From e59ac86ea96da5bd3b730af5b95c85acef45d74b Mon Sep 17 00:00:00 2001
From: Simon Tatham <anakin@pobox.com>
Date: Wed, 5 Aug 2015 18:44:37 +0100
Subject: [PATCH] New 'contrib' script to sort out email-corrupted packet logs.

If a PuTTY SSH packet log has gone through line-wrapping at 72
columns, destroying the long lines of the packet hex dumps, then this
script will reconstitute it as best it can, by reconstructing the
ASCII section at the end of the dump from the (hopefully) undamaged
hex part, and using that to spot wrapped lines and remove the
subsequent debris.
---
 contrib/logrewrap.pl | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100755 contrib/logrewrap.pl

diff --git a/contrib/logrewrap.pl b/contrib/logrewrap.pl
new file mode 100755
index 00000000..ca2716f8
--- /dev/null
+++ b/contrib/logrewrap.pl
@@ -0,0 +1,44 @@
+#!/usr/bin/perl
+
+# Process a PuTTY SSH packet log that has gone through inappropriate
+# line wrapping, and try to make it legible again.
+#
+# Motivation: people often include PuTTY packet logs in email
+# messages, and if they're not careful, the sending MUA 'helpfully'
+# wraps the lines at 72 characters, corrupting all the hex dumps into
+# total unreadability.
+#
+# But as long as it's only the ASCII part of the dump at the end of
+# the line that gets wrapped, and the hex part is untouched, this is a
+# mechanically recoverable kind of corruption, because the ASCII is
+# redundant and can be reconstructed from the hex. Better still, you
+# can spot lines in which this has happened (because the ASCII at the
+# end of the line is a truncated version of what we think it should
+# say), and use that as a cue to remove the following line.
+
+use strict;
+use warnings;
+
+while (<>) {
+    if (/^  ([0-9a-f]{8})  ((?:[0-9a-f]{2} ){0,15}(?:[0-9a-f]{2}))/) {
+        my $addr = $1;
+        my $hex = $2;
+        my $ascii = "";
+        for (my $i = 0; $i < length($2); $i += 3) {
+            my $byte = hex(substr($hex, $i, 2));
+            my $char = ($byte >= 32 && $byte < 127 ? chr($byte) : ".");
+            $ascii .= $char;
+        }
+        $hex = substr($hex . (" " x 48), 0, 47);
+        my $old_line = $_;
+        chomp($old_line);
+        my $new_line = "  $addr  $hex  $ascii";
+        if ($old_line ne $new_line and
+            $old_line eq substr($new_line, 0, length($old_line))) {
+            print "$new_line\n";
+            <>; # eat the subsequent wrapped line
+            next;
+        }
+    }
+    print $_;
+}