Implement SSH Compression Phase 2: Integration

- Add compression_ctos/compression_stoc to EncryptionContext
- Default impl: CompressionContext::new(6)
- from_session_keys(): initialize compression fields
- enable_compression() method (based on KEX negotiation)
- server.rs: enable compression after NEWKEYS (if negotiated)

All 179 tests pass.

markbase-core/src/ssh_server/cipher.rs

@@ -3,6 +3,7 @@
 
 use super::crypto::SessionKeys;
 use super::sshbuf::SshBuf;
+use super::compression::CompressionContext; // Phase 2: SSH Compression
 use aes::Aes128; // 改为AES-128（协商算法是aes128-ctr）
 use aes_gcm::{
     aead::{Aead, KeyInit, Payload},
@@ -39,6 +40,8 @@ pub struct EncryptionContext {
     pub cipher_ctos: Option<Aes128Ctr>, // 客户端→服务器cipher实例（持久化，AES-CTR）
     pub cipher_stoc: Option<Aes128Ctr>, // 服务器→客户端cipher实例（持久化，AES-CTR）
     pub cipher_mode: CipherMode,        // Phase 1: 区分 AES-CTR 和 AES-GCM 模式
+    pub compression_ctos: CompressionContext, // Phase 2: 客户端→服务器压缩
+    pub compression_stoc: CompressionContext, // Phase 2: 服务器→客户端压缩
 }
 
 /// Phase 1: 加密模式选择（AES-CTR vs AES-GCM）
@@ -64,6 +67,8 @@ impl Default for EncryptionContext {
             cipher_ctos: None,
             cipher_stoc: None,
             cipher_mode: CipherMode::AesCtr, // 默认使用 AES-CTR（兼容性）
+            compression_ctos: CompressionContext::new(6), // Phase 2
+            compression_stoc: CompressionContext::new(6), // Phase 2
         }
     }
 }
@@ -113,6 +118,20 @@ impl EncryptionContext {
             cipher_ctos: Some(cipher_ctos), // 持久化cipher实例
             cipher_stoc: Some(cipher_stoc), // 持久化cipher实例
             cipher_mode: CipherMode::AesCtr, // 默认使用 AES-CTR（兼容性）
+            compression_ctos: CompressionContext::new(6), // Phase 2: 默认压缩级别6
+            compression_stoc: CompressionContext::new(6), // Phase 2: 默认压缩级别6
+        }
+    }
+    
+    /// Phase 2: 启用压缩（根据 KEX 协商结果）
+    pub fn enable_compression(&mut self, compression_ctos: &str, compression_stoc: &str) {
+        if compression_ctos == "zlib" {
+            info!("Enabling compression (client→server)");
+            self.compression_ctos.enable();
+        }
+        if compression_stoc == "zlib" {
+            info!("Enabling compression (server→client)");
+            self.compression_stoc.enable();
         }
     }