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tpmutil: Fix integer casting on 32-bit platforms #253

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merged 1 commit into from
Jun 29, 2021
Merged

tpmutil: Fix integer casting on 32-bit platforms #253

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19 changes: 10 additions & 9 deletions tpmutil/structures.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ import (
// from resulting in a massive memory allocation, potentially causing
// an OOM condition on the system.
// We expect no buffer from a TPM to approach 1Mb in size.
const maxBytesBufferSize = 1024 * 1024 // 1Mb.
const maxBytesBufferSize uint32 = 1024 * 1024 // 1Mb.

// RawBytes is for Pack and RunCommand arguments that are already encoded.
// Compared to []byte, RawBytes will not be prepended with slice length during
Expand All @@ -38,16 +38,16 @@ type U16Bytes []byte

// TPMMarshal packs U16Bytes
func (b *U16Bytes) TPMMarshal(out io.Writer) error {
size := uint16(len([]byte(*b)))
if err := binary.Write(out, binary.BigEndian, size); err != nil {
size := len([]byte(*b))
if err := binary.Write(out, binary.BigEndian, uint16(size)); err != nil {
return err
}

n, err := out.Write(*b)
if err != nil {
return err
}
if n != int(size) {
if n != size {
return fmt.Errorf("unable to write all contents of U16Bytes")
}
return nil
Expand Down Expand Up @@ -82,16 +82,16 @@ type U32Bytes []byte

// TPMMarshal packs U32Bytes
func (b *U32Bytes) TPMMarshal(out io.Writer) error {
size := uint32(len([]byte(*b)))
if err := binary.Write(out, binary.BigEndian, size); err != nil {
size := len([]byte(*b))
if err := binary.Write(out, binary.BigEndian, uint32(size)); err != nil {
return err
}

n, err := out.Write(*b)
if err != nil {
return err
}
if n != int(size) {
if n != size {
return fmt.Errorf("unable to write all contents of U32Bytes")
}
return nil
Expand All @@ -103,11 +103,12 @@ func (b *U32Bytes) TPMUnmarshal(in io.Reader) error {
if err := binary.Read(in, binary.BigEndian, &tmpSize); err != nil {
return err
}
size := int(tmpSize)

if size > maxBytesBufferSize {
if tmpSize > maxBytesBufferSize {
return bytes.ErrTooLarge
}
// We can now safely cast to an int on 32-bit or 64-bit machines
size := int(tmpSize)

if len(*b) >= size {
*b = (*b)[:size]
Expand Down