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encoding/base32: reduce the overflow risk when computing encode/decode length
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7141d1e6d8
commit
652c8c6712
@ -271,7 +271,7 @@ func NewEncoder(enc *Encoding, w io.Writer) io.WriteCloser {
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// of an input buffer of length n.
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func (enc *Encoding) EncodedLen(n int) int {
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if enc.padChar == NoPadding {
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return (n*8 + 4) / 5
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return n/5*8 + (n%5*8+4)/5
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}
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return (n + 4) / 5 * 8
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}
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@ -545,8 +545,7 @@ func NewDecoder(enc *Encoding, r io.Reader) io.Reader {
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// corresponding to n bytes of base32-encoded data.
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func (enc *Encoding) DecodedLen(n int) int {
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if enc.padChar == NoPadding {
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return n * 5 / 8
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return n/8*5 + n%8*5/8
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}
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return n / 8 * 5
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}
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@ -8,6 +8,8 @@ import (
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"bytes"
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"errors"
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"io"
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"math"
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"strconv"
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"strings"
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"testing"
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)
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@ -679,52 +681,86 @@ func TestBufferedDecodingPadding(t *testing.T) {
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}
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}
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func TestEncodedDecodedLen(t *testing.T) {
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func TestEncodedLen(t *testing.T) {
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var rawStdEncoding = StdEncoding.WithPadding(NoPadding)
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type test struct {
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in int
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wantEnc int
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wantDec int
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enc *Encoding
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n int
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want int64
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}
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data := bytes.Repeat([]byte("x"), 100)
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for _, test := range []struct {
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name string
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enc *Encoding
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cases []test
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}{
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{"StdEncoding", StdEncoding, []test{
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{0, 0, 0},
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{1, 8, 5},
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{5, 8, 5},
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{6, 16, 10},
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{10, 16, 10},
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}},
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{"NoPadding", StdEncoding.WithPadding(NoPadding), []test{
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{0, 0, 0},
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{1, 2, 1},
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{2, 4, 2},
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{5, 8, 5},
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{6, 10, 6},
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{7, 12, 7},
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{10, 16, 10},
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{11, 18, 11},
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}},
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} {
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t.Run(test.name, func(t *testing.T) {
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for _, tc := range test.cases {
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encLen := test.enc.EncodedLen(tc.in)
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decLen := test.enc.DecodedLen(encLen)
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enc := test.enc.EncodeToString(data[:tc.in])
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if len(enc) != encLen {
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t.Fatalf("EncodedLen(%d) = %d but encoded to %q (%d)", tc.in, encLen, enc, len(enc))
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}
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if encLen != tc.wantEnc {
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t.Fatalf("EncodedLen(%d) = %d; want %d", tc.in, encLen, tc.wantEnc)
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}
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if decLen != tc.wantDec {
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t.Fatalf("DecodedLen(%d) = %d; want %d", encLen, decLen, tc.wantDec)
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}
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}
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})
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tests := []test{
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{StdEncoding, 0, 0},
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{StdEncoding, 1, 8},
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{StdEncoding, 2, 8},
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{StdEncoding, 3, 8},
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{StdEncoding, 4, 8},
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{StdEncoding, 5, 8},
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{StdEncoding, 6, 16},
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{StdEncoding, 10, 16},
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{StdEncoding, 11, 24},
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{rawStdEncoding, 0, 0},
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{rawStdEncoding, 1, 2},
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{rawStdEncoding, 2, 4},
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{rawStdEncoding, 3, 5},
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{rawStdEncoding, 4, 7},
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{rawStdEncoding, 5, 8},
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{rawStdEncoding, 6, 10},
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{rawStdEncoding, 7, 12},
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{rawStdEncoding, 10, 16},
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{rawStdEncoding, 11, 18},
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}
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// check overflow
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switch strconv.IntSize {
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case 32:
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tests = append(tests, test{rawStdEncoding, (math.MaxInt-4)/8 + 1, 429496730})
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tests = append(tests, test{rawStdEncoding, math.MaxInt/8*5 + 4, math.MaxInt})
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case 64:
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tests = append(tests, test{rawStdEncoding, (math.MaxInt-4)/8 + 1, 1844674407370955162})
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tests = append(tests, test{rawStdEncoding, math.MaxInt/8*5 + 4, math.MaxInt})
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}
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for _, tt := range tests {
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if got := tt.enc.EncodedLen(tt.n); int64(got) != tt.want {
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t.Errorf("EncodedLen(%d): got %d, want %d", tt.n, got, tt.want)
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}
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}
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}
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func TestDecodedLen(t *testing.T) {
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var rawStdEncoding = StdEncoding.WithPadding(NoPadding)
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type test struct {
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enc *Encoding
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n int
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want int64
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}
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tests := []test{
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{StdEncoding, 0, 0},
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{StdEncoding, 8, 5},
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{StdEncoding, 16, 10},
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{StdEncoding, 24, 15},
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{rawStdEncoding, 0, 0},
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{rawStdEncoding, 2, 1},
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{rawStdEncoding, 4, 2},
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{rawStdEncoding, 5, 3},
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{rawStdEncoding, 7, 4},
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{rawStdEncoding, 8, 5},
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{rawStdEncoding, 10, 6},
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{rawStdEncoding, 12, 7},
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{rawStdEncoding, 16, 10},
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{rawStdEncoding, 18, 11},
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}
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// check overflow
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switch strconv.IntSize {
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case 32:
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tests = append(tests, test{rawStdEncoding, math.MaxInt/5 + 1, 268435456})
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tests = append(tests, test{rawStdEncoding, math.MaxInt, 1342177279})
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case 64:
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tests = append(tests, test{rawStdEncoding, math.MaxInt/5 + 1, 1152921504606846976})
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tests = append(tests, test{rawStdEncoding, math.MaxInt, 5764607523034234879})
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}
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for _, tt := range tests {
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if got := tt.enc.DecodedLen(tt.n); int64(got) != tt.want {
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t.Errorf("DecodedLen(%d): got %d, want %d", tt.n, got, tt.want)
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}
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}
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}
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