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compress/zlib: tighten header CINFO check

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RFC 1950 section 2.2 "Data format" says "CINFO (Compression info)... For
CM = 8... Values of CINFO above 7 are not allowed".

Change-Id: Ibbc1213125c7dc045f09901ee7746660e90b5fcd
Reviewed-on: https://go-review.googlesource.com/c/go/+/395734
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Trust: Nigel Tao <nigeltao@golang.org>
This commit is contained in:
Nigel Tao 2022-03-25 10:33:21 +11:00
parent eee6f9f825
commit d1060d8e82
2 changed files with 13 additions and 3 deletions
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7
src/compress/zlib/reader.go
View File

@ -32,7 +32,10 @@ import (
"io" "io"
) )
const zlibDeflate = 8 const (
zlibDeflate = 8
zlibMaxWindow = 7
)
var ( var (
// ErrChecksum is returned when reading ZLIB data that has an invalid checksum. // ErrChecksum is returned when reading ZLIB data that has an invalid checksum.
@ -143,7 +146,7 @@ func (z *reader) Reset(r io.Reader, dict []byte) error {
return z.err return z.err
} }
h := uint(z.scratch[0])<<8 | uint(z.scratch[1]) h := uint(z.scratch[0])<<8 | uint(z.scratch[1])
if (z.scratch[0]&0x0f != zlibDeflate) || (h%31 != 0) { if (z.scratch[0]&0x0f != zlibDeflate) || (z.scratch[0]>>4 > zlibMaxWindow) || (h%31 != 0) {
z.err = ErrHeader z.err = ErrHeader
return z.err return z.err
} }

9
src/compress/zlib/reader_test.go
View File

@ -65,7 +65,14 @@ var zlibTests = []zlibTest{
nil, nil,
}, },
{ {
"bad header", "bad header (CINFO)",
"",
[]byte{0x88, 0x98, 0x03, 0x00, 0x00, 0x00, 0x00, 0x01},
nil,
ErrHeader,
},
{
"bad header (FCHECK)",
"", "",
[]byte{0x78, 0x9f, 0x03, 0x00, 0x00, 0x00, 0x00, 0x01}, []byte{0x78, 0x9f, 0x03, 0x00, 0x00, 0x00, 0x00, 0x01},
nil, nil,