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之前有写为sftpgo添加匿名访问支持，还有个问题不能访问链接文件，基于sftpgo2.2.2修改制作了个patch以支持软链接，linux下测试通过，windows未测试。

diff -urN -x .git sftpgo/common/connection.go sftpgo3/common/connection.go
--- sftpgo/common/connection.go 2022-04-04 15:06:39.542187282 +0800
+++ sftpgo3/common/connection.go        2022-04-04 14:57:31.027102136 +0800
@@ -242,6 +242,27 @@
                c.Log(logger.LevelDebug, "error listing directory: %+v", err)
                return nil, c.GetFsError(fs, err)
        }
+       if c.protocol == ProtocolWebDAV || c.protocol == ProtocolFTP {
+               for k, file := range files {
+                       if file.Mode()&os.ModeSymlink != 0 {
+                               dst, err := os.Readlink(fsPath + "/" + file.Name())
+                               if err != nil {
+                                       c.Log(logger.LevelError, "error readlink: %#v error: %+v", fsPath+"/"+file.Name(), err)
+                                       continue
+                               }
+                               dstinfo, err := os.Stat(dst)
+                               if err != nil {
+                                       c.Log(logger.LevelError, "error stat: %#v error: %+v", dst, err)
+                                       continue
+                               }
+                               if dstinfo.IsDir() {
+                                       files[k] = vfs.NewFileInfo(file.Name(), true, 0, dstinfo.ModTime(), false)
+                               } else {
+                                       files[k] = vfs.NewFileInfo(file.Name(), false, dstinfo.Size(), dstinfo.ModTime(), false)
+                               }
+                       }
+               }
+       }
        return c.User.AddVirtualDirs(files, virtualPath), nil
 }
 
diff -urN -x .git sftpgo/ftpd/handler.go sftpgo3/ftpd/handler.go
--- sftpgo/ftpd/handler.go      2022-04-04 15:06:39.550187152 +0800
+++ sftpgo3/ftpd/handler.go     2022-04-04 14:55:41.368885080 +0800
@@ -14,7 +14,7 @@
        "github.com/drakkan/sftpgo/v2/common"
        "github.com/drakkan/sftpgo/v2/dataprovider"
        "github.com/drakkan/sftpgo/v2/logger"
-       "github.com/drakkan/sftpgo/v2/util"
+       //"github.com/drakkan/sftpgo/v2/util"
        "github.com/drakkan/sftpgo/v2/vfs"
 )
 
@@ -288,10 +288,12 @@
        if err != nil {
                return files, err
        }
-       if name != "/" {
-               files = util.PrependFileInfo(files, vfs.NewFileInfo("..", true, 0, time.Now(), false))
-       }
-       files = util.PrependFileInfo(files, vfs.NewFileInfo(".", true, 0, time.Now(), false))
+       /*
+               if name != "/" {
+                       files = util.PrependFileInfo(files, vfs.NewFileInfo("..", true, 0, time.Now(), false))
+               }
+               files = util.PrependFileInfo(files, vfs.NewFileInfo(".", true, 0, time.Now(), false))
+       */
        return files, nil
 }
 
diff -urN -x .git sftpgo/vfs/osfs.go sftpgo3/vfs/osfs.go
--- sftpgo/vfs/osfs.go  2022-04-04 15:06:39.574186762 +0800
+++ sftpgo3/vfs/osfs.go 2022-04-04 14:59:06.413551648 +0800
@@ -291,6 +291,7 @@
                virtualPath = strings.TrimPrefix(virtualPath, fs.mountPath)
        }
        r := filepath.Clean(filepath.Join(fs.rootDir, virtualPath))
+       return r, nil
        p, err := filepath.EvalSymlinks(r)
        if err != nil && !os.IsNotExist(err) {
                return "", err

1.修改vfs/osfs.go文件取消对链接目标的校验是否在家目录内，这时部分客户端已正常，因为sftpgo返回链接目录属性为l而非d，导致有的客户端将链接目录识别为文件。
2.修改common/connection.go文件是修改返回的链接目录/文件的属性为标准目录和文件。
参考：
https://github.com/drakkan/sftpgo/issues/336

仅通过check_password_hook验证用户，用户信息使用web配置，将以下脚本保存为文件添加到sftpgo.json配置文件内check_password_hook参数。

#!/bin/bash -eu
#if [[ "${SFTPGO_AUTHD_USERNAME}" = "guest" ]] && [[ "${SFTPGO_AUTHD_PASSWORD}" = "pass" ]]; then
if [[ "${SFTPGO_AUTHD_USERNAME}" = "anonymous" ]] || [[ "${SFTPGO_AUTHD_USERNAME}" = "guest" ]]; then
cat <<EOF
{
  "status": 1
}
EOF
exit 0
fi

使用external_auth_hook外部验证用户并直接返回虚拟目录权限等信息：

#!/bin/bash -eu
if [[ "${SFTPGO_AUTHD_USERNAME}" = "anonymous" ]] || [[ "${SFTPGO_AUTHD_USERNAME}" = "guest" ]]; then
cat <<EOF
{
  "status": 1,
  "username": "${SFTPGO_AUTHD_USERNAME}",
  "home_dir": "/data/ftp",
  "permissions": {
    "/": ["list", "download"]
  },
  "virtual_folders": [
    {
      "name": "dir1",
      "mapped_path": "/data/dir1",
      "virtual_path": "/dir1"
    }, 
    {
      "name": "dir2",
      "mapped_path": "/data/dir2",
      "virtual_path": "/dir2"
    } 
  ]
}
EOF
fi

ftp/webdav匿名访问允许空密码patch：

diff -urN -x .git sftpgo2/ftpd/server.go sftpgo/ftpd/server.go
--- sftpgo2/ftpd/server.go      2022-04-05 18:55:25.959456839 +0800
+++ sftpgo/ftpd/server.go       2022-04-05 19:01:32.841334341 +0800
@@ -9,6 +9,7 @@
        "os"
        "path/filepath"
        "sync"
+        "strings"
 
        ftpserver "github.com/fclairamb/ftpserverlib"
 
@@ -182,6 +183,9 @@
 
 // AuthUser authenticates the user and selects an handling driver
 func (s *Server) AuthUser(cc ftpserver.ClientContext, username, password string) (ftpserver.ClientDriver, error) {
+       if len(strings.TrimSpace(password)) == 0 {
+               password = "guest"
+       }
        loginMethod := dataprovider.LoginMethodPassword
        if s.isTLSConnVerified(cc.ID()) {
                loginMethod = dataprovider.LoginMethodTLSCertificateAndPwd

diff -urN -x .git sftpgo2/webdavd/server.go sftpgo/webdavd/server.go
--- sftpgo2/webdavd/server.go   2022-04-05 18:55:25.995456233 +0800
+++ sftpgo/webdavd/server.go    2022-04-05 19:01:44.537140407 +0800
@@ -13,6 +13,7 @@
        "path/filepath"
        "runtime/debug"
        "time"
+        "strings"
 
        "github.com/go-chi/chi/v5/middleware"
        "github.com/rs/cors"
@@ -232,6 +233,9 @@
        var tlsCert *x509.Certificate
        loginMethod := dataprovider.LoginMethodPassword
        username, password, ok := r.BasicAuth()
+       if len(strings.TrimSpace(password)) == 0 {
+               password = "guest"
+       }
        if s.binding.isMutualTLSEnabled() && r.TLS != nil {
                if len(r.TLS.PeerCertificates) > 0 {
                        tlsCert = r.TLS.PeerCertificates[0]

参考：
https://github.com/drakkan/sftpgo/issues/373
https://github.com/drakkan/sftpgo/blob/main/docs/check-password-hook.md
https://github.com/drakkan/sftpgo/blob/main/docs/external-auth.md