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tar: asm: store padding in chunks to avoid memory exhaustion 

Previously, we would read the entire padding in a given archive into
memory in order to store it in the packer. This would cause memory
exhaustion if a malicious archive was crafted with very large amounts of
padding. Since a given SegmentType is reconstructed losslessly, we can
simply chunk up any padding into large segments to avoid this problem.
Use a reasonable default of 1MiB to avoid changing the tar-split.json of
existing archives that are not malformed.

Fixes: CVE-2017-14992
Signed-off-by: Aleksa Sarai <asarai@suse.de>
This commit is contained in:
Aleksa Sarai 2017-11-08 00:05:46 +11:00
parent b9775006bf
commit 3d9db48dbe
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GPG Key ID: 9E18AA267DDB8DB4
1 changed files with 28 additions and 15 deletions
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43
tar/asm/disassemble.go
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@ -2,7 +2,6 @@ package asm
import (
"io"
"io/ioutil"
"github.com/vbatts/tar-split/archive/tar"
"github.com/vbatts/tar-split/tar/storage"
@ -119,20 +118,34 @@ func NewInputTarStream(r io.Reader, p storage.Packer, fp storage.FilePutter) (io
}
}
// it is allowable, and not uncommon that there is further padding on the
// end of an archive, apart from the expected 1024 null bytes.
remainder, err := ioutil.ReadAll(outputRdr)
if err != nil && err != io.EOF {
pW.CloseWithError(err)
return
}
_, err = p.AddEntry(storage.Entry{
Type: storage.SegmentType,
Payload: remainder,
})
if err != nil {
pW.CloseWithError(err)
return
// It is allowable, and not uncommon that there is further padding on
// the end of an archive, apart from the expected 1024 null bytes. We
// do this in chunks rather than in one go to avoid cases where a
// maliciously crafted tar file tries to trick us into reading many GBs
// into memory.
const paddingChunkSize = 1024 * 1024
var paddingChunk [paddingChunkSize]byte
for {
var isEOF bool
n, err := outputRdr.Read(paddingChunk[:])
if err != nil {
if err != io.EOF {
pW.CloseWithError(err)
return
}
isEOF = true
}
_, err = p.AddEntry(storage.Entry{
Type: storage.SegmentType,
Payload: paddingChunk[:n],
})
if err != nil {
pW.CloseWithError(err)
return
}
if isEOF {
break
}
}
pW.Close()
}()