gitee.com/mysnapcore/mysnapd@v0.1.0/snap/helpers.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2019-2020 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package snap
    21  
    22  import (
    23  	"os/user"
    24  	"path/filepath"
    25  	"strconv"
    26  	"syscall"
    27  
    28  	"gitee.com/mysnapcore/mysnapd/dirs"
    29  	"gitee.com/mysnapcore/mysnapd/snap/naming"
    30  )
    31  
    32  var (
    33  	userLookupId = user.LookupId
    34  )
    35  
    36  func IsSnapd(snapID string) bool {
    37  	return snapID == naming.WellKnownSnapID("snapd")
    38  }
    39  
    40  // AllUsers returns a list of users, including the root user and all users that
    41  // can be found under /home with a snap directory.
    42  func AllUsers(opts *dirs.SnapDirOptions) ([]*user.User, error) {
    43  	ds, err := filepath.Glob(DataHomeGlob(opts))
    44  	if err != nil {
    45  		// can't happen?
    46  		return nil, err
    47  	}
    48  
    49  	users := make([]*user.User, 1, len(ds)+1)
    50  	root, err := user.LookupId("0")
    51  	if err != nil {
    52  		return nil, err
    53  	}
    54  	users[0] = root
    55  	seen := make(map[uint32]bool, len(ds)+1)
    56  	seen[0] = true
    57  	var st syscall.Stat_t
    58  	for _, d := range ds {
    59  		err := syscall.Stat(d, &st)
    60  		if err != nil {
    61  			continue
    62  		}
    63  		if seen[st.Uid] {
    64  			continue
    65  		}
    66  		seen[st.Uid] = true
    67  		usr, err := userLookupId(strconv.FormatUint(uint64(st.Uid), 10))
    68  		if err != nil {
    69  			// Treat all non-nil errors as user.Unknown{User,Group}Error's, as
    70  			// currently Go's handling of returned errno from get{pw,gr}nam_r
    71  			// in the cgo implementation of user.Lookup is lacking, and thus
    72  			// user.Unknown{User,Group}Error is returned only when errno is 0
    73  			// and the list of users/groups is empty, but as per the man page
    74  			// for get{pw,gr}nam_r, there are many other errno's that typical
    75  			// systems could return to indicate that the user/group wasn't
    76  			// found, however unfortunately the POSIX standard does not actually
    77  			// dictate what errno should be used to indicate "user/group not
    78  			// found", and so even if Go is more robust, it may not ever be
    79  			// fully robust. See from the man page:
    80  			//
    81  			// > It [POSIX.1-2001] does not call "not found" an error, hence
    82  			// > does not specify what value errno might have in this situation.
    83  			// > But that makes it impossible to recognize errors.
    84  			//
    85  			// See upstream Go issue: https://github.com/golang/go/issues/40334
    86  			continue
    87  		} else {
    88  			users = append(users, usr)
    89  		}
    90  	}
    91  
    92  	return users, nil
    93  }