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|
package shacrypt
import (
"fmt"
"strconv"
"github.com/go-crypt/crypt/algorithm"
"github.com/go-crypt/crypt/internal/encoding"
)
// RegisterDecoder the decoder with the algorithm.DecoderRegister.
func RegisterDecoder(r algorithm.DecoderRegister) (err error) {
if err = RegisterDecoderSHA256(r); err != nil {
return err
}
if err = RegisterDecoderSHA512(r); err != nil {
return err
}
return nil
}
// RegisterDecoderSHA256 registers specifically the sha256 decoder variant with the algorithm.DecoderRegister.
func RegisterDecoderSHA256(r algorithm.DecoderRegister) (err error) {
if err = r.RegisterDecodeFunc(VariantSHA256.Prefix(), DecodeVariant(VariantSHA256)); err != nil {
return err
}
return nil
}
// RegisterDecoderSHA512 registers specifically the sha512 decoder variant with the algorithm.DecoderRegister.
func RegisterDecoderSHA512(r algorithm.DecoderRegister) (err error) {
if err = r.RegisterDecodeFunc(VariantSHA512.Prefix(), DecodeVariant(VariantSHA512)); err != nil {
return err
}
return nil
}
// Decode the encoded digest into a algorithm.Digest.
func Decode(encodedDigest string) (digest algorithm.Digest, err error) {
return DecodeVariant(VariantNone)(encodedDigest)
}
// DecodeVariant the encoded digest into a algorithm.Digest provided it matches the provided Variant. If VariantNone is
// used all variants can be decoded.
func DecodeVariant(v Variant) func(encodedDigest string) (digest algorithm.Digest, err error) {
return func(encodedDigest string) (digest algorithm.Digest, err error) {
var (
parts []string
variant Variant
)
if variant, parts, err = decoderParts(encodedDigest); err != nil {
return nil, fmt.Errorf(algorithm.ErrFmtDigestDecode, AlgName, err)
}
if v != VariantNone && v != variant {
return nil, fmt.Errorf(algorithm.ErrFmtDigestDecode, AlgName, fmt.Errorf("the '%s' variant cannot be decoded only the '%s' variant can be", variant.String(), v.String()))
}
if digest, err = decode(variant, parts); err != nil {
return nil, fmt.Errorf(algorithm.ErrFmtDigestDecode, AlgName, err)
}
return digest, nil
}
}
func decoderParts(encodedDigest string) (variant Variant, parts []string, err error) {
parts = encoding.Split(encodedDigest, -1)
if n := len(parts); n != 4 && n != 5 {
return VariantNone, nil, algorithm.ErrEncodedHashInvalidFormat
}
variant = NewVariant(parts[1])
if variant == VariantNone {
return variant, nil, fmt.Errorf("%w: identifier '%s' is not an encoded %s digest", algorithm.ErrEncodedHashInvalidIdentifier, parts[1], AlgName)
}
return variant, parts[2:], nil
}
func decode(variant Variant, parts []string) (digest algorithm.Digest, err error) {
decoded := &Digest{
variant: variant,
}
var (
ip, is, ik int
)
switch len(parts) {
case 2:
ip, is, ik = -1, 0, 1
case 3:
ip, is, ik = 0, 1, 2
}
if len(parts[ik]) == 0 {
return nil, fmt.Errorf("%w: key has 0 bytes", algorithm.ErrEncodedHashKeyEncoding)
}
decoded.iterations = IterationsDefaultOmitted
var params []encoding.Parameter
if ip >= 0 {
if params, err = encoding.DecodeParameterStr(parts[ip]); err != nil {
return nil, err
}
}
for _, param := range params {
switch param.Key {
case "rounds":
var rounds uint64
if rounds, err = strconv.ParseUint(param.Value, 10, 32); err != nil {
return nil, fmt.Errorf("%w: option '%s' has invalid value '%s': %v", algorithm.ErrEncodedHashInvalidOptionValue, param.Key, param.Value, err)
}
decoded.iterations = int(rounds)
default:
return nil, fmt.Errorf("%w: option '%s' with value '%s' is unknown", algorithm.ErrEncodedHashInvalidOptionKey, param.Key, param.Value)
}
}
decoded.salt, decoded.key = []byte(parts[is]), []byte(parts[ik])
return decoded, nil
}
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