Fix my broken understanding of the role of the init-vector in the

encryption process.  Essential property of the init-vector in CFB
encryption is that no two messages encrypted with the same key should
also use the same init-vector.  New design will read files encrypted
with previous scheme, but writes them using the current time as the
init-vector, and writes the init-vector into the file as part of the
header.

diff --git a/v7/src/runtime/blowfish.scm b/v7/src/runtime/blowfish.scm
index a6f394723ea9fb18e75fb47756196ca3f0a87b21..c211df3a227bc5adf869297eecf6651785b64d6c 100644 (file)
--- a/v7/src/runtime/blowfish.scm
+++ b/v7/src/runtime/blowfish.scm
@@ -1,6 +1,6 @@
 #| -*-Scheme-*-
 
-$Id: blowfish.scm,v 1.7 1999/05/18 17:11:58 cph Exp $
+$Id: blowfish.scm,v 1.8 1999/08/09 03:24:27 cph Exp $
 
 Copyright (c) 1997, 1999 Massachusetts Institute of Technology
 
@@ -104,11 +104,10 @@ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
                            0
                            encrypt?))
 
-(define (blowfish-encrypt-port input output key-string encrypt?)
+(define (blowfish-encrypt-port input output key-string init-vector encrypt?)
   ;; Assumes that INPUT is in blocking mode.
   (let ((key (blowfish-set-key (md5 key-string)))
-       (buffer (make-string 4096))
-       (init-vector (make-string 8 #\NUL)))
+       (buffer (make-string 4096)))
     (let loop ((m 0))
       (let ((n (input-port/read-string! input buffer)))
        (if (not (fix:= 0 n))
@@ -120,21 +119,41 @@ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
              (loop (fix:and #x7 (fix:+ m n)))))))))
 
 (define (write-blowfish-file-header port)
-  (write-string blowfish-file-header port)
-  (newline port))
+  (write-string blowfish-file-header-v2 port)
+  (newline port)
+  (let ((init-vector (compute-blowfish-cfb-init-vector)))
+    (write-string init-vector port)
+    init-vector))
 
 (define (read-blowfish-file-header port)
-  (if (not (string=? (read-line port) blowfish-file-header))
-      (error:bad-range-argument port 'READ-BLOWFISH-FILE-HEADER)))
+  (let ((line (read-line port)))
+    (cond ((string=? blowfish-file-header-v1 line)
+          (make-string 8 #\NUL))
+         ((string=? blowfish-file-header-v2 line)
+          (let ((init-vector (make-string 8)))
+            (if (not (= 8 (read-string! init-vector 0 8 port)))
+                (error "Short read while getting init-vector:" port))
+            init-vector))
+         (else
+          (error:bad-range-argument port 'READ-BLOWFISH-FILE-HEADER)))))
 
 (define (blowfish-file? pathname)
   (let ((line (call-with-binary-input-file pathname read-line)))
     (and (not (eof-object? line))
-        (string=? line blowfish-file-header))))
+        (or (string=? line blowfish-file-header-v1)
+            (string=? line blowfish-file-header-v2)))))
 
-(define blowfish-file-header
-  "Blowfish, 16 rounds")
+(define blowfish-file-header-v1 "Blowfish, 16 rounds")
+(define blowfish-file-header-v2 "Blowfish, 16 rounds, version 2")
 
+(define (compute-blowfish-cfb-init-vector)
+  (let ((iv (make-string 8)))
+    (do ((i 0 (fix:+ i 1))
+        (t (get-universal-time) (quotient t #x100)))
+       ((fix:= 8 i))
+      (vector-8b-set! iv i (remainder t #x100)))
+    iv))
+\f
 (define (md5-file filename)
   (call-with-binary-input-file filename
     (lambda (port)