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Add extra logging to troubleshoot issue #670

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This commit is contained in:
Jeroen van Erp
2021-03-30 12:00:34 +02:00
parent 45b2f32b14
commit cf7309c866
1 changed files with 30 additions and 3 deletions
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33
src/main/java/net/schmizz/sshj/transport/Encoder.java
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@@ -16,6 +16,7 @@
package net.schmizz.sshj.transport;
import net.schmizz.sshj.common.Buffer;
import net.schmizz.sshj.common.ByteArrayUtils;
import net.schmizz.sshj.common.LoggerFactory;
import net.schmizz.sshj.common.SSHPacket;
import net.schmizz.sshj.transport.cipher.Cipher;
@@ -83,18 +84,38 @@ final class Encoder
}
// Compute padding length
int padLen = cipherSize - (lengthWithoutPadding % cipherSize);
if (padLen < 4 || (authMode && padLen < cipherSize)) {
padLen += cipherSize;
// random padding - Arbitrary-length padding, such that the total length of
// (packet_length || padding_length || payload || random padding)
// is a multiple of the cipher block size or 8, whichever is
// larger. There MUST be at least four bytes of padding. The
// padding SHOULD consist of random bytes. The maximum amount of
// padding is 255 bytes.
int mod = 8;
if (cipherSize > mod) {
mod = cipherSize;
}
int padLen = mod - (lengthWithoutPadding % mod);
if (padLen < 4 || (authMode && padLen < mod)) {
padLen += mod;
}
final int startOfPacket = buffer.rpos() - 5;
int packetLen = 1 + payloadSize + padLen; // packetLength = padLen (1 byte) + payload + padding
// The minimum size of a packet is 16 (or the cipher block size,
// whichever is larger) bytes (plus 'mac'). Implementations SHOULD
// decrypt the length after receiving the first 8 (or cipher block size,
// whichever is larger) bytes of a packet.
if (packetLen < 16) {
padLen += cipherSize;
packetLen = 1 + payloadSize + padLen;
}
// while (packetLen < Math.max(16, cipherSize)) {
// padLen += mod; // Increment with the mod so that multiple holds
// packetLen = 1 + payloadSize + padLen;
// }
/*
* In AES-GCM ciphers, they require packets must be a multiple of 16 bytes (which is also block size of AES)
* as mentioned in RFC5647 Section 7.2. So we are calculating the extra padding as necessary here
@@ -130,10 +151,16 @@ final class Encoder
if (mac != null) {
putMAC(buffer, startOfPacket, endOfPadding);
}
if (log.isTraceEnabled()) {
log.trace("Encrypting packet #{}: {}", seq, ByteArrayUtils.printHex(buffer.array(), startOfPacket, 4 + packetLen));
}
cipher.update(buffer.array(), startOfPacket, 4 + packetLen);
}
buffer.rpos(startOfPacket); // Make ready-to-read
return seq;
} finally {
encodeLock.unlock();