File: fuzz.go

package info (click to toggle)
golang-github-google-gofuzz 0.0~git20170612.24818f7-1~bpo9%2B1
  • links: PTS, VCS
  • area: main
  • in suites: stretch-backports
  • size: 116 kB
  • sloc: makefile: 2
file content (487 lines) | stat: -rw-r--r-- 13,590 bytes parent folder | download | duplicates (2)
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
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
/*
Copyright 2014 Google Inc. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package fuzz

import (
	"fmt"
	"math/rand"
	"reflect"
	"time"
)

// fuzzFuncMap is a map from a type to a fuzzFunc that handles that type.
type fuzzFuncMap map[reflect.Type]reflect.Value

// Fuzzer knows how to fill any object with random fields.
type Fuzzer struct {
	fuzzFuncs        fuzzFuncMap
	defaultFuzzFuncs fuzzFuncMap
	r                *rand.Rand
	nilChance        float64
	minElements      int
	maxElements      int
	maxDepth         int
}

// New returns a new Fuzzer. Customize your Fuzzer further by calling Funcs,
// RandSource, NilChance, or NumElements in any order.
func New() *Fuzzer {
	return NewWithSeed(time.Now().UnixNano())
}

func NewWithSeed(seed int64) *Fuzzer {
	f := &Fuzzer{
		defaultFuzzFuncs: fuzzFuncMap{
			reflect.TypeOf(&time.Time{}): reflect.ValueOf(fuzzTime),
		},

		fuzzFuncs:   fuzzFuncMap{},
		r:           rand.New(rand.NewSource(seed)),
		nilChance:   .2,
		minElements: 1,
		maxElements: 10,
		maxDepth:    100,
	}
	return f
}

// Funcs adds each entry in fuzzFuncs as a custom fuzzing function.
//
// Each entry in fuzzFuncs must be a function taking two parameters.
// The first parameter must be a pointer or map. It is the variable that
// function will fill with random data. The second parameter must be a
// fuzz.Continue, which will provide a source of randomness and a way
// to automatically continue fuzzing smaller pieces of the first parameter.
//
// These functions are called sensibly, e.g., if you wanted custom string
// fuzzing, the function `func(s *string, c fuzz.Continue)` would get
// called and passed the address of strings. Maps and pointers will always
// be made/new'd for you, ignoring the NilChange option. For slices, it
// doesn't make much sense to  pre-create them--Fuzzer doesn't know how
// long you want your slice--so take a pointer to a slice, and make it
// yourself. (If you don't want your map/pointer type pre-made, take a
// pointer to it, and make it yourself.) See the examples for a range of
// custom functions.
func (f *Fuzzer) Funcs(fuzzFuncs ...interface{}) *Fuzzer {
	for i := range fuzzFuncs {
		v := reflect.ValueOf(fuzzFuncs[i])
		if v.Kind() != reflect.Func {
			panic("Need only funcs!")
		}
		t := v.Type()
		if t.NumIn() != 2 || t.NumOut() != 0 {
			panic("Need 2 in and 0 out params!")
		}
		argT := t.In(0)
		switch argT.Kind() {
		case reflect.Ptr, reflect.Map:
		default:
			panic("fuzzFunc must take pointer or map type")
		}
		if t.In(1) != reflect.TypeOf(Continue{}) {
			panic("fuzzFunc's second parameter must be type fuzz.Continue")
		}
		f.fuzzFuncs[argT] = v
	}
	return f
}

// RandSource causes f to get values from the given source of randomness.
// Use if you want deterministic fuzzing.
func (f *Fuzzer) RandSource(s rand.Source) *Fuzzer {
	f.r = rand.New(s)
	return f
}

// NilChance sets the probability of creating a nil pointer, map, or slice to
// 'p'. 'p' should be between 0 (no nils) and 1 (all nils), inclusive.
func (f *Fuzzer) NilChance(p float64) *Fuzzer {
	if p < 0 || p > 1 {
		panic("p should be between 0 and 1, inclusive.")
	}
	f.nilChance = p
	return f
}

// NumElements sets the minimum and maximum number of elements that will be
// added to a non-nil map or slice.
func (f *Fuzzer) NumElements(atLeast, atMost int) *Fuzzer {
	if atLeast > atMost {
		panic("atLeast must be <= atMost")
	}
	if atLeast < 0 {
		panic("atLeast must be >= 0")
	}
	f.minElements = atLeast
	f.maxElements = atMost
	return f
}

func (f *Fuzzer) genElementCount() int {
	if f.minElements == f.maxElements {
		return f.minElements
	}
	return f.minElements + f.r.Intn(f.maxElements-f.minElements+1)
}

func (f *Fuzzer) genShouldFill() bool {
	return f.r.Float64() > f.nilChance
}

// MaxDepth sets the maximum number of recursive fuzz calls that will be made
// before stopping.  This includes struct members, pointers, and map and slice
// elements.
func (f *Fuzzer) MaxDepth(d int) *Fuzzer {
	f.maxDepth = d
	return f
}

// Fuzz recursively fills all of obj's fields with something random.  First
// this tries to find a custom fuzz function (see Funcs).  If there is no
// custom function this tests whether the object implements fuzz.Interface and,
// if so, calls Fuzz on it to fuzz itself.  If that fails, this will see if
// there is a default fuzz function provided by this package.  If all of that
// fails, this will generate random values for all primitive fields and then
// recurse for all non-primitives.
//
// This is safe for cyclic or tree-like structs, up to a limit.  Use the
// MaxDepth method to adjust how deep you need it to recurse.
//
// obj must be a pointer. Only exported (public) fields can be set (thanks,
// golang :/ ) Intended for tests, so will panic on bad input or unimplemented
// fields.
func (f *Fuzzer) Fuzz(obj interface{}) {
	v := reflect.ValueOf(obj)
	if v.Kind() != reflect.Ptr {
		panic("needed ptr!")
	}
	v = v.Elem()
	f.fuzzWithContext(v, 0)
}

// FuzzNoCustom is just like Fuzz, except that any custom fuzz function for
// obj's type will not be called and obj will not be tested for fuzz.Interface
// conformance.  This applies only to obj and not other instances of obj's
// type.
// Not safe for cyclic or tree-like structs!
// obj must be a pointer. Only exported (public) fields can be set (thanks, golang :/ )
// Intended for tests, so will panic on bad input or unimplemented fields.
func (f *Fuzzer) FuzzNoCustom(obj interface{}) {
	v := reflect.ValueOf(obj)
	if v.Kind() != reflect.Ptr {
		panic("needed ptr!")
	}
	v = v.Elem()
	f.fuzzWithContext(v, flagNoCustomFuzz)
}

const (
	// Do not try to find a custom fuzz function.  Does not apply recursively.
	flagNoCustomFuzz uint64 = 1 << iota
)

func (f *Fuzzer) fuzzWithContext(v reflect.Value, flags uint64) {
	fc := &fuzzerContext{fuzzer: f}
	fc.doFuzz(v, flags)
}

// fuzzerContext carries context about a single fuzzing run, which lets Fuzzer
// be thread-safe.
type fuzzerContext struct {
	fuzzer   *Fuzzer
	curDepth int
}

func (fc *fuzzerContext) doFuzz(v reflect.Value, flags uint64) {
	if fc.curDepth >= fc.fuzzer.maxDepth {
		return
	}
	fc.curDepth++
	defer func() { fc.curDepth-- }()

	if !v.CanSet() {
		return
	}

	if flags&flagNoCustomFuzz == 0 {
		// Check for both pointer and non-pointer custom functions.
		if v.CanAddr() && fc.tryCustom(v.Addr()) {
			return
		}
		if fc.tryCustom(v) {
			return
		}
	}

	if fn, ok := fillFuncMap[v.Kind()]; ok {
		fn(v, fc.fuzzer.r)
		return
	}
	switch v.Kind() {
	case reflect.Map:
		if fc.fuzzer.genShouldFill() {
			v.Set(reflect.MakeMap(v.Type()))
			n := fc.fuzzer.genElementCount()
			for i := 0; i < n; i++ {
				key := reflect.New(v.Type().Key()).Elem()
				fc.doFuzz(key, 0)
				val := reflect.New(v.Type().Elem()).Elem()
				fc.doFuzz(val, 0)
				v.SetMapIndex(key, val)
			}
			return
		}
		v.Set(reflect.Zero(v.Type()))
	case reflect.Ptr:
		if fc.fuzzer.genShouldFill() {
			v.Set(reflect.New(v.Type().Elem()))
			fc.doFuzz(v.Elem(), 0)
			return
		}
		v.Set(reflect.Zero(v.Type()))
	case reflect.Slice:
		if fc.fuzzer.genShouldFill() {
			n := fc.fuzzer.genElementCount()
			v.Set(reflect.MakeSlice(v.Type(), n, n))
			for i := 0; i < n; i++ {
				fc.doFuzz(v.Index(i), 0)
			}
			return
		}
		v.Set(reflect.Zero(v.Type()))
	case reflect.Array:
		if fc.fuzzer.genShouldFill() {
			n := v.Len()
			for i := 0; i < n; i++ {
				fc.doFuzz(v.Index(i), 0)
			}
			return
		}
		v.Set(reflect.Zero(v.Type()))
	case reflect.Struct:
		for i := 0; i < v.NumField(); i++ {
			fc.doFuzz(v.Field(i), 0)
		}
	case reflect.Chan:
		fallthrough
	case reflect.Func:
		fallthrough
	case reflect.Interface:
		fallthrough
	default:
		panic(fmt.Sprintf("Can't handle %#v", v.Interface()))
	}
}

// tryCustom searches for custom handlers, and returns true iff it finds a match
// and successfully randomizes v.
func (fc *fuzzerContext) tryCustom(v reflect.Value) bool {
	// First: see if we have a fuzz function for it.
	doCustom, ok := fc.fuzzer.fuzzFuncs[v.Type()]
	if !ok {
		// Second: see if it can fuzz itself.
		if v.CanInterface() {
			intf := v.Interface()
			if fuzzable, ok := intf.(Interface); ok {
				fuzzable.Fuzz(Continue{fc: fc, Rand: fc.fuzzer.r})
				return true
			}
		}
		// Finally: see if there is a default fuzz function.
		doCustom, ok = fc.fuzzer.defaultFuzzFuncs[v.Type()]
		if !ok {
			return false
		}
	}

	switch v.Kind() {
	case reflect.Ptr:
		if v.IsNil() {
			if !v.CanSet() {
				return false
			}
			v.Set(reflect.New(v.Type().Elem()))
		}
	case reflect.Map:
		if v.IsNil() {
			if !v.CanSet() {
				return false
			}
			v.Set(reflect.MakeMap(v.Type()))
		}
	default:
		return false
	}

	doCustom.Call([]reflect.Value{v, reflect.ValueOf(Continue{
		fc:   fc,
		Rand: fc.fuzzer.r,
	})})
	return true
}

// Interface represents an object that knows how to fuzz itself.  Any time we
// find a type that implements this interface we will delegate the act of
// fuzzing itself.
type Interface interface {
	Fuzz(c Continue)
}

// Continue can be passed to custom fuzzing functions to allow them to use
// the correct source of randomness and to continue fuzzing their members.
type Continue struct {
	fc *fuzzerContext

	// For convenience, Continue implements rand.Rand via embedding.
	// Use this for generating any randomness if you want your fuzzing
	// to be repeatable for a given seed.
	*rand.Rand
}

// Fuzz continues fuzzing obj. obj must be a pointer.
func (c Continue) Fuzz(obj interface{}) {
	v := reflect.ValueOf(obj)
	if v.Kind() != reflect.Ptr {
		panic("needed ptr!")
	}
	v = v.Elem()
	c.fc.doFuzz(v, 0)
}

// FuzzNoCustom continues fuzzing obj, except that any custom fuzz function for
// obj's type will not be called and obj will not be tested for fuzz.Interface
// conformance.  This applies only to obj and not other instances of obj's
// type.
func (c Continue) FuzzNoCustom(obj interface{}) {
	v := reflect.ValueOf(obj)
	if v.Kind() != reflect.Ptr {
		panic("needed ptr!")
	}
	v = v.Elem()
	c.fc.doFuzz(v, flagNoCustomFuzz)
}

// RandString makes a random string up to 20 characters long. The returned string
// may include a variety of (valid) UTF-8 encodings.
func (c Continue) RandString() string {
	return randString(c.Rand)
}

// RandUint64 makes random 64 bit numbers.
// Weirdly, rand doesn't have a function that gives you 64 random bits.
func (c Continue) RandUint64() uint64 {
	return randUint64(c.Rand)
}

// RandBool returns true or false randomly.
func (c Continue) RandBool() bool {
	return randBool(c.Rand)
}

func fuzzInt(v reflect.Value, r *rand.Rand) {
	v.SetInt(int64(randUint64(r)))
}

func fuzzUint(v reflect.Value, r *rand.Rand) {
	v.SetUint(randUint64(r))
}

func fuzzTime(t *time.Time, c Continue) {
	var sec, nsec int64
	// Allow for about 1000 years of random time values, which keeps things
	// like JSON parsing reasonably happy.
	sec = c.Rand.Int63n(1000 * 365 * 24 * 60 * 60)
	c.Fuzz(&nsec)
	*t = time.Unix(sec, nsec)
}

var fillFuncMap = map[reflect.Kind]func(reflect.Value, *rand.Rand){
	reflect.Bool: func(v reflect.Value, r *rand.Rand) {
		v.SetBool(randBool(r))
	},
	reflect.Int:     fuzzInt,
	reflect.Int8:    fuzzInt,
	reflect.Int16:   fuzzInt,
	reflect.Int32:   fuzzInt,
	reflect.Int64:   fuzzInt,
	reflect.Uint:    fuzzUint,
	reflect.Uint8:   fuzzUint,
	reflect.Uint16:  fuzzUint,
	reflect.Uint32:  fuzzUint,
	reflect.Uint64:  fuzzUint,
	reflect.Uintptr: fuzzUint,
	reflect.Float32: func(v reflect.Value, r *rand.Rand) {
		v.SetFloat(float64(r.Float32()))
	},
	reflect.Float64: func(v reflect.Value, r *rand.Rand) {
		v.SetFloat(r.Float64())
	},
	reflect.Complex64: func(v reflect.Value, r *rand.Rand) {
		panic("unimplemented")
	},
	reflect.Complex128: func(v reflect.Value, r *rand.Rand) {
		panic("unimplemented")
	},
	reflect.String: func(v reflect.Value, r *rand.Rand) {
		v.SetString(randString(r))
	},
	reflect.UnsafePointer: func(v reflect.Value, r *rand.Rand) {
		panic("unimplemented")
	},
}

// randBool returns true or false randomly.
func randBool(r *rand.Rand) bool {
	if r.Int()&1 == 1 {
		return true
	}
	return false
}

type charRange struct {
	first, last rune
}

// choose returns a random unicode character from the given range, using the
// given randomness source.
func (r *charRange) choose(rand *rand.Rand) rune {
	count := int64(r.last - r.first)
	return r.first + rune(rand.Int63n(count))
}

var unicodeRanges = []charRange{
	{' ', '~'},           // ASCII characters
	{'\u00a0', '\u02af'}, // Multi-byte encoded characters
	{'\u4e00', '\u9fff'}, // Common CJK (even longer encodings)
}

// randString makes a random string up to 20 characters long. The returned string
// may include a variety of (valid) UTF-8 encodings.
func randString(r *rand.Rand) string {
	n := r.Intn(20)
	runes := make([]rune, n)
	for i := range runes {
		runes[i] = unicodeRanges[r.Intn(len(unicodeRanges))].choose(r)
	}
	return string(runes)
}

// randUint64 makes random 64 bit numbers.
// Weirdly, rand doesn't have a function that gives you 64 random bits.
func randUint64(r *rand.Rand) uint64 {
	return uint64(r.Uint32())<<32 | uint64(r.Uint32())
}