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ssh: reject unencrypted keys from ParsePrivateKeyWithPassphrase

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The behavior of ParsePrivateKeyWithPassphrase when the key is
unencrypted is unspecified. Currently, it just parses them like
ParsePrivateKey, which is unlikely to be what anyone wants: for us to
ignore a passphrase that they explicitly passed. It also makes the
implementation of encrypted OpenSSH keys in the next CL more confused.

Instead, make ParsePrivateKey return a PassphraseNeededError, so the
application logic can be ParsePrivateKey -> detect encrypted key ->
obtain passphrase -> ParsePrivateKeyWithPassphrase. That error will also
let us return the public key for OpenSSH keys.

Change-Id: Ife4fb2499ae538bef36e353adf9bc8e902662386
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/207599
Run-TryBot: Filippo Valsorda <filippo@golang.org>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
This commit is contained in:
Filippo Valsorda
2019-12-05 16:18:47 +00:00
committed by Filippo Valsorda
parent 86a70503ff
commit 0a08dada0f
3 changed files with 68 additions and 56 deletions
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ssh/keys.go
+29 -19
View File
@@ -1055,7 +1055,8 @@ func NewPublicKey(key interface{}) (PublicKey, error) {
}
// ParsePrivateKey returns a Signer from a PEM encoded private key. It supports
// the same keys as ParseRawPrivateKey.
// the same keys as ParseRawPrivateKey. If the private key is encrypted, it
// will return a PassphraseMissingError.
func ParsePrivateKey(pemBytes []byte) (Signer, error) {
key, err := ParseRawPrivateKey(pemBytes)
if err != nil {
@@ -1068,8 +1069,8 @@ func ParsePrivateKey(pemBytes []byte) (Signer, error) {
// ParsePrivateKeyWithPassphrase returns a Signer from a PEM encoded private
// key and passphrase. It supports the same keys as
// ParseRawPrivateKeyWithPassphrase.
func ParsePrivateKeyWithPassphrase(pemBytes, passPhrase []byte) (Signer, error) {
key, err := ParseRawPrivateKeyWithPassphrase(pemBytes, passPhrase)
func ParsePrivateKeyWithPassphrase(pemBytes, passphrase []byte) (Signer, error) {
key, err := ParseRawPrivateKeyWithPassphrase(pemBytes, passphrase)
if err != nil {
return nil, err
}
@@ -1085,8 +1086,21 @@ func encryptedBlock(block *pem.Block) bool {
return strings.Contains(block.Headers["Proc-Type"], "ENCRYPTED")
}
// A PassphraseMissingError indicates that parsing this private key requires a
// passphrase. Use ParsePrivateKeyWithPassphrase.
type PassphraseMissingError struct {
// PublicKey will be set if the private key format includes an unencrypted
// public key along with the encrypted private key.
PublicKey PublicKey
}
func (*PassphraseMissingError) Error() string {
return "ssh: this private key is passphrase protected"
}
// ParseRawPrivateKey returns a private key from a PEM encoded private key. It
// supports RSA (PKCS#1), PKCS#8, DSA (OpenSSL), and ECDSA private keys.
// supports RSA (PKCS#1), PKCS#8, DSA (OpenSSL), and ECDSA private keys. If the
// private key is encrypted, it will return a PassphraseMissingError.
func ParseRawPrivateKey(pemBytes []byte) (interface{}, error) {
block, _ := pem.Decode(pemBytes)
if block == nil {
@@ -1094,7 +1108,7 @@ func ParseRawPrivateKey(pemBytes []byte) (interface{}, error) {
}
if encryptedBlock(block) {
return nil, errors.New("ssh: cannot decode encrypted private keys")
return nil, &PassphraseMissingError{}
}
switch block.Type {
@@ -1117,24 +1131,22 @@ func ParseRawPrivateKey(pemBytes []byte) (interface{}, error) {
// ParseRawPrivateKeyWithPassphrase returns a private key decrypted with
// passphrase from a PEM encoded private key. If wrong passphrase, return
// x509.IncorrectPasswordError.
func ParseRawPrivateKeyWithPassphrase(pemBytes, passPhrase []byte) (interface{}, error) {
func ParseRawPrivateKeyWithPassphrase(pemBytes, passphrase []byte) (interface{}, error) {
block, _ := pem.Decode(pemBytes)
if block == nil {
return nil, errors.New("ssh: no key found")
}
buf := block.Bytes
if encryptedBlock(block) {
if x509.IsEncryptedPEMBlock(block) {
var err error
buf, err = x509.DecryptPEMBlock(block, passPhrase)
if err != nil {
if err == x509.IncorrectPasswordError {
return nil, err
}
return nil, fmt.Errorf("ssh: cannot decode encrypted private keys: %v", err)
}
if !encryptedBlock(block) || !x509.IsEncryptedPEMBlock(block) {
return nil, errors.New("ssh: not an encrypted key")
}
buf, err := x509.DecryptPEMBlock(block, passphrase)
if err != nil {
if err == x509.IncorrectPasswordError {
return nil, err
}
return nil, fmt.Errorf("ssh: cannot decode encrypted private keys: %v", err)
}
switch block.Type {
@@ -1144,8 +1156,6 @@ func ParseRawPrivateKeyWithPassphrase(pemBytes, passPhrase []byte) (interface{},
return x509.ParseECPrivateKey(buf)
case "DSA PRIVATE KEY":
return ParseDSAPrivateKey(buf)
case "OPENSSH PRIVATE KEY":
return parseOpenSSHPrivateKey(buf)
default:
return nil, fmt.Errorf("ssh: unsupported key type %q", block.Type)
}