fix: wipe private key bytes and passphrases when they're freed - #542
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irvingouj@Devolutions (irvingoujAtDevolution)
added this pull request to stack #540
September 30, 2026 03:01
Disposing a key object from .NET now zeroes what it held instead of just freeing it. - Pem: the decoded bytes, since a PEM can carry a private key - SshPrivateKey: the passphrase (picky already wipes the key itself) - SshPrivateKey/PuttyPpk ToRepr: the temporary string holding the encoded key - Ppk: the private key buffer and the copies made while encrypting, decrypting and converting. make_padding now allocates its final size up front so a resize can't leave a plaintext copy behind. Adds .NET round-trip tests for passphrase-protected SSH keys and encrypted PPKs, which had no coverage before. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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On top of #541. Disposing a key from .NET now zeroes what it held instead of just freeing it.
Pem: the decoded bytes, since a PEM can carry a private keySshPrivateKey: the passphrase. picky already wipes the key itselfSshPrivateKey.ToRepr/PuttyPpk.ToRepr: the temporary string holding the encoded keyPpk(picky core): the private key buffer isZeroizingnow, so the copies made while encrypting, decrypting and converting get wiped too.make_paddingallocates its final size up front so a resize can't leave a plaintext copy behind. Field is private, no API changeWhat this doesn't cover (it's all outside picky):
ToReprstring, and thebyte[]C# builds for astringargument (Diplomat.Utf8.Clone). That's the generator, so it's a follow-up in Devolutions/diplomatstringyou get back fromToRepror pass in as a passphrase. It's immutable, nothing to wipeNew tests: passphrase-protected SSH key and encrypted PPK round trips. Neither had .NET coverage before.
Tested: 34/34 on net6 and 17/17 on net48, debug and release native. picky putty/ssh/pem 95/95.