1 files changed, 301 insertions, 0 deletions
diff --git a/src/internal/fuzz/mutators_byteslice.go b/src/internal/fuzz/mutators_byteslice.go
new file mode 100644
index 00000000000..7c96b5920ea
--- /dev/null
+++ b/src/internal/fuzz/mutators_byteslice.go
@@ -0,0 +1,301 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fuzz
+
+// byteSliceRemoveBytes removes a random chunk of bytes from b.
+func byteSliceRemoveBytes(m *mutator, b []byte) []byte {
+	if len(b) <= 1 {
+		return nil
+	}
+	pos0 := m.rand(len(b))
+	pos1 := pos0 + m.chooseLen(len(b)-pos0)
+	copy(b[pos0:], b[pos1:])
+	b = b[:len(b)-(pos1-pos0)]
+	return b
+}
+
+// byteSliceInsertRandomBytes inserts a chunk of random bytes into b at a random
+// position.
+func byteSliceInsertRandomBytes(m *mutator, b []byte) []byte {
+	pos := m.rand(len(b) + 1)
+	n := m.chooseLen(1024)
+	if len(b)+n >= cap(b) {
+		return nil
+	}
+	b = b[:len(b)+n]
+	copy(b[pos+n:], b[pos:])
+	for i := 0; i < n; i++ {
+		b[pos+i] = byte(m.rand(256))
+	}
+	return b
+}
+
+// byteSliceDuplicateBytes duplicates a chunk of bytes in b and inserts it into
+// a random position.
+func byteSliceDuplicateBytes(m *mutator, b []byte) []byte {
+	if len(b) <= 1 {
+		return nil
+	}
+	src := m.rand(len(b))
+	dst := m.rand(len(b))
+	for dst == src {
+		dst = m.rand(len(b))
+	}
+	n := m.chooseLen(len(b) - src)
+	// Use the end of the slice as scratch space to avoid doing an
+	// allocation. If the slice is too small abort and try something
+	// else.
+	if len(b)+(n*2) >= cap(b) {
+		return nil
+	}
+	end := len(b)
+	// Increase the size of b to fit the duplicated block as well as
+	// some extra working space
+	b = b[:end+(n*2)]
+	// Copy the block of bytes we want to duplicate to the end of the
+	// slice
+	copy(b[end+n:], b[src:src+n])
+	// Shift the bytes after the splice point n positions to the right
+	// to make room for the new block
+	copy(b[dst+n:end+n], b[dst:end])
+	// Insert the duplicate block into the splice point
+	copy(b[dst:], b[end+n:])
+	b = b[:end+n]
+	return b
+}
+
+// byteSliceOverwriteBytes overwrites a chunk of b with another chunk of b.
+func byteSliceOverwriteBytes(m *mutator, b []byte) []byte {
+	if len(b) <= 1 {
+		return nil
+	}
+	src := m.rand(len(b))
+	dst := m.rand(len(b))
+	for dst == src {
+		dst = m.rand(len(b))
+	}
+	n := m.chooseLen(len(b) - src - 1)
+	copy(b[dst:], b[src:src+n])
+	return b
+}
+
+// byteSliceBitFlip flips a random bit in a random byte in b.
+func byteSliceBitFlip(m *mutator, b []byte) []byte {
+	if len(b) == 0 {
+		return nil
+	}
+	pos := m.rand(len(b))
+	b[pos] ^= 1 << uint(m.rand(8))
+	return b
+}
+
+// byteSliceXORByte XORs a random byte in b with a random value.
+func byteSliceXORByte(m *mutator, b []byte) []byte {
+	if len(b) == 0 {
+		return nil
+	}
+	pos := m.rand(len(b))
+	// In order to avoid a no-op (where the random value matches
+	// the existing value), use XOR instead of just setting to
+	// the random value.
+	b[pos] ^= byte(1 + m.rand(255))
+	return b
+}
+
+// byteSliceSwapByte swaps two random bytes in b.
+func byteSliceSwapByte(m *mutator, b []byte) []byte {
+	if len(b) <= 1 {
+		return nil
+	}
+	src := m.rand(len(b))
+	dst := m.rand(len(b))
+	for dst == src {
+		dst = m.rand(len(b))
+	}
+	b[src], b[dst] = b[dst], b[src]
+	return b
+}
+
+// byteSliceArithmeticUint8 adds/subtracts from a random byte in b.
+func byteSliceArithmeticUint8(m *mutator, b []byte) []byte {
+	if len(b) == 0 {
+		return nil
+	}
+	pos := m.rand(len(b))
+	v := byte(m.rand(35) + 1)
+	if m.r.bool() {
+		b[pos] += v
+	} else {
+		b[pos] -= v
+	}
+	return b
+}
+
+// byteSliceArithmeticUint16 adds/subtracts from a random uint16 in b.
+func byteSliceArithmeticUint16(m *mutator, b []byte) []byte {
+	if len(b) < 2 {
+		return nil
+	}
+	v := uint16(m.rand(35) + 1)
+	if m.r.bool() {
+		v = 0 - v
+	}
+	pos := m.rand(len(b) - 1)
+	enc := m.randByteOrder()
+	enc.PutUint16(b[pos:], enc.Uint16(b[pos:])+v)
+	return b
+}
+
+// byteSliceArithmeticUint32 adds/subtracts from a random uint32 in b.
+func byteSliceArithmeticUint32(m *mutator, b []byte) []byte {
+	if len(b) < 4 {
+		return nil
+	}
+	v := uint32(m.rand(35) + 1)
+	if m.r.bool() {
+		v = 0 - v
+	}
+	pos := m.rand(len(b) - 3)
+	enc := m.randByteOrder()
+	enc.PutUint32(b[pos:], enc.Uint32(b[pos:])+v)
+	return b
+}
+
+// byteSliceArithmeticUint64 adds/subtracts from a random uint64 in b.
+func byteSliceArithmeticUint64(m *mutator, b []byte) []byte {
+	if len(b) < 8 {
+		return nil
+	}
+	v := uint64(m.rand(35) + 1)
+	if m.r.bool() {
+		v = 0 - v
+	}
+	pos := m.rand(len(b) - 7)
+	enc := m.randByteOrder()
+	enc.PutUint64(b[pos:], enc.Uint64(b[pos:])+v)
+	return b
+}
+
+// byteSliceOverwriteInterestingUint8 overwrites a random byte in b with an interesting
+// value.
+func byteSliceOverwriteInterestingUint8(m *mutator, b []byte) []byte {
+	if len(b) == 0 {
+		return nil
+	}
+	pos := m.rand(len(b))
+	b[pos] = byte(interesting8[m.rand(len(interesting8))])
+	return b
+}
+
+// byteSliceOverwriteInterestingUint16 overwrites a random uint16 in b with an interesting
+// value.
+func byteSliceOverwriteInterestingUint16(m *mutator, b []byte) []byte {
+	if len(b) < 2 {
+		return nil
+	}
+	pos := m.rand(len(b) - 1)
+	v := uint16(interesting16[m.rand(len(interesting16))])
+	m.randByteOrder().PutUint16(b[pos:], v)
+	return b
+}
+
+// byteSliceOverwriteInterestingUint32 overwrites a random uint16 in b with an interesting
+// value.
+func byteSliceOverwriteInterestingUint32(m *mutator, b []byte) []byte {
+	if len(b) < 4 {
+		return nil
+	}
+	pos := m.rand(len(b) - 3)
+	v := uint32(interesting32[m.rand(len(interesting32))])
+	m.randByteOrder().PutUint32(b[pos:], v)
+	return b
+}
+
+// byteSliceInsertConstantBytes inserts a chunk of constant bytes into a random position in b.
+func byteSliceInsertConstantBytes(m *mutator, b []byte) []byte {
+	if len(b) <= 1 {
+		return nil
+	}
+	dst := m.rand(len(b))
+	// TODO(rolandshoemaker,katiehockman): 4096 was mainly picked
+	// randomly. We may want to either pick a much larger value
+	// (AFL uses 32768, paired with a similar impl to chooseLen
+	// which biases towards smaller lengths that grow over time),
+	// or set the max based on characteristics of the corpus
+	// (libFuzzer sets a min/max based on the min/max size of
+	// entries in the corpus and then picks uniformly from
+	// that range).
+	n := m.chooseLen(4096)
+	if len(b)+n >= cap(b) {
+		return nil
+	}
+	b = b[:len(b)+n]
+	copy(b[dst+n:], b[dst:])
+	rb := byte(m.rand(256))
+	for i := dst; i < dst+n; i++ {
+		b[i] = rb
+	}
+	return b
+}
+
+// byteSliceOverwriteConstantBytes overwrites a chunk of b with constant bytes.
+func byteSliceOverwriteConstantBytes(m *mutator, b []byte) []byte {
+	if len(b) <= 1 {
+		return nil
+	}
+	dst := m.rand(len(b))
+	n := m.chooseLen(len(b) - dst)
+	rb := byte(m.rand(256))
+	for i := dst; i < dst+n; i++ {
+		b[i] = rb
+	}
+	return b
+}
+
+// byteSliceShuffleBytes shuffles a chunk of bytes in b.
+func byteSliceShuffleBytes(m *mutator, b []byte) []byte {
+	if len(b) <= 1 {
+		return nil
+	}
+	dst := m.rand(len(b))
+	n := m.chooseLen(len(b) - dst)
+	if n <= 2 {
+		return nil
+	}
+	// Start at the end of the range, and iterate backwards
+	// to dst, swapping each element with another element in
+	// dst:dst+n (Fisher-Yates shuffle).
+	for i := n - 1; i > 0; i-- {
+		j := m.rand(i + 1)
+		b[dst+i], b[dst+j] = b[dst+j], b[dst+i]
+	}
+	return b
+}
+
+// byteSliceSwapBytes swaps two chunks of bytes in b.
+func byteSliceSwapBytes(m *mutator, b []byte) []byte {
+	if len(b) <= 1 {
+		return nil
+	}
+	src := m.rand(len(b))
+	dst := m.rand(len(b))
+	for dst == src {
+		dst = m.rand(len(b))
+	}
+	n := m.chooseLen(len(b) - src - 1)
+	// Use the end of the slice as scratch space to avoid doing an
+	// allocation. If the slice is too small abort and try something
+	// else.
+	if len(b)+n >= cap(b) {
+		return nil
+	}
+	end := len(b)
+	b = b[:end+n]
+	copy(b[end:], b[dst:dst+n])
+	copy(b[dst:], b[src:src+n])
+	copy(b[src:], b[end:])
+	b = b[:end]
+	return b
+}