From 96bb08dd94b67b34cb37dfa79f680956ec647b2e Mon Sep 17 00:00:00 2001
From: Warren <warren@momentry.ddns.net>
Date: Wed, 10 Jun 2026 15:43:31 +0800
Subject: [PATCH] =?UTF-8?q?SSH=20Padding=E8=AE=A1=E7=AE=97=E4=BF=AE?=
 =?UTF-8?q?=E5=A4=8D=EF=BC=9A=E7=AC=A6=E5=90=88RFC=204253=E8=A7=84?=
 =?UTF-8?q?=E8=8C=83=20=E2=9C=85?=
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修复内容：
- Padding计算逻辑完全符合SSH协议规范
- (packet_length + 4) % block_size == 0
- 最少4字节padding，动态调整满足block_size约束

测试结果：
✅ SSH服务器编译成功（0错误）
✅ SSH服务器启动成功（port 2024）
✅ SSH版本交换成功（SSH-2.0-MarkBaseSSH_1.0）
✅ SSH_MSG_KEXINIT发送和接收成功 ⭐⭐⭐⭐⭐
✅ OpenSSH客户端成功解析算法提议

OpenSSH客户端输出：
  debug1: SSH2_MSG_KEXINIT sent
  debug1: SSH2_MSG_KEXINIT received
  debug2: peer server KEXINIT proposal
  debug2: KEX algorithms: curve25519-sha256...

下一步：
- 测试SSH密钥交换（Curve25519）
- 测试认证流程
- 测试SFTP/SCP功能
---
 markbase-core/src/ssh_server/packet.rs | 37 ++++++++++++++++++--------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/markbase-core/src/ssh_server/packet.rs b/markbase-core/src/ssh_server/packet.rs
index fed9bb2..e12f788 100644
--- a/markbase-core/src/ssh_server/packet.rs
+++ b/markbase-core/src/ssh_server/packet.rs
@@ -67,27 +67,42 @@ pub struct SshPacket {
 impl SshPacket {
     /// 创建新的SSH packet
     pub fn new(payload: Vec<u8>) -> Self {
-        // 计算padding（SSH协议要求：packet总长度必须是block_size的倍数）
-        // 参考OpenSSH：block_size = 8（未加密阶段）
-        let block_size = 8;
+        // 计算padding（SSH协议RFC 4253规范）
+        // 参考OpenSSH packet.c: construct_packet()
+        let block_size = 8;  // 未加密阶段block_size=8
         
-        // packet_length = padding_length + payload_length + 1 (type byte)
         let payload_length = payload.len();
         let min_padding = 4;  // OpenSSH要求最少4字节padding
         
-        // 计算padding长度
-        let total_without_mac = 1 + payload_length;  // padding_length byte + payload
-        let padding_needed = (block_size - (total_without_mac % block_size)) % block_size;
-        let padding_length = std::cmp::max(min_padding as u32, padding_needed as u32) as u8;
+        // SSH协议约束：
+        // packet_length = padding_length + payload_length + 1
+        // (packet_length + 4) 必须是block_size的倍数
+        // 
+        // 计算：
+        // (1 + payload_length + padding_length + 4) % 8 == 0
+        // => (5 + payload_length + padding_length) % 8 == 0
         
-        // 计算packet总长度
+        // 先尝试padding=4（最小）
+        let mut padding_length = min_padding as u8;
+        
+        // 计算packet总长度（包括4字节的packet_length字段）
         let packet_length = 1 + payload_length + padding_length as usize;
+        let total_length = packet_length + 4;  // 加上packet_length字段本身的4字节
         
-        // 生成随机padding（简化：使用0，实际应随机）
+        // 如果总长度不是block_size的倍数，增加padding
+        if total_length % block_size != 0 {
+            let remainder = total_length % block_size;
+            padding_length += (block_size - remainder) as u8;
+        }
+        
+        // 重新计算packet_length
+        let packet_length = (1 + payload_length + padding_length as usize) as u32;
+        
+        // 生成随机padding（简化：使用0）
         let padding = vec![0u8; padding_length as usize];
         
         Self {
-            packet_length: packet_length as u32,
+            packet_length,
             padding_length,
             payload,
             padding,