1// Copyright 2015 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// +build aix darwin dragonfly freebsd hurd linux netbsd openbsd solaris
6
7package net
8
9import (
10	"errors"
11	"internal/bytealg"
12	"io"
13	"os"
14)
15
16// nssConf represents the state of the machine's /etc/nsswitch.conf file.
17type nssConf struct {
18	err     error                  // any error encountered opening or parsing the file
19	sources map[string][]nssSource // keyed by database (e.g. "hosts")
20}
21
22type nssSource struct {
23	source   string // e.g. "compat", "files", "mdns4_minimal"
24	criteria []nssCriterion
25}
26
27// standardCriteria reports all specified criteria have the default
28// status actions.
29func (s nssSource) standardCriteria() bool {
30	for i, crit := range s.criteria {
31		if !crit.standardStatusAction(i == len(s.criteria)-1) {
32			return false
33		}
34	}
35	return true
36}
37
38// nssCriterion is the parsed structure of one of the criteria in brackets
39// after an NSS source name.
40type nssCriterion struct {
41	negate bool   // if "!" was present
42	status string // e.g. "success", "unavail" (lowercase)
43	action string // e.g. "return", "continue" (lowercase)
44}
45
46// standardStatusAction reports whether c is equivalent to not
47// specifying the criterion at all. last is whether this criteria is the
48// last in the list.
49func (c nssCriterion) standardStatusAction(last bool) bool {
50	if c.negate {
51		return false
52	}
53	var def string
54	switch c.status {
55	case "success":
56		def = "return"
57	case "notfound", "unavail", "tryagain":
58		def = "continue"
59	default:
60		// Unknown status
61		return false
62	}
63	if last && c.action == "return" {
64		return true
65	}
66	return c.action == def
67}
68
69func parseNSSConfFile(file string) *nssConf {
70	f, err := os.Open(file)
71	if err != nil {
72		return &nssConf{err: err}
73	}
74	defer f.Close()
75	return parseNSSConf(f)
76}
77
78func parseNSSConf(r io.Reader) *nssConf {
79	slurp, err := readFull(r)
80	if err != nil {
81		return &nssConf{err: err}
82	}
83	conf := new(nssConf)
84	conf.err = foreachLine(slurp, func(line []byte) error {
85		line = trimSpace(removeComment(line))
86		if len(line) == 0 {
87			return nil
88		}
89		colon := bytealg.IndexByte(line, ':')
90		if colon == -1 {
91			return errors.New("no colon on line")
92		}
93		db := string(trimSpace(line[:colon]))
94		srcs := line[colon+1:]
95		for {
96			srcs = trimSpace(srcs)
97			if len(srcs) == 0 {
98				break
99			}
100			sp := bytealg.IndexByte(srcs, ' ')
101			var src string
102			if sp == -1 {
103				src = string(srcs)
104				srcs = nil // done
105			} else {
106				src = string(srcs[:sp])
107				srcs = trimSpace(srcs[sp+1:])
108			}
109			var criteria []nssCriterion
110			// See if there's a criteria block in brackets.
111			if len(srcs) > 0 && srcs[0] == '[' {
112				bclose := bytealg.IndexByte(srcs, ']')
113				if bclose == -1 {
114					return errors.New("unclosed criterion bracket")
115				}
116				var err error
117				criteria, err = parseCriteria(srcs[1:bclose])
118				if err != nil {
119					return errors.New("invalid criteria: " + string(srcs[1:bclose]))
120				}
121				srcs = srcs[bclose+1:]
122			}
123			if conf.sources == nil {
124				conf.sources = make(map[string][]nssSource)
125			}
126			conf.sources[db] = append(conf.sources[db], nssSource{
127				source:   src,
128				criteria: criteria,
129			})
130		}
131		return nil
132	})
133	return conf
134}
135
136// parses "foo=bar !foo=bar"
137func parseCriteria(x []byte) (c []nssCriterion, err error) {
138	err = foreachField(x, func(f []byte) error {
139		not := false
140		if len(f) > 0 && f[0] == '!' {
141			not = true
142			f = f[1:]
143		}
144		if len(f) < 3 {
145			return errors.New("criterion too short")
146		}
147		eq := bytealg.IndexByte(f, '=')
148		if eq == -1 {
149			return errors.New("criterion lacks equal sign")
150		}
151		lowerASCIIBytes(f)
152		c = append(c, nssCriterion{
153			negate: not,
154			status: string(f[:eq]),
155			action: string(f[eq+1:]),
156		})
157		return nil
158	})
159	return
160}
161