[Opensrf-commits] r1038 - trunk/src/srfsh

[svn at svn.open-ils.org]

Author: erickson
Date: 2007-07-16 09:03:48 -0400 (Mon, 16 Jul 2007)
New Revision: 1038

Modified:
   trunk/src/srfsh/srfsh.c
Log:
Patch from Scott McKellar to repair srfsh buffer overflow:

The potential overflow occurs in handle_introspection(), which in the
existing code uses sprintf() to insert some user-supplied input into a
fixed length buffer, without checking the length of the user-supplied
input.

There's always more than one way to fix this sort of thing.  For
example I could have formatted into a growing_buffer.  Instead, I
chose to calculate the necessary buffer size and then declare a
variable-length buffer.  That way I avoid two mallocs and two frees.

I tested this change by inserting some temporary printfs to capture
the commands being sent to parse_request().  The outputs before and
after the change were identical.

There's at least one more such potential overflow that I haven't
addressed yet.  It's near the top of handle_login(), where we
use sprintf() to insert a username into a fixed length buffer.
There may be others that I haven't noticed yet.

Scott McKellar
http://home.swbell.net/mck9/ct/



Modified: trunk/src/srfsh/srfsh.c
===================================================================
--- trunk/src/srfsh/srfsh.c	2007-07-16 03:19:33 UTC (rev 1037)
+++ trunk/src/srfsh/srfsh.c	2007-07-16 13:03:48 UTC (rev 1038)
@@ -324,25 +324,30 @@
 
 static int handle_introspect(char* words[]) {
 
-	if(words[1] && words[2]) {
-		fprintf(stderr, "--> %s\n", words[1]);
-		char buf[256];
-		memset(buf,0,256);
-		sprintf( buf, "request %s opensrf.system.method %s", words[1], words[2] );
+	if( ! words[1] )
+		return 0;
+
+	fprintf(stderr, "--> %s\n", words[1]);
+
+	// Build a command in a suitably-sized
+	// buffer and then parse it
+	
+	size_t len;
+	if( words[2] ) {
+		static const char text[] = "request %s opensrf.system.method %s";
+		len = sizeof( text ) + strlen( words[1] ) + strlen( words[2] );
+		char buf[len];
+		sprintf( buf, text, words[1], words[2] );
 		return parse_request( buf );
 
 	} else {
-	
-		if(words[1]) {
-			fprintf(stderr, "--> %s\n", words[1]);
-			char buf[256];
-			memset(buf,0,256);
-			sprintf( buf, "request %s opensrf.system.method.all", words[1] );
-			return parse_request( buf );
-		}
+		static const char text[] = "request %s opensrf.system.method.all";
+		len = sizeof( text ) + strlen( words[1] );
+		char buf[len];
+		sprintf( buf, text, words[1] );
+		return parse_request( buf );
+
 	}
-
-	return 0;
 }