "A program to use to create the backend from the auth",}} // Options is options for creating the proxytype Options struct {	AuthProxy string `config:"auth_proxy"`} // Opt is the default optionsvar Opt Options func init() {	fs.RegisterGlobalOptions(fs.OptionsInfo{Name: "proxy", Opt: &Opt, Options: OptionsInfo})} // Proxy represents a proxy to turn auth requests into a VFStype Proxy struct {	cmdLine     []string // broken down command line	vfsCache    *libcache.Cache	ctx         context.Context // for global config	Opt         Options	vfsOpt      vfscommon.Options	accessKeyMu sync.Mutex // serialises replacing a cached access key entry} // cacheEntry is what is stored in the vfsCachetype cacheEntry struct {	vfs       *vfs.VFS          // stored VFS	pwHash    [sha256.Size]byte // sha256 hash of the password/publicKey	secret    string            // secret access key returned by the proxy for access key auth	refreshed *atomic.Int64     // unix nanoseconds when the proxy last confirmed this entry} // accessKeyRefreshInterval is the minimum time between consulting the// proxy again for a cached access key ID whose secret failed to// verify a request, so a stream of bad signatures for a known access// key ID can't make the proxy run for every request.//// A variable so tests can adjust it.var accessKeyRefreshInterval = 10 * time.Second // accessKeyRevalidateInterval is how long a cached access key ID is// trusted before the proxy is asked about it again even though its// signatures are still verifying, so a revoked access key ID stops// working within this time rather than for as long as it stays in// use.//// A variable so tests can adjust it.var accessKeyRevalidateInterval = 5 * time.Minute // authKind is the kind of credential the client presentedtype authKind int const (	authPassword  authKind = iota // auth is a password	authPublicKey                 // auth is a public key	authAccessKey                 // user is an S3 access key ID and auth is empty) // New creates a new proxy with the Options passed in//// Any VFS are created with the vfsOpt passed in.func New(ctx context.Context, opt *Options, vfsOpt *vfscommon.Options) *Proxy {	p := &Proxy{		ctx:      ctx,		Opt:      *opt,		cmdLine:  strings.Fields(opt.AuthProxy),		vfsCache: libcache.New(),		vfsOpt:   *vfsOpt,	}	p.vfsCache.SetFinalizer(func(value any) {		if entry, ok := value.(cacheEntry); ok && entry.vfs != nil {			entry.vfs.Shutdown()		}	})	return p} // run the proxy command returning a config mapfunc (p *Proxy) run(in map[string]string) (config configmap.Simple, err error) {	cmd := exec.Command(p.cmdLine[0], p.cmdLine[1:]...)	inBytes, err := json.MarshalIndent(in, "", "\t")	if err != nil {		return nil, fmt.Errorf("proxy: failed to marshal input: %w", err)	}	var stdout, stderr bytes.Buffer	cmd.Stdin = bytes.NewBuffer(inBytes)	cmd.Stdout = &stdout	cmd.Stderr = &stderr	start := time.Now()	err = cmd.Run()	fs.Debugf(nil, "Calling proxy %v", p.cmdLine)	duration := time.Since(start)	if err != nil {		return nil, fmt.Errorf("proxy: failed on %v: %q: %w", p.cmdLine, strings.TrimSpace(stderr.String()), err)	}	err = json.Unmarshal(stdout.Bytes(), &config)	if err != nil {		return nil, fmt.Errorf("proxy: failed to read output: %q: %w", stdout.String(), err)	}	fs.Debugf(nil, "Proxy returned in %v", duration) 	// Obscure any values in the config map that need it	obscureFields, ok := config.Get("_obscure")	if ok {		for key := range strings.SplitSeq(obscureFields, ",") {			value, ok := config.Get(key)			if ok {				obscuredValue, err := obscure.Obscure(value)				if err != nil {					return nil, fmt.Errorf("proxy: %w", err)				}				config.Set(key, obscuredValue)			}		}	}	return config, nil} // cacheKeyHMACKey is a per-process random key used to derive cache keys// from auth credentials. Using a keyed hash (HMAC) rather than a bare// SHA256 means the hash fragment that appears in logs and backend names// cannot be used to brute-force the underlying password offline.var cacheKeyHMACKey = func() []byte {	key := make([]byte, 32)	if _, err := rand.Read(key); err != nil {		panic(fmt.Sprintf("proxy: failed to generate cache key: %v", err))	}	return key}() // ipFromAddr returns the bare IP from a "host:port" address, or "" if it has none.func ipFromAddr(addr string) string {	ap, err := netip.ParseAddrPort(addr)	if err != nil {		return ""	}	return ap.Addr().Unmap().String()} // generateCacheKey creates a composite cache key from the user, the auth// credentials and the client's IP address.func generateCacheKey(user, auth, clientIP string) string {	mac := hmac.New(sha256.New, cacheKeyHMACKey)	mac.Write([]byte(auth))	// Separate the two so ("ab", "c") can't collide with ("a", "bc")	mac.Write([]byte{0})	mac.Write([]byte(clientIP))	return user + "-" + hex.EncodeToString(mac.Sum(nil)[:8])} // call runs the auth proxy and returns a cacheEntry and an errorfunc (p *Proxy) call(user, auth string, kind authKind, clientIP string) (value any, err error) {	// Contact the proxy	in := map[string]string{		"user": user,	}	switch kind {	case authPublicKey:		in["public_key"] = auth	case authPassword:		in["pass"] = auth	}	if clientIP != "" {		in["client_ip"] = clientIP	}	config, err := p.run(in)	if err != nil {		return nil, err	} 	// Look for required fields in the answer	fsName, ok := config.Get("type")	if !ok {		return nil, errors.New("proxy: type not set in result")	}	root, ok := config.Get("_root")	if !ok {		return nil, errors.New("proxy: _root not set in result")	}	var secret string	if kind == authAccessKey {		secret, ok = config.Get("_secret_access_key")		if !ok {			return nil, errors.New("proxy: _secret_access_key not set in result")		}		// An empty secret would let anyone sign for this access key ID		if secret == "" {			return nil, errors.New("proxy: _secret_access_key is empty in result")		}		// Keep the secret out of the backend config		delete(config, "_secret_access_key")	} 	// Find the backend	fsInfo, err := fs.Find(fsName)	if err != nil {		return nil, fmt.Errorf("proxy: couldn't find backend for %q: %w", fsName, err)	} 	// Make the cache key include the auth and the client IP so that	// changes to either (eg the proxy returning new config) create a	// fresh backend rather than reusing the cached one.	cacheKey := generateCacheKey(user, auth, clientIP) 	// For access key auth the secret isn't part of the cache key as	// it isn't known until the proxy has been run, so retire any	// cached entry whose secret the proxy has since changed.	//	// The stale entry is moved to a key including its old secret	// rather than deleted so that its VFS isn't shut down under	// requests still using it - it expires with the rest of the cache	// once it has been unused for long enough.	//	// The check, rename and the creation below are done under a lock	// so that two concurrent refreshes during a rotation can't have	// the second retire the backend the first has just created.	if kind == authAccessKey {		p.accessKeyMu.Lock()		defer p.accessKeyMu.Unlock()		if old, ok := p.vfsCache.GetMaybe(cacheKey); ok {			if entry, ok := old.(cacheEntry); ok && entry.secret != secret {				p.vfsCache.Rename(cacheKey, generateCacheKey(user, entry.secret, clientIP))			}		}	} 	// base name of config on user name and auth hash.  This may appear in logs	name := "proxy-" + cacheKey	fsString := name + ":" + root 	// Look for fs in the VFS cache	value, err = p.vfsCache.Get(cacheKey, func(key string) (value any, ok bool, err error) {		// Create the Fs from the cache		f, err := cache.GetFn(p.ctx, fsString, func(ctx context.Context, fsString string) (fs.Fs, error) {			// Update the config with the default values			for i := range fsInfo.Options {				o := &fsInfo.Options[i]				if _, found := config.Get(o.Name); !found && o.Default != nil && o.String() != "" {					config.Set(o.Name, o.String())				}			}			return fsInfo.NewFs(ctx, name, root, config)		})		if err != nil {			return nil, false, err		} 		// We hash the auth here so we don't copy the auth more than we		// need to in memory. An attacker would find it easier to go		// after the unencrypted password in memory most likely.		entry := cacheEntry{			vfs:       vfs.New(p.ctx, f, &p.vfsOpt),			pwHash:    sha256.Sum256([]byte(auth)),			secret:    secret,			refreshed: new(atomic.Int64),		}		return entry, true, nil	})	if err != nil {		return nil, fmt.Errorf("proxy: failed to create backend: %w", err)	}	// The proxy has just confirmed this entry whether it was created	// or reused	if entry, ok := value.(cacheEntry); ok {		entry.refreshed.Store(time.Now().UnixNano())	}	return value, nil} // Call runs the auth proxy with the username and password/public key provided// returning a *vfs.VFS and the key used in the VFS cache.//// remoteAddr is the address of the client as returned by net.Addr.String().// It may be empty if the client has no IP address, for example when// connecting over a unix socket.func (p *Proxy) Call(user, auth string, isPublicKey bool, remoteAddr string) (VFS *vfs.VFS, vfsKey string, err error) {	clientIP := ipFromAddr(remoteAddr) 	// Cache key includes the auth and the client IP so credential or	// address changes don't hit a stale entry	cacheKey := generateCacheKey(user, auth, clientIP) 	// Look in the cache first with the credential-aware key	value, ok := p.vfsCache.GetMaybe(cacheKey) 	// If not found then call the proxy for a fresh answer	if !ok {		kind := authPassword		if isPublicKey {			kind = authPublicKey		}		value, err = p.call(user, auth, kind, clientIP)		if err != nil {			return nil, "", err		}	} 	// check we got what we were expecting	entry, ok := value.(cacheEntry)	if !ok {		return nil, "", fmt.Errorf("proxy: value is not cache entry: %#v", value)	} 	// Check the password / public key matches the cached entry. The	// cache key already includes a hash of the auth, so a changed	// credential lands on a fresh key rather than this entry; this	// check is a final guard against a hash collision on the key	// returning a backend created with different auth.	authHash := sha256.Sum256([]byte(auth))	if subtle.ConstantTimeCompare(authHash[:], entry.pwHash[:]) != 1 {		if isPublicKey {			return nil, "", errors.New("proxy: incorrect public key")		}		return nil, "", errors.New("proxy: incorrect password")	} 	return entry.vfs, cacheKey, nil} // CallAccessKey runs the auth proxy for an S3 access key ID returning// a *vfs.VFS and the secret access key the proxy supplied for it.//// The caller must verify the request's signature against the returned// secret - the proxy only maps the access key ID to a backend and// secret, it cannot authenticate the client itself.//// If refresh is true the proxy is consulted rather than using a cached// answer, unless it was consulted for this access key ID less than// accessKeyRefreshInterval ago. A refresh never shuts down a cached// backend, even if the proxy returns a different secret, so this is// safe to do when a signature fails to verify in case the secret has// been rotated.//// A cached answer older than accessKeyRevalidateInterval is always// checked with the proxy so a revoked access key ID is refused even// if it is in constant use.//// remoteAddr is the address of the client as returned by net.Addr.String().func (p *Proxy) CallAccessKey(accessKeyID, remoteAddr string, refresh bool) (VFS *vfs.VFS, secret string, err error) {	clientIP := ipFromAddr(remoteAddr)

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