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only process supported Putty v3 keys + minor optimizations (#729)
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@jpstotz
jpstotz committed Oct 2, 2021
1 parent 93de1ec commit d6d6f0d
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Showing 2 changed files with 92 additions and 13 deletions.
37 changes: 26 additions & 11 deletions src/main/java/net/schmizz/sshj/userauth/keyprovider/PuTTYKeyFile.java
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Original file line number Diff line number Diff line change
Expand Up @@ -100,9 +100,16 @@ public KeyType getType() throws IOException {
return KeyType.UNKNOWN;
}

public boolean isEncrypted() {
// Currently the only supported encryption types are "aes256-cbc" and "none".
return "aes256-cbc".equals(headers.get("Encryption"));
public boolean isEncrypted() throws IOException {
// Currently, the only supported encryption types are "aes256-cbc" and "none".
String encryption = headers.get("Encryption");
if ("none".equals(encryption)) {
return false;
}
if ("aes256-cbc".equals(encryption)) {
return true;
}
throw new IOException(String.format("Unsupported encryption: %s", encryption));
}

private Map<String, String> payload = new HashMap<String, String>();
Expand All @@ -116,8 +123,9 @@ protected KeyPair readKeyPair() throws IOException {
this.parseKeyPair();
final Buffer.PlainBuffer publicKeyReader = new Buffer.PlainBuffer(publicKey);
final Buffer.PlainBuffer privateKeyReader = new Buffer.PlainBuffer(privateKey);
final KeyType keyType = this.getType();
publicKeyReader.readBytes(); // The first part of the payload is a human-readable key format name.
if (KeyType.RSA.equals(this.getType())) {
if (KeyType.RSA.equals(keyType)) {
// public key exponent
BigInteger e = publicKeyReader.readMPInt();
// modulus
Expand All @@ -139,7 +147,7 @@ protected KeyPair readKeyPair() throws IOException {
throw new IOException(i.getMessage(), i);
}
}
if (KeyType.DSA.equals(this.getType())) {
if (KeyType.DSA.equals(keyType)) {
BigInteger p = publicKeyReader.readMPInt();
BigInteger q = publicKeyReader.readMPInt();
BigInteger g = publicKeyReader.readMPInt();
Expand All @@ -161,14 +169,14 @@ protected KeyPair readKeyPair() throws IOException {
throw new IOException(e.getMessage(), e);
}
}
if (KeyType.ED25519.equals(this.getType())) {
if (KeyType.ED25519.equals(keyType)) {
EdDSANamedCurveSpec ed25519 = EdDSANamedCurveTable.getByName("Ed25519");
EdDSAPublicKeySpec publicSpec = new EdDSAPublicKeySpec(publicKeyReader.readBytes(), ed25519);
EdDSAPrivateKeySpec privateSpec = new EdDSAPrivateKeySpec(privateKeyReader.readBytes(), ed25519);
return new KeyPair(new EdDSAPublicKey(publicSpec), new EdDSAPrivateKey(privateSpec));
}
final String ecdsaCurve;
switch (this.getType()) {
switch (keyType) {
case ECDSA256:
ecdsaCurve = "P-256";
break;
Expand All @@ -190,7 +198,7 @@ protected KeyPair readKeyPair() throws IOException {
ECPrivateKeySpec pks = new ECPrivateKeySpec(s, ecCurveSpec);
try {
PrivateKey privateKey = SecurityUtils.getKeyFactory(KeyAlgorithm.ECDSA).generatePrivate(pks);
return new KeyPair(getType().readPubKeyFromBuffer(publicKeyReader), privateKey);
return new KeyPair(keyType.readPubKeyFromBuffer(publicKeyReader), privateKey);
} catch (GeneralSecurityException e) {
throw new IOException(e.getMessage(), e);
}
Expand Down Expand Up @@ -252,6 +260,12 @@ protected void parseKeyPair() throws IOException {
* This is used to decrypt the private key when it's encrypted.
*/
private byte[] toKey(final String passphrase) throws IOException {
// The field Key-Derivation has been introduced with Putty v3 key file format
// The only available formats are "Argon2i" "Argon2d" and "Argon2id"
String keyDerivation = headers.get("Key-Derivation");
if (keyDerivation != null) {
throw new IOException(String.format("Unsupported key derivation function: %s", keyDerivation));
}
try {
MessageDigest digest = MessageDigest.getInstance("SHA-1");

Expand Down Expand Up @@ -283,7 +297,7 @@ private byte[] toKey(final String passphrase) throws IOException {
*/
private void verify(final String passphrase) throws IOException {
try {
// The key to the MAC is itself a SHA-1 hash of:
// The key to the MAC is itself a SHA-1 hash of (v1/v2 key only):
MessageDigest digest = MessageDigest.getInstance("SHA-1");
digest.update("putty-private-key-file-mac-key".getBytes());
if (passphrase != null) {
Expand All @@ -297,8 +311,9 @@ private void verify(final String passphrase) throws IOException {
final ByteArrayOutputStream out = new ByteArrayOutputStream();
final DataOutputStream data = new DataOutputStream(out);
// name of algorithm
data.writeInt(this.getType().toString().length());
data.writeBytes(this.getType().toString());
String keyType = this.getType().toString();
data.writeInt(keyType.length());
data.writeBytes(keyType);

data.writeInt(headers.get("Encryption").length());
data.writeBytes(headers.get("Encryption"));
Expand Down
68 changes: 66 additions & 2 deletions src/test/java/net/schmizz/sshj/keyprovider/PuTTYKeyFileTest.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -25,10 +25,13 @@
import java.io.File;
import java.io.IOException;
import java.io.StringReader;
import java.security.PrivateKey;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;

public class PuTTYKeyFileTest {

Expand Down Expand Up @@ -236,7 +239,39 @@ public class PuTTYKeyFileTest {
"Private-Lines: 1\n" +
"AAAAIEblmwyKaGuvc6dLgNeHsc1BuZeQORTSxBF5SBLNyjYc\n" +
"Private-MAC: e1aed15a209f48fdaa5228640f1109a7740340764a96f97ec6023da7f92d07ea";


final static String v3_rsa_encrypted = "PuTTY-User-Key-File-3: ssh-rsa\n" +
"Encryption: aes256-cbc\n" +
"Comment: rsa-key-20210926\n" +
"Public-Lines: 6\n" +
"AAAAB3NzaC1yc2EAAAADAQABAAABAQCBjWQHMpKAQnU3vZZF/iHn4RA867Ox+U03\n" +
"/GOHivW0SgGIQbhKcSSWvTzYOE+GQdtX9T2KJxr76z/lB4nghkcWkpLoQW91gNBf\n" +
"PUagMvaBxKXC8cNqaMm99uw5KpRg8SpTJWxwYPlQtzmyxav0PRFeOMSsiRsnjNuX\n" +
"polMDSu6vmkkuKrPzvinPZbsXoZeMybcm1gn2Zq+7ik4us0icaGxRJRuF+nVqYag\n" +
"EmO9jmQoytyqoNWzvPYEh/dh85hESwtIKXiaMOjQg52dW5BuELPGV7ZxaKRK7Znw\n" +
"RGW6CtoGYulo0mJz5IZslDrRK/EK2bSGDbrlAcYaajROB6aBDyaJ\n" +
"Key-Derivation: Argon2id\n" +
"Argon2-Memory: 8192\n" +
"Argon2-Passes: 21\n" +
"Argon2-Parallelism: 1\n" +
"Argon2-Salt: baf1530601433715467614d044c0e4a5\n" +
"Private-Lines: 14\n" +
"QAJl3mq/QJc8/of4xWbgBuE09GdgIuVhRYGAV5yC5C0dpuiJ+yF/6h7mk36s5E3Q\n" +
"k32l+ZoWHG/kBc8s6N9rTQnIgC/eieNlN5FK3OSSoI9PBvoAtNEVWsR2T4U6ZkAG\n" +
"FbyF3vRWq2h9Ux8flZusySqafQ2AhXP79pr13wvMziv1QbPkPFHWaR1Uvq9w0GJq\n" +
"rfR+M6t8/6aPKhnsCTy8MiAoIcjeZmHiG/vOMIBBoWI7KtpD5IrbO4pIgzRK8m9Z\n" +
"JqQvgWCPnddwCeiDFOZwf/Bm6g+duQYId4upB1IxSs34j21a7ZkMSExDZyV0d13S\n" +
"G59U9pReZ7mHyIjORqeY7ssr/L9aJPPa7YCu4J5a/Bn/ARf/X5XmMnueFZ6H806M\n" +
"ZUtHzeG2sZGoHULpwEaY1zRQs1JD5UAeaFzgDpzD4oeaD8v+FS3RdNlgj2gtWNcl\n" +
"h8nvWD60XbylR0BdbB553xGuC8HC0482xQCCJUc8SMHZ/k2+FKTaf2m2p4dLyKkk\n" +
"Qrw43QcmkgypUPRHKvnVs+6qUYMDHkwtPR1ZGFqHQzlHozvO9NdY/ZXTln/qfPZA\n" +
"5w5TKvy0/GvofhISJCMocnPbkqGR6fDcKbpUjAS/RDgsCKKS5hxf6nhsYUgrXA4G\n" +
"hXIgqGnMefLemjRG7dD/3XE8NmF6Q8mjIideEOBeP4tRCaDC2n90rZ3yChP9bsel\n" +
"yg/TeKxj7OLk+X3ocP3yw2lsp3zOPsptSNtGI7g9VaIPGtxGaqRaIuObdLbBxCeR\n" +
"ZgKSIuWtz8W1kT0aWuZ0aXMPagGao0ZsffmroyVpGbzW3QaI9633Krmf7EyphZoy\n" +
"6tV3Z/GJ5aQJFeMYPOq69ktXRLAWr800822NwEStcxtQHTWbaTk7dxh8+0xwlCgI\n" +
"Private-MAC: 582dea09758afd93a8e248abce358287d384e5ee36d21515ffcc0d42d8c5d86a\n";

@Test
public void test2048() throws Exception {
PuTTYKeyFile key = new PuTTYKeyFile();
Expand Down Expand Up @@ -359,7 +394,36 @@ public void testV3Key() throws Exception {
assertNotNull(key.getPrivate());
assertNotNull(key.getPublic());
}


/**
* Reading an encrypted Putty v3 key requires an Argon2i/Argon2d/Argon2id
* implementation.
* Putty v3 keys additionally use a different algorithm for generating the "Private-MAC"
*/
@Test
public void testRSAv3EncryptedKey() throws Exception {
PuTTYKeyFile key = new PuTTYKeyFile();
key.init(new StringReader(v3_rsa_encrypted), new PasswordFinder() {
@Override
public char[] reqPassword(Resource<?> resource) {
return "changeit".toCharArray();
}

@Override
public boolean shouldRetry(Resource<?> resource) {
return false;
}
});
try {
PrivateKey privateKey = key.getPrivate();
fail("IOException expected as encrypted Putty v3 keys are not yet supported");
} catch (IOException e) {
assertTrue(e.getMessage().startsWith("Unsupported key derivation function"));
}
// assertNotNull(key.getPrivate());
// assertNotNull(key.getPublic());
}

@Test
public void testCorrectPassphraseRsa() throws Exception {
PuTTYKeyFile key = new PuTTYKeyFile();
Expand Down

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