Bug#762508: fails to read from read-only filesystems; uses buggy read logic and error detection

[Sam Hocevar]

Package: chntpw
Version: 1.0-1
Severity: important
Tags: upstream patch

   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. The attached 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.

Cheers,
-- 
Sam.

-- System Information:
Debian Release: jessie/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (500, 'testing'), (500, 'stable'), (500, 
'oldstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 3.16-trunk-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages chntpw depends on:
ii  libc6        2.19-11
ii  libgcrypt11  1.5.4-3

chntpw recommends no packages.

chntpw suggests no packages.

-- no debconf information

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);
   }