Use Improved Key Reuse Procedure

encrypt.c

@@ -199,13 +199,21 @@ void make_encryptor(struct encryptor *tpl, struct encryptor *enc, uint8_t method
 		} else {
 			assert(!key);
 			assert(tpl->key);
-			enc->key = tpl->key;
-			enc->rc4_en = (struct rc4_state *)malloc(sizeof(struct rc4_state));
-			enc->rc4_de = (struct rc4_state *)malloc(sizeof(struct rc4_state));
+
+			if (!tpl->rc4_en) {
+			    // initialize rc4 keystream
+			    tpl->rc4_en = malloc(sizeof(*tpl->rc4_en));
+			    if (!tpl->rc4_en)
+				FATAL("malloc() failed!");
+			    rc4_init(tpl->rc4_en, tpl->key, MD5_LEN);
+			}
+			enc->rc4_en = malloc(sizeof(*enc->rc4_en));
+			enc->rc4_de = malloc(sizeof(*enc->rc4_de));
 			if (!(enc->rc4_en && enc->rc4_de))
 				FATAL("malloc() failed!");
-			rc4_init(enc->rc4_en, enc->key, MD5_LEN);
-			rc4_init(enc->rc4_de, enc->key, MD5_LEN);
+			// Copy the initial rc4 key stream.
+			*enc->rc4_en = *tpl->rc4_en;
+			*enc->rc4_de = *tpl->rc4_en;
 		}
 	}
 }
@@ -215,6 +223,7 @@ void destroy_encryptor(struct encryptor *enc)
 	if (enc->rc4_en) {
 		free(enc->rc4_en);
 		free(enc->rc4_de);
+		enc->rc4_en = NULL;
+		enc->rc4_de = NULL;
 	}
-
 }

rc4.c

@@ -36,6 +36,7 @@
  *
  * $FreeBSD: src/sys/crypto/rc4/rc4.c,v 1.2.2.1 2000/04/18 04:48:31 archie Exp $
  */
+#include <string.h>
 #include <stdint.h>
 #include "rc4.h"
 

server.c

@@ -544,9 +544,10 @@ int main(int argc, char *argv[])
 			    else if (!strcmp("shadow", optarg))
 			    	crypt_method = METHOD_SHADOWCRYPT;
 			    break;
+			case 'h':
 			default:
 				fprintf(stderr, USAGE, newargv[0]);
-				abort();
+				exit(1);
 		}
 	}
 

server.h

@@ -37,7 +37,8 @@
                         "  -p : Override the listening port\n"\
                         "  -k : Override the listening password\n"\
                         "  -f : Override the pidfile path\n"\
-                        "  -m : Override the encryption method\n\n"
+                        "  -m : Override the encryption method\n"\
+                        "  -h : Print this message\n\n"
 #define PROCESS_TITLE "shadowsocks on port:%d"
 #define PROCESS_TITLE_LENGTH 26
 #define ADDRTYPE_IPV4 1