svn commit: r318790 - head/usr.sbin/bootparamd/bootparamd

[Alan Somers]

Author: asomers
Date: Wed May 24 16:30:38 2017
New Revision: 318790
URL: https://svnweb.freebsd.org/changeset/base/318790

Log:
  Fix a buffer overflow in bootparamd(8)
  
  If /etc/bootparams contains a line with an excessively long pathname, and a
  client asks for that path, then bootparamd will overflow a buffer and crash
  while parsing that line.  This is not remotely exploitable since it requires
  a malformed /etc/bootparams file.
  
  Reported by:	Coverity
  CID:		1305954
  MFC after:	1 week
  Sponsored by:	Spectra Logic Corp

Modified:
  head/usr.sbin/bootparamd/bootparamd/bootparamd.c

Modified: head/usr.sbin/bootparamd/bootparamd/bootparamd.c
==============================================================================
--- head/usr.sbin/bootparamd/bootparamd/bootparamd.c	Wed May 24 14:36:51 2017	(r318789)
+++ head/usr.sbin/bootparamd/bootparamd/bootparamd.c	Wed May 24 16:30:38 2017	(r318790)
@@ -199,7 +199,10 @@ int blen;
 
   int ch, pch, fid_len, res = 0;
   int match = 0;
-  char info[MAX_FILEID + MAX_PATH_LEN+MAX_MACHINE_NAME + 3];
+#define INFOLEN 1343
+  _Static_assert(INFOLEN >= MAX_FILEID + MAX_PATH_LEN+MAX_MACHINE_NAME + 3,
+		  "INFOLEN isn't large enough");
+  char info[INFOLEN + 1];
 
   bpf = fopen(bootpfile, "r");
   if ( ! bpf )
@@ -251,8 +254,9 @@ int blen;
      info of the file */
 
   if (match) {
-    fid_len = strlen(fileid);
-    while ( ! res && (fscanf(bpf,"%s", info)) > 0) { /* read a string */
+#define AS_FORMAT(d)	"%" #d "s"
+#define REXPAND(d) AS_FORMAT(d)	/* Force another preprocessor expansion */
+    while ( ! res && (fscanf(bpf, REXPAND(INFOLEN), info)) > 0) {
       ch = getc(bpf);                                /* and a character */
       if ( *info != '#' ) {                          /* Comment ? */
 	if (! strncmp(info, fileid, fid_len) && *(info + fid_len) == '=') {