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75 lines
2.1 KiB
75 lines
2.1 KiB
7 years ago
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package update
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import (
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"crypto"
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"crypto/dsa"
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"crypto/ecdsa"
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"crypto/rsa"
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"encoding/asn1"
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"errors"
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"math/big"
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)
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// Verifier defines an interface for verfiying an update's signature with a public key.
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type Verifier interface {
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VerifySignature(checksum, signature []byte, h crypto.Hash, publicKey crypto.PublicKey) error
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}
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type verifyFn func([]byte, []byte, crypto.Hash, crypto.PublicKey) error
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func (fn verifyFn) VerifySignature(checksum []byte, signature []byte, hash crypto.Hash, publicKey crypto.PublicKey) error {
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return fn(checksum, signature, hash, publicKey)
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}
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// NewRSAVerifier returns a Verifier that uses the RSA algorithm to verify updates.
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func NewRSAVerifier() Verifier {
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return verifyFn(func(checksum, signature []byte, hash crypto.Hash, publicKey crypto.PublicKey) error {
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key, ok := publicKey.(*rsa.PublicKey)
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if !ok {
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return errors.New("not a valid RSA public key")
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}
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return rsa.VerifyPKCS1v15(key, hash, checksum, signature)
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})
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}
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type rsDER struct {
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R *big.Int
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S *big.Int
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}
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// NewECDSAVerifier returns a Verifier that uses the ECDSA algorithm to verify updates.
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func NewECDSAVerifier() Verifier {
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return verifyFn(func(checksum, signature []byte, hash crypto.Hash, publicKey crypto.PublicKey) error {
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key, ok := publicKey.(*ecdsa.PublicKey)
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if !ok {
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return errors.New("not a valid ECDSA public key")
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}
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var rs rsDER
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if _, err := asn1.Unmarshal(signature, &rs); err != nil {
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return err
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}
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if !ecdsa.Verify(key, checksum, rs.R, rs.S) {
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return errors.New("failed to verify ecsda signature")
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}
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return nil
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})
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}
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// NewDSAVerifier returns a Verifier that uses the DSA algorithm to verify updates.
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func NewDSAVerifier() Verifier {
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return verifyFn(func(checksum, signature []byte, hash crypto.Hash, publicKey crypto.PublicKey) error {
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key, ok := publicKey.(*dsa.PublicKey)
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if !ok {
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return errors.New("not a valid DSA public key")
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}
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var rs rsDER
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if _, err := asn1.Unmarshal(signature, &rs); err != nil {
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return err
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}
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if !dsa.Verify(key, checksum, rs.R, rs.S) {
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return errors.New("failed to verify ecsda signature")
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}
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return nil
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})
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}
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