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encoding/base32: don't panic when decoding "AAAA==".

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Edit encoding/base64's internals and tests to match encoding/base32.

Properly handling line breaks in padding is left for another CL.

R=dsymonds
CC=golang-dev
https://golang.org/cl/7693044
This commit is contained in:
Nigel Tao 2013-03-12 11:07:36 +11:00
parent 1b3c969ac3
commit 79d06d7286
4 changed files with 77 additions and 39 deletions
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34
src/pkg/encoding/base32/base32.go
View File

@ -236,7 +236,6 @@ func (enc *Encoding) decode(dst, src []byte) (n int, end bool, err error) {
var dbuf [8]byte
dlen := 8
// do the top bytes contain any data?
for j := 0; j < 8; {
if len(src) == 0 {
return n, false, CorruptInputError(len(osrc) - len(src) - j)
@ -248,15 +247,26 @@ func (enc *Encoding) decode(dst, src []byte) (n int, end bool, err error) {
continue
}
if in == '=' && j >= 2 && len(src) < 8 {
// We've reached the end and there's
// padding, the rest should be padded
for k := 0; k < 8-j-1; k++ {
// We've reached the end and there's padding
if len(src)+j < 8-1 {
// not enough padding
return n, false, CorruptInputError(len(osrc))
}
for k := 0; k < 8-1-j; k++ {
if len(src) > k && src[k] != '=' {
// incorrect padding
return n, false, CorruptInputError(len(osrc) - len(src) + k - 1)
}
}
dlen = j
end = true
dlen, end = j, true
// 7, 5 and 2 are not valid padding lengths, and so 1, 3 and 6 are not
// valid dlen values. See RFC 4648 Section 6 "Base 32 Encoding" listing
// the five valid padding lengths, and Section 9 "Illustrations and
// Examples" for an illustration for how the the 1st, 3rd and 6th base32
// src bytes do not yield enough information to decode a dst byte.
if dlen == 1 || dlen == 3 || dlen == 6 {
return n, false, CorruptInputError(len(osrc) - len(src) - 1)
}
break
}
dbuf[j] = enc.decodeMap[in]
@ -269,16 +279,16 @@ func (enc *Encoding) decode(dst, src []byte) (n int, end bool, err error) {
// Pack 8x 5-bit source blocks into 5 byte destination
// quantum
switch dlen {
case 7, 8:
case 8:
dst[4] = dbuf[6]<<5 | dbuf[7]
fallthrough
case 6, 5:
case 7:
dst[3] = dbuf[4]<<7 | dbuf[5]<<2 | dbuf[6]>>3
fallthrough
case 4:
case 5:
dst[2] = dbuf[3]<<4 | dbuf[4]>>1
fallthrough
case 3:
case 4:
dst[1] = dbuf[1]<<6 | dbuf[2]<<1 | dbuf[3]>>4
fallthrough
case 2:
@ -288,11 +298,11 @@ func (enc *Encoding) decode(dst, src []byte) (n int, end bool, err error) {
switch dlen {
case 2:
n += 1
case 3, 4:
case 4:
n += 2
case 5:
n += 3
case 6, 7:
case 7:
n += 4
case 8:
n += 5

43
src/pkg/encoding/base32/base32_test.go
View File

@ -137,27 +137,48 @@ func TestDecoderBuffering(t *testing.T) {
}
func TestDecodeCorrupt(t *testing.T) {
type corrupt struct {
e string
p int
}
examples := []corrupt{
testCases := []struct {
input string
offset int // -1 means no corruption.
}{
{"", -1},
{"!!!!", 0},
{"x===", 0},
{"AA=A====", 2},
{"AAA=AAAA", 3},
{"MMMMMMMMM", 8},
{"MMMMMM", 0},
{"A=", 1},
{"AA=", 3},
{"AA==", 4},
{"AA===", 5},
{"AAAA=", 5},
{"AAAA==", 6},
{"AAAAA=", 6},
{"AAAAA==", 7},
{"A=======", 1},
{"AA======", -1},
{"AAA=====", 3},
{"AAAA====", -1},
{"AAAAA===", -1},
{"AAAAAA==", 6},
{"AAAAAAA=", -1},
{"AAAAAAAA", -1},
}
for _, e := range examples {
dbuf := make([]byte, StdEncoding.DecodedLen(len(e.e)))
_, err := StdEncoding.Decode(dbuf, []byte(e.e))
for _, tc := range testCases {
dbuf := make([]byte, StdEncoding.DecodedLen(len(tc.input)))
_, err := StdEncoding.Decode(dbuf, []byte(tc.input))
if tc.offset == -1 {
if err != nil {
t.Error("Decoder wrongly detected coruption in", tc.input)
}
continue
}
switch err := err.(type) {
case CorruptInputError:
testEqual(t, "Corruption in %q at offset %v, want %v", e.e, int(err), e.p)
testEqual(t, "Corruption in %q at offset %v, want %v", tc.input, int(err), tc.offset)
default:
t.Error("Decoder failed to detect corruption in", e)
t.Error("Decoder failed to detect corruption in", tc)
}
}
}

8
src/pkg/encoding/base64/base64.go
View File

@ -227,9 +227,8 @@ func (enc *Encoding) decode(dst, src []byte) (n int, end bool, err error) {
continue
}
if in == '=' && j >= 2 && len(src) < 4 {
// We've reached the end and there's
// padding
if len(src) == 0 && j == 2 {
// We've reached the end and there's padding
if len(src)+j < 4-1 {
// not enough padding
return n, false, CorruptInputError(len(osrc))
}
@ -237,8 +236,7 @@ func (enc *Encoding) decode(dst, src []byte) (n int, end bool, err error) {
// incorrect padding
return n, false, CorruptInputError(len(osrc) - len(src) - 1)
}
dlen = j
end = true
dlen, end = j, true
break
}
dbuf[j] = enc.decodeMap[in]

31
src/pkg/encoding/base64/base64_test.go
View File

@ -142,11 +142,11 @@ func TestDecoderBuffering(t *testing.T) {
}
func TestDecodeCorrupt(t *testing.T) {
type corrupt struct {
e string
p int
}
examples := []corrupt{
testCases := []struct {
input string
offset int // -1 means no corruption.
}{
{"", -1},
{"!!!!", 0},
{"x===", 1},
{"AA=A", 2},
@ -154,18 +154,27 @@ func TestDecodeCorrupt(t *testing.T) {
{"AAAAA", 4},
{"AAAAAA", 4},
{"A=", 1},
{"A==", 1},
{"AA=", 3},
{"AA==", -1},
{"AAA=", -1},
{"AAAA", -1},
{"AAAAAA=", 7},
}
for _, e := range examples {
dbuf := make([]byte, StdEncoding.DecodedLen(len(e.e)))
_, err := StdEncoding.Decode(dbuf, []byte(e.e))
for _, tc := range testCases {
dbuf := make([]byte, StdEncoding.DecodedLen(len(tc.input)))
_, err := StdEncoding.Decode(dbuf, []byte(tc.input))
if tc.offset == -1 {
if err != nil {
t.Error("Decoder wrongly detected coruption in", tc.input)
}
continue
}
switch err := err.(type) {
case CorruptInputError:
testEqual(t, "Corruption in %q at offset %v, want %v", e.e, int(err), e.p)
testEqual(t, "Corruption in %q at offset %v, want %v", tc.input, int(err), tc.offset)
default:
t.Error("Decoder failed to detect corruption in", e)
t.Error("Decoder failed to detect corruption in", tc)
}
}
}