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package selfupdate
import (
"crypto/ecdsa"
"crypto/sha256"
"encoding/asn1"
"fmt"
"math/big"
)
// Validator represents an interface which enables additional validation of releases.
type Validator interface {
// Validate validates release bytes against an additional asset bytes.
// See SHA2Validator or ECDSAValidator for more information.
Validate(release, asset []byte) error
// Suffix describes the additional file ending which is used for finding the
// additional asset.
Suffix() string
}
// SHA2Validator specifies a SHA256 validator for additional file validation
// before updating.
type SHA2Validator struct {
}
// Validate validates the SHA256 sum of the release against the contents of an
// additional asset file.
func (v *SHA2Validator) Validate(release, asset []byte) error {
calculatedHash := fmt.Sprintf("%x", sha256.Sum256(release))
hash := fmt.Sprintf("%s", asset[:sha256.BlockSize])
if calculatedHash != hash {
return fmt.Errorf("sha2: validation failed: hash mismatch: expected=%q, got=%q", calculatedHash, hash)
}
return nil
}
// Suffix returns the suffix for SHA2 validation.
func (v *SHA2Validator) Suffix() string {
return ".sha256"
}
// ECDSAValidator specifies a ECDSA validator for additional file validation
// before updating.
type ECDSAValidator struct {
PublicKey *ecdsa.PublicKey
}
// Validate validates the ECDSA signature the release against the signature
// contained in an additional asset file.
// additional asset file.
func (v *ECDSAValidator) Validate(input, signature []byte) error {
h := sha256.New()
h.Write(input)
var rs struct {
R *big.Int
S *big.Int
}
if _, err := asn1.Unmarshal(signature, &rs); err != nil {
return fmt.Errorf("failed to unmarshal ecdsa signature: %v", err)
}
if !ecdsa.Verify(v.PublicKey, h.Sum([]byte{}), rs.R, rs.S) {
return fmt.Errorf("ecdsa: signature verification failed")
}
return nil
}
// Suffix returns the suffix for ECDSA validation.
func (v *ECDSAValidator) Suffix() string {
return ".sig"
}
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