summaryrefslogtreecommitdiff
path: root/nslcd_proto/io.go
blob: bf5928262de00dad662cfe571c904ad3e4dcd26b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
// Copyright (C) 2015, 2017 Luke Shumaker <lukeshu@sbcglobal.net>
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
// 02110-1301 USA

package nslcd_proto

import (
	"encoding/binary"
	"fmt"
	"io"
	"net"
	"reflect"

	"golang.org/x/sys/unix"
)

// NslcdError represents a normal, expected error when dealing with
// the nslcd protocol.  Passing invalid data to a Write operation is
// *not* an NslcdError, nor is passing a non-pointer to a Read
// operation; those are programming errors, and result in a panic().
type NslcdError string

func (o NslcdError) Error() string {
	return string(o)
}

func npanic(err NslcdError) {
	panic(err)
}

// An nslcdObject is an object with a different network representation
// than a naive structure.
type nslcdObject interface {
	// May panic(interface{}) if given invalid data.
	//
	// May panic(NslcdError) if encountering a network error.
	nslcdWrite(fd io.Writer)
}

// An nslcdObjectPtr is a pointer to an object with a different
// network representation than a naive structure.
type nslcdObjectPtr interface {
	// May panic(NslcdError) if encountering a network error.
	nslcdRead(fd io.Reader)
}

// Write an object to a stream.  Any errors returned are of type
// NslcdError.
func Write(fd io.Writer, data interface{}) (err error) {
	defer func() {
		if r := recover(); r != nil {
			switch r := r.(type) {
			case NslcdError:
				err = r
			default:
				panic(r)
			}
		}
	}()
	write(fd, data)

	return err
}

// Read an object from a stream.  Any errors returned are of type
// NslcdError.  If the type assertion succeeds, then
// fd.(*io.LimitedReader).N is used to prevent an overly-large buffer
// from being allocated.
func Read(fd io.Reader, data interface{}) (err error) {
	defer func() {
		if r := recover(); r != nil {
			switch r := r.(type) {
			case NslcdError:
				err = r
			default:
				panic(r)
			}
		}
	}()
	read(fd, data)

	return err
}

// Write an object to a stream.  In the event of an error, this
// function may panic(NslcdError)!  Handle it!
func write(fd io.Writer, data interface{}) {
	switch data := data.(type) {
	// basic data types
	case nslcdObject:
		data.nslcdWrite(fd)
	case []byte:
		if len(data) > 0 {
			_, err := fd.Write(data)
			if err != nil {
				npanic(NslcdError(err.Error()))
			}
		}
	case int32:
		err := binary.Write(fd, binary.BigEndian, data)
		if err != nil {
			npanic(NslcdError(err.Error()))
		}
	// composite datatypes
	case string:
		write(fd, int32(len(data)))
		write(fd, []byte(data))
	case []string:
		write(fd, int32(len(data)))
		for _, item := range data {
			write(fd, item)
		}
	case net.IP:
		var af int32 = -1
		switch len(data) {
		case net.IPv4len:
			af = unix.AF_INET
		case net.IPv6len:
			af = unix.AF_INET6
		}
		var bytes []byte
		if af < 0 {
			bytes = make([]byte, 0)
		} else {
			bytes = data
		}
		write(fd, af)
		write(fd, int32(len(bytes)))
		write(fd, bytes)
	case []net.IP:
		write(fd, int32(len(data)))
		for _, item := range data {
			write(fd, item)
		}
	default:
		v := reflect.ValueOf(data)
		switch v.Kind() {
		case reflect.Struct:
			for i, n := 0, v.NumField(); i < n; i++ {
				write(fd, v.Field(i).Interface())
			}
		default:
			panic(fmt.Sprintf("Invalid structure to write NSLCD protocol data from: %T ( %#v )", data, data))
		}
	}
}

// Assert that we *will* read n bytes.  If we know now that < n bytes
// will be available, then this will let us avoid an allocation.
func willread(fd io.Reader, n int64) {
	if lfd, ok := fd.(*io.LimitedReader); ok {
		if n > lfd.N {
			npanic(NslcdError(io.EOF.Error()))
		}
	}
}

// Read an object from a stream.  In the event of an error, this
// function may panic(NslcdError)!  Handle it!
func read(fd io.Reader, data interface{}) {
	switch data := data.(type) {
	// basic data types
	case nslcdObjectPtr:
		data.nslcdRead(fd)
	case *[]byte:
		if len(*data) > 0 {
			_, err := io.ReadFull(fd, *data)
			if err != nil {
				npanic(NslcdError(err.Error()))
			}
		}
	case *int32:
		err := binary.Read(fd, binary.BigEndian, data)
		if err != nil {
			npanic(NslcdError(err.Error()))
		}
	// composite datatypes
	case *string:
		var len int32
		read(fd, &len)
		willread(fd, int64(len))
		buf := make([]byte, len)
		read(fd, &buf)
		*data = string(buf)
	case *[]string:
		var num int32
		read(fd, &num)
		willread(fd, int64(num * /* min size of a string is: */4))
		*data = make([]string, num)
		for i := 0; i < int(num); i++ {
			read(fd, &((*data)[i]))
		}
	case *net.IP:
		var af int32
		read(fd, &af)
		var _len int32
		switch af {
		case unix.AF_INET:
			_len = net.IPv4len
		case unix.AF_INET6:
			_len = net.IPv6len
		default:
			npanic(NslcdError(fmt.Sprintf("incorrect address family specified: %d", af)))
		}
		var len int32
		read(fd, &len)
		if len != _len {
			npanic(NslcdError(fmt.Sprintf("address length incorrect: %d", len)))
		}
		buf := make([]byte, len)
		read(fd, &buf)
		*data = buf
	case *[]net.IP:
		var num int32
		read(fd, &num)
		willread(fd, int64(num * /* min size of an IP is: */net.IPv4len))
		*data = make([]net.IP, num)
		for i := 0; i < int(num); i++ {
			read(fd, &((*data)[i]))
		}
	default:
		p := reflect.ValueOf(data)
		v := reflect.Indirect(p)
		if p == v || v.Kind() != reflect.Struct {
			panic(fmt.Sprintf("The argument to nslcd_proto.Read() must be a pointer: %T ( %#v )", data, data))
		}
		for i, n := 0, v.NumField(); i < n; i++ {
			read(fd, v.Field(i).Addr().Interface())
		}
	}
}