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BUGFIX: don't allocate more memory than what can be read from io.Reader #42

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Apr 22, 2024
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BUGFIX: don't allocate more memory than what can be read from io.Reader #42

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16 changes: 13 additions & 3 deletions ber.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ import (
"errors"
"fmt"
"io"
"io/ioutil"
"math"
"os"
"reflect"
Expand Down Expand Up @@ -352,13 +353,22 @@ func readPacket(reader io.Reader) (*Packet, int, error) {
if MaxPacketLengthBytes > 0 && int64(length) > MaxPacketLengthBytes {
return nil, read, fmt.Errorf("length %d greater than maximum %d", length, MaxPacketLengthBytes)
}
content := make([]byte, length)

var content []byte
if length > 0 {
_, err := io.ReadFull(reader, content)
// Read the content and limit it to the parsed length.
// If the content is less than the length, we return an EOF error.
content, err = ioutil.ReadAll(io.LimitReader(reader, int64(length)))
if err == nil && len(content) < int(length) {
err = io.EOF
}
if err != nil {
return nil, read, unexpectedEOF(err)
}
read += length
read += len(content)
} else {
// If length == 0, we set the ByteValue to an empty slice
content = make([]byte, 0)
}

if p.ClassType == ClassUniversal {
Expand Down
5 changes: 0 additions & 5 deletions fuzz_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -30,11 +30,6 @@ func FuzzDecodePacket(f *testing.F) {
f.Add([]byte{0x09, 0x02, 0x85, 0x30})
f.Add([]byte{0x09, 0x01, 0xcf})

// Set a limit on the length decoded in readPacket() since the call to
// make([]byte, length) can allocate up to MaxPacketLengthBytes which is
// currently 2 GB. This can cause memory related crashes when fuzzing in
// parallel or on memory constrained devices.
MaxPacketLengthBytes = 65536
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This PR fixes the issue described above.

f.Fuzz(func(t *testing.T, data []byte) {
stime := time.Now()
p, err := DecodePacketErr(data)
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