Description: Fix reading files in read-only filesystems

 chntpw fails to read files from read-only filesystems, despite having some
 logic to handle this:

# chntpw -e /c/Windows/System32/config/SOFTWARE
chntpw version 1.00 140201, (c) Petter N Hagen
openHive(/c/Windows/System32/config/SOFTWARE) failed: Read-only file system, trying read-only
openHive(): read error: : Read-only file system
chntpw: Unable to open/read a hive, exiting..
#

   This is due to using errno as an error checking mechanism; it should only be
   used when one knows a function has failed. This patch fixes this problem. It
   also adds support for the non-fatal EINTR error, and fixes yet another bug
   where the last read size is used in a check instead of the whole file size.

Author: Sam Hocevar <sam@hocevar.net>
Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=762508

Index: chntpw-1.0/ntreg.c
===================================================================
--- chntpw-1.0.orig/ntreg.c
+++ chntpw-1.0/ntreg.c
@@ -4241,9 +4241,9 @@ struct hive *openHive(char *filename, in
   do {  /* On some platforms read may not block, and read in chunks. handle that */
     r = read(hdesc->filedesc, hdesc->buffer + rt, hdesc->size - rt);
     rt += r;
-  } while ( !errno && (rt < hdesc->size) );
+  } while ( (r > 0 || (r < 0 && errno == EINTR)) && (rt < hdesc->size) );
 
-  if (errno) { 
+  if (r < 0) {
     perror("openHive(): read error: ");
     closeHive(hdesc);
     return(NULL);
@@ -4255,10 +4255,10 @@ struct hive *openHive(char *filename, in
     return(NULL);
   }
 
-  if (r < sizeof (*hdesc)) {
+  if (rt < sizeof (*hdesc)) {
     fprintf(stderr,
 	    "file is too small; got %d bytes while expecting %d or more\n",
-	    r, sizeof (*hdesc));
+	    rt, sizeof (*hdesc));
     closeHive(hdesc);
     return(NULL);
   }