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code_generator.go
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code_generator.go
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package bertyvcissuer
import (
"crypto/hmac"
"crypto/sha256"
"fmt"
"berty.tech/berty/v2/go/pkg/errcode"
"berty.tech/weshnet/pkg/verifiablecredstypes"
)
func CodeGeneratorZero(_ *verifiablecredstypes.StateCode) (string, error) {
return "000000", nil
}
type codeGeneratorEightDigits struct {
secret []byte
}
func bytesToInt(input []byte) (uint64, error) {
bytesRequired := 4
if len(input) < bytesRequired {
return 0, errcode.ErrInvalidInput.Wrap(fmt.Errorf("expected at least %d bytes", bytesRequired))
}
out := uint64(0)
for i := uint64(0); i < uint64(bytesRequired); i++ {
out |= uint64(input[i]) << (8 * i)
}
return out % 100000000, nil
}
func (c *codeGeneratorEightDigits) CodeGeneratorEightDigits(state *verifiablecredstypes.StateCode) (string, error) {
if len(c.secret) == 0 {
return "", errcode.ErrInvalidInput.Wrap(fmt.Errorf("secret needs to be defined"))
}
if len(state.BertyLink) == 0 {
return "", errcode.ErrInvalidInput.Wrap(fmt.Errorf("invalid state: berty_link field needs to be defined"))
}
if len(state.Identifier) == 0 {
return "", errcode.ErrInvalidInput.Wrap(fmt.Errorf("invalid state: identifier field needs to be defined"))
}
if len(state.Timestamp) == 0 {
return "", errcode.ErrInvalidInput.Wrap(fmt.Errorf("invalid state: timestamp needs to be defined"))
}
h := hmac.New(sha256.New, c.secret)
_, err := h.Write([]byte(state.BertyLink))
if err != nil {
return "", errcode.ErrStreamWrite.Wrap(err)
}
_, err = h.Write([]byte(state.Identifier))
if err != nil {
return "", errcode.ErrStreamWrite.Wrap(err)
}
_, err = h.Write(state.Timestamp)
if err != nil {
return "", errcode.ErrStreamWrite.Wrap(err)
}
sum := h.Sum(nil)
codeAsInt, err := bytesToInt(sum[0:4])
if err != nil {
return "", errcode.ErrInternal.Wrap(err)
}
return fmt.Sprintf("%08d", codeAsInt), nil
}
func CodeGeneratorEightDigits(secret []byte) func(state *verifiablecredstypes.StateCode) (string, error) {
generator := &codeGeneratorEightDigits{secret: secret}
return generator.CodeGeneratorEightDigits
}