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Ensure critical header contains valid labels #78

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merged 3 commits into from
Jun 21, 2022
Merged

Ensure critical header contains valid labels #78

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0845404
enusre critical header contains valid labels
qmuntal Jun 20, 2022
936bb8f
format switch
qmuntal Jun 20, 2022
e0a1374
factor our label validation
qmuntal Jun 20, 2022
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63 changes: 39 additions & 24 deletions headers.go
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Original file line number Diff line number Diff line change
Expand Up @@ -158,6 +158,10 @@ func (h ProtectedHeader) ensureCritical() error {
return err
}
for _, label := range labels {
_, ok := normalizeLabel(label)
if !ok {
return fmt.Errorf("critical header label: require int / tstr type, got '%T': %v", label, label)
}
if _, ok := h[label]; !ok {
return fmt.Errorf("missing critical header: %v", label)
}
Expand Down Expand Up @@ -405,30 +409,9 @@ func ensureHeaderIV(h map[interface{}]interface{}) error {
func validateHeaderLabel(h map[interface{}]interface{}) error {
existing := make(map[interface{}]struct{})
for label := range h {
switch v := label.(type) {
case int:
label = int64(v)
case int8:
label = int64(v)
case int16:
label = int64(v)
case int32:
label = int64(v)
case int64:
label = int64(v)
case uint:
label = int64(v)
case uint8:
label = int64(v)
case uint16:
label = int64(v)
case uint32:
label = int64(v)
case uint64:
label = int64(v)
case string:
// no conversion
default:
var ok bool
label, ok = normalizeLabel(label)
if !ok {
return errors.New("cbor: header label: require int / tstr type")
}
if _, ok := existing[label]; ok {
Expand All @@ -440,6 +423,38 @@ func validateHeaderLabel(h map[interface{}]interface{}) error {
return nil
}

// normalizeLabel tries to cast label into a int64 or a string.
// Returns (nil, false) if the label type is not valid.
func normalizeLabel(label interface{}) (interface{}, bool) {
switch v := label.(type) {
case int:
label = int64(v)
case int8:
label = int64(v)
case int16:
label = int64(v)
case int32:
label = int64(v)
case int64:
label = int64(v)
case uint:
label = int64(v)
case uint8:
label = int64(v)
case uint16:
label = int64(v)
case uint32:
label = int64(v)
case uint64:
label = int64(v)
Comment on lines +448 to +449
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should we intercept the potential overflow here?

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I'll rather do it in another PR. This is clearly an issue but requires its own discussion.

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Sure. #79 for tracking this.

case string:
// no conversion
default:
return nil, false
}
return label, true
}

// headerLabelValidator is used to validate the header label of a COSE header.
type headerLabelValidator struct {
value interface{}
Expand Down
14 changes: 14 additions & 0 deletions headers_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -103,6 +103,13 @@ func TestProtectedHeader_MarshalCBOR(t *testing.T) {
},
wantErr: true,
},
{
name: "critical header contains non-label element",
h: ProtectedHeader{
HeaderLabelCritical: []interface{}{[]uint8{}},
},
wantErr: true,
},
{
name: "duplicated key",
h: ProtectedHeader{
Expand Down Expand Up @@ -238,6 +245,13 @@ func TestProtectedHeader_UnmarshalCBOR(t *testing.T) {
},
wantErr: true,
},
{
name: "critical header contains non-label element",
data: []byte{
0x44, 0xa1, 0x2, 0x81, 0x40,
},
wantErr: true,
},
{
name: "duplicated key",
data: []byte{
Expand Down