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fix(gcm): reset AEAD packet/nonce counters during key exchanges (#165) #14

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Merged
GT-610 merged 1 commit into from
Jun 30, 2026
Merged

fix(gcm): reset AEAD packet/nonce counters during key exchanges (#165) #14

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10 changes: 8 additions & 2 deletions lib/src/ssh_transport.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -210,6 +210,10 @@ class SSHTransport {

final _remotePacketSN = SSHPacketSN.fromZero();

int _localAeadPacketCount = 0;

int _remoteAeadPacketCount = 0;

final _paddingRandom = Random.secure();

/// Whether a key exchange is currently in progress (initial or re-key).
Expand Down Expand Up @@ -372,7 +376,7 @@ class SSHTransport {
final encrypted = _processAead(
key: _localCipherKey!,
iv: _localIV!,
sequence: _localPacketSN.value,
sequence: _localAeadPacketCount++,
aad: aad,
input: plaintext,
forEncryption: true,
Expand Down Expand Up @@ -743,7 +747,7 @@ class SSHTransport {
plaintext = _processAead(
key: _remoteAeadKey!,
iv: _remoteAeadFixedNonce!,
sequence: _remotePacketSN.value,
sequence: _remoteAeadPacketCount++,
aad: aad,
input: encryptedInput,
forEncryption: false,
Expand Down Expand Up @@ -1035,6 +1039,7 @@ class SSHTransport {
}
_encryptCipher = null;
_localMac = null; // AEAD provides integrity
_localAeadPacketCount = 0;
} else {
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_encryptCipher = cipherType.createCipher(
_deriveKey(
Expand Down Expand Up @@ -1104,6 +1109,7 @@ class SSHTransport {
}
_decryptCipher = null;
_remoteMac = null; // AEAD provides integrity
_remoteAeadPacketCount = 0;
} else {
_decryptCipher = cipherType.createCipher(
_deriveKey(
Expand Down