Fix broken compatibility tests for MD4 mode.

rdiff sig defaults (temporarily) back to MD4, but gains an option to control
this. In MD4, truncate the hash the same way that previous versions did.

Add a sig_magic parameter to rs_sig_begin and rs_sig_file to let callers
choose a version.

Add NEWS about md4 weakness.

1 files changed, 27 insertions, 7 deletions

diff --git a/librsync.h b/librsync.h
index e03ae3d..fd27d2a 100644
--- a/librsync.h
+++ b/librsync.h
@@ -2,7 +2,7 @@
  *
  * librsync -- library for network deltas
  * 
- * Copyright (C) 2000, 2001 by Martin Pool <mbp@sourcefrog.net>
+ * Copyright 2000, 2001, 2014 by Martin Pool <mbp@sourcefrog.net>
  * Copyright (C) 2003 by Donovan Baarda <abo@minkirri.apana.org.au> 
  * 
  * This program is free software; you can redistribute it and/or modify
@@ -71,6 +71,25 @@ typedef enum {
 
 
 
+                          /*
+                           | "The IETF already has more than enough
+                           | RFCs that codify the obvious, make
+                           | stupidity illegal, support truth,
+                           | justice, and the IETF way, and generally
+                           | demonstrate the author is a brilliant and
+                           | valuable Contributor to The Standards
+                           | Process."
+                           |     -- Vernon Schryver
+                           */
+
+
+typedef enum {
+    RS_DELTA_MAGIC          = 0x72730236,      /* r s \2 6 */
+    RS_MD4_SIG_MAGIC        = 0x72730136,      /* r s \1 6 */
+    RS_BLAKE2_SIG_MAGIC     = 0x72730137       /* r s \1 7 */
+} rs_magic_number;
+
+
 /**
  * \typedef rs_trace_fn_t
  * \brief Callback to write out log messages.
@@ -193,6 +212,8 @@ typedef struct rs_mdfour rs_mdfour_t;
  * buffers now
  * #define RS_MD4_LENGTH 16
  */
+extern const int RS_MD4_SUM_LENGTH, RS_BLAKE2_SUM_LENGTH;
+
 #define RS_MAX_STRONG_SUM_LENGTH 32
 
 typedef unsigned int rs_weak_sum_t;
@@ -281,10 +302,6 @@ struct rs_buffers_s {
  */
 typedef struct rs_buffers_s rs_buffers_t;
 
-/** Default length of strong signatures, in bytes.  The MD4 checksum
- * is truncated to this size. */
-#define RS_DEFAULT_STRONG_LEN 32
-
 /** Default block length, if not determined by any other factors. */
 #define RS_DEFAULT_BLOCK_LEN 2048
 
@@ -322,7 +339,8 @@ rs_result       rs_job_free(rs_job_t *);
 
 int             rs_accum_value(rs_job_t *, char *sum, size_t sum_len);
 
-rs_job_t *rs_sig_begin(size_t new_block_len, size_t strong_sum_len);
+rs_job_t *rs_sig_begin(size_t new_block_len, size_t strong_sum_len,
+		       rs_long_t sig_magic);
 
 rs_job_t *rs_delta_begin(rs_signature_t *);
 
@@ -370,7 +388,9 @@ extern int rs_inbuflen, rs_outbuflen;
 void rs_mdfour_file(FILE *in_file, char *result);
 
 rs_result rs_sig_file(FILE *old_file, FILE *sig_file,
-                      size_t block_len, size_t strong_len, rs_stats_t *); 
+                      size_t block_len, size_t strong_len,
+		      rs_long_t sign_magic,
+		      rs_stats_t *); 
 
 rs_result rs_loadsig_file(FILE *, rs_signature_t **, rs_stats_t *);