encoding/wkb: only limit allocation length not read length

encoding/wkb/line_string.go

@@ -15,12 +15,13 @@ func readLineString(r io.Reader, bom binary.ByteOrder) (orb.LineString, error) {
 		return nil, err
 	}
 
-	if num > maxPointsAlloc {
+	alloc := num
+	if alloc > maxPointsAlloc {
 		// invalid data can come in here and allocate tons of memory.
-		num = maxPointsAlloc
+		alloc = maxPointsAlloc
 	}
+	result := make(orb.LineString, 0, alloc)
 
-	result := make(orb.LineString, 0, num)
 	for i := 0; i < int(num); i++ {
 		p, err := readPoint(r, bom)
 		if err != nil {

encoding/wkb/line_string_test.go

@@ -16,6 +16,11 @@ var (
 )
 
 func TestLineString(t *testing.T) {
+	large := orb.LineString{}
+	for i := 0; i < maxPointsAlloc+100; i++ {
+		large = append(large, orb.Point{float64(i), float64(-i)})
+	}
+
 	cases := []struct {
 		name     string
 		data     []byte
@@ -26,6 +31,11 @@ func TestLineString(t *testing.T) {
 			data:     testLineStringData,
 			expected: testLineString,
 		},
+		{
+			name:     "large line string",
+			data:     MustMarshal(large),
+			expected: large,
+		},
 	}
 
 	for _, tc := range cases {

encoding/wkb/point.go

@@ -42,12 +42,13 @@ func readMultiPoint(r io.Reader, bom binary.ByteOrder) (orb.MultiPoint, error) {
 		return nil, err
 	}
 
-	if num > maxPointsAlloc {
+	alloc := num
+	if alloc > maxPointsAlloc {
 		// invalid data can come in here and allocate tons of memory.
-		num = maxPointsAlloc
+		alloc = maxPointsAlloc
 	}
+	result := make(orb.MultiPoint, 0, alloc)
 
-	result := make(orb.MultiPoint, 0, num)
 	for i := 0; i < int(num); i++ {
 		byteOrder, typ, err := readByteOrderType(r)
 		if err != nil {

encoding/wkb/point_test.go

@@ -86,6 +86,11 @@ var (
 )
 
 func TestMultiPoint(t *testing.T) {
+	large := orb.MultiPoint{}
+	for i := 0; i < maxPointsAlloc+100; i++ {
+		large = append(large, orb.Point{float64(i), float64(-i)})
+	}
+
 	cases := []struct {
 		name     string
 		data     []byte
@@ -101,6 +106,11 @@ func TestMultiPoint(t *testing.T) {
 			data:     testMultiPointSingleData,
 			expected: testMultiPointSingle,
 		},
+		{
+			name:     "large multi point",
+			data:     MustMarshal(large),
+			expected: large,
+		},
 	}
 
 	for _, tc := range cases {

encoding/wkb/wkb.go

@@ -23,7 +23,7 @@ const (
 const (
 	// limits so that bad data can't come in allocate way tons of memory.
 	// Well formed data with less elements will allocate the correct amount just fine.
-	maxPointsAlloc = 5000
+	maxPointsAlloc = 10000
 	maxMultiAlloc  = 100
 )