github.com/stackdocker/rkt@v0.10.1-0.20151109095037-1aa827478248/common/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 common
    16  
    17  import (
    18  	"bufio"
    19  	"fmt"
    20  	"io"
    21  	"os"
    22  	"strconv"
    23  	"strings"
    24  )
    25  
    26  const (
    27  	groupFilePath = "/etc/group"
    28  	RktGroup      = "rkt"
    29  )
    30  
    31  // Group represents an entry in the group file.
    32  type Group struct {
    33  	Name  string
    34  	Pass  string
    35  	Gid   int
    36  	Users []string
    37  }
    38  
    39  // LookupGid reads the group file and returns the gid of the group
    40  // specified by groupName.
    41  func LookupGid(groupName string) (gid int, err error) {
    42  	groups, err := parseGroupFile(groupFilePath)
    43  	if err != nil {
    44  		return -1, fmt.Errorf("error parsing %q file: %v", groupFilePath, err)
    45  	}
    46  
    47  	group, ok := groups[groupName]
    48  	if !ok {
    49  		return -1, fmt.Errorf("%q group not found", groupName)
    50  	}
    51  
    52  	return group.Gid, nil
    53  }
    54  
    55  func parseGroupFile(path string) (group map[string]Group, err error) {
    56  	groupFile, err := os.Open(path)
    57  	if err != nil {
    58  		return nil, err
    59  	}
    60  	defer groupFile.Close()
    61  
    62  	return parseGroups(groupFile)
    63  }
    64  
    65  func parseGroups(r io.Reader) (group map[string]Group, err error) {
    66  	s := bufio.NewScanner(r)
    67  	out := make(map[string]Group)
    68  
    69  	for s.Scan() {
    70  		if err := s.Err(); err != nil {
    71  			return nil, err
    72  		}
    73  
    74  		text := s.Text()
    75  		if text == "" {
    76  			continue
    77  		}
    78  
    79  		p := Group{}
    80  		parseGroupLine(text, &p)
    81  
    82  		out[p.Name] = p
    83  	}
    84  
    85  	return out, nil
    86  }
    87  
    88  func parseGroupLine(line string, group *Group) {
    89  	const (
    90  		NameIdx = iota
    91  		PassIdx
    92  		GidIdx
    93  		UsersIdx
    94  	)
    95  
    96  	if line == "" {
    97  		return
    98  	}
    99  
   100  	splits := strings.Split(line, ":")
   101  	if len(splits) < 4 {
   102  		return
   103  	}
   104  
   105  	group.Name = splits[NameIdx]
   106  	group.Pass = splits[PassIdx]
   107  	group.Gid, _ = strconv.Atoi(splits[GidIdx])
   108  
   109  	u := splits[UsersIdx]
   110  	if u != "" {
   111  		group.Users = strings.Split(u, ",")
   112  	} else {
   113  		group.Users = []string{}
   114  	}
   115  }