github.com/coreos/rocket@v1.30.1-0.20200224141603-171c416fac02/pkg/group/group.go (about)

     1  // Copyright 2015 The rkt Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package group
    16  
    17  import (
    18  	"bufio"
    19  	"errors"
    20  	"fmt"
    21  	"io"
    22  	"os"
    23  	"strconv"
    24  	"strings"
    25  
    26  	"github.com/hashicorp/errwrap"
    27  )
    28  
    29  const (
    30  	groupFilePath = "/etc/group"
    31  )
    32  
    33  // Group represents an entry in the group file.
    34  type Group struct {
    35  	Name  string
    36  	Pass  string
    37  	Gid   int
    38  	Users []string
    39  }
    40  
    41  // LookupGid reads the group file specified by groupFile, and returns the gid of the group
    42  // specified by groupName.
    43  func LookupGidFromFile(groupName, groupFile string) (gid int, err error) {
    44  	groups, err := parseGroupFile(groupFile)
    45  	if err != nil {
    46  		return -1, errwrap.Wrap(fmt.Errorf("error parsing %q file", groupFile), err)
    47  	}
    48  
    49  	group, ok := groups[groupName]
    50  	if !ok {
    51  		return -1, fmt.Errorf("%q group not found", groupName)
    52  	}
    53  
    54  	return group.Gid, nil
    55  }
    56  
    57  // LookupGid reads the group file and returns the gid of the group
    58  // specified by groupName.
    59  func LookupGid(groupName string) (gid int, err error) {
    60  	return LookupGidFromFile(groupName, groupFilePath)
    61  }
    62  
    63  func parseGroupFile(path string) (group map[string]*Group, err error) {
    64  	groupFile, err := os.Open(path)
    65  	if err != nil {
    66  		return nil, err
    67  	}
    68  	defer groupFile.Close()
    69  
    70  	return parseGroups(groupFile)
    71  }
    72  
    73  func parseGroups(r io.Reader) (group map[string]*Group, err error) {
    74  	s := bufio.NewScanner(r)
    75  	out := make(map[string]*Group)
    76  
    77  	for s.Scan() {
    78  		if err := s.Err(); err != nil {
    79  			return nil, err
    80  		}
    81  
    82  		text := s.Text()
    83  		if text == "" {
    84  			continue
    85  		}
    86  
    87  		p, err := parseGroupLine(text)
    88  		if err != nil {
    89  			return nil, errwrap.Wrap(errors.New("error parsing line"), err)
    90  		}
    91  
    92  		out[p.Name] = p
    93  	}
    94  
    95  	return out, nil
    96  }
    97  
    98  func parseGroupLine(line string) (*Group, error) {
    99  	const (
   100  		NameIdx = iota
   101  		PassIdx
   102  		GidIdx
   103  		UsersIdx
   104  	)
   105  	var err error
   106  
   107  	if line == "" {
   108  		return nil, errors.New("cannot parse empty line")
   109  	}
   110  
   111  	splits := strings.Split(line, ":")
   112  	if len(splits) < 4 {
   113  		return nil, fmt.Errorf("expected at least 4 fields, got %d", len(splits))
   114  	}
   115  
   116  	group := &Group{
   117  		Name: splits[NameIdx],
   118  		Pass: splits[PassIdx],
   119  	}
   120  
   121  	group.Gid, err = strconv.Atoi(splits[GidIdx])
   122  	if err != nil {
   123  		return nil, errwrap.Wrap(errors.New("unable to parse gid"), err)
   124  	}
   125  
   126  	u := splits[UsersIdx]
   127  	if u != "" {
   128  		group.Users = strings.Split(u, ",")
   129  	} else {
   130  		group.Users = []string{}
   131  	}
   132  
   133  	return group, nil
   134  }