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Fix decoding of uints in windows events #290

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merged 1 commit into from
Oct 7, 2022
Merged

Fix decoding of uints in windows events #290

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39 changes: 25 additions & 14 deletions attest/win_events.go
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Original file line number Diff line number Diff line change
Expand Up @@ -164,7 +164,7 @@ type WinEvents struct {
// BootCount contains the value of the monotonic boot counter. This
// value is not set for TPM 1.2 devices and some TPMs with buggy
// implementations of monotonic counters.
BootCount int
BootCount uint64
// LoadedModules contains authenticode hashes for binaries which
// were loaded during boot.
LoadedModules map[string]WinModuleLoad
Expand Down Expand Up @@ -394,38 +394,49 @@ func (w *WinEvents) readBooleanByteEvent(header microsoftEventHeader, r *bytes.R
return nil
}

func (w *WinEvents) readUint(header microsoftEventHeader, r io.Reader) (uint64, error) {
if header.Size > 8 {
return 0, fmt.Errorf("integer too large (%d bytes)", header.Size)
func (w *WinEvents) readUint32(header microsoftEventHeader, r io.Reader) (uint32, error) {
if header.Size != 4 {
return 0, fmt.Errorf("integer size not uint32 (%d bytes)", header.Size)
}

data := make([]uint8, header.Size)
if err := binary.Read(r, binary.LittleEndian, &data); err != nil {
return 0, fmt.Errorf("reading u%d: %w", header.Size<<8, err)
return 0, fmt.Errorf("reading u32: %w", err)
}
i, n := binary.Uvarint(data)
if n <= 0 {
return 0, fmt.Errorf("reading u%d: invalid varint", header.Size<<8)
i := binary.LittleEndian.Uint32(data)

return i, nil
}

func (w *WinEvents) readUint64(header microsoftEventHeader, r io.Reader) (uint64, error) {
if header.Size != 8 {
return 0, fmt.Errorf("integer size not uint64 (%d bytes)", header.Size)
}

data := make([]uint8, header.Size)
if err := binary.Read(r, binary.LittleEndian, &data); err != nil {
return 0, fmt.Errorf("reading u64: %w", err)
}
i := binary.LittleEndian.Uint64(data)

return i, nil
}

func (w *WinEvents) readBootCounter(header microsoftEventHeader, r *bytes.Reader) error {
i, err := w.readUint(header, r)
i, err := w.readUint64(header, r)
if err != nil {
return fmt.Errorf("boot counter: %v", err)
}

if w.BootCount > 0 && w.BootCount != int(i) {
if w.BootCount > 0 && w.BootCount != i {
return fmt.Errorf("conflicting values for boot counter: %d != %d", i, w.BootCount)
}
w.BootCount = int(i)
w.BootCount = i
return nil
}

func (w *WinEvents) readTransferControl(header microsoftEventHeader, r *bytes.Reader) error {
i, err := w.readUint(header, r)
i, err := w.readUint32(header, r)
if err != nil {
return fmt.Errorf("transfer control: %v", err)
}
Expand Down Expand Up @@ -473,7 +484,7 @@ func (w *WinEvents) parseImageValidated(header microsoftEventHeader, r io.Reader
}

func (w *WinEvents) parseHashAlgID(header microsoftEventHeader, r io.Reader) (WinCSPAlg, error) {
i, err := w.readUint(header, r)
i, err := w.readUint32(header, r)
if err != nil {
return 0, fmt.Errorf("hash algorithm ID: %v", err)
}
Expand Down Expand Up @@ -578,7 +589,7 @@ func (w *WinEvents) readLoadedModuleAggregation(rdr *bytes.Reader, header micros
if imgSize != 0 {
return errors.New("duplicate image size in LMA event")
}
if imgSize, err = w.readUint(h, r); err != nil {
if imgSize, err = w.readUint64(h, r); err != nil {
return err
}
case hashAlgorithmID:
Expand Down
3 changes: 3 additions & 0 deletions attest/win_events_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@ func TestParseWinEvents(t *testing.T) {
"0fdce7d71936f79445e7d2c84cbeb97c948d3730e0b839166b0a4e625c2d4547": WinModuleLoad{
FilePath: `\Windows\System32\drivers\vioscsi.sys`,
ImageBase: []uint64{81416192},
ImageSize: uint64(86016),
HashAlgorithm: WinAlgSHA256,
ImageValidated: true,
AuthorityIssuer: "Microsoft Windows Third Party Component CA 2014",
Expand All @@ -51,6 +52,7 @@ func TestParseWinEvents(t *testing.T) {
"055a36a9921b98cc04042ca95249c7eca655536868dafcec7508947ebe5e71f4": WinModuleLoad{
FilePath: `\Windows\System32\Drivers\ksecpkg.sys`,
ImageBase: []uint64{82952192},
ImageSize: uint64(204800),
HashAlgorithm: WinAlgSHA256,
ImageValidated: true,
AuthorityIssuer: "Microsoft Windows Production PCA 2011",
Expand All @@ -68,6 +70,7 @@ func TestParseWinEvents(t *testing.T) {
"2bedd1589410b6fa13c82f35db735025b6a160595922750248771f5abd0fee58": WinModuleLoad{
FilePath: `\Windows\System32\drivers\volmgrx.sys`,
ImageBase: []uint64{80875520},
ImageSize: uint64(405504),
HashAlgorithm: WinAlgSHA256,
ImageValidated: true,
AuthorityIssuer: "Microsoft Windows Production PCA 2011",
Expand Down