[release-branch.go1.18] archive/tar: limit size of headers

Set a 1MiB limit on special file blocks (PAX headers, GNU long names,
GNU link names), to avoid reading arbitrarily large amounts of data
into memory.

Thanks to Adam Korczynski (ADA Logics) and OSS-Fuzz for reporting
this issue.

Fixes CVE-2022-2879
Updates #54853
Fixes #55925

Change-Id: I85136d6ff1e0af101a112190e027987ab4335680
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1565555
Reviewed-by: Tatiana Bradley <tatianabradley@google.com>
Run-TryBot: Roland Shoemaker <bracewell@google.com>
Reviewed-by: Roland Shoemaker <bracewell@google.com>
(cherry picked from commit 6ee768cef6b82adf7a90dcf367a1699ef694f3b2)
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1590622
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Julie Qiu <julieqiu@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/438500
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Carlos Amedee <carlos@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

6 files changed, 56 insertions, 3 deletions

diff --git a/src/archive/tar/format.go b/src/archive/tar/format.go
index 21b9d9d4db..8898c438b5 100644
--- a/src/archive/tar/format.go
+++ b/src/archive/tar/format.go
@@ -143,6 +143,10 @@ const (
 	blockSize  = 512 // Size of each block in a tar stream
 	nameSize   = 100 // Max length of the name field in USTAR format
 	prefixSize = 155 // Max length of the prefix field in USTAR format
+
+	// Max length of a special file (PAX header, GNU long name or link).
+	// This matches the limit used by libarchive.
+	maxSpecialFileSize = 1 << 20
 )
 
 // blockPadding computes the number of bytes needed to pad offset up to the
diff --git a/src/archive/tar/reader.go b/src/archive/tar/reader.go
index 4b11909bc9..e609c15f27 100644
--- a/src/archive/tar/reader.go
+++ b/src/archive/tar/reader.go
@@ -103,7 +103,7 @@ func (tr *Reader) next() (*Header, error) {
 			continue // This is a meta header affecting the next header
 		case TypeGNULongName, TypeGNULongLink:
 			format.mayOnlyBe(FormatGNU)
-			realname, err := io.ReadAll(tr)
+			realname, err := readSpecialFile(tr)
 			if err != nil {
 				return nil, err
 			}
@@ -293,7 +293,7 @@ func mergePAX(hdr *Header, paxHdrs map[string]string) (err error) {
 // parsePAX parses PAX headers.
 // If an extended header (type 'x') is invalid, ErrHeader is returned
 func parsePAX(r io.Reader) (map[string]string, error) {
-	buf, err := io.ReadAll(r)
+	buf, err := readSpecialFile(r)
 	if err != nil {
 		return nil, err
 	}
@@ -828,6 +828,16 @@ func tryReadFull(r io.Reader, b []byte) (n int, err error) {
 	return n, err
 }
 
+// readSpecialFile is like io.ReadAll except it returns
+// ErrFieldTooLong if more than maxSpecialFileSize is read.
+func readSpecialFile(r io.Reader) ([]byte, error) {
+	buf, err := io.ReadAll(io.LimitReader(r, maxSpecialFileSize+1))
+	if len(buf) > maxSpecialFileSize {
+		return nil, ErrFieldTooLong
+	}
+	return buf, err
+}
+
 // discard skips n bytes in r, reporting an error if unable to do so.
 func discard(r io.Reader, n int64) error {
 	// If possible, Seek to the last byte before the end of the data section.
diff --git a/src/archive/tar/reader_test.go b/src/archive/tar/reader_test.go
index f21a6065b4..140c736429 100644
--- a/src/archive/tar/reader_test.go
+++ b/src/archive/tar/reader_test.go
@@ -6,6 +6,7 @@ package tar
 
 import (
 	"bytes"
+	"compress/bzip2"
 	"crypto/md5"
 	"errors"
 	"fmt"
@@ -244,6 +245,9 @@ func TestReader(t *testing.T) {
 		file: "testdata/pax-bad-hdr-file.tar",
 		err:  ErrHeader,
 	}, {
+		file: "testdata/pax-bad-hdr-large.tar.bz2",
+		err:  ErrFieldTooLong,
+	}, {
 		file: "testdata/pax-bad-mtime-file.tar",
 		err:  ErrHeader,
 	}, {
@@ -625,9 +629,14 @@ func TestReader(t *testing.T) {
 			}
 			defer f.Close()
 
+			var fr io.Reader = f
+			if strings.HasSuffix(v.file, ".bz2") {
+				fr = bzip2.NewReader(fr)
+			}
+
 			// Capture all headers and checksums.
 			var (
-				tr      = NewReader(f)
+				tr      = NewReader(fr)
 				hdrs    []*Header
 				chksums []string
 				rdbuf   = make([]byte, 8)
diff --git a/src/archive/tar/testdata/pax-bad-hdr-large.tar.bz2 b/src/archive/tar/testdata/pax-bad-hdr-large.tar.bz2
new file mode 100644
index 0000000000..06bf710d3a
--- /dev/null
+++ b/src/archive/tar/testdata/pax-bad-hdr-large.tar.bz2
diff --git a/src/archive/tar/writer.go b/src/archive/tar/writer.go
index 3729f7e82c..9b2e3e25d4 100644
--- a/src/archive/tar/writer.go
+++ b/src/archive/tar/writer.go
@@ -199,6 +199,9 @@ func (tw *Writer) writePAXHeader(hdr *Header, paxHdrs map[string]string) error {
 			flag = TypeXHeader
 		}
 		data := buf.String()
+		if len(data) > maxSpecialFileSize {
+			return ErrFieldTooLong
+		}
 		if err := tw.writeRawFile(name, data, flag, FormatPAX); err != nil || isGlobal {
 			return err // Global headers return here
 		}
diff --git a/src/archive/tar/writer_test.go b/src/archive/tar/writer_test.go
index da3fb89e65..640264984a 100644
--- a/src/archive/tar/writer_test.go
+++ b/src/archive/tar/writer_test.go
@@ -1004,6 +1004,33 @@ func TestIssue12594(t *testing.T) {
 	}
 }
 
+func TestWriteLongHeader(t *testing.T) {
+	for _, test := range []struct {
+		name string
+		h    *Header
+	}{{
+		name: "name too long",
+		h:    &Header{Name: strings.Repeat("a", maxSpecialFileSize)},
+	}, {
+		name: "linkname too long",
+		h:    &Header{Linkname: strings.Repeat("a", maxSpecialFileSize)},
+	}, {
+		name: "uname too long",
+		h:    &Header{Uname: strings.Repeat("a", maxSpecialFileSize)},
+	}, {
+		name: "gname too long",
+		h:    &Header{Gname: strings.Repeat("a", maxSpecialFileSize)},
+	}, {
+		name: "PAX header too long",
+		h:    &Header{PAXRecords: map[string]string{"GOLANG.x": strings.Repeat("a", maxSpecialFileSize)}},
+	}} {
+		w := NewWriter(io.Discard)
+		if err := w.WriteHeader(test.h); err != ErrFieldTooLong {
+			t.Errorf("%v: w.WriteHeader() = %v, want ErrFieldTooLong", test.name, err)
+		}
+	}
+}
+
 // testNonEmptyWriter wraps an io.Writer and ensures that
 // Write is never called with an empty buffer.
 type testNonEmptyWriter struct{ io.Writer }