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https://issues.apache.org/jira/browse/SSHD-997?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17112365#comment-17112365
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Thomas Wolf edited comment on SSHD-997 at 5/20/20, 3:44 PM:
------------------------------------------------------------
I think I know why it is all zeroes for a key read from a file.
Check {{OpenSSHEd25519PrivateKeyEntryDecoder}}, lines 103ff:
{code:java}
byte[] sk = Arrays.copyOf(keypair, SK_SIZE);
EdDSAPrivateKey privateKey;
try {
// create the private key
EdDSAParameterSpec params =
EdDSANamedCurveTable.getByName(EdDSASecurityProviderUtils.CURVE_ED25519_SHA512);
privateKey = generatePrivateKey(new EdDSAPrivateKeySpec(sk,
params));
} finally {
// get rid of sensitive data a.s.a.p
Arrays.fill(sk, (byte) 0);
}
{code}
sshd clears the SK read from the file. But that SK is the same object as
{{privateKey.seed}}; it is _not_ copied during generatePrivateKey.
The key still works with sshd (I use ed25519 keys with sshd in JGit daily), but
this breaks round-tripping: reading a key from a file and writing it again
will produce a different file. (And of course it also breaks
{{KeyUtils.compareKeys()}}.)
The fix in sshd is to remove the {{try-finally}} and the {{Arrays.fill(sk,
(byte) 0);}}. A fix in i2p would be to make sure that the private key generated
from a spec does not reference any arrays passed in externally, but to copy the
data such that the key is the sole owner.
So this is actually not a "minor feature" but really a "bug".
was (Author: wolft):
I think I know why it is all zeroes for a key read from a file.
Check {{OpenSSHEd25519PrivateKeyEntryDecoder}}, lines 103ff:
{code:java}
byte[] sk = Arrays.copyOf(keypair, SK_SIZE);
EdDSAPrivateKey privateKey;
try {
// create the private key
EdDSAParameterSpec params =
EdDSANamedCurveTable.getByName(EdDSASecurityProviderUtils.CURVE_ED25519_SHA512);
privateKey = generatePrivateKey(new EdDSAPrivateKeySpec(sk,
params));
} finally {
// get rid of sensitive data a.s.a.p
Arrays.fill(sk, (byte) 0);
}
{code}
sshd clears the SK read from the file. But that SK is the same object as
{{privateKey.seed}}; it is _not_ copied during generatePrivateKey.
The key still works with sshd (I use ed25519 keys with sshd in JGit daily), but
this breaks round-tripping: reading a key from a file and writing it again
will produce a different file. (And of course it also breaks
{{KeyUtils.compareKeys()}}.)
The fix in sshd is to remove the {{try-finally}} and the {{Arrays.fill(sk,
(byte) 0);}}. A fix in i2p would be to make sure that the private key generated
from a spec does not reference any arrays passed in externally, but to copy the
data such that the key is the sole owner.
So this is actually not a "minor feature" but actually a "bug".
> Replace EdDSA-Java library with new ed25519-elisabeth implementation
> --------------------------------------------------------------------
>
> Key: SSHD-997
> URL: https://issues.apache.org/jira/browse/SSHD-997
> Project: MINA SSHD
> Issue Type: New Feature
> Affects Versions: 2.4.0
> Reporter: David Ostrovsky
> Priority: Minor
>
> Recent addition to the SSHD library revealed issues with seed attribute in
> EdDSA-Java library:
> {code:java}
> + private boolean compare(KeyPair a, KeyPair b) {
> + if ("EDDSA".equals(data.algorithm)) {
> + // Bug in net.i2p.crypto.eddsa and in sshd? Both also compare the
> + // seed of the private key, but for a generated key, this is some
> + // random value, while it is all zeroes for a key read from a
> file.
> + return KeyUtils.compareKeys(a.getPublic(), b.getPublic())
> + && Objects.equals(((EdDSAKey)
> a.getPrivate()).getParams(),
> + ((EdDSAKey) b.getPrivate()).getParams());
> + }
> {code}
> The corresponding issue: [1] upstream pointing to the new library:
> [1] https://github.com/str4d/ed25519-java/issues/30#issuecomment-573389252
> [2] https://github.com/cryptography-cafe/ed25519-elisabeth
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