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package plaintext
import (
"fmt"
"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 = RegisterDecoderPlainText(r); err != nil {
return err
}
if err = r.RegisterDecodeFunc(AlgIdentifierBase64, Decode); err != nil {
return err
}
return nil
}
// RegisterDecoderPlainText registers specifically the plaintext decoder variant with the algorithm.DecoderRegister.
func RegisterDecoderPlainText(r algorithm.DecoderRegister) (err error) {
if err = r.RegisterDecodeFunc(VariantPlainText.Prefix(), DecodeVariant(VariantPlainText)); err != nil {
return err
}
return nil
}
// RegisterDecoderBase64 registers specifically the base64 decoder variant with the algorithm.DecoderRegister.
func RegisterDecoderBase64(r algorithm.DecoderRegister) (err error) {
if err = r.RegisterDecodeFunc(VariantBase64.Prefix(), DecodeVariant(VariantBase64)); 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 plaintext.Variant. If
// plaintext.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.Prefix(), v.Prefix()))
}
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, 3)
if len(parts) != 3 {
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,
}
if decoded.key, err = decoded.variant.Decode(parts[0]); err != nil {
return nil, fmt.Errorf("%w: %v", algorithm.ErrEncodedHashKeyEncoding, err)
}
if len(decoded.key) == 0 {
return nil, fmt.Errorf("%w: key has 0 bytes", algorithm.ErrEncodedHashKeyEncoding)
}
return decoded, nil
}
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