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package googletpm
import (
"encoding/binary"
"errors"
"fmt"
"io"
"reflect"
)
// From github.com/google/go-tpm
// Portions of existing package conflicted with existing build environment
// and only needed very small amount of code for pubarea and certinfo structs
// so copied them out to this package
// Supported Algorithms.
const (
AlgUnknown Algorithm = 0x0000
AlgRSA Algorithm = 0x0001
AlgSHA1 Algorithm = 0x0004
AlgAES Algorithm = 0x0006
AlgKeyedHash Algorithm = 0x0008
AlgSHA256 Algorithm = 0x000B
AlgSHA384 Algorithm = 0x000C
AlgSHA512 Algorithm = 0x000D
AlgNull Algorithm = 0x0010
AlgRSASSA Algorithm = 0x0014
AlgRSAES Algorithm = 0x0015
AlgRSAPSS Algorithm = 0x0016
AlgOAEP Algorithm = 0x0017
AlgECDSA Algorithm = 0x0018
AlgECDH Algorithm = 0x0019
AlgECDAA Algorithm = 0x001A
AlgKDF2 Algorithm = 0x0021
AlgECC Algorithm = 0x0023
AlgCTR Algorithm = 0x0040
AlgOFB Algorithm = 0x0041
AlgCBC Algorithm = 0x0042
AlgCFB Algorithm = 0x0043
AlgECB Algorithm = 0x0044
)
// UnpackBuf recursively unpacks types from a reader just as encoding/binary
// does under binary.BigEndian, but with one difference: it unpacks a byte
// slice by first reading an integer with lengthPrefixSize bytes, then reading
// that many bytes. It assumes that incoming values are pointers to values so
// that, e.g., underlying slices can be resized as needed.
func UnpackBuf(buf io.Reader, elts ...interface{}) error {
for _, e := range elts {
v := reflect.ValueOf(e)
k := v.Kind()
if k != reflect.Ptr {
return fmt.Errorf("all values passed to Unpack must be pointers, got %v", k)
}
if v.IsNil() {
return errors.New("can't fill a nil pointer")
}
iv := reflect.Indirect(v)
switch iv.Kind() {
case reflect.Struct:
// Decompose the struct and copy over the values.
for i := 0; i < iv.NumField(); i++ {
if err := UnpackBuf(buf, iv.Field(i).Addr().Interface()); err != nil {
return err
}
}
case reflect.Slice:
var size int
_, isHandles := e.(*[]Handle)
switch {
// []Handle always uses 2-byte length, even with TPM 1.2.
case isHandles:
var tmpSize uint16
if err := binary.Read(buf, binary.BigEndian, &tmpSize); err != nil {
return err
}
size = int(tmpSize)
// TPM 2.0
case lengthPrefixSize == tpm20PrefixSize:
var tmpSize uint16
if err := binary.Read(buf, binary.BigEndian, &tmpSize); err != nil {
return err
}
size = int(tmpSize)
// TPM 1.2
case lengthPrefixSize == tpm12PrefixSize:
var tmpSize uint32
if err := binary.Read(buf, binary.BigEndian, &tmpSize); err != nil {
return err
}
size = int(tmpSize)
default:
return fmt.Errorf("lengthPrefixSize is %d, must be either 2 or 4", lengthPrefixSize)
}
// A zero size is used by the TPM to signal that certain elements
// are not present.
if size == 0 {
continue
}
// Make len(e) match size exactly.
switch b := e.(type) {
case *[]byte:
if len(*b) >= size {
*b = (*b)[:size]
} else {
*b = append(*b, make([]byte, size-len(*b))...)
}
case *[]Handle:
if len(*b) >= size {
*b = (*b)[:size]
} else {
*b = append(*b, make([]Handle, size-len(*b))...)
}
default:
return fmt.Errorf("can't fill pointer to %T, only []byte or []Handle slices", e)
}
if err := binary.Read(buf, binary.BigEndian, e); err != nil {
return err
}
default:
if err := binary.Read(buf, binary.BigEndian, e); err != nil {
return err
}
}
}
return nil
}
// lengthPrefixSize is the size in bytes of length prefix for byte slices.
//
// In TPM 1.2 this is 4 bytes.
// In TPM 2.0 this is 2 bytes.
var lengthPrefixSize int
const (
tpm12PrefixSize = 4
tpm20PrefixSize = 2
)
// UseTPM20LengthPrefixSize makes Pack/Unpack use TPM 2.0 encoding for byte
// arrays.
func UseTPM20LengthPrefixSize() {
lengthPrefixSize = tpm20PrefixSize
}
|
